Examining Whether Exercise Preference and Tolerance Moderate the Within-Subject Association Between Physical Activity Intention and Next-Day Moderate to Vigorous Physical Activity.

Background: Physical activity (PA) intentions may predict future PA engagement, such that when intentions for PA are strong, an individual may be more likely to engage in PA compared with when intentions for PA are weak. However, intentions do not always translate into behavior, a phenomenon known as the intention-behavior gap. Individual differences in exercise preference (predisposition for high-intensity exercise) and tolerance (ability to continue exercising at higher intensity) may explain this gap. This study examined whether exercise preference and tolerance moderate the within-subject association between PA intention and next-day moderate to vigorous PA (MVPA) using ecological momentary assessment and accelerometry.

Methods: Exercise preference and tolerance were assessed at baseline using a validated questionnaire. A 14-day smartphone-based ecological momentary assessment protocol captured PA intentions each evening, and next-day MVPA was assessed via accelerometry. Multilevel linear regression models (days [level 1] nested within-people [level 2]) assessed within-subject associations between PA intention and next-day MVPA, along with cross-level interaction effects of exercise preference and tolerance.

Results: Data from 62 US adults (mean age = 39 y, SD = 4.29 y) were analyzed. A negative within-subject main effect of PA intention on next-day MVPA was observed (β = -0.20, P < .001), while exercise preference positively moderated this relationship (β = 0.04, P < .001). Exercise tolerance was not a significant moderator.

Conclusions: Exercise preference may influence the intention-behavior gap, suggesting that those who prefer high-intensity exercise are more likely to translate PA intentions into next-day MVPA.