Abstract: Objective: To explore the influence of perceived social support on the physical activity level of breast cancer patients in the rehabilitation period, aiming to provide a reference for improving the level of physical activity in patients. Methods: A total of 230 breast cancer patients during rehabilitation from a tertiary grade A hospital in Shandong province from January to July 2024 were selected using convenience sampling. The International Physical Activity Questionnaire-Long, Perceived Social Support Scale, Exercise Self-Efficacy Scale, and Cognitive Appraisal of Health Scale were used for investigation. A structural equation model was established to examine the mediating effects, and the Bootstrap method was used for testing. Results: Perceived social support and exercise self-efficacy had direct positive effects on physical activity level (β=0.078, 0.160, both P<0.001), while negative health cognition evaluation had a direct negative effect (β=-0.276, P<0.001). The direct effect of perceived social support on physical activity level accounted for 23.1% of the total effect, while the indirect effects of negative health cognition evaluation, exercise self-efficacy, and their chain mediating effect accounted for 47.5%, 20.1%, and 9.3%, respectively. Conclusion: The variables in the Self-Determination Theory have multiple pathways of influence on the physical activity level of patients. The primary pathway involves understanding how social support influences physical activity levels through negative cognitive evaluations. Clinical nursing should pay attention to patients with negative health cognition evaluation and enhance their physical activity level by establishing positive health cognition evaluation.

Key words: breast cancer; physical activity; self-efficacy; perceived social support; health cognitive assessment