Explaining physical activity levels from a self-efficacy perspective: The Physical Activity Counseling trial

Background. The Physical Activity Counseling (PAC) trial compared the effects of a 13-week primary care physical activity (PA) intervention that incorporated a PA counselor into a health care practice compared to a control condition on PA over a 25-week period and showed group differences in PA were present at 6 and 13 weeks. Purpose: The main purpose was to examine the mediating effect of 6-week task and barrier self-efficacy on the intervention versus control group/ 13-week PA relationships. A secondary purpose was to determine whether task and barrier self-efficacy were significantly related to PA throughout the trial for both groups. Method. Participants were primarily sedentary individuals who received a 2- to 4-min PA intervention from their primary care provider, after which they were randomly assigned to the intervention (n = 61) or control condition (n = 59). Self-reported PA and task (barrier) self-efficacy measures were obtained during (i.e., baseline, 6 and 13 weeks) and after (i.e., 19 and 25 weeks) the intervention in both groups. Results: Six-week task and barrier self-efficacy had a small mediating effect. Furthermore, barrier self-efficacy had a significant relationship with PA throughout the trial, whereas the relationship between task self-efficacy and PA became significantly weaker as the trial progressed. Conclusions: PAC interventions among primarily sedentary individuals should be partly based on barrier and task self-efficacy. However, the stability of the task self-efficacy/PA relationship needs further examination.