BackgroundBoth reducing sitting and increasing physical exercise promote health but exercising more does not necessarily reduce sitting time. One reason for this non-dependency may be that different aspects of exercise motivation are differently related to sitting time. Identifying the type of exercise motivation that would also be associated with sitting time can help to reduce sitting indirectly through increased exercise, thus bringing greater benefits.MethodsThe present study explored the association between quality of motivations toward physical activity with physical activity and sitting (...) time in a total of 373 adults. The short version of international physical activity questionnaire was used for measuring physical activity and sitting time. Reasons for exercising regularly were measured with the Self-Regulated Questionnaire–Exercise, including four regulation subscales to assess regulation styles. Confirmatory factor analysis was used to test the four subscales of SRQ-E with the data obtained using AMOS v.23. Then, structural equation model with maximum likelihood estimates was used to test the hypothesized model.ResultsThe results indicated that only intrinsic motivation, but not identified, introjected or external motivation, toward physical activity predicted both physical activity and sitting time. Higher intrinsic motivation toward physical activity was associated with both higher physical activity and lower sitting time. In addition, physical activity was a mediator for lower sitting time when the source was intrinsic motivation.ConclusionPrevious studies have shown low between and within participant correlation between sitting time and physical activity, and interventions have generally failed to both increase physical activity while decreasing sitting time. The present cross-sectional results suggest that targeting increased physical activity by increased intrinsic motivation has the potential to both increase physical activity and decrease sitting time. (shrink)