Background: Grounded in self-determination theory (SDT), this pilot study aimed to test an autonomy-supportive exercise instructing style to promote hedonic (seeking comfort and pleasure) and eudaimonic (seeking to develop the best within one and pursue excellence) orientations, exercise motivation, and psychological well-being of breast cancer survivors. Methods: Twenty-four breast cancer survivors were randomized in either autonomy-supportive exercise instructing style (treatment condition) or usual exercise instructing style (control condition). The study consisted of a pre-intervention session followed by 22 exercise sessions and a post-intervention session. Hedonic and eudaimonic orientations, exercise motivation, and psychological well-being (subjective vitality) measured at baseline and post-intervention sessions. Results: As expected, participants in the treatment condition reported greater eudaimonic and hedonic orientations and subjective vitality compared to the participants in the control condition. The results showed no difference in exercise motivation across conditions. Conclusion: We concluded that the SDT-based intervention was successful in helping breast cancer survivors increase hedonic and eudaimonic orientations and subjective vitality. Practical and theoretical implications, along with limitations and future research suggestions are discussed inside.
