Intrinsic rewards predict exercise via behavioral intentions for initiators but via habit strength for maintainers

Regular exercise is thought to involve both reflective (e.g., intention) and automatic (e.g., habit) mechanisms. Intrinsic motivation is a reflective factor in exercise initiation; we propose that the experience of intrinsic exercise rewards (enjoyment; stress reduction) may come to function as a factor in exercise automaticity, or habit, and therefore of exercise maintenance. The current studies evaluate whether the relationship between intrinsic exercise rewards and exercise is mediated by behavioral intention for those newer to exercise (initiators) but mediated by behavioral habit strength for longer term exercisers (maintainers). In 2 studies, self-reported exercise stage (initiation vs. maintenance), intrinsic exercise rewards, intentions, and habit strength were measured at baseline. For outcomes, Study 1 concurrently assessed self-reported exercise in a large sample of U.S. college students (n = 463), and Study 2 prospectively assessed objective activity using accelerometers for 1 month in a U.S. college student and staff population (n = 114). Moderated mediation analyses resulted in support of the hypotheses: Habit strength significantly mediated the relationship between intrinsic rewards and exercise for maintainers in Studies 1 and 2 (unstandardized indirect effect = 7.66 and 0.04, respectively; p < .05) but less strongly for initiators in Study 1 and not at all for initiators in Study 2. Intentions mediated the relationship for initiators (unstandardized indirect effect = 0.94 and 0.02, respectively; p < .05) but not for maintainers, as expected. We concluded that intrinsic rewards may promote exercise repetition via intentional or reflective means in initiation but via habit strength in maintenance. Interventions that foster intrinsic exercise rewards may promote exercise maintenance through habitual action.