Effects of Reallocating Time Spent in Different Physical Activity Intensities on Sarcopenia Risk in Older European Adults: An Isotemporal Substitution Analysis

Sammanfattning

Introduction: Age-related changes in muscular quantity and quality reduce the independence and quality of life of older adults (Breen and Phillips, 2013). Physical activity (PA) is one of the most effective strategies to improve muscular health and sedentary time is recognized as a risk factor for muscular degradation. Identifying how different physical intensities impact muscular health among older adults is vital for their health and life quality. Aim: This thesis investigates the effect of reallocating time spent in different physical activity intensities on indicators of muscle health in older European adults using an isotemporal substitution analysis. Method & Material: Participants were European older men and women aged 65-79 years (N =991). PA intensity was recorded using accelerometery and the intensities were divided into sedentary (SED), light PA (LPA) and, moderate-to-vigorous PA (MVPA). Muscular health outcomes (1) Skeletal muscle mass index (SMI) was assessed using DXA-scan and (2) handgrip strength (HG) was assessed using a handheld dynamometer. Sarcopenia risk score (SRS) were based on the two components merged together. Statistical analysis was conducted as linear regression based on isotemporal substitution modelling. Results: The analysis revealed that replacing a period of 30 minutes of SED with a corresponding period of LPA was associated to a significantly lower SRS and higher SMI, with no significant effect on HG strength. The second finding was that reallocating time in both SED orLPA with MVPA was associated with a significantly lower SRS, higher SMI and HG. Conclusion: The present thesis supports the reduction of time spent sedentary replaced by any other intensity to reduce the risk of sarcopenia in older adults.However, in order to obtain beneficial effects on both muscle mass and muscle strength in older adults, engagement in MVPA should be recommended.