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

OBJECTIVES: We investigated the acoustic startle reflex in recently concussed adolescent athletes compared to healthy controls and those with concussion history (>1 year prior) but no current symptoms. We hypothesized that individuals with recent concussion would have a suppressed startle response compared to healthy controls. METHODS: We conducted a cross-sectional study on 49 adolescent athletes with a recent concussion (n = 20; age: 14.6 ± 1.6 years; 60% female), a concussion history > 1 year prior (n = 16; age: 14.8 ± 2.0 years; 44% female), and healthy controls (n = 13; age: 13.3 ± 2.8 years; 54% female). We measured the eyeblink of the general startle reflex via electromyography activity of the orbicularis oculi muscle using electrodes placed under the right eye. Measurement sessions included twelve 103 decibel acoustic startle probes ~50 milliseconds in duration delivered ~15-25 seconds apart. The primary dependent variable was mean startle magnitude (µV), and group was the primary independent variable. We used a one-way analysis of variance followed by a Tukey post hoc test to compare mean startle magnitude between groups. RESULTS: Mean startle magnitude significantly differed (F = 5.49, P = .007) among the groups. Mean startle magnitude was significantly suppressed for the concussion (P = .01) and concussion history groups (P = .02) compared to healthy controls. There was no significant difference between the recent concussion and concussion history groups (P = 1.00). CONCLUSION: Our results provide novel evidence for startle suppression in adolescent athletes following concussion. The concussion history group had an attenuated startle response beyond resolution of their recovery, suggesting there may be lingering physiological dysfunction.

Running Biomechanics and Clinical Features Among Adolescent Athletes With Lower Leg Chronic Exertional Compartment Syndrome.

OBJECTIVE: To compare clinical measures between patients with chronic exertional compartment syndrome (CECS) and healthy controls and evaluate running biomechanics, physical measurements, and exertional intracompartmental (ICP) changes in adolescent athletes with lower leg CECS. DESIGN: Cross-sectional case-control study. SETTING: Large tertiary care hospital and affiliated injury prevention center. PARTICIPANTS: Forty-nine adolescents with CECS (39 F, 10 M; age: 16.9 ± 0.8 years; body mass index (BMI): 23.1 ± 2.9 kg/m 2 ; symptom duration: 8 ± 12 months) were compared with 49 healthy controls (39 F, 10 M; age: 6.9 ± 0.8 years; BMI: 20.4 ± 3.7 kg/m 2 ). INTERVENTIONS: All participants underwent gait analyses on a force plate treadmill and clinical lower extremity strength and range of motion testing. Patients with chronic exertional compartment syndrome underwent Stryker monitor ICP testing. MAIN OUTCOME MEASURES: Symptoms, menstrual history, and ICP pressures of the patients with CECS using descriptive statistics. Mann-Whitney U and χ 2 analyses were used to compare CECS with healthy patients for demographics, clinical measures, and gait biomechanics continuous and categorical outcomes, respectively. For patients with CECS, multiple linear regressions analyses were used to assess associations between gait biomechanics, lower extremity strength and range of motion, and with ICP measures. RESULTS: The CECS group demonstrated higher mass-normalized peak ground reaction force measures (xBW) compared with controls (0.21 ± 0.05 xBW ( P < 0.001) and were more likely to have impact peak at initial contact ( P = 0.04). Menstrual dysfunction was independently associated with higher postexertion ICP (ß = 14.6; P = 0.02). CONCLUSIONS: The CECS group demonstrated increased total force magnitude and vertical impact transient peaks. In women with CECS, menstrual dysfunction was independently associated with increased postexertion ICP. These biomechanical and physiological attributes may play a role in the development of CECS.

Relationship Between Running Biomechanics and Core Temperature Across a Competitive Road Race.

BACKGROUND: Outdoor races introduce environmental stressors to runners, and core temperature changes may influence runners' movement patterns. This study assessed changes and determined relationships between sensor-derived running biomechanics and core temperature among runners across an 11.27-km road race. HYPOTHESIS: Core temperatures would increase significantly across the race, related to changes in spatiotemporal biomechanical measures. STUDY DESIGN: Cross-sectional cohort study. LEVEL OF EVIDENCE: Level 3. METHODS: Twenty runners (9 female, 11 male; age, 48 ± 12 years; height, 169.7 ± 9.1 cm; mass, 71.3 ± 13.4 kg) enrolled in the 2022 Falmouth Road Race were recruited. Participants used lightweight technologies (ingestible thermistors and wearable sensors) to monitor core temperature and running biomechanics throughout the race. Timestamps were used to align sensor-derived measures for 7 race segments. Observations were labeled as core temperatures generally within normal limits (<38°C) or at elevated core temperatures (≥38°C). Multivariate repeated measures analyses of variance were used to assess changes in sensor-derived measures across the race, with Bonferroni post hoc comparisons for significant findings. Pearson's r correlations were used to assess the relationship between running biomechanics and core temperature measures. RESULTS: Eighteen participants developed hyperthermic core temperatures (39.0°C ± 0.5°C); core temperatures increased significantly across the race (P < 0.01). Kinetic measures obtained from the accelerometers, including shock, impact, and braking g, all significantly increased across the race (P < 0.01); other sensor-derived biomechanical measures did not change significantly. Core temperatures were weakly associated with biomechanics (|r range|, 0.02-0.16). CONCLUSION: Core temperatures and kinetics increased significantly across a race, yet these outcomes were not strongly correlated. The observed kinetic changes may have been attributed to fatigue-related influences over the race. CLINICAL RELEVANCE: Clinicians may not expect changes in biomechanical movement patterns to signal thermal responses during outdoor running in a singular event.

Biomechanical changes identified during a marathon race among high-school aged runners.

BACKGROUND: Despite the increasing popularity of endurance running competitions among adolescent runners, there is currently limited information regarding expected biomechanical changes across the duration of a long-distance running event, and the relationship between young runners' biomechanics and running performance. Wearable technology offers an ecological means to continuously assess runners' biomechanical data during outdoor running competitions. RESEARCH QUESTION: Do adolescent athletes adopt changes in sensor-derived biomechanics throughout a marathon race, and are there relationships between race performance and biomechanical features among young marathoners? METHODS: Fourteen high-school aged runners (9 M, 5 F; age: 16 ± 1 years, height: 170.8 ± 7.5 cm; mass: 63.6 ± 9.4 kg) wore lace-mounted sensors to record step-by-step biomechanics during a marathon race. Official race segment completion times were extracted across 5 race segments (5-K, 15-K, Half Marathon [21.1-K], 35-K, Marathon [42.2-K]). Within-participant repeated measures of covariance (pace) were conducted to assess changes in biomechanics across the race, with Bonferroni post-hoc comparisons. Pearson's r correlations were performed to assess the relationship between race finish times and biomechanics. RESULTS: Pace was significantly slower (p-range: 0.002-0.005), contact times significantly longer, and stride lengths significantly shorter in the final segment compared to middle segments (p-range: 0.003-0.004). The rate of shock accumulation was significantly higher in the final race segment compared to the first three segments (p-range: 0.001-0.002). Moderate relationships existed between finish times and pace (r = -0.63), stride length (r = -0.62), and contact time (r = 0.51). SIGNIFICANCE: Adolescent runners altered their gait patterns in the final marathon segment compared to earlier segments. Spatiotemporal measures were moderately correlated with race finish times, suggesting a link between faster run pace, increased stride lengths, and reduced contact time for improved running performance during an endurance race.

Clinical assessment, treatment, and referral trends for adolescent runners seeking care at an injured runners' clinic.

PURPOSE: Over a 10-year time frame, this study aimed to evaluate diagnosis, treatment, and referral trends for adolescent runners seeking care for running-related injuries (RRIs) at a clinic that specializes in running medicine. METHODS: This study was a retrospective chart review of 392 adolescent runners (2,326 encounters) who sought care for RRIs between the years 2011 and 2021. Descriptive statistics were used to summarize clinical assessments, referrals, assistive devices, and medications prescribed or administered overall and by injury type. Chi-square analyses were used to compare proportions of services rendered across the 10-year time frame. RESULTS: Patients most frequently received manual evaluations or special tests during clinic visits. Most visits resulted in at least one referral (91%), primarily for physical therapy or gait-training. Assistive devices and medications/supplements were offered at only 18% of patient visits. The majority of assessments (X2 = 69.7, p = 0.002), treatments (X2: 23.6-43.8, p: <  0.001-0.003), and referrals (X2 = 132, p <  0.001) were for shin injuries. Larger proportions of nutrition assessments (X2 = 40.7, p <  0.001), interventions (X2 = 26.8, p = 0.003), and referrals (X2 = 27.5, p = 0.002) were performed in or after the year 2015. CONCLUSION: Clinic visits for shin injuries required the most clinical resources per episode of care. There were observed shifts in clinical assessment and treatment approaches to include more expanded nutritional and physiologic considerations.

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

CONTEXT: Single- and dual-task walking gait assessments have been used to identify persistent movement and cognitive dysfunction among athletes with concussions. However, it is unclear whether previous ankle sprain injuries confound these outcomes during baseline testing. The purpose of this study was to determine the effects of (1) ankle sprain history and (2) time since prior ankle sprain injury on single- and dual-task spatiotemporal gait outcomes and cognitive measures. DESIGN: Cross-sectional study. METHODS: We assessed 60 college Division-I athletes (31 with ankle sprain history; 13 females and 18 males, 19.3 [0.8] y; 29 with no ankle sprain history, 14 females and 15 males, 19.7 [0.9] y) who completed injury history forms and underwent concussion baseline testing. Athletes completed single- and dual-task gait assessments by walking back and forth along an 8-m walkway for 40 seconds. Athletes wore a smartphone with an associated mobile application on their lumbar spine to record spatiotemporal gait parameters and dual-task cognitive performance. Separate multivariate analyses of variance were used to assess the effects of ankle sprain injury history on spatiotemporal measures, gait variability, and cognitive performance. We performed a multivariate regression subanalysis on athletes who reported time since injury (n = 23) to assess temporal effects on gait and cognitive performance. RESULTS: Athletes with and without a history of ankle sprains had comparable spatiotemporal and gait variability outcomes during single- (P = .42; P = .13) and dual-task (P = .75; P = .55) conditions. Additionally, ankle sprain injury history did not significantly influence cognitive performance (P = .35). Finally, time since ankle sprain did not significantly affect single- (P = .75) and dual-task gait (P = .69), nor cognitive performance (P = .19). CONCLUSIONS: Ankle sprain injury history did not significantly alter spatiotemporal gait outcomes nor cognitive performance during this common clinical assessment. Future studies may consider including athletes with ankle sprain injury history during concussion assessments.

Outpatient Runners Clinic Visit Trends and Injury Characteristics Among 392 Child and Adolescent Patients: A 10-year Chart Review.

OBJECTIVE: To evaluate clinic visits and running-related injury (RRI) characteristics among child and adolescent runners seeking care at an outpatient clinic over a 10-year time frame. DESIGN: Retrospective chart review. SETTING: Outpatient hospital-affiliated Injured Runners Clinic. PATIENTS: Children and adolescent runners (6-17 years) with RRIs. INDEPENDENT VARIABLES: We examined electronic medical records (EMRs) among child and adolescent patients in the hospital database from 2011 to 2021 to obtain RRI characteristics and key demographic factors. MAIN OUTCOME MEASURES: We assessed volume and frequency of patient visits to the clinic by RRI characteristics. Chi square analyses were used to compare the proportion of clinic visits over time and injury trends by body region and diagnosis. RESULTS: There were 392 patients (sex: 277 F; mean age: 16.1 ± 1.3 years) and an average of 5 clinic visits per diagnosis (5 ± 4 visits; min: 1 visit, max: 31 visits). Number of visits generally increased over time up to 2016 but declined most drastically during the years of the pandemic (2020-2021; χ 2 = 644, P < 0 .001). Of the 654 new injury diagnoses, 77.68% were attributed to repetitive stress. Bone stress injuries to the tibia were the most common RRI (χ 2 = 1940, P < 0 .001; N = 132; 20.2% of all injuries) and constituted most of the clinic visits (χ 2 = 9271, P < 0 .001; N = 591; 25.4% of all visits). CONCLUSION: We identified that adolescents with overuse injuries, particularly bone stress injuries to the tibia, constituted most of the visits to the outpatient healthcare setting. Clinicians should emphasize injury prevention efforts in clinical practice to reduce RRI burden.

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.

Adolescent Marathon Training: Prospective Evaluation of Musculotendinous Changes During a 6-Month Endurance Running Program.

OBJECTIVES: Assess changes in lower extremity musculotendinous thickness, tissue echogenicity, and muscle pennation angles among adolescent runners enrolled in a 6-month distance running program. METHODS: We conducted prospective evaluations of adolescent runners' lower extremity musculotendinous changes at three timepoints (baseline, 3 months, and 6 months) throughout a progressive marathon training program. Two experienced researchers used an established protocol to obtain short- and long-axis ultrasound images of the medial gastrocnemius, tibialis anterior, flexor digitorum brevis, abductor hallicus, and Achilles and patellar tendons. ImageJ software was used to calculate musculotendinous thickness and echogenicity for all structures, and fiber pennation angles for the ankle extrinsic muscles. Repeated measures within-subject analyses of variance were conducted to assess the effect of endurance training on ultrasound-derived measures. RESULTS: We assessed 11 runners (40.7% of eligible runners; 6F, 5M; age: 16 ± 1 years; running experience: 3 ± 2 years) who remained injury-free and completed all ultrasound evaluation timepoints. Medial gastrocnemius muscle (F2,20  = 3.48, P = .05), tibialis anterior muscle (F2,20  = 7.36, P = .004), and Achilles tendon (F2,20  = 3.58, P = .05) thickness significantly increased over time. Echogenicity measures significantly decreased in all muscles (P-range: <.001-.004), and increased for the patellar tendon (P < .001) during training. Muscle fiber pennation angles significantly increased for ankle extrinsic muscles (P < .001). CONCLUSIONS: Adolescent runners' extrinsic foot and ankle muscles increased in volume and decreased in echogenicity, attributed to favorable distance training adaptations across the 6-month timeframe. We noted tendon thickening without concomitantly increased echogenicity, signaling intrasubstance tendon remodeling in response to escalating distance.

Repetitive head injury in adolescent mice: A role for vascular inflammation.

Repetitive mild traumatic brain injury during adolescence can induce neurological dysfunction through undefined mechanisms. Interleukin-1 (IL-1) contributes to experimental adult diffuse and contusion TBI models, and IL-1 antagonists have entered clinical trials for severe TBI in adults; however, no such data exist for adolescent TBI. We developed an adolescent mouse repetitive closed head injury (rCHI) model to test the role of IL-1 family members in post-injury neurological outcome. Compared to one CHI, three daily injuries (3HD) produced acute and chronic learning deficits and emergence of hyperactivity, without detectable gliosis, neurodegeneration, brain atrophy, and white matter loss at one year. Mature IL-1ß and IL-18 were induced in brain endothelium in 3HD but not 1HD, three hit weekly, or sham animals. IL-1ß processing was induced cell-autonomously in three-dimensional human endothelial cell cultures subjected to in vitro concussive trauma. Mice deficient in IL-1 receptor-1 or caspase-1 had improved post-injury Morris water maze performance. Repetitive mild CHI in adolescent mice may induce behavioral deficits in the absence of significant histopathology. The endothelium is a potential source of IL-1ß and IL-18 in rCHI, and IL-1 family members may be therapeutic targets to reduce or prevent neurological dysfunction after repetitive mild TBI in adolescents.