Associations Among Physical Exercise, Social Support, and Meaning in Life in College Students: An Actor–Partner Interdependence Model

Background: Physical exercise is known to promote positive psychological functioning among college students; however, its relationship with meaning in life within naturally occurring friendship dyads remains underexplored. This study examined both actor and partner associations between physical exercise, social support, and meaning in life. Methods: A cross-sectional dyadic survey was conducted among 415 friendship dyads (830 Chinese college students, aged 17–23 years). Participants completed validated measures of physical exercise, perceived social support, and meaning in life. Intraclass correlations, Pearson correlations, actor–partner interdependence models (APIMs), and an indistinguishable APIM mediation model were applied to assess within-dyad nonindependence, actor and partner effects, and indirect pathways through social support. Results: Intraclass correlations revealed within-dyad similarities in physical exercise, social support, and meaning in life, with ICCs of 0.101, 0.188, and 0.253, respectively. The constrained indistinguishable mediation model demonstrated acceptable fit: χ²(6) = 12.81, p = 0.046; CFI = 0.973; TLI = 0.933; RMSEA = 0.052; SRMR = 0.028. Physical exercise was positively associated with social support at both the actor level (B = 0.150, p < 0.001) and partner level (B = 0.095, p < 0.001). Social support, in turn, was positively linked to meaning in life at both actor (B = 0.174, p < 0.001) and partner levels (B = 0.206, p < 0.001). Direct effects of physical exercise on meaning in life remained significant for both actor (B = 0.055, p = 0.001) and partner pathways (B = 0.067, p < 0.001). Bootstrap analyses confirmed significant total indirect effects for actors (B = 0.046, 95% CI [0.030, 0.063]) and partners (B = 0.047, 95% CI [0.032, 0.065]). Conclusions: Physical exercise is associated with meaning in life not only via intrapersonal pathways but also through interpersonal pathways within friendship dyads. Social support serves as a key mediating factor in this relationship.