Adolescent and Parent Perceptions of the Impact of Concussion/mTBI on Family Functioning and Activity Levels in Recovery.

OBJECTIVE: To explore adolescent and parent perceptions of the impact of a concussion/mild traumatic brain injury (mTBI) on family functioning and activity levels in the first 4 weeks of recovery. SETTING: Outpatient research setting. PARTICIPANTS: Twenty-seven adolescents (aged of 13-17 years) within 1 week of a concussion/mTBI and a parent/guardian were enrolled in the study. DESIGN: Prospective ecological study with qualitative, semistructured interviews. MAIN MEASURES: Adolescents reported symptoms electronically every 2 days for 28 days via the Post-Concussion Symptom Inventory. Semistructured interviews were completed with each adolescent-parent dyad at the end of the 28-day period. Interview questions focused on perceptions of recovery progress and study procedures. RESULTS: Symptom trajectories were variable across participants. Three main themes emerged from thematic analysis, including: (1) disruption of routines and activities, (2) injury management considerations, and (3) positive and negative influential factors (eg, school and coach support, timing of injury, and recovery expectations). Results highlighted nuances of recovery challenges that families specifically face and help emphasize the potential benefits of shared decision-making and where more guidance would be appreciated such as more specific self-management of symptoms and physical activity reintegration strategies. CONCLUSIONS: Study findings support a shared decision-making approach with the identified themes as potential topics to help consider social and environmental influences on recovery. The themes presented in the results could be topics emphasized during intake and follow-up visit processes to help guide plans of care and return-to-activity decisions.

An Exploration of the Impact of Initial Timing of Physical Therapy on Safety and Outcomes After Concussion in Adolescents.

BACKGROUND AND PURPOSE: Physical therapy (PT) is a management strategy increasingly recognized to facilitate recovery after concussion. The purpose of this study was to investigate the safety and outcomes of multimodal impairment-based PT at varying time points after injury in youth diagnosed with concussion. METHODS: Data were extracted retrospectively from medical records for patients who received PT for concussion-related impairments. Patient records were categorized into 3 cohorts on the basis of the timing of PT implementation: 0-20 days following injury (early intervention), 21 to 41 days following injury (middle intervention), and 42 or more days following injury (late intervention). The primary outcome measure was Post-Concussion Symptom Inventory score from the beginning to the end of the PT episode of care. Additional outcome measures included number of PT sessions, duration of PT episode of care (days), and occurrence of unplanned visits to a health care provider. RESULTS: A total of 120 patient records (mean age of 14.77 years) were analyzed. Thirty-three, 39, and 48 individuals were categorized into the early, middle, and late intervention cohorts, respectively. There were no significant differences between intervention cohorts with regard to symptom change on the Post-Concussion Symptom Inventory from the beginning to the end of the PT episode of care, unplanned health care visits, number of PT sessions, or duration of PT episode of care. DISCUSSION AND CONCLUSIONS: Early initiation of PT may be safe and tolerable. Future prospective studies are needed to explore the efficacy of PT services administered early following injury to help characterize an optimal care plan for youth following concussion.Video Abstract available for more insights from the authors (see Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A210).

Exertional Tolerance Assessments After Mild Traumatic Brain Injury: A Systematic Review.

OBJECTIVE: To review the literature to identify and summarize strategies for evaluating responses to physical exertion after mild traumatic brain injury (mTBI) for clinical and research purposes. DATA SOURCES: PubMed and EBSCOhost through December 31, 2016. STUDY SELECTION: Two independent reviewers selected studies based on the following criteria: (1) inclusion of participants with mTBI/concussion, (2) use of a measurement of physiological or psychosomatic response to exertion, (3) a repeatable description of the exertion protocol was provided, (4) a sample of at least 10 participants with a mean age between 8 and 65 years, and (5) the article was in English. The search process yielded 2685 articles, of which 14 studies met the eligibility requirements. DATA EXTRACTION: A quality assessment using a checklist was conducted for each study by 2 independent study team members and verified by a third team member. Data were extracted by one team member and verified by a second team member. DATA SYNTHESIS: A qualitative synthesis of the studies revealed that most protocols used a treadmill or cycle ergometer as the exercise modality. Protocol methods varied across studies including differences in initial intensity determination, progression parameters, and exertion duration. Common outcome measures were self-reported symptoms, heart rate, and blood pressure. CONCLUSIONS: The strongest evidence indicates that exertional assessments can provide important insight about mTBI recovery and should be administered using symptoms as a guide. Additional studies are needed to verify optimal modes and protocols for post-mTBI exertional assessments.

Structural Connectivity Related to Persistent Symptoms After Mild TBI in Adolescents and Response to Aerobic Training: Preliminary Investigation.

OBJECTIVE: To quantify structural connectivity abnormalities in adolescents with mild traumatic brain injury (mTBI) and to investigate connectivity changes following aerobic training using graph theory and diffusion tensor imaging tractography. SETTING: Outpatient research setting. PARTICIPANTS: Twenty-two children (age: 15.83 ± 1.77 years, 10 females) with 4 to 16 weeks of persistent symptoms after mTBI and a matched healthy comparison group. DESIGN: Randomized clinical trial of aerobic training and stretching comparison combined with case-control comparison. MAIN MEASURES: (1) Five global network measures: global efficiency (Eglob), mean local efficiency, modularity, normalized clustering coefficient (γ), normalized characteristic path length (λ), and small-worldness (σ). (2) The self-reported Post-Concussion Symptom Inventory score. RESULTS: At initial enrollment, adolescents with mTBI had significantly lower Eglob and higher γ, λ, and σ (all P < .05) than healthy peers. After the intervention, significantly increased Eglob and decreased λ (both P < .05) were found in the aerobic training group. Improvement in Post-Concussion Symptom Inventory scores was significantly correlated with the Eglob increase and λ decrease in the aerobic training and λ decrease in the stretching comparison group (all P < .05). CONCLUSION: This pilot study showed initial evidence that structural connectivity analysis was sensitive to brain network abnormalities and may serve as an imaging biomarker in children with persistent symptoms after mTBI.

Aerobic Exercise for Adolescents With Prolonged Symptoms After Mild Traumatic Brain Injury: An Exploratory Randomized Clinical Trial.

OBJECTIVE: To describe the methodology and report primary outcomes of an exploratory randomized clinical trial (RCT) of aerobic training for management of prolonged symptoms after a mild traumatic brain injury (mTBI) in adolescents. SETTING: Outpatient research setting. PARTICIPANTS: Thirty adolescents between the ages of 12 and 17 years who sustained a mTBI and had between 4 and 16 weeks of persistent symptoms. DESIGN: Partially blinded, pilot RCT of subsymptom exacerbation aerobic training compared with a full-body stretching program. MAIN MEASURES: The primary outcome was postinjury symptom improvement assessed by the adolescent's self-reported Post-Concussion Symptom Inventory (PCSI) repeated for at least 6 weeks of the intervention. Parent-reported PCSI and adherence are also described. RESULTS: Twenty-two percent of eligible participants enrolled in the trial. Repeated-measures analysis of variance via mixed-models analysis demonstrated a significant group × time interaction with self-reported PCSI ratings, indicating a greater rate of improvement in the subsymptom exacerbation aerobic training group than in the full-body stretching group (F = 4.11, P = .044). Adherence to the home exercise programs was lower in the subsymptom exacerbation aerobic training group compared with the full-body stretching group (mean [SD] times per week = 4.42 [1.95] vs 5.85 [1.37], P < .0001) over the duration of the study. CONCLUSION: Findings from this exploratory RCT suggest subsymptom exacerbation aerobic training is potentially beneficial for adolescents with persistent symptoms after an mTBI. These findings and other recent research support the potential benefit of active rehabilitation programs for adolescents with persistent symptoms after an mTBI. Larger replication studies are needed to verify findings and improve generalizability. Future work should focus on determining the optimal type, timing, and intensity of active rehabilitation programs and characteristics of individuals most likely to benefit.

Influence of Age on Postconcussive Postural Control Measures and Future Implications for Assessment.

OBJECTIVE: To examine the influence of age, sex, attention-deficit hyperactivity disorder (ADHD) status, previous history of concussion, and days since injury on postconcussion postural control assessment in adolescents who have suffered a concussion. DESIGN: Prospective cohort study. SETTING: Hospital-based outpatient clinic. PARTICIPANTS: Seventy-one participants (42 males; 29 females) with mean age 14.14 ± 2.44. INDEPENDENT VARIABLES: Age, sex, previous concussion history, ADHD status, total and severity of postconcussion symptoms, and days since injury. MAIN OUTCOME MEASURES: Total Balance Error Scoring System score, path length, center-of-pressure (COP) area, sample entropy, and Romberg quotient. RESULTS: Pearson product-moment correlation coefficients were calculated to test for potential associations between the continuous participant characteristics and the postural control variables. Spearman correlation was used to test the association between symptom severity and the postural control variables. Standard multiple regression was used to model the extent to which participant characteristics accounted for the variance in the postural sway variables. Age was significantly associated with all of the postural sway variables except COP area for the eyes open condition and sample entropy in the anterior-posterior direction for the eyes closed condition. Sex, ADHD status, and previous concussion history did not significantly predict postural control scores. CONCLUSIONS: Age significantly influences scores on common postconcussion postural control assessments. CLINICAL RELEVANCE: This study demonstrates that age is a critical factor that needs to be accounted for to improve the clinical appropriateness and utility of current postconcussion postural control assessments.

Postconcussion Postural Sway Variability Changes in Youth: The Benefit of Structural Variability Analyses.

PURPOSE: The purpose of this study was to evaluate the utility of postural sway variability as a potential assessment to detect altered postural sway in youth with symptoms related to a concussion. METHODS: Forty participants (20 who were healthy and 20 who were injured) aged 10 to 16 years were assessed using the Balance Error Scoring System (BESS) and postural sway variability analyses applied to center-of-pressure data captured using a force plate. RESULTS: Significant differences were observed between the 2 groups for postural sway variability metrics but not for the BESS. Specifically, path length was shorter and Sample and Renyi Entropies were more regular for the participants who were injured compared with the participants who were healthy (P < .05). CONCLUSION: The results of this study indicate that postural sway variability may be a more valid measure than the BESS to detect postconcussion alterations in postural control in young athletes.

The utility of the balance error scoring system for mild brain injury assessments in children and adolescents.

The Balance Error Scoring System (BESS) is widely recognized as an acceptable assessment of postural control for adult patients following a mild traumatic brain injury (mTBI) or concussion. However, the measurement properties of the BESS as a post-mTBI assessment test for younger patients are not well understood. The purpose of this study was to evaluate the utility of the BESS as a post-mTBI assessment test for children and adolescents aged 8 to 18 years through 2 investigations: (1) a retrospective medical records review of the relationship among age, BESS scores, and other common post-mTBI assessment tests; and (2) a prospective study comparing BESS scores for a cohort of children with a recent mTBI and BESS scores for a cohort of matched healthy peers. Age was found to be significantly correlated with several of the BESS measures and the total BESS score (P < 0.05). Significant differences were observed between the injured and healthy cohorts for 3 of the BESS measures and the total BESS score. However, the observed differences were not likely to be clinically meaningful. Cumulatively, evidence from the literature and the results of these studies indicate that the BESS may be limited for producing accurate assessments of younger athletes' post-mTBI postural control abilities. Future research recommendations include testing of modified versions of the BESS or other alternatives for post-mTBI postural control assessments with younger individuals.

Reduced 2-D Frontal Plane Motion During Single-Limb Landing Is Associated With Risk of Future Anterior Cruciate Ligament Graft Rupture After Anterior Cruciate Ligament Reconstruction and Return to Sport: A Pilot Study.

OBJECTIVES: To evaluate the association between 2-D frontal plane movement and second anterior cruciate ligament (ACL) injury risk in young athletes at return to sport (RTS) after ACL reconstruction. DESIGN: Prospective cohort. METHODS: Forty-nine participants who had ACL reconstruction (mean ± SD age, 16.5 ± 3.0 years) performed a single-leg drop landing from a 31-cm box at the time of their RTS. Frontal plane trunk, pelvis, and knee angles were measured using 2-D video analysis at the point of maximum depth during landing. Summated frontal plane angles were calculated by adding trunk, pelvis, and knee angles. Participants were grouped based on whether or not they sustained an ACL graft rupture over the 24 months after RTS. RESULTS: Seven participants (14%) sustained an ipsilateral graft rupture within 24 months after RTS. Participants who suffered a second ACL injury had a significant reduction in the summated frontal plane angle of the trunk, pelvis, and knee (P = .018) and of the trunk and knee (P = .02) compared to those who did not suffer a second injury. For every 5° increase in the summated trunk, pelvis, and knee angle (odds ratio [OR] = 0.54; 95% confidence interval [CI]: 0.31, 0.94) and the summated trunk and knee angle (OR = 0.48; 95% CI: 0.25, 0.94), the athletes were 46% to 52% less likely to sustain a graft rupture. CONCLUSION: Athletes who suffered an ACL graft rupture within 24 months of RTS had a more rigid posture when landing compared to their uninjured peers. The results of this pilot study should be replicated in a larger sample to determine whether this method has merit as a screening tool to identify athletes at high risk for second ACL injury. J Orthop Sports Phys Ther 2021;51(2):82-87. Epub 25 Dec 2020. doi:10.2519/jospt.2021.9302.

Neurocognitive and Quality of Life Improvements Associated With Aerobic Training for Individuals With Persistent Symptoms After Mild Traumatic Brain Injury: Secondary Outcome Analysis of a Pilot Randomized Clinical Trial.

Objective: To report secondary neurocognitive and quality of life outcomes for a pilot randomized clinical trial (RCT) of aerobic training for management of prolonged symptoms after a mild traumatic brain injury (mTBI) in adolescents. Setting: Outpatient research setting. Participants: Thirty adolescents between the ages of 12 and 17 years who sustained a mTBI and had between 4 and 16 weeks of persistent post-concussive symptoms. Design: Secondary outcome analysis of a partially masked RCT of sub-symptom exacerbation aerobic training compared with a full-body stretching program highlighting cognitive and quality of life outcomes. Main Measures: The secondary outcomes assessed included neurocognitive changes in fluid and crystallized age-adjusted cognition using the National Institutes of Health (NIH) toolbox and self and parent-reported total quality of life using the Pediatric Quality of Life Inventory. Results: Twenty-two percent of eligible participants enrolled in the trial. General linear models did not reveal statistically significant differences between groups. Within group analyses using paired t-tests demonstrated improvement in age-adjusted fluid cognition [t (13) = 3.39, p = 0.005, Cohen's d = 0.61] and crystallized cognition [t (13) = 2.63, p = 0.02, Cohen's d = 0.70] within the aerobic training group but no significant improvement within the stretching group. Paired t-tests demonstrated significant improvement in both self-reported and parent-reported total quality of life measures in the aerobic training group [self-report t (13) = 3.51, p = 0.004, Cohen's d = 0.94; parent-report t (13) = 6.5, p < 0.0001, Cohen's d = 1.80] and the stretching group [self-report t (14) = 4.20, p = 0.0009, Cohen's d = 1.08; parent-report t (14) = 4.06, p = 0.0012, Cohen's d = 1.045]. Conclusion: Quality of life improved significantly in both the aerobic exercise and stretching groups; however, this study suggests that only sub-symptom exacerbation aerobic training was potentially beneficial for neurocognitive recovery, particularly the fluid cognition subset in the NIH Toolbox. Limited sample size and variation in outcomes measures limited ability to detect between group differences. Future research should focus on developing larger studies to determine optimal timing post-injury and intensity of active rehabilitation to facilitate neurocognitive recovery and improve quality of life after mTBI. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT02035579.

Spatial and temporal analysis center of pressure displacement during adolescence: Clinical implications of developmental changes.

This study aimed to provide insight into the development of postural control abilities in youth. A total of 276 typically developing adolescents (155 males, 121 females) with a mean age of 13.23 years (range of 7.11-18.80) were recruited for participation. Subjects performed two-minute quiet standing trials in bipedal stance on a force plate. Center of pressure (COP) trajectories were quantified using Sample Entropy (SampEn) in the anterior-posterior direction (SampEn-AP), SampEn in the medial-lateral direction (SampEn-ML), and Path Length (PL) measures. Three separate linear regression analyses were conducted to predict the relationship between age and each of the response variables after adjusting for individuals' physical characteristics. Linear regression models showed an inverse relationship between age and entropy measures after adjusting for body mass index. Results indicated that chronological age was predictive of entropy and path length patterns. Specifically, older adolescents exhibited center of pressure displacement (smaller path length) and less complex, more regular center of pressure displacement patterns (lower SampEn-AP and SampEn-ML values) compared to the younger children. These findings support prior studies suggesting that developmental changes in postural control abilities may continue throughout adolescence and into adulthood.

PHYSICAL THERAPY INTERVENTION STRATEGIES FOR PATIENTS WITH PROLONGED MILD TRAUMATIC BRAIN INJURY SYMPTOMS: A CASE SERIES.

BACKGROUND AND PURPOSE: Although most patients recover from a mild traumatic brain injury (mTBI) within 7-14 days, 10-30% of people will experience prolonged mTBI symptoms. Currently, there are no standardized treatment protocols to guide physical therapy interventions for this population. The purpose of this case series was to describe the unique, multimodal evaluation and treatment approaches for each of the patients with post-concussion syndrome (PCS). CASE DESCRIPTION: Six pediatric athletes with PCS who had participated in physical therapy and fit the inclusion criteria for review were retrospectively chosen for analysis. Patients received a cervical evaluation, an aerobic activity assessment, an oculomotor screen, and postural control assessment. Each patient participated in an individualized physical therapy treatment plan-of-care based on their presentation during the evaluation. OUTCOMES: Patients were treated for a mean of 6.8 treatment sessions over 9.8 weeks. Four of six patients returned to their pre-injury level of activity while two returned to modified activity upon completion of physical therapy. Improvements were observed in symptom scores, gaze stability, balance and postural control measures, and patient self-management of symptoms. All patients demonstrated adequate self-management of symptoms upon discharge from physical therapy. DISCUSSION/CONCLUSIONS: Physical therapy interventions for pediatric athletes with PCS may facilitate recovery and improve function. Further research is needed to validate effective tools for assessment of patients who experience prolonged concussion symptoms as well as to establish support for specific post-mTBI physical therapy interventions. LEVEL OF EVIDENCE: Level 4.

The Back Squat Part 2: Targeted Training Techniques to Correct Functional Deficits and Technical Factors that Limit Performance.

The back squat is a well-researched and widely used exercise to enhance fundamental movement competency that creates a foundation for optimal mechanical strategies during a broad range of activities. The primary commentary introduced the Back Squat Assessment (BSA): a criterion based assessment of the back squat that delineates 30 potentially observable functional deficits. This follow-up commentary provides a targeted system of training cues and exercises to supplement the BSA to guide corrective intervention. We propose a criterion driven approach to corrective exercise that can support practitioners in their goal to help individuals achieve movement competency in the back squat.

Reduced hip strength is associated with increased hip motion during running in young adult and adolescent male long-distance runners.

STUDY DESIGN: Controlled laboratory study. BACKGROUND AND PURPOSE: Anterior knee pain is one of the most common running symptoms reported in the literature. While the exact etiology is unknown, a lack of hip strength is suggested to contribute to abnormal running mechanics. The purpose of this research study was to evaluate the association between isokinetic hip strength and 3-D running kinematics. METHODS: 33 male high school and collegiate cross country runners participated in this study. Peak isokinetic hip abductor and hip extensor strength were assessed. Each subject also completed a treadmill running protocol at a self-selected speed (mean = 3.8 m/s). 3-D kinematic data were collected at 240 Hz using a 10-camera motion capture system. Pearson correlation coefficients were used to determine the relationship between hip strength and hip range of motion (ROM) during the stance phase of running (p<0.05). RESULTS: Peak isokinetic hip extensor torque was inversely correlated with transverse plane hip ROM (r = -.387, p = .026) but was not significantly related to sagittal plane hip ROM or frontal plane hip ROM. Peak isokinetic hip abductor torque was inversely correlated with frontal plane hip ROM (r=-.462, p=.008) but was not significantly related to either sagittal plane hip ROM or transverse plane hip ROM. Peak isokinetic hip extensor torque and peak isokinetic hip abductor torque were not significantly related to knee kinematics in any plane. CONCLUSIONS: Peak isokinetic hip extensor torque and peak isokinetic hip abductor torque are associated with transverse plane and frontal plane hip kinematics, but not knee kinematics. LEVELS OF EVIDENCE: Level 3b.

The back squat: A proposed assessment of functional deficits and technical factors that limit performance.

Fundamental movement competency is essential for participation in physical activity and for mitigating the risk of injury, which are both key elements of health throughout life. The squat movement pattern is arguably one of the most primal and critical fundamental movements necessary to improve sport performance, to reduce injury risk and to support lifelong physical activity. Based on current evidence, this first (1 of 2) report deconstructs the technical performance of the back squat as a foundation training exercise and presents a novel dynamic screening tool that incorporates identification techniques for functional deficits that limit squat performance and injury resilience. The follow-up report will outline targeted corrective methodology for each of the functional deficits presented in the assessment tool.

Relationship between hip strength and trunk motion in college cross-country runners.

PURPOSE: Hip strength may directly relate to abnormal running mechanics and contribute to the high incidence of overuse injuries in distance runners. The purpose of this study was to determine the relationship between hip isokinetic strength and thorax and pelvic motion during treadmill running. METHODS: Isokinetic hip strength and treadmill running kinematics were collected on 24 collegiate cross-country runners (14 males and 10 females). Each subject completed a running protocol on a treadmill at a self-selected speed (3.58 ± 0.26 m·s) and prescribed speed (3.58 ± 0.0 m·s). Kinematic data were collected with retroreflective markers attached to the thorax, pelvis, and each lower extremity segment (thigh, shank, and foot). Thorax and pelvis range of motion (ROM) were calculated from initial ground contact to toe-off. Pearson correlation coefficients were used to determine the relationship between strength and ROM (P < 0.05). Differences between male and female athletes were tested with mixed-design ANOVAs (P < 0.05). RESULTS: Isokinetic hip extension and abduction torque had significant inverse correlations to thorax axial rotation ROM during stance phase of running (r = -0.60 and r = -0.53) at self-selected speed. Frontal plane pelvic obliquity ROM was also significantly correlated to hip strength (extension r = -0.49; abduction r = -0.44). Similar correlations were found during the prescribed speed condition. Female runners had significantly decreased normalized strength (hip extension 1.8 ± 0.4 N·m·kg, P < 0.05; hip abduction 1.0 ± 0.2 N·m·kg, P < 0.05), increased pelvic obliquity (13.1° ± 2.6°, P < 0.05), and thorax axial rotation (34.5° ± 7.0°, P < 0.05) ROM compared to males (hip extension 2.5 ± 0.5 N·m·kg; hip abduction 1.3 ± 0.2 N·m·kg; pelvic obliquity 8.9° ± 1.9°; thorax axial rotation 22.6° ± 3.5°). CONCLUSIONS: Moderate correlations were found in hip extensor and hip abductor strength and pelvic and thorax motion during running in collegiate runners.

Test-retest consistency of a postural sway assessment protocol for adolescent athletes measured with a force plate.

PURPOSE/BACKGROUND: Postural control assessments can provide a powerful means of detecting concussion-related neurophysiological abnormalities and are considered an important part of the concussion management processes. Studies with college athletes indicate that postural sway analyzed using complexity metrics may provide a sensitive and novel way to detect post-concussion postural control impairments. The purpose of this study was to determine if a postural sway assessment protocol (PSAP) measured using a force plate system can serve as a reliable assessment tool for adolescent athletes. METHODS: The short-term and long-term test-retest reliability of the PSAP was examined in a group of adolescent female athletes under eyes open and eyes closed conditions. Detrended fluctuation analysis was used to evaluate the complexity of the times series data (i.e., degree of self-similarity across time scales). Conventional measures of standard deviation and total path length (distance traveled by the center-of-pressure) were also assessed. RESULTS: The complexity and conventional measures generally demonstrated good reliability coefficients for short-term and long-term test-retest reliability with both eyes open and eyes closed conditions. Intra-class Correlation Coefficient (ICC) values ranged from .38-.90 The highest ICC values corresponded with the short-term reliability for the eyes open condition, while the lower ICC values corresponded with the long-term reliability for the eyes closed condition. CONCLUSIONS: The results of this study indicate that the PSAP demonstrated good short-term and long-term test-retest reliability. In addition, no evidence of learning effects was elicited through this study. Future studies should further explore the validity and feasibility of the use of this protocol for different age groups, different types of athletes, and longitudinal evaluations of post-concussion impairments. CLINICAL RELEVANCE: This study provides preliminary support for the utility of a postural sway assessment protocol measured using a force plate for use with adolescent athletes. LEVEL OF EVIDENCE: Level III.