Mindfulness-based stress reduction (MBSR) and aerobic exercise training (AET) programs improve health and well-being. Exercise participation has been related to mindfulness and may be altered by MBSR training.

Purpose This study aimed to compare 8 wk of MBSR, AET, and no-treatment control during the fall season on objectively measured physical activity in healthy adults.

Methods Participants (n = 66) wore an ActiGraph GT3X+ accelerometer for 7 d prerandomization and after 8 wk MBSR or AET interventions, or neither (control). Mean daily minutes (min) of moderate-to-vigorous physical activities (MVPA) were calculated along with weekly time spent in bouts of MVPA ≥10 min (MVPABouts) to assess physical activity sufficient to meet national guidelines. Groups were compared on pairwise changes in outcomes across time. Effect sizes were calculated using Cohen’s d.

Results Sufficient data (≥3 weekdays, ≥1 weekend day, and ≥10 h·d−1) were obtained from 49 participants (18 MBSR, 14 AET, and 17 control). Daily MVPA decreased in all groups from prerandomization to postintervention (August to November); control decreased 17.9 ± 25.7 min·d−1, MBSR decreased 5.7 ± 7.5 min·d−1, and AET decreased 7.4 ± 14.3 min·d−1 (mean ± SD), without significant differences among the groups (all P > 0.05). MVPABouts decreased 77.3 ± 106.6 min·wk−1 in control and 15.5 ± 37.0 min·wk−1 in MBSR (between-group difference: P = 0.08; d = 0.86), whereas it increased by 5.7 ± 64.1 min·wk−1 in AET (compared with control: P = 0.029; d = 0.97; compared with MBSR; P = 0.564; d = 0.29).

Conclusion Data from participants in a randomized controlled trial showed that although AET increases MVPA bouts compared with no treatment, MBSR training may also mitigate the influence of shorter day length and cooler weather on participation in physical activities. Future research is needed to determine how MBSR affects exercise to inform interventions. Interventions combining MBSR and exercise may be particularly successful at increasing physical activity participation.