Muscle performance and structure in the elderly as studied cross-sectionally and longitudinally.

Longitudinal and cross-sectional studies of muscle performance and structure in the elderly are summarized in this article. Muscle strength and muscle mass decrease with age, mainly due to the loss of muscle fibers. In most studies of the vastus lateralis, the mean fiber area decreases only slightly with a larger reduction in the type II fiber area, with the type I fiber area being constant. However, other fiber area patterns have also been recorded, such as the preserved type II fiber area in the biceps brachii muscle, which is larger than the type I fiber area. An increase in fiber areas was recorded in 76- to 80-year-old men who maintained their physical activity level rather well. The muscle enzyme levels of the muscles studied also vary, and show adaptation with training. In particular, oxidative enzymes seem to be well maintained in old age. General conclusions concerning aging effects should not be drawn from measurements in only one muscle, and the impact of the current physical activity level of the subjects should always be taken into account.