Billing, Lauren2017-11-272017-11-272017-06https://hdl.handle.net/11299/191393University of Minnesota Ph.D. dissertation. June 2017. Major: Kinesiology. Advisor: Beth Lewis. 1 computer file (PDF); vii, 150 pages.Approximately 20.8% of U.S. adults participate in the recommended levels of physical activity (PA) despite the health benefits. Researchers have begun to examine the importance of affect for adopting and maintaining PA. However, few studies have examined how strategies aimed at facilitating positive PA-related affect can influence PA adherence. The current prospective, randomized controlled intervention trial examined the efficacy of a 12-week affective intervention focused on enhancing PA-related affect relative to a behavioral comparison. Participants included healthy low-active adults (n = 40). PA, PA-related affect, and several psychosocial variables were assessed at baseline, 12 weeks, and 16 weeks. Participants in the affective intervention demonstrated increases in objectively measured PA at 12 weeks relative to the behavioral comparison after controlling for baseline ƒ(1,28)=14.764, p < .005. However, there were no between group differences on self-reported PA at 12 or 16 weeks. After controlling for baseline, participants in the affective intervention reported increases in positive Pre-PA affect ƒ(1,26)=5.485, p < .05, and reported marginal increases in affect during PA ƒ(1,26)=3.037, p = .094, relative to the behavioral comparison. Additionally, participants in the affective intervention reported marginal increases in PA enjoyment relative to the behavioral comparison at 16 weeks ƒ(1,32)=3.68, p = .064. These findings provide initial evidence that teaching low-active individuals strategies to increase positive PA-related affect before and during PA is efficacious for increasing PA. Future studies with larger samples, and real-time assessment strategies are needed to further understand the efficacy of PA-related affect interventions.ensport and exercise psychologyThesis or Dissertation