Representativeness of a muscle biopsy specimen for the whole muscle

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Abstract
To investigate whether the muscle fiber area and the proportion of fiber types in a biopsy specimen are representative of the muscle, 7 specimens from the anterior tibial muscle in humans were compared with 7 necropsy specimens including the whole cross-sectioned anterior tibial muscle. The fiber areas of the transverse section differed greatly between biopsy and necropsy specimens and between different regions of the necropsy specimens, probably owing to different degrees of muscle fiber contraction. Relative measures, the coefficient of variance for the mean fiber area and the differences in size beween type I and type II fibers, proved to be reliable. The proportion of fiber types varied greatly between adjacent fascicles and in different regions of the necropsy specimens. The mean proportion of type II fibers can vary from 7-30% in 2 biopsies from the same muscle. Great caution is recommended when the proportion of fiber types in a biopsy specimen is assumed to be valid for the proportion of fiber types in the whole muscle: specimens must be taken from several sites.