Patient-Reported Outcomes in Male and Female Collegiate Soccer Players During an Athletic Season

Context

 Clinicians are urged to document patient-based outcomes during rehabilitation to measure health-related quality of life (HRQOL) from the patient''s perspective. It is unclear how scores on patient-reported outcome instruments (PROs) vary over the course of an athletic season because of normal athletic participation.

Objective

 Our primary purpose was to evaluate the effect of administration time point on HRQOL during an athletic season. Secondary purposes were to determine test-retest reliability and minimal detectable change scores of 3 PROs commonly used in clinical practice and if a relationship exists between generic and region-specific outcome instruments.

Design

 Cross-sectional study.

Setting

 Athletic facility.

Patients or Other Participants

 Twenty-three collegiate soccer athletes (11 men, 12 women).

Main Outcome Measure(s)

 At 5 time points over a spring season, we administered the Disablement in the Physically Active Scale (DPA), Foot and Ankle Ability Measure-Sport, and Knee Injury and Osteoarthritis Outcome Score (KOOS).

Results

 Time effects were observed for the DPA (P = .011) and KOOS Quality of Life subscale (P = .027). However, the differences between individual time points did not surpass the minimal detectable change for the DPA, and no post hoc analyses were significant for the KOOS-Quality of Life subscale. Test-retest reliability was moderate for the KOOS-Pain subscale (intraclass correlation coefficient = 0.71) and good for the remaining KOOS subscales, DPA, and Foot and Ankle Ability Measure-Sport (intraclass correlation coefficients > 0.79). The DPA and KOOS-Sport subscale demonstrated a significant moderate relationship (P = .018).

Conclusions

 Athletic participation during a nontraditional, spring soccer season did not affect HRQOL. All 3 PROs were reliable and could be used clinically to monitor changes in health status throughout an athletic season. Our results demonstrate that significant deviations in scores were related to factors other than participation, such as injury. Finally, both generic and region-specific instruments should be used in clinical practice.Key Words: health-related quality of life, patient-centered outcomes, injury history, evidence-based practice

Key Points

• The Disablement in the Physically Active Scale, Foot and Ankle Ability Measure-Sport, and Knee Injury and Osteoarthritis Outcome Score scales are reliable instruments that have been used clinically to assess activity limitations and participation restrictions in collegiate athletes.
• Significant changes in health-related quality of life are likely to be associated with an injury that restricts athletic participation or another factor rather than participation itself.
• To capture all dimensions of health-related quality of life, clinicians should use both a generic and a region-specific instrument.

As evidence-based practice grows in the field of athletic training, clinicians are encouraged to document clinical outcomes to demonstrate the effectiveness of treatments or interventions to improve patient care.¹ Patient-reported outcome instruments (PROs) are patient-centered outcomes used in clinical practice to capture the patient''s perspective regarding physical impairment, functional limitations, and overall health-related quality of life (HRQOL).¹ The HRQOL is a measure of a person''s function in everyday life and an evaluation of his or her physical, psychological, and social aspects of health derived from personal beliefs, preferences, experiences, and expectations.^2,3 Most often, HRQOL is measured using PROs, and numerous PROs have been created. These instruments are commonly classified into 3 categories: generic, region specific, and dimension specific.¹ Generic PROs measure the patient''s perception of his or her overall health and can capture a range of health-related problems.¹ Examples of generic PROs are the Short-Form 12⁴ and the Disablement in the Physically Active Scale (DPA).^5,6 Region-specific PROs assess the patient''s perception of function for a certain region of the body, such as the ankle or knee.¹ Examples of region-specific PROs that are used in athletes are the Foot and Ankle Ability Measure-Sport (FAAM-S)⁷ and the Knee Injury and Osteoarthritis Outcome Score (KOOS).⁸Health-related quality of life has not been studied thoroughly in athletes and is a topic of interest to athletic training researchers and clinicians.^9–13 Throughout a traditional or nontraditional athletic season, athletes participate in different team activities that may contribute to an increase or decrease in HRQOL, regardless of the athlete''s injury status. Given that athletes are involved in practices, games, agility training, conditioning, and weight training, we must consider the effect of continuous athletic participation on HRQOL. If participation in these activities can change HRQOL, use of these instruments after injury may be confounded by this phenomenon and influence how PRO scores are interpreted. Furthermore, when using PROs in clinical practice, it is important to know their test-retest reliability. The ability of an instrument to measure a change in health status depends on the instrument''s ability to measure consistently over time. Assessing the test-retest reliability of these instruments will allow us to calculate the minimal detectable change (MDC). At this time, neither the test-retest reliability nor the MDC have been calculated for the DPA in healthy, physically active persons participating in intercollegiate athletics. In addition, multiple PROs can be used to assess different dimensions of HRQOL. Currently, we do not know if a relationship exists between generic and region-specific instruments. If a relationship does exist, athletic trainers may be able to use fewer PROs to assess HRQOL in their patients.Our study had 3 purposes. The first purpose was to determine the test-retest reliability and calculate the MDC value of the DPA, FAAM-S, and KOOS subscales in collegiate soccer athletes with a history of lower extremity injury. We hypothesized that these instruments would demonstrate good test-retest reliability in this population. The second purpose was to determine the effect of administration time point on HRQOL scores in collegiate soccer players during an athletic season. We hypothesized that the administration time point would not affect HRQOL. Finally, we aimed to determine if a relationship exists between the DPA and the 2 region-specific instruments. We hypothesized that a strong positive relationship would exist between the generic and 2 region-specific instruments in an athletic population.     

Asymmetry Thresholds for Common Screening Tests and Their Effects on Jump Performance in Professional Soccer Players

ContextArbitrary asymmetry thresholds are regularly used in professional soccer athletes, notwithstanding the sparse literature available to examine their prevalence.ObjectiveTo establish normative and positional asymmetry values for commonly used screening tests and investigate their relationships with jumping performance.DesignCross-sectional study.SettingElite soccer screening.Patients or Other ParticipantsA total of 203 professional male soccer players.Main Outcome Measure(s)Bilateral and unilateral jumping; range of motion; and hamstrings (HAM), quadriceps (QUAD), and hip-adductor and -abductor strength tests were used to quantify asymmetry. Players were divided into 4 quartiles (Q1–Q4) based on the magnitude of their asymmetry for each test. Single composite scores were also developed to group tests by range of motion and HAM, QUAD, hip-adduction, and hip-abduction strength, and differences in jump performance were examined among players in each quartile.ResultsLarge variability (range = 5.2%–14.5%) was evident in asymmetry scores across the different tests and physical qualities. Forwards displayed greater asymmetry in concentric quadriceps and eccentric hip-abduction strength (P < .05). The HAM and QUAD composite scores indicated that Q4 players'' jumps were shorter than those in other quartiles during a single-legged countermovement jump and 10-second hop (P < .05). No decrements in unilateral jump performance were shown among players in each quartile for range of motion or hip-adduction and -abduction strength, and no composite measures of asymmetry affected bilateral jump performance.ConclusionsNo single asymmetry threshold was present for all tests; the outcomes were task, variable, and population specific. Larger asymmetries in HAM and QUAD strength appeared to be detrimental to unilateral jump performance.     

Recovery After High-Intensity Intermittent Exercise in Elite Soccer Players Using VEINOPLUS Sport Technology for Blood-Flow Stimulation

Context

Electric muscle stimulation has been suggested to enhance recovery after exhaustive exercise by inducing an increase in blood flow to the stimulated area. Previous studies have failed to support this hypothesis. We hypothesized that the lack of effect shown in previous studies could be attributed to the technique or device used.

Objective

To investigate the effectiveness of a recovery intervention using an electric blood-flow stimulator on anaerobic performance and muscle damage in professional soccer players after intermittent, exhaustive exercise.

Design

Randomized controlled clinical trial.

Setting

National Institute of Sport, Expertise, and Performance (INSEP).

Patients or Other Participants

Twenty-six healthy professional male soccer players.

Intervention(s)

The athletes performed an intermittent fatiguing exercise followed by a 1-hour recovery period, either passive or using an electric blood-flow stimulator (VEINOPLUS). Participants were randomly assigned to a group before the experiment started.

Main Outcome Measures(s)

Performances during a 30-second all-out exercise test, maximal vertical countermovement jump, and maximal voluntary contraction of the knee extensor muscles were measured at rest, immediately after the exercise, and 1 hour and 24 hours later. Muscle enzymes indicating muscle damage (creatine kinase, lactate dehydrogenase) and hematologic profiles were analyzed before and 1 hour and 24 hours after the intermittent fatigue exercise.

Results

The electric-stimulation group had better 30-second all-out performances at 1 hour after exercise (P = .03) in comparison with the passive-recovery group. However, no differences were observed in muscle damage markers, maximal vertical countermovement jump, or maximal voluntary contraction between groups (P > .05).

Conclusions

Compared with passive recovery, electric stimulation using this blood-flow stimulator improved anaerobic performance at 1 hour postintervention. No changes in muscle damage markers or maximal voluntary contraction were detected. These responses may be considered beneficial for athletes engaged in sports with successive rounds interspersed with short, passive recovery periods.Key Words: calf muscle, fatigue, athletes

Key Points

• After intermittent fatiguing exercise, these elite male soccer players showed better restoration of anaerobic performance with blood-flow stimulation than with passive recovery at 1 hour.
• Neither modality improved clearance of muscle damage markers or maximal voluntary contraction.

Rapid recovery of performance is important for elite athletes engaged in intermittent exercise that involves periods of intense exercise interspersed with short recovery periods (eg, martial arts, ice hockey, field sports). Optimizing training recovery may also be beneficial for performing successive bouts of training or competition over a season without associated fatigue or overtraining effects.The inability to repeat the same level of performance in short-duration exercise is frequently attributed to peripheral fatigue involving metabolite accumulation and muscle damage^1,2 resulting from mechanical stress, imbalances in muscle cell homeostasis, or local inflammation from exercise.³ Indeed, the response of different muscle enzymes (mainly creatine kinase [CK] and lactate dehydrogenase [LDH]) has received researchers'' attention because strenuous exercise induces muscle cell structural damage, which results in increased plasma concentrations of muscle enzymes such as CK and LDH.⁴ The efflux of CK and LDH proteins from muscle may be attributed to increased permeability of the plasma membrane or intramuscular vasculature (or both).⁵ Thus, a reduction in these markers has been proposed as an indicator of recovery after strenuous exercise that induces muscle damage.⁶ To optimize recovery, various techniques have been suggested to accelerate the clearance of muscular damage or metabolite accumulations. Usually, these techniques focus on local fatigue. Their main goal is to treat fatigue by directly applying the recovery method to the working muscles (eg, electromyostimulation, local cryotherapy, or cold-water immersion). This approach showed positive results after muscle damage by reducing local inflammation, especially when cold modalities were used.⁷ However, results on peripheral fatigue from metabolite accumulation are inconclusive, probably because the metabolic byproducts are released into the blood. From these findings, a change in the recovery approach from a local treatment to a systemic view was necessary. One possible way to achieve this goal is to improve the peripheral circulation and the venous return by stimulating total blood flow. In athletes, several techniques have been proposed to achieve this result. Of these, active recovery,^8,9 contrast water therapy,¹⁰ compression garments,¹¹ low-level laser therapy,¹² and low-frequency electromyostimulation¹³ have been investigated and compared with passive recovery (PAS).^6,14 The results of these studies provide no definitive consensus on the ability to improve explosive strength and anaerobic capacity performance or clear muscle damage markers after exercise.^15–17 Lattier et al¹⁸ showed no difference in neuromuscular function and maximal test performance after a recovery intervention using blood-flow stimulation from electromyostimulation compared with PAS or active recovery. Based on these observations, several authors concluded that the effects of these techniques are minimal, especially on performance. However, researchers^13,19 have hypothesized that this lack of effect could also be associated with the technique, the device used, or the localization of the electric stimulation (eg, systemic treatment [calf] versus local treatment [quadriceps]), suggesting that the blood flow and, more particularly, the venous return may not be effectively increased. Accordingly, Martin et al¹³ recommended optimizing the electric stimulation to better approximate the physiologic contraction of the muscle; a new way of using an electric muscle stimulator on the calf muscles could provide interesting results. This systemic approach is based on results showing that total blood flow can be efficiently stimulated by intensifying the pumping action associated with calf muscle contractions from techniques such as electromyostimulation, cuff inflation, or walking.²⁰ Indeed, these muscles, which have been termed the “peripheral venous heart,” “calf muscle pump,” and “musculovenous pump,” were responsible for 80% of the venous return^21–23 and considered a second heart. A low-intensity, repetitive mechanical contraction-relaxation muscle cycle may increase local and total blood flow, translocation, and removal of metabolites and reduce intracellular fluid volume.²⁴ However, using electric muscle stimulation to increase blood flow for exercise recovery has been ineffective despite the emergence of new devices that significantly improved total blood flow and venous return.^25–29 Therefore, we hypothesized that such a device applied to the calf muscles could result in faster restoration in performance and reduce the amount of muscle damage markers after fatiguing exercise.The purpose of our study was to investigate the effectiveness of muscle stimulation using the VEINOPLUS unit (Ad Rem Technology, Paris, France) on explosive strength and 30-second all-out performance and CK and LDH recovery profiles in professional soccer players after exhaustive intermittent exercise. We proposed that use of the VEINOPLUS would result in better restoration of anaerobic performance than passive recovery.     

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.     

Youth Soccer Parents’ Perceptions of Long-Term Effects of Concussion

ABSTRACT

Increased focus on sports-related concussion (SRC) in football in the media, and mandatory concussion education for parents of youth sport athletes, may result in parental concern that youth athletes will experience long-term effects from concussion. We sought to identify beliefs about long-term effects of concussion in parents of youth soccer athletes. Four hundred and eleven parents from soccer leagues in three states completed a survey assessing parents’ perceptions and knowledge of long-term effects of SRC. Nearly all youth soccer parents surveyed (96.5%) believe there are long-term effects from SRCs, 76% reported concern their child would sustain a concussion, and 71% had talked with their child about concussion symptoms/reporting. Parents ranked tackle football as having the highest risk for concussion, followed by soccer, ice hockey, cheerleading, and lacrosse. Parents of children that had previously sustained a concussion were 8.3x more likely to be concerned their child would sustain a concussion, and parents with a personal history of concussion were 2x more likely to consider not allowing their child to participate in youth sports. There are wide-spread beliefs among youth soccer parents regarding long-term effects of SRCs, and concerns their children will sustain concussions while participating in youth sports.     

The Effect of Visual and Sensory Performance on Head Impact Biomechanics in College Football Players

The development of prevention strategies is critical to address the rising prevalence of sport-related concussions. Visual and sensory performance may influence an individual’s ability to interpret environmental cues, anticipate opponents’ actions, and create appropriate motor responses limiting the severity of an impending head impact. The purpose of this study was to determine the relationship between traditional and visual sensory reaction time measures, and the association between visual and sensory performance and head impact severity in college football players. Thirty-eight collegiate football players participated in the study. We used real-time data collection instrumentation to record head impact biomechanics during games and practices. Our findings reveal no significant correlations between reaction time on traditional and visual sensory measures. We found a significant association between head impact severity and level of visual and sensory performance for multiple assessments, with low visual and sensory performers sustaining a higher number of severe head impacts. Our findings reveal a link between level of visual and sensory performance and head impact biomechanics. Future research will allow clinicians to have the most appropriate testing batteries to identify at-risk athletes and create interventions to decrease their risk of injurious head impacts.     

Age-Related,Sport-Specific Adaptions of the Shoulder Girdle in Elite Adolescent Tennis Players

Context:

Tennis requires repetitive overhead movements that can lead to upper extremity injury. The scapula and the shoulder play a vital role in injury-free playing. Scapular dysfunction and glenohumeral changes in strength and range of motion (ROM) have been associated with shoulder injury in the overhead athlete.

Objective:

To compare scapular position and strength and shoulder ROM and strength between Swedish elite tennis players of 3 age categories (<14, 14–16, and >16 years).

Design:

Cross-sectional study.

Setting:

Tennis training sports facilities.

Patients or Other Participants:

Fifty-nine adolescent Swedish elite tennis players (ages 10–20 years) selected based on their national ranking.

Main Outcome Measure(s):

We used a clinical screening protocol with a digital inclinometer and a handheld dynamometer to measure scapular upward rotation at several angles of arm elevation, isometric scapular muscle strength, glenohumeral ROM, and isometric rotator cuff strength.

Results:

Players older than 16 years showed less scapular upward rotation on the dominant side at 90° and 180° (P < .05). Although all absolute scapular muscle strength values increased with age, there was no change in the body-weight–normalized strength of the middle (P = .9) and lower (P = .81) trapezius or serratus anterior (P = .17). Glenohumeral internal-rotation ROM and total ROM tended to decrease, but this finding was not statistically significant (P = .052 and P = .06, respectively). Whereas normalized internal-rotator strength increased from 14 to 16 years to older than 16 years (P = .009), normalized external-rotator and supraspinatus strength remained unchanged.

Conclusions:

Age-related changes in shoulder and scapular strength and ROM were apparent in elite adolescent tennis players. Future authors should examine the association of these adaptations with performance data and injury incidence.Key Words: upper extremity, scapular position, scapular muscle strength, range of motion, rotator cuff strength

Key Points

• Elite adolescent tennis players showed some sport-specific adaptations in glenohumeral internal-rotation range of motion, rotator cuff strength, and scapular upward rotation.
• Sport-specific adaptations seemed to change within the 10- to 20-years-old age range.

The tennis serve uses rapid upper extremity movements to create high racket and ball speeds. Optimal upper extremity strength, flexibility, and neuromuscular coordination are necessary for attaining a high-velocity outcome.^1,2Due to the high loads and forces put on the shoulder complex during serving and hitting, tennis players are at increased risk for shoulder pain. Injury risk seems to increase with age^3,4 and, despite some lack of evidence, has been suggested to be related to the level and volume of play.^3–5 Shoulder injuries in overhead athletes are commonly due to repetitive use,⁶ muscle fatigue,⁷ and may be related to scapular dyskinesis,^8,9 rotator cuff injury and weakness,¹⁰ or glenohumeral internal-rotation deficit,^11,12 resulting in int ernal impingement or labral injury (or both).^13,14In high-performance sports, athletes start full-time practice in early childhood, which overlaps with the period of skeletal and muscular development.^15,16 As a result of the high demands on joint mobility, muscle strength, and complex biomechanics in the shoulder girdle during overhead sport movements, sport-specific adaptations at the glenohumeral and scapulothoracic level may occur even during adolescence.^4,8,17Numerous authors have reported glenohumeral^18,19 and scapulothoracic^20,21 alterations in adult overhead sport populations. In addition, changes in glenohumeral range of motion³ and rotator cuff strength¹⁷ have been described in elite junior tennis players. Only recently have some studies^4,8 been published describing the scapular position, strength, and flexibility variables in this young population. However, in these investigations, only general data were established for the whole period of adolescence. The specific age-related changes within adolescents (11–18 years) and the progression over time in this age category were not apparent. Moreover, even though the literature highlights the importance of the coupled movements at the shoulder and scapulothoracic joint for optimal kinematics during the tennis serve,¹ to date no authors have combined glenohumeral and scapulothoracic measurements in adolescent tennis players. Therefore, the purpose of our study was to describe the age-related, sport-specific adaptations in the shoulder girdle in adolescent elite tennis players: in particular, glenohumeral rotational range of motion and strength and scapular upward rotation and muscle strength.     

Different Exercise Training Interventions and Drop-Landing Biomechanics in High School Female Athletes

Context:

Anterior cruciate ligament (ACL) injuries are common in female athletes and are related to poor neuromuscular control. Comprehensive neuromuscular training has been shown to improve biomechanics; however, we do not know which component of neuromuscular training is most responsible for the changes.

Objective:

To assess the efficacy of either a 4-week core stability program or plyometric program in altering lower extremity and trunk biomechanics during a drop vertical jump (DVJ).

Design:

Cohort study.

Setting:

High school athletic fields and motion analysis laboratory.

Patients or Other Participants:

Twenty-three high school female athletes (age = 14.8 ± 0.8 years, height = 1.7 ± 0.07 m, mass = 57.7 ± 8.5 kg).

Intervention(s):

Independent variables were group (core stability, plyometric, control) and time (pretest, posttest). Participants performed 5 DVJs at pretest and posttest. Intervention participants engaged in a 4-week core stability or plyometric program.

Main Outcome Measure(s):

Dependent variables were 3-dimensional hip, knee, and trunk kinetics and kinematics during the landing phase of a DVJ. We calculated the group means and associated 95% confidence intervals for the first 25% of landing. Cohen d effect sizes with 95% confidence intervals were calculated for all differences.

Results:

We found within-group differences for lower extremity biomechanics for both intervention groups (P ≤ .05). The plyometric group decreased the knee-flexion and knee internal-rotation angles and the knee-flexion and knee-abduction moments. The core stability group decreased the knee-flexion and knee internal-rotation angles and the hip-flexion and hip internal-rotation moments. The control group decreased the knee external-rotation moment. All kinetic changes had a strong effect size (Cohen d > 0.80).

Conclusions:

Both programs resulted in biomechanical changes, suggesting that both types of exercises are warranted for ACL injury prevention and should be implemented by trained professionals.Key Words: anterior cruciate ligament, plyometrics, core stability

Key Points

• Kinematic and kinetic changes occurred in high school female athletes after an in-season, 4-week training program of core stability and plyometric exercises.
• The plyometric group demonstrated changes only at the knee joint, but the core stability group demonstrated changes in kinetics at the hip joint and kinematics at the knee joint.
• Core stability and plyometric exercises are warranted in programs designed to prevent anterior cruciate ligament injury because they contribute different biomechanical adaptations.

The rate of noncontact anterior cruciate ligament (ACL) injury is more than 3 times higher in adult and adolescent females than in their male counterparts.¹ Noncontact ACL injuries commonly occur during dynamic activities when the individual is decelerating, such as landing from a jump or changing direction.² Kinematic patterns thought to be associated with greater risk for injury include landing in an extended posture through the knee, hip, and trunk, resulting in increased shear force on the ACL.^3,4 Frontal- and transverse-plane movements, including increased knee abduction and internal rotation and decreased hip abduction, also are thought to place rotational force on the static stabilizer.^5–9A link between ACL injury and proximal lower extremity and trunk neuromuscular control has been established. Hewett et al⁶ found that individuals who sustained an ACL injury had larger external knee-abduction moments that were correlated with the hip-adduction moment. In addition, females who had greater lateral trunk displacement in response to a sudden force were more likely to incur an ACL injury.⁹ These results suggest that the risk for noncontact ACL injury may be related to forces at the knee affected by decreased neuromuscular control at the hip and trunk.Biomechanical and neuromuscular control patterns have been shown to be modifiable in response to training.^5,10,11 Training programs that have resulted in favorable changes to biomechanical patterns have involved a broad approach, incorporating balance, lower extremity strength, plyometric, and agility components to address all aspects of neuromuscular control.^7,8,10,11 These comprehensive programs often involve lengthy training sessions and may require equipment that is not always easily accessible for group training purposes. Furthermore, we do not know whether all components of comprehensive training programs are effective or necessary in altering biomechanical patterns. The variety and volume of the components included in an intervention program possibly can be reduced to make it more manageable to incorporate in various athletic settings. Researchers^12,13 have investigated the contributions of specific muscles during commonly prescribed lower extremity and trunk exercises; however, little information exists about how a group of exercises affects lower extremity and trunk biomechanics during a dynamic landing task. In 1 study,¹⁴ 9 weeks of lower extremity strength training did not result in any lower extremity biomechanical changes despite an increase in strength. In contrast, researchers¹⁰ who compared traditional strength training and plyometric training found similar changes in kinematic and kinetic variables for both groups. By gaining a better understanding of how individual components effectively alter neuromuscular patterns, clinicians may be able to develop more effective and efficient injury-prevention programs.Therefore, the purpose of our study was to assess the efficacy of either a 4-week core stability program or plyometric program in altering lower extremity and trunk biomechanics during a drop vertical jump (DVJ). We hypothesized that (1) the plyometric group would decrease lateral trunk-flexion, hip-adduction, hip internal-rotation, knee-abduction, and knee internal-rotation angles; (2) the plyometric group would increase hip- and knee-flexion angles; (3) the plyometric group would decrease their external flexion, abduction, and external-rotation moments at the hip; (4) the plyometric group would decrease their external flexion, abduction, and internal-rotation moments at the knee; (5) the core stability group would decrease lateral trunk-flexion, hip internal-rotation and adduction angles and external joint moments; and (6) the control group would not show changes in kinematic or kinetic variables.     

跑者足部形态与足趾及跖趾关节屈肌力量的相关性

目的 探究坐姿及站姿下跑者足部形态与足趾屈曲力量和跖趾关节屈肌力量的相关性.方法 选取26名男性跑者,采用数显游标卡尺、跖趾关节屈肌力量测试仪、屈曲力量计测量足长、截脚长、足宽、足舟骨高度、50％足长处足背高度、跖趾关节屈肌力量、第1和其余四趾屈曲力量.使用偏相关分析足部形态与足部肌力的相关性.结果 校正年龄与身体质量...     

Red Light and the Sleep Quality and Endurance Performance of Chinese Female Basketball Players

Context

Good sleep is an important recovery method for prevention and treatment of overtraining in sport practice. Whether sleep is regulated by melatonin after red-light irradiation in athletes is unknown.

Objective

To determine the effect of red light on sleep quality and endurance performance of Chinese female basketball players.

Design

Cohort study.

Setting

Athletic training facility of the Chinese People''s Liberation Army and research laboratory of the China Institute of Sport Science.

Patients or Other Participants

Twenty athletes of the Chinese People''s Liberation Army team (age = 18.60 ± 3.60 years) took part in the study. Participants were divided into red-light treatment (n = 10) and placebo (n = 10) groups.

Intervention(s)

The red-light treatment participants received 30 minutes of irradiation from a red-light therapy instrument every night for 14 days. The placebo group did not receive light illumination.

Main Outcome Measure(s)

The Pittsburgh Sleep Quality Index (PSQI) questionnaire was completed, serum melatonin was assessed, and 12-minute run was performed at preintervention (baseline) and postintervention (14 days).

Results

The 14-day whole-body irradiation with red-light treatment improved the sleep, serum melatonin level, and endurance performance of the elite female basketball players (P < .05). We found a correlation between changes in global Pittsburgh Sleep Quality Index and serum melatonin levels (r = −0.695, P = .006).

Conclusions

Our study confirmed the effectiveness of body irradiation with red light in improving the quality of sleep of elite female basketball players and offered a nonpharmacologic and noninvasive therapy to prevent sleep disorders after training.Key Words: Pittsburgh Sleep Quality Index, melatonin, 12-minute run

Key Points

• Red-light illumination positively affected sleep quality and endurance performance variables in Chinese female basketball players.
• Red-light illumination is a positive nonpharmacologic and noninvasive therapy to prevent sleep disorders after training.

Good sleep is a prerequisite for optimal performance.¹ Given that people spend about one-third of their lives asleep, sleep has substantial functions for development, daily functioning, and health.² Perhaps no daytime behavior has been associated more closely with improved sleep than exercise.³ Researchers have shown that exercise serves as a positive function for sleep. Regular exercise consistently has been associated with better sleep.⁴ Moreover, the American Academy of Sleep Medicine considers physical exercise to be a modality of nonpharmacologic treatment for sleep disorders.⁴ When studying the influence of exercise on sleep, most investigators have compared acute exercise and sedentary control treatments.⁵ In their study of chronic moderate-intensity endurance exercise, Driver and Taylor⁶ also provided compelling evidence that exercise promotes sleep.However, exercise can negatively affect sleep quality. Exercising immediately before going to sleep is detrimental to sleep quality.⁷ Athletes train very hard to improve their on-field performances, but excessive training may lead to a decrease in performance, which is known as overtraining syndrome. Researchers⁸ have shown that symptoms of overtraining indicate poor-quality sleep. Good sleep is an important recovery method for prevention and treatment of overtraining in sport practice.⁹Evidence is compelling that chronic exposure to bright light (3000 lux) can enhance sleep.¹⁰ Guilleminault et al¹¹ suggested that the effects of exposure to light may be more powerful than those associated with exercise. In a recent study in which red-light therapy (wavelength = 670 nm, light dose = 4 J/cm²) was used, Yeager et al¹² indicated that red light could restore glutathione redox balance upon toxicologic insult and enhance both cytochrome c oxidase and energy production, all of which may be affected by melatonin. Melatonin is a neurohormone that is produced by the pineal gland and regulates sleep and circadian functions.¹³ No one knows whether sleep is regulated by melatonin after red-light irradiation in athletes. Researchers^14,15 have demonstrated that phototherapy improves muscle regeneration after exercise. Red light could protect human erythrocytes in preserved diluted whole blood from the damage caused by experimental artificial heart-lung machines.¹⁶ However, the effect of red-light illumination on endurance performance is a new topic in sport science.Sleep quality can be defined subjectively by self-report¹⁷ or by more objective measures, such as polysomnography or actigraphy.¹⁸ Subjective sleep quality has been assessed most widely with the Pittsburgh Sleep Quality Index (PSQI).¹⁷ The PSQI is a comprehensive 18-item self-report questionnaire assessing sleep disturbances in the previous month. It derives ordinal scores for 7 clinically relevant domains of sleep: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances (eg, awakenings from sleep due to discomfort, bad dreams), use of sleeping medication, and daytime dysfunction (feeling sleepy during the day due to a poor night''s sleep). Scores from these separate components are combined to derive a global measure of sleep quality.¹⁹As demonstrated in these studies, acute or chronic exercise may lead to good- or bad-quality sleep. However, the effects of red light on sleep quality and endurance performance have not been investigated sufficiently. Therefore, the purpose of our study was to determine the effect of red light on the sleep quality and endurance performance of Chinese female basketball players.     

Association Between Knee- and Hip-Extensor Strength and Running-Related Injury Biomechanics in Collegiate Distance Runners

ContextRunning-related injuries are common in distance runners. Strength training is used for performance enhancement and injury prevention. However, the association between maximal strength and distance-running biomechanics is unclear.ObjectiveTo determine the relationship between maximal knee- and hip-extensor strength and running biomechanics previously associated with injury risk.DesignCross-sectional study.SettingResearch laboratory.Patients or Other ParticipantsA total of 36 collegiate distance runners (26 men, 10 women; age = 20.0 ± 1.5 years, height = 1.74 ± 0.09 m, mass = 61.97 ± 8.26 kg).Main Outcome Measure(s)Strength was assessed using the 1-repetition maximum (1RM) back squat and maximal voluntary isometric contractions of the knee extensors and hip extensors. Three-dimensional running biomechanics were assessed overground at a self-selected speed. Running variables were the peak instantaneous vertical loading rate; peak forward trunk-lean angle; knee-flexion, internal-rotation, and -abduction angles and internal moments; and hip-extension, internal-rotation, and -adduction angles and internal moments. Separate stepwise linear regression models were used to examine the associations between strength and biomechanical outcomes (ΔR²) after accounting for sex, running speed, and foot-strike index.ResultsGreater 1RM back-squat strength was associated with a larger peak knee-flexion angle (ΔR² = 0.110, ΔP = .045) and smaller peak knee internal-rotation angle (ΔR² = 0.127, ΔP = .03) and internal-rotation moment (ΔR² = 0.129, ΔP = .03) after accounting for sex, speed, and foot-strike index. No associations were found between 1RM back-squat strength and vertical loading rate, trunk lean, or hip kinematics and kinetics. Hip- and knee-extensor maximal voluntary isometric contractions were also not associated with any biomechanical variables.ConclusionsGreater 1RM back-squat strength was weakly associated with a larger peak knee-flexion angle and smaller knee internal-rotation angle and moment in collegiate distance runners. Runners who are weaker in the back-squat exercise may exhibit running biomechanics associated with the development of knee-related injuries.     

An 8-Year Longitudinal Study of Overreaching in 114 Elite Female Chinese Wrestlers

Context:Successful training involves structured overload but must avoid the combination of excessive overload and inadequate recovery.Objective:The aim of this study was to determine the incidence of functional overreaching (FOR), nonfunctional overreaching (NFOR), and overtraining syndrome in elite female wrestlers during their normal training and competition schedules and to explore the utility of blood markers for the early detection of overreaching. Classification of FOR, NFOR, and overtraining syndrome was based on the European Congress of Sports Medicine position statement.Design:Case series.Setting:China Institute of Sport Science.Results:Among the 114 athletes, there were 13 (3.6%) instances of FOR, 23 (6.4%) instances of NFOR, and 2 (0.6%) instances of overtraining syndrome. The diagnostic sensitivity for FOR was 38%, 15%, 45%, and 18% for creatine kinase, hemoglobin, testosterone, and cortisol, respectively. The diagnostic sensitivity for NFOR was 29%, 33%, 26%, and 35% for creatine kinase, hemoglobin, testosterone, and cortisol, respectively. Specificity was 79%, 88%, 90%, and 82% for creatine kinase, hemoglobin, testosterone, and cortisol, respectively. Post hoc analysis showed no mean differences in creatine kinase (F = 0.5, P = .47), hemoglobin (F = 3.8, P = .052), testosterone (F = 0.2, P = .62), or cortisol (F = 0.04, P = .85) between monitoring periods when wrestlers were and were not diagnosed with FOR and NFOR.Conclusions:Coaches and sports scientists should not use single blood variables as markers of overreaching in elite female wrestlers.Key Words: blood markers, fatigue, overtraining, underperformance

Key Points

• The incidence of overtraining was high (69%) in world-class female wrestlers.
• The blood variables creatine kinase, hemoglobin, testosterone, and cortisol were not useful markers for the early detection of overreaching.

An imbalance between training stress and recovery is known as overtraining and can result in functional overreaching (FOR), nonfunctional overreaching (NFOR), and overtraining syndrome (OTS).^1,2 Functional overreaching is considered a desirable component of training for elite athletes because of the relatively short recovery time (within 2 weeks) and the associated supercompensatory effect that elicits improved athletic performance.³ In contrast, recovery from NFOR may take several weeks to months and hence has a negative effect on athletes'' training programs. Furthermore, recovery from OTS may take months to years and is characterized by a prolonged decrease in performance, persistent fatigue, and mood disturbances, all of which seriously compromise the competitive athlete.^2,4 The incidence of NFOR and OTS has been estimated to be in the range of 5% to 60% of all athletes during their sports career.^5–9 Therefore, this problem continually needs to be addressed by coaches and scientific support staff. The process of intensified training leading to FOR, NFOR, and OTS is often viewed as a continuum, and the thresholds between these 3 states are extremely narrow. Thus, athletes and coaches need accurate and reliable diagnostic tools to identify overtraining so that timely recovery interventions can be implemented to avoid the negative consequences associated with NFOR and OTS.In the last few decades, considerable research has indicated that FOR, NFOR, and OTS may be identified using diagnostic blood markers,^10–18 physiologic perturbations,^11,16,19,20 and negative changes in the athlete''s psychological state.^{14,16,18,21–23} Most authors who have investigated the early signs of overtraining have relied on deliberately inducing a state of overreaching by exposing athletes to short periods of intensified training.^{10,13,20–23} Such studies, however, rarely reflect the normal training and competition schedules of elite athletes, are difficult to conduct, and raise a variety of ethical concerns. Cross-sectional studies focusing on diagnostic markers of NFOR and OTS generally include athletes from sports medicine clinics in which athletes experiencing OTS are highly represented.^17,18 Unfortunately, such investigations do not reveal any information about the incidence of FOR, NFOR, and OTS during the athletes'' normal training and competition schedules. These studies also do not provide information on the development of FOR and NFOR because they focus on the end stages of the overtraining continuum. Few authors of longitudinal studies have attempted to document the incidence of NFOR and identify early markers of FOR and NFOR within a naturalistic sports setting, and, to the best of our knowledge, no studies have investigated overreaching in elite wrestlers.The main aim of our study was to report the incidence of FOR, NFOR, and OTS in elite female wrestlers, using a longitudinal 8-year observation of the Chinese women''s wrestling team during their normal training and competition schedules. A second aim was to explore the utility of blood markers for the early detection of overreaching.     

Sex-Related and Age-Related Differences in Knee Strength of Basketball Players Ages 11-17 Years

OBJECTIVE: To assess hamstrings and quadriceps strength of basketball players ages 11-13 and 15-17 years. DESIGN AND SETTING: This cross-sectional study occurred during the 2000 American Youth Basketball Tour National Tournament. We investigated whether sex- or age-related strength differences existed among study participants. SUBJECTS: Forty-one tournament participants (22 girls, 19 boys; 11-13 or 15-17 years old) who reported no history of knee sprain or surgery were recruited. MEASUREMENTS: We used a Cybex II dynamometer to obtain isokinetic concentric peak torques relative to body mass (Nm/kg) at 60 degrees /s for hamstrings and quadriceps bilaterally. From average peak torques, we determined ipsilateral hamstrings:quadriceps and homologous muscle-group ratios. RESULTS: Correlations between hamstrings and quadriceps strength measures ranged from 0.78 to 0.97. Players 15-17 years old had greater relative hamstrings and quadriceps strength than 11- to 13-year-old athletes. Age and sex interacted significantly for quadriceps strength. The quadriceps strength of 15- to 17-year-old girls did not differ from that of 11- to 13-year-old girls, whereas 15- to 17-year-old boys had stronger quadriceps than 11- to 13-year-old boys. Boys 15-17 years old had greater quadriceps strength than girls 15-17 years old. CONCLUSIONS: This study is unique in providing normative data for the hamstrings and quadriceps strength of basketball players 11-13 and 15-17 years old. Age-related strength differences did not occur consistently between the sexes, as girls 11-13 and 15-17 years old had similar relative quadriceps strength.     

Helmet Fit Assessment and Concussion Risk in Youth Ice Hockey Players: A Nested Case-Control Study

ContextInjury surveillance has shown that concussions are the most common injury in youth ice hockey. Research examining the criteria for ensuring the correct fit of protective equipment and its potential relationship with concussion risk is very limited.ObjectiveTo evaluate the association between helmet fit and the odds of experiencing a concussion among youth ice hockey players.DesignNested case-control within a cohort study.SettingCalgary, Alberta, Canada.Patients or Other ParticipantsData were collected for 72 concussed, 41 nonconcussion-injured, and 62 uninjured ice hockey players aged 11 to 18 years.Main Outcome Measure(s)Helmet-fit assessments were conducted across players and encompassed helmet specifications, condition, certification, and criteria measuring helmet fit. Using a validated injury-surveillance system, we identified participants as players with suspected concussions or physician-diagnosed concussions or both. One control group comprised players who sustained nonconcussion injuries, and a second control group comprised uninjured players. Helmet-fit criteria (maximum score = 16) were assessed for the concussed players and compared with each of the 2 control groups. The primary outcome was dichotomous (>1 helmet-fit criteria missing versus 0 or 1 criterion missing). Logistic and conditional logistic regression were used to investigate the effect of helmet fit on the odds of concussion.ResultsThe primary analysis (54 pairs matched for age, sex, and level of play) suggested that inadequate helmet fit (>1 criterion missing) resulted in greater odds of sustaining a concussion when comparing concussed and uninjured players (odds ratio [OR] = 2.67 [95% CI = 1.04, 6.81], P = .040). However, a secondary unmatched analysis involving all participants indicated no significant association between helmet fit and the odds of sustaining a concussion when we compared concussed players with nonconcussion-injured players (OR = 0.98 [0.43, 2.24], P = .961) or uninjured players (OR = 1.66 [0.90, 3.05], P = .103).ConclusionsInadequate helmet fit may affect the odds of sustaining a concussion in youth ice hockey players. Future investigators should continue to evaluate this relationship in larger samples to inform helmet-fit recommendations.     

Head Impact Biomechanics in Youth Hockey: Comparisons Across Playing Position, Event Types, and Impact Locations

The age at which young hockey players should safely body check is unknown. We sought to determine if playing position (defensemen vs. forwards), event type (practice vs. game), or head impact location (top vs. back vs. front vs. sides) had an effect on head impact biomechanics in youth hockey. A total of 52 Bantam (13–14 years old) and Midget (15–16 years old) ice hockey players wore accelerometer-instrumented helmets for two seasons. Biomechanical data were captured for 12,253 head impacts during 151 games and 137 practices. Random intercepts general mixed linear models were employed to analyze differences in linear acceleration, rotational acceleration, and HITsp by player position, event type, and head impact location. Head impacts sustained during games resulted in greater rotational acceleration and HITsp than those sustained during practices. No event type or playing position differences in linear acceleration were observed. Impacts to the top of the head resulted in greater linear acceleration, but lower rotational acceleration and HITsp, than impacts to back, front, or side of the head. Side head impacts yielded greater rotational acceleration and HITsp compared to the other head impact locations. Since linear and rotational accelerations were observed in all impacts, future hockey helmet design standards should include rotational acceleration limits in addition to the current linear acceleration standards.     

Thigh Muscle Activity,Knee Motion,and Impact Force During Side-Step Pivoting in Agility-Trained Female Basketball Players

Context:

Improving neuromuscular control of hamstrings muscles might have implications for decreasing anterior cruciate ligament injuries in females.

Objective:

To examine the effects of a 6-week agility training program on quadriceps and hamstrings muscle activation, knee flexion angles, and peak vertical ground reaction force.

Design:

Prospective, randomized clinical research trial.

Setting:

Sports medicine research laboratory.

Patients or Other Participants:

Thirty female intramural basketball players with no history of knee injury (age  =  21.07 ± 2.82 years, height  =  171.27 ± 4.66 cm, mass  =  66.36 ± 7.41 kg).

Intervention(s):

Participants were assigned to an agility training group or a control group that did not participate in agility training. Participants in the agility training group trained 4 times per week for 6 weeks.

Main Outcome Measure(s):

We used surface electromyography to assess muscle activation for the rectus femoris, vastus medialis oblique, medial hamstrings, and lateral hamstrings for 50 milliseconds before initial ground contact and while the foot was in contact with the ground during a side-step pivot maneuver. Knee flexion angles (at initial ground contact, maximum knee flexion, knee flexion displacement) and peak vertical ground reaction force also were assessed during this maneuver.

Results:

Participants in the training group increased medial hamstrings activation during ground contact after the 6-week agility training program. Both groups decreased their vastus medialis oblique muscle activation during ground contact. Knee flexion angles and peak vertical ground reaction force did not change for either group.

Conclusions:

Agility training improved medial hamstrings activity in female intramural basketball players during a side-step pivot maneuver. Agility training that improves hamstrings activity might have implications for reducing anterior cruciate ligament sprain injury associated with side-step pivots.