Soccer-Specific Warm-Up and Lower Extremity Injury Rates in Collegiate Male Soccer Players

Context:

A number of comprehensive injury-prevention programs have demonstrated injury risk-reduction effects but have had limited adoption across athletic settings. This may be due to program noncompliance, minimal exercise supervision, lack of exercise progression, and sport specificity. A soccer-specific program described as the F-MARC 11+ was developed by an expert group in association with the Federation Internationale de Football Association (FIFA) Medical Assessment and Research Centre (F-MARC) to require minimal equipment and implementation as part of regular soccer training. The F-MARC 11+ has been shown to reduce injury risk in youth female soccer players but has not been evaluated in an American male collegiate population.

Objective:

To investigate the effects of a soccer-specific warm-up program (F-MARC 11+) on lower extremity injury incidence in male collegiate soccer players.

Design:

Cohort study.

Setting:

One American collegiate soccer team followed for 2 seasons.

Patients or Other Participants:

Forty-one male collegiate athletes aged 18–25 years.

Intervention(s):

The F-MARC 11+ program is a comprehensive warm-up program targeting muscular strength, body kinesthetic awareness, and neuromuscular control during static and dynamic movements. Training sessions and program progression were monitored by a certified athletic trainer.

Main Outcome Measure(s):

Lower extremity injury risk and time lost to lower extremity injury.

Results:

The injury rate in the referent season was 8.1 injuries per 1000 exposures with 291 days lost and 2.2 injuries per 1000 exposures and 52 days lost in the intervention season. The intervention season had reductions in the relative risk (RR) of lower extremity injury of 72% (RR = 0.28, 95% confidence interval = 0.09, 0.85) and time lost to lower extremity injury (P < .01).

Conclusions:

This F-MARC 11+ program reduced overall risk and severity of lower extremity injury compared with controls in collegiate-aged male soccer athletes.Key Words: injury prevention, sport injuries, athletic trainers

Key Points

• The F-MARC 11+ reduced the risk of lower extremity injuries in youth female soccer players, but limited evidence for its effectiveness exists in males and at the collegiate level.
• A traditional warm-up did not prevent injury as effectively as the F-MARC 11+ program, despite taking the same amount of time.
• When supervised by an athletic trainer, the F-MARC 11+ prevented injuries in collegiate male soccer players.
• An athletic trainer administered intervention, reduced injury risk, and improved program compliance, progression, and execution.

Soccer is among the most popular sports in the world, boasting more than 265 million¹ youth and amateur players and more than 37 000 American collegiate players.² Soccer participation has continued to increase over the past decade worldwide and especially in the United States National Collegiate Athletic Association (NCAA).² Lower extremity injury rates for male NCAA soccer athletes have remained relativity stable over the past decade (practice versus game: 8 versus 12.18 per 1000 exposures).² Junge and Dvorak,³ in a systematic review of soccer injuries in international male players, reported 10 to 35 injuries per 1000 hours of match play and 2 to 7 per 1000 hours of training in international male soccer players. In cohorts of international, elite-level soccer athletes, the injury rate was high (1.3 injuries per player per season); most injuries affected the lower extremity (87%) and resulted from noncontact mechanisms (58%).⁴ The most common injury in male collegiate soccer players was ankle sprains (3.19 per 1000 exposures), followed by thigh muscle strains and knee sprains at 2.28 and 2.07 per 1000 exposures, respectively.² These findings are consistent with reports of international-level soccer athletes.⁴ These lower extremity injuries have substantial short-term consequences, such as loss of participation, and the potential for long-term consequences, such as decreased physical activity⁵ and increased risk of osteoarthritis.^5–10 Nearly 20% of all soccer injuries were severe, requiring greater than 10 days of time lost from activity.² Knee ligament ruptures and leg fractures accounted for 35% of these injuries, many of which required surgical intervention and prolonged rehabilitative care; these patients also had a greatly increased risk of a secondary injury when they returned to soccer competition.^2,11The high injury rate in soccer players has persisted despite scientific advances in injury etiology,^12–17 screening techniques, and the identification of athletes who may be at greater risk.^18–25 Although injury-prevention programs have successfully decreased lower extremity injuries such as ankle sprains,^24,26–29 anterior cruciate ligament (ACL) injuries,^18,30,31 and hamstrings strains,^{20,24,29,32–34} they have not yet been widely adopted,³⁵ limiting their potential effects in soccer athletes.³⁶Although numerous training programs have been designed to prevent injury,^{3,24,26,29,31,32,37–55} few incorporate sport-specific components.^{37,38,41,42,56,57} Many of these programs have shown promising results in decreasing the risk of injury.^{18,37,38,41,58} However, extensive time, expert personnel, and special equipment are needed for these programs to be effective. To make injury-prevention programs as widely accessible as possible, the F-MARC 11+ program was developed by the Federation International de Football Association (FIFA) Medical Assessment and Research Center (F-MARC).⁵⁹ This program can be completed in a short time frame, takes minimal training to implement, and requires only a soccer ball, making it an attractive alternative for sport coaches, strength and conditioning professionals, and rehabilitation specialists already working with limited time and budgets. Thus far, 4 studies^37,38,41,60 have reported on the use of a version of the F-MARC 11+ program in adolescent males and females, with injury reductions ranging from 21% to 71%. In Norwegian handball players, similar training programs have produced a 49% reduction in injury risk⁴⁰ and 94% reduction in ACL injury risk.³⁹To our knowledge, the F-MARC 11+ has yet to be investigated for effectiveness in injury risk reduction in an American male collegiate soccer population. Therefore, our aim was to examine the effect of a sport-specific program implemented with athletic trainer supervision to track compliance, injury occurrence, and program performance quality. We hypothesized that the comprehensive, exercise-based soccer warm-up program (the F-MARC 11+) would be more effective than the traditional dynamic warm-up in preventing lower extremity injuries in male NCAA Division III collegiate soccer athletes.     

Customized Noise-Stimulation Intensity for Bipedal Stability and Unipedal Balance Deficits Associated With Functional Ankle Instability

Context:

Stochastic resonance stimulation (SRS) administered at an optimal intensity could maximize the effects of treatment on balance.

Objective:

To determine if a customized optimal SRS intensity is better than a traditional SRS protocol (applying the same percentage sensory threshold intensity for all participants) for improving double- and single-legged balance in participants with or without functional ankle instability (FAI).

Design:

Case-control study with an embedded crossover design.

Setting:

Laboratory.

Patients or Other Participants:

Twelve healthy participants (6 men, 6 women; age = 22 ± 2 years, height = 170 ± 7 cm, mass = 64 ± 10 kg) and 12 participants (6 men, 6 women; age = 23 ± 3 years, height = 174 ± 8 cm, mass = 69 ± 10 kg) with FAI.

Intervention(s):

The SRS optimal intensity level was determined by finding the intensity from 4 experimental intensities at the percentage sensory threshold (25% [SRS₂₅], 50% [SRS₅₀], 75% [SRS₇₅], 90% [SRS₉₀]) that produced the greatest improvement in resultant center-of-pressure velocity (R-COPV) over a control condition (SRS₀) during double-legged balance. We examined double- and single-legged balance tests, comparing optimal SRS (SRS_opt1) and SRS₀ using a battery of center-of-pressure measures in the frontal and sagittal planes.

Main Outcome Measure(s):

Anterior-posterior (A-P) and medial-lateral (M-L) center-of-pressure velocity (COPV) and center-of-pressure excursion (COPE), R-COPV, and 95th percentile center-of-pressure area ellipse (COPA-95).

Results:

Data were organized into bins that represented optimal (SRS_opt1), second (SRS_opt2), third (SRS_opt3), and fourth (SRS_opt4) improvement over SRS₀. The SRS_opt1 enhanced R-COPV (P ≤ .05) over SRS₀ and other SRS conditions (SRS₀ = 0.94 ± 0.32 cm/s, SRS_opt1 = 0.80 ± 0.19 cm/s, SRS_opt2 = 0.88 ± 0.24 cm/s, SRS_opt3 = 0.94 ± 0.25 cm/s, SRS_opt4 = 1.00 ± 0.28 cm/s). However, SRS did not improve R-COPV over SRS₀ when data were categorized by sensory threshold. Furthermore, SRS_opt1 improved double-legged balance over SRS₀ from 11% to 25% in all participants for the center-of-pressure frontal- and sagittal-plane assessments (P ≤ .05). The SRS_opt1 also improved single-legged balance over SRS₀ from 10% to 17% in participants with FAI for the center-of-pressure frontal- and sagittal-plane assessments (P ≤ .05). The SRS_opt1 did not improve single-legged balance in participants with stable ankles.

Conclusions:

The SRS_opt1 improved double-legged balance and transfers to enhancing single-legged balance deficits associated with FAI.Key Words: chronic ankle instability, noise, postural stability, therapy

Key Points

• Stochastic resonance stimulation can be considered an alternative treatment for balance impairments.
• Stochastic resonance stimulation may be an effective treatment in the early stages of rehabilitation to facilitate immediate balance improvements that may help patients transition to complex postural stability exercises or functional movements.
• A double-legged balance-optimization protocol may be an efficient method to determine a customized optimal stochastic resonance stimulation intensity that will transfer to improving single-legged balance for functional ankle instability.

Functional ankle instability (FAI) is a residual symptom of ankle sprains that often causes the sensation of “giving way” at the ankle and recurrent ankle sprains.¹ In addition, sensorimotor deficits associated with FAI are present as balance impairments.² Postural instabilities are important to identify because poor balance is a predisposing factor of ankle sprain injury.^3–5 Given that balance improvements associated with rehabilitation often take 6 weeks to occur,^6,7 a therapy, such as stochastic resonance stimulation (SRS), that facilitates balance improvements immediately⁸ or more quickly than rehabilitation alone^9,10 would be beneficial for individuals with FAI. Stochastic resonance stimulation is a therapy that introduces subsensory mechanical noise through the skin to enhance the ability of mechanoreceptors to detect and transmit weak signals related to balance.^11–13Natural noise created in the body can promote signal detection by amplifying weak sensory signals.^14,15 This natural noise occurs from external stimuli, physiologic processes, and biomechanics.^14,15 However, this internally generated noise may not be at a high enough level in some individuals to improve signal detection.^14,15 Healthy and injured individuals may benefit from SRS therapy when the level of naturally occurring noise is too low to facilitate signal detection.^14,15 Most evidence has indicated that individuals with and without sensorimotor impairments react similarly to SRS,^9,10,16–20 suggesting that the level of natural noise in the body is low enough for SRS to have positive treatment effects.Interestingly, however, Priplata et al¹⁸ reported that elderly participants had a better response to SRS than young healthy participants because the former used SRS to facilitate sensory signal detection to reduce sway. In addition, SRS improved balance in the elderly participants to within the normal range for young, healthy participants.¹⁸ Sensorimotor impairments are associated with age, and the naturally occurring noise in the elderly participants might not have contributed to signal detection.¹⁸ Thus, SRS corrected these sensorimotor deficits to facilitate balance improvements.¹⁸ Given the findings in the elderly participants,¹⁸ we postulate that the balance response to SRS might be better in individuals with FAI than in healthy individuals because FAI also is associated with sensorimotor deficits. Currently, no evidence exists to demonstrate that SRS produces better balance for FAI than stable ankles. Demonstrating that SRS improves balance more in FAI than stable ankles lends credence to the notion that this therapy enhances sensorimotor function.Recent evidence²¹ has indicated that the sensorimotor dysfunction with FAI may be due to reflex depressions, which can cause excessive sway with single-legged balance. These poor postural reflexes can result from an inability to integrate afferent input and efferent output.²² That is, diminished sensation from the foot and ankle may not detect signals related to postural control, leading to inappropriate muscle contractions that maintain stability. The inability to sense signals to generate adequate postural reflexes suggests that the naturally occurring internal noise is at a level too low to facilitate signal detection. To correct this sensorimotor impairment, SRS can serve as a pedestal to predispose mechanoreceptors to fire in the presence of real sensory signals, especially signals that otherwise would be undetectable.^11–13The traditional method for examining the effects of SRS on balance improvements is to apply the same subsensory intensity to all participants within a research study.^16–20 Subsensory intensities from 25% to 90% have enhanced balance in patients who are healthy, have diabetes, or have had a stroke.^16–20 Researchers¹⁷ also have presented preliminary data indicating that 75% of sensory threshold could be the optimal SRS intensity to affect the degree of balance improvements. This finding was confirmed in a second experiment¹⁷ when this specific SRS intensity was applied to all participants to optimize balance enhancements.Two research groups recently have proposed customizing the intensity of SRS applied to an individual to maximize treatment effects in lieu of applying the same intensity to all participants.^8,23 The rationale for this customized design was deduced from the early work of Collins et al,²⁴ who demonstrated that performance increased to a peak with increasing levels of SRS intensity and then decreased; however, the SRS intensity associated with this optimal intensity was slightly different for participants. In other words, the levels of SRS intensity for improving sensorimotor function must be fine tuned because subsensory intensities that are too low may not improve balance and those that are too high can diminish function.^{8,11,17,23,24} Furthermore, a customized SRS intensity is proposed for minimizing random error in datasets, potentially decreasing washout effects in a group analysis.⁸ Specifically related to FAI, researchers⁸ using 1 of 2 input SRS intensities have demonstrated that 92% of participants with FAI improved their single-legged balance with at least 1 input intensity, whereas 55% of them had impaired balance at the other input intensity. This finding suggests that using 1 intensity for all participants may have masked the treatment effects of SRS if the intensity that impaired balance was used for analysis.⁸ More recently, Mulavara et al²³ found that customizing the SRS intensity applied to an individual was crucial for maximizing balance improvements in healthy participants. These researchers defined an optimal intensity as the stimulus amplitude emitted from the SRS device that best improved balance over a control (no-SRS) condition.²³ By determining this customized optimal intensity for each individual, we speculate that treatment effects associated with SRS will increase compared with the same intensity for all participants.Double-legged balance tests are recommended for determining the treatment effects of SRS on stability.^16–20,23 These bipedal assessments allow individuals to maximize their stability with a wide base of support, providing a reliable means of determining the optimal SRS intensity. This recommended double-legged SRS protocol has not been tested in participants with FAI. Clinically, this protocol may be important to examine with FAI because balance can be assessed quickly when optimizing SRS intensity. Single-legged balance protocols may not be efficient for optimizing SRS intensity because of the number of unsuccessful trials associated with FAI. However, most researchers do not use single-legged balance as a criterion standard for assessing balance deficits associated with FAI² or quantifying treatment effects of SRS on FAI.^8–10 Therefore, for clinical applications, we propose using a double-legged balance protocol to quickly and efficiently optimize SRS intensity and then using this intensity to enhance single-legged balance. This optimization protocol may be more clinically relevant if the intensity for enhancing double-legged balance transfers to improving single-legged balance.Along these lines of clinical effectiveness, we believe that clinicians need to focus on 1 balance outcome measure when optimizing SRS intensity to improve stability. Common balance outcome measures that have improved with SRS over control conditions include sway velocity, excursion, and area.^16–20 Specifically related to FAI, resultant center-of-pressure velocity (COPV) has been used to assess the immediate effects of SRS on single-legged balance.⁸ Other balance measures also have been examined with SRS in participants with FAI, but all use center-of-pressure excursion (COPE) data points to compute the outcome measures (eg, COPV is computed by dividing excursion by time).^9,10 For clinical applicability, we have taken a minimalist approach in our study by selecting resultant COPV as our main outcome measure for the optimization protocol because it has detected balance improvements associated with SRS in participants with FAI.⁸Therefore, the initial purpose of our study was to determine if a customized optimal SRS intensity was better than a traditional SRS protocol (applying the same percentage sensory threshold intensity for all participants) for improving double- and single-legged balance in participants with and without FAI. Using a customized optimal SRS intensity, we wanted to determine (1) if individuals with FAI and individuals with stable ankles responded at different rates, (2) if double-legged balance (as measured by additional center-of-pressure measures) improved more with the optimal intensity than a control condition, and (3) if the optimal intensity for double-legged balance could transfer to improving single-legged balance over a control condition. Our hypotheses included the following: (1) The customized optimal SRS intensity protocol would improve double-legged balance better than the traditional protocol; (2) the treatment response to optimal SRS would be greater in individuals with FAI than in individuals with stable ankles; (3) the optimal intensity would improve double-legged balance more than a control condition; and (4) the optimal intensity would transfer to improving single-legged balance more than a control condition. The results of our study may be clinically relevant because a customized optimal SRS intensity level that maximally improves balance may enhance rehabilitation outcome measures and lead to greater ankle stability.     

Differences in Lateral Drop Jumps From an Unknown Height Among Individuals With Functional Ankle Instability

Context:

Functional ankle instability (FAI) is a debilitating condition that has been reported to occur after 20% to 50% of all ankle sprains. Landing from a jump is one common mechanism of ankle injury, yet few researchers have explored the role of visual cues and anticipatory muscle contractions, which may influence ankle stability, in lateral jumping maneuvers.

Objective:

To examine muscle-activation strategies between FAI and stable ankles under a lateral load and to evaluate the differences in muscle activation in participants with FAI and participants with stable ankles when they were unable to anticipate the onset of lateral loads during eyes-open versus eyes-closed conditions.

Design:

Case-control study.

Setting:

Controlled laboratory setting.

Patients or Other Participants:

A total of 40 people participated: 20 with FAI and 20 healthy, uninjured, sex- and age-matched persons (control group).

Intervention(s):

Participants performed a 2-legged lateral jump off a platform onto a force plate set to heights of 35 cm or 50 cm and then immediately jumped for maximal height. They performed jumps in 2 conditions (eyes open, eyes closed) and were unaware of the jump height when their eyes were closed.

Main Outcome Measure(s):

Amplitude normalized electromyographic (EMG) area (%), peak (%), and time to peak in the tibialis anterior (TA), peroneus longus (PL), and lateral gastrocnemius (LG) muscles were measured.

Results:

Regardless of the eyes-open or eyes-closed condition, participants with FAI had less preparatory TA (t₁₅₈ = 2.22, P = .03) and PL (t₁₅₈ = 2.09, P = .04) EMG area and TA (t₁₅₈ = 2.45, P = .02) and PL (t₁₅₈ = 2.17, P = .03) peak EMG than control-group participants.

Conclusions:

By removing visual cues, unanticipated lateral joint loads occurred simultaneously with decreased muscle activity, which may reduce dynamic restraint capabilities in persons with FAI. Regardless of visual impairment and jump height, participants with FAI exhibited PL and TA inhibition, which may limit talonavicular stability and intensify lateral joint surface compression and pain.Key Words: electromyography, peroneus longus, tibialis anterior, neuromuscular control

Key Points

• Participants with functional ankle instability (FAI) had less preparatory electromyographic (EMG) area and less peak EMG amplitude in the peroneus longus and tibialis anterior compared to control participants.
• When landing from a lateral jump, participants with FAI exhibited muscle-activation strategies that were different from those of participants with stable ankles.
• Participants with FAI did not appropriately increase dynamic stability relative to the functional demands.
• Decreased activation in the peroneus longus and tibialis anterior before landing from unknown heights has important clinical applications because it may place persons with FAI at risk for further injury during athletic activities.

Ankle injuries are one of the most common injuries in athletes, and evidence suggests that the cause of injury may not always involve mechanical laxity but rather complex abnormalities within the sensorimotor system.^1–3Approximately 50% of the population with lateral sprains experiences functional ankle instability (FAI), which is a frequent and serious pathologic sequela.^4,5 These persons often present with sensations of the ankle “giving way” and sudden “rollover” events, which are characteristic of FAI.^1,3 Several factors contributing to FAI have been proposed to result from the failure of the dynamic restraint mechanism, such as deficits in kinesthetic awareness and balance, weakness of the musculature, mechanical laxity, and many other influences.^1,3,6–10 However, limited data are available to establish whether persons with FAI attempt to negotiate sensory conflicts with different dynamic restraint strategies when confronted with sudden lateral ankle loading during functional activities.¹¹Sudden bouts of instability to the ankle can occur during many functional tasks, including walking, running, cutting, and jumping.¹² During athletic competition, the combination of high-speed, ballistic-like movements and rapid joint loading requires people to use feed-forward motor control to execute preprogrammed movement strategies.¹³ Based on past experiences, the central nervous system develops and executes the preactivation strategies to anticipate the expected joint loads associated with specific maneuvers.^14,15 Preactivation of muscles is an important contributor to joint stability because properly tensioned muscles optimize joint stiffness for dynamic restraint and functional performance capabilities.^16–19 If somatosensory information is misinterpreted or incompatible with physical events, optimal stiffness may not be achieved, and both functional performance and joint stability may be compromised.Much of the previous research on muscle activation has focused on various types of forward or sagittal-plane movements (ie, forward gait, forward hopping, running).^7–11,13 In a study on gait, Caulfield and Garrett⁷ reported increased electromyographic (EMG) amplitude in the peroneus longus (PL) after heel strike among persons with FAI. In addition, decreased PL EMG amplitude has been observed before landing from a jump.^7,8 These differences in EMG activation of the PL may reflect compensatory strategies to dynamically protect the ankle joint from excessive inversion. In walking and forward-landing research, investigators^8,9,11,13 have provided some evidence of neuromuscular disparities in persons with FAI during activity. However, lateral maneuvers are also important functional tasks involved in the pathomechanics of injury and have not been measured adequately.Given that most athletic maneuvers are executed in multiplanar directions and that a combination of inversion and plantar flexion is a common contributor to ankle injury, researchers need to examine movements within other functional planes, such as lateral jumping.^3,20 Docherty et al²⁰ suggested that measurable functional performance deficits are present during lateral hopping in participants with instability, but no deficits are present when they are executing sagittal-plane functional movements. In earlier research, Delahunt et al¹¹ also demonstrated that participants with FAI have less eversion from 45 milliseconds before contact to 95 milliseconds after contact and have increased EMG activity in the tibialis anterior (TA) and soleus muscles during a lateral hop. These data show the differences of anticipatory muscle activation and joint positioning in preparation for joint loading and illustrate that participants with FAI may present with incorrect neuromuscular control strategies that could predispose them to future episodes of instability.In addition, increased EMG activity in the surrounding musculature has been seen with an increase in jump height.^15,21 Consequently, when a person knows there is a large drop-jump height, the amount of muscle stiffness increases to account for the increase in anticipated forces that will be placed on the ankle.^15,21 However, during physical activity, sensory conflict may occur and disrupt preparatory motor planning. If visual clues are lacking or conflicting, other input, such as proprioceptive and vestibular information, is necessary to modulate preactivation of muscles and navigate safe landings.¹⁵Muscle-activation strategies may be altered in patients with FAI and may influence dynamic restraint capabilities. It is not known whether persons with FAI execute normal preactivation strategies during lateral drop jumps or how they respond to conditions where they cannot anticipate the jump height. Potential differences in the preactivation of muscles in persons with FAI versus persons with stable ankles may provide insight about compensatory movement strategies underlying chronic sensations of the ankle giving way and instability. To our knowledge, no researchers have observed drop jumps with lateral loading of the ankle or have examined the effects of anticipatory muscle preactivation in FAI participants under unknown landing conditions. Therefore, the purpose of our research was 2-fold: (1) to examine muscle-activation strategies between persons with FAI and those with stable ankles under a lateral load and (2) to evaluate the differences in muscle activation in participants with FAI and participants with stable ankles when they were unable to anticipate the onset of lateral loads during eyes-open versus eyes-closed conditions.     

Lower Extremity Biomechanics in Athletes With Ankle Instability After a 6-Week Integrated Training Program

Context:

Plyometric exercise has been recommended to prevent lower limb injury, but its feasibility in and effects on those with functional ankle instability (FAI) are unclear.

Objective:

To investigate the effect of integrated plyometric and balance training in participants with FAI during a single-legged drop landing and single-legged standing position.

Design:

Randomized controlled clinical trial.

Setting:

University motion-analysis laboratory.

Patients or Other Participants:

Thirty athletes with FAI were divided into 3 groups: plyometric group (8 men, 2 women, age = 23.20 ± 2.82 years; 10 unstable ankles), plyometric-balance (integrated)–training group (8 men, 2 women, age = 23.80 ± 4.13 years; 10 unstable ankles), and control group (7 men, 3 women, age = 23.50 ± 3.00 years; 10 unstable ankles).

Intervention(s):

A 6-week plyometric-training program versus a 6-week integrated-training program.

Main Outcome Measure(s):

Postural sway during single-legged standing with eyes open and closed was measured before and after training. Kinematic data were recorded during medial and lateral single-legged drop landings after a 5-second single-legged stance.

Results:

Reduced postural sway in the medial-lateral direction and reduced sway area occurred in the plyometric- and integrated-training groups. Generally, the plyometric training and integrated training increased the maximum angles at the hip and knee in the sagittal plane, reduced the maximum angles at the hip and ankle in the frontal and transverse planes in the lateral drop landing, and reduced the time to stabilization for knee flexion in the medial drop landing.

Conclusions:

After 6 weeks of plyometric training or integrated training, individuals with FAI used a softer landing strategy during drop landings and decreased their postural sway during the single-legged stance. Plyometric training improved static and dynamic postural control and should be incorporated into rehabilitation programs for those with FAI.Key Words: plyometric training, balance training, landings, ankle injuries

Key Points

• After 6 weeks of isolated plyometric or combined plyometric and balance training, people with functional ankle instability demonstrated increased lower extremity maximal sagittal-plane angles and decreased maximal frontal-plane and transverse-plane angles on ground contact.
• Static and dynamic postural control improved with plyometric training, which should be included in rehabilitation programs for patients with functional ankle instability.

Ankle sprains often occur during physical activities such as basketball and soccer that require sudden stops, jumping, landing, and rotation around a planted foot. Although a patient with an ankle sprain may recover without experiencing persistent pain and swelling, most patients go on to develop chronic dysfunction, such as recurrent ankle sprain or instability.¹ Athletes report a 73% recurrence rate of lateral ankle sprain,² and the impairments associated with ankle sprain persist in 40% of patients 6 months after injury.³ These findings demonstrate that prolonged ankle dysfunction or disability is commonly attributable to ankle sprain.Functional ankle instability (FAI) is identified in those with symptoms such as frequent episodes of ankle giving way and feelings of ankle instability⁴ after ankle sprains and often presents with sensorimotor deficits in muscle reaction time, joint position sense, postural sway, and time to stabilization (TTS) of ground reaction force.^5,6 Several outcome measures, including center-of-pressure (COP) sway, leg reaching with the Star Excursion Balance Test, surface electromyography, and kinematics, are used to evaluate the neuromuscular and biomechanical characteristics of individuals with FAI. Measurement of COP sway during the single-legged stance is an easy way to evaluate static postural stability.⁷ People with ankle instability had greater variation in the magnitude of medial-lateral COP than a healthy group.⁸ In addition, TTS is effective for detecting differences between unstable and healthy groups.^9,10 The TTS for ground reaction force is the time required to achieve stability after a dynamic perturbation, and this time is longer in those with FAI.^9,11 In addition to TTS for ground reaction force, TTS for kinematics is a novel method to investigate the ability to regain balance in people with FAI; participants with FAI took longer TTS for ankle inversion after 1-legged hopping.¹² The advantage of using TTS for kinematics instead of TTS for ground reaction force is to provide more specific information about dynamic neuromuscular control of body segments.Rehabilitation programs for ankle sprain include muscle-strengthening, balance-training, neuromuscular-training, and proprioceptive-training protocols. The use of balance training for ankle reeducation has become common in recent years and is effective in reducing episodes of inversion.¹³ Balance training focuses on improving the ability to maintain a position through conscious and subconscious motor control.¹⁴ Certain tools, such as the balance board,¹⁵ Dura Disc, minitrampoline,¹⁶ biomechanical ankle platform system (BAPS),¹⁷ and Star Excursion Balance Test,¹⁸ can be used to assist training. In individuals with FAI, a 12-week BAPS exercise program with progressive testing reduced the radius of COP in single-legged standing.¹⁷ Another study¹⁹ showed that 4 weeks of balance improved shank-rearfoot coupling stability during walking. Proprioceptive training attempts to restore proprioceptive sensibility, retrain afferent pathways, and enhance the sensation of joint movement.¹⁴ Eils and Rosenbaum²⁰ found that 6 weeks of multi-station proprioceptive exercise in individuals with ankle instability reduced the standard deviation of COP (referring to the 68.2% range of COP dispersion) and maximum sway of COP (referring to the maximum range of COP dispersion) in the medial-lateral direction. However, Coughlan and Caulfield²¹ reported no change in ankle kinematics during treadmill walking and running after a 4-week neuromuscular training program with the “both sides up” (BOSU) balance trainer.Plyometric training has positive effects on sport performance, including distance running,²² jumping,²³ sprinting, and leg-extension force.²⁴ The focus of plyometric training is the stretch-shortening cycle induced in the muscle-tendon complex, where soft tissues repeatedly lengthen and shorten.²⁵ Plyometric exercise is described as “reactive neuromuscular training”²⁶ because it increases the excitability of the neurologic receptors and improves reactivity of the neuromuscular system. Plyometric training desensitizes the Golgi tendon organs through adaptation to the stretch-shortening exercise, which allows the elastic components of muscles to tolerate greater stretching.²⁷ Previously, plyometric training was theorized to improve neuromuscular control and dynamic stability, reduce the incidence of serious knee injuries,²⁸ and reduce the risk of injury by increasing functional joint stability of the lower limbs.^23,28 Furthermore, 6 weeks of plyometric exercise enhanced results on functional performance testing in athletes after lateral ankle sprain.²⁹ Plyometric exercise is thought to enable segments to absorb joint force effectively by promoting the mechanical advantage of soft tissue structures³⁰ through increasing initial and maximal knee and hip flexion during the jump-landing task.³⁰ The increased knee-flexion and hip-flexion angles during landing protect the knee via hamstrings tension.^31,32To date, investigations on the effect of plyometric training have emphasized functional performance^28,29 or preventing anterior cruciate ligament injuries.^33,34 Data on the feasibility and effectiveness of plyometric training in those with FAI are very limited.²⁹ Therefore, our purposes were to determine the effects on lower extremity biomechanics of a 6-week plyometric-training program or a 6-week integrated program with plyometric and balance training in athletes with FAI. We hypothesized that both training programs would increase maximum joint angles in the sagittal plane and reduce the time needed to regain stability during drop-landing tasks. We further hypothesized that the integrated training would reduce postural sway during single-legged stance and decrease the center of mass (COM)-COP deviation during drop-landing tasks.     

Female Athletic Training Students' Perceptions of Motherhood and Retention in Athletic Training

Context:

Motherhood appears to be a catalyst in job turnover for female athletic trainers, especially those employed at the National Collegiate Athletic Association Division I level. However, most researchers examining this topic have investigated the perspectives of those who are currently employed rather than those who are preparing to enter the profession.

Objective:

To evaluate female athletic training students'' perceptions of motherhood and retention.

Design:

Qualitative study.

Setting:

Athletic training education program.

Patients or Other Participants:

A total of 18 female athletic training students volunteered to participate. They were enrolled in 1 Commission on Accrediting Athletic Training Education–accredited athletic training program and represented 3 levels of academic study.

Data Collection and Analysis:

The participants responded to a series of questions related to work–life balance and retention in athletic training. Analysis of the data followed a general inductive process. Credibility was established by interpretive member checks and peer review.

Results:

The first theme, clinical setting, speaks to the belief that work–life balance and retention in athletic training require an employment setting that fosters a family-friendly atmosphere and a work schedule (including travel) that allows for time at home. The second theme, mentorship, reflects the acknowledgment that a female mentor who is successful in balancing the roles of mother and athletic trainer can serve as a role model. The final theme, work–life balance strategies, illustrates the need to have a plan in place to meet the demands of both home and work life.

Conclusions:

A female athletic trainer who is successfully balancing her career and family responsibilities may be the most helpful factor in retention, especially for female athletic training students. Young professionals need to be educated on the importance of developing successful work–life balance strategies, which can be helpful in reducing attrition from the profession.Key Words: athletic training careers, work–life balance, mentors

Key Points

• Balancing the demands of a career, parenthood, and life can be difficult for all professionals, including female athletic trainers, and may affect their choice of work setting and their decision to remain in or leave the profession.
• Among the factors that can help female athletic trainers in the collegiate setting attain work–life balance are supportive work and home environments, flexible schedules, and good time-management skills.
• Female athletic trainers who have learned to balance their career and family responsibilities can serve as role models for students and young professionals.

Comparable with other occupational settings,¹ the athletic training profession has seen a steady increase in the employment of female athletic trainers, who now constitute 52% of the National Athletic Trainers'' Association membership.² These demographic data are somewhat deceiving in not reflecting age or employment setting, which reveal attrition from the profession and collegiate setting once a woman begins a family.³ The reasons for departure from the college or university clinical setting appear to be multifaceted, including irregular work hours, inflexible work schedules, and travel.^3,4 Mazerolle et al⁴ found that only 22 women with children were employed in the collegiate setting, a statistic supported by Milazzo et al⁵ and Kahanov et al.⁶ Similar to Mazerolle et al,³ Milazzo et al⁵ reported a small number of women with children in the collegiate setting, and Kahanov et al⁶ noted that only about one-fourth of all athletic trainers (ATs) in the collegiate setting are women. Furthermore, Kahanov and Eberman⁷ found that at about age 28, female ATs tend to leave the athletic training profession and postulated that work–life balance concerns have the greatest influence on occupation change.Work–life balance issues and time for parenting influence the decision to persist at the collegiate and professional levels, where job responsibilities include long hours (>40 hours per week) and travel, which can limit time spent at home with family.^3,4,6–8 Employment as an AT within the secondary school setting does not completely mitigate these concerns,⁹ but this setting appears to be seen as more helpful in allowing a woman to manage her parenting obligations.⁶ The literature regarding career planning complements findings that employment policies are important when a female AT selects an employment setting.¹⁰In general, women with or without children appear to experience greater conflicts between work and home than their husbands and men do.¹¹ Gender differences regarding work–life balance conflicts have not been reported within athletic training,³ despite the concerns raised by female ATs about the difficulties associated with parenting due to working long hours.^3,4,6,8,12 Female ATs have opted to leave the profession of athletic training because of work–life balancing problems,^3,8 and this concern seems to filter down to athletic training students (ATSs) because the extensive time commitment and reduced time available for parenting and spousal duties appear to influence retention in athletic training education programs.¹³ The role of the AT is demanding; however, emerging data indicate that work–life balance is possible, regardless of the clinical setting,^9,12,14–16 but it requires personal and professional work–life balance strategies. Furthermore, even after starting a family, female ATs can find success as ATs, including at the collegiate level.¹⁶Mazerolle and Goodman¹⁶ suggested the need for mentorship between mothers who are ATs and future professionals to increase retention. The purpose of our investigation was to explore the perceptions of female ATSs and the viability of a career in athletic training after starting a family. Particular emphasis was placed on their opinions regarding ways to establish work–life balance while managing the roles of AT and mother.     

Therapeutic Interventions for Increasing Ankle Dorsiflexion After Ankle Sprain: A Systematic Review

Context:

Clinicians perform therapeutic interventions, such as stretching, manual therapy, electrotherapy, ultrasound, and exercises, to increase ankle dorsiflexion. However, authors of previous studies have not determined which intervention or combination of interventions is most effective.

Objective:

To determine the magnitude of therapeutic intervention effects on and the most effective therapeutic interventions for restoring normal ankle dorsiflexion after ankle sprain.

Data Sources:

We performed a comprehensive literature search in Web of Science and EBSCO HOST from 1965 to May 29, 2011, with 19 search terms related to ankle sprain, dorsiflexion, and intervention and by cross-referencing pertinent articles.

Study Selection:

Eligible studies had to be written in English and include the means and standard deviations of both pretreatment and posttreatment in patients with acute, subacute, or chronic ankle sprains. Outcomes of interest included various joint mobilizations, stretching, local vibration, hyperbaric oxygen therapy, electrical stimulation, and mental-relaxation interventions.

Data Extraction:

We extracted data on dorsiflexion improvements among various therapeutic applications by calculating Cohen d effect sizes with associated 95% confidence intervals (CIs) and evaluated the methodologic quality using the Physiotherapy Evidence Database (PEDro) scale.

Data Synthesis:

In total, 9 studies (PEDro score = 5.22 ± 1.92) met the inclusion criteria. Static-stretching interventions with a home exercise program had the strongest effects on increasing dorsiflexion in patients 2 weeks after acute ankle sprains (Cohen d = 1.06; 95% CI = 0.12, 2.42). The range of effect sizes for movement with mobilization on ankle dorsiflexion among individuals with recurrent ankle sprains was small (Cohen d range = 0.14 to 0.39).

Conclusions:

Static-stretching intervention as a part of standardized care yielded the strongest effects on dorsiflexion after acute ankle sprains. The existing evidence suggests that clinicians need to consider what may be the limiting factor of ankle dorsiflexion to select the most appropriate treatments and interventions. Investigators should examine the relationship between improvements in dorsiflexion and patient progress using measures of patient self-reported functional outcome after therapeutic interventions to determine the most appropriate forms of therapeutic interventions to address ankle-dorsiflexion limitation.Key Words: chronic ankle instability, range of motion, stretching, joint mobilization

Key Points

• A static-stretching intervention as part of a standardized home exercise program had the strongest effects on ankle-dorsiflexion improvement after acute ankle sprains.
• Clinicians need to consider what may be the limiting factor of ankle dorsiflexion to select the most appropriate treatments and interventions.
• Investigators should examine the long-term effects of treatments on ankle dorsiflexion and a relationship between an improvement in ankle dorsiflexion and measures of patient self-reported and physical function to determine the most appropriate forms of therapeutic interventions to address limited dorsiflexion.

Lateral ankle sprain has been documented to be the most common lower extremity injury sustained during sport participation.^1–4 Approximately 85% of all ankle sprains result from an inversion mechanism and damage to the lateral ligamentous complex of the ankle.⁵ Injury to the lateral ligamentous complex at the ankle joint results in pain, swelling, and limited osteokinematics.⁶ A loss of normal ankle dorsiflexion usually is observed at the talocrural joint after lateral ankle sprain.^7–12The amount of available ankle dorsiflexion plays a key role in the cause of lower extremity injuries.^7,13–22 Limitation of dorsiflexion may be a predisposition to reinjury of the ankle^11,16 and several future lower limb injuries, including plantar fasciopathy,^13,20,21 lateral ankle sprains,^13,15,17,19 iliotibial band syndrome,¹⁴ patellofemoral pain syndrome,¹⁸ patellar tendinopathy,²² and medial tibial stress syndrome.¹⁴The importance of restoring ankle dorsiflexion after an acute ankle sprain often is emphasized in rehabilitation guidelines,⁹ and proper recovery of ankle dorsiflexion is a vital component of ankle rehabilitation. Inadequate restoration of ankle dorsiflexion may increase the risk of developing recurrent ankle sprain^11,16 and limit functional activities, such as walking, with long-term pain and disability.²³ Limited ankle-dorsiflexion range of motion (ROM) after lateral ankle sprain has been considered a predisposing factor for recurrent ankle sprain because diminished dorsiflexion prevents the ankle from reaching its closed-pack position by holding the ankle in a hypersupinated position. Therefore, ensuring appropriate restoration of ankle dorsiflexion after ankle sprain has important clinical implications for restoring full functional abilities, ultimately leading to reduced risk of recurrent ankle sprain.Clinicians perform several therapeutic interventions, such as stretching, manual therapy, electrotherapy, ultrasound, and exercises, to increase ankle dorsiflexion. However, the intervention or combination of interventions that most effectively improves ankle dorsiflexion has not been established. In previous systematic reviews,^24–26 researchers have examined the effects of specific intervention techniques of manipulative therapy on various outcome variables. In addition, Bleakley et al²⁷ conducted a systematic review with a comprehensive search of various therapeutic interventions to provide evidence for the management of ankle sprains and the prevention of long-term complications; however, the authors focused only on patients with an acute ankle sprain. Therefore, the purpose of this systematic review was to determine the magnitude of therapeutic intervention effects on and the most effective therapeutic interventions for restoring normal ankle dorsiflexion after ankle sprain. In contrast to previous reviews,^24–26 we comprehensively searched the existing literature to determine the effectiveness of various therapeutic intervention techniques in restoring ankle dorsiflexion in patients with acute, subacute, or recurrent ankle sprains. By providing a quantitative estimate of the magnitude of the effect of therapeutic interventions, our review provides a new perspective on the evidence of interventions to restore ankle dorsiflexion in various stages of ankle-sprain conditions.     

Scapular Bracing and Alteration of Posture and Muscle Activity in Overhead Athletes With Poor Posture

Context

Overhead athletes commonly have poor posture. Commercial braces are used to improve posture and function, but few researchers have examined the effects of shoulder or scapular bracing on posture and scapular muscle activity.

Objective

To examine whether a scapular stabilization brace acutely alters posture and scapular muscle activity in healthy overhead athletes with forward-head, rounded-shoulder posture (FHRSP).

Design

Randomized controlled clinical trial.

Setting

Applied biomechanics laboratory.

Patients or Other Participants

Thirty-eight healthy overhead athletes with FHRSP.

Intervention(s)

Participants were assigned randomly to 2 groups: compression shirt with no strap tension (S) and compression shirt with the straps fully tensioned (S + T). Posture was measured using lateral-view photography with retroreflective markers. Electromyography (EMG) of the upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) in the dominant upper extremity was measured during 4 exercises (scapular punches, W''s, Y''s, T''s) and 2 glenohumeral motions (forward flexion, shoulder extension). Posture and exercise EMG measurements were taken with and without the brace applied.

Main Outcome Measure(s)

Head and shoulder angles were measured from lateral-view digital photographs. Normalized surface EMG was used to assess mean muscle activation of the UT, MT, LT, and SA.

Results

Application of the brace decreased forward shoulder angle in the S + T condition. Brace application also caused a small increase in LT EMG during forward flexion and Y''s and a small decrease in UT and MT EMG during shoulder extension. Brace application in the S + T group decreased UT EMG during W''s, whereas UT EMG increased during W''s in the S group.

Conclusions

Application of the scapular brace improved shoulder posture and scapular muscle activity, but EMG changes were highly variable. Use of a scapular brace might improve shoulder posture and muscle activity in overhead athletes with poor posture.Key Words: shoulder, upper extremity, electromyography, braces

Key Points

• • Changes occurred in forward shoulder angle and the electromyographic activity of the upper, middle, and lower trapezius muscles when participants wore the scapular-stabilizing brace.
• • The compression garment and the tension straps selectively affected posture by reducing forward shoulder angle, but associated electromyographic activity changes were small and do not appear to be influenced by strap tension.
• • Scapular bracing appeared to produce beneficial changes in muscular activity and posture in healthy overhead athletes.
• • Clinicians might consider using a scapular brace as an adjunct to prerehabilitation and rehabilitation exercises in the athlete with poor posture.

Shoulder injuries are a common and disabling condition among athletes, particularly overhead athletes (baseball, softball, swimming, volleyball, track and field throwing events, and tennis). Recent National Collegiate Athletic Association (NCAA) injury-surveillance system research has shown that shoulder injuries account for 39.4% of all injuries in baseball,¹ 15.8% of injuries in softball,² and 21.7% of injuries in volleyball.³ Most of these injuries are classified as overuse injuries of muscles, tendons, and other tissues within the joint.^4–7 These overuse injuries can result from incorrect posture, mechanics, or techniques during overhead throwing, hitting, or striking motions.^8–10 Therefore, when working with athletes involved in overhead sports, clinicians should address posture, as well as sport-specific mechanics, during the evaluation and rehabilitation process.Forward-head, rounded-shoulder posture (FHRSP) is a specific postural anomaly that might play a role in the development of shoulder pain and pathologic conditions. Both forward-head (FH) and rounded-shoulder (RS) postures are defined as excessive anterior orientation of the head or glenohumeral joint relative to the vertical plumb line of the body.^8,11 These postural abnormalities often occur in conjunction and might be associated with other overuse injuries in the shoulder.^11–14 Many clinicians and researchers^8,14–16 believe that FHRSP alters scapular mechanics and muscular activity about the shoulder complex, causing altered force couples and scapular motions that result in tissue overuse, injury, and pain. Greenfield et al¹³ reported greater FH posture in patients with shoulder conditions than in healthy control participants. Griegel-Morris et al¹⁷ found an association between both FH and RS postures and reports of shoulder or scapular pain. Patients with preexisting FHRSP exhibited greater anterior tilt and upward rotation of the scapula during flexion motions at the shoulder.¹⁶ Acutely, adopting a FHRSP also creates increased scapular anterior tilt and upward rotation.¹⁸ Both of these specific scapular positions are related to shoulder conditions, suggesting that head and shoulder posture might influence the development and progression of overuse injuries.^8,14,15The altered positions of the scapula seen in individuals displaying FHRSP might change the electromyographic (EMG) activity of the musculature surrounding the scapula and glenohumeral joint, leading to tissue overload and injury. Patients with overuse shoulder conditions commonly display decreased serratus anterior (SA) and lower trapezius (LT) activity during shoulder motions.^8,16,19–21 Most researchers^8,14,15 believe that these altered EMG patterns disrupt the normal force couples surrounding the scapula, leading to dyskinesis and increasing the risk of pain. Researchers^16,19,20 studying participants with FH, RS, or both, postures have demonstrated that these postures are related to decreased SA activity and increased upper trapezius (UT) activity. Given that these alterations in SA and UT activity have been observed in individuals with shoulder conditions, posture might play an important role in the development or progression of overuse shoulder injuries.²¹One method for restoring normal posture and muscular activity around the scapula involves bracing or taping the scapulothoracic articulation. Scapular taping typically involves having the patient retract and depress the scapula, then applying tape over the scapular spine and medial border.^11,22–25 The patients who have used scapular taping generally displayed altered scapular position, decreased UT muscle activity, and decreased or improved pain profiles.^11,23–25 However, the application of adhesive tape might cause skin irritation in some patients and might not be a feasible intervention for daily or prolonged use. Based on the results of this research, companies have developed braces that patients can use to improve scapular position and muscle activity and treat shoulder conditions. These braces are designed to alter the posture of the shoulder and thoracic spine, causing favorable changes in scapular position, muscle activity, and movement . In studies of 15 healthy participants and 15 participants with scapular dyskinesis, Uhl et al^26,27 found that wearing 1 type of commercially available scapular brace increased posterior tipping, decreased upward rotation in the dominant and nondominant upper extremities, and decreased internal rotation during the lowering phase of elevation. They concluded^26,27 that the brace affected scapular position at rest and in the lower ranges of motion and might assist the scapular muscles in controlling scapular motion. Walther et al²⁸ compared the effects of a functional brace with traditional rehabilitation and home-based programs in a group of participants with subacromial impingement syndrome. After 6 and 12 weeks, the braced group demonstrated the same improvements in shoulder pain and function as traditional rehabilitation groups. The authors²⁸ concluded that bracing might be as effective as traditional methods for treating impingement syndrome. Thus, bracing might be a new tool to help correct scapular position and treat pain in individuals with shoulder conditions.Scapular braces commonly are used for athletes with shoulder conditions in conjunction with rehabilitation. Clinically, athletic trainers might use bracing or taping to complement a corrective exercise program or might use bracing or taping to restore more normal length-tension relationships in muscles during the exercise program itself. Because of this, a better understanding of the effects these braces have on healthy individuals is needed. In the few studies of the effects of bracing or taping on the shoulder girdle, investigators have not examined short-term changes that take place during the performance of rehabilitative exercises, and no researchers have evaluated the effects of a brace application on factors such as scapular muscle activity and posture in healthy overhead athletes. Therefore, the purpose of our study was to examine whether a scapular stabilization brace acutely altered posture and scapular muscle activity in healthy overhead athletes with FHRSP while performing 4 common rehabilitation exercises and 2 functional shoulder movements compared with not wearing the brace.     

Fatigue-Induced Alterations of Static and Dynamic Postural Control in Athletes With a History of Ankle Sprain

Context:

Sensorimotor control is impaired after ankle injury and in fatigued conditions. However, little is known about fatigue-induced alterations of postural control in athletes who have experienced an ankle sprain in the past.

Objective:

To investigate the effect of fatiguing exercise on static and dynamic balance abilities in athletes who have successfully returned to preinjury levels of sport activity after an ankle sprain.

Design:

Cohort study.

Setting:

University sport science research laboratory.

Patients or Other Participants:

30 active athletes, 14 with a previous severe ankle sprain (return to sport activity 6–36 months before study entry; no residual symptoms or subjective instability) and 16 uninjured controls.

Intervention(s):

Fatiguing treadmill running in 2 experimental sessions to assess dependent measures.

Main Outcome Measure(s):

Center-of-pressure sway velocity in single-legged stance and time to stabilization (TTS) after a unilateral jump-landing task (session 1) and maximum reach distance in the Star Excursion Balance Test (SEBT) (session 2) were assessed before and immediately after a fatiguing treadmill exercise. A 2-factorial linear mixed model was specified for each of the main outcomes, and effect sizes (ESs) were calculated as Cohen d.

Results:

In the unfatigued condition, between-groups differences existed only for the anterior-posterior TTS (P = .05, ES = 0.39). Group-by-fatigue interactions were found for mean SEBT (P = .03, ES = 0.43) and anterior-posterior TTS (P = .02, ES = 0.48). Prefatigue versus postfatigue SEBT and TTS differences were greater in previously injured athletes, whereas static sway velocity increased similarly in both groups.

Conclusions:

Fatiguing running significantly affected static and dynamic postural control in participants with a history of ankle sprain. Fatigue-induced alterations of dynamic postural control were greater in athletes with a previous ankle sprain. Thus, even after successful return to competition, ongoing deficits in sensorimotor control may contribute to the enhanced ankle reinjury risk.Key Words: sensorimotor control, neuromuscular activity, copers, balance, time to stabilization, Star Excursion Balance Test

Key Points

• When athletes were tested in the unfatigued state, only minimal differences in postural control were detected between athletes who had fully recovered from an ankle sprain and uninjured controls.
• Injured participants experienced larger fatigue-induced alterations of dynamic postural control than healthy controls.
• Persistent sensorimotor control deficits in recovered athletes might remain undetected in the unfatigued state.

Ankle sprains are the most common game-related injuries in team ball-sport athletes,¹ and are often associated with decreases in sensorimotor control, including proprioception (reduced joint position sense and kinesthesia), muscular strength, and balance performance (static and dynamic postural control). These alterations have been reported in individuals after acute ankle sprain^2,3 and in those with chronic ankle instability (CAI).^2,3 Along with additional complaints, such as swelling, pain, or episodes of “giving way,” sensorimotor deficits persist even years after injury.^4,5 Consequently, sensorimotor impairments associated with lower extremity injuries may contribute to performance impairments⁶ and increase the reinjury risk.⁷ Athletes who successfully return to high-level sports activities and report normal function without persistent complaints have previously been defined as copers.⁸ However, recent studies suggest that even though functional performance and self-reported disability in ankle-sprain copers are similar to those in individuals who have never sustained an ankle sprain,⁸ sensorimotor control might still be affected.^9,10The incidence of match injuries in soccer players increases toward the end of both halves,¹¹ suggesting that physical fatigue might play an important role in injury-related sensorimotor control changes. This concept is supported by a number of studies examining sensorimotor alterations after fatiguing exercise in healthy, uninjured participants; among the observed changes were reduced muscle strength and activity,¹² and altered proprioception¹³ and kinematics.¹⁴ Additionally, static postural control was assessed in most of these studies, showing an increase in postural sway due to localized fatigue of the ankle,¹⁵ knee, and hip¹⁶ muscles that can persist up to 10 minutes after exercise ends.¹⁷ Comparable results have been shown for fatiguing multijoint exercises¹⁷ and whole-body fatigue.¹⁸ Authors of only 2 studies have investigated the effects of fatiguing exercises on dynamic measures of postural control in healthy individuals¹⁹ and participants with CAI²⁰; however, because of different study populations and testing modalities, the effects remain uncertain.The findings described above suggest that long-term impairment of sensorimotor control exists after an ankle sprain and may even be present in those who do not develop persistent functional impairments and successfully return to preinjury levels of sport activity. To our knowledge, only 1 study²⁰ specifically investigated the effect of exercise-induced fatigue on participants with a previous ankle injury. Based on the findings of Gribble et al,²⁰ we hypothesize that these impairments are small under regular conditions but could expose athletes to an increased injury risk when they physically fatigue during intensive exercise.Therefore, the aim of our study was to investigate fatigue-induced alterations of static and dynamic postural control in a sample of ankle sprain copers and to compare the effects with those of uninjured controls. We proposed that changes in postural control due to fatigue would be more substantial in previously injured participants than in controls.     

Sport-Related Concussion and Sensory Function in Young Adults

Context:

The long-term implications of concussive injuries for brain and cognitive health represent a growing concern in the public consciousness. As such, identifying measures sensitive to the subtle yet persistent effects of concussive injuries is warranted.

Objective:

To investigate how concussion sustained early in life influences visual processing in young adults. We predicted that young adults with a history of concussion would show decreased sensory processing, as noted by a reduction in P1 event-related potential component amplitude.

Design:

Cross-sectional study.

Setting:

Research laboratory.

Patients or Other Participants:

Thirty-six adults (18 with a history of concussion, 18 controls) between the ages of 20 and 28 years completed a pattern-reversal visual evoked potential task while event-related potentials were recorded.

Main Outcome Measure(s):

The groups did not differ in any demographic variables (all P values > .05), yet those with a concussive history exhibited reduced P1 amplitude compared with the control participants (P = .05).

Conclusions:

These results suggest that concussion history has a negative effect on visual processing in young adults. Further, upper-level neurocognitive deficits associated with concussion may, in part, result from less efficient downstream sensory capture.Key Words: mild traumatic brain injuries, visual processing, event-related potentials, pattern-reversal visual evoked potentials

Key Points

• Visual processing and higher-level cognitive function were affected by concussion over the long term.
• The potential contributions of low-level sensory deficits to higher-order neurocognitive dysfunction after concussion should be studied.
• Event-related potentials have greater sensitivity than standard clinical tools and have the potential for clinical use.

The long-term and cumulative effects of concussive injuries represent a growing concern in the public consciousness. Concussion has been defined as “a complex pathophysiological process affecting the brain, induced by traumatic biomechanical forces.”^1,2 Estimated incidence rates for this condition, described as a “silent epidemic” by the Centers for Disease Control and Prevention,^2–5 range from a conservative 300 000 per year^4–6 to a more liberal and recent estimate of 3.8 million cases in the United States annually.⁷ Because 15% to 20% of these injuries result from sport participation,⁸ sport-related concussion represents an increasing concern, not only in the public domain but also in clinical and research settings.Based on clinical evaluations, concussed persons typically return to their preinjury level of functioning within 7 to 10 days of injury,^9,10 a time paralleling the acute neurometabolic cascade associated with concussion.^11,12 Indeed, several investigations^2,13–15 of young adult athletes with a concussion history indicate normal performance on a variety of clinical tests after the acute injury stage. However, more recent studies using highly sensitive assessment measures suggest that a multitude of chronic nervous system dysfunctions and cognitive deficits stem from concussive injuries.^16–28 Thus, the chronic, subclinical effects of concussion remain unclear, and measures sensitive to subtle and persistent deficits stemming from concussion are needed.Electroencephalography, which records brain activity from electrodes placed on the scalp, has been extensively used to examine neuroelectric activity in normal and clinical populations for almost a century. More recently, event-related potentials (ERPs; patterns of neuroelectric activity that occur in preparation for or in response to an event) have emerged as a technique to provide insight into the neural processes underlying perception, memory, and action.²⁹ The ERPs may be obligatory responses (exogenous) to stimuli in the environment or may reflect higher-order cognitive processes (endogenous) that often require active consideration by a person.³⁰Over the past decade, electroencephalography and ERPs in particular have demonstrated the requisite sensitivity to detect subtle, covert deficits in neurocognitive function associated with concussion^{17,23,27,31–33} (for review, see Broglio et al²⁹). Although several groups have evaluated ERP components, such as the ERN, N2, and P3, to examine attention, perception, and memory, few authors^23,34–36 have evaluated the effects of concussion on neuroelectric indexes of sensory function. In particular, only 3 studies have evaluated the influence of concussion on visual-evoked potentials (VEPs).^23,34,35 Findings from these studies suggest that for a significant portion of people, concussion may lead to chronic impairment in the neuroelectric correlates of visual processing.Believed to reflect the functional integrity of the visual system, VEPs are electrophysiologic signals passively evoked in response to visual stimuli that demonstrate a parietal-occipital maximum.^37–40 Efficient visual processing and sensory integration are essential to day-to-day functioning^34,41; however, the visual system of a concussed individual is typically unevaluated.³⁴ Thus, VEPs represent an underused and potentially valuable tool for evaluating and understanding sensory and nervous system dysfunction after injury.One VEP paradigm of particular utility is the pattern-reversal task (PR-VEP). This task uses an inverting patterned stimulus to evoke an electrocortical waveform, which is characterized by a negative deflection at about 75 milliseconds (N75), followed by a positive deflection at about 100 milliseconds (P1).⁴² The PR-VEP task is a standard in clinical research assessing central nervous system function⁴³ because of the high sensitivity, specificity, and intraindividual stability of PR-VEPs relative to VEPs elicited by other paradigms.^44,45 Specifically, the P1 elicited by this paradigm is less variable than the P1 components elicited by other paradigms, making it preferable for evaluating clinical populations.⁴⁰ For example, Sarnthein et al⁴⁵ observed a test-retest sensitivity of 95% and specificity of 99.7% for P1 component values. Further, Mellow et al,⁴⁶ evaluating binocular reproducibility in a single participant, observed test-retest coefficients of variation of 9% to 14% for P1 amplitude and 1% to 2% for P1 latency.The P1 component is an exogenous or obligatory potential and is the first positive-going deflection after stimulus presentation (or inversion). The P1 is thought to reflect sensory processes such as gating, amplification, and preferential attention to sensory inputs.^38,47 Within the context of the PR-VEP paradigm, the P1 is believed to index the functioning of the geniculostriatal pathway,³⁹ which is thought to mediate visual processing. The P1 component values can provide important information to researchers and clinicians: reduced P1 amplitude may indicate neuronal atrophy,⁴⁸ and increased P1 latency may indicate slowed neural conduction within the visual pathways.⁴⁹To our knowledge, only one set of authors²³ has evaluated the P1 component in relation to sport-induced concussion by using a pattern-reversal task to elicit VEPs in young and middle-aged adults. Approximately one-third of the participants who reported a concussion history evidenced P1 deficits, as determined by clinical diagnostic criteria. Such findings suggest that concussion may negatively influence the P1 component in a subset of persons, but further investigation is warranted to clarify the nature of the relationship between concussive injuries and the P1 VEP. Accordingly, the purpose of our investigation was to assess the relationship of sport-related concussion on visual processing using a pattern-reversal paradigm.     

Noise-Enhanced Eversion Force Sense in Ankles With or Without Functional Instability

Context

Force sense impairments are associated with functional ankle instability. Stochastic resonance stimulation (SRS) may have implications for correcting these force sense deficits.

Objective

To determine if SRS improved force sense.

Design

Case-control study.

Setting

Research laboratory.

Patients or Other Participants

Twelve people with functional ankle instability (age = 23 ± 3 years, height = 174 ± 8 cm, mass = 69 ± 10 kg) and 12 people with stable ankles (age = 22 ± 2 years, height = 170 ± 7 cm, mass = 64 ± 10 kg).

Intervention(s)

The eversion force sense protocol required participants to reproduce a targeted muscle tension (10% of maximum voluntary isometric contraction). This protocol was assessed under SRS_on and SRS_off (control) conditions. During SRS_on, random subsensory mechanical noise was applied to the lower leg at a customized optimal intensity for each participant.

Main Outcome Measure(s)

Constant error, absolute error, and variable error measures quantified accuracy, overall performance, and consistency of force reproduction, respectively.

Results

With SRS, we observed main effects for force sense absolute error (SRS_off = 1.01 ± 0.67 N, SRS_on = 0.69 ± 0.42 N) and variable error (SRS_off = 1.11 ± 0.64 N, SRS_on = 0.78 ± 0.56 N) (P < .05). No other main effects or treatment-by-group interactions were found (P > .05).

Conclusions

Although SRS reduced the overall magnitude (absolute error) and variability (variable error) of force sense errors, it had no effect on the directionality (constant error). Clinically, SRS may enhance muscle tension ability, which could have treatment implications for ankle stability.Key Words: chronic injuries, error, proprioception, sensorimotor system, stochastic resonance

Key Points

• In both participants with functional ankle instability and those with normal ankles, stochastic resonance stimulation immediately reduced the overall magnitude (absolute error) and variability (variable error) of force sense errors.
• The treatment had no effect on error directionality (constant error).

Inversion ankle sprains are common in physically active individuals.¹ Sprains to the ankle are often thought to be innocuous, but prolonged symptoms occur frequently, and individuals may continue to sustain sprains because of joint instability.^2–4 The term used to describe this syndrome is functional ankle instability (FAI), which can be more specifically defined as ankles with repetitive bouts of “giving way” or instability that leads to recurring sprains.^5,6 Currently, a single source of this instability has not been established, but the causal factors range from mechanical to functional inadequacies.⁷ Functional inadequacies associated with FAI include deficits in proprioception, kinesthesia, neuromuscular control, strength, and balance.⁷ Certain functional factors may be enhanced through rehabilitation exercises, but the results of other studies are equivocal regarding the degree to which rehabilitation can improve these functional deficiencies associated with FAI.^8–10 Consequently, researchers and clinicians may not be treating the correct causal factor of FAI and may need to refocus rehabilitation on other functional inadequacies. Alternatively, a complementary therapeutic intervention may be needed to amplify treatment effects.Force sense is a functional deficiency that has been documented with ankle instability.^11–15 Force sense is defined as the ability to detect tension from a muscle contraction.¹¹ Evidence indicates that individuals with FAI do not sense low-load eversion forces when replicating a targeted eversion muscle tension.^11–15 This inability to adjust eversion tension adequately is also correlated with episodes of giving way at the ankle joint and perceived ankle instability.^11,13 Consequently, force sense is important to investigate because the ability of muscles, in particular foot evertors, to generate adequate tension may be the difference between maintaining joint stability and sustaining an inversion ankle sprain.^11,13Muscle strains to the foot evertors can occur with ankle sprains,³ and accompanying damage to muscle mechanoreceptors from the strain is a likely source of force sense deficits associated with FAI. More specifically, injury to muscle spindle endings or Golgi tendon organs (or both) may be the root of force sense impairments.^16,17 When compromised, these muscle mechanoreceptors may distort force sense by inhibiting the agonist muscle and facilitating activation of the antagonist, potentially leading to a muscle''s inability to generate adequate tension.¹¹ In FAI, for example, the evertors may become inhibited, and the invertor muscles may be facilitated to generate a greater inversion moment, forcing the foot into a more vulnerable supinated position. Therapy to enhance force sense and prevent foot positions that predispose ankles to sprains is an obvious intervention, but we currently do not know if rehabilitation corrects force sense impairments.¹⁵ Perhaps a therapy that sensitizes these muscle mechanoreceptors is necessary to attain clinically relevant treatment effects.Recently, stochastic resonance stimulation (SRS) has been used as a complementary therapy for FAI to potentially facilitate the activation of muscle mechanoreceptors.^18–23 This therapy introduces subsensory mechanical or electrical noise through the skin to enhance the ability of the mechanoreceptors to detect and transmit weak sensory signals.^24–26 This subsensory noise can stimulate the mechanoreceptors to bring membrane potentials closer to threshold by changing ion permeability.²⁷ Essentially, SRS can prime the mechanoreceptors to fire and transmit sensory information.²⁷ Interestingly, SRS has been reported to facilitate the efferent output of the central nervous system by sensitizing tactile response²⁸ and amplifying reflexive muscle contractions in patients with sensorimotor deficits.^29,30 Thus, SRS may be used to enhance sensorimotor function in individuals with FAI.The use of SRS for treating FAI has mainly focused on improving static and dynamic balance, which can occur more quickly and to a greater extent than with rehabilitation alone.^18–23 Furthermore, when applied during static and dynamic balance, SRS has improved balance immediately.^18,20,23 Recent results²³ also indicate that customizing the stimulation intensity for individuals may enhance the treatment effects associated with SRS. In addition, customizing SRS intensity may improve balance to a greater degree in ankles with instability than in stable ankles.²³ This outcome supports the need to tailor the SRS intensity to achieve optimal balance enhancements.²³ Consequently, no single intensity has been identified to apply universally to all individuals to optimize SRS treatment effects. To improve balance, SRS may act on muscle mechanoreceptors to enhance the sensory feedback and reflexive contractions necessary for postural control.²³ Interestingly, the mechanoreceptors that may be affected by SRS to enhance balance are also responsible for improving force sense. Thus, SRS may sensitize mechanoreceptors to allow adequate adjustments in muscle tension.Based on the aforementioned evidence, we speculated that SRS administered at an optimal intensity to improve balance would enhance force sense in ankles with functional instability and that improvements in these ankles would be greater than those seen in stable ankles. The capacity of SRS to improve force sense of the evertors has not been examined, and research is needed to demonstrate that this stimulation may be a viable intervention to enhance treatment effects. Thus, the purpose of our study was to examine the effects of SRS on force sense in foot-evertor muscles in ankles with functional instability and in stable ankles. If successful for improving force sense, then SRS could be used as a complementary therapy for FAI and may have clinical relevance in allowing individuals with FAI to develop adequate muscle tension to prevent instability and sprains.     

Different Modes of Feedback and Peak Vertical Ground Reaction Force During Jump Landing: A Systematic Review

Context:

Excessive ground reaction force when landing from a jump may result in lower extremity injuries. It is important to better understand how feedback can influence ground reaction force (GRF) and potentially reduce injury risk.

Objective:

To determine the effect of expert-provided (EP), self-analysis (SA), and combination EP and SA (combo) feedback on reducing peak vertical GRF during a jump-landing task.

Data Sources:

We searched the Web of Science database on July 1, 2011; using the search terms ground reaction force, landing biomechanics, and feedback elicited 731 initial hits.

Study Selection:

Of the 731 initial hits, our final analysis included 7 studies that incorporated 32 separate data comparisons.

Data Extraction:

Standardized effect sizes and 95% confidence intervals (CIs) were calculated between pretest and posttest scores for each feedback condition.

Data Synthesis:

We found a homogeneous beneficial effect for combo feedback, indicating a reduction in GRF with no CIs crossing zero. We also found a homogeneous beneficial effect for EP feedback, but the CIs from 4 of the 10 data comparisons crossed zero. The SA feedback showed strong, definitive effects when the intervention included a videotape SA, with no CIs crossing zero.

Conclusions:

Of the 7 studies reviewed, combo feedback seemed to produce the greatest decrease in peak vertical GRF during a jump-landing task.Key Words: injury prevention, knee, feedback, landing biomechanics

Key Points

• All modes of feedback effectively reduced ground reaction force during a jump-landing task.
• Combination feedback demonstrated the strongest effect sizes for reducing ground reaction force compared with expert-provided and self-analysis feedback.
• More high-quality studies are needed to support the use of feedback interventions for altering lower extremity landing forces and decreasing lower extremity injury risk.

Landing is an essential athletic task used during many different sporting activities, including basketball, volleyball, and gymnastics.^1–3 The act of jumping and landing during these different sporting activities involves different magnitudes of ground reaction forces (GRFs).⁴ The GRF magnitudes have been reported to be greatest during the landing phase of a jump when the knee is between 0° and 25° of flexion, a point at which the knee must resist a rapid change in kinetic energy.⁵ Excessive GRFs may result in lower extremity injuries.^3,6–8The knee is largely responsible for energy attenuation of the lower extremity when landing from a jump,^9,10 so this joint may have increased susceptibility to injury during such a task. Researchers have identified the presence of damage to the subchondral bone, cartilage, and soft tissue due to extreme forces imposed on the lower extremity during selected landing activities.¹¹ A positive moderate correlation between increased vertical GRF and increased anterior tibial acceleration when landing from a jump supports the hypothesis that individuals landing with greater impact loads could have an increased risk of anterior cruciate ligament (ACL) injury.¹² Given that the main function of the ACL is preventing anterior translation of the tibia, landing with increased GRF and thus increased anterior tibial acceleration may place more strain on the ligament, increasing the likelihood of ligament rupture.To reduce the risk of injury associated with increased GRF during landing, different interventions have been used to decrease GRF by altering lower extremity biomechanics during landing. To our knowledge, no researchers have evaluated whether reducing an individual''s GRF decreases his or her risk of injury, but compelling data have suggested that higher GRF and other factors may increase the risk of substantially injuring the knee.¹³ Specifically, prospective data have shown that GRF during a jump-landing task was 20% higher in female athletes who sustained an ACL rupture than in athletes who did not.¹³ These data spark a compelling but unsubstantiated theory that reducing high GRFs may coincide with a decreased risk of knee injury. Clinical trials to evaluate the true prophylactic capabilities of reducing GRF to limit knee injuries are likely expensive and logistically difficult to conduct. Therefore, successfully identifying an intervention that can manipulate GRF is important before these studies are performed.Various methods have been implemented to teach proper landing biomechanics to prevent future injury.¹⁴ For example, feedback is a modality used to prompt an individual to correct potentially harmful biomechanics and reduce high GRF. Feedback can be defined as sensory information made available to the participant during or after a task in an attempt to alter a movement.¹⁵ It can include information related to the sensations associated with the movement (eg, the feel or sound the participant experiences while performing the task) or related to the result of the action with respect to the environmental goal.¹⁵ Different modes of feedback have been reported and include (1) expert-provided (EP) feedback through oral correction,¹⁶ oral instruction,^17,18 or visual demonstration¹⁶; (2) self-analysis (SA) feedback conducted with videotape correction^19,20 or self-correction from previous trials¹⁷; and (3) combination (combo) feedback that uses both EP and SA feedback.^19,21 Through EP feedback, professionals can analyze movements and provide various forms of oral and visual feedback to alter that task, whereas SA feedback requires the participant to identify movement characteristics that need to be altered and to adjust to change that specific task.Recently, a surge of injury-prevention programs have been implemented to reduce the risk of ACL injury in athletes.^22,23 These programs often incorporate feedback techniques and aim to reduce the risk of injury by teaching athletes to land properly to reduce stress on the lower extremity and potentially prevent acute and chronic lower extremity injuries.¹⁹ Altering the landing phase of a jump via various feedback methods could result in decreased GRFs and increased flexion angles at the knee, which may decrease the risk of lower extremity injury.Although programs incorporating feedback are increasing in popularity, the magnitude of the effect that different types of feedback have on reducing GRF has not been evaluated systematically. Knowledge of the efficacy of feedback on reducing potentially harmful GRF may help clinicians determine whether feedback should be incorporated into jump-landing training programs. Therefore, the purpose of our study was to systematically evaluate the current literature to determine the magnitude of immediate and delayed effects of EP, SA, and combo feedback interventions on reducing peak vertical GRF during a jump-landing task in healthy individuals.     

Muscle Spindle Traffic in Functionally Unstable Ankles During Ligamentous Stress

Context:

Ankle sprains are common in athletes, with functional ankle instability (FAI) developing in approximately half of cases. The relationship between laxity and FAI has been inconclusive, suggesting that instability may be caused by insufficient sensorimotor function and dynamic restraint. Research has suggested that deafferentation of peripheral mechanoreceptors potentially causes FAI; however, direct evidence confirming peripheral sensory deficits has been elusive because previous investigators relied upon subjective proprioceptive tests.

Objective:

To develop a method for simultaneously recording peripheral sensory traffic, joint forces, and laxity and to quantify differences between healthy ankles and those with reported instability.

Design:

Case-control study.

Setting:

University laboratory.

Patients or Other Participants:

A total of 29 participants (age = 20.9 ± 2.2 years, height = 173.1 ± 8.9 cm, mass = 74.5 ± 12.7 kg) stratified as having healthy (HA, n = 19) or unstable ankles (UA, n = 10).

Intervention(s):

Sensory traffic from muscle spindle afferents in the peroneal nerve was recorded with microneurography while anterior (AP) and inversion (IE) stress was applied to ligamentous structures using an ankle arthrometer under test and sham conditions.

Main Outcome Measure(s):

Laxity (millimeters or degrees) and amplitude of sensory traffic (percentage) were determined at 0, 30, 60, 90, and 125 N of AP force and at 0, 1, 2, 3, and 4 Nm of IE torque. Two-factor repeated-measures analyses of variance were used to determine differences between groups and conditions.

Results:

No differences in laxity were observed between groups (P > .05). Afferent traffic increased with increased force and torque in test trials (P < .001). The UA group displayed decreased afferent activity at 30 N of AP force compared with the HA group (HA: 30.2% ± 9.9%, UA: 17.1% ± 16.1%, P < .05).

Conclusions:

The amplitude of sensory traffic increased simultaneously with greater ankle motion and loading, providing evidence of the integrated role of capsuloligamentous and musculotendinous mechanoreceptors in maintaining joint sensation. Unstable ankles demonstrated diminished afferent traffic at low levels of force, suggesting the early detection of joint loading may be compromised.Key Words: functional ankle instability, microneurography, ankle arthrometry

Key Points

• Sensory traffic amplitude from muscle spindles increased during ligamentous loading of the ankle joint.
• Sensory traffic amplitude in functionally unstable ankles did not increase at low levels of anterior force when compared with healthy ankles.
• During inversion loading, functionally unstable ankles reached their peak sensory traffic amplitude earlier than did healthy ankles.

Ankle sprains are among the most common unintentional injuries related to sport and physical activity, accounting for approximately 15% of all collegiate sports injuries and approximately 800 000 emergency room visits per year in the United States.^1,2 Reports indicate that 30% to 75% of patients with ankle sprains develop repeated sensations of giving way or “rolling”—known as functional ankle instability (FAI)—despite efforts to rehabilitate and mechanically stabilize the joint.^3–5 Questions remain, however, because both injured and healthy patients may present with equivalent scores of mechanical laxity and sensory function, contrary to prevailing theories of joint stability that these deficits increase the likelihood of joint injury. Advances in technology now permit the simultaneous measurements of joint loading and laxity through arthrometry, as well as direct sensory recordings of individual mechanoreceptor populations through microneurography. The combination of these techniques may significantly advance our understanding of how these neuromechanical relationships related to joint stability differ among healthy individuals and those with repeated ankle sprains.Some investigators^4,6 originally suggested that FAI exists secondary to mechanical laxity of the lateral ligaments, because the excessive stress and strain directly damages these structures. Mechanical laxity has been investigated with a variety of tools including stress radiographs and ankle arthrometers; however, research has been inconclusive in establishing a relationship between mechanical laxity and FAI.^6–8 Consequently, the joint stability paradigm includes sensory deficits that could lead to loss of neuromuscular control and, therefore, sensations of instability.⁹ According to this theory, laxity, whether congenital or secondary to injury, may cause sensory deficits because inadequate tension in loose capsuloligamentous tissues prevents embedded mechanoreceptors from being stimulated, such that not enough action potentials are generated to achieve conscious perception.^10–12 Numerous authors^13,14 have investigated this theory by testing proprioception, using joint angle-replication measures and observing patients'' thresholds to detect passive motion (kinesthesia). However, across other joints, 10% to 40% of injured patients may exhibit sensory deficits yet excel functionally, whereas others are incapable of returning to their previous level of physical activity, even though mechanical laxity and sensation may be within normal limits.^15,16 This evidence suggests that traditional beliefs regarding the relationship between joint laxity and proprioception may overlook essential neuromechanical factors influencing the perception of potentially injurious joint pathomechanics and the maintenance of joint stability.Apart from the problem of joint laxity, discrete deficits in sensation and neuromuscular control have also been suggested as potential causes of FAI.^4,14 This theory proposes that although the structural properties of the ligament may heal after a lateral ankle sprain, some mechanoreceptors located within the ankle may not undergo reinnervation.⁴ The diminished transmission of sensory signals originating from the articular mechanoreceptors would reduce proprioception and lead to alterations in neuromuscular control.^11,17 However, current research has investigated these peripheral sensory signals using indirect methods. Joint angle replication, threshold to detect passive motion, and balance testing do not control for the spinal influences and cognitive abilities of the participant.^12,13 Additionally, balance and muscle (peroneal) reaction time measures have been used to measure proprioception but may largely depend on visual and vestibular feedback along with neuromuscular coordination.¹⁸ The use of these indirect measures in assessing joint sensation complicates the interpretation of these results.¹⁴Microneurography is an alternative technique that obtains real-time in vivo recordings directly from specific sensory receptors and, when combined with arthrometry, offers additional insight regarding the relationship among joint load, laxity, and mechanoreceptor function. The procedure involves insertion of a microelectrode directly into a peripheral nerve, where the summation of nerve action potentials is recorded, similar to electromyography (Figure 1).^19,20 Therefore, researchers²¹ can observe and quantify real-time sensory events close to the peripheral source before conscious awareness arises in the brain. Although several types of afferent or efferent signals can be collected using microneurography, muscle spindle afferents (MSAs) are identifiable and contain highly relevant sensory information for understanding joint proprioception.^22,23 Muscle spindles, through the fusimotor system, are responsive to changes in muscle length and the rate of change in length and, due to the muscle''s arrangement across joints, may also provide accurate signals for joint position and loading.²⁴ In addition, as reported by Johansson et al,²⁴ articular mechanoreceptors have a potent influence on spindle discharge in cats via innervations of the muscle spindles by small gamma motor neurons.^24–27 This suggests that changes in afferent feedback from capsuloligamentous mechanoreceptors may be reflected in the muscle spindle''s signals, and for this reason, their sensory traffic is believed to serve as a “final common input” for sensory information to the central nervous system of joint position and movement.²⁴ Muscle spindle activity has previously been studied using microneurography, but no authors have investigated the simultaneous response of the muscle spindle to a quantifiable joint load and position in patients complaining of ankle instability.Open in a separate windowFigure 1. Microneurography. Schematic representation of recording electrode recording voltage differences of action potentials summated from various afferents within a recording sphere.Contemporary scientific paradigms regarding joint stability do not fully explain existing data. More research is necessary to reconcile how joint load and laxity manifest within the nervous system and whether other receptors, such as muscle spindles, have the capacity to provide timely feedback on joint position and loading. The purpose of our study was to use microneurography to evaluate whether the progressive onset of ligamentous stress causes changes in MSA activity and to investigate potential sensory deficits that may exist in unstable ankles.     

Neuromuscular Fatigue and Tibiofemoral Joint Biomechanics When Transitioning From Non–Weight Bearing to Weight Bearing

Context:Fatigue is suggested to be a risk factor for anterior cruciate ligament injury. Fatiguing exercise can affect neuromuscular control and laxity of the knee joint, which may render the knee less able to resist externally applied loads. Few authors have examined the effects of fatiguing exercise on knee biomechanics during the in vivo transition of the knee from non–weight bearing to weight bearing, the time when anterior cruciate ligament injury likely occurs.Objective:To investigate the effect of fatiguing exercise on tibiofemoral joint biomechanics during the transition from non–weight bearing to early weight bearing.Design:Cross-sectional study.Setting:Research laboratory.Intervention(s):Participants were tested before (preexercise) and after (postexercise) a protocol consisting of repeated leg presses (15 repetitions from 10°–40° of knee flexion, 10 seconds'' rest) against a 60% body-weight load until they were unable to complete a full bout of repetitions.Results:The axial compressive force (351.8 ± 44.3 N versus 374.0 ± 47.9 N; P = .018), knee-flexion excursion (8.0° ± 4.0° versus 10.2° ± 3.7°; P = .046), and anterior tibial translation (6.7 ± 1.7 mm versus 8.2 ± 1.9 mm; P < .001) increased from preexercise to postexercise. No significant correlations were noted.Conclusions:Neuromuscular fatigue may impair initial knee-joint stabilization during weight acceptance, leading to greater accessory motion at the knee and the potential for greater anterior cruciate ligament loading.Key Words: knee, anterior cruciate ligament, axial loading

Key Points

• After closed chain exercise, participants demonstrated an increase in anterior tibial translation during simulated lower extremity weight acceptance.
• Observed alterations of knee biomechanics in a fatigued state may suggest increased anterior cruciate ligament strain during the latter part of the competition.

The anterior cruciate ligament (ACL) is one of the most commonly injured ligaments in the knee.^1–4 Injuries to the ACL frequently result from noncontact mechanisms, occurring when the knee is near full extension at the time of foot strike during activities such as landing, cutting, and deceleration-type maneuvers.⁵ Neuromuscular fatigue has been defined as any exercise-induced loss in the ability to produce force with a muscle or muscle group, involving processes at all levels of the motor pathway between the brain and the muscle.^6–8 Furthermore, fatigue has been suggested as a contributing risk factor for noncontact ACL injury^9–14 because the risk of noncontact knee injuries appears to increase later in games.^15,16 Specifically, prolonged exercise, which contributes to the delayed activation of muscles agonistic to the ACL,^13,17 has been suggested to increase risk of knee injury.¹³The quadriceps and hamstrings play a critical role in providing dynamic stability of the knee joint during sports activities,¹⁸ so various lower extremity fatigue protocols have been used to decrease the force-producing capabilities of these muscles.^10,19,20 Commonly, fatigue has been induced using isokinetic exercise protocols.^12,14,21,22 However, the true nature of muscle function and its effect on functional knee-joint biomechanics during sporting activity is likely difficult to assess from isolated forms of isometric, concentric, or eccentric contractions. Exercise that results in complete volitional exhaustion of a single muscle or muscle group rarely occurs during functional activity. Therefore, fatigue protocols that involve total lower extremity actions incorporating submaximal stretch-shortening cycles^23,24 may better mimic the type of muscular fatigue associated with prolonged weight-bearing activity.A number of authors^23,25,26 have examined the effect of lower extremity muscle fatigue on knee-joint biomechanics during jumping and landing activities. These results suggest that, depending on the fatigue protocol and task used, knee-flexion excursion (KF_EXC) may be either decreased or increased postexercise, thus modulating joint stiffness.^25,27 These changes in KF_EXC appear to primarily depend on the peak knee flexion obtained,^11,27 given that little to no change in the initial knee-flexion landing angle has been reported at ground contact in response to fatiguing exercise.^9,20 Moran et al²⁸ examined the effect of an incremental treadmill protocol and reported that exercise-induced alterations in tibial peak-impact acceleration were not attributed to changes in the knee angles at foot contact during a drop jump. This suggests that fatiguing exercise does not alter the initial knee-position angle at ground contact, but it may have a profound effect on knee-joint biomechanics during the weight-acceptance phase of landing. Because ACL injuries typically occur near the time of foot strike^1,4 with the knee in shallow flexion (average, 23° of initial knee flexion),²⁹ understanding the effect of fatiguing exercise on knee-joint biomechanics during this early weight-acceptance phase may lend further insight into the role of fatigue in ACL injury mechanisms.As the knee transitions from non–weight bearing (NWB) to weight bearing (WB), the natural anterior translation of the tibia (ATT) relative to the femur at low knee-flexion angles (eg, 15°–30°)^30,31 is restrained by the ACL.³¹ Greater axial loads^30,32,33 and slowing of the quadriceps and hamstrings onset times in response to an anterior tibial load may contribute to increased ATT¹⁴ at shallow knee-flexion angles; hence, fatigue may compromise the biomechanics of the tibiofemoral joint during weight acceptance, thereby modifying the strain placed upon the ACL with continued loading and subsequent maneuvers (eg, plant and cut). This may be particularly problematic in landing situations where KF_EXC decreases in response to fatiguing exercise.^9,25,34 Although decreased KF_EXC may represent a compensatory strategy to prevent collapse of the body due to fatigue of the quadriceps muscles,^10,34 the reduced KF_EXC may increase axial loads at the knee joint, and these greater axial loads may increase the amount of ATT.³⁵The purpose of our study was to investigate the effects of a lower extremity exercise protocol on tibiofemoral-joint biomechanics as the knee transitioned from NWB to WB in vivo. Based on previous fatigue studies of submaximal total lower extremity actions,^9,25 our expectation was that fatiguing exercise would decrease KF_EXC, increase axial compressive force (ACF), and subsequently increase ATT during transition from NWB to WB.     

Strength-Training Protocols to Improve Deficits in Participants With Chronic Ankle Instability: A Randomized Controlled Trial

Context:Although lateral ankle sprains are common in athletes and can lead to chronic ankle instability (CAI), strength-training rehabilitation protocols may improve the deficits often associated with CAI.Objective:To determine whether strength-training protocols affect strength, dynamic balance, functional performance, and perceived instability in individuals with CAI.Design:Randomized controlled trial.Setting:Athletic training research laboratory.Intervention(s):Both rehabilitation groups completed their protocols 3 times/wk for 6 weeks. The control group did not attend rehabilitation sessions.Results:The resistance-band protocol group improved in strength (dorsiflexion, inversion, and eversion) and on the visual analog scale (P < .05); the proprioceptive neuromuscular facilitation group improved in strength (inversion and eversion) and on the visual analog scale (P < .05) as well. No improvements were seen in the triple-crossover hop or the Y-Balance tests for either intervention group or in the control group for any dependent variable (P > .05).Conclusions:Although the resistance-band protocol is common in rehabilitation, the proprioceptive neuromuscular facilitation strength protocol is also an effective treatment to improve strength in individuals with CAI. Both protocols showed clinical benefits in strength and perceived instability. To improve functional outcomes, clinicians should consider using additional multiplanar and multijoint exercises.Key Words: functional ankle instability, functional performance, rehabilitation, Star Excursion Balance Test

Key Points

• Proprioceptive neuromuscular facilitation is an alternate strength-training protocol that was effective in enhancing ankle strength in those with chronic ankle instability.
• Neither the resistance-band protocol nor the proprioceptive neuromuscular facilitation protocol improved dynamic balance or functional performance in individuals with chronic ankle instability.

Lateral ankle sprains are very common in athletes¹ and account for 80% of injuries to the ankle.² These injuries can cause damage to the ligaments, muscles, nerves, and mechanoreceptors that cross the lateral ankle.³ Repetitive occurrences of lateral ankle sprains can lead to chronic ankle instability (CAI),^4–6 which is characterized by a subjective feeling of recurrent instability, repeated episodes of giving way, weakness during physical activity, and self-reported disability.^5,7,8 Patients with CAI often exhibit deficits in functional performance,^9–13 proprioception,^5,14–16 and strength.^4,5,16,17Because muscle weakness is associated with CAI, strength training is an essential part of the rehabilitation protocol¹⁷ to reduce the residual symptoms and, we hope, to prevent further episodes of instability from occurring. Strength training improves the physical conditioning of participants with ankle instability.^16,18–25 Strength training is thought to promote muscular gains during the first 3 to 5 weeks because it enhances neural factors.²⁶ Therefore, strength training may improve proprioception and balance deficits.^18,24,25 Conflicting findings exist in the current literature^14,23; thus, the relationship between strength training and other factors, such as balance, proprioception, or functional performance, requires further investigation.Most authors^{18,20,21,23,25} who have investigated the effect of strength training in people with CAI have used resistive-tubing exercises 3 times/wk for 4 weeks²⁰ to 6 weeks.^18,21,23,25 Other rehabilitation protocols have involved manual resistance at the ankle²² and isokinetic strength training.²⁴ Some researchers^{18,21,23–25} focused on strength-training protocols alone, whereas others^{19,20,22,27,28} have used multicomponent protocols that included balance exercises. Improvements in strength,^18,24,25 static balance,²⁴ joint position sense,¹⁸ and functional performance tests²⁴ were reported.Proprioceptive neuromuscular facilitation (PNF) is another form of progressive strength training that emphasizes multiplanar motion.²⁹ The goal of PNF techniques is to promote functional movement through facilitation (strengthening) and inhibition (relaxation) of muscle groups.³⁰ Although it is used more often at the shoulder, hip, and knee joints, PNF can also be used at the ankle.³¹ Two studies^32,33 compared the differences between common lower extremity strength-training programs and PNF strength-training patterns. The PNF pattern for both studies used the sequential movements of toe flexion, ankle plantar flexion and eversion, knee and hip extension, abduction, and internal rotation in the lower extremity. The PNF strength patterns were as effective as isokinetic training³² and weight training³³ in improving knee strength and functional performance. Based on the deficits seen in patients with CAI, PNF may be a beneficial treatment approach. Because PNF patterns are similar to functional movement patterns,²⁹ PNF strength techniques may also improve dynamic balance and functional performance.Although a multicomponent rehabilitation protocol is often used after an injury, examining 1 component, such as strength, in a controlled research setting will allow us to determine the effectiveness of a single approach. If strength training alone can improve multiple deficits seen in patients with CAI, it could save time for both clinician and patient. A resistance-band protocol has already been established as an effective strength-training protocol in improving some deficits in people with CAI.^18,24,25 Therefore, the purpose of our study was to compare the effects of resistance-band (RBP) and PNF protocols on strength, dynamic balance, functional performance, and perceived instability in individuals with CAI.     

Ankle Dorsiflexion Among Healthy Men With Different Qualities of Lower Extremity Movement

Context:

Lower extremity movement patterns have been implicated as a risk factor for various knee disorders. Ankle-dorsiflexion (DF) range of motion (ROM) has previously been associated with a faulty movement pattern among healthy female participants.

Objective:

To determine the association between ankle DF ROM and the quality of lower extremity movement during the lateral step-down test among healthy male participants.

Design:

Cross-sectional study.

Setting:

Training facility of the Israel Defense Forces.

Patients or Other Participants:

Fifty-five healthy male Israeli military recruits (age = 19.7 ± 1.1 years, height = 175.4 ± 6.4 cm, mass = 72.0 ± 7.6 kg).

Intervention(s):

Dorsiflexion ROM was measured in weight-bearing and non–weight-bearing conditions using a fluid-filled inclinometer and a universal goniometer, respectively. Lower extremity movement pattern was assessed visually using the lateral step-down test and classified categorically as good or moderate. All measurements were performed bilaterally.

Main Outcome Measure(s):

Weight-bearing and non–weight-bearing DF ROM were more limited among participants with moderate quality of movement than in those with good quality of movement on the dominant side (P = .01 and P = .02 for weight-bearing and non–weight-bearing DF, respectively). Non–weight-bearing DF demonstrated a trend toward a decreased range among participants with moderate compared with participants with good quality of movement on the nondominant side (P = .03 [adjusted P = .025]). Weight-bearing DF was not different between participants with good and moderate movement patterns on the nondominant side (P = .10). Weight-bearing and non–weight-bearing ankle DF ROM correlated significantly with the quality of movement on both sides (P < .01 and P < .05 on the dominant and nondominant side, respectively).

Conclusions:

Ankle DF ROM was associated with quality of movement among healthy male participants. The association seemed weaker in males than in females.Key Words: anterior cruciate ligament, hip, knee, lateral step-down test, patellofemoral pain syndrome

Key Points

• Healthy males with a moderate quality of movement on the lateral step-down test exhibited less ankle-dorsiflexion range of motion than those with a good quality of movement.
• When a lower quality of movement is present in males, clinicians should consider interventions to increase ankle dorsiflexion.

An altered lower extremity movement pattern, consisting of excessive femoral adduction and internal rotation leading to excessive knee valgus alignment, has been implicated as a risk factor for patellofemoral pain syndrome (PFPS) and noncontact anterior cruciate ligament injuries.^1–3 Various factors have been suggested to contribute to an altered movement pattern, including decreased strength of the ipsilateral hip musculature,^4,5 increased subtalar joint pronation,^6,7 and altered motor control.⁸ Assessment of movement pattern and the factors associated with it is therefore commonly performed in the evaluation of patients with PFPS, as well as in screening for the risk of knee injury.^9–11Another possible contributor to an altered movement pattern is the available ipsilateral ankle-dorsiflexion (DF) range of motion (ROM). Decreased ankle DF ROM can limit the forward progression of the tibia over the talus during activities that require simultaneous knee flexion and ankle DF (eg, squatting, stair descent). A possible compensation for the limited motion of the tibia could be subtalar pronation, which may shift the tibia and the knee medially into greater valgus alignment.^6,12–14 Some evidence already exists for the association between ankle DF and the lower extremity movement pattern. Decreased DF has been previously associated with increased knee valgus during a drop-land maneuver,¹⁴ a squat,¹⁵ and a step-down maneuver¹⁶ among healthy participants.One limitation of the current literature regarding this topic is the inclusion of only female participants in many of the studies evaluating lower extremity movement patterns and the associated factors.^{4,6,14,16–18} This is likely because of sex differences in kinematics, kinetics, and muscle-activation patterns during various functional activities.^8,19,20 Women have been shown to perform activities such as cutting, jumping, and landing with greater knee valgus alignment and greater knee extension than men.^19,20 These differences are hypothesized to account for the greater incidence of noncontact anterior cruciate ligament tears and PFPS among women.^1,2,21,22 Accordingly, authors^14,16 of the 2 studies that have previously linked decreased ankle DF with a faulty movement pattern included only female participants as well. A third study of a mixed population demonstrated only a statistical trend for the association between ankle DF and a faulty movement pattern.¹⁵ It is therefore unclear whether the association between ankle DF and lower extremity movement pattern is similar for both sexes.Paradoxically, another limitation of the current literature is the use of sophisticated 3-D motion-analysis systems in many of the studies evaluating lower extremity movement patterns.^2,4,14,17,18 Although this type of analysis certainly contributes to a high level of precision and reliability, clinicians and coaches typically do not have the access, time, or skill to operate such systems. Instead, visual observation is often relied on to assess movement patterns in the clinic or on the field. It is unknown, however, to what extent any movement deviations identified during 3-D motion analyses correlate with movement deviations identified visually. Consequently, the findings from 3-D motion analyses studies may be difficult to apply in the clinical setting or on the field. We therefore decided to assess whether ankle DF ROM is related to the quality of lower extremity movement as assessed visually among healthy male participants.The lateral step-down (LSD) test is frequently used to assess movement patterns of the lower extremity.^9,11,23–25 Piva et al²⁵ suggested a visually based rating system for classifying the quality of movement during the LSD test. The reliability of this rating system has been established previously.^16,25 Our hypothesis was that male participants with a lower quality of movement on the LSD would exhibit less ankle DF ROM.     

Fulfillment of Work–Life Balance From the Organizational Perspective: A Case Study

Context:

Researchers studying work–life balance have examined policy development and implementation to create a family-friendly work environment from an individualistic perspective rather than from a cohort of employees working under the same supervisor.

Objective:

To investigate what factors influence work–life balance within the National Collegiate Athletic Association (NCAA) Division I clinical setting from the perspective of an athletic training staff.

Design:

Qualitative study.

Setting:

Web-based management system.

Patients or Other Participants:

Eight athletic trainers (5 men, 3 women; age = 38 ± 7 years) in the NCAA Division I setting.

Data Collection and Analysis:

Participants responded to a series of questions by journaling their thoughts and experiences. We included data-source triangulation, multiple-analyst triangulation, and peer review to establish data credibility. We analyzed the data via a grounded theory approach.

Results:

Three themes emerged from the data. Family-oriented and supportive work environment was described as a workplace that fosters and encourages work–life balance through professionally and personally shared goals. Nonwork outlets included activities, such as exercise and personal hobbies, that provide time away from the role of the athletic trainer. Individualistic strategies reflected that although the athletic training staff must work together and support one another, each staff member must have his or her own personal strategies to manage personal and professional responsibilities.

Conclusions:

The foundation for a successful work environment in the NCAA Division I clinical setting potentially can center on the management style of the supervisor, especially one who promotes teamwork among his or her staff members. Although a family-friendly work environment is necessary for work–life balance, each member of the athletic training staff must have personal strategies in place to fully achieve a balance.Key Words: quality of life, support network, rejuvenation

Key Points

• Athletic trainers who create a balance between their personal and professional lives must recognize the personal strategies that work best for their work responsibilities and family and personal needs.
• A workplace that encourages and accepts a teamwork environment and has a supervisor who advocates for his or her employees; values personal and family time; and promotes a flexible, reasonable workload for each staff member is important for work–life balance.

Many factors influence an individual''s perceptions of quality of life, but often the time available for personal interests, obligations, and rejuvenation positively or negatively mediates the overall assessment. The extensive time commitment associated with meeting the job responsibilities for an athletic trainer (AT) often has been cited as a negative aspect of the profession and has been linked to concerns with work–life balance.^1–4 Moreover, demanding work schedules, including long hours spent at work, have been connected to job burnout^4,5 and job turnover.⁶ Furthermore, the organizational structure of the workplace, among other factors such as job characteristics, personal values, and sex ideology,^7,8 has been identified as a potential proponent of work–life balance for the employee.^7–9 More specifically, organizations that have more family-friendly policies in place, such as flextime and on-site child care, can better meet the personal and domestic needs of their employees, reducing the possibility of conflict between those different roles.⁹Long work hours are seemingly the major catalyst for students enrolled in athletic training educational programs^10,11 and certified ATs to consider a position or career change,^4,6 as well as a major precipitating factor leading to burnout and work–life balance concerns.^2,4 In studies by Dodge et al¹¹ and Mazerolle et al,¹⁰ limited time for family and parenting was a mechanism for many athletic training students to drop out of their undergraduate studies in athletic training to pursue more family-friendly careers. This finding is consistent with the findings of other researchers who have examined ATs employed at the collegiate level and have reported female ATs leave their positions to have more time to meet their family needs.^6,12 Recognizing the critical link among work hours, work–life balance, and retention, many athletic training scholars have investigated ways to improve the quality of life for the AT. Time away from the role of the AT has been found to be pivotal in helping promote professional commitment and personal rejuvenation, thus increasing the individual''s commitment to his or her organization.¹³In an investigation of the practices used by ATs employed within the National Collegiate Athletic Association Division I clinical setting, Mazerolle et al² discovered that coworker support, teamwork, and prioritization of both work and personal responsibilities were most successful in creating time away from the job. Support networks and job sharing among coworkers also have been shown to help the female AT remain in the Division I clinical setting¹² because these strategies allow the fulfillment of both professional duties and home-life obligations, including parenting, attending to personal interests, and completing household duties. Establishing a family-friendly work environment through organizational policies (eg, job sharing and flexible work schedules) is a critical link in promoting a balance between the work and life of the employee,⁹ yet few researchers have examined the organizational infrastructure from a holistic perspective. In other words, researchers have examined policy development and implementation from an individualistic perspective rather than from a cohort of employees working under the same supervisor. Therefore, the purpose of our study was to investigate what factors influence work–life balance within the Division I clinical setting from the perspective of an athletic training staff. Information gathered from this investigation may help other athletic training staffs develop similar policies to promote work–life balance and possibly illustrate ways to help socialize staff members into the workplace, which can help promote work–life balance.