Background: Current recommendations for sport-related concussion uniformly emphasize the importance of physical activity. However, specifics of this recommendation remain vague and do not account for an exercise dosage or compliance. Purposes: First, we examined if an 8-week individualized sub-symptom threshold aerobic exercise prescription, initiated within the first two weeks of concussion, alleviates symptom severity or affects the amount of exercise performed during the study. Second, we examined whether prescription adherence, rather than randomized group assignment, reflects the actual impact of aerobic exercise in post-concussion recovery. Methods: For this single-site prospective randomized clinical trial, participants completed an aerobic exercise test within 14 days of injury, and were randomized to an individualized aerobic exercise program or standard-of-care, and returned for assessments 1 month and 2 months after the initial visit (Table 1). The aerobic exercise group was instructed to exercise 5 days/week, 20 minutes/day, at a target heart rate based on an exercise test at the initial visit. Participants reported their symptom exercise volume each week over the 8-week study period, and reported symptoms at each study visit (initial, 1 month, 2 month). Results: Initial symptom severity was not different between randomized groups (Figure 1A), and no significant differences in symptom severity were found at the 4-week (Figure 1B) or 8-week (Figure 1C) assessment. In addition, there was no significant differences between groups for average weekly exercise volume during the first four weeks (Figure 2A) or second four weeks (Figure 2B) of the study. During the first four weeks of the study, 65% (n=11/17) of the exercise intervention participants were compliant with their exercise recommendation (≥100 min/week), compared to 45% (n=9/20) of the standard-of-care group (p=0.33). During the second four weeks of the study, 71% (n=12/17) of the exercise prescription group exercised ≥100 min/week, compared to 55% (n=11/20) of the standard-of-care group (p=0.50). When grouped by exercise volume, the group who exercised ≥100 minutes/week during the first month of the study reported significantly lower symptom severity scores than those who exercised <100 minutes/week (Figure 3B), despite similar initial symptom severity scores (Figure 3A). Conclusion: Participant randomization within 14 days of concussion did not lead to a significant reduction in symptoms, or greater exercise volume. Given that greater exercise volume was associated with lower symptoms after one month of the study, researchers and clinicians should pay particular attention to adherence to aerobic exercise programs for the treatment of concussion. [Table: see text][Figure: see text][Figure: see text][Figure: see text]
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