Human beings are designed to move. Despite changes in modern lifestyles that have led to a reduction in habitual physical activity in the developed world, this remains an important human biological function. The skeletal muscles, forming one of the largest tissue compartments of the body, are dedicated to this end. The ability to move in the form of athletic performance peaks in the third and fourth decades of life and then progressively declines. Skeletal muscle mass declines by around 30% by the seventh and eighth decades and further losses of up to 50% may occur by the ninth decade and above.¹ This age-related loss of muscle mass has been termed “sarcopaenia”, of Greek origin, meaning “poverty of the flesh”. Sarcopaenia and the loss of muscle strength that is associated with it have important health consequences. Muscle mass and strength are independent predictors of mortality and disability in the elderly,² and are important aetiological factors in falls in frail older people.³ Some loss of muscle mass and strength is almost universal in older people, but varies widely between individuals, particularly in relation to habitual levels of physical activity. The prevalence of “pathological” sarcopaenia in older people is uncertain. Using a cutoff for muscle mass (measured by dual-energy x ray absorption) of two standard deviations below the mean for young healthy adults (analogous to the T score for bone mineral density), a recent study suggested the prevalence to be 13–24% in 60–70-year-olds and over 50% in older people aged ⩾80 years.⁴

Loss of skeletal muscle mass and strength is a particular problem in many chronic diseases affecting older people, particularly diseases such as chronic obstructive pulmonary disease (COPD), where exercise intolerance …