Process evaluation and proximal impact of an affect-based exercise intervention among adolescents.

The objective of this study was to evaluate the implementation and proximal impact of an intervention designed to enhance adolescents' affective experience during Physical Education (PE). Healthy adolescents (N = 74) were randomly assigned to an affect-based or a traditional exercise prescription. Intervention logs, observations and interviews documented the implementation of the intervention. Participants completed a 30-min exercise task at an intensity that felt "good" to them before and after the intervention. Study procedures were implemented successfully and students enjoyed study participation. The intervention had no impact on exercise intensity during PE or during the "feels-good" exercise task. Among adolescents who manifested a negative affective response to moderate-intensity exercise at baseline, the selected intensity during the "feels-good" task increased over time. The intervention may have been too weak to impact behavior over and above a high-quality PE program. The results do suggest, however, that reluctant exercisers may choose to exercise at a higher intensity after experiencing a high-quality PE program in combination with heart rate monitoring.