Relationship between sedentary behaviour, physical activity, muscle quality and body composition in healthy older adults

SIR—Sedentary behaviour (SB), defined as time spent sitting or lying, has been shown to be a major modifiable risk factor for chronic disease, disablement and frailty 1 independently physical activity levels (PA) 2, 3. Time spent sitting or lying affects muscle physiology 4, is thought to accelerate sarcopenia 5, and to be a determinant driver of the obesity epidemic 6. These two effects of SB: obesity and low muscle strength appear to potentiate each other to increase risk of disablement and frailty in older adults 7.