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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.