Abstract
The purpose of this study is to investigate the relationship between physical activity and exercise self-efficacy among college students and to examine the mediating effects of loneliness and body image. Through an analysis of parallel mediating effects, the intrinsic mechanisms underlying these variables are revealed and provide theoretical support for promoting healthy behaviours among college students. The study, conducted in April 2025, employed a cross-sectional design to survey college students across northeast, North, central, East, and South China. A total of 1102 valid questionnaires were collected. The level of physical activity was assessed using the Physical Activity Rating Scale (PARS-3). Exercise self-efficacy was measured using the Exercise Self-Efficacy Scale. Body image was assessed using the Physical Self-Esteem Scale (PSPP), and loneliness was calculated using the UCLA Loneliness Inventory (3rd edition). The data were analysed using SPSS 27 software for descriptive statistics, correlation analyses, and mediation effect analyses. A significant direct positive correlation was found between physical activity and exercise self-efficacy (β = 0.2313, p < 0.001). Furthermore, loneliness and body image played important mediating roles in the relationship between physical activity and exercise self-efficacy. Specifically, physical activity indirectly improved exercise self-efficacy by reducing loneliness (β=-0.124, p < 0.001) and enhancing body image (β = 0.383, p < 0.001). The mediating effect accounted for 32.1% of the total impact, and the mediating effect of body image (28.5%) was significantly more potent than that of loneliness (3.5%). This study reveals the mechanism by which physical activity indirectly increases college students' sense of exercise self-efficacy by reducing loneliness and improving body image. This finding shows the importance of focusing on individual psychological states when promoting physical activity. Interventions should promote both positive body image and a favourable social environment to improve college students' exercise self-efficacy and overall psychological well-being.