Physical Activity, Sedentary Behavior, and Skeletal Muscle Strength in Patients With Chronic Kidney Disease: An Isotemporal Substitution Approach

Objective. Insufficient physical activity and excessive sedentary behavior can contribute to decreased skeletal muscle strength, which is strongly associated with increased mortality in patients with chronic kidney disease (CKD). However, the potential impact of replacing sedentary behavior with physical activity on skeletal muscle strength remains unclear in these individuals. The purpose of this study was to examine the associations of physical activity, sedentary behavior, and skeletal muscle strength in patients with CKD using an isotemporal substitution model to estimate the associations on replacing time from one behavior to another while keeping the total time and other behaviors fixed. Methods. A total of 108 patients with CKD (mean age = 65 [SD = 9] y; mean estimated glomerular filtration rate = 57 [SD = 22] mL/min/1.73 m²) participated in this cross-sectional analysis study. The time spent in sedentary behavior, light-intensity physical activity, and moderate- to vigorous-intensity physical activity (MVPA) was assessed using a triaxial accelerometer. Handgrip strength, isometric knee extension strength, and 30-second chair stand test were used to measure skeletal muscle strength. Results. In multivariate analyses (single-factor and partition models), the time spent in MVPA was beneficially associated with both isometric knee extension strength and 30-second chair stand test. Furthermore, the isotemporal substitution model found that replacing 10 min/d of sedentary behavior or light-intensity physical activity with equivalent MVPA time was beneficially associated with both isometric knee extension strength and 30-second chair stand test. Conclusion. These cross-sectional findings indicate that MVPA time is beneficially associated with lower extremity muscle strength and that a slight increase in the MVPA time may contribute to maintaining skeletal muscle strength in patients with CKD. Impact. Increasing the time spent in MVPA (10 min/d) may be a feasible strategy in patients with CKD who have a high prevalence of impaired physical function.