A Randomized Clinical Trial of a Self-Determination Theory-Based Intervention on Physical Activity of Women Aged 30-45 Years

Background: Despite the existence of much evidence about the importance and impact of physical activity in maximizing the various dimensions of health, steps have been taken to increase physical activity in the continuation of regular physical activity in women who have not been very successful. Materials and Methods: To investigate the effect of SDT-based intervention on physical activity and motivation drivers, this Randomized Clinical Trial parallel design was conducted in a comprehensive health center of Damghan at the northeast IRAN, 2017-2018. In this research, 114 women (age 30-45 years, non-pregnant, physical activity without medical prohibition, body mass index less than 35 (kg / m2) were randomly allocated in two groups: intervention and control. Physical activity and motivation drivers were studied as a study outcome. The MPAM-R questionnaire was completed via interviews with all participants. The mean scores of the intragroup and intergroup components at the beginning, one and three months later (5% alpha error and 80% power) were assessed. Results: Among the drivers of physical activity through the MPAM-R questionnaire, the effect of the "pleasure and interest" component in increasing physical activity of women in the SDT group, and "fitness" in the control group were statistically significant. Also, between the number of aerobic steps a person took while walking, the mean distance walked, and finally, the average calorie consumed by a person through daily physical activity each day after the study increased in SDT-based intervention group compared to the onset of the study and this increase continued for three months after the intervention. Discussion and Conclusion: Although SDT-based interventions can be effective in stabilizing and maintaining physical activity and similar health behaviors, lack of providing autonomy-supporting environments and lack of implementing SDT-based RCT and quasi-experimental interventions in the cultural and social context, etc. given the demographic and contextual variables and other social and cultural components related to health make it difficult to judge on the results and generalize them into other populations.