What requirement did participants have in the Sallis et al. 1999 study?

In the Sallis et al. 1999 study, participants were required to complete a semester-long course. This structure was essential for the study's aim to assess the impacts of a structured educational program on physical activity levels. The semester-long course provided a comprehensive framework, allowing participants to engage deeply with the content over an extended period. It also facilitated systematic tracking of changes in behavior and understanding of physical activity, which are crucial for evaluating the effectiveness of the intervention.

Other options, while involving significant commitments, do not align with the specific requirements outlined in the study. For instance, attending weekly workshops or engaging in daily physical training would not provide the same level of structured learning and could lead to varied interpretations of commitment. Similarly, participating in online fitness challenges lacks the focused educational component that was central to the study's design. Hence, the semester-long course was vital for the participants' thorough engagement with the intervention's material.