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Background: Aerobic exercise has emerged as a useful treatment to improve outcomes among individuals who experience a concussion. However, compliance with exercise recommendations and the effect of exercise volume on symptom recovery require further investigation. Purpose: To examine (1) if an 8-week aerobic exercise prescription, provided within 2 weeks of concussion, affects symptom severity or exercise volume; (2) whether prescription adherence, rather than randomized group assignment, reflects the actual effect of aerobic exercise in postconcussion recovery; and (3) the optimal volume of exercise associated with symptom resolution after 1 month of study. Study Design: Cohort study; Level of evidence, 2. Methods: Individuals randomized to an exercise intervention (n = 17; mean age, 17.2 ± 2.0 years; 41% female; initially tested a mean of 11.3 ± 2.8 days after injury) or standard of care (n = 20; mean age, 16.8 ± 2.2 years; 50% female; initially tested a mean of 10.7 ± 3.2 days after injury) completed an aerobic exercise test within 14 days of injury. They returned for assessments 1 month and 2 months after the initial visit. The aerobic exercise group was instructed to exercise 5 d/wk, 20 min/d (100 min/wk), at a target heart rate based on an exercise test at the initial visit. Participants reported their exercise volume each week over the 8-week study period and reported symptoms at each study visit (initial, 1 month, 2 months). Because of low compliance in both groups, there was no difference in the volume of exercise between the 2 groups. Results: There were no significant symptom severity differences between the intervention and standard-of-care groups at the initial (median Post-Concussion Symptom Inventory, 15 [interquartile range = 10, 42] vs 20 [11, 35.5]; P = .26), 1-month (4 [0, 28] vs 5.5 [0.5, 21.5]; P = .96), or 2-month (6.5 [0, 27.5] vs 0 [0, 4]; P = .11) study visits. Exercise volume was similar between groups (median, 115 [54, 225] vs 88 [28, 230] min/wk for exercise intervention vs standard of care; P = .52). Regardless of group, those who exercised <100 min/wk reported significantly higher symptom severity at the 1-month evaluation compared with those who exercised ≥100 min/wk (median, 1.5 [0, 7.5] vs 12 [4, 28]; P = .03). Exercising ≥160 min/wk successfully discriminated between those with and those without symptoms 1 month after study commencement (classification accuracy, 81%; sensitivity, 90%; specificity, 78%). Conclusion: Greater exercise volume was associated with lower symptom burden after 1 month of study, and an exercise volume >160 min/wk in the first month of the study was the threshold associated with symptom resolution after the first month of the study. Because our observation on the association between exercise volume and symptom level is a retrospective and secondary outcome, it is possible that participants who were feeling better were more likely to exercise more, rather than the exercise itself driving the reduction in symptom severity.

Objective: To examine if self-reported dizziness is associated with concussion symptoms, depression and/or anxiety symptoms, or gait performance within 2 weeks of postconcussion. Design: Cross-sectional study. Setting: Research laboratory. Participants: Participants were diagnosed with a concussion within 14 days of initial testing (N 5 40). Participants were divided into 2 groups based on their Dizziness Handicap Inventory (DHI) score: 36 to 100 5 moderate/severe dizziness and 0 to 35 5 mild/ no dizziness. Interventions: Participants were tested on a single occasion and completed the DHI, hospital anxiety and depression scale (HADS), Patient Health Questionnaire-9 (PHQ-9), and Post-Concussion Symptom Inventory (PCSI). Three different postural control tests were use: modified Balance Error Scoring System, single-/dual-task tandem gait, and a single-/dualtask instrumented steady-state gait analysis. Main Outcome Measures: Comparison of patient-reported outcomes and postural control outcomes between moderate/severe (DHI $ 36) and mild/no (DHI , 36) dizziness groups. Results: Participants with moderate/severe dizziness (n 5 19; age 5 17.1 6 2.4 years; 63% female) reported significantly higher symptom burden (PSCI: 43.0 6 20.6 vs 22.8 6 15.7; P 5 0.001) and had higher median HADS anxiety (6 vs 2; P , 0.001) and depression (6 vs 1; P 5 0.001) symptom severity than those with no/minimal dizziness (n 5 21; age 5 16.5 6 1.9; 38% female). During steady-state gait, moderate/severe dizziness group walked with significantly slower single-task cadence (mean difference 5 4.8 steps/minute; 95% confidence interval 5 0.8, 8.8; P 5 0.02) and dual-task cadence (mean difference 5 7.4 steps/minute; 95% confidence interval 5 0.7, 14.0; P 5 0.04) than no/mild dizziness group. Conclusion: Participants who reported moderate/severe dizziness reported higher concussion symptom burden, higher anxiety scores, and higher depression scores than those with no/mild dizziness. Cadence during gait was also associated with the level of dizziness reported.

Objective: To assess acute cerebrovascular function in concussed adolescents (14-21 years of age), whether it is related to resting cerebral hemodynamics, and whether it recovers chronically. Methods: Cerebral vasoreactivity and autoregulation, based on middle cerebral artery blood flow velocity, was assessed in 28 concussed participants (≤14 days of injury) and 29 matched controls. The participants in the concussion group returned for an 8-week follow-up assessment. Over the course of those 8-weeks, participants recorded aerobic exercise frequency and duration. Results: Between groups, demographic, clinical, and hemodynamic variables were not significantly different. Vasoreactivity was significantly higher in the concussed group (p = 0.02). Within the concussed group, 60% of the variability in resting cerebral blood flow velocity was explained by vasoreactivity and two components of autoregulationfalling slope and effectiveness of autoregulation (adjusted R 2 = 0.60, p < 0.001). Moreover, lower mean arterial pressure, lower responses to increases in arterial pressure, and lower vasoreactivity were significantly associated with larger symptom burden (adjusted R 2 = 0.72, p < 0.01). By the 8-week timepoint, symptom burden, but not vasoreactivity, improved in all but four concussed participants (p < 0.01). 8-week change in vasoreactivity was positively associated with aerobic exercise volume (adjusted R 2 = 0.19, p = 0.02). Interpretation: Concussion resulted in changes in cerebrovascular regulatory mechanisms, which in turn explained the variability in resting cerebral blood flow velocity and acute symptom burden. Furthermore, these alterations persisted chronically despite symptom resolution, but was positively modified by aerobic exercise volume. These findings provide a mechanistic framework for further investigation into underlying cerebrovascular related symptomatology.

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.

Objective: To examine the association between postconcussion exercise volume and changes in depression, anxiety, dizziness, and postural stability. Design: Secondary analysis of a single-site prospective clinical trial. Setting: Cerebrovascular research laboratory. Participants: Participants completed questionnaires and underwent tests of gait and balance within 2 weeks of a concussion (mean = 11 ± 3 days postconcussion) and approximately 1 month later (mean = 41 ± 7 days postconcussion). Exercise volume was tracked by weekly exercise logs. Interventions: On the basis of a previous work classifying exercise volume following concussion, we grouped participants according to self-reported exercise volume between visits as high exercise volume (≥150 min/wk) or low exercise volume (<150 min/wk). Main Outcome Measures: Participants completed assessments evaluating anxiety and depression (Hospital Anxiety and Depression Scale), dizziness (Dizziness Handicap Inventory), and postural stability (tandem gait and modified Balance Error Scoring System). Results: Thirty-eight participants completed the study, of which 22 were in the high exercise volume group (mean = 71 ± 40 min/wk; 16.8 ± 2.1 years; 59% female) and 16 were in the low exercise volume group (mean = 379 ± 187 min/wk; 17.5 ± 2.1 years; 31% female). Although depression symptoms were not significantly different initially (mean difference = 1.5; 95% CI, −0.68 to 3.68; P = .24), the high exercise volume group had significantly lower depression symptom scores at follow-up (mean difference = 3.0; 95% CI, 1.40 to 4.47; P < .001). Anxiety symptoms (mean difference = 2.8; 95% CI, 0.3 to 5.4; P = 0.03), dizziness symptoms (mean difference = 10.9; 95% CI, 0.2 to 21.5; P = .047), single-task tandem gait (mean difference = 3.1 seconds; 95% CI, 0.2 to 6.0; P = .04), and dual-task tandem gait (mean difference = 4.2 seconds; 95% CI, 0.2 to 8.2; P = .04) were significantly better among the high exercise volume group. Conclusion: Greater exercise volumes were associated with lower depression, anxiety, and dizziness symptoms, and faster tandem gait performance. These preliminary findings suggest a potentially beneficial role for exercise within several different domains commonly affected by concussion.

Objective: (1) To examine the effect of social media (SM) use on sleep quality and (2) to determine the effect of SM on competition performance among college athletes. Design: Cross-sectional study. Setting: Two local Division III colleges, MA, USA. Participants: National Collegiate Athletic Association Division III swim and track and field athletes. Intervention: Data were collected onsite through an SM use form, the lifestyle survey, and the Patient-Reported Outcomes Measurement Information System Sleep Disturbance Questionnaire. Participants were divided into 3 groups based on their SM volume: (1) less active SM users (#2 h/d), (2) moderately active SM users (.2-#5 h/d), and (3) active SM users (.5 h/d) for analysis. Main Outcome Measures:Sleep quality and sport performance data collected through publicly available competition results. The independent variable, SM volume (hours of SM use per day over 7 days), was collected using the iPhone screen time function. Results: The cohort consisted of 40 male track and field athletes and 47 female track and field (37, 79%) and swimming (10, 21%) athletes. Mean SM use was 4.6 6 3.4 h/d. The sleep quality of active SM users was worse than less active SM users (P 5 0.033). There was an independent association between increased Facebook time and poor performance after adjusting confounders (adjusted odds ratio: 0.990, 95% confidence interval: 0.981-0.999, P 5 0.049). Conclusions: High SM use has a negative impact on sleep quality and may hinder competition performance among college athletes. These findings may have implications for developing SM use guidelines for college athletes to improve their sleep quality and performance.

Background and Objectives:Aerobic exercise has become a useful method to assist with post-concussion management. Exercise can exacerbate concussion symptoms even when symptoms are not apparent at rest. Few studies have examined the reasons for symptom exacerbation during exercise following a concussion. We had two primary objectives. 1) To delineate cardiopulmonary and cerebrovascular responses to exercise in adolescents and young adults with a concussion and healthy controls. 2) To determine the association between cerebrovascular responses and symptom burden.Methods:We recruited participants with a recent concussion from a sport concussion clinic between 9/1/2018-2/22/2020. They were included if their concussion occurred <3 weeks before initial testing and if they were symptomatic at rest. Participants were excluded if they sustained a concussion in the past year (excluding index injury), reported history of neurological disorders, or were using medications/devices that may alter neurological function. Participants completed a progressive, symptom-limited, sub-maximal exercise protocol on a stationary bike. We assessed heart rate, blood pressure, fraction of end tidal CO2 (FETCO2) and middle cerebral artery blood flow velocity (CBF) and cerebrovascular function (vasoreactivity and autoregulation) at seated rest and during exercise.Results:We conducted 107 exercise tests (40 concussed, 37 healthy participants initially; 30 concussed at follow-up). Concussed participants were tested initially (mean=17.6±2.2 [SD] years old; 55% female; mean=12.5±4.7 days post-concussion) and again 8 weeks later (mean=73.3±9.5 days post-concussion). Control participants (mean=18.3±2.4 years; 62% female) were tested once. FETCO2 increased throughout the exercise protocol as heart rate increased, reached a plateau, and declined at higher exercise intensities. CO2 explained >25% of the variation in resting CBF (R2>0.25; p<0.01) in most (73% individuals). Within the concussion group, resting symptom severity and the heart rate at which FETCO2 reached a plateau explained ∼two-thirds of variation in exercise-induced symptom exacerbation (R2=0.65; FETCO2 β=-1.210±0.517[S.E.], p<0.05). There was a moderate, statistically significant relationship between cerebrovascular responses to CO2 at rest (cerebral vasoreactivity) and cerebrovascular responses to exercise-induced changes in FETCO2 (R2=0.13, p=0.01).Discussion:The arterial CO2 response and symptom exacerbation relationship during post-concussion aerobic exercise may be mediated by increased sensitivity of cerebral vasculature to exercise-related increase in CO2.