Are there different determinants of the frequency, intensity, and duration of physical activity?

The authors of this study explored whether different determinants exist for each of the three components of physical activity (frequency, intensity, and duration). The theoretical model they used was a modified version of the theory of planned behavior. Undergraduate volunteers (N = 170) completed an initial questionnaire and provided self-reports 2 and 4 weeks later of their physical activity during the interval. Hierarchical regression analyses indicated that both intention and self-efficacy explained unique variance in frequency and intensity, but only intention explained unique variance in duration. Further hierarchical regression analyses showed that self-efficacy contributed unique variance to all three components of intention, whereas attitude was implicated only in intended frequency and duration, and affect only in intended intensity. Possible explanations for the emergence of different determinants of the three components are discussed, and directions for future research are suggested.