Moderate-to-vigorous physical activity promotion and grip strength improvement in Chinese community-dwelling older adults: a 12-month pragmatic intervention study

Abstract Background While increasing moderate-to-vigorous physical activity (MVPA) enhances muscular health through metabolic and vascular adaptations, its association with muscle strength improvement remains unclear, especially in real-world contexts. This study therefore aimed to investigate the longitudinal relationship between changes in MVPA and handgrip strength (HGS) to inform lifestyle guidelines and promote healthy ageing. Methods A pragmatic intervention study enrolled 4344 Chinese community-dwelling adults aged rld contexts. This study therefore aimed to investigate the longitudinal physical activity energy expenditure (PAEE, kJ/kg/day) were continuously monitored via wearable devices. HGS was measured upon enrollment and at 3-, 6- and 12-month follow-ups. During each follow-up, we performed latent class growth analysis (LCGA) to characterize longitudinal patterns of MVPA change (ΔMVPA), and robust linear regression models to evaluate the associations between ΔMVPA trajectories and HGS changes. At the 12-month endpoint, we employed restricted cubic spline analysis to characterize a dose–response association. We also analysed the relationship between PAEE and HGS after accounting for MVPA. Results Participants wore the activity tracker for 75, 151 and 282 valid days and achieved 9.5%, 30.9% and 65.1% increase in MVPA during each follow-up, respectively. LCGA identified distinct ΔMVPA trajectories over time and further revealed the temporal pattern of association between ΔMVPA trajectories and HGS changes, with non-significant directional changes at 6 months, and significant differences by 12 months, where increasers demonstrating a 1.88 kg gain (95% CI: 1.29–2.47) and accelerators a 3.51 kg gain (95% CI: 2.58–4.45) compared to maintainers. Moreover, we established a dose–response relationship as 0.66 kg (95%CI: 0.51–0.82) HGS improvement per 10 min/day MVPA increase, with stronger associations observed in females and those with lower baseline HGS or MVPA levels. PAEE showed no independent association with HGS improvement. Conclusion This study revealed time- and dose-dependent associations of MVPA promotion with muscle strength improvement, without additional association from PAEE, highlighting the necessity of engaging and maintaining MVPA despite age-related barriers, particularly for females, inactive individuals and those with low strength.