Gait Performance Is Associated with Subsequent Lower Extremity Injury following Concussion

Post-Acute Concussion-Related Differences in Neuromotor Control Measured Using a Low-Cost Movement Assessment System: A Feasibility Study

Background

Athletes prematurely cleared to play following concussion increase their risk for subsequent concussion and musculoskeletal injury, leading practitioners to call for low-cost and objective tools to identify lingering neuromotor control deficits following concussion. # PurposeThe purpose of this feasibility study was to determine the usefulness of Mizzou Point-of-care Assessment System (MPASS) measures for creating a discriminant model classifying individuals as being either healthy or in the post-acute phase of concussion (having suffered a concussion within the prior three months).

Study Design

Cross-sectional.

Methods

Ten participants with concussion injury (Mean = 3.9 ± 1.66 wks. post-concussion) and twelve with no concussion within the prior year participated in this study. All participants completed walking (normal, serial subtraction by seven, and head shaking), Romberg balance (eyes open and eyes closed on firm surface), and reaction time tasks while MPASS recorded kinematics, kinetics, and reaction time. Principal component analysis (PCA) was used to reduce the dimensionality of MPASS data.

Results

Using four retained principal components (PCs), the LDA model achieved a statistically significant (p = 0.007) accuracy of 82% with 80% sensitivity and 83% specificity for classifying participants into groups.

Conclusion

This work presents a framework for assessing the discriminative power of multidimensional and clinically feasible tools for assessing human movement.

Level of Evidence

3.

Return-to-Play With R2Play: Protocol for Evaluating Cross-Site Feasibility, Face Validity, and Content Validity of a Multidomain Concussion Assessment Tool for Youth

CONTEXT

Clinical concussion assessments do not typically simulate the speed or complexity of sport. Performance changes arising from combined physical, cognitive, and sensory demands of sport may thus remain undetected during rehabilitation. We developed R2Play, a multidomain return-to-play assessment tool for youth with concussions. R2Play involves levels and conditions that vary in physical, cognitive, and sensory load to simulate the multidomain demands of sport.

OBJECTIVES

To explore cross-site feasibility, face validity, and content validity of R2Play by integrating quantitative and qualitative data.

METHODS

Convergent mixed-methods feasibility study. Five sites will each recruit 5 clinicians (total nc = 25) and 10 youth sport participants (ages 10-25 y) with a history of concussion in the previous year (total ny = 50). Feasibility will be evaluated using quantitative criteria for acceptability, demand, implementation, practicality, and integration, and qualitative investigated data from content analysis of postassessment interviews with youth and clinician participants. Face validity will be investigated in postassessment interviews. Content validity will be established through (1) changes in performance metrics (time to completion, errors, and heart rate) across R2Play levels, (2) youth-perceived physical and cognitive exertion for each level, and (3) overall clinician perceptions determined through postassessment interviews. Qualitative and quantitative data will be merged through joint display to identify areas of convergence, divergence, and complementarity, and to establish meta-inferences about feasibility, face validity, and content validity.

DISCUSSION

This study aims to demonstrate the face and content validity of R2Play, and its feasibility for cross-site implementation. Findings will guide further iteration of R2Play and establish the foundation for a larger multicenter validation study to establish the psychometric properties of R2Play. This work represents an important first step toward the implementation of an ecologically valid multidomain assessment tool designed to support a safe and efficient return-to-play after concussion, ultimately reducing the risk of recurrent concussion and subsequent injury.

Clinical Measures Associated with Subsequent Injury after Adolescent Concussion: A Prospective Cohort Study

PURPOSE

This study aimed to examine associations between clinical measures (self-reported and clinician administered) and subsequent injury rates in the year after concussion return to play (RTP) among adolescent athletes.

METHODS

We performed a prospective, longitudinal study of adolescents ages 13-18 yr. Each participant was initially assessed within 21 d of concussion and again within 5 d of receiving RTP clearance from their physician. Participants completed self-report measures: the Pittsburgh Sleep Quality Index and Tampa Scale of Kinesiophobia, and clinician-administered measures: single- and dual-task tandem gait and reaction time (RT; simple and clinical) assessments. They then completed monthly surveys for a year after RTP, which assessed exposure to injury (sport participation) and subsequent injuries (musculoskeletal or concussions) sustained. We used Poisson regression models to calculate injury rate ratios with the number of subsequent injuries sustained as the outcome, adjusted for RTP clearance time and competitive exposures for each measure.

RESULTS

Forty-one participants were included (age = 15.5 ± 1.3 yr, 56% female, 9.6 ± 4.6 d postconcussion; 38.0 ± 31.5 d to RTP). A higher injury rate per athletic exposure was observed for simple RT ≥ 505 ms versus <505 ms (injury rate ratio = 2.96, 95% confidence interval = 1.41-6.60, P = 0.005). Injury rates did not significantly differ by Pittsburgh Sleep Quality Index or Tampa Scale of Kinesiophobia scores, single/dual-task tandem gait time, or clinical RT.

CONCLUSIONS

Simple RT may be one risk factor that is associated with higher rates of subsequent injury after adolescent concussion. A simple RT measure incorporated into a comprehensive concussion RTP assessment may identify some individuals at higher risk of subsequent injury in the year after concussion, although further research is needed to better understand this relationship.

A Machine Learning Model for Post-Concussion Musculoskeletal Injury Risk in Collegiate Athletes

Background

Emerging evidence indicates an elevated risk of post-concussion musculoskeletal (MSK) injuries in collegiate athletes; however, identifying athletes at highest risk remains to be elucidated.

Objective

The purpose of this study was to model post-concussion MSK injury risk in collegiate athletes by integrating a comprehensive set of variables by machine learning.

Methods

A risk model was developed and tested on a dataset of 194 athletes (155 in the training set and 39 in the test set) with 135 variables entered into the analysis, which included participant's heath and athletic history, concussion injury and recovery specific criteria, and outcomes from a diverse array of concussions assessments. The machine learning approach involved transforming variables by the Weight of Evidence method, variable selection using L1-penalized logistic regression, model selection via the Akaike Information Criterion, and a final L2-regularized logistic regression fit.

Results

A model with 48 predictive variables yielded significant predictive performance of subsequent MSK injury with an area under the curve of 0.82. Top predictors included cognitive, balance, and reaction at Baseline and Acute timepoints. At a specified false positive rate of 6.67%, the model achieves a true positive rate (sensitivity) of 79% and a precision (positive predictive value) of 95% for identifying at-risk athletes via a well calibrated composite risk score.

Conclusion

These results support the development of a sensitive and specific injury risk model using standard data combined with a novel methodological approach that may allow clinicians to target high injury risk student-athletes. The development and refinement of predictive models, incorporating machine learning and utilizing comprehensive datasets, could lead to improved identification of high-risk athletes and allow for the implementation of targeted injury risk reduction strategies by identifying student-athletes most at risk for post-concussion MSK injury.

Acute and Longitudinal Effects of Concussion on Reactive Balance in Collegiate Athletes

BACKGROUND

Postural instability is a common observation after concussions, with balance assessments playing a crucial role in clinical evaluations. Widely used post-concussion balance tests focus primarily on static and dynamic balance, excluding the critical aspect of reactive balance.

OBJECTIVES

This study investigated the acute and longitudinal effects of concussion on reactive balance in collegiate athletes.

METHODS

Concussed and healthy matched controls NCAA division I athletes were assessed at pre-season baseline and 4 post-concussion timepoints: acute, pre-return-to-play (RTP), post-RTP, and 6 months post-concussion. The instrumented-modified Push and Release test measured reactive balance during single- and dual-task conditions. Longitudinal effects of concussions on time to stability and step latency metrics were investigated applying Generalized Estimating Equations.

RESULTS

Acutely after concussion, athletes demonstrated impaired reactive balance, indicated by longer times to stability, in dual-task conditions (P = .004). These acute impairments were transient and recovered over time. Exploratory analyses revealed that athletes who sustained their first lifetime concussion exhibited both acute (P = .037) and longitudinal (P = .004 at post-RTP) impairments in single- and dual-task compared to controls with no lifetime concussion.

CONCLUSIONS

This comprehensive evaluation provides insights into the multifaceted nature of post-concussion impairments and emphasizes the importance of considering cognitive demand and history of concussions in assessing athletes' balance.

Research Letter: Concussion-Related General Startle Suppression in Adolescent Athletes

OBJECTIVES

We investigated the acoustic startle reflex in recently concussed adolescent athletes compared to healthy controls and those with concussion history (>1 year prior) but no current symptoms. We hypothesized that individuals with recent concussion would have a suppressed startle response compared to healthy controls.

METHODS

We conducted a cross-sectional study on 49 adolescent athletes with a recent concussion (n = 20; age: 14.6 ± 1.6 years; 60% female), a concussion history > 1 year prior (n = 16; age: 14.8 ± 2.0 years; 44% female), and healthy controls (n = 13; age: 13.3 ± 2.8 years; 54% female). We measured the eyeblink of the general startle reflex via electromyography activity of the orbicularis oculi muscle using electrodes placed under the right eye. Measurement sessions included twelve 103 decibel acoustic startle probes ~50 milliseconds in duration delivered ~15-25 seconds apart. The primary dependent variable was mean startle magnitude (µV), and group was the primary independent variable. We used a one-way analysis of variance followed by a Tukey post hoc test to compare mean startle magnitude between groups.

RESULTS

Mean startle magnitude significantly differed (F = 5.49, P = .007) among the groups. Mean startle magnitude was significantly suppressed for the concussion ( P = .01) and concussion history groups ( P = .02) compared to healthy controls. There was no significant difference between the recent concussion and concussion history groups ( P = 1.00).

CONCLUSION

Our results provide novel evidence for startle suppression in adolescent athletes following concussion. The concussion history group had an attenuated startle response beyond resolution of their recovery, suggesting there may be lingering physiological dysfunction.

Diagnosed concussion is associated with increased risk for upper extremity injury in community rugby players in males only

OBJECTIVES

To cross-sectionally determine 1) the association between lifetime diagnosed concussion and upper extremity musculoskeletal injury (UE-MSI) amongst a novel cohort of community rugby union players and 2) the sex specific risk of UE-MSI given concussion history among these rugby players.

METHODS

1,037 (31.0% female, 31.6 + 11.3 years) rugby players completed an online survey to determine lifetime history of diagnosed concussion (yes; no) and UE-MSI (yes; no). A chi-squared test of association was performed between concussion and any UE-MSI; odds ratio risk was also determined. Analyses were repeated by sex (male; female) and with specific UE-MSI (e.g. sprains, broken bones, dislocations).

RESULTS

There was a significant association between concussion and any UE-MSI for this cohort (χ(1) = 10.802, p = 0.001, OR = 1.70 [95%CI: 1.23-2.32]). There was a significant association between concussion and any UE-MSI among males for (χ(1) = 13.612, p < 0.001, OR = 2.20 [95%CI: 1.4-3.3]) but not among females (χ(1) = 0.735, p = 0.391, OR = 1.20 [95%CI: 0.8-2.0]).

CONCLUSIONS

Community rugby players with a history of diagnosed concussion are at 1.7× increased odds for history of any UE-MSI compared to rugby players who are concussion naïve; sex specific analyses revealed only increased risk among males. Sports medicine professionals and rugby stakeholders should view concussions as a risk factor and utilize established injury prevention programs to help reduce future UE-MSI in athletes.

NCAA football players are at higher risk of upper extremity injury after first-time concussion

BACKGROUND

Previous research has demonstrated that concussions increase the risk of subsequent lower extremity musculoskeletal injury in athletes. However, the risk of upper extremity injury in athletes' post-concussion is poorly understood.

METHODS

All concussed football players within a National Collegiate Athletic Association (NCAA) Division I conference athletic database were identified between 2017 and 2021. After exclusions, each athlete experiencing their first concussion was then retrospectively reviewed for upper extremity injuries in the year prior to their concussion and in the year beginning at 90 days after their concussion. All upper extremity injuries were identified and the odds ratio, 95% confidence interval, and statistical significance between groups were calculated in Microsoft Excel.

RESULTS

160 de-identified football players from a single conference who were first diagnosed with concussions in the seasons from 2017 through 2021 met inclusion criteria. In these athletes the odds of upper extremity injury in year following first diagnosed concussion were 2.36 times higher than in the year prior (95% CI 1.13-4.95, p = 0.02). Shoulder was the most common site of injury with 57.7% of injuries compared to 19.2% in the hand, 15.4% in the elbow, 7.7% in the forearm, and 0% in the wrist.

CONCLUSION

This study demonstrates that collegiate football players are at a 2.36 times greater risk of upper extremity injury in the year following their first diagnosed concussion compared to the year preceding it. The most common site of upper extremity injury after concussion was the shoulder.

LEVEL OF EVIDENCE

III.

Analyzing Dual-Task Paradigms to Improve Postconcussion Assessment and Management

CONTEXT

Dual-task (simultaneous cognitive-motor activities) assessments have been adapted into reliable and valid clinical concussion measures. However, abundant motor and cognitive variations leave researchers and clinicians uncertain about which combinations elicit the intended dual-task effect. Our objective was to examine differences between commonly employed dual-task motor and cognitive combinations among healthy, college-aged individuals.

DESIGN

Cross-sectional laboratory study.

METHODS

Twenty participants (age: 21.3 [2.4] y; height: 176.0 [9.1] cm; mass: 76.0 [16.4] kg; 20% with concussion history) completed 4 motor tasks (gait, tandem gait, single-leg balance, and tandem balance) under 5 cognitive conditions (single task, subtraction, month reversal, spelling backward, and visual Stroop) in a research laboratory. The motor performance outcomes were spatiotemporal variables for gait and tandem gait and center of pressure path length (in centimeters) for single-leg and tandem balance. Cognitive outcomes were response rate (responses/second) and cognitive accuracy. We used separate repeated-measures analyses of variance for each motor and cognitive outcome with post hoc Tukey t tests.

RESULTS

Gait velocity, gait stride length, and tandem gait velocity demonstrated significant cognitive-motor interactions (P's < .001) such that all dual-task conditions resulted in varyingly slower or shorter movement than single task. Conversely, single-leg balance (P = .627) and tandem balance (P = .434) center of pressure path length did not significantly differ among the dual-task cognitive conditions or relative to single task. Statistically significant cognitive-motor interactions were observed only for spelling backward accuracy (P = .004) and response rates for spelling backward, month reversal, and visual Stroop (P's < .001) such that worse accuracy, but faster response rates, occurred during motor tasks.

CONCLUSIONS

Gait and tandem gait motor tasks accompanied with spelling backward or subtraction cognitive tasks demonstrated consistently strong dual-task effects and, therefore, may be the best suited for clinical and research use following concussion.

Trunk and Lower Extremity Biomechanics in Female Athletes With and Without a Concussion History

CONTEXT

Athletes with a history of concussion are at a greater risk for lower extremity musculoskeletal injury. Female athletes may be at an even greater risk than male athletes. Previous researchers on postconcussion landing biomechanics have focused on the lower extremities, but the trunk plays a crucial role as an injury risk factor.

OBJECTIVE

To compare lower extremity and trunk biomechanics during jump-landing and cutting maneuvers between female athletes with and those without a concussion history.

DESIGN

Cross-sectional study.

SETTING

Biomechanics laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 26 athletes (mean ± SD age = 19.0 ± 1.3 years, height = 1.68 ± 0.07 m, mass = 64.02 ± 6.76 kg, body mass index = 22.58 ± 1.97 kg/m2; median [interquartile range] time since most recent concussion = 37.5 months [25.0 months, 65.8 months]) with a concussion history and 38 athletes (age = 19.0 ± 1.1 years, height = 1.71 ± 0.08 m, mass = 64.72 ± 9.45 kg, body mass index = 22.14 ± 1.80 kg/m2) without a concussion history.

MAIN OUTCOME MEASURE(S)

Peak kinetics (vertical ground reaction force, vertical loading rate, external knee-abduction moment, and external knee-flexion moment) and kinematics (trunk-flexion angle, trunk lateral-bending angle, ankle-dorsiflexion angle, knee-flexion angle, knee-abduction angle, and hip-flexion angle) were obtained during the eccentric portion of jump-landing and cutting tasks. Separate 2 (group) × 2 (limb) between- and within-factors analyses of covariance were used to compare outcomes between groups. We covaried for time since the most recent concussion and the limb that had a history of musculoskeletal injury.

RESULTS

Athletes with a concussion history displayed a greater peak knee-abduction angle in their nondominant limb than their dominant limb (P = .01, ηp2 = 0.107) and the nondominant limb of athletes without a concussion history (P = .02, ηp2 = 0.083) during jump landing. They also had less trunk lateral bending during cutting compared with athletes without a concussion history (P = .005, ηp2 = 0.126).

CONCLUSIONS

Our results indicated landing biomechanics are different between female athletes with and those without a concussion history. This finding may be due to impairments in neuromuscular control postconcussion that may ultimately increase the risk of subsequent lower extremity injury, although further research is warranted given the cross-sectional nature of our study.

The Influence of Sports-Related Concussion on Cognition and Landing Biomechanics in Collegiate Athletes

Injury surveillance data indicate that collegiate athletes are at greater risk for lower extremity (LE) injuries following sports-related concussion (SRC). While the association between SRC and LE injury appears to be clinically relevant up to 1-year post-SRC, little evidence has been provided to determine possible mechanistic rationales. Thus, we aimed to compare collegiate athletes with a history of SRC to matched controls on biomechanical and cognitive performance measures associated with LE injury risk. Athletes with a history of SRC (n = 20) and matched controls (n = 20) performed unanticipated bilateral land-and-cut tasks and cognitive assessments. Group-based analyses (ANOVA) and predictive modeling (C5.0 decision tree algorithm) were used to compare group differences on biomechanical and cognitive measures. Collegiate athletes with a history of SRC demonstrated approximately six degrees less peak knee flexion on both dominant (p = 0.03, d = 0.71) and nondominant (p = 0.02, d = 0.78) limbs during the land-and-cut tasks compared to controls. Verbal Memory, knee flexion, and Go/No Go total score (C5.0 decision tree algorithm) were identified as the strongest indicators of previous SRC injury history. Reduced knee flexion during sport-specific land-and-cut tasks may be a mechanism for increased LE injury risk in athletes with a history of SRC. There appears to be multiple biomechanical and cognitive predictors for identifying previous SRC in collegiate athletes, providing evidence to support a multifactorial SRC management strategy to reduce future injury risk.

Impaired Neuromotor Control During Gait in Concussed Adolescents-A Frequency Analysis

Disruptions in gait function are common after concussion in adolescents; however, the neuromotor control deficits driving these gait disruptions are not well known. Fifteen concussed (age mean [SD]): 17.4 [0.6], 13 females, days since injury: 26.3 [9.9]) and 17 uninjured (age: 18.0 [0.7], 10 females) adolescents completed 3 trials each of single-task gait and dual-task gait (DT). During DT, participants simultaneously walked while completing a serial subtraction task. Gait metrics and variability in instantaneous mean frequency in lower extremity muscles were captured by inertial sensors and surface electromyography, respectively. A 2-way analysis of covariance was used to compare gait metrics across groups and conditions. Functional principal components analysis was used to identify regions of variability in instantaneous mean frequency curves. Functional principal component scores were compared across groups using a Welch statistic. Both groups displayed worse performance on gait metrics during DT condition compared to single-task, with no differences between groups (P < .001). Concussed adolescents displayed significantly greater instantaneous mean frequency, indicated by functional principal component 1, in the tibialis anterior, biceps femoris, and semitendinosus (P < .05) during single-task and DT compared with uninjured adolescents. Our observations suggest that concussed adolescents display inefficient motor unit recruitment lasting longer than 2 weeks following injury, regardless of the addition of a secondary task.

Acute and Longitudinal Effects of Sport-related Concussion on Reactive Balance

Postural instability is a common observation after concussions, with balance assessments playing a crucial role in clinical evaluations. Widely used post-concussion balance tests focus primarily on static and dynamic balance, excluding the critical aspect of reactive balance. This study investigated the acute and longitudinal effects of concussion on reactive balance in collegiate athletes. The assessments were conducted at pre-season baseline and 4 post-concussion timepoints: acute, pre-return-to-play, post-return-to-play, and six months post-concussion. The instrumented-modified Push and Release test measured reactive balance. Longitudinal effects of concussions on time to stability and step latency metrics were investigated applying Generalized Estimating Equations. Acutely after concussion, athletes demonstrated impaired reactive balance, indicated by longer times to stability, in dual-task conditions ( p = 0.004). These acute impairments were transient and recovered over time. Exploratory analyses revealed that athletes who sustained their first lifetime concussion exhibited both acute ( p = 0.037) and longitudinal ( p = 0.004 at post-return-to-play) impairments in single- and dual-task compared to controls with no lifetime concussion. This comprehensive evaluation provides insights into the multifaceted nature of post-concussion impairments and emphasizes the importance of considering cognitive demand and history of concussions in assessing athletes' balance.

Initial investigation of kinesiophobia as a predictor of functional reaction time one year after concussion

Aim

The relationship between post-concussion kinesiophobia and clinical and functional reaction time (RT) beyond clinical recovery remains to be elucidated.

Methods

College-aged participants with (n = 20) and without (n = 20) a concussion history completed patient-reported outcomes, and RT tasks. Kinesiophobia, symptoms and RTs were compared using t-tests. Linear regressions were performed to determine if kinesiophobia predicted RT measures and dual-task cost.

Results

The concussion history group reported higher scores (p < 0.01) for all patient-reported outcomes. We observed significant single-task RT differences between groups (p = 0.013) such that those without a concussion history (m = 0.51s ± 0.08) were faster (m = 0.59s ± 0.12). There were no clinical or dual-task RT differences between groups (p > 0.05). Kinesiophobia significantly predicted single-task RT (R2 = 0.22).

Discussion

Kinesiophobia should be considered when measuring RT.

Sport Type and Risk of Subsequent Injury in Collegiate Athletes Following Concussion: a LIMBIC MATARS Consortium Investigation

OBJECTIVE

To investigate the association between sport type (collision, contact, non-contact) and subsequent injury risk following concussion in collegiate athletes.

MATERIALS AND METHODS

This retrospective chart review of 248 collegiate athletes with diagnosed concussions (age: 20.0 ± 1.4 years; height: 179.6 ± 10.9 cm; mass: 79.0 ± 13.6 kg, 63% male) from NCAA athletic programs (n = 11) occurred between the 2015-2020 athletic seasons. Acute injuries that occurred within six months following concussion were evaluated. Subsequent injuries were grouped by lower extremity, upper extremity, trunk, or concussion. The independent variable was sport type: collision, contact, non-contact. A Cox proportional hazard model was used to assess the risk of subsequent injury between sport types.

RESULTS

Approximately 28% (70/248) of athletes sustained a subsequent acute injury within six months post-concussion. Collision sport athletes had a significantly higher risk of sustaining any injury (HR: 0.41, p < 0.001, 95% CI: 0.28, 0.62), lower extremity (HR: 0.55, p = 0.04, 95% CI: 0.32, 0.97), and upper extremity (HR: 0.41, p = 0.01, 95% CI: 0.20, 0.81) injuries following concussion. No differences between sport types were observed for other injuries.

CONCLUSION

Collision sport athletes had a higher rate of any subsequent injury, lower, and upper extremity injuries following concussion. Future research should focus on sport-specific secondary injury prevention efforts.

A Multifaceted Approach to Interpreting Reaction Time Deficits After Adolescent Concussion

CONTEXT

Reaction time (RT) is a critical element of return to participation (RTP), and impairments have been linked to subsequent injury after a concussion. Current RT assessments have limitations in clinical feasibility and in the identification of subtle deficits after concussion symptom resolution.

OBJECTIVES

To examine the utility of RT measurements (clinical drop stick, simple stimulus-response, single-task Stroop, and dual-task Stroop) to differentiate between adolescents with concussion and uninjured control individuals at initial assessment and RTP.

DESIGN

Prospective cohort study.

SETTING

A pediatric sports medicine center associated with a regional tertiary care hospital.

PATIENTS OR OTHER PARTICIPANTS

Twenty-seven adolescents with a concussion (mean age = 14.8 ± 2.1 years; 52% female; tested 7.0 ± 3.3 days postconcussion) and 21 uninjured control individuals (mean age = 15.5 ± 1.6 years; 48% female).

MAIN OUTCOME MEASURE(S)

Participants completed the Post-Concussion Symptoms Inventory (PCSI) and a battery of RT tests: clinical drop stick, simple stimulus-response, single-task Stroop, and dual-task Stroop.

RESULTS

The concussion group demonstrated slower clinical drop stick (β = 58.8; 95% CI = 29.2, 88.3; P < .001) and dual-task Stroop (β = 464.2; 95% CI = 318.4, 610.0; P < .001) RT measures at the initial assessment than the uninjured control group. At 1-month follow up, the concussion group displayed slower clinical drop stick (238.9 ± 25.9 versus 188.1 ± 21.7 milliseconds; P < .001; d = 2.10), single-task Stroop (1527.8 ± 204.5 versus 1319.8 ± 133.5 milliseconds; P = .001; d = 1.20), and dual-task Stroop (1549.9 ± 264.7 versus 1341.5 ± 114.7 milliseconds; P = .002; d = 1.04) RT than the control group, respectively, while symptom severity was similar between groups (7.4 ± 11.2 versus 5.3 ± 6.5; P = .44; d = 0.24). Classification accuracy and area under the curve (AUC) values were highest for the clinical drop stick (85.1% accuracy, AUC = 0.86, P < .001) and dual-task Stroop (87.2% accuracy, AUC = 0.92, P < .002) RT variables at initial evaluation.

CONCLUSIONS

Adolescents recovering from concussion may have initial RT deficits that persist despite symptom recovery. The clinical drop stick and dual-task Stroop RT measures demonstrated high clinical utility given high classification accuracy, sensitivity, and specificity to detect postconcussion RT deficits and may be considered for initial and RTP assessment.

Integrative data analysis to identify persistent post-concussion deficits and subsequent musculoskeletal injury risk: project structure and methods

Concussions are a serious public health problem, with significant healthcare costs and risks. One of the most serious complications of concussions is an increased risk of subsequent musculoskeletal injuries (MSKI). However, there is currently no reliable way to identify which individuals are at highest risk for post-concussion MSKIs. This study proposes a novel data analysis strategy for developing a clinically feasible risk score for post-concussion MSKIs in student-athletes. The data set consists of one-time tests (eg, mental health questionnaires), relevant information on demographics, health history (including details regarding the concussion such as day of the year and time lost) and athletic participation (current sport and contact level) that were collected at a single time point as well as multiple time points (baseline and follow-up time points after the concussion) of the clinical assessments (ie, cognitive, postural stability, reaction time and vestibular and ocular motor testing). The follow-up time point measurements were treated as individual variables and as differences from the baseline. Our approach used a weight-of-evidence (WoE) transformation to handle missing data and variable heterogeneity and machine learning methods for variable selection and model fitting. We applied a training-testing sample splitting scheme and performed variable preprocessing with the WoE transformation. Then, machine learning methods were applied to predict the MSKI indicator prediction, thereby constructing a composite risk score for the training-testing sample. This methodology demonstrates the potential of using machine learning methods to improve the accuracy and interpretability of risk scores for MSKI.

Does prior concussion lead to biomechanical alterations associated with lateral ankle sprain and anterior cruciate ligament injury? A systematic review and meta-analysis

OBJECTIVE

To determine whether individuals with a prior concussion exhibit biomechanical alterations in balance, gait and jump-landing tasks with and without cognitive demands that are associated with risk of lateral ankle sprain (LAS) and anterior cruciate ligament (ACL) injury.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Five electronic databases (Web of Science, Scopus, PubMed, SPORTDiscus and CiNAHL) were searched in April 2023.

ELIGIBILITY CRITERIA

Included studies involved (1) concussed participants, (2) outcome measures of spatiotemporal, kinematic or kinetic data and (3) a comparison or the data necessary to compare biomechanical variables between individuals with and without concussion history or before and after a concussion.

RESULTS

Twenty-seven studies were included involving 1544 participants (concussion group (n=757); non-concussion group (n=787)). Individuals with a recent concussion history (within 2 months) had decreased postural stability (g=0.34, 95% CI 0.20 to 0.49, p<0.001) and slower locomotion-related performance (g=0.26, 95% CI 0.11 to 0.41, p<0.001), both of which are associated with LAS injury risk. Furthermore, alterations in frontal plane kinetics (g=0.41, 95% CI 0.03 to 0.79, p=0.033) and sagittal plane kinematics (g=0.30, 95% CI 0.11 to 0.50, p=0.002) were observed in individuals approximately 2 years following concussion, both of which are associated with ACL injury risk. The moderator analyses indicated cognitive demands (ie, working memory, inhibitory control tasks) affected frontal plane kinematics (p=0.009), but not sagittal plane kinematics and locomotion-related performance, between the concussion and non-concussion groups.

CONCLUSION

Following a recent concussion, individuals display decreased postural stability and slower locomotion-related performance, both of which are associated with LAS injury risk. Moreover, individuals within 2 years following a concussion also adopt a more erect landing posture with greater knee internal adduction moment, both of which are associated with ACL injury risk. While adding cognitive demands to jump-landing tasks affected frontal plane kinematics during landing, the altered movement patterns in locomotion and sagittal plane kinematics postconcussion persisted regardless of additional cognitive demands.

PROSPERO REGISTRATION NUMBER

CRD42021248916.

Associations Between Head Injury and Subsequent Risk of Falls: Results From the Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND AND OBJECTIVES

Falls are a leading cause of head injury among older adults, but the risk of fall occurring after a head injury is less well-characterized. We sought to examine the association between head injury and subsequent risk of falls requiring hospital care among community-dwelling older adults.

METHODS

This analysis included 13,081 participants in the Atherosclerosis Risk in Communities Study enrolled in 1987-1989 and followed through 2019. The association of head injury (time-varying exposure, self-reported and/or ICD-9/10 code identified) with the risk of subsequent (occurring >1-month after head injury) falls requiring hospital care (ICD-9/10 code defined) was modeled using Cox proportional hazards regression. Secondary analyses included Fine and Gray proportional hazards regression to account for the competing risk of death, analysis of head injury frequency and severity, and formal testing for interaction by age, sex, and race. Models were adjusted for age, sex, race/center, education, military service, alcohol consumption, smoking, diabetes, hypertension, and psychotropic medication use.

RESULTS

The mean age of participants at baseline was 54 years, 58% were female, 28% were Black, and 14% had at least one head injury occurring over the study period. Over a median 23 years of follow-up, 29% of participants had a fall requiring medical care. In adjusted Cox proportional hazards models, individuals with head injury had 2.01 (95% CI 1.85-2.18) times the risk of falls compared with individuals without head injury. Accounting for the competing risk of mortality, individuals with head injury had 1.69 (95% CI 1.57-1.82) times the risk of falls compared with individuals without head injury. We observed stronger associations among men compared with women (men: hazard ratio [HR] = 2.60, 95% CI 2.25-3.00; women: HR = 1.80, 95% CI 1.63-1.99, p-interaction <0.001). We observed evidence of a dose-response association for head injury number and severity with fall risk (1 injury: HR = 1.68, 95% CI 1.53-1.84; 2+ injuries: HR = 2.37, 95% CI 1.92-2.94 and mild: HR = 1.97, 95% CI 1.78-2.18; moderate/severe/penetrating: HR = 2.50, 95% CI 2.06-3.02).

DISCUSSION

Among community-dwelling older adults followed over 30 years, head injury was associated with subsequent falls requiring medical care. We observed stronger associations among men and with increasing number and severity of head injuries. Whether older individuals with head injury might benefit from fall prevention measures should be a focus of future research.

Ankle Sprain History Does Not Significantly Alter Single- and Dual-Task Spatiotemporal Gait Mechanics

CONTEXT

Single- and dual-task walking gait assessments have been used to identify persistent movement and cognitive dysfunction among athletes with concussions. However, it is unclear whether previous ankle sprain injuries confound these outcomes during baseline testing. The purpose of this study was to determine the effects of (1) ankle sprain history and (2) time since prior ankle sprain injury on single- and dual-task spatiotemporal gait outcomes and cognitive measures.

DESIGN

Cross-sectional study.

METHODS

We assessed 60 college Division-I athletes (31 with ankle sprain history; 13 females and 18 males, 19.3 [0.8] y; 29 with no ankle sprain history, 14 females and 15 males, 19.7 [0.9] y) who completed injury history forms and underwent concussion baseline testing. Athletes completed single- and dual-task gait assessments by walking back and forth along an 8-m walkway for 40 seconds. Athletes wore a smartphone with an associated mobile application on their lumbar spine to record spatiotemporal gait parameters and dual-task cognitive performance. Separate multivariate analyses of variance were used to assess the effects of ankle sprain injury history on spatiotemporal measures, gait variability, and cognitive performance. We performed a multivariate regression subanalysis on athletes who reported time since injury (n = 23) to assess temporal effects on gait and cognitive performance.

RESULTS

Athletes with and without a history of ankle sprains had comparable spatiotemporal and gait variability outcomes during single- (P = .42; P = .13) and dual-task (P = .75; P = .55) conditions. Additionally, ankle sprain injury history did not significantly influence cognitive performance (P = .35). Finally, time since ankle sprain did not significantly affect single- (P = .75) and dual-task gait (P = .69), nor cognitive performance (P = .19).

CONCLUSIONS

Ankle sprain injury history did not significantly alter spatiotemporal gait outcomes nor cognitive performance during this common clinical assessment. Future studies may consider including athletes with ankle sprain injury history during concussion assessments.

Neurophysiological and gait outcomes during a dual-task gait assessment in concussed adolescents

BACKGROUND

Gait deficits are common after concussion in adolescents. However, the neurophysiological underpinnings of these gait deficiencies are currently unknown. Thus, the goal of this study was to compare spatiotemporal gait metrics, prefrontal cortical activation, and neural efficiency between concussed adolescents several weeks from injury and uninjured adolescents during a dual-task gait assessment.

METHODS

Fifteen concussed (mean age[SD]: 17.4[0.6], 13 female, days since injury: 26.3[9.9]) and 17 uninjured adolescents (18.0[0.7], 10 female) completed a gait assessment with three conditions repeated thrice: single-task walking, single-task subtraction, and dual-task, which involved walking while completing a subtraction task simultaneously. Gait metrics were measured using an inertial sensor system. Prefrontal cortical activation was captured via functional near-infrared spectroscopy. Neural efficiency was calculated by relating gait metrics to prefrontal cortical activity. Differences between groups and conditions were examined, with corrections for multiple comparisons.

FINDINGS

There were no significant differences in gait metrics between groups. Compared to uninjured adolescents, concussed adolescents displayed significantly greater prefrontal cortical activation during the single-task subtraction (P = 0.01) and dual-task (P = 0.01) conditions with lower neural efficiency based on cadence (P = 0.02), gait cycle duration (P = 0.03), step duration (P = 0.03), and gait speed (P = 0.04) during the dual-task condition.

INTERPRETATION

Our findings suggest that several weeks after injury concussed adolescents demonstrate lower neural efficiency and display a cost to gait performance when cognitive demand is high, e.g., while multitasking, suggesting that the concussed adolescent brain is less able to compensate when attention is divided between two concurrent tasks.

Rethinking recovery in adolescent concussions: Network-level functional connectivity alterations associated with motor deficits

Adolescents who are clinically recovered from concussion continue to show subtle motor impairment on neurophysiological and behavioral measures. However, there is limited information on brain-behavior relationships of persistent motor impairment following clinical recovery from concussion. We examined the relationship between subtle motor performance and functional connectivity of the brain in adolescents with a history of concussion, status post-symptom resolution, and subjective return to baseline. Participants included 27 adolescents who were clinically recovered from concussion and 29 never-concussed, typically developing controls (10-17 years); all participants were examined using the Physical and Neurologic Examination of Subtle Signs (PANESS). Functional connectivity between the default mode network (DMN) or dorsal attention network (DAN) and regions of interest within the motor network was assessed using resting-state functional magnetic resonance imaging (rsfMRI). Compared to controls, adolescents clinically recovered from concussion showed greater subtle motor deficits as evaluated by the PANESS and increased connectivity between the DMN and left lateral premotor cortex. DMN to left lateral premotor cortex connectivity was significantly correlated with the total PANESS score, with more atypical connectivity associated with more motor abnormalities. This suggests that altered functional connectivity of the brain may underlie subtle motor deficits in adolescents who have clinically recovered from concussion. More investigation is required to understand the persistence and longer-term clinical relevance of altered functional connectivity and associated subtle motor deficits to inform whether functional connectivity may serve as an important biomarker related to longer-term outcomes after clinical recovery from concussion.

Reliability and Minimal Detectable Change of the Standardized Assessment of Reaction Time

CONTEXT

Postconcussion reaction time deficits are common, but existing assessments lack sport-related applicability. We developed the Standardized Assessment of Reaction Time (StART) tool to emulate the simultaneous cognitive and motor function demands in sport, but its reliability is unestablished.

OBJECTIVES

To determine the intrarater, interrater, and test-retest reliability of StART and to examine the dual-task effect, time effect, and relationships between StART and computerized and laboratory-based functional reaction time assessments.

DESIGN

Prospective cohort study.

SETTING

Clinical laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty healthy, physically active individuals (age = 20.3 ± 1.8 years, females = 12, no concussion history = 75%).

MAIN OUTCOME MEASURE(S)

Participants completed the StART, computerized reaction time (Stroop task via CNS Vital Signs), and laboratory-based jump landing and cutting reaction time under single-task and dual-task (subtracting by 6s or 7s) cognitive conditions at 2 testing sessions a median of 7 days apart. We used intraclass correlation coefficients (ICCs), repeated-measure analysis of variance, and Pearson r correlations to address our aims.

RESULTS

Overall, good to strong interrater (ICC [2,k] range = 0.83-0.97), intrarater (ICC [3,k] range = 0.91-0.98), and test-retest (ICC [3,k] range = 0.69-0.89) reliability were observed. A significant reaction time assessment-by-cognitive condition interaction was present (P = .018, ηp2 = 0.14), with StART having the largest dual-task effect. Main time effects for dual-task conditions were seen across all reaction time assessments (mean difference = -25 milliseconds, P = .026, ηp2 = 0.08) with improved performance at the second testing session. No StART outcomes correlated with computerized reaction time (P > .05), although some correlated with single-task (r range = 0.42-0.65) and dual-task (r range = 0.19-0.50) laboratory cutting reaction time.

CONCLUSIONS

The StART demonstrated overall reliable performance relative to other reaction time measures. Reliability coupled with a strong dual-task effect indicates that StART is a valid measure for examining functional reaction time and may have future utility for sport-related concussion return-to-play decision-making.

Clinical Mental Health Measures and Prediction of Postconcussion Musculoskeletal Injury

CONTEXT

The rate of lower extremity musculoskeletal injury (LE MSK) is elevated after concussion; however, the underlying mechanism has not been elucidated. Physical characteristics have been investigated despite poorer mental health being a common postconcussion complaint and linked to MSKs.

OBJECTIVE

To evaluate the role of mental health as a predictor of postconcussion LE MSK.

DESIGN

Case-control study.

SETTING

Intercollegiate athletic training facility.

PATIENTS OR OTHER PARTICIPANTS

A total of 67 National Collegiate Athletic Association Division I student-athletes (n = 39 females) who had been diagnosed with a sport-related concussion.

MAIN OUTCOME MEASURE(S)

The Brief Symptom Inventory-18, Hospital Anxiety and Depression Scale, and Satisfaction With Life Scale (SWLS) measures were completed at baseline (preseason) and on the day participants were cleared for unrestricted return to play (RTP) after a concussion. Two binary logistic regressions were used to predict postconcussion LE MSK within a year, one for the baseline time point and the second for the RTP time point. A 2 (group: LE MSK, no LE MSK)-by-2 (time: baseline, RTP) repeated-measures analysis of variance compared performance between baseline and RTP.

RESULTS

Subsequent LE MSKs were sustained by 44 participants (65.7%). The only significant predictor of postconcussion LE MSK was the SWLS score at RTP, with Exp(B) = 0.64, indicating that an increased (improved) SWLS score was associated with a lower LE MSK rate. No significant interactions were present between mental health measures and subsequent MSK (P values = .105-.885).

CONCLUSIONS

Limited associations were evident between postconcussion LE MSK and scores on commonly used measures of anxiety, depression, and satisfaction with life. Reported increased satisfaction with life was associated with a decreased injury risk, which warrants further attention. Our results suggest that these measures of anxiety, depression, and satisfaction with life have limited value in assisting sports medicine clinicians with determining which student-athletes are at elevated risk of postconcussion LE MSK.

The impact of concussion on subsequent injury risk in elite junior Australian football athletes

OBJECTIVES

Concussion increases injury risk. However, this has not been investigated in junior Australian football and it is unknown whether the location, severity, and mechanism of subsequent injuries differ after concussion vs. non-concussion injury.

DESIGN

Prospective cohort.

METHODS

1455 elite adolescent male Australian footballers were tracked across seven seasons to determine whether subsequent injury risk was greater after concussion compared to non-concussion index injury using multilevel survival analysis. Mixed-effects logistic regression compared location and mechanism. Mixed-effects Poisson regression compared severity.

RESULTS

Of 1455 athletes, 632 were injured and included in subsequent-injury analysis. There were no differences in injury incidence after a concussion compared to upper- (hazard ratio = 1.0, 0.6 to 1.9, P = 0.892; trivial effect) and lower (hazard ratio = 1.1, 0.6 to 1.9, P = 0.810; trivial effect) index injury, or in location. Subsequent injuries were more likely to be contact-based after a non-concussion injury than concussion (odds ratio = 4.6, 1.3 to 16.0; P = 0.017; large effect). There was no difference in subsequent injury severity after lower- (3.4 ± 3.0 missed matches; incidence rate ratio = 1.4, 0.9 to 2.1; P ≤ 0.117; small effect) and upper-limb injuries (3.4 ± 3.1 missed matches; incidence rate ratio = 1.4, 0.9 to 2.2; P = 0.189; small effect) compared to concussion (2.4 ± 2.0 missed matches).

CONCLUSIONS

Subsequent injury risk, severity, and location in junior Australian football are similar following concussion compared to non-concussion index injuries, although contact injuries are less likely.

Concussion history is associated with increased lower-extremity injury incidence in Reserve Officers' Training Corps cadets

INTRODUCTION

Concussions have been associated with an increased risk of lower-extremity musculoskeletal injury (LE-MSI) in athletes and US Army soldiers, creating an added economic, physical and social burden. Yet, there is a paucity of evidence on this relationship among Reserve Officers' Training Corps (ROTC) cadets, a group which engages in activities with high-injury risk and will subsequently commission as active duty officers. This study aimed to examine the association between concussions and LE-MSI in ROTC cadets.

METHODS

125 (83 were male) Army and Air Force ROTC cadets (19.8±2.0 years) from two large state universities' Army and Air Force ROTC programmes participated in this study. Cadets completed a reliable injury history questionnaire to ascertain the following variables of interest: (1) any concussion history, (2) reported concussions, (3) undiagnosed concussions, and (4) potentially unrecognised concussion history and LE-MSI history (eg, ankle sprain, knee sprain or muscle strain). Data were analysed using a χ² test for association and binary logistic regression to determine ORs.

RESULTS

Cadets with any concussion history (n=42) had a significantly (p=0.035) higher association with LE-MSI (OR 2.47, 95% CI 1.05 to 5.83) than those without. Cadets who had a reported concussion (n=33) had a significantly (p=0.026) higher association with LE-MSI (OR 2.95, 95% CI 1.11 to 7.84) compared to cadets without.

CONCLUSIONS

ROTC cadets with a history of diagnosed concussion were more likely to have suffered an LE-MSI than cadets without a concussion history. ROTC cadre should be aware of this relationship and incorporate injury prevention protocols.

Kinesiophobia Is Related to Acute Musculoskeletal Injury Incidence Following Concussion

CONTEXT

Athletes with a history of sport concussion (SC) have an increased risk of musculoskeletal injury (MSK); however, the underlying mechanisms have yet to be determined. The purpose of our study was to evaluate kinesiophobia in college athletes with or without a time-loss MSK within 180 days of unrestricted return to play following a SC.

DESIGN

This was a retrospective cohort study within a sports medicine facility.

METHODS

Participants were eligible if they were diagnosed with a SC, completed the Tampa Scale of Kinesiophobia (TSK), and completed an unrestricted return to play. Fifty-six college athletes (40 men and 16 women) with an average age of 19.5 (1.25) years, height of 183.5 (10.45) cm, and mass of 94.72 (24.65) kg, were included in the study. MSK participants were matched to non-MSK participants 1:1. Demographic and TSK outcome scores were compared using independent t tests. The proportion of participants in each group who scored above the clinical threshold (TSK ≥ 37) was compared using a chi-square analysis. Alpha was set at α = .05.

RESULTS

The MSK group (31.2 [6.30]) reported similar TSK scores to the matched group (28.9 [3.34]; t54 = 1.70, P = .10, d = 0.45 [-0.08 to 0.97]). A greater proportion of athletes who were diagnosed with an MSK-reported scores above the cutoff (χ2[1] = 6.49, P = .01).

CONCLUSIONS

Athletes diagnosed with SC had similar kinesiophobia values regardless of MSK status. However, a higher proportion of athletes with a time-loss MSK injury reported a TSK score greater than the clinical cutoff. Our results suggest that factors such as kinesiophobia should be considered following a SC.

Lower Extremity Musculoskeletal Injuries After Concussion in Collegiate Student-Athletes

BACKGROUND

An association has been identified between concussion and lower extremity musculoskeletal injury (LEMSKI) after return to sports participation. However, the collegiate student-athlete studies have relied on relatively small single-institution studies, which limits generalizability.

PURPOSE

To assess odds of, and time to, LEMSKI after concussion in US collegiate athletes, using the National Collegiate Athletic Association (NCAA) Injury Surveillance Program (ISP).

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Data from the NCAA ISP during the 2010-2011 through 2019-2020 athletic seasons were considered for analysis. Frequency distributions were examined for details related to the initial and subsequent injuries (injuries to bone, bursa, joint, ligament, muscle, or tendon). Multivariable logistic regression models and random-effects Poisson regression models examined odds of time loss (TL) and non-time loss (NTL) LEMSKI after concussion, as well as the time interval between initial concussion and subsequent LEMSKI in a single athletic season, or initial musculoskeletal injury (MSKI) and subsequent LEMSKI in a single athletic season. Analyses were performed separately for football and other sports.

RESULTS

A total of 31,556 initial injuries were recorded (football: 11,900; other sports: 19,656), which were followed by 0 or 1 injury in the same season. Overall, first injury type was not a significant predictor of subsequent LEMSKI, although certain contrasts yielded significant estimates. In football, the odds of NTL LEMSKI were higher after concussion than after upper extremity MSKI (UEMSKI; adjusted odds ratio [OR_Adj], 1.56; 95% CI, 1.06-2.31). In football, the odds of TL LEMSKI were lower after concussion than after UEMSKI (OR_Adj, 0.71; 95% CI, 0.51-0.99). No other significant effect estimates were observed for football or other sports.

CONCLUSION

First injury type, either concussion or upper extremity, was not associated with an elevated risk of LEMSKI. Specifically, the results of this study did not identify an elevated odds of LEMSKI after a concussion. However, the authors observed greater odds of NTL LEMSKI and lower odds of TL LEMSKI in football.

Influential Factors and Preliminary Reference Data for a Clinically Feasible, Functional Reaction Time Assessment: The Standardized Assessment of Reaction Time

CONTEXT

Clinical reaction-time (RT) measures are frequently used when examining patients with concussion but do not correlate with functional movement RT. We developed the Standardized Assessment of RT (StART) to emulate the rapid cognitive demands and whole-body movement needed in sport.

OBJECTIVE

To assess StART differences across 6 cognitive-motor combinations, examine potential demographic and health history confounders, and provide preliminary reference data for healthy collegiate student-athletes.

DESIGN

Prospective, cross-sectional study.

SETTING

Clinical medicine facilities.

PATIENTS OR OTHER PARTICIPANTS

A total of 89 student-athletes (56 [62.9%] men, 33 [37.1%] women; age = 19.5 ± 0.9 years, height = 178.2 ± 21.7 cm, mass = 80.4 ± 24 kg; no concussion history = 64 [71.9%]).

MAIN OUTCOME MEASURE(S)

Student-athletes completed health history questionnaires and StART during preseason testing. The StART consisted of 3 movements (standing, single-legged balance, and cutting) under 2 cognitive states (single task and dual task [subtracting by 6's or 7's]) for 3 trials under each condition. The StART trials were calculated as milliseconds between penlight illumination and initial movement. We used a 3 × 2 repeated-measures analysis of variance with post hoc t tests and 95% CIs to assess StART cognitive and movement differences, conducted univariable linear regressions to examine StART performance associations, and reported StART performance as percentiles.

RESULTS

All StART conditions differed (P ≤ .03), except single-task standing versus single-task single-legged balance (P = .36). Every 1-year age increase was associated with an 18-millisecond (95% CI = 8, 27 milliseconds) slower single-task cutting RT (P < .001). Female athletes had slower single-task (15 milliseconds; 95% CI = 2, 28 milliseconds; P = .02) and dual-task (28 milliseconds; 95% CI = 2, 55 milliseconds; P = .03) standing RT than male athletes. No other demographic or health history factors were associated with any StART condition (P ≥ .056).

CONCLUSIONS

The StART outcomes were unique across each cognitive-motor combination, suggesting minimal subtest redundancy. Only age and sex were associated with select outcomes. The StART composite scores may minimize confounding factors, but future researchers should consider age and sex when providing normative data.

Single-Leg Hop Stabilization Throughout Concussion Recovery: A Preliminary Biomechanical Assessment

CONTEXT

Aberrant movement patterns among individuals with concussion history have been reported during sport-related movement. However, the acute postconcussion kinematic and kinetic biomechanical movement patterns during a rapid acceleration-deceleration task have not been profiled and leaves their progressive trajectory unknown. Our study aimed to examine single-leg hop stabilization kinematics and kinetics between concussed and healthy-matched controls acutely (≤7 d) and when asymptomatic (≤72 h of symptom resolution).

DESIGN

Prospective, cohort laboratory study.

METHODS

Ten concussed (60% male; 19.2 [0.9] y; 178.7 [14.0] cm; 71.3 [18.0] kg) and 10 matched controls (60% male; 19.5 [1.2] y; 176.1 [12.6] cm; 71.0 [17.0] kg) completed the single-leg hop stabilization task under single and dual task (subtracting by 6's or 7's) at both time points. Participants stood on a 30-cm tall box set 50% of their height behind force plates while in an athletic stance. A synchronized light was illuminated randomly, queuing participants to initiate the movement as rapidly as possible. Participants then jumped forward, landed on their nondominant leg, and were instructed to reach and maintain stabilization as fast as possible upon ground contact. We used 2 (group) × 2 (time) mixed-model analyses of variance to compare single-leg hop stabilization outcomes separately during single and dual task.

RESULTS

We observed a significant main group effect for single-task ankle plantarflexion moment, with greater normalized torque (mean difference = 0.03 N·m/body weight; P = .048, g = 1.18) for concussed individuals across time points. A significant interaction effect for single-task reaction time indicated that concussed individuals had slower performance acutely relative to asymptomatic (mean difference = 0.09 s; P = .015, g = 0.64), while control group performance was stable. No other main or interaction effects for single-leg hop stabilization task metrics were present during single and dual task (P ≥ .051).

CONCLUSIONS

Greater ankle plantarflexion torque coupled with slower reaction time may indicate stiff, conservative single-leg hop stabilization performance acutely following concussion. Our findings shed preliminary light on the recovery trajectories of biomechanical alterations following concussion and provide specific kinematic and kinetic focal points for future research.

Multi-domain assessment of sports-related and military concussion recovery: A scoping review

OBJECTIVE

This review explores the literature on multi-domain assessments used in concussion recovery, to inform evidence-based and ecologically valid return-to-play. It asks: What simultaneous, dynamic multi-domain paradigms are used to assess recovery of youth and adults following concussion?

METHODS

Five databases were searched (CINAHL, EMBASE, MEDLINE, PsycInfo, SPORTDiscus) until September 30, 2021. Records were limited to those published in peer-reviewed journals, in English, between 2002 and 2021. Included studies were required to describe the assessment of concussion recovery using dynamic paradigms (i.e., requiring sport-like coordination) spanning multiple domains (i.e., physical, cognitive, socio-emotional functioning) simultaneously.

RESULTS

7098 unique articles were identified. 64 were included for analysis, describing 36 unique assessments of 1938 concussed participants. These assessments were deconstructed into their constituent tasks: 13 physical, 17 cognitive, and one socio-emotional. Combinations of these "building blocks" formed the multi-domain assessments. Forty-six studies implemented level walking with a concurrent cognitive task. The most frequently implemented cognitive tasks were 'Q&A' paradigms requiring participants to answer questions aloud during a physical task.

CONCLUSIONS

A preference emerged for dual-task assessments, specifically combinations of level walking and Q&A tasks. Future research should balance ecological validity and clinical feasibility in multi-domain assessments, and work to validate these assessments for practice.

Relationship and Latent Factors Between Clinical Concussion Assessments and the Functional Standardized Assessment of Reaction Time (StART)

OBJECTIVE

To examine the relationships and latent factors within the Standardized Assessment of Reaction Time (StART), and between StART and current clinical assessments.

DESIGN

Cross-sectional study.

SETTING

Clinical medicine facility.

PARTICIPANTS

Eighty-nine healthy collegiate student-athletes (63% male, age: 19.5 ± 0.9 years, 28% ≥1 concussion history).

ASSESSMENT OF RISK FACTORS

Student-athletes completed StART and clinical assessments during preinjury testing.

MAIN OUTCOME MEASURES

Standardized Assessment of Reaction Time consisted of 3 conditions (standing, single-leg balance, cutting) under 2 cognitive states (single task and dual task) for 3 trials each condition. Clinical assessments were the Sport Concussion Assessment Tool (SCAT) symptom checklist, Standardized Assessment of Concussion (SAC), tandem gait (single task and dual task), and Immediate PostConcussion Assessment and Cognitive Testing (ImPACT). We used Pearson- r correlation coefficients and exploratory factor analysis (EFA) to examine relationships and latent factors between StART and clinical assessments.

RESULTS

Null to moderate correlations presented among the StART outcomes (r range: 0.06-0.70), and null to small correlations between StART and clinical assessments (r range: -0.16 to 0.34). The three-factor EFA for solely StART explained 70.6% total variance: functional movement (cutting), static dual-task (standing and single-leg balance), and static single task (standing and single-leg balance). The five-factor EFA for StART and clinical assessments explained 65.8% total variance: gait (single-task and dual-task tandem gait), functional movement (StART single-task and dual-task cutting), static dual-task (StART standing, single-leg balance), neurocognitive (ImPACT verbal memory, visual memory, visual-motor speed), and static single task (StART standing, single-leg balance). No other outcomes met the factor loading threshold.

CONCLUSIONS

StART displayed 3 distinct categories and had minimal redundancy within its subtests. StART did not meaningfully correlate with clinical assessments, suggesting that StART provides unique information by examining more functional, reactive movement.

Effect of Concussion on Reaction Time and Neurocognitive Factors: Implications for Subsequent Lower Extremity Injury

Background

Recent evidence has demonstrated that athletes are at greater risk for a lower extremity injury following a return-to-sport (RTS) after sport-related concussion (SRC). The reason for this is not completely clear, but it has been hypothesized that persistent deficits in neurocognitive factors may be a contributing factor.

Hypothesis/Purpose

This study assessed simple reaction time, processing speed, attention, and concentration in a group of athletes, post-concussion upon clearance for RTS for potential deficits that may result in slower reaction time, processing speed, attention, and concentration. The researchers hypothesized that the concussion group would demonstrate worse scores on both assessments compared to a sex-, age-, and sport-matched cohort.

Study Design

Case-controlled study.

Methods

Twelve participants who had suffered a SRC and eight healthy individuals who were matched to the concussed group by age, sex, and sport were evaluated. Those with a concussion had been cleared for RTS by a licensed healthcare provider. Each participant underwent neurocognitive tests that included a simple reaction time test (SRT) and the King-Devick Test (K-D). Independent t-tests were performed to compare the groups with significance set a priori at p<0.05.

Results

There was a significant difference (p =0.024) between groups for SRT with the concussed group demonstrating a better SRT than the control group. There were no significant differences (p =0.939) between the groups for the K-D.

Conclusion

With no significant differences between groups in the K-D assessment and, surprisingly, the concussed group having a better SRT compared to the healthy group, our hypothesis was not supported.

Clinical Relevance

These specific measures, compounded with extensive post-concussion time lapse until RTS clearance, may have limited capacity in revealing potential persistent deficits in relevant neurocognitive characteristics.

Level of Evidence

Level of Evidence 3.

Machine Learning for Predicting Lower Extremity Muscle Strain in National Basketball Association Athletes

Background

In professional sports, injuries resulting in loss of playing time have serious implications for both the athlete and the organization. Efforts to quantify injury probability utilizing machine learning have been met with renewed interest, and the development of effective models has the potential to supplement the decision-making process of team physicians.

Purpose/Hypothesis

The purpose of this study was to (1) characterize the epidemiology of time-loss lower extremity muscle strains (LEMSs) in the National Basketball Association (NBA) from 1999 to 2019 and (2) determine the validity of a machine-learning model in predicting injury risk. It was hypothesized that time-loss LEMSs would be infrequent in this cohort and that a machine-learning model would outperform conventional methods in the prediction of injury risk.

Study Design

Case-control study; Level of evidence, 3.

Methods

Performance data and rates of the 4 major muscle strain injury types (hamstring, quadriceps, calf, and groin) were compiled from the 1999 to 2019 NBA seasons. Injuries included all publicly reported injuries that resulted in lost playing time. Models to predict the occurrence of a LEMS were generated using random forest, extreme gradient boosting (XGBoost), neural network, support vector machines, elastic net penalized logistic regression, and generalized logistic regression. Performance was compared utilizing discrimination, calibration, decision curve analysis, and the Brier score.

Results

A total of 736 LEMSs resulting in lost playing time occurred among 2103 athletes. Important variables for predicting LEMS included previous number of lower extremity injuries; age; recent history of injuries to the ankle, hamstring, or groin; and recent history of concussion as well as 3-point attempt rate and free throw attempt rate. The XGBoost machine achieved the best performance based on discrimination assessed via internal validation (area under the receiver operating characteristic curve, 0.840), calibration, and decision curve analysis.

Conclusion

Machine learning algorithms such as XGBoost outperformed logistic regression in the prediction of a LEMS that will result in lost time. Several variables increased the risk of LEMS, including a history of various lower extremity injuries, recent concussion, and total number of previous injuries.

Concussion is not associated with elevated rates of lower-extremity musculoskeletal injuries in National Football League Players

OBJECTIVE

Emerging evidence has identified an ~2x elevated risk of musculoskeletal (MSK) injury in the year following a concussion. Most of these studies have examined a single college/university athletic department and may lack generalizability to professional sports. Therefore, the purpose of this study was to assess the odds of post-concussion MSK injury utilizing publicly available National Football League (NFL) injury reports.

METHODS

Concussions were identified through a review of published NFL injury reports during the 2015, 2016, and 2017 regular seasons. Concussed players were matched by team and position, and injuries were tracked for both groups for the remainder of the season. A chi-square analysis compared the frequency of MSK injury in both groups and a Cox Proportional Hazard model calculated the risk of sustaining a subsequent MSK injury.

RESULTS

There were 322 concussed NFL players who met inclusion criteria and were successfully matched. From the time of concussion through the remainder of the season, 21.4% of the concussed players were injured and 26.4% of control participants were injured. There was no difference in MSK injury rates (p = 0.166), and the relative risk ratio was 0.90 for subsequent injury in the concussion group. There was no difference in the time to event for subsequent MSK between the two groups (p = 0.123).

CONCLUSION

The primary finding of this study was no elevated risk of post-concussion MSK in NFL football players.

An 8-Week Neuromuscular Training Program After Concussion Reduces 1-Year Subsequent Injury Risk: A Randomized Clinical Trial

BACKGROUND

Existing data suggest that after concussion, athletes experience an increased risk of subsequent injury. Exploring methods that may reduce injury risk after successful postconcussion return to play may lead to new treatment approaches.

PURPOSE

To examine the efficacy of a neuromuscular training (NMT) intervention on acute sports-related time-loss injury over the subsequent year relative to standard of care.

STUDY DESIGN

Randomized clinical trial; Level of evidence, 1.

METHODS

A total of 27 youth athletes were assessed initially postconcussion (median, 7 days postconcussion; interquartile range [IQR], 5-10) and after return-to-play clearance (median, 40 days postconcussion; IQR, 15-52). After return-to-play clearance, they were randomly assigned to NMT intervention (n = 11; mean ± SD age, 14.7 ± 1.7 years; 36% female) or standard of care (n = 16; mean ± SD age, 15.3 ± 1.8 years; 44% female). The intervention (duration, 8 weeks; frequency, 2 times per week) included guided strength exercises with landing stabilization focus. Standard of care received no recommendations. For the subsequent year, athletes prospectively completed a monthly log of sports-related injuries and organized sports competitions.

RESULTS

During the first year after postconcussion return-to-play clearance, sports-related time-loss injuries were more common among standard of care relative to NMT intervention (75% [95% CI, 48%-93%] vs 36% [95% CI, 11%-69%]). After adjusting for age and sex, the hazard of subsequent injury in the standard-of-care group was 3.56 times (95% CI, 1.11-11.49; P = .0334) that of the NMT intervention group. Sports participation was similar between NMT intervention and standard of care during the year-long monitoring period (hours of organized sports per month; median, 12 [IQR, 2.6-32.1] vs 15.6 [IQR, 3.5-105.9]; P = .55). The age- and sex-adjusted incidence of injuries was 10.2 per 1000 competitive exposures (95% CI, 3.7-28.4) in the standard-of-care group as opposed to 3.4 per 1000 (95% CI, 0.9-13.4) in the NMT intervention group. After adjusting for age and sex, incidence of injuries was higher for standard of care vs NMT intervention (rate ratio, 2.96 [95% CI, 0.89-9.85]; P = .076).

CONCLUSION

Although preliminary, our findings suggest that an NMT intervention initiated after return-to-play clearance may significantly reduce sports-related time-loss injuries over the subsequent year.

REGISTRATION

NCT03917290 (ClinicalTrials.gov identifier).

Neuromuscular training after concussion to improve motor and psychosocial outcomes: A feasibility trial

OBJECTIVE

To determine the feasibility of an 8-week neuromuscular training program initiated upon return-to-play clearance following concussion.

DESIGN

Feasibility trial.

SETTING

A single sports medicine center.

PARTICIPANTS

We approached n = 54 patients; n = 32 agreed to participate (59%). N = 27 participants returned for their second visit at return-to-play clearance (84%) and were randomized to neuromuscular training (n = 13) or standard-of-care (n = 14).

MAIN OUTCOME MEASURES

Participants completed three assessments: within 14 days post-concussion, immediately after return-to-play clearance, and 8-weeks following return-to-play clearance. The intervention aimed to achieve positive neuromuscular adaptations and occurred 2x/week for 8 weeks under supervision.

RESULTS

N = 2 participants randomized to the intervention elected not to participate, both due to schedule conflicts (e.g., time required to meet with the study team). Participants began the intervention an average of 11 days after return-to-play clearance, the majority (91%) completed >75% of training sessions, and training sessions lasted an average of 18.2 ± 4.8 min. One participant stopped the intervention after 7 training sessions due to time availability.

CONCLUSION

It is feasible to initiate a neuromuscular training program for most athletes shortly after returning to play following concussion. Clinicians and researchers may consider this approach to mitigate the increased musculoskeletal injury risk for concussion patients returning to sports.

Persistent Visual and Vestibular Impairments for Postural Control Following Concussion: A Cross-Sectional Study in University Students

OBJECTIVE

To examine how concussion may impair sensory processing for control of upright stance.

METHODS

Participants were recruited from a single university into 3 groups: 13 participants (8 women, 21 ± 3 years) between 2 weeks and 6 months post-injury who initiated a return-to-play progression (under physician management) by the time of testing (recent concussion group), 12 participants (7 women, 21 ± 1 years) with a history of concussion (concussion history group, > 1 year post-injury), and 26 participants (8 women, 22 ± 3 years) with no concussion history (control group). We assessed sensory reweighting by simultaneously perturbing participants' visual, vestibular, and proprioceptive systems and computed center of mass gain relative to each modality. The visual stimulus was a sinusoidal translation of the visual scene at 0.2 Hz, the vestibular stimulus was ± 1 mA binaural monopolar galvanic vestibular stimulation (GVS) at 0.36 Hz, the proprioceptive stimulus was Achilles' tendon vibration at 0.28 Hz.

RESULTS

The recent concussion (95% confidence interval 0.078-0.115, p = 0.001) and the concussion history (95% confidence interval 0.056-0.094, p = 0.038) groups had higher gains to the vestibular stimulus than the control group (95% confidence interval 0.040-0.066). The recent concussion (95% confidence interval 0.795-1.159, p = 0.002) and the concussion history (95% confidence interval 0.633-1.012, p = 0.018) groups had higher gains to the visual stimulus than the control group (95% confidence interval 0.494-0.752). There were no group differences in gains to the proprioceptive stimulus or in sensory reweighting.

CONCLUSION

Following concussion, participants responded more strongly to visual and vestibular stimuli during upright stance, suggesting they may have abnormal dependence on visual and vestibular feedback. These findings may indicate an area for targeted rehabilitation interventions.

Impaired motor control after sport-related concussion could increase risk for musculoskeletal injury: Implications for clinical management and rehabilitation

This review presents a conceptual framework and supporting evidence that links impaired motor control after sport-related concussion (SRC) to increased risk for musculoskeletal injury. Multiple studies have found that athletes who are post-SRC have higher risk for musculoskeletal injury compared to their counterparts. A small body of research suggests that impairments in motor control are associated with musculoskeletal injury risk. Motor control involves the perception and processing of sensory information and subsequent coordination of motor output within the central nervous system to perform a motor task. Motor control is inclusive of motor planning and motor learning. If sensory information is not accurately perceived or there is interference with sensory information processing and cognition, motor function will be altered, and an athlete may become vulnerable to injury during sport participation. Athletes with SRC show neuroanatomic and neurophysiological changes relevant to motor control even after meeting return to sport criteria, including a normal neurological examination, resolution of symptoms, and return to baseline function on traditional concussion testing. In conjunction, altered motor function is demonstrated after SRC in muscle activation and force production, movement patterns, balance/postural stability, and motor task performance, especially performance of a motor task paired with a cognitive task (i.e., dual-task condition). The clinical implications of this conceptual framework include a need to intentionally address motor control impairments after SRC to mitigate musculoskeletal injury risk and to monitor motor control as the athlete progresses through the return to sport continuum.

Impaired eye tracking is associated with symptom severity but not dynamic postural control in adolescents following concussion

PURPOSE

The purpose of the study was to (1) examine the relationship between self-reported symptoms and concussion-related eye tracking impairments, and (2) compare gait performance between (a) adolescents with a concussion who have normal eye tracking, (b) adolescents with a concussion who have abnormal eye tracking, and (c) healthy controls.

METHODS

A total of 30 concussed participants (age: 14.4 ± 2.2 years, mean ± SD, 50% female) and 30 controls (age: 14.2 ± 2.2 years, 47% female) completed eye tracking and gait assessments. The BOX score is a metric of pupillary disconjugacy, with scores <10 classified as normal and ≥10 abnormal. Symptoms were collected using the Post-Concussion Symptom Scale (PCSS), and gait speed was measured with triaxial inertial measurement units. We conducted a linear regression to examine the relationship between PCSS and BOX scores and a two-way mixed effects analysis of variance to examine the effect of group (abnormal BOX, normal BOX, and healthy control) on single- and dual-task gait speed.

RESULTS

There was a significant association between total PCSS score and BOX score in the concussion group (β = 0.16, p = 0.004, 95% confidence interval (95%CI): 0.06‒0.27), but not in the control group (β = 0.21, p = 0.08, 95%CI: -0.03 to 0.45). There were no significant associations between PCSS symptom profiles and BOX scores in the concussion or control groups. There were also no significant differences in single-task (Abnormal: 1.00 ± 0.14 m/s; Normal: 1.11 ± 0.21 m/s; Healthy: 1.14 ± 0.18 m/s; p = 0.08) or dual-task (Abnormal: 0.77 ± 0.15 m/s; Normal: 0.84 ± 0.21 m/s; Healthy: 0.90 ± 0.18 m/s; p = 0.16) gait speed.

CONCLUSION

The concussed group with impaired eye tracking reported higher total symptom severity, as well as worse symptom severity across the 5 PCSS symptom domain profiles. However, eye tracking deficits did not appear to be driven by any particular symptom domain. While not statistically significant, the slower gait speeds in those with abnormal BOX scores may still be clinically relevant since gait-related impairments may persist beyond clinical recovery.

Sensitivity and Specificity of a Multimodal Approach for Concussion Assessment in Youth Athletes

CONTEXT

Current international consensus endorses a multimodal approach to concussion assessment. However, the psychometric evaluation of clinical measures used to identify postconcussion performance deficits once an athlete is asymptomatic remains limited, particularly in the pediatric population.

OBJECTIVE

To describe and compare the sensitivity and specificity of a multimodal assessment battery (balance, cognition, and upper and lower body strength) versus individual clinical measures at discriminating between concussed youth athletes and noninjured controls when asymptomatic.

DESIGN

Prospective cohort study.

SETTING

Hospital laboratory setting.

PARTICIPANTS

A total of 32 youth athletes with a concussion and 32 matched (age and sex) noninjured control participants aged 10-18 years.

INTERVENTION(S)

Participants were administered preinjury (baseline) assessments of cognition (Immediate Post-Concussion Assessment and Cognitive Testing [ImPACT]), balance (BioSway), and upper and lower body strength (grip strength and standing long jump). Assessments were readministered when concussed participants reported symptom resolution (asymptomatic time point). Noninjured control participants were reassessed using the same time interval as their concussion matched pair. Sensitivity and specificity were calculated using standardized regression-based methods and receiver operating characteristic curves.

MAIN OUTCOME MEASURES

Outcome measures included baseline and postinjury ImPACT, BioSway, grip strength, and standing long jump scores.

RESULTS

When asymptomatic, declines in performance on each individual clinical measure were seen in 3% to 22% of the concussion group (sensitivity = 3%-22%) compared with 3% to 13% of the noninjured control group (specificity = 87%-97%) (90% confidence interval). The multimodal battery of all combined clinical measures yielded a sensitivity of 41% and a specificity of 77% (90% confidence interval). Based on discriminative analyses, the multimodal approach was statistically superior compared with an individual measures approach for balance and upper and lower body strength, but not for cognition.

CONCLUSIONS

Results provide a foundation for understanding which domains of assessment (cognition, balance, and strength) may be sensitive and specific to deficits once symptoms resolve in youth athletes. More work is needed prior to clinical implementation of a preinjury (baseline) to postinjury multimodal approach to assessment following concussion in youth athletes.

Impairments in Dynamic Postural Control across Concussion Clinical Milestones

The aim of this study was to assess gait initiation (GI) performance longitudinally across clinical concussion recovery milestones through return to participation (RTP). We recruited 54 collegiate student-athletes, 27 with concussions and 27 matched controls (15 female and 12 male per group). Participants performed five trials of GI at baseline and again at five post-concussion clinical milestones: 1) Acute, the day clinical tests achieved baseline values on the 2) Balance Error Scoring System (BESS), 3) Immediate Post-Concussion Assessment and Cognitive Test ImPACT, 4) Asymptomatic, and 5) RTP Day. GI performance on six outcome measures (anterior/posterior and medial/lateral center of pressure displacements and velocities during the anticipatory postural adjustment [APA] phase and initial step length and velocity) with repeated-measures mixed model and pair-wise post hoc. A reliable change index (RCI) was calculated, and post-concussion participant's performance was compared to the RCI at milestones. There were significant interactions for APA posterior and lateral displacement, APA posterior velocity, step length, and step velocity. The post-hoc tests identified significant deficits across clinical milestones and at RTP for APA posterior and lateral displacement, step length, and step velocity. There were no post-hoc differences for any outcome measure in the control group. At RTP, 85.2-88.9% of concussion participants had at least one outcome measure which exceeded the 80% or 95% RCI. The primary finding of this study was persistent impairments in dynamic postural control, suggesting ongoing neurophysiological impairment despite clinical recovery. These results suggest that collegiate student-athletes may be RTP before neurophysiological recovery and potentially exposing themselves to elevated risk of recurrent concussion or subsequent musculoskeletal injury.

Dual-Task Gait Stability after Concussion and Subsequent Injury: An Exploratory Investigation

Persistent gait alterations can occur after concussion and may underlie future musculoskeletal injury risk. We compared dual-task gait stability measures among adolescents who did/did not sustain a subsequent injury post-concussion, and uninjured controls. Forty-seven athletes completed a dual-task gait evaluation. One year later, they reported sport-related injuries and sport participation volumes. There were three groups: concussion participants who sustained a sport-related injury (n = 8; age =15.4 ± 3.5 years; 63% female), concussion participants who did not sustain a sport-related injury (n = 24; 14.0 ± 2.6 years; 46% female), and controls (n = 15; 14.2 ± 1.9 years; 53% female). Using cross-recurrence quantification, we quantified dual-task gait stability using diagonal line length, trapping time, percent determinism, and laminarity. The three groups reported similar levels of sports participation (11.8 ± 5.8 vs. 8.6 ± 4.4 vs. 10.9 ± 4.3 hours/week; p = 0.37). The concussion/subsequent injury group walked slower (0.76 ± 0.14 vs. 0.65 ± 0.13 m/s; p = 0.008) and demonstrated higher diagonal line length (0.67 ± 0.08 vs. 0.58 ± 0.05; p = 0.02) and trapping time (5.3 ± 1.5 vs. 3.8 ± 0.6; p = 0.006) than uninjured controls. Dual-task diagonal line length (hazard ratio =1.95, 95% CI = 1.05–3.60), trapping time (hazard ratio = 1.66, 95% CI = 1.09–2.52), and walking speed (hazard ratio = 0.01, 95% CI = 0.00–0.51) were associated with subsequent injury. Dual-task gait stability measures can identify altered movement that persists despite clinical concussion recovery and is associated with future injury risk.

Reactive Postural Responses After Mild Traumatic Brain Injury and Their Association With Musculoskeletal Injury Risk in Collegiate Athletes: A Study Protocol

Background: Deficits in neuromuscular control are widely reported after mild traumatic brain injury (mTBI). These deficits are speculated to contribute to the increased rate of musculoskeletal injuries after mTBI. However, a concrete mechanistic connection between post-mTBI deficits and musculoskeletal injuries has yet to be established. While impairments in some domains of balance control have been linked to musculoskeletal injuries, reactive balance control has received little attention in the mTBI literature, despite the inherent demand of balance recovery in athletics. Our central hypothesis is that the high rate of musculoskeletal injuries after mTBI is in part due to impaired reactive balance control necessary for balance recovery. The purpose of this study is to (1) characterize reactive postural responses to recover balance in athletes with recent mTBI compared to healthy control subjects, (2) determine the extent to which reactive postural responses remain impaired in athletes with recent mTBI who have been cleared to return to play, and (3) determine the relationship between reactive postural responses and acute lower extremity musculoskeletal injuries in a general sample of healthy collegiate athletes.

Methods: This two-phase study will take place at the University of Utah in coordination with the University of Utah Athletics Department. Phase 1 will evaluate student-athletes who have sustained mTBI and teammate-matched controls who meet all the inclusion criteria. The participants will be assessed at multiple time points along the return-to-play progress of the athlete with mTBI. The primary outcome will be measures of reactive postural response derived from wearable sensors during the Push and Release (P&R) test. In phase 2, student-athletes will undergo a baseline assessment of postural responses. Acute lower extremity musculoskeletal injuries for each participant will be prospectively tracked for 1 year from the date of first team activity. The primary outcomes will be the measures of reactive postural responses and the time from first team activity to lower extremity injury.

Discussion: Results from this study will further our understanding of changes in balance control, across all domains, after mTBI and identify the extent to which postural responses can be used to assess injury risk in collegiate athletes.