Muscle mass and strength: relation to function in population studies.

The use of the term sarcopenia to describe the age-related loss in skeletal muscle and its functional consequences is relatively recent. However, interest in the relationship of muscle mass to strength and function predates the concept of sarcopenia as researchers have attempted to understand differences in mass and strength between men and women, young and old. Most of these studies are cross-sectional comparisons in which muscle mass and strength tend to be linearly related, so that those with more muscle tend to be stronger. This article focuses instead on some potential problems with the sarcopenia-function association in old age and presents what little data exist from longitudinal population studies addressing the effect of sarcopenia over time.