Variability of histochemical and morphometric data from needle biopsy specimens of human quadriceps femoris muscle

Duplicate needle biopsies from the lateral portion of quadriceps femoris muscle from 20 young, healthy males were investigated morphometrically and histochemically. Mean results showed both the size and occurrence of the three main fibre types present to be similiar to values obtained from a survey of the literature. However, considerable variations in the proportions of fibre types (coefficients of variation 30-40%) and significant (P <0.001) differences in fibre size between individuals were common. Within individuals, comparisons of samples taken at a reference site in the right thigh with samples obtained from deeper, more proximal or contralateral sites also often showed significant differences in fibre size. These results suggest caution is necessary when interpreting apparent changes in such values derived from subsequent biopsies of individuals.