The defnition of physical activity in the literature on sports practice is highly heterogeneous. This article provides evidence of the extent to which the inclusion of walking, which is one of the most frequent types of physical activity, and the minimum frequency used to consider a person a practitioner affect the conclusions about the correlates of physical activity practice and frequency. To this end, we compared participation and frequency models by applying different measures of physical activity. We found that the activities included under the defnition of physical activity play a relevant role in terms of the effects of the covariates in both the participation and frequency models. However, the minimum frequency used to define a person as a practitioner is not associated with significant changes in the effects of the correlates. These conclusions may have relevant policy implications in terms of designing measures to promote participation in physical activity.