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

SIMPLE SUMMARY: The role of daily time spent sedentary and in different intensities of physical activity (PA) for maintenance of muscle health is currently unclear. Therefore, we investigated the impact of reallocating time spent in different PA intensities on a sarcopenia risk score (SRS) in older adults, while considering PA type (muscle strengthening activities, MSA) and protein intake. In the present study, we show for the first time that reallocating sedentary time with at least light-intensity PA was significantly related to a lower SRS, which remained evident after adjustment by PA type (MSA) and protein intake. Similarly, reallocating time in light- to moderate-to-vigorous-intensity PA was related to a significantly lower SRS. Our results emphasize the importance of displacing sedentary behaviours for more active pursuits, where PA of even light intensities may alleviate age-related deteriorations of muscle health in older adults. ABSTRACT: The role of daily time spent sedentary and in different intensities of physical activity (PA) for the maintenance of muscle health currently remains unclear. Therefore, we investigated the impact of reallocating time spent in different PA intensities on sarcopenia risk in older adults, while considering PA type (muscle strengthening activities, MSA) and protein intake. In a sample of 235 community-dwelling older adults (65–70 years), a sarcopenia risk score (SRS) was created based on muscle mass assessed by bioimpedance, together with handgrip strength and performance on the five times sit-to-stand (5-STS) test assessed by standardized procedures. Time spent in light-intensity PA (LPA), moderate-to-vigorous PA (MVPA), and being sedentary was assessed by accelerometry, and PA type (MSA) by self-report. Linear regression models based on isotemporal substitution were employed. Reallocating sedentary time to at least LPA was significantly (p < 0.05) related to a lower SRS, which remained evident after adjustment by PA type (MSA) and protein intake. Similarly, reallocating time in LPA by MVPA was related to a significantly (p < 0.05) lower SRS. Our results emphasize the importance of displacing sedentary behaviours for more active pursuits, where PA of even light intensities may alleviate age-related deteriorations of muscle health in older adults.