Quantitative analysis of quadriceps muscle biopsy. Results in 30 healthy females.

Open biopsy was performed in right quadriceps muscle (vastus lateralis) in 30 healthy female volunteers between 20 and 50 years of age. Histometric analysis was carried out on ATPase stained sections preincubated at pH 4.5. Type 1, 2a, 2b, and 2 fibres were quantified taking into account the following parameters: percentage of fibre types, mean diameter, atrophy and hypertrophy factor, variability coefficient of mean diameter and mean diameter ratio of type 1: type 2 fibres. Results showed that there is a large variation in fibre type percentage, mean diameter and hypertrophy factor, and consequently ranges of normal values are wider than those previously reported. Atrophy factor and variability coefficient are the least variable parameters. The importance of normal controls is stressed to avoid false positives in histometric evaluation of muscle biopsy with minimal changes.