Consistent exercise timing as a strategy to increase physical activity: A feasibility study

Observational research suggests that consistent exercise timing could be leveraged to promote moderate-to-vigorous physical activity (MVPA) among adults with obesity. However, the feasibility and acceptability of prescribed consistent exercise timing in a free-living setting is unknown. The purpose of this study was to assess the feasibility and acceptability of prescribed consistent exercise timing in a free-living setting among inactive adults with obesity (primary) and to compare MVPA timing prescriptions and characterize exercise barriers/facilitators (secondary).

Using a within-subjects design, inactive adults with obesity (n=15) were randomized in counterbalanced order to three 3-wk exercise timing conditions separated by 2-wk washout periods: 1) consistent morning, 2) consistent evening, and 3) choice timing (control). Feasibility was assessed using prespecified benchmarks. Acceptability and preferred timing were assessed with questionnaires post-intervention. Secondarily, exercise timing and MVPA were assessed via accelerometry and nightly surveys and barriers/facilitators were assessed with nightly surveys.

All feasibility benchmarks were achieved (e.g., timing adherence = 69.9% via accelerometry and 87.4% via self-report (target: ≥60%)). Consistent exercise timing was acceptable (mean rating = 3.7 of 5 (target: ≥3.5)). Choice was the most popular prescription. There were medium- to large-sized effects (partial η² of 0.09-0.16) of condition on MVPA; MVPA was higher during the morning and evening conditions versus choice condition. Facilitators were similar across conditions, while some barriers were time specific.

Prescribed exercise timing in a free-living setting appears feasible and acceptable. While choice timing was most preferred, consistent timing appeared most effective for increasing MVPA. Data warrant larger trials to test the efficacy and mechanisms of consistent exercise timing as a translational strategy for promoting MVPA. Pending findings from a fully powered randomized trial, practitioners interested in promoting MVPA among their patients or clients could consider encouraging exercise at a consistent time day-to-day.