The Interval Between Concussions Does Not Influence Time to Asymptomatic or Return to Play: A CARE Consortium Study.

INTRODUCTION: The purpose of this study was to determine if the time interval between two concussive events influences the number of days to asymptomatic status, days to return to play, or performance on common post-concussion assessments following the second concussion. METHODS: Data from 448 collegiate athletes and service academy cadets with two concussions (time between concussions: median 295.0 days [interquartile range: 125.0-438.2]), 40.0% female) were analyzed from Concussion Assessment Research and Education (CARE) Consortium institutions between 2014 and 2020. Days between concussions was the primary predictor variable. Primary outcome measures included time to asymptomatic and time to return to play following the second concussion. Secondary outcome measures included total number of symptoms, total symptom severity, Balance Error Scoring System total score, and Standardized Assessment of Concussion total score within 48 h of their second concussion. RESULTS: Time between concussions did not significantly contribute to the multivariate time to asymptomatic (p = 0.390), time to return to play (p = 0.859), or the secondary outcomes (p-range = 0.165-0.477) models. Time to asymptomatic (p = 0.619) or return to play (p = 0.524) did not differ between same-season and different-season concussions. Sex significantly contributed to the return to play (p = 0.005) multivariate model. Delayed symptom onset and immediate removal from play/competition significantly contributed to the total number of symptoms (p = 0.001, p = 0.014) and symptom severity (p = 0.011, p = 0.022) multivariate models. CONCLUSION: These results suggest that in a population with a large period between injuries, the time between concussions may not be relevant to clinical recovery.

Optimizing Concussion Care Seeking: Connecting Care-Seeking Behaviors and Neurophysiological States Through Blood Biomarkers.

BACKGROUND: Timely and appropriate medical care after concussion presents a difficult public health problem. Concussion identification and treatment rely heavily on self-report, but more than half of concussions go unreported or are reported after a delay. If incomplete self-report increases exposure to harm, blood biomarkers may objectively indicate this neurobiological dysfunction. PURPOSE/HYPOTHESIS: The purpose of this study was to compare postconcussion biomarker levels between individuals with different previous concussion diagnosis statuses and care-seeking statuses. It was hypothesized that individuals with undiagnosed concussions and poorer care seeking would show altered biomarker profiles. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Blood samples were collected from 287 military academy cadets and collegiate athletes diagnosed with concussion in the Advanced Research Core of the Concussion Assessment, Research and Education Consortium. The authors extracted each participant's self-reported previous concussion diagnosis status (no history, all diagnosed, ≥1 undiagnosed) and whether they had delayed or immediate symptom onset, symptom reporting, and removal from activity after the incident concussion. The authors compared the following blood biomarkers associated with neural injury between previous concussion diagnosis status groups and care-seeking groups: glial fibrillary acidic protein, ubiquitin c-terminal hydrolase-L1 (UCH-L1), neurofilament light chain (NF-L), and tau protein, captured at baseline, 24 to 48 hours, asymptomatic, and 7 days after unrestricted return to activity using tests of parallel profiles. RESULTS: The undiagnosed previous concussion group (n = 21) had higher levels of NF-L at 24- to 48-hour and asymptomatic time points relative to all diagnosed (n = 72) or no previous concussion (n = 194) groups. For those with delayed removal from activity (n = 127), UCH-L1 was lower at 7 days after return to activity than that for athletes immediately removed from activity (n = 131). No other biomarker differences were observed. CONCLUSION: Individuals with previous undiagnosed concussions or delayed removal from activity showed some different biomarker levels after concussion and after clinical recovery, despite a lack of baseline differences. This may indicate that poorer care seeking can create neurobiological differences in the concussed brain.

Trunk and lower extremity biomechanics differ between 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. Previous landing biomechanics research post-concussion has 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 without a concussion history. DESIGN: Cross-sectional. SETTING: Biomechanics laboratory. PARTICIPANTS: Our study included 26 athletes with (age:19.0±1.3years, BMI:22.6±2.0kg/m2, time since most recent concussion: median=37.5 months [interquartile range (25.0, 65.8)]), and 38 athletes without (age:19.0±1.1years, BMI:22.1±1.8kg/m2) a concussion history. MAIN OUTCOME MEASURES: Peak kinetics (vertical ground reaction force, vertical loading rate, external knee abduction moment, external knee flexion moment) and kinematics (trunk flexion angle, trunk lateral bending angle, dorsiflexion angle, knee flexion angle, knee abduction angle, hip flexion angle) were obtained during the eccentric portion of the task. Separate 2 (group) × 2 (limb) between-within analyses of covariance compared outcomes between groups. We covaried for time since most recent concussion and limb which had a history of musculoskeletal injury. RESULTS: Athletes with a concussion history displayed a greater nondominant knee abduction angle compared to their dominant limb (p=0.010, np2=0.107) and athletes without a concussion history nondominant limb (p=0.023, np2=0.083) during the jump landing. Athletes with a concussion history displayed less trunk lateral bending during cutting compared with athletes without a concussion history (p=0.005, np2=0.126). CONCLUSIONS: Our results indicate landing biomechanics are different between female athletes with and without a concussion history. This may be due to impairments in neuromuscular control post-concussion which may ultimately increase the risk of subsequent lower extremity injury, although further research is warranted given the cross-sectional nature of our study.

Longitudinal Assessment of Postconcussion Driving: Evidence of Acute Driving Impairment.

BACKGROUND: Current medical practices and recommendations largely ignore the safety of postconcussion driving, even though commonly used measures of neurocognition, balance, and vestibulo-ocular function show impairment. PURPOSE: To compare simulated driving between patients with concussion and controls throughout concussion recovery using a case-control design. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: A total of 26 concussed and 23 control Division I collegiate athletes completed a driving simulation assessment at 3 time points (within 72 hours, asymptomatic, and return to sport). Cumulative driving simulation outcome variables included total number of collisions, speed exceedances, stop signs missed, lane excursions, total drive time, percentage of time over the speed limit, and percentage of time out of the lane. The mean speed, standard deviation of speed (SDS), lateral lane position, and standard deviation of lateral lane position (SDLP) were examined for each of the 11 drive segments. Outcomes were compared using generalized linear mixed models with random intercepts by participant with Poisson or normal distributions. RESULTS: Within 72 hours of injury, the concussion group committed more lane excursions (median difference, 2; P = .003), exhibited greater SDS while avoiding a child pedestrian crossing the road (Cohen d = 0.73; P = .011), drove ~7 inches (~18 cm) closer to the centerline during a residential left curve (d = 0.90; P = .015), and had greater SDLP while navigating around a car crash compared with controls (d = 0.72; P = .016). When asymptomatic, the concussion group committed fewer speed exceedances (median difference, 2; P = .002) and had lower SDLP while navigating through a traffic light compared with controls (d = 0.60; P = .045). No differences were evident at return to sport. Groups did not differ in total collisions at any time point. CONCLUSION: The concussion group showed more impaired driving patterns within 72 hours of injury, drove more conservatively once asymptomatic, and had similar driving performance at the time they returned fully to sport. Clinicians should consider these findings when discussing driving with patients acutely after concussion. Further research is needed to determine whether on-road collision risk is elevated after concussion.

Cognition Uniquely Influences Dual-Task Tandem Gait Performance Among Athletes With a Concussion History.

BACKGROUND: After a concussion, there are unique associations between static balance and landing with cognition. Previous research has explored these unique correlations, but the factor of time, dual-task, and different motor tasks leave gaps within the literature. The purpose of this study was to determine the associations between cognition and tandem gait performance. HYPOTHESIS: We hypothesized that athletes with a concussion history would display stronger associations compared with athletes without a concussion history between cognition and tandem gait. STUDY DESIGN: Cross-sectional. LEVEL OF EVIDENCE: Level 3. METHODS: A total of 126 athletes without (56.3% female; age, 18.8 ± 1.3 years; height, 176.7 ± 12.3 cm; mass, 74.8 ± 19.0 kg) and 42 athletes with (40.5% female; age, 18.8 ± 1.3 years; height, 179.3 ± 11.9 cm; mass, 81.0 ± 25.1 kg) concussion history participated. Cognitive performance was assessed with CNS Vital Signs. Tandem gait was performed on a 3-meter walkway. Dual-task tandem gait included a concurrent cognitive task of serial subtraction, reciting months backward, or spelling words backward. RESULTS: Athletes with a concussion history exhibited a larger number of significant correlations compared with athletes without a concussion history for cognition and dual-task gait time (4 significant correlations: rho-range, -0.377 to 0.358 vs 2 significant correlations: rho, -0.233 to 0.179) and dual-task cost gait time (4 correlations: rho range, -0.344 to 0.392 vs 1 correlation: rho, -0.315). The time between concussion and testing did significantly moderate any associations (P = 0.11-0.63). Athletes with a concussion history displayed better dual-task cost response rate (P = 0.01). There were no other group differences for any cognitive (P = 0.13-0.97) or tandem gait (P = 0.20-0.92) outcomes. CONCLUSION: Athletes with a concussion history display unique correlations between tandem gait and cognition. These correlations are unaffected by the time since concussion. CLINICAL RELEVANCE: These unique correlations may represent shared neural resources between cognition and movement that are only present for athletes with a concussion history. Time does not influence these outcomes, indicating the moderating effect of concussion on the correlations persists long-term after the initial injury.

Preinjury Measures Do Not Predict Future Concussion Among Collegiate Student-Athletes: Findings From the CARE Consortium.

ABSTRACT: This prospective cohort study aimed to determine whether preinjury characteristics and performance on baseline concussion assessments predicted future concussions among collegiate student-athletes. Participant cases (concussed = 2529; control = 30,905) completed preinjury: demographic forms (sport, concussion history, sex), Immediate Post-Concussion Assessment and Cognitive Test, Balance Error Scoring System, Sport Concussion Assessment Tool symptom checklist, Standardized Assessment of Concussion, Brief Symptom Inventory-18 item, Wechsler Test of Adult Reading, and Brief Sensation Seeking Scale. We used machine-learning logistic regressions with area under the curve, sensitivity, and positive predictive values statistics for univariable and multivariable analyses. Primary sport was determined to be the strongest univariable predictor (area under the curve = 64.3% ± 1.4, sensitivity = 1.1% ± 1.4, positive predictive value = 4.9% ± 6.5). The all-predictor multivariable model was the strongest (area under the curve = 68.3% ± 1.6, sensitivity = 20.7% ± 2.7, positive predictive value = 16.5% ± 2.0). Despite a robust sample size and novel analytical approaches, accurate concussion prediction was not achieved regardless of modeling complexity. The strongest positive predictive value (16.5%) indicated only 17 of every 100 individuals flagged would experience a concussion. These findings suggest preinjury characteristics or baseline assessments have negligible utility for predicting subsequent concussion. Researchers, healthcare providers, and sporting organizations therefore should not use preinjury characteristics or baseline assessments for future concussion risk identification at this time.

Early Exercise is Associated with Faster Concussion Recovery Among Collegiate Athletes: Findings from the NCAA-DoD CARE Consortium.

BACKGROUND: Growing evidence indicates early exercise may improve symptoms and reduce clinical recovery time after concussion, but research examining collegiate student-athletes is scarce. OBJECTIVE: The aim of this study was to compare symptom recovery time, clinical recovery time, and persisting post-concussion symptom (i.e., symptoms ≥ 28 days) prevalence by the timing of light exercise initiation before the graded return to play (RTP) protocol among concussed participants. METHODS: Collegiate student-athletes (n = 1228; age 18.4 ± 0.9 years; 56.5% male, 76.3% division I; 33.7% ≥ 1 prior concussion) across 30 institutions enrolled in the CARE Consortium completed post-concussion assessments and were monitored over time. Symptom recovery (days from injury to symptom resolution) and clinical recovery (days from injury to return to play protocol completion) was determined by the student-athletes' clinicians. Student-athletes were categorized by timing of light exercise initiation. Early (< 2 days post-concussion; n = 161), typical (3-7 days post-concussion; n = 281), and late exercise (≥ 8 days post-concussion; n = 169) groups were compared with the no-exercise group (n = 617; i.e., did not exercise prior to beginning the RTP protocol) for all analyses. Multivariable Cox regression models with hazard ratios (HR) and survival curves and a multivariable binomial regression model with prevalence ratios (PR) compared recovery outcomes between exercise groups while accounting for covariates. RESULTS: Compared to the no-exercise group, the early exercise group was 92% more probable to experience symptom recovery (HR 1.92; 95% CI 1.57-2.36), 88% more probable to reach clinical recovery (HR 1.88; 95% CI 1.55-2.28) and took a median of 2.4 and 3.2 days less to recover, respectively. The late exercise group relative to the no-exercise group was 57% less probable to reach symptom recovery (HR 0.43; 95% CI 0.35-0.53), 46% less probable to achieve clinical recovery (HR 0.54; 95% CI 0.45-0.66) and took 5.3 days and 5.7 days more to recover, respectively. The typical exercise group did not differ in hazard for symptom or clinical recovery (p ≥ 0.329) compared with the no-exercise group. The prevalence of persisting post-concussion symptoms in the combined sample was 6.6%. Early exercise had 4% lower prevalence (PR 0.96, 95% CI 0.94-0.99) and typical exercise had 3% lower prevalence (PR 0.97, 95% CI 0.94-0.99) of persisting post-concussion symptoms, while the late exercise group had an elevated prevalence (PR 1.11, 95% CI 1.04-1.18) compared with the no-exercise group. CONCLUSION: Exercise < 2 days post-concussion was associated with more probable and faster symptom and clinical recovery, and lower persisting post-concussion symptom prevalence. When considering our findings and existing literature, qualified clinicians may implement early exercise into their clinical practice to provide therapeutic treatment and improve student-athlete recovery.

Quantifying head impact biomechanical differences between commonly employed cleaning levels: a critical research interpretation consideration.

INTRODUCTION: Wearable accelerometry devices quantify on-field frequency and severity of head impacts to further improve sport safety. Commonly employed post-data collection cleaning techniques may affect these outcomes. OBJECTIVE: Our purpose was to compare game impact rates and magnitudes between three different cleaning levels (Level-1: impacts recorded within start and end times, Level-2: impacts during pauses/breaks removed, Level-3: video verified) for male youth tackle football. METHODS: Participants (n = 23, age = 10.9 ± 0.3 yrs, height = 150.0 ± 8.3 cm, mass = 41.6 ± 8.4 kg) wore Triax SIM-G sensors throughout Fall 2019. Impact rates, ratios (IRRs), and 95% confidence intervals (95%CI) were used to compare levels. Random-effects general linear models were used to compare peak linear acceleration (PLA;g) and angular velocity (PAV;rads/s). RESULTS: Level-1 resulted in higher impact rates (4.57; 95%CI = 4.14-5.05) compared to Level-2 (3.09; 95%CI = 2.80-3.42; IRR = 1.48; 95%CI = 1.34-1.63) and Level-3 datasets (2.56; 95%CI = 2.30-2.85; IRR = 1.78; 95%CI = 1.60-1.98). Level-2 had higher impact rates compared to Level-3 (1.21; 95%CI = 1.08-1.35). Level-1 resulted in higher PAV than Level-2 and Level-3 (p < 0.001) datasets. PLA did not differ across datasets (p = 0.296). CONCLUSIONS: Head impact data should be filtered of pauses/breaks, and does not substantially differ outcome estimates compared to time-intensive video verification.

Motor vehicle crash concussion mechanism displays a greater total number of symptoms and greater affective symptom severity but no neurocognitive differences compared with sport-related concussion mechanism.

Previous research among adolescents has shown differences in symptoms and neurocognitive performance between sport-related (SRC) and motor vehicle crash (MVC) concussion mechanisms. Limited research has focused on young adults. The purpose of our study was to compare symptoms, balance, and neurocognitive performance between SRC and MVC mechanisms in young adults. Forty-three (58.1% female, age = 25.5 ± 3.2 years, days since concussion = 12.8 ± 12.7) and 26 (76.9% female, age = 24.1 ± 5.6 years, days since concussion = 12.6 ± 8.3) individuals with an SRC and MVC mechanism, respectively, participated. Primary outcome measures included the total number, severity, cluster (disorientation, migraine, lethargy, and affective) of post-concussion symptoms endorsed, Balance Error Scoring System (BESS), and CNS Vital Signs scores. Clusters are subgroups of symptoms used for targeted rehabilitation. We used independent t-tests and Mann-Whitney U tests to compare symptoms, BESS, and neurocognitive performance. Cliff's Delta effect size was interpreted as negligible (<0.15), small (0.15-0.33), medium (0.34-0.47), and large (≥0.48). There were no group differences for any demographic factors or preexisting conditions (p-range = 0.112-0.991). Participants with an MVC mechanism reported a greater number of total post-concussion symptoms (p = 0.025, Cliff's Delta = 0.32) and a more severe affective symptom cluster (p = 0.010, Cliff's Delta = 0.37). There were no group differences for BESS or neurocognitive performance after correcting for multiple comparisons. The MVC mechanism resulted in a greater total symptom burden relative to the SRC mechanism. Medical practitioners and individuals experiencing a concussion should know that concussions are heterogeneous within and across various mechanisms.

Computerized and functional reaction time in varsity-level female collegiate athletes with and without a concussion history.

OBJECTIVES: To 1) determine the association between computerized and functional reaction time, and 2) compare functional reaction times between female athletes with and without a concussion history. DESIGN: Cross-sectional study. METHODS: Twenty female college athletes with concussion history (age = 19.1 ±â€¯1.5 years, height = 166.9 ±â€¯6.7 cm, mass = 62.8 ±â€¯6.9 kg, median total concussion = 1.0 [interquartile range = 1.0, 2.0]), and 28 female college athletes without concussion history (age = 19.1 ±â€¯1.0 years, height = 172.7 ±â€¯8.3 cm, mass = 65.4 ±â€¯8.4 kg). Functional reaction time was assessed during jump landing and dominant and non-dominant limb cutting. Computerized assessments included simple, complex, Stroop, and composite reaction times. Partial correlations investigated the associations between functional and computerized reaction time assessments while covarying for time between computerized and functional reaction time assessments. Analysis of covariance compared functional and computerized reaction time, covarying for time since concussion. RESULTS: There were no significant correlations between functional and computerized reaction time assessments (p-range = 0.318 to 0.999, partial correlation range = -0.149 to 0.072). Reaction time did not differ between groups during any functional (p-range = 0.057 to 0.920) or computerized (p-range = 0.605 to 0.860) reaction time assessments. CONCLUSIONS: Post-concussion reaction time is commonly assessed via computerized measures, but our data suggest computerized reaction time assessments are not characterizing reaction time during sport-like movements in varsity-level female athletes. Future research should investigate confounding factors of functional reaction time.

Investigating post-mild traumatic brain injury neuromuscular function and musculoskeletal injury risk: A protocol for a prospective, observational, case-controlled study in service members and active individuals.

INTRODUCTION: Musculoskeletal injury (MSKI) risk is increased following mild traumatic brain injury (mTBI). Increased MSKI risk is present up to 2 years following post-mTBI return-to-duty/activity relative to both non-mTBI peers and to their pre-mTBI selves across a range of populations, including military service members, and professional, college and high school athletes. Despite the well documented increased post-mTBI MSKI risk, the underlying neuromuscular mechanisms contributing to this increased risk have yet to be definitively determined. A number of potential mechanisms have been suggested (eg, aberrant kinematics, dynamic balance impairments, lower voluntary muscle activation), but none have been confirmed with a comprehensive, prospective study. This study aims to: (1) elucidate the neuromuscular control mechanisms following mTBI that contribute to increased MSKI risk, and (2) prospectively track patient outcomes (up to 12 months; MSKI occurrences and patient-reported outcomes (PRO)). METHODS AND ANALYSIS: This is a multicentre prospective, case-matched control observational study to identify deficiencies in neuromuscular function following mTBI that may contribute to increased MSKI risk. Participants (aim to recruit 148, complete data collection on 124) will be classified into two cohorts; mTBI and control. All participants will undergo longitudinal (initial, 6 weeks post-initial, 12 weeks post-initial) comprehensive three-dimensional biomechanical (jump-landing; single leg hop; cut; gait), neuromuscular (interpolated twitch technique, muscular ramp contraction) and sensory (joint repositioning; light touch sensation) assessments to elucidate the underlying neuromuscular control mechanisms post-mTBI that may contribute to increased MSKI. Occurrences of MSKI and PROs (National Institutes of Health Patient-Reported Outcome Measurement Information System: Physical Function, Pain Interference, Depression, Anxiety; Brief Resilience Scale; Tampa Scale of Kinesiophobia), will be tracked monthly (up to 1 year) via electronic data capture platforms. ETHICS AND DISSEMINATION: The study received approval from the Walter Reed National Military Medical Center Institutional Review Board. Results will be made available to the associated funding agency and other researchers via conference proceedings and journal articles. TRIAL REGISTRATION NUMBER: NCT05122728.

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.

Youth Tackle Football Head-Impact Estimation by Players and Parents: Is the Perception the Reality?

CONTEXT: With growing concerns surrounding exposure to head impacts in youth tackle football, players and parents must understand the exposure level when assenting and consenting to participate. OBJECTIVE: To determine whether youth football players and parents could estimate on-field head-impact frequency, severity, and location. DESIGN: Prospective cohort study. SETTING: Football field. PATIENTS OR OTHER PARTICIPANTS: We administered a 10-question head-impact estimation tool to parents (n = 23; mean age = 36.5 years [95% CI = 31.7, 37.3 years]) and players (n = 16 boys; mean age = 11.1 years [95% CI = 10.3, 11.8 years]). MAIN OUTCOME MEASURE(S): Player on-field head-impact exposure was captured using the Triax SIM-G system. We determined the accuracy between player and parent estimates relative to on-field head-impact exposures using κ and weighted κ values. RESULTS: Youth tackle football players and parents did not accurately estimate on-field head-impact frequency (κ range = -0.09 to 0.40), severity (κ range = -0.05 to 0.34), or location (κ range = -0.30 to 0.13). Players and parents overestimated head-impact frequency in practices but underestimated the frequency in games. Both groups overestimated head-impact severity, particularly in games. Most players and parents underestimated the number of head impacts to the top of the head, particularly during practices. CONCLUSIONS: Underestimations of head-impact frequency in games and to the top of the head suggest that informed consent processes aimed at educating players and parents should be improved. Overestimations of head-impact frequency in practices and severity may explain declining rates of youth tackle football participation.

Lower Extremity Somatosensory Function Throughout Concussion Recovery: A Prospective Cohort Study.

OBJECTIVE: Balance impairments may suggest somatosensory disruption beyond concussion clinical recovery, but somatosensory subsystems have never been directly assessed. Our objective was to examine somatosensory function between individuals with a concussion and healthy matched-controls at acute (<7 days) and asymptomatic (<72 hours of being symptom-free) time points. SETTING: Laboratory. PARTICIPANTS: Participants with a concussion and matched controls ( n = 24; 58% male, age: 19.3 ± 1.1 years, mass: 70.3 ± 16.4 kg, height: 177.3 ± 12.7 cm). DESIGN: Prospective cohort. MAIN MEASURES: Somatosensory assessments on the dominant limb at both time points included: (1) plantar touch sensation threshold via Semmes-Weinstein monofilaments, (2) plantar pressure pain threshold via algometry, and (3) knee absolute passive joint repositioning (PJR) error via Biodex across 3 arcs (105°-75°, 30°-60°, 90°-45° knee-flexion). We used mixed-model analyses of variance, post hoc Tukey honestly significant difference t tests with mean difference, 95% CI, and Hedges' g effect sizes to examine outcomes. RESULTS: Touch sensation had a group effect with the concussion cohort needing 0.95 grams of force (gf) more relative to controls (95% CI: 0.03 to 1.87; P = .043). No touch sensation interaction was present, but medium and large effects were observed for greater gf needed among the concussed cohort at the acute (1.11 gf; 95% CI: 0.17 to 2.05; g = 0.96) and asymptomatic time points (0.79 gf; 95% CI: -0.15 to 1.73; g = 0.73). No plantar pressure pain threshold effects were observed ( P ≥ .311), with negligible pressure difference magnitudes at the acute (0.26 pound force [lbf]/cm 2 ; 95% CI: -1.54 to 2.06; g = 0.13) and medium magnitudes at the asymptomatic time points (0.99 lbf/cm 2 ; 95% CI: -0.81 to 2.80; g = 0.42) for the concussed cohort needing more pressure to detect pain. The 30° to 60° PJR had a time effect, with asymptomatic time point having 3.12° better accuracy (95% CI: 1.23° to 5.02; P = .002). The concussed cohort had small-to-medium magnitude differences relative to controls at the acute time point for PJR during 105° to 75° (0.89°; g = 0.30) and 90° to 45° (0.62°; g = 0.17), but not 30° to 60° (-1.75°; g = -0.40). CONCLUSIONS: Individuals with a concussion exhibited large effects for diminished plantar touch sensation and small to medium effects for inhibited plantar pressure pain sensation compared with controls, which may indicate altered somatosensory function. Negligible PJR differences suggest knee joint position sense is not altered post-concussion. Pre- and postconcussion examination is warranted to understand causal somatosensory mechanisms.

Concussion Assessment and Management Practices Among Irish and Canadian Athletic Therapists: An International Perspective.

CONTEXT: Certified athletic therapists in Ireland and Canada serve essential concussion assessment and management roles, but their health care practices and concussion knowledge have not been established. OBJECTIVE: To examine Irish and Canadian athletic therapist cohorts' (1) concussion knowledge, (2) current concussion assessment and management techniques across all job settings, and (3) the association of concussion assessment and management practices with years of clinical experience and highest degree attained. DESIGN: Cross-sectional cohort study. SETTING: Online survey. PATIENTS OR OTHER PARTICIPANTS: Licensed Irish (49.7%, n = 91/183) and Canadian (10.1%, n = 211/2090) athletic therapists. MAIN OUTCOME MEASURE(S): Athletic therapists completed an online survey assessing their demographics, concussion knowledge (symptom recognition, patient-clinician scenarios), frequency of concussions assessed annually, and assessment and return-to-play (RTP) measures using a modified, previously validated survey. Symptom recognition consisted of 20 (8 true, 12 false) items on recognition of signs and symptoms that were scored as total correct. Descriptive statistics and odds ratios were used to examine survey responses where appropriate. RESULTS: Irish (86.8%, n = 46/53) and Canadian (93.4%, n = 155/166) athletic therapists indicated RTP guidelines were the most common method for determining RTP. Symptom recognition scores were 72.8% ± 17.0% among Irish and 76.6% ± 17.0% among Canadian athletic therapists. Irish (91.2%, n = 52/57) and Canadian (90.4%, n = 161/178) athletic therapists reported standardized sideline assessments as the most used concussion assessment method. Irish and Canadian athletic therapists' use of 2-domain (Irish: 38.6% [n = 22/57]; Canadian: 73.6% [n = 131/178]) and 3-domain (Irish: 3.5% [n = 2/57]; Canadian: 19.7% [n = 35/178]) minimum assessments (ie, symptoms, balance, or neurocognitive) was not associated with education or clinical experience (P ≥ .07), except for Canadian athletic therapists with master's degrees having greater odds of completing 2-domain assessments at initial evaluation than those with bachelor's degrees (odds ratio = 1.80; 95% CI = 1.41, 1.95). CONCLUSIONS: Irish and Canadian athletic therapists demonstrated similar concussion knowledge; however, most did not fully adhere to international consensus guidelines for concussion assessment as evidenced by low 2- and 3-domain assessment use. Athletic therapists should aim to implement multidimensional concussion assessments to ensure optimal health care practices and patient safety.

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.

Lower-Extremity Neuromuscular Function Following Concussion: A Preliminary Examination.

CONTEXT: Neuromuscular function is altered acutely following concussion and theoretically linked to the subsequent postconcussion musculoskeletal injury risk. Existing research has only examined voluntary muscle activation, limiting mechanistic understanding. Therefore, our study aimed to examine voluntary and involuntary muscle activation between college-aged, concussed individuals when symptom-free and healthy matched controls. DESIGN: Prospective, cross-sectional cohort laboratory study. METHODS: Concussed and healthy participants (n = 24; 58% male, age: 19.3 [1.1] y, mass: 70.3 [16.4] kg, height: 177.3 [12.7] cm) completed the superimposed burst (SB) neuromuscular assessment on their dominant limb within 72 hours after self-reporting asymptomatic (22.4 [20.2] d postinjury). Unnormalized and bodyweight-normalized quadriceps maximal voluntary isometric contraction torque (in newton meters), unnormalized and bodyweight-normalized electrically stimulated SB torque, pain (numeric 1-10) during SB, and the central activation ratio (in percentage) were assessed via the SB. Parametric and nonparametric analyses, 95% confidence intervals (95% CIs), and Hedges g (parametric) and Spearman ρ (nonparametric) effect sizes were used to examine group differences (α = .05). RESULTS: The maximal voluntary isometric contraction torque (concussed: 635.60 N·m [300.93] vs control: 556.27 N·m [182.46]; 95% CI, -131.36 to 290.02; P = .443; d = 0.33), SB torque (concussed: 203.22 N·m [97.17], control: 262.85 N·m [159.07]; 95% CI, -171.22 to 51.97; P = .280; d = -0.47), and central activation ratio (concussed: 72.16% [17.16], control: 70.09% [12.63]; 95% CI, -10.68 to 14.83; P = .740; d = 0.14) did not differ between the concussed and control groups regardless of bodyweight normalization (P ≥ .344). Pain during the SB was significantly higher with a medium effect for participants with a concussion versus healthy controls (concussed: median = 7, control: median = 5; P = .046; ρ = -0.42). DISCUSSION: These findings suggest concussed participants do not have statistically altered voluntary or involuntary quadricep neuromuscular function once asymptomatic compared with controls. Therefore, the elevated postconcussion musculoskeletal injury risk may not be attributed to lower-extremity muscle activation. Concussed participants displayed greater pain perception during the SB, which suggests somatosensory or perception changes requiring further examination.

Tandem gait test-retest reliability among healthy physically active young adults.

BACKGROUND: A tandem gait assessment is recommended after concussion. There is limited research examining psychometric properties of tandem gait assessments. OBJECTIVE: To determine tandem gait test intertrial and 1-week test-retest reliability. It was hypothesized that the tandem gait test would yield moderate to good reliability, times would improve across trials/sessions, and average scores would have higher reliability. DESIGN: Reliability study. SETTING: Research laboratory. INTERVENTIONS: Sixty participants (36 females, age: 20.4 ± 1.8 years) completed 10 tandem gait test trials on two occasions. MAIN OUTCOME MEASURES: Dependent variables included number of normal trials (participants stayed on the line, heel and toe touched on every step, and they avoided touching an examiner/object) and times for each trial. We analyzed intertrial reliability using a one-way analysis of covariance and intraclass correlation coefficients (ICC), and test-retest reliability using dependent samples t-tests and ICCs. RESULTS: At the first testing session, there were significant differences in times across seven trials (F2.44,80.42 = 21.55, p < .001). All trials were faster than the first trial. The second, third, and fifth trial were faster than the previous trial. There was moderately high overall reliability across the first seven trials (ICC2,1 = 0.77, 95% confidence interval = 0.63, 0.87). All times were faster at the second testing session (compared to the first). Most outcomes for the 1-week test-retest reliability demonstrated at least moderate reliability, including the best times for the first three, four, and five trials; average times for the first four and five trials; and best and average times for all of the participants' normal trials during five and 10 attempted trials. CONCLUSIONS: There are practice effects when administering multiple tandem gait test trials, but scores stabilize after the fifth trial. There are practice effects associated with multiple administrations of the tandem gait test, but outcomes using times for four or five trials have adequate 1-week test-retest reliability in healthy physically active young adults.

Optimizing Concussion Care Seeking: A Longitudinal Analysis of Recovery.

BACKGROUND: Approximately half of concussions go undisclosed and therefore undiagnosed. Among diagnosed concussions, 51% to 64% receive delayed medical care. Understanding the influence of undiagnosed concussions and delayed medical care would inform medical and education practices. PURPOSE: To compare postconcussion longitudinal clinical outcomes among (1) individuals with no concussion history, all previous concussions diagnosed, and ≥1 previous concussion undiagnosed, as well as (2) those who have delayed versus immediate symptom onset, symptom reporting, and removal from activity after concussion. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Participants included 2758 military academy cadets and intercollegiate athletes diagnosed with concussion in the CARE Consortium. We determined (1) each participant's previous concussion diagnosis status self-reported at baseline (no history, all diagnosed, ≥1 undiagnosed) and (2) whether the participant had delayed or immediate symptom onset, symptom reporting, and removal from activity. We compared symptom severities, cognition, balance, and recovery duration at baseline, 24 to 48 hours, date of asymptomatic status, and date of unrestricted return to activity using tests of parallel profiles. RESULTS: The ≥1 undiagnosed concussion group had higher baseline symptom burdens (P < .001) than the other 2 groups and poorer baseline verbal memory performance (P = .001) than the all diagnosed group; however, they became asymptomatic and returned to activity sooner than those with no history. Cadets/athletes who delayed symptom reporting had higher symptom burdens 24 to 48 hours after injury (mean ± SE; delayed, 28.8 ± 0.8; immediate, 20.6 ± 0.7), took a median difference of 2 days longer to become asymptomatic, and took 3 days longer to return to activity than those who had immediate symptom reporting. For every 30 minutes of continued participation after injury, days to asymptomatic status increased 8.1% (95% CI, 0.3%-16.4%). CONCLUSION: Clinicians should expect that cadets/athletes who delay reporting concussion symptoms will have acutely higher symptom burdens and take 2 days longer to become asymptomatic. Educational messaging should emphasize the clinical benefits of seeking immediate care for concussion-like symptoms.

Weight Loss and Exercise Effects on Rate of Torque Development and Physical Function in Overweight Older Women.

Exercise training (EX) and weight loss (WL) improve lower extremity physical function (LEPF) in older overweight women; however, effects on rate of torque development (RTD) are unknown. This study aimed to determine the effects of WL + EX or WL alone on RTD, and relatedly LEPF, in overweight older women. Leg strength was assessed using isokinetic dynamometry, and RTD was calculated (RTD200 = RTD at 200 ms, RTDPeak = peak RTD, T2P = time to 1st peak). LEPF was determined via clinical functional tasks. Women (n = 44, 69.1 ± 3.6 years, 30.6 ± 4.3 kg/m2) completed a 6-month trial in EX + WL or WL groups with similar weight loss (-9.8 ± 4.2%, p > .95). EX + WL had greater improvements in (a) most LEPF tasks (p < .001) and (b) RTD200, compared with WL (36% vs. -16%, p = .031); no other RTD parameters differed. Changes in RTD parameters and LEPF were not related (all p > .05). RTD is responsive to EX but is not associated with LEPF in older women.