Exercise Intolerance After Mild Traumatic Brain Injury Occurs in All Subtypes in the Adult Population.

Thematically grouped symptom clusters are present during the acute timeline of post-mild traumatic brain injuries (mTBI), representing clinical profiles called subtypes. Exercise intolerance has not been evaluated within the subtype classifications and, because guidelines support early submaximal aerobic exercise, further knowledge is required in regard to the exercise capabilities among the concussion subtypes. This cross-sectional study (n = 78) aimed to characterize the presence of exercise intolerance within the clinical subtypes and to explore performance on the Buffalo Concussion Treadmill Test (BCTT) in the adult subacute (2-12 weeks post-injury) mTBI population. All participants were evaluated using the BCTT to determine exercise tolerance. We first used the Neurobehavioral Symptom Inventory (NSI) questionnaire to assign each participant a primary subtype(s). To further explore all five subtypes (headache, cognitive, vestibular, ocular motor, and mood), participants were assessed using a multitude of thematically grouped assessments including self-reported questionnaires, clinical tests of vestibular and ocular motor function, balance function, and computerized cognitive testing. Thirty-seven (47%) subjects were exercise tolerant and 41 (53%) were exercise intolerant. There was no difference in the distribution of primary subtypes between the exercise tolerant and exercise intolerant groups. In addition, no significant differences were found between the exercise tolerant and exercise intolerant groups on other thematically grouped subtype assessments. The exercise intolerant group had a significantly higher resting heart rate (HR), lower percentage of age-predicted maximum HR achieved, lower Borg Rate of Perceived Exertion (RPE), and could walk on the treadmill for less time (lower duration) compared with the exercise tolerant group. The current findings suggest that exercise intolerance is common and pervasive across all five mTBI subtypes. A comprehensive mTBI assessment should include evaluation for exercise intolerance regardless of the primary clustering of symptoms and across patient populations. Therefore, early referral to physical therapists, athletic trainers, or medical clinics that can perform the BCTT may be helpful to initiate appropriate exercise prescriptions for patients with mTBI.

Assessing the Effects of Mild Traumatic Brain Injury on Vestibular Home Exercise Performance with Wearable Sensors.

After a mild traumatic brain injury (mTBI), dizziness and balance problems are frequently reported, affecting individuals' daily lives and functioning. Vestibular rehabilitation is a standard treatment approach for addressing these issues, but its efficacy in this population remains inconclusive. A potential reason for suboptimal outcomes is the lack of objective monitoring of exercise performance, which is crucial for therapeutic success. This study utilized wearable inertial measurement units (IMUs) to quantify exercise performance in individuals with mTBI during home-based vestibular rehabilitation exercises. Seventy-three people with mTBI and fifty healthy controls were enrolled. Vestibular exercises were performed, and IMUs measured forehead and sternum velocities and range of motions. The mTBI group demonstrated a slower forehead peak angular velocity in all exercises, which may be a compensatory strategy to manage balance issues or symptom exacerbation. Additionally, the mTBI group exhibited a larger forehead range of motion during specific exercises, potentially linked to proprioceptive deficits. These findings emphasize the usefulness of utilizing IMUs to monitor the quality of home-based vestibular exercises for individuals with mTBI and the potential for IMUs improving rehabilitation outcomes.

Assessment of balance in people with mild traumatic brain injury using a balance systems model approach.

PURPOSE: Measuring persistent imbalance after mTBI is challenging and may include subjective symptom-reporting as well as clinical scales. Clinical assessments for quantifying balance following mTBI have focused on sensory orientation. It is theorized that balance control goes beyond sensory orientation and also includes subdomains of anticipatory postural adjustments, reactive postural control, and dynamic gait. The Mini Balance Evaluation Systems Test (Mini-BESTest) is a validated balance test that measures balance according to these subdomains for a more comprehensive assessment. The purpose of this study was to compare Mini-BESTest total and subdomain scores after subacute mTBI with healthy controls. METHODS: Symptomatic mTBI (n = 90, 20 % male, age=36.0 ± 12.0, 46.3.4 ± 22.1 days since injury) and healthy control (n = 45, 20 % male, age=35.4 ± 12.5) participants completed the Mini-BESTest for balance. Mini-BESTest between-group differences were evaluated using Wilcoxon rank-sum tests. RESULTS: The mTBI group (Median[minimum,maximum]) had a significantly worse Mini-BESTest total score than the healthy controls (24[18,28] vs 27[23-28], p < 0.001). The mTBI group performed significantly worse in 3 of the 4 subdomains compared to the healthy controls: reactive postural control: 5[2-6] vs 6[3-6], p = 0.003; sensory orientation: 6[5,6] vs 6[6], p = 0.005; dynamic gait: 8[5-10] vs 9[8-10], p < 0.001. There was no significance difference between groups in the anticipatory postural adjustments domain (5[3-6] vs 5[3-6], p = 0.12). CONCLUSIONS: The Mini-BESTest identified deficits in people with subacute mTBI in the total score and 3 out of 4 subdomains, suggesting it may be helpful to use in the clinic to identify balance subdomain deficits in the subacute mTBI population. In combination with self-reported assessments, the mini-BESTest may identify balance domain deficits in the subacute mTBI population and help guide treatment for this population.

Symptoms and Central Sensory Integration in People With Chronic mTBI: Clinical Implications.

INTRODUCTION: Balance deficits in people with chronic mild traumatic brain injury (mTBI; ≥3 months post-mTBI), thought to relate to central sensory integration deficits, are subtle and often difficult to detect. The purpose of this study was to determine the sensitivity of the instrumented modified clinical test of sensory integration for balance (mCTSIB) in identifying such balance deficits in people with symptomatic, chronic mTBI and to establish the associations between balance and mTBI symptom scores in the chronic mTBI group. METHODS: The Institutional Review Board approved these study methods. Forty-one people with chronic mTBI and balance complaints and 53 healthy controls performed the mCTSIB (eyes open/closed on firm/foam surfaces; EoFi, EcFi, EoFo, and EcFo) with a wearable sensor on their waist to quantify sway area (m2/s4). Sensory reweighting variables were calculated for the firm and foam stance conditions. A stopwatch provided the clinical outcome for the mCTSIB (time). Each participant completed the Neurobehavioral Symptom Inventory (NSI), which quantifies mTBI-related symptoms and provides a total score, as well as sub-scores on affective, cognitive, somatic, and vestibular domains. RESULTS: The mTBI group reported significantly higher symptom scores across each NSI sub-score (all Ps < .001). The mTBI group had a significantly larger sway area than the control group across all mCTSIB conditions and the mTBI group had significantly higher sensory reweighting scores compared to the control group on both the firm (P = .01) and foam (P = .04) surfaces. Within the mTBI group, the NSI vestibular score significantly related to the mCTSIB sway area EcFi (r = 0.38; P = .02), sway area EcFo (r = 0.43; P = .006), sensory reweighting firm (r = 0.33; P = .04), and sensory reweighting foam (r = 0.38; P = .02). The average sway area across the 4 mCTSIB conditions was significantly (area under the curve: 0.77; P < .001) better at differentiating groups than the mCTSIB clinical total score. The average sway area across the 4 mCTSIB conditions had a sensitivity of 73% and a specificity of 71%. The clinical mCTSIB outcome scores were not different between groups. CONCLUSION: People with chronic mTBI appear to have central sensory integration deficits detectable by instrumented measures of postural assessment. These findings suggest that central sensory integration should be targeted in rehabilitation for people with chronic mTBI.

Central sensorimotor integration assessment reveals deficits in standing balance control in people with chronic mild traumatic brain injury.

Imbalance is common following mild Traumatic Brain Injury (mTBI) and can persist months after the initial injury. To determine if mTBI subjects with chronic imbalance differed from healthy age- and sex-matched controls (HCs) we used both the Central SensoriMotor Integration (CSMI) test, which evaluates sensory integration, time delay, and motor activation properties and the standard Sensory Organization Test (SOT). Four CSMI conditions evoked center-of-mass sway in response to: surface tilts with eyes closed (SS/EC), surface tilts with eyes open viewing a fixed visual surround (SS/EO), visual surround tilts with eyes open standing on a fixed surface (VS/EO), and combined surface and visual tilts with eyes open (SS+VS/EO). The mTBI participants relied significantly more on visual cues during the VS/EO condition compared to HCs but had similar reliance on combinations of vestibular, visual, and proprioceptive cues for balance during SS/EC, SS/EO, and SS+VS/EO conditions. The mTBI participants had significantly longer time delays across all conditions and significantly decreased motor activation relative to HCs across conditions that included surface-tilt stimuli with a sizeable subgroup having a prominent increase in time delay coupled with reduced motor activation while demonstrating no vestibular sensory weighting deficits. Decreased motor activation compensates for increased time delay to maintain stability of the balance system but has the adverse consequence that sensitivity to both internal (e.g., sensory noise) and external disturbances is increased. Consistent with this increased sensitivity, SOT results for mTBI subjects showed increased sway across all SOT conditions relative to HCs with about 45% of mTBI subjects classified as having an "Aphysiologic" pattern based on published criteria. Thus, CSMI results provided a plausible physiological explanation for the aphysiologic SOT pattern. Overall results suggest that rehabilitation that focuses solely on sensory systems may be incomplete and may benefit from therapy aimed at enhancing rapid and vigorous responses to balance perturbations.

The effects of augmenting traditional rehabilitation with audio biofeedback in people with persistent imbalance following mild traumatic brain injury.

Complaints of non-resolving imbalance are common in individuals with chronic mild traumatic brain injury (mTBI). Vestibular rehabilitation therapy may be beneficial for this population. Additionally, wearable sensors can enable biofeedback, specifically audio biofeedback (ABF), and aid in retraining balance control mechanisms in people with balance impairments. In this study, we described the effectiveness of vestibular rehabilitation therapy with and without ABF to improve balance in people with chronic mTBI. Participants (n = 31; females = 22; mean age = 40.9 ± 11 y) with chronic (>3 months) mTBI symptoms of self-reported imbalance were randomized into vestibular rehabilitation with ABF (n = 16) or without ABF (n = 15). The intervention was a standard vestibular rehabilitation, with or without ABF, for 45 min biweekly for 6 weeks. The ABF intervention involved a smartphone that provided auditory feedback when postural sway was outside of predetermined equilibrium parameters. Participant's completed the Post-Concussion Symptom Scale (PCSS). Balance was assessed with the sensory organization test (SOT) and the Central Sensorimotor Integration test which measured sensory weighting, motor activation, and time delay with sway evoked by surface and/or visual surround tilts. Effect sizes (Hedge's G) were calculated on the change between pre-and post-rehabilitation scores. Both groups demonstrated similar medium effect-sized decreases in PCSS and large increases in SOT composite scores after rehabilitation. Effect sizes were minimal for increasing sensory weighting for both groups. The with ABF group showed a trend of larger effect sizes in increasing motor activation (with ABF = 0.75, without ABF = 0.22) and in decreasing time delay (with ABF = -0.77, without ABF = -0.52) relative to the without ABF group. Current clinical practice focuses primarily on sensory weighting. However, the evaluation and utilization of motor activation factors in vestibular rehabilitation, potentially with ABF, may provide a more complete assessment of recovery and improve outcomes.

Implementation and Adoption of Telerehabilitation for Treating Mild Traumatic Brain Injury.

BACKGROUND AND PURPOSE: Multimodal physical therapy for mild traumatic brain injury (mTBI) has been shown to improve recovery. Due to the coronavirus disease-2019 (COVID-19) pandemic, a clinical trial assessing the timing of multimodal intervention was adapted for telerehabilitation. This pilot study explored feasibility and adoption of an in-person rehabilitation program for subacute mTBI delivered through telerehabilitation. METHODS: Fifty-six in-person participants-9 males; mean (SD) age 34.3 (12.2); 67 (31) days post-injury-and 17 telerehabilitation participants-8 males; age 38.3 (12.7); 61 (37) days post-injury-with subacute mTBI (between 2 and 12 weeks from injury) were enrolled. Intervention included 8, 60-minute visits over 6 weeks and included subcategories that targeted cervical spine, cardiovascular, static balance, and dynamic balance impairments. Telerehabilitation was modified to be safely performed at home with minimal equipment. Outcome measures included feasibility (the number that withdrew from the study, session attendance, home exercise program adherence, adverse events, telerehabilitation satisfaction, and progression of exercises performed), and changes in mTBI symptoms pre- and post-rehabilitation were estimated with Hedges' g effect sizes. RESULTS: In-person and telerehabilitation had a similar study withdrawal rate (13% vs 12%), high session attendance (92% vs 97%), and no adverse events. The telerehabilitation group found the program easy to use (4.2/5), were satisfied with care (4.7/5), and thought it helped recovery (4.7/5). The telerehabilitation intervention was adapted by removing manual therapy and cardiovascular portions and decreasing dynamic balance exercises compared with the in-person group. The in-person group had a large effect size (-0.94) in decreases in symptoms following rehabilitation, while the telerehabilitation group had a moderate effect size (-0.73). DISCUSSION AND CONCLUSIONS: Telerehabilitation may be feasible for subacute mTBI. Limited ability to address cervical spine, cardiovascular, and dynamic balance domains along with underdosage of exercise progression may explain group differences in symptom resolution.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A392 ).

Free-living gait does not differentiate chronic mTBI patients compared to healthy controls.

BACKGROUND: Physical function remains a crucial component of mild traumatic brain injury (mTBI) assessment and recovery. Traditional approaches to assess mTBI lack sensitivity to detect subtle deficits post-injury, which can impact a patient's quality of life, daily function and can lead to chronic issues. Inertial measurement units (IMU) provide an opportunity for objective assessment of physical function and can be used in any environment. A single waist worn IMU has the potential to provide broad/macro quantity characteristics to estimate gait mobility, as well as more high-resolution micro spatial or temporal gait characteristics (herein, we refer to these as measures of quality). Our recent work showed that quantity measures of mobility were less sensitive than measures of turning quality when comparing the free-living physical function of chronic mTBI patients and healthy controls. However, no studies have examined whether measures of gait quality in free-living conditions can differentiate chronic mTBI patients and healthy controls. This study aimed to determine whether measures of free-living gait quality can differentiate chronic mTBI patients from controls. METHODS: Thirty-two patients with chronic self-reported balance symptoms after mTBI (age: 40.88 ± 11.78 years, median days post-injury: 440.68 days) and 23 healthy controls (age: 48.56 ± 22.56 years) were assessed for ~ 7 days using a single IMU at the waist on a belt. Free-living gait quality metrics were evaluated for chronic mTBI patients and controls using multi-variate analysis. Receiver operating characteristics (ROC) and Area Under the Curve (AUC) analysis were used to determine outcome sensitivity to chronic mTBI. RESULTS: Free-living gait quality metrics were not different between chronic mTBI patients and controls (all p > 0.05) whilst controlling for age and sex. ROC and AUC analysis showed stride length (0.63) was the most sensitive measure for differentiating chronic mTBI patients from controls. CONCLUSIONS: Our results show that gait quality metrics determined through a free-living assessment were not significantly different between chronic mTBI patients and controls. These results suggest that measures of free-living gait quality were not impaired in our chronic mTBI patients, and/or, that the metrics chosen were not sensitive enough to detect subtle impairments in our sample.

Career Head Impact Exposure Profile of Canadian University Football Players.

This study quantified head impact exposures for Canadian university football players over their varsity career. Participants included 63 players from one team that participated in a minimum of 3 seasons between 2013 and 2018. A total of 127,192 head impacts were recorded from 258 practices and 65 games. The mean (SD) number of career impacts across all positions was 2023.1 (1296.4), with an average of 37.1 (20.3) impacts per game and 7.4 (4.4) impacts per practice. The number of head impacts that players experienced during their careers increased proportionally to the number of athletic exposures (P < .001, r = .57). Linebackers and defensive and offensive linemen experienced significantly more head impacts than defensive backs, quarterbacks, and wide receivers (P ≤ .014). Seniority did not significantly affect the number of head impacts a player experienced. Mean linear acceleration increased with years of seniority within defensive backs and offensive linemen (P ≤ .01). Rotational velocity increased with years of seniority within defensive backs, defensive and offensive linemen, running backs, and wide receivers (P < .05). These data characterize career metrics of head impact exposure for Canadian university football players and provide insights to reduce head impacts through rule modifications and contact regulations.

Exploring persistent complaints of imbalance after mTBI: Oculomotor, peripheral vestibular and central sensory integration function.

BACKGROUND: Little is known on the peripheral and central sensory contributions to persistent dizziness and imbalance following mild traumatic brain injury (mTBI). OBJECTIVE: To identify peripheral vestibular, central integrative, and oculomotor causes for chronic symptoms following mTBI. METHODS: Individuals with chronic mTBI symptoms and healthy controls (HC) completed a battery of oculomotor, peripheral vestibular and instrumented posturography evaluations and rated subjective symptoms on validated questionnaires. We defined abnormal oculomotor, peripheral vestibular, and central sensory integration for balance measures among mTBI participants as falling outside a 10-percentile cutoff determined from HC data. A X-squared test associated the proportion of normal and abnormal responses in each group. Partial Spearman's rank correlations evaluated the relationships between chronic symptoms and measures of oculomotor, peripheral vestibular, and central function for balance control. RESULTS: The mTBI group (n = 58) had more abnormal measures of central sensory integration for balance than the HC (n = 61) group (mTBI: 41% -61%; HC: 10%, p's < 0.001), but no differences on oculomotor and peripheral vestibular function (p > 0.113). Symptom severities were negatively correlated with central sensory integration for balance scores (p's < 0.048). CONCLUSIONS: Ongoing balance complaints in people with chronic mTBI are explained more by central sensory integration dysfunction rather than peripheral vestibular or oculomotor dysfunction.

Head Impact Telemetry System's Video-based Impact Detection and Location Accuracy.

PURPOSE: This study aimed to quantify the Head Impact Telemetry (HIT) System's impact detection and location measurement accuracy using an impact biomechanics data set paired with video of high school football special teams plays. METHODS: The head impact biomechanics data set and video were collected from 22 high school football players, wearing HIT System instrumented helmets, competing in 218 special teams plays over a single high school football season. We used two separate video analysis approaches. To quantify the impact detection accuracy, we evaluated the video for head impacts independently of the impact data collection triggers collected by the HIT System. Video-observed impacts matched to valid and invalid head impacts by the HIT System algorithm were categorized as true positives, false positives, false negatives, and true negatives. To quantify impact location accuracy, we analyzed video-synchronized head impacts for impact location independent of the HIT System's impact location measurement and quantified the estimated percent agreement of impact location between the HIT System recorded impact location and the impact location observed on video. RESULTS: The HIT System's impact-filtering algorithm had 69% sensitivity, 72% specificity, and 70% accuracy in categorizing true and non-head impact data collection triggers. The HIT System agreed with video-observed impact locations on 64% of the 129 impacts we analyzed (unweighted k = 0.43, 95% confidence interval = 0.31-0.54). CONCLUSION: This work provides data on the HIT System's impact detection and location accuracy during high school football special teams plays using game video analysis that has not been previously published. Based on our data, we believe that the HIT System is useful for estimating population-based impact location distributions for special teams plays.

Single-Legged Hop and Single-Legged Squat Balance Performance in Recreational Athletes With a History of Concussion.

CONTEXT: Researchers have suggested that balance deficiencies may linger during functional activities after concussion recovery. OBJECTIVE: To determine whether participants with a history of concussion demonstrated dynamic balance deficits as compared with control participants during single-legged hops and single-legged squats. DESIGN: Cross-sectional study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 15 previously concussed participants (6 men, 9 women; age = 19.7 ± 0.9 years, height = 169.2 ± 9.4 cm, mass = 66.0 ± 12.8 kg, median time since concussion = 126 days [range = 28-432 days]) were matched with 15 control participants (6 men, 9 women; age = 19.7 ± 1.6 years, height = 172.3 ± 10.8 cm, mass = 71.0 ± 10.4 kg). INTERVENTION(S): During single-legged hops, participants jumped off a 30-cm box placed at 50% of their height behind a force plate, landed on a single limb, and attempted to achieve a stable position as quickly as possible. Participants performed single-legged squats while standing on a force plate. MAIN OUTCOME MEASURE(S): Time to stabilization (TTS; time for the normalized ground reaction force to stabilize after landing) was calculated during the single-legged hop, and center-of-pressure path and speed were calculated during single-legged squats. Groups were compared using analysis of covariance, controlling for average days since concussion. RESULTS: The concussion group demonstrated a longer TTS than the control group during the single-legged hop on the nondominant leg (mean difference = 0.35 seconds [95% confidence interval = 0.04, 0.64]; F2,27 = 5.69, P = .02). No TTS differences were observed for the dominant leg (F2,27 = 0.64, P = .43). No group differences were present for the single-legged squat on either leg (P ≥ .11). CONCLUSIONS: Dynamic balance-control deficits after concussion may contribute to an increased musculoskeletal injury risk. Given our findings, we suggest that neuromuscular deficits currently not assessed after concussion may linger. Time to stabilization is a clinically applicable measure that has been used to distinguish patients with various pathologic conditions, such as chronic ankle instability and anterior cruciate ligament reconstruction, from healthy control participants. Whereas the single-legged squat may not sufficiently challenge balance control, future study of the more dynamic single-legged hop is needed to determine its potential diagnostic and prognostic value after concussion.

Influence of Self-reported Fatigue and Sex on Baseline Concussion Assessment Scores.

BACKGROUND: Baseline concussion assessments are advocated to provide an objective preinjury point of comparison for determining the extent of postconcussion neurological deficits and to assist with return-to-activity decision making. Many factors, including testing environment, proctor availability, and testing group size, can influence test accuracy and validity; however, it is unknown how self-reported fatigue affects test scores. PURPOSE: To investigate the influence of self-reported fatigue and patient sex on baseline concussion assessment scores. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Participants included 494 healthy Division I college student-athletes (221 women, 273 men; mean ± SD age, 20.0 ± 1.3 years). During preseason baseline testing, participants were asked to rate their fatigue on a scale from 0 to 100 based on how they normally feel and function each day (0, completely exhausted; 100, completely awake and alert). Each participant then completed a multimodal baseline concussion assessment, including a graded symptom checklist (number of symptoms endorsed and total symptom severity score), Standardized Assessment of Concussion (SAC), Balance Error Scoring System (BESS), and CNS Vital Signs computerized neurocognitive testing. Multiple linear regressions tested whether self-reported fatigue and sex predicted baseline concussion examination scores. RESULTS: Athletes with higher self-reported fatigue levels (ß = -0.014, P < .01) and female athletes (ß = -0.216, P < .01) reported more total symptoms. Being male (ß = 0.856, P < .01) increased the likelihood of endorsing zero symptoms versus any symptoms by a factor of 2.40. Women also had significantly higher SAC scores (ß = 0.569, P < .001), BESS scores (ß = -2.747, P < .001), and CNS Vital Signs summary scores (ß = 4.506, P < .001). SAC, BESS, and CNS Vital Signs scores were not predicted by fatigue level (P > .05). CONCLUSION: Female athletes and fatigued athletes endorsed more symptoms and higher symptom severity at baseline. Using total symptom endorsement and total symptom severity scores as part of the postinjury management is a common practice. The current data suggest that levels of reported exhaustion can influence concussion assessment scores meant to represent a healthy baseline and likely would interfere with postinjury assessment scores.

Head Impact Locations in U.S. High School Boys' and Girls' Soccer Concussions, 2012/13-2015/16.

This study describes concussions and concussion-related outcomes sustained by high school soccer players by head impact location, sex, and injury mechanism. Data were obtained for the 2012/13-2015/16 school years from the National High School Sports-Related Injury Surveillance System, High School RIO™. This Internet-based sports injury surveillance system captures data reported by athletic trainers from an annual average of 162 U.S. high schools. Data were analyzed to describe circumstances of soccer concussion (e.g., symptomology, symptom resolution, and return-to-play time) by impact location (i.e., front- [face included], back-, side-, and top-of-the-head) and sex. Most concussions were from front-of-the-head impacts (boys, 30.5%; girls, 34.0%). Overall, 4.1 ± 2.2 and 4.6 ± 2.3 symptoms were reported in boys and girls, respectively. In boys, symptom frequency was not associated with head impact location (p = 0.66); an association was found in girls (p = 0.02), with the highest symptom frequency reported in top-of-the-head impacts (5.4 ± 2.2). Head impact location was not associated with symptom resolution time (boys, p = 0.21; girls, p = 0.19) or return-to-play time (boys, p = 0.18; girls, p = 0.07). Heading was associated with 28.0% and 26.5% of concussions in boys and girls, respectively. Most player-player contact concussions during heading occurred from side-of-the-head impacts (boys, 49.4%; girls, 43.2%); most heading-related ball contact concussions occurred from front-of-the-head (boys, 41.4%; girls, 42.6%) and top-of-the-head (boys, 34.5%; girls, 36.9%) impacts. Head impact location was generally independent of symptom resolution time, return-to-play time, and recurrence among high school soccer concussions. However, impact location may be associated with reported symptom frequency. Further, many of these clinical concussion descriptors were associated with sex.

Can Functional Movement Assessment Predict Football Head Impact Biomechanics?

PURPOSE: The purposes of this study was to determine functional movement assessments' ability to predict head impact biomechanics in college football players and to determine whether head impact biomechanics could explain preseason to postseason changes in functional movement performance. METHODS: Participants (N = 44; mass, 109.0 ± 20.8 kg; age, 20.0 ± 1.3 yr) underwent two preseason and postseason functional movement assessment screenings: 1) Fusionetics Movement Efficiency Test and 2) Landing Error Scoring System (LESS). Fusionetics is scored 0 to 100, and participants were categorized into the following movement quality groups as previously published: good (≥75), moderate (50-75), and poor (<50). The LESS is scored 0 to 17, and participants were categorized into the following previously published movement quality groups: good (≤5 errors), moderate (6-7 errors), and poor (>7 errors). The Head Impact Telemetry (HIT) System measured head impact frequency and magnitude (linear acceleration and rotational acceleration). An encoder with six single-axis accelerometers was inserted between the padding of a commercially available Riddell football helmet. We used random intercepts general linear-mixed models to analyze our data. RESULTS: There were no effects of preseason movement assessment group on the two Head Impact Telemetry System impact outcomes: linear acceleration and rotational acceleration. Head impact frequency did not significantly predict preseason to postseason score changes obtained from the Fusionetics (F1,36 = 0.22, P = 0.643, R = 0.006) or the LESS (F1,36 < 0.01, P = 0.988, R < 0.001) assessments. CONCLUSIONS: Previous research has demonstrated an association between concussion and musculoskeletal injury, as well as functional movement assessment performance and musculoskeletal injury. The functional movement assessments chosen may not be sensitive enough to detect neurological and neuromuscular differences within the sample and subtle changes after sustaining head impacts.

Concussion Mechanisms and Activities in Youth, High School, and College Football.

Our purpose was to determine concussion mechanism and activity differences among three cohorts of football players: youth, high school, and college. Participants in this prospective cohort study were youth (ages 5-14 years, 118 teams, 310 team-seasons), high school (96 teams, 184 team-seasons), and college (34 teams, 71 team-seasons) football players. Athletic trainers collected athlete-exposure (AE) and concussion data during the 2012-2014 seasons. Injury mechanism referred to the object that made contact with the concussed player, resulting in the concussion. Injury activity referred to the type of football-specific activity that the player was involved in when the concussion was sustained. Injury proportion ratios (IPR) compared distributions of concussion mechanisms and activities among age levels. A total of 1429 concussions were reported over 1,981,284 AE across all levels (Rate: 0.72/1000AE). Overall, most concussions were caused by player contact (84.7%). During games, a greater proportion of youth football concussions (14.7%) were caused by surface contact than high school (7.3%, IPR = 2.02; 95% confidence interval [CI]: 1.10-3.72) and college (7.1%, IPR = 2.07, 95% CI: 1.02-4.23) football. Compared with college football concussions (90.2%), a smaller proportion of youth (80.0%, IPR = 0.89, 95% CI: 0.79-0.99) and high school (83.2%, IPR = 0.92, 95% CI: 0.86-0.99) football concussions were caused by player contact. A greater proportion of game youth football concussions (42.1%) occurred while an individual was being tackled than occurred in high school (23.2%, IPR = 1.81, 95% CI: 1.34-2.45) and college (23.0%, IPR = 1.83, 95% CI: 1.29-2.62) football. Findings were similar during practices. Compared with college football game concussions (15.8%), a smaller proportion of youth (6.3%, IPR = 0.40, 95% CI: 0.17-0.93) and high school (9.5%, IPR = 0.60, 95% CI: 0.38-0.95) football game concussions occurred while an individual was being blocked. Concussion mechanism and activity differences should be considered when developing concussion prevention and sport-safety methods specific to different age levels, in order to maximize effectiveness.

Effect of the mandible on mouthguard measurements of head kinematics.

Wearable sensors are becoming increasingly popular for measuring head motions and detecting head impacts. Many sensors are worn on the skin or in headgear and can suffer from motion artifacts introduced by the compliance of soft tissue or decoupling of headgear from the skull. The instrumented mouthguard is designed to couple directly to the upper dentition, which is made of hard enamel and anchored in a bony socket by stiff ligaments. This gives the mouthguard superior coupling to the skull compared with other systems. However, multiple validation studies have yielded conflicting results with respect to the mouthguard׳s head kinematics measurement accuracy. Here, we demonstrate that imposing different constraints on the mandible (lower jaw) can alter mouthguard kinematic accuracy in dummy headform testing. In addition, post mortem human surrogate tests utilizing the worst-case unconstrained mandible condition yield 40% and 80% normalized root mean square error in angular velocity and angular acceleration respectively. These errors can be modeled using a simple spring-mass system in which the soft mouthguard material near the sensors acts as a spring and the mandible as a mass. However, the mouthguard can be designed to mitigate these disturbances by isolating sensors from mandible loads, improving accuracy to below 15% normalized root mean square error in all kinematic measures. Thus, while current mouthguards would suffer from measurement errors in the worst-case unconstrained mandible condition, future mouthguards should be designed to account for these disturbances and future validation testing should include unconstrained mandibles to ensure proper accuracy.

Laboratory Evaluation of the gForce Tracker™, a Head Impact Kinematic Measuring Device for Use in Football Helmets.

This study sought to compare a new head impact-monitoring device, which is not limited to specific helmet styles, against reference accelerometer measurements. Laboratory controlled impacts were delivered using a linear pneumatic impactor to a Hybrid III headform (HIII) fitted with a football helmet and the impact monitoring device (gForce Tracker-GFT) affixed to the inside of the helmet. Linear regression analyses and absolute mean percent error (MAPE) were used to compare the head impact kinematics measured by the GFT to a reference accelerometer located at the HIII's center of mass. The coefficients of determination were strong for the peak linear acceleration, peak rotational velocity, and HIC15 across all impact testing locations (r(2) = 0.82, 0.94, and 0.70, respectively), but there were large MAPE for the peak linear acceleration and HIC15 (MAPE = 49 ± 21% and 108 ± 58%). The raw GFT was accurate at measuring the peak rotational velocity at the center of mass of the HIII (MAPE = 9%). Results from the impact testing were used to develop a correction algorithm. The coefficients of determination for all impact parameters improved using the correction algorithm for the GFT (r(2) > 0.97), and the MAPE were less than 14%. The GFT appears to be a suitable impact-monitoring device that is not limited to specific styles of football helmets, however, correction algorithms will need to be developed for each helmet style.

Biomechanical research on bowed string musicians: a scoping study.

UNLABELLED: Performing arts biomechanics is concerned with quantifying the musculoskeletal demands of artistic tasks. The growing body of related research has prompted this scoping study, solely focused on quantitative research, to summarize the state of the science, identify knowledge gaps, and identify opportunities for future research. OBJECTIVES: To identify, summarize, and categorize quantitative research on the biomechanics of violin, viola, cello, and double bass players, using scoping study methodology. METHODS: Established scoping study methodology was used to identify and categorize existing research. We identified 74 articles for review. Of these, 34 met our scoping study criteria and were included in this study. RESULTS: Twenty-one of the 34 articles that met the scoping criteria were published since 2000. Investigations using electromyography (16 studies) and kinematics (15 studies) comprise the bulk of the research. Two studies employed force transducers for data collection. Violinists were the most frequently studied musicians (22 studies) and double bass players were the least (1 study). Fewer than half of the studies used solely professional musicians as their subjects (13 studies). CONCLUSIONS: This scoping study confirmed that quantitative biomechanical research into bowed string musicians has been performed with increasing frequency and that there are voids in the research, particularly in investigating mechanisms of injury and protective strategies. Currently, arts biomechanics research is largely descriptive in nature. There are few studies that investigate protective strategies, although it is expected that the field will progress to incorporate this type of research.