Intramuscular variation of fiber types in the brachial biceps and the lateral vastus muscles of elderly men: how representative is a small biopsy sample?

The aim of the study was to investigate the reliability of the distribution of muscle fiber types determined in small fragments of human skeletal muscle. Fiber-type distribution was analyzed in small areas, equivalent to a needle biopsy in size, and in large areas, at nine sites of the brachial biceps (BB) and the lateral vastus (LV) muscles obtained at autopsy from five elderly subjects. It was concluded that in the BB the site of a biopsy should be well defined, since the incidence of fiber types varied systematically. In the LV the biopsy should be large to permit a reliable estimate of the incidence of fiber types; with the needle technique, repeated sampling may be necessary. Small samples are not suited for the analysis of fiber type grouping.