Health-Promoting or Involuntary? Heterogeneous Effects of Physical Activity Type and Frequency on Depression Among Older Chinese Adults

Background Physical activity (PA) is widely recognized as a protective factor for depression in older adults. However, limited research has examined how different types and frequencies of PA may have heterogeneous psychological effects depending on behavioral motivation and structural constraints. This study investigates the interaction between PA type, participation frequency, and depressive symptoms among older Chinese adults, with a particular focus on the psychological consequences of involuntary intensive physical activity (IPA). Methods Data were drawn from the 2020 China Health and Retirement Longitudinal Study (CHARLS), including 5,472 respondents aged 65 and older. Participants reported the frequency of engaging in vigorous (IPA), moderate (MPA), and light physical activity (LPA). Depressive symptoms were assessed using the 10-item Center for Epidemiological Studies Depression Scale (CESD-10). Multivariate linear and logistic regressions were conducted to examine the dose–response relationships between PA types and depression. Further analyses stratified by hukou status, medical insurance type, and cohabitation were used to assess the conditional effects of IPA based on behavioral purposes (work, exercise, entertainment). Results Daily participation in LPA was associated with significantly lower depression scores ( β = −0.70, p  = 0.007; OR = 0.87, p  = 0.04). MPA showed a protective effect only with daily frequency ( β = −0.43, p  = 0.02). In contrast, engaging in IPA five to six days per week ( β  = 1.45, p  = 0.001) and daily ( β  = 0.53, p  = 0.04) was positively associated with depressive symptoms. Stratified analysis revealed that in rural residents, those with rural insurance, and older adults living alone, work-related IPA was significantly linked to higher depression scores, while exercise- or entertainment-driven IPA showed no such association. Conclusions The mental health effects of physical activity among older adults vary by activity type, frequency, and behavioral context. Regular LPA and MPA appear to be protective, whereas high-frequency IPA—especially when performed involuntarily for subsistence—may increase psychological burden. These findings highlight the importance of distinguishing health-promoting exercise from involuntary labor when designing age-appropriate mental health interventions.