Examination of Reaction Time Deficits Following Concussion: A Systematic Review and Meta-analysis

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

BackgroundPostural 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.ObjectivesThis study investigated the acute and longitudinal effects of concussion on reactive balance in collegiate athletes.MethodsConcussed 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.ResultsAcutely 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.ConclusionsThis 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.

Investigating the role of the brain-derived neurotrophic factor Val66Met polymorphism in repetitive mild traumatic brain injury outcomes in rats

BACKGROUND

Mild traumatic brain injury (mTBI) poses a significant public health concern, particularly regarding repetitive injury, with outcomes ranging from acute neurobehavioral deficits to long-term impairments. While demographic factors like age and sex influence outcomes, the understanding of genetic contributions, particularly the role of the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism, remains limited. This study aimed to characterize acute effects of repetitive mTBI (rmTBI) in rats with the Val68Met SNP, the rodent equivalent of the human Val66Met, focusing on behavioral, fluid biomarker, and histological changes.

METHODS

Using a closed-head injury model, rats underwent five mTBIs over consecutive days. Behavioral assessments included sensorimotor function, anxiety-like behavior, spatial learning and memory, and nociceptive response. Plasma neurofilament light (NfL) levels served as a biomarker of axonal injury and immunohistochemistry evaluated microglial activation.

RESULTS

Sensorimotor deficits and increased anxiety-like behavior were found in rats with rmTBI, but these changes were not affected by sex or genotype. Plasma NfL levels were higher in rmTBI compared with sham rats, with levels greater in female rmTBI when compared with male rmTBI rats. Microglial activation was observed in the hypothalamus of injured rats, but was not influenced by genotype or sex.

CONCLUSIONS

While the Val68Met SNP did not significantly influence acute responses to rmTBI in this study, further investigation into alternative functional and pathophysiological outcomes, as well as long-term effects, is required.

In People With Subacute Mild Traumatic Brain Injury, Earlier Physical Therapy Improved Symptoms at a Faster Rate Than Later Physical Therapy: Randomized Controlled Trial

IMPORTANCE

There is unclear evidence on when to initiate physical therapy after mild traumatic brain injury (mTBI) in a non-athlete, adult population.

OBJECTIVE

The objective of this study was to investigate physical therapy timing after mTBI through changes in patient-reported and clinically-assessed tools and objective and mechanism measurements of sensorimotor balance control.

DESIGN

This study was an investigator-blinded randomized control trial (NCT03479541).

SETTING

The study took place at an academic research center.

PARTICIPANTS

Two hundred and three participants were randomized to earlier physical therapy (n = 82) or to later physical therapy (n = 121).

INTERVENTION

After enrollment, the earlier physical therapy group started rehabilitation within 1 week and the later group started rehabilitation after a 6-week wait period. All participants received similar rehabilitation; 6-week program administered and progressed by licensed physical therapists.

MAIN OUTCOMES AND MEASURES

The primary outcome was the Dizziness Handicap Inventory (DHI). Secondary outcomes included common patient-reported/clinical assessments of mTBI and objective/mechanism measurements of balance, including novel measures of central sensorimotor integration. Differences between and within the groups on outcomes were examined with linear mixed-effect models, t tests, and effect sizes.

RESULTS

While both groups significantly improved and reached similar levels on patient-reported outcomes (DHI and secondary outcomes), the earlier physical therapy group had significantly larger and faster rates of improvement compared to later physical therapy. There were differential effects of physical therapy timing on the objective/mechanism-measured outcomes. Specifically, there were significant improvements in sensorimotor time delay for the earlier physical therapy group and no change in the later group. Further, the later group worsened in the motor activation components for balance control while there was no change in the early group.

CONCLUSION AND RELEVANCE

Earlier physical therapy after mTBI can improve symptoms at a faster rate relative to later physical therapy. Earlier physical therapy also showed improvements in sensorimotor aspects of balance control, not seen in the later group. There may be an important window to address central sensorimotor deficits after mTBI.

The state of the science for potential contributors to musculoskeletal injury following concussion: Mechanisms, gaps, and clinical considerations

Concussion is a common mild traumatic brain injury affecting athletic, military, and general populations. While unrestricted medical clearance often occurs within 1-month, emerging evidence indicates prolonged sensorimotor control deficiencies and greater musculoskeletal injury risk after a concussion. Various theoretical frameworks and original studies indicate potential neurophysiological alterations affecting sensory input, sensorimotor integration, and neuromotor output, though the exact mechanisms remain unclear. This commentary aims to briefly review the literature on contributors to sensory and neuromotor deficiencies potentially related to musculoskeletal injury risk, recommend future research avenues to better understand these factors, and highlight current and future clinical applications.

Test-Retest Reliability and Reliable Change Estimates for Sensorimotor Concussion Assessments in Healthy Young Adults

CONTEXT

Sensorimotor impairments are common sequela following concussion, but recovery following a concussion is often determined through examiner scored clinical testing. There are emerging technologies that provide objective methods to determine physiological impairment after concussion, but the psychometrics of these tools are lacking and must be established for use in clinical practice.

OBJECTIVE

The purpose of this study was to examine the test-retest reliability and provide reliable change estimates in healthy young adults for outcomes from 3 emerging technologies providing objective assessments of sensorimotor function in healthy young adults.

DESIGN

Test-retest reliability design in a laboratory setting.

METHODS

Healthy, young adults completed testing at 2 time points 4 weeks apart on the Bertec Vision Trainer, the Concussion Balance Test (COBALT), and the Neurolign Dx-100 eye-tracking system. We determined test-retest reliability using intraclass correlation coefficients with a 2-way mixed-effects model absolute agreement. Reliable change estimates were calculated for 70%, 80%, 90%, and 95% CIs.

RESULTS

Participants included 30 healthy young adults (age = 25 [5] y, interquartile range = 20-29; range = 18-38; 17% [57%] women). Test-retest reliability for the Bertec Vision Trainer outcomes ranged from 0.56 to 0.88, with 45% of the outcomes being classified as clinically acceptable (>.70 intraclass correlation coefficients ); for COBALT conditions, sway velocity ranged from 0.50 to 0.95, 95% ellipse area ranged from -0.22 to 0.88, and Sway Score ranged from 0.07 to 0.85, with 50% of COBALT metrics being clinically acceptable; and for the Dx-100, outcomes ranged from -0.20 to 0.89, with 52% being clinically acceptable.

CONCLUSIONS

Overall, test-retest reliability was moderate-to-good for the Bertec Vision Trainer assessment outcomes but were highly variable for outcomes of postural control using the COBALT and eye-tracking metrics using the Dx-100. This study adds clinically relevant test-retest reliability and reliable change estimates in healthy adults for 3 commercially available sensorimotor assessments.

Neuromechanical Models of Mild Traumatic Brain Injury Conditioned on Reaction Time: A Systematic Review and Meta-Analysis

The accurate, repeatable, and cost-effective quantitative characterization of mild traumatic brain injuries (mTBIs) is crucial for safeguarding the long-term health and performance of high-risk groups, including athletes, emergency responders, and military personnel. However, gaps remain in optimizing mTBI assessment methods, especially regarding the integration of neuromechanical metrics such as reaction time (RT) in predictive models. Background/Objectives: This review synthesizes existing research on the use of neuromechanical probabilistic models as tools for assessing mTBI, with an emphasis on RT's role in predictive diagnostics. Methods: We examined 57 published studies on recent sensing technologies such as advanced electromyographic (EMG) systems that contribute data for probabilistic neural imaging, and we also consider measurement models for real-time RT tracking as a diagnostic measure. Results: The analysis identifies three primary contributions: (1) a comprehensive survey of probabilistic approaches for mTBI characterization based on RT, (2) a technical examination of these probabilistic algorithms in terms of reliability and clinical utility, and (3) a detailed outline of experimental requirements for using RT-based metrics in psychomotor tasks to advance mTBI diagnostics. Conclusions: This review provides insights into implementing RT-based neuromechanical metrics within experimental frameworks for mTBI diagnosis, suggesting that such metrics may enhance the sensitivity and utility of assessment and rehabilitation protocols. Further validation studies are recommended to refine RT-based probabilistic models for mTBI applications.

Youth Soccer Heading Exposure and Its Effects on Clinical Outcome Measures

Purposeful heading, in which players may use their heads to advance the ball in play, is a unique part of soccer. Clinical outcome measures used to aid in the diagnosis of a concussion have long been a cornerstone of the contemporary measurements associated with the short- and long-term effects of monitoring repetitive head impacts (RHI) and soccer heading exposure. The effects of RHI in the youth population are still unknown, therefore, the purpose of this study was to examine if heading exposure is predictive of changes in self-reported symptoms, neurocognitive functioning, gait, and balance in female youth soccer players over the course of one soccer season. Small improvements in neurocognitive functioning and gait and slight deficits in balance were observed from pre- to post-season. All changes were not clinically relevant and likely due to a practice effect. The low heading exposure in our cohort of youth soccer players was likely not enough to elicit any changes in clinical measures. In general, our clinical outcomes did not change after a season of soccer play and change scores were not predicted by heading exposure.

The Influence of Kinesiophobia on Time to Clinical Recovery in Collegiate Athletes with Concussion

BACKGROUND

Several factors such as acute symptom severity, premorbid anxiety, and depression have been associated with concussion recovery. Elevated kinesiophobia has been associated with recovery from musculoskeletal conditions, as well as increased reaction time and vestibular-ocular motor dysfunction following concussion. However, kinesiophobia has yet to be evaluated as a modifier of concussion recovery time.

OBJECTIVES

This study was designed to evaluate the role of acute kinesiophobia levels on days until clinical recovery in collegiate athletes with concussion. We hypothesized that collegiate athletes with elevated Tampa Scale of Kinesiophobia (TSK) scores would take a greater number of days to achieve clinical recovery compared with athletes with lower values.

METHODS

Division I collegiate athletes diagnosed with a concussion (N = 113, 19.9 ± 1.5 years, 42% female) participated in this descriptive laboratory study. Participants were assigned to high [≥ 37 (H-TSK, n = 54)] or low [< 37 (L-TSK, n = 59)] TSK groups on the basis of the first TSK values recorded within 72 h of their concussion. Participants were also administered the Revised Head Injury Scale (HIS-r) to assess symptom severity within 72 h of injury. The Immediate Postconcussion and Cognitive Test (ImPACT) battery was administered at baseline and used to gather demographic variables such as biological sex, age, history of anxiety/depression, and concussion history, and as part of the athletes' symptom-free assessment. Days until clinical recovery between H-TSK and L-TSK groups were compared using a Mann-Whitney U test. Spearman's rank correlation coefficients were calculated to determine the relationship between TSK and days until clinical recovery in addition to other modifiers of recovery. Multiple linear regression was used to evaluate days until clinical recovery as a function of the TSK total score, controlling for the HIS-r and ImPACT variables.

RESULTS

Days until clinical recovery was significantly longer in the H-TSK group (median difference = 2.5 days, p < 0.001) compared with the L-TSK group. A significant, moderate positive correlation between the TSK score and days to clinical recovery (ρ = 0.45, p < 0.001) was observed, which was also the strongest correlation among all variables. Our regression model demonstrated that for every point increase on the TSK, days until clinical recovery increased by 0.23 while controlling for total symptom severity, age, concussion history, psychiatric history, and biological sex (β = 0.23, p = 0.018). All other variables entered into the regression were not statistically significant.

CONCLUSIONS

Our data suggest that athletes with TSK scores above 37 within 72 h of a concussion had a greater number of days until clinical recovery when compared with athletes with TSK values below 37. The TSK score had the highest correlation with days until clinical recovery when compared with other known modifiers of recovery, including total symptom severity. The TSK score was also the strongest predictor of days until clinical recovery. Collectively, these findings suggest that the TSK score should be considered by healthcare professionals to help inform effective management strategies for collegiate athletes with concussion.

Female Collegiate Athletes' Concussion Characteristics and Recovery Patterns: A Report from the NCAA-DoD CARE Consortium

Concussion has been described in the United States (US) collegiate student-athlete population, but female-specific findings are often underrepresented and underreported. Our study aimed to describe female collegiate student-athletes' initial injury characteristics and return to activity outcomes following concussion. Female collegiate student-athletes (n = 1393) from 30-US institutions experienced a concussion and completed standardized, multimodal concussion assessments from pre-injury through unrestricted return to play (uRTP) in this prospective, longitudinal cohort study. Initial injury presentation characteristics, assessment, and return to activity outcomes [<48-h (acute), return to learn, initiate return to play (iRTP), uRTP] were collected. We used descriptive statistics to report injury characteristics, return to activity outcomes, and post-injury assessment performance change categorization (worsened, unchanged, improved) based on change score confidence rank criteria across sport contact classifications [contact (n = 661), limited (n = 446), non-contact (n = 286)]. The median (25th to 75th percentile) days to return to learn was 6.0 (3.0-10.0), iRTP was 8.1 (4.8-13.8), and uRTP was 14.8 (9.9-24.0), but varied by contact classification. Across contact levels, the majority experienced worse SCAT total symptom severity (72.8-82.6%), ImPACT reaction time (91.2-92.6%), and BSI-18 total score (45.2-51.8%) acutely relative to baseline, but unchanged BESS total errors (58.0-60.9%), SAC total score (71.5-76.1%), and remaining ImPACT domains (50.6-66.5%). Our findings provide robust estimates of the typical female collegiate student-athlete presentation and recovery trajectory following concussion, with overall similar findings to the limited female collegiate student-athlete literature. Overall varying confidence rank classification was observed acutely. Our findings provide clinically-relevant insights for athletes, clinicians, researchers, and policymakers to inform efforts specific to females experiencing concussion.

Initial Mild Traumatic Brain Injury Characteristics and Recovery Patterns Among Females Across the United States Military Service Academies: A Report from the NCAA-DoD CARE Consortium

Mild traumatic brain injury (mTBI) has been described in the United States (US) military service academy cadet population, but female-specific characteristics and recovery outcomes are poorly characterized despite sex being a confounder. Our objective was to describe female cadets' initial characteristics, assessment performance, and return-to-activity outcomes post-mTBI. Female cadets (n = 472) from the four US military service academies who experienced a mTBI completed standardized mTBI assessments from pre-injury to acute initial injury and unrestricted return-to-duty (uRTD). Initial injury presentation characteristics (e.g., delayed symptoms, retrograde amnesia) and return-to-activity outcomes [i.e., return-to-learn, initiate return-to-duty protocol (iRTD), uRTD] were documented. Descriptive statistics summarized female cadets' injury characteristics, return-to-activity outcomes, and post-mTBI assessment performance change categorization (worsened, unchanged, improved) relative to pre-injury baseline using established change score confidence rank criteria for each assessment score. The median (interquartile range) days to return-to-learn (n = 157) was 7.0 (3.0-14.0), to iRTD (n = 412) was 14.7 (8.6-25.8), and to uRTD (n = 431) was 26.0 (17.7-41.8). The majority experienced worse SCAT total symptom severity (77.8%) and ImPACT reaction time (97.0%) acutely < 24-h versus baseline, but unchanged BESS total errors (75.2%), SAC total score (72%), BSI-18 total score (69.6%), and ImPACT verbal memory (62.3%), visual memory (58.4%), and visual motor speed (52.5%). We observed similar return-to-activity times in the present female cadet cohort relative to the existing female-specific literature. Confidence ranks categorizing post-mTBI performance were heterogenous and indicate multimodal assessments are necessary. Our findings provide clinically relevant insights to female cadets experiencing mTBI across the US service academies for stakeholders providing healthcare.

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.

The Effect of Impact Seizure on the Recovery of Children and Adolescents With Concussion: A Matched Case-Control Study

OBJECTIVE

Management of sport-related and recreation-related concussions (SRCs) in children and adolescents is challenging as brain maturation affects prognosis. However, impact seizure was removed as a prognosis modifying factor in children and adolescents with SRCs in the 2017 consensus statement on concussion in sport, based mostly on adult literature. Therefore, this study evaluates the association of impact seizure on the recovery in children and adolescents with SRCs.

DESIGN

Retrospective matched case-control study.

SETTING

Tertiary pediatric sports medicine service, from January 1, 2015, to June 30, 2022.

PATIENTS

A cohort of 452 patients, aged 7 to 18 years, with new episode of SRC was seen. From this cohort, 396 patients were included in the analysis, including 22 with impact seizures. Controls were generated using the propensity score matching approach. Patients with moderate or severe traumatic brain injury or incomplete treatment were excluded.

INDEPENDENT VARIABLE

Impact seizure during SRC.

MAIN OUTCOME MEASURES

Primary outcome was recovery duration in number of days.

RESULTS

The median recovery duration was longer in the cases (73 days, interquartile range [IQR] = 38-143 days) as compared with controls (49.5 days, IQR = 30.5-93.5 days). There was no difference in patients with prolonged recovery (ie >28 days) between both groups (OR 1.6, 95% CI, 0.4-6.6, P = 0.505).

CONCLUSIONS

Impact seizures prolonged the recovery duration in children and adolescents with SRCs and therefore have a potential concussion modifying prognostic role. These findings could help provide evidence-based management principles for children and adolescents with SRCs in subsequent concussion consensus statements.

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.

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.

Acute effects of an isometric neck warm-up programme on neck performance characteristics and ultrasound-based morphology

OBJECTIVE

Athletic performance can be enhanced immediately after an isometric warm-up, a phenomenon termed post-activation performance enhancement (PAPE). While isometric warm-ups can improve lower extremity sprint and jump performance, neck-specific isometric warm-ups need development and validation for mild traumatic brain disorders and neck pain. This study examined acute effects of isometric warm-ups on neck performance and morphology.

METHODS

Arm 1: Twenty-six adults (13 M:13F) completed neck performance testing before and after a 10-minute neck isometric warm-up or stationary bike (sham) between two visits. Testing included visual-motor reaction time, peak force, rate of force development, force steadiness, and force replication/proprioception measured by a 6-axis load cell. An inclinometer assessed range-of-motion. Paired t-tests and two-way ANOVA examined effects of neck/bike warm-up and interaction effects, respectively. Arm 2: 24 adults (11 M:13F) completed ultrasound scans of cervical muscles: before 20-minute rest (sham), and before/after a 5-min neck isometric warm-up. Longus colli cross-sectional area and sternocleidomastoid/upper trapezius thickness and stiffness, and cervical extensors thickness was assessed. One-way ANOVA compared morphological values at sham, before, and after warm-up. Significance was set at p < 0.05.

RESULTS

Isometric neck warm-up increased rate of force development in flexion (p = 0.022), extension (p = 0.001-0.003), right lateral flexion (p = 0.004-0.032), left lateral flexion (p = 0.005-0.014), while peak force improved only in left lateral flexion (p = 0.032). Lateral flexion range-of-motion increased after neck warm-up (p = 0.003-0.026). Similarly, longus colli cross-sectional area (p = 0.016) and sternocleidomastoid thickness (p = 0.004) increased.

CONCLUSIONS

Increased neck performance characteristics and morphology are likely due to PAPE effects of isometric neck warm-up. For coaches and athletes, simple isometric contractions could be added to existing warm-ups to reduce prevalence, incidence, and severity of mild traumatic brain injuries and neck pain.

Effects of sociodemographic and player characteristics on baseline cognitive performance in 1000 rugby players: A retrospective 8-year follow-up study

OBJECTIVES

To analyze the effects of sociodemographic and player characteristics on the Sport Concussion Assessment Tool and neuropsychological scores over 8 years in a large sample of rugby players.

DESIGN

An 8-year retrospective study of preseason clinical assessments of professional rugby players and players enrolled in training academies at professional clubs.

METHODS

The Sport Concussion Assessment Tool-3 or -5, Trail Making Test and Digit Symbol Substitution Test were administered prior to the start of the competition season for each player. Statistical analyses included: (i) descriptive analyses of sociodemographic, player and neuropsychological characteristics; (ii) multivariate models to identify factors influencing cognitive scores at the first visit; and (iii) linear mixed models to assess the evolution of the scores over the years.

RESULTS

One thousand players were included (mean age: 22.8, males: 92 %). Twenty-two percent of the athletes reported baseline symptoms. A higher level of education was associated with better cognitive scores at the first visit and over the years. Forwards had poorer processing speed performances compared to backs at the first visit and over repeated assessments. Finally, the number of examinations was associated with improved cognitive scores showing a practice effect on all the neuropsychological tests, except for the Standardized Assessment of Concussion 5th edition.

CONCLUSIONS

Results from this retrospective study could help to improve the management of athletes and return-to-play decision-making in collision sports.

Sports-Related Concussion Assessment: A New Physiological, Biomechanical, and Cognitive Methodology Incorporating a Randomized Controlled Trial Study Protocol

BACKGROUND

Taking part in moderate-to-vigorous exercise in contact sports on a regular basis may be linked to an increase in cerebrovascular injury and head trauma. Validated objective measures are lacking in the initial post-event diagnosis of head injury. The exercise style, duration, and intensity may also confound diagnostic indicators. As a result, we propose that the new Interdisciplinary Group in Movement & Performance from Acute & Chronic Head Trauma (IMPACT) analyze a variety of functional (biomechanical and motor control) tests as well as related biochemistry to see how they are affected by contact in sports and head injury. The study's goal will be to look into the performance and physiological changes in rugby players after a game for head trauma and injury.

METHODS

This one-of-a-kind study will use a randomized controlled trial (RCT) utilizing a sport participation group and a non-participation control group. Forty male rugby 7 s players will be recruited for the study and allocated randomly to the experimental groups. The intervention group will participate in three straight rugby matches during a local 7 s rugby event. At the pre-match baseline, demographic and anthropometric data will be collected. This will be followed by the pre-match baseline collection of biochemical, biomechanical, and cognitive-motor task data. After three consecutive matches, the same measures will be taken. During each match, a notational analysis will be undertaken to obtain contact information. All measurements will be taken again 24, 48, and 72 h after the third match.

DISCUSSION

When the number of games increases owing to weariness and/or stressful circumstances, we expect a decline in body movement, coordination, and cognitive-motor tasks. Changes in blood biochemistry are expected to correspond to changes in biomechanics and cognitive-motor processes. This research proposal will generate considerable, ecologically valid data on the occurrence of head trauma events under game conditions, as well as the influence of these events on the biological systems of the performers. This will lead to a greater understanding of how sports participants react to exercise-induced injuries. This study's scope will have far-reaching ramifications for doctors, coaches, managers, scientists, and sports regulatory bodies concerned with the health and well-being of athletic populations at all levels of competition, including all genders and ages.

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.

Neck strength and force in reaction time task of adolescent athletes with and without concussion history: A pilot study

OBJECTIVES

Assess the impact of concussion by comparing reaction time, peak force recruitment, and rate of force development of adolescent athletes returning from concussion against age- and sex-matched controls in visual-elicited neck movement.

DESIGN

Athletes sat secured in a custom-built isometric device with their heads secured in a helmet and attached to a 6-axis load cell. They performed neck flexion, extension, and lateral flexion in response to a visual cue. Three trials in each direction were used for statistical analyses; peak force and rate of force development were normalized against athlete mass.

SETTING

Laboratory.

PARTICIPANTS

26 adolescent/young adult athletes (8F/18M), either recently concussed (and cleared for return to sport) or an age- and sex-matched healthy control.

MAIN OUTCOME MEASURES

Reaction time, angle, standard deviation of angle, deviation from target angle, peak force, and RFD over 50, 100, 150,and 200 ms of movement were measured for each trial.

RESULTS

Concussed athletes had decreased normalized peak force (P = 0.008) and rate of force development (P < 0.001-0.007). In neck extension, concussed athletes also had decreased movement precision (P = 0.012).

CONCLUSIONS

Concussion is associated with alterations of neck biomechanics that decrease overall neck strength.

Immediate effects and duration of a short and single application of transcutaneous auricular vagus nerve stimulation on P300 event related potential

Introduction

Transcutaneous auricular vagus nerve stimulation (taVNS) is a neuromodulatory technique that stimulates the auricular branch of the vagus nerve. The modulation of the locus coeruleus-norepinephrine (LC-NE) network is one of the potential working mechanisms of this method. Our aims were 1-to investigate if short and single applications of taVNS can modulate the P300 cognitive event-related potential (ERP) as an indirect marker that reflects NE brain activation under control of the LC, and 2-to evaluate the duration of these changes.

Methods

20 healthy volunteers executed an auditory oddball paradigm to obtain P300 and reaction time (RT) values. Then a 7 min active or sham taVNS period was initiated and simultaneously a new P300 paradigm was performed. We successively repeated the paradigm on 4 occasions with different time intervals up to 56 min after the stimulation onset.

Results

During active taVNS an immediate and significant effect of increasing the amplitude and reducing the latency of P300, as well as a shortening in the RT was observed. This effect was prolonged in time up to 28 min. The values then returned to pre-stimulation levels. Sham stimulation did not generate changes.

Discussion

Our results, demonstrate differential facilitating effects in a concrete time window after taVNS. Literature about the modulatory effect of taVNS over P300 ERP shows a wide spread of results. There is not a standardized system for taVNS and currently the great heterogeneity of stimulation approaches concerning targets and parameters, make it difficult to obtain conclusions about this relationship. Our study was designed optimizing several stimulation settings, such as a customized earbud stimulator, enlarged stimulating surface, simultaneous stimulation over the cymba and cavum conchae, a Delayed Biphasic Pulse Burst and current controlled stimulation that adjusted the output voltage and guaranteed the administration of a preset electrical dose. Under our stimulation conditions, targeting vagal nerve fibers via taVNS modulates the P300 in healthy participants. The optimal settings of modulatory function of taVNS on P300, and their interdependency is insufficiently studied in the literature, but our data provides several easily optimizable parameters, that will produce more robust results in future.

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 ± 1.5 years, height = 166.9 ± 6.7 cm, mass = 62.8 ± 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 ± 1.0 years, height = 172.7 ± 8.3 cm, mass = 65.4 ± 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.

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.

Mental Fatigue Uniquely Influences Drop Landing Biomechanics for Individuals With a Concussion History

CONTEXT

Induced mental fatigue negatively impacts sport performance and neurocognition. However, it is unclear how induced mental fatigue influences landing biomechanics. The purpose of this study was to examine the influence of mental fatigue on drop landing biomechanics in individuals with and without a concussion history.

DESIGN

Crossover design.

METHODS

Forty-eight (24 per group) recreationally active individuals were matched on age (±3 y), sex, and body mass index (±1 kg/m2). All participants completed an experimental (30-min Stroop task) and control (30-min reading magazines) intervention on separate days separated by a minimum of 24 hours. Drop landings were performed before and after both interventions. Outcomes included peak vertical ground reaction force (vGRF), vertical loading rate (VLR), knee flexion angle, knee abduction angle, external knee flexion moment, external knee abduction moment, and initial ground contact knee flexion and knee abduction angles. Separate 2 (group) × 2 (intervention) between-within analyses of covariance compared drop landing outcomes. Each group's average pre-Stroop and premagazine outcomes were covariates.

RESULTS

There was a significant interaction for vGRF (P = .033, ηp2=.097) and VLR (P = .0497, ηp2=.083). The vGRF simple effects were not statistically significantly (P range = .052-.325). However, individuals with a concussion history displayed a medium effect size for greater vGRF post-Stroop compared with their own postmagazine vGRF (mean difference (95% confidence interval [95% CI] = 0.163 (-0.002 to 0.327) bodyweight (BW), p = .052, ηp2=.081. In contrast, the control group displayed a small effect size (mean difference [95% CI] = 0.095 [-0.069 to 0.259] BW, p = .251, ηp2=.029). Individuals with a concussion history displayed greater VLR post-Stroop compared with controls (mean difference [95% CI], 26.29 [6.19 to 46.40] BW/s, P = .012, ηp2=.134) and their own postmagazine values (mean difference [95% CI] = 32.61 [7.80 to 57.42] BW/s, p = .011, ηp2=.135).

CONCLUSION

Mental fatigue leads to greater VLR for individuals with a concussion history. Athletic competition and activities of daily living can increase mental fatigue. Training programs may seek to teach mental fatigue reducing strategies to athletes with a concussion history.

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.

Reliability and Validity of Inertial Sensor Assisted Reaction Time Measurement Tools among Healthy Young Adults

The assessment of movement reaction time (RT) as a sideline assessment is a valuable biomarker for mild TBI or concussion. However, such assessments require controlled laboratory environments, which may not be feasible for sideline testing during a game. Body-worn wearable devices are advantageous as being cost-effective, easy to don and use, wirelessly transmit data, and ensure unhindered movement performance. This study aimed to develop a Drop-stick Test System (DTS) with a wireless inertial sensor and confirm its reliability for different standing conditions (Foam versus No Foam) and task types (Single versus Dual), and postures (Standing versus sitting). Fourteen healthy young participants (seven females, seven males; age 24.7 ± 2.6 years) participated in this study. The participants were asked to catch a falling stick attached to the sensor during a drop test. Reaction Times (RTs) were calculated from data for each trial from DTS and laboratory camera system (gold standard). Intraclass correlation coefficients (ICC 3,k) were computed to determine inter-instrument reliability. The RT measurements from participants using the camera system and sensor-based DTS showed moderate to good inter-instrument reliability with an overall ICC of 0.82 (95% CI 0.78-0.85). Bland-Altman plots and 95% levels of agreement revealed a bias where the DTS underestimated RT by approximately 50 ms.

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.

Comparison of Azure Kinect overground gait spatiotemporal parameters to marker based optical motion capture

BACKGROUND

Instrumented measurement of spatiotemporal parameters during walking can provide valuable information on an individual's overall function and health. Efficient, inexpensive, and accurate measurement of overground walking spatiotemporal parameters would be a critical component of providing point-of-care assessments of gait function, concussion recovery, fall-risk, and cognitive decline. Depth cameras combined with skeleton pose tracking algorithms, such as the Microsoft Kinect with body tracking software, have been used to measure walking spatiotemporal parameters. However, the ability of the latest generation Microsoft Kinect sensor, the Azure Kinect, to accurately measure overground walking spatiotemporal parameters has not been evaluated in the literature.

RESEARCH QUESTION

The purpose of this work was to compare overground walking spatiotemporal parameters measurements from a 12 camera Vicon optical motion capture system to measurements of a single Azure Kinect with body tracking SDK (software development kit).

METHODS

Spatiotemporal parameters of overground walking were simultaneously collected on twenty young healthy participants. Stride length, stride time, step length and step width were derived from ankle joint center locations and measurements from the two instruments were compared using descriptive statistics, scatter plots, Pearson correlation analyses, and Bland-Altman analyses.

RESULTS

Pearson correlation coefficients were greater than 0.87 for all spatiotemporal parameters with most parameters demonstrating very strong (> 0.9) agreement. The mean of the differences for stride length between measurements was 35.6 mm for the left limb and 39.1 mm for the right limb, both of which are less than 3% of average stride length. Mean of the differences for step width and stride time were less than 2% and 1% of their averages respectively.

SIGNIFICANCE

A single Microsoft Azure Kinect with body tracking SDK can provide clinically relevant measurement of walking spatiotemporal parameters, providing accessible and objective measurements that can improve clinical decision making across a variety of patient populations.

Anticipatory and reactive responses to underfoot perturbations during gait in healthy adults and individuals with a recent mild traumatic brain injury

BACKGROUND

Following mild traumatic brain injury, individuals often exhibit quantifiable gait deficits over flat surfaces, but little is known about how they control gait over complex surfaces. Such complex surfaces require precise neuromotor control to anticipate and react to small disturbances in walking surfaces, and mild traumatic brain injury-related balance deficits may adversely affect these gait adjustments.

METHODS

This study investigates anticipatory and reactive gait adjustments for expected and unexpected underfoot perturbations in healthy adults (n = 5) and individuals with mild traumatic brain injury (n = 5). Participants completed walking trials with random unexpected or expected underfoot perturbations from a mechanized shoe and inertial measurement units collected kinematic data from the feet and sternum. Linear mixed-effects models assessed the effects of segment, group, and their interaction on standardized difference of accelerations between perturbation and non-perturbation trials.

FINDINGS

Both groups demonstrated similar gait strategies when perturbations were unexpected. During late swing phase before expected perturbations, persons with mild traumatic brain injury exhibited greater lateral acceleration of their perturbed foot and less lateral movement of their trunk compared with unperturbed gait. Control participants exhibited less lateral foot acceleration and no difference in mediolateral trunk acceleration compared with unperturbed gait during the same period. A significant group*segment interaction (p < 0.001) during this part of the gait cycle suggests the groups adopted different anticipatory strategies for the perturbation.

INTERPRETATION

Individuals with mild traumatic brain injury may be adopting cautious strategies for expected perturbations due to persistent neuromechanical deficits stemming from their injury.

Whole-Body Reactive Agility Metrics to Identify Football Players With a Core and Lower Extremity Injury Risk

Clinical prediction models are useful in addressing several orthopedic conditions with various cohorts. American football provides a good population for attempting to predict injuries due to their relatively high injury rate. Physical performance can be assessed a variety of ways using an assortment of different tests to assess a diverse set of metrics, which may include reaction time, speed, acceleration, and deceleration. Asymmetry, the difference between right and left performance has been identified as a possible risk factor for injury. The purpose of this study was to determine the whole-body reactive agility metrics that would identify Division I football players who were at elevated risk for core, and lower extremity injuries (CLEI). This cohort study utilized 177 Division I football players with a total of 57 CLEI suffered who were baseline tested prior to the season. Single-task and dual-task whole-body reactive agility movements in lateral and diagonal direction reacting to virtual reality targets were analyzed separately. Receiver operator characteristic (ROC) analyses narrowed the 34 original predictor variables to five variables. Logistic regression analysis determined the three strongest predictors of CLEI for this cohort to be: lateral agility acceleration asymmetry, lateral flanker deceleration asymmetry, and diagonal agility reaction time average. Univariable analysis found odds ratios to range from 1.98 to 2.75 for these predictors of CLEI. ROC analysis had an area under the curve of 0.702 for any combination of two or more risk factors produced an odds ratio of 5.5 for risk of CLEI. These results suggest an asymmetry of 8-15% on two of the identified metrics or a slowed reaction time of ≥0.787 s places someone at increased risk of injury. Sixty-three percent (36/57) of the players who sustained an injury had ≥2 positive predictors In spite of the recognized limitation, these finding support the belief that whole-body reactive agility performance can identify Division I football players who are at elevated risk for CLEI.

Reaction Time Task Performance in Concussed Athletes over a 30-Day Period: An Observational Study

OBJECTIVE

Reaction time is a common deficit following concussion, making its evaluation critical during return-to-play protocol. Without proper evaluation, an athlete may return-to-play prematurely, putting them at risk of further injury. Although often assessed, we propose that current clinical testing may not be challenging enough to detect lingering deficits. Thus, the aim of this study was to examine reaction time in concussed individuals three times over a 30-day period through the use of a novel reaction time device consisting of simple, complex, and go/no-go reaction time tasks.

METHODS

Twenty-three concussed subjects completed simple, complex, and go/no-go reaction time tests at three different timepoints: within 7-, 14-, and 30-days of injury, and 21 healthy controls completed the three reaction time tasks during a single session.

RESULTS

Independent t-tests revealed that for the simple reaction time task, concussed participants were only significantly slower at session 1 (p = .002) when compared to controls. Complex reaction time task results showed concussed participants to be significantly slower at session 1 (p = .0002), session 2 (p = .001), and session 3 (p = .002). Go/no-go results showed concussed participants to be significantly slower than controls at session 1 (p = .003), session 2 (p = .001), and session 3 (p = .001).

CONCLUSIONS

Concussed individuals display prolonged reaction time deficits beyond the acute phase of injury, illustrated using increasingly complex tasks.

Interpreting Clinical Reaction Time Change and Recovery After Concussion: A Baseline Versus Norm-Based Cutoff Score Comparison

CONTEXT

Preseason testing can be time intensive and cost prohibitive. Therefore, using normative data for postconcussion interpretation in lieu of preseason testing is desirable.

OBJECTIVE

To establish the recovery trajectory for clinical reaction time (RTclin) and assess the usefulness of changes from baseline (comparison of postconcussion scores with individual baseline scores) and norm-based cutoff scores (comparison of postconcussion scores with a normative mean) for identifying impairments postconcussion.

DESIGN

Case-control study.

SETTING

Multisite clinical setting.

PATIENTS OR OTHER PARTICIPANTS

An overlapping sample of 99 participants (age = 19.0 ± 1.1 years) evaluated within 6 hours postconcussion, 176 participants (age = 18.9 ± 1.1 years) evaluated at 24 to 48 hours postconcussion, and 214 participants (age = 18.9 ± 1.1 years) evaluated once they were cleared to begin a return-to-play progression were included. Participants with concussion were compared with 942 control participants (age = 19.0 ± 1.0 years) who did not sustain a concussion during the study period but completed preseason baseline testing at 2 points separated by 1 year (years 1 and 2).

MAIN OUTCOME MEASURE(S)

At each time point, follow-up RTclin (ie, postconcussion or year 2) was compared with the individual year 1 preseason baseline RTclin and normative baseline data (ie, sex and sport specific). Receiver operating characteristic curves were calculated to compare the sensitivity and specificity of RTclin change from baseline and norm-based cutoff scores.

RESULTS

Clinical reaction time performance declined within 6 hours (18 milliseconds, 9.2% slower than baseline). The decline persisted at 24 to 48 hours (15 milliseconds, 7.6% slower than baseline), but performance recovered by the time of return-to-play initiation. Within 6 hours, a change from baseline of 16 milliseconds maximized combined sensitivity (52%) and specificity (79%, area under the curve [AUC] = 0.702), whereas a norm-based cutoff score of 19 milliseconds maximized combined sensitivity (46%) and specificity (86%, AUC = 0.700). At 24 to 48 hours, a change from baseline of 2 milliseconds maximized combined sensitivity (64%) and specificity (61%, AUC = 0.666), whereas a norm-based cutoff score of 0 milliseconds maximized combined sensitivity (63%) and specificity (62%, AUC = 0.647).

CONCLUSIONS

Norm-based cutoff scores can be used for interpreting RTclin scores postconcussion in collegiate athletes when individual baseline data are not available, although low sensitivity and specificity limit the use of RTclin as a stand-alone test.

Transitory kinesiophobia after sport-related concussion and its correlation with reaction time

OBJECTIVES

To examine kinesiophobia (i.e. fear of movement) among adolescent athletes with concussion compared to controls, and correlations of kinesiophobia with symptoms and reaction time.

DESIGN

Prospective cohort study.

METHODS

We evaluated 49 adolescent athletes twice. The concussion group was assessed within 14 days of injury and at return-to-play clearance. The control group was tested initially and approximately 28 days later. Participants completed Tampa Scale of Kinesiophobia, Post-Concussion Symptom Inventory, and clinical reaction time assessments.

RESULTS

We included 32 concussion participants (15 ± 2 years; 50% female) and 17 controls (16 ± 1 years; 47% female). Acutely (<14 days post-injury), the concussion group reported greater Tampa Scale of Kinesiophobia scores (38.5 ± 5.4 vs. 29.4 ± 6.7; p < 0.001; Cohen's d = 1.54), and a greater proportion of "high" (≥37) scores than controls (69% vs. 6%; p < 0.001). At return-to-play, there were no significant between-group differences (33.3 ± 6.5 vs. 30.8 ± 7.4; p = 0.23; Cohen's d = 0.36); 28% of the concussion group reported "high" Tampa Scale of Kinesiophobia scores. At return-to-play, kinesiophobia was significantly/moderately correlated with clinical reaction time for the concussion group (r = 0.50; p = 0.01).

CONCLUSIONS

Adolescents recovering from concussion commonly reported high kinesiophobia initially postconcussion, while 28% continued to report high kinesiophobia at return-to-play clearance. Additionally, a correlation between Tampa Scale of Kinesiophobia scores and clinical reaction time was observed for the concussion group. This finding would benefit from further study to determine potential perception-behavior relationships following concussion.

Optimizing Order of Administration for Concussion Baseline Assessment Among NCAA Student-Athletes and Military Cadets

BACKGROUND

Concussion pre-injury (i.e., baseline) assessments serve as a benchmark comparison point in the event an individual sustains a concussion and allows clinicians to compare to post-injury measures. However, baseline assessments must reflect the individual's true and most optimized performance to serve as a useful comparison. Mental fatigue and motivation throughout baseline testing may alter individual assessment performance, indicating an order of administration (OoA) may play an influential role in assessment outcomes.

OBJECTIVE

To examine the influence concussion baseline battery OoA has on symptom, postural stability, cognitive screening, and computerized neurocognitive test outcomes.

METHODS

We employed a retrospective observational cohort study to examine healthy collegiate student-athletes and military cadets (n = 2898, 19.0 ± 1.4 years, 66.1% male, 75.6% white, 54.4% Division-I) baseline assessment performance on the Sport Concussion Assessment Tool (SCAT; total symptom number and severity), Balance Error Scoring System (BESS; total error scores), Standardized Assessment of Concussion (SAC; total score), and Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) domain scores (verbal and visual memory, visual-motor speed, reaction time). Assessments were binned to beginning, middle, or end tertiles based upon OoA. We used one-way ANOVAs with Tukey post-hoc t tests, 95% confidence intervals (CI), and Cohen's d effect sizes for significant models (α = 0.05).

RESULTS

SCAT total symptom number (mean difference = 2.23; 95% CI 1.76-2.70; d = 0.49, p < 0.001) and severity (mean difference = 5.58; 95% CI 4.42-6.74; d = 0.50; p < 0.001) were lower when completed at the end of baseline testing compared to the middle. Total BESS errors were 1.06 lower when completed at the middle relative to the end (95% CI 0.43-1.69; d = 0.17; p = 0.001). Total SAC scores were better at the beginning relative to middle (mean difference = 0.58; 95% CI 0.25-0.90; d = 0.33; p < 0.001) and end (mean difference = 0.44; 95% CI 0.16-0.73; d = 0.24; p = 0.001). Verbal memory, visual memory, and reaction time performance were highest at the beginning (p ≤ 0.002), while visual-motor speed performance was highest at the middle (p = 0.001).

CONCLUSION

Completing baseline assessments in the order of (1) ImPACT, (2) SAC, (3) BESS, and (4) SCAT symptom checklist may improve performance across assessments collectively. Clinicians and researchers should consider completing baseline assessments in this order when possible to potentially aid in optimizing concussion baseline assessment performance and maximize post-concussion comparisons.

High school female basketball athletes exhibit decreased knee-specific choice visual-motor reaction time

Weaker hamstrings muscular forces and lower ratio of the hamstrings/quadriceps muscular forces in female athletes have been identified as modifiable risk factors for anterior cruciate ligament (ACL) injuries. However, sex differences in athletes' ability to react to visual cues (Choice Visual-Motor Reaction Time: VMRT) and to generate knee muscular forces (rate of force development: RFD) immediately following the visual cues were largely unknown. Therefore, the purpose of the study was to examine sex differences in Choice VMRT and RFD. A total of 50 high school basketball athletes (26F/24 M) participated in the study. Subjects sat in the knee dynamometer chair with their knee secured at 70° of knee flexion and performed knee extension or flexion maximum voluntary isometric contractions immediately after they saw the visual cue: "UP" or "DOWN" arrows, respectively. Choice VMRT was defined as the time between the visual cue and the initiation of muscular force development (>5Newtons). RFD was calculated by dividing the changes in forces over the changes in time at four time points (0-50/100/150/200 ms). Peak muscular forces and RFD were normalized to their body mass. Average of three trials in each direction (flexion and extension) in each leg was used for statistical analyses. Females had significantly slower Choice VMRT (p < 0.001-0.027) and lower knee extension RFD at 100 ms (p = 0.005). In addition, females had significantly higher knee flexion/extension ratio than males in late RFD (150 ms and 200 ms) (p < 0.004). The current study has provided additional sensorimotor characteristics of athletes and sexes in addition to their knee muscular characteristics.

Test-Retest Reliability of a Functional Reaction Time Assessment Battery

CONTEXT

Reaction time is commonly assessed postconcussion through a computerized neurocognitive battery. Although this measure is sensitive to postconcussion deficits, it is not clear if computerized reaction time reflects the dynamic reaction time necessary to compete effectively and safely during sporting activities. Functional reaction time assessments may be useful postconcussion, but reliability must be determined before clinical implementation.

OBJECTIVE

To determine the test-retest reliability of a functional reaction time assessment battery and to determine if reaction time improved between sessions.

DESIGN

Cohort.

SETTING

Laboratory.

PARTICIPANTS

Forty-one participants (21 men and 20 women) completed 2 time points. Participants, on average, were 22.5 (2.1) years old, 72.5 (11.9) cm tall, had a mass of 71.0 (13.7) kg, and were mostly right leg and hand dominant (92.7%).

INTERVENTIONS

Participants completed 2 clinical reaction time tests (computerized Stroop and drop stick) and 5 functional reaction time tests (gait, jump landing, single-leg hop, anticipated cut, and unanticipated cut) across 2 sessions. Drop stick and functional reaction time assessments were performed in single (motor task only) and dual task (motor task with cognitive task).

MAIN OUTCOME MEASURES

Reaction time (in seconds) was calculated during all assessments. Test-retest reliability was determined using 2-way mixed-effects intraclass correlation coefficients (3, k). Paired samples t tests compared mean reaction time between sessions.

RESULTS

Test-retest reliability was moderate to excellent for all reaction time outcomes (intraclass correlation coefficients [3, k] range = .766-.925). Several statistically significant between-session mean differences were observed, but effect sizes were negligible to small (d range = 0.05-0.44).

CONCLUSIONS

The functional reaction time assessment battery displayed similar reliability to the standard computerized reaction time assessment battery and may provide important postinjury information, but more research is needed to determine clinical utility.

Slowed driving-reaction time following concussion-symptom resolution

BACKGROUND

Concussed patients have impaired reaction time (RT) and cognition following injury that may linger and impair driving performance. Limited research has used direct methods to assess driving-RT post-concussion. Our study compared driving RT during simulated scenarios between concussed and control individuals and examined driving-RT's relationship with traditional computerized neurocognitive testing (CNT) domains.

METHODS

We employed a cross-sectional study among 14 concussed (15.9 ± 9.8 days post-concussion, mean ± SD) individuals and 14 healthy controls matched for age, sex, and driving experience. Participants completed a driving simulator and CNT (CNS Vital Signs) assessment within 48 h of symptom resolution. A driving-RT composite (ms) was derived from 3 simulated driving scenarios: stoplight (green to yellow), evasion (avoiding approaching vehicle), and pedestrian (person running in front of vehicle). The CNT domains included verbal and visual memory; CNT-RT (simple-, complex-, Stroop-RT individually); simple and complex attention; motor, psychomotor, and processing speed; executive function; and cognitive flexibility. Independent t tests and Hedge d effect sizes assessed driving-RT differences between groups, Pearson correlations (r) examined driving RT and CNT domain relationships among cohorts separately, and p values were controlled for false discovery rate via Benjamini-Hochberg procedures (α = 0.05).

RESULTS

Concussed participants demonstrated slower driving-RT composite scores than controls (mean difference = 292.86 ms; 95% confidence interval (95%CI): 70.18-515.54; p = 0.023; d = 0.992). Evasion-RT (p = 0.054; d = 0.806), pedestrian-RT (p = 0.258; d = 0.312), and stoplight-RT (p = 0.292; d = 0.585) outcomes were not statistically significant after false-discovery rate corrections but demonstrated medium to large effect sizes for concussed deficits. Among concussed individuals, driving-RT outcomes did not significantly correlate with CNT domains (r-range: -0.51 to 0.55; p > 0.05). No correlations existed between driving-RT outcomes and CNT domains among control participants either (r-range: -0.52 to 0.72; p > 0.05).

CONCLUSION

Slowed driving-RT composite scores and large effect sizes among concussed individuals when asymptomatic signify lingering impairment and raise driving-safety concerns. Driving-RT and CNT-RT measures correlated moderately but not statistically, which indicates that CNT-RT is not an optimal surrogate for driving RT.

Classification of Comprehensive Neuro-Ophthalmologic Measures of Postacute Concussion

IMPORTANCE

Symptom-based methods of concussion diagnosis in contact sports result in underdiagnosis and repeated head injury exposure, increasing the risk of long-term disability. Measures of neuro-ophthalmologic (NO) function have the potential to serve as objective aids, but their diagnostic utility is unknown.

OBJECTIVE

To identify NO measures that accurately differentiate athletes with and without concussion.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study was conducted among athletes with and without concussion who were aged 17 to 22 years between 2016 and 2017. Eye movements and cognitive function were measured a median of 19 days after injury among patients who had an injury meeting the study definition of concussion while playing a sport (retrospectively selected from a concussion clinic), then compared with a control group of participants without concussion (enrolled from 104 noncontact collegiate athlete volunteers without prior head injury). Data analysis was conducted from November 2019 through May 2020.

EXPOSURE

Concussion.

MAIN OUTCOMES AND MEASURES

Classification accuracy of clinically important discriminator eye-tracking (ET) metrics. Participants' eye movements were evaluated with a 12-minute ET procedure, yielding 42 metrics related to smooth pursuit eye movement (SPEM), saccades, dynamic visual acuity, and reaction time. Clinically important discriminator metrics were defined as those with significantly different group differences and area under the receiver operator characteristic curves (AUROCs) of at least 0.70.

RESULTS

A total of 34 participants with concussions (mean [SD] age, 19.7 [2.4] years; 20 [63%] men) and 54 participants without concussions (mean [SD] age, 20.8 [2.2] years; 31 [57%] men) completed the study. Six ET metrics (ie, simple reaction time, discriminate reaction time, discriminate visual reaction speed, choice visual reaction speed, and reaction time on 2 measures of dynamic visual acuity 2) were found to be clinically important; all were measures of reaction time, and none were related to SPEM. Combined, these 6 metrics had an AUROC of 0.90 (95% CI, 0.80-0.99), a sensitivity of 77.8%, and a specificity of 92.6%. The 6 metrics remained significant on sensitivity testing.

CONCLUSIONS AND RELEVANCE

In this study, ET measures of slowed visual reaction time had high classification accuracy for concussion. Accurate, objective measures of NO function have the potential to improve concussion recognition and reduce the disability associated with underdiagnosis.

Clinical versus Functional Reaction Time: Implications for Postconcussion Management

PURPOSE

This study aimed to examine the association between clinical and functional reaction time (RT) assessments with and without simultaneous cognitive tasks among healthy individuals.

METHODS

Participants (n = 41, 49% female; 22.5 ± 2.1 yr; 172.5 ± 11.9 cm; 71.0 ± 13.7 kg) completed clinical (drop stick, Stroop) and functional (gait, jump landing, single-leg hop, anticipated cut, unanticipated cut) RT assessments in random order. All RT assessments, except Stroop and unanticipated cut, were completed under single- (movement only) and dual-task conditions (movement and subtracting by 6s or 7s). Drop stick involved catching a randomly dropped rod embedded in a weighted disk. Stroop assessed RT via computerized neurocognitive testing. An instrumented walkway measured gait RT when center-of-pressure moved after random stimulus. All other functional RT assessments involved participants jumping forward and performing a vertical jump (jump landing), balancing on one leg (single-leg hop), or a 45° cut in a known (anticipated cut) or unknown (unanticipated cut) direction. RT was determined when the sacrum moved following random visual stimulus. Pearson correlation coefficients and a 5 × 2 repeated-measures ANOVA compared RT assessments and cognitive conditions.

RESULTS

Stroop RT outcomes did not significantly correlate with functional RT assessments (r range = -0.10 to 0.24). A significant assessment by cognitive task interaction (F4,160 = 14.01; P < 0.001) revealed faster single-task RT among all assessments compared with dual-task (mean differences, -0.11 to -0.09 s; P < 0.001), except drop stick (P = 0.195). Single-leg hop (0.58 ± 0.11 s) was significantly slower compared with jump landing (0.53 ± 0.10 s), anticipated cut (0.49 ± 0.09 s), gait (0.29 ± 0.07 s), and drop stick (0.21 ± 0.03 s; P values ≤ 0.001). Dual-task assessments were significantly slower than single-task assessments (mean difference, 0.08 s; P < 0.001).

CONCLUSIONS

Clinical and functional RT assessments were not correlated with each other, suggesting that sport-like RT is not being assessed after concussion. Functional and dual-task RT assessments may add clinical value and warrant further exploration after concussion.