Isolated and Combined Effects of Sedentary Behaviour and Physical Activity on Muscle Strength in Older Adults: A Prospective Cohort Study

ABSTRACT Aim We aim the isolated and combined effects of sedentary behaviour exposure time and physical activity levels on muscle strength in older adults. Design This prospective observational cohort study, analytical in nature, using exploratory survey methods and physical performance testing. With 5‐year longitudinal follow‐up (2015–2020). Methods A total of 459 older adults participated in the baseline, with a total of 224 being included/located again in the follow‐up. We evaluate muscle strength using handgrip tests and sit‐to‐stand tests. The international physical activity questionnaire was used to measure physical activity and sedentary behaviour. Generalised Estimation Equations tested both independent and combined effects, reporting results as β coefficients and confidence intervals. Results Older adults exhibiting low sedentary behaviour displayed enhanced handgrip strength compared to those with high sedentary behaviour. Notably, older adults who were sufficiently active with low sedentary behaviour, sufficiently active with high sedentary behaviour, and insufficiently active with low sedentary behaviour showed increased handgrip strength compared to their counterparts who were insufficiently active with high sedentary behaviour. This trend was consistent for lower limb strength. Conclusion Interventions that encourage a reduction in sedentary behaviour and an increase in physical activity are essential to maintain muscle strength among older adults. Implications for Practice The findings of this study underscore the importance of addressing both sedentary behaviour and physical activity levels in clinical interventions aimed at preserving muscle strength in older adults. Routine assessments of physical activity and sedentary behaviour could help tailor personalised exercise programs, potentially enhancing functional independence and reducing the risk of frailty and disability in older patients. Patient or Public Contribution Patients were involved in the sample of the study. Reporting Method This study was conducted in accordance with the Strengthening Research in Observational Studies in Epidemiology (STROBE) guidelines.