Trajectories of well-being during an exercise randomized controlled trial: The role of exposure and exercise...

We examined how process factors were related to the development of various indicators of well-being during the course of an exercise randomized controlled trial aimed at reducing fatigue among university students. We investigated (a) whether actual exposure to the exercise sessions was related to differences in students' trajectories of well-being, (b) the minimally required exposure to exercise needed before well-being started to differ between the intervention and control condition, and (c) whether exercise experiences (enjoyment and detachment) were related to differences in well-being trajectories. University students with high levels of fatigue were randomly allocated to a 6-week exercise intervention (n = 50) or wait list (n = 49). All participants were measured before, 5 times during, and at the end of the intervention period. Multilevel analyses showed that exercisers with high exposure showed an increase in self-efficacy whereas those with low exposure did not. Effects of exercise on well-being became visible after 2 to 4 weeks during the intervention period and (partly) depended on the extent of psychological detachment. We recommend that both outcomes and process factors throughout the intervention period should be measured in order to better understand "when" and "under what conditions" an exercise intervention works.