SDT-Based Intervention for Exercise Motivation in Female Students

Study Protocol for a Randomized Controlled Trial of a Self-determination Theory-Based Psychoeducational Intervention to Enhance Autonomous Motivation for Exercise in Female University Students

Physical inactivity, maladaptive exercise motives, and body image concerns are highly prevalent among young adult women and are associated with reduced psychological well-being and increased risk for disordered eating. This study protocol describes a randomized controlled trial designed to evaluate a multi-component psychoeducational intervention integrating Self-Determination Theory principles with functionality-oriented body image strategies to enhance autonomous motivation for exercise and promote psychological well-being among female university students. Female Health Sciences students aged 18-25 will be randomly allocated (1:1) to an experimental or control group following baseline assessment, and outcomes will be evaluated at baseline, post-intervention, and six-week follow-up. The six-session face-to-face intervention incorporates autonomy-supportive communication, competence-building activities, meaningful rationales, choice provision, and supportive relational climates, combined with functionality-based body image content. The primary outcome is autonomous motivation for exercise (BREQ-3; Relative Autonomy Index), and secondary outcomes include basic psychological need satisfaction and frustration, physical activity levels, positive body image, and eating disorder risk. Linear mixed-effects models will be used under an intention-to-treat approach, and mediation analyses will test whether changes in psychological need satisfaction underlie improvements in motivational quality. The intervention is expected to promote healthier motivational regulation, increase physical activity engagement, strengthen positive body image, and reduce maladaptive exercise drivers. Findings aim to inform scalable, theory-driven preventive strategies for improving health and well-being among young women in university settings.

Inclusion Criteria:

• Female sex
• Age between 18 and 25 years
• Enrolled in Health Sciences programs (Physical Activity and Sport Sciences, Physiotherapy, Human Nutrition and Dietetics, Nursing) at Universidad Francisco de Vitoria
• Provision of written informed consent

Exclusion Criteria:

• Current or previous diagnosis of an eating disorder
• Failure to complete baseline or post-intervention questionnaires
• Identification of an eating disorder after enrollment, which triggers referral according to the well-being protocol