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.     

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.     

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.     

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.     

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.     

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.     

Clinical Examination Results in Individuals With Functional Ankle Instability and Ankle-Sprain Copers

Context:

Why some individuals with ankle sprains develop functional ankle instability and others do not (ie, copers) is unknown. Current understanding of the clinical profile of copers is limited.

Objective:

To contrast individuals with functional ankle instability (FAI), copers, and uninjured individuals on both self-reported variables and clinical examination findings.

Design:

Cross-sectional study.

Setting:

Sports medicine research laboratory.

Patients or Other Participants:

Participants consisted of 23 individuals with a history of 1 or more ankle sprains and at least 2 episodes of giving way in the past year (FAI: Cumberland Ankle Instability Tool [CAIT] score = 20.52 ± 2.94, episodes of giving way = 5.8 ± 8.4 per month), 23 individuals with a history of a single ankle sprain and no subsequent episodes of instability (copers: CAIT score = 27.74 ± 1.69), and 23 individuals with no history of ankle sprain and no instability (uninjured: CAIT score = 28.78 ± 1.78).

Intervention(s):

Self-reported disability was recorded using the CAIT and Foot and Ankle Ability Measure for Activities of Daily Living and for Sports. On clinical examination, ligamentous laxity and tenderness, range of motion (ROM), and pain at end ROM were recorded.

Main Outcome Measure(s):

Questionnaire scores for the CAIT, Foot and Ankle Ability Measure for Activities of Daily Living and for Sports, ankle inversion and anterior drawer laxity scores, pain with palpation of the lateral ligaments, ankle ROM, and pain at end ROM.

Results:

Individuals with FAI had greater self-reported disability for all measures (P < .05). On clinical examination, individuals with FAI were more likely to have greater talar tilt laxity, pain with inversion, and limited sagittal-plane ROM than copers (P < .05).

Conclusions:

Differences in both self-reported disability and clinical examination variables distinguished individuals with FAI from copers at least 1 year after injury. Whether the deficits could be detected immediately postinjury to prospectively identify potential copers is unknown.Key Words: laxity, chronic ankle instability, giving way, range of motion

Key Points

• Compared with copers, participants with functional ankle instability had greater self-reported disability, talar tilt laxity, and pain with inversion and limited sagittal-plane range of motion.
• Identifying dynamic coping mechanisms may help to improve ankle-sprain prevention and treatment strategies.

Functional ankle instability (FAI) is a common sequela of ankle sprain, affecting approximately 32% to 47% of patients with symptoms including sensations of giving way, subsequent sprains, and instability.^1–3 Because these symptoms can limit physical activity and activities of daily living for years after injury^2,3 and decrease quality of life,¹ significant resources have been dedicated to elucidating the mechanisms behind this condition. However, despite extensive research in this area, the factors that contribute to the development and continuation of FAI are still not clear.^4–6In the search to clarify current understanding, recent reports^7,8 have focused on ankle instability definitions and patient inclusion criteria. Delahunt et al⁷ highlighted the varied inclusion criteria in studies of chronic ankle instability and FAI. They emphasized that variability in the pathologic group may partially account for inconsistent findings in the research literature. In contrast to the highly variable FAI groups, the comparison groups in studies of ankle instability are very consistent. Comparison groups are generally individuals who have never sprained either ankle (the uninjured or control group).⁹ Some authors^10,11 have studied copers as an alternative comparison group: individuals with a history of lateral ankle sprain but no recurrent instability for at least 1 year postinjury. Rather than compare individuals with FAI with individuals who have never sprained an ankle, it may be more appropriate to compare them with individuals who have been exposed to the initial risk factor (lateral ankle sprain) but have not gone on to develop FAI.¹⁰ Although the precise mechanism of coping is still unknown,^11–14 insight into coping mechanisms may help explain why individuals with FAI are unable to cope after ankle sprain. Additionally, once identified, successful coping mechanisms may be useful in treating FAI.In recent years, a number of authors have included comparison groups of ankle-sprain copers.^11–14 Differences in functional performance,¹¹ self-assessed disability,^11–14 ligamentous laxity,¹² injury history,^11–13 lower extremity kinematics,¹⁴ ankle-joint stiffness,¹³ fibular position,¹³ and postural control^13,15 have been investigated. However, more information about the clinical profiles of these individuals is needed because it may help us to prospectively differentiate potential copers and noncopers (postsprain but before development of FAI). Clinicians could then target individuals who are likely to have recurrent injury, leading to more efficient use of resources and enhanced injury-prevention efforts. Such a prospective clinical screening evaluation already exists for patients with anterior cruciate ligament injuries.¹⁶ However, the ankle-instability literature is still several steps away from this type of measure.We believe one of the next steps to better understand ankle-sprain copers is to compile a profile of a typical coper, consisting of injury history, self-reported disability, and clinical examination and to compare that profile with the profiles of both individuals with FAI and uninjured individuals. Thus, the primary purpose of our study was to explore potential group (FAI, coper, and uninjured) differences in both self-reported variables (injury history and disability) and clinical examination variables (laxity, pain, and range of motion).     

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.     

Thermoregulation and Stress Hormone Recovery After Exercise Dehydration: Comparison of Rehydration Methods

Context:

Athletic trainers recommend and use a multitude of rehydration (REHY) methods with their patients. The REHY modality that most effectively facilitates recovery is unknown.

Objective:

To compare 5 common REHY methods for thermoregulatory and stress hormone recovery after exercise dehydration (EXDE) in trained participants.

Design:

Randomized, cross-over, controlled study.

Patients or Other Participants:

Twelve physically active, non–heat-acclimatized men (age = 23 ± 4 years, height = 180 ± 6 cm, mass = 81.3 ± 3.7 kg, V̇o₂max = 56.9 ± 4.4 mL·min⁻¹·kg⁻¹, body fat = 7.9% ± 3%) participated.

Intervention(s):

Participants completed 20-hour fluid restriction and 2-hour EXDE; they then received no fluid (NF) or REHY (half-normal saline) via ad libitum (AL), oral (OR), intravenous (IV), or combination IV and OR (IV + OR) routes for 30 minutes; and then were observed for another 30 minutes.

Main Outcome Measure(s):

Body mass, rectal temperature, 4-site mean weighted skin temperature, plasma stress hormone concentrations, and environmental symptoms questionnaire (ESQ) score.

Results:

Participants were hypohydrated (body mass −4.23% ± 0.22%) post-EXDE. Rectal temperature for the NF group was significantly greater than for the IV group (P = .023) at 30 minutes after beginning REHY (REHY30) and greater than OR, IV, and IV + OR (P ≤ .009) but not AL (P = .068) at REHY60. Mean weighted skin temperature during AL was less than during IV + OR at REHY5 (P = .019). The AL participants demonstrated increased plasma cortisol concentrations compared with IV + OR, independent of time (P = .015). No differences existed between catecholamine concentrations across treatments (P > .05). The ESQ score was increased at REHY60 for NF, AL, OR, and IV (P < .05) but not for IV + OR (P = .217). The NF ESQ score was greater than that of IV + OR at REHY60 (P = .012).

Conclusions:

Combination IV + OR REHY reduced body temperature to a greater degree than OR and AL REHY when compared with NF. Future studies addressing clinical implications are needed.Key Words: heat stress, heat illness, hypohydration

Key Points

• A combination of intravenous and oral fluid replacement after exercise dehydration reduced heat-related symptoms more than a single mode of rehydration.
• If intravenous fluid replacement is warranted, the addition of simultaneous oral rehydration seems to add benefit to an efficient recovery.

The importance of rehydration (REHY) after exercise dehydration (EXDE) is emphasized by the many physiologic systems affected by hypohydration. Many of the adverse effects of hypohydration can impair recovery or hamper future exercise performance.^1,2 The popular mantra surrounding REHY is that intravenous (IV) fluid is more rapid and advantageous to the athlete. Whether IV fluid administration is necessary in many instances can be questioned.³ Furthermore, it may not be ethical or legal in athletes without a significant medical reason.⁴Previous researchers^5–14 have identified that cardiovascular and thermoregulatory strain corresponds with greater body fluid losses. When blood volume is limited, evaporative sweat losses are impeded and overall heat dissipation decreases.^5,9,14–17 After EXDE, if dehydration is lasting, body temperature decreases at a slower rate, and this can delay recovery.⁴ Cellular metabolism remains elevated in conjunction with high temperatures, further complicating recovery.¹⁵ A delay in exercise recovery could have deleterious implications, hindering the benefits of exercise sessions or increasing the amount and duration of cellular stress.¹⁵ Finish-line medical tent staffs treat many patients after endurance races (triathlons, marathons, ultramarathons) for EXDE.³ The recovery time for these patients is the limiting factor in the number of patients that a tent staff can treat at once and should be expedited when possible.³Decreased water content and heat stress negatively affect cell function and integrity. Circulating catecholamine concentrations are typically used to quantify sympathetic stress.^18–22 Previous researchers who compared modes of REHY offer a glimpse of cellular recovery. These studies^18,19,21 demonstrate no appreciable differences between modes of REHY on cellular stress recovery. However, no previous authors have included trials during which participants consumed fluids as thirst dictated or combined oral (OR) and IV fluids.Comparisons of modes of REHY demonstrate the importance of fluid replacement after EXDE.^{18,19,21,23,24} A lack of REHY delays recovery and profoundly decreases subsequent exercise performance.⁴ When equal volumes of fluid are provided, IV and OR fluid administration are essentially the same.^19,21,23 No previous researchers have tested post-EXDE recovery facilitated by ad libitum (AL) consumption or a combination of IV and OR fluids. Therefore, the purpose of our study was to compare modes of REHY after heat stress and EXDE in recovery of body temperature and sympathetic stress hormone concentrations. We hypothesized that a combination trial, including simultaneous IV and OR fluids, would maximize the rate at which body temperature and hormone levels return to baseline.     

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.     

Invalid Performance and the ImPACT in National Collegiate Athletic Association Division I Football Players

Context:

Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) is a computerized cognitive test battery commonly used for concussion evaluation. An important aspect of these procedures is baseline testing, but researchers have suggested that many users do not use validity indices to ensure adequate effort during testing. No one has examined the prevalence of invalid performance for college football players.

Objective:

To examine the prevalence of invalid scores on ImPACT testing.

Design:

Cross-sectional study.

Setting:

National Collegiate Athletic Association Division I university.

Patients or Other Participants:

A total of 159 athletes (age = 20.3 ± 1.41 years; range = 17.8–23.7 years) from a Division I collegiate football team participated.

Intervention(s):

An informational intervention regarding the importance of concussion testing to promote safety was administered before testing for the most recent season.

Main Outcome Measure(s):

We examined preseason ImPACT testing data across a 3-year period (total assessments = 269). Based on invalid and sandbagging indices denoted by the ImPACT manual, protocols were examined to indicate how many invalid indices each athlete had.

Results:

A total of 27.9% (n = 75) of assessments were suggestive of invalid scores, with 4.1% (n = 11) suggesting invalid responding only, 17.5% (n = 47) indicating “sandbagging” only, and 6.3% (n = 17) showing both invalid and sandbagging responding. The informational intervention did not reduce the prevalence of invalid responding.

Conclusions:

These findings highlight the need for further information about the ImPACT validity indices and whether they truly reflect poor effort. Future work is needed to identify practices to reliably target and reduce invalid responding.Key Words: concussions, neuropsychological tests, malingering

Key Points

• More than 25% (n = 75) of the participants'' baseline cognitive testing suggested suboptimal effort.
• Providing information about concussion risks and the importance of cognitive testing did not reduce the prevalence of poor effort; however, instructing athletes to repeat testing did reduce it.
• More research is needed to determine effective and efficient strategies to reduce the prevalence of invalid performance on Immediate Post-Concussion Assessment and Cognitive Testing.

Sport-related concussions have been a growing topic of interest in the popular media and clinical neuropsychology.¹ Concussions, often termed mild traumatic brain injuries, are defined as traumatically induced, typically reversible impairments of neurologic function. Researchers^2–5 have estimated the prevalence of US sport-related concussions at about 300 000 per year. This figure is likely an underestimate because many concussions are not reported.⁶ Given its popularity and perceived risk of concussions, football is the most frequently examined sport, and an estimated 5% to 9% of collegiate players sustain concussions each year.^2,4,7 Across various college sports, concussions compose 5.8% to 6.2% of all reported injuries.^3,7Several computerized cognitive test batteries have been developed to assist in the diagnosis of sport-related concussions.^8–10 Nearly 95% of athletic trainers in a recent survey reported conducting baseline cognitive testing of some form.¹¹ However, only 51.9% of those athletic trainers who administered computerized baseline testing examined the tests for validity concerns.¹¹ Without valid baseline testing, determining whether postinjury testing shows a meaningful change from previous levels of functioning can be challenging.¹² For example, Hunt et al¹³ showed 11% of high school athletes given a brief neuropsychological test battery exhibited poor effort on testing and athletes with invalid protocols had lower scores on several tests within the battery.A common computerized neuropsychological test is the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT), which is used not only by the National Football League and National Hockey League but by several US Olympic teams and many universities throughout the United States and Canada.¹² The ImPACT manual¹² provides indices to detect invalid responding during testing, but no one has examined the prevalence of invalid test profiles within a sample of student-athletes tested under typical conditions. Data from student volunteers suggest that 25.7% exhibit suboptimal effort on testing.¹⁴ Therefore, the purpose of our study was to determine the prevalence of invalid responding in student-athletes by examining preseason ImPACT testing in football players across a 3-year period. We hypothesized that poor effort would be common within this sample because researchers^13,14 have shown that 11% of high school students and more than 25% of student volunteers exhibited suboptimal effort on neuropsychological testing. Furthermore, athletes may be motivated to intentionally suppress their baseline performances to limit detection of concussions during the season and to be allowed to continue to participate.     

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.     

Injuries in a Japanese Division I Collegiate American Football Team: A 3-Season Prospective Study

Context:

Previous research on American football injuries in Japan has focused on incidence proportion in terms of the number of injuries divided by the number of players. This is the first study to examine injury rates over several seasons.

Objective:

To conduct a prospective study of injuries in a Japanese Division I collegiate American football team over the 2007 through 2009 seasons.

Design:

Cohort study.

Setting:

Collegiate football team at Doshisha University, Kyoto, Japan.

Patients or Other Participants:

All 289 athletes who played on the collegiate Division I football team during the 2007 through 2009 seasons.

Main Outcome Measure(s):

A certified athletic trainer kept a daily record of all practice and game injuries. Injury rates were calculated according to season, injury type, body part, severity, and mechanism. Injuries were also analyzed according to position of player, school year, and playing experience.

Results:

The game injury rate (GIR; 32.7 injuries/1000 athlete-exposures) was higher than the practice injury rate (PIR; 10.9 injuries/1000 athlete-exposures) over the 3 seasons (P < .05). The PIR was higher among Japanese players than the comparable United States collegiate football injury rates (5.8–7.0 injuries/1000 athlete-exposures). Ankle and foot injuries occurred more frequently during games, whereas thigh and gluteal injuries occurred more frequently during practices.

Conclusions:

Our data show differences between games and practices in terms of injury rates, body parts injured, and positions of players injured. The high PIR in Japan may be due to the increased contact during practices and length of practices compared with the United States. Further research involving multiple teams is recommended to validate the trends noted in this study. The expanded data set could assist in the development of safety regulations and preventive interventions for Japanese football.Key Words: Japanese football, American football, college football, injury rates

Key Points

• The practice injury rate for Japanese collegiate football players was higher than in the United States. This may be explained by the increased contact during practice and unregulated practice length in Japan.
• Ankle and foot injuries occurred more often during games, whereas thigh and gluteal injuries were more frequent during practices.

American football is 1 of the most popular sports in the United States, played by more than 60 000 college-level male athletes in 2008 and more than 1 million high school male athletes in 2009.^1,2 Football has a high injury risk,³ and as the number of players has grown, so has the number of injuries experienced.⁴ Previous researchers^3,5–13 have examined football injuries in a variety of conferences, divisions, and schools. Football had the highest number of reported injuries among the 5 fall collegiate sports.³ The National Collegiate Athletic Association (NCAA) reported 266 943 injuries during the 2004–2005 through 2008–2009 seasons. Hootman et al¹⁴ noted that football had the highest number of serious sport-related injuries (eg, anterior cruciate ligament injury, concussion) among the 15 collegiate sports. Ramirez et al¹³ found that the estimated cost per football injury increased by approximately 20% from 1977 to 1986. Injured athletes may also experience psychological trauma such as fear of reinjury or surgery.¹⁵ The NCAA has implemented measures to reduce injury risk. In 1998, limits were placed on the number of practices and the number of contacts allowed during spring football practices in an attempt to reduce the injury rate, which was twice as high during spring football practices as during fall practices.⁵Data released in 2008 by the Japanese Football Association¹⁶ indicated that approximately 20 000 football players participated on 402 teams, including 11 junior high school teams, 112 high school teams, 218 university teams, and 61 adult club teams. Despite the relatively large number of players, research regarding football injuries in Japan is limited.^17–21 Moreover, unlike in the United States, no evidence-based rule changes have been implemented to try to reduce injuries in Japanese football.Previous Japanese studies have focused on incidence proportion, calculated as the number of injuries divided by the number of players. Although incidence proportion can directly measure the risk of injury, which is useful information for the general public, this value is rarely used in the sport-injury literature and is difficult to compare among different sports.²² Injury rate is easier to compare among different sports and permits comparisons within the sport, both nationally and internationally.Only 1 Japanese study²⁰ has examined injury rates according to athlete-exposures (AEs). However, that study was conducted during a single season, and no studies have followed a team over several seasons. In comparison, research in the United States has examined injury rates based on multiple-year records.^{5,7,10,11,13,14} We aimed to examine practice and game injury rates according to season, injury type, body part, severity, and mechanism in a Japanese Division I collegiate football team over 3 consecutive seasons. Injuries were also analyzed according to position of player, school year, and playing experience.     

Anticipatory Effects on Lower Extremity Neuromechanics During a Cutting Task

Context

 Continued research into the mechanism of noncontact anterior cruciate ligament injury helps to improve clinical interventions and injury-prevention strategies. A better understanding of the effects of anticipation on landing neuromechanics may benefit training interventions.

Objective

 To determine the effects of anticipation on lower extremity neuromechanics during a single-legged land-and-cut task.

Design

 Controlled laboratory study.

Setting

 University biomechanics laboratory.

Participants

 Eighteen female National Collegiate Athletic Association Division I collegiate soccer players (age = 19.7 ± 0.8 years, height = 167.3 ± 6.0 cm, mass = 66.1 ± 2.1 kg).

Intervention(s)

 Participants performed a single-legged land-and-cut task under anticipated and unanticipated conditions.

Main Outcome Measure(s)

 Three-dimensional initial contact angles, peak joint angles, and peak internal joint moments and peak vertical ground reaction forces and sagittal-plane energy absorption of the 3 lower extremity joints; muscle activation of selected hip- and knee-joint muscles.

Results

 Unanticipated cuts resulted in less knee flexion at initial contact and greater ankle toe-in displacement. Unanticipated cuts were also characterized by greater internal hip-abductor and external-rotator moments and smaller internal knee-extensor and external-rotator moments. Muscle-activation profiles during unanticipated cuts were associated with greater activation of the gluteus maximus during the precontact and landing phases.

Conclusions

 Performing a cutting task under unanticipated conditions changed lower extremity neuromechanics compared with anticipated conditions. Most of the observed changes in lower extremity neuromechanics indicated the adoption of a hip-focused strategy during the unanticipated condition.Key Words: anticipation, anterior cruciate ligament, biomechanics

Key Points

• Participants demonstrated that the hip joint played a substantially greater role as part of the neuromechanical landing strategy during the unanticipated condition.
• The unanticipated condition was characterized by only a few changes in landing mechanics consistent with greater anterior cruciate ligament loading.

Noncontact anterior cruciate ligament (ACL) injuries are a common occurrence in sport.¹ When compared with their male counterparts, females are at a 3.5 to 4 times higher risk of sustaining an injury to the ACL.^2–4 Among ACL injuries in females, the most frequent mechanism of injury occurs in the absence of contact. On average, 70% to 80% of all noncontact ACL tears involve rapid deceleration during a landing or cutting maneuver.^2,5 To develop clinical interventions that aim to prevent injuries, research efforts have been directed at determining how biomechanical and neuromuscular risk factors manifest within the ACL injury mechanism.^6–16 Most authors^9,14,17,18 who investigated these risk factors and their role in the ACL injury mechanism focused on kinetic and kinematic variables measured during landing and cutting tasks. These results suggest that deleterious knee kinetics are characterized by greater external-flexion, abduction, and internal-rotation moments.^9,14,17,18 In addition, other kinematic factors, such as smaller hip and knee sagittal-plane angles along with greater frontal-plane angles and ranges of motion, have been identified as components of an at-risk movement pattern.^{7,11,14,17,18} This movement pattern has also been evident during direct observations of ACL injuries using video analysis of in-game footage and as part of a prospective investigation of ACL injury risk.^6,19,20Many of the biomechanical studies^{8,11,13,21,22} that investigated landing mechanics and movement patterns used experimental models in which participants completed preplanned movement tasks (eg, cutting or landing or both) with an anticipated or known direction of movement. However, executing movement tasks under such conditions may not accurately represent the dynamic and evolving environment in which athletic activities occur. Researchers, therefore, try to mimic the uncertainty of these conditions by having participants perform tasks without knowing which direction to move in before they actually initiate the movement.^{7,9,12,14,15,17,18,23,24} It is interesting, however, that direct comparisons between lower extremity mechanics performed under anticipated and unanticipated conditions have not been conducted as often as comparisons between groups that performed only unanticipated conditions. Yet, analyzing biomechanical and neuromuscular variables under either condition alone may not provide sufficient information about the neuromechanical strategies that athletes adopt when faced with situations that more closely resemble the dynamic athletic environment. That may ultimately limit the insight available to develop appropriate training programs to prevent injury.The few researchers^12,14,15 who directly compared anticipated and unanticipated conditions generally indicated that lower extremity mechanics were exacerbated when movement tasks were performed under unanticipated conditions. These results, however, primarily described differences in knee-joint biomechanics (ie, kinematics and kinetics) between movement tasks performed under anticipated and unanticipated conditions. Much less is known about the effects of anticipation on the biomechanics of more proximal joints (ie, the hip) or the underlying neuromuscular-control strategies that athletes adopt to cope with the demands presented by the unanticipated conditions.^8,25 Collecting electromyographic (EMG) data during dynamic movement tasks generally enhances the interpretation of traditional kinematic and kinetic data and, in the case of unanticipated movement conditions, would provide better global insight into the neuromechanical strategies that athletes adopt under suboptimal conditions for planning and executing task-appropriate movement patterns. Given the importance of hip-joint function in controlling upper body momentum and influencing lower body mechanics during landing,^10,21,26,27 the lack of knowledge about proximal biomechanics and muscle- activation patterns (eg, the gluteus maximus and medius) during unanticipated landing and cutting tasks could possibly limit insight into how neuromechanical strategies affect the ACL injury mechanism.The purpose of our study was to analyze the effects of anticipation on lower extremity neuromechanics during a single-legged land-and-cut task. Specific emphasis was placed on muscle-activation patterns, in addition to kinematic and kinetic analyses, to obtain a more complete understanding of the neuromechanical strategies during landing in relation to the ACL injury mechanism. We hypothesized that landing under unanticipated conditions would be characterized by more deleterious joint kinematics, kinetics, and muscle-activation patterns in regard to the risk of noncontact ACL injury.     

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.