Abstract

This study was designed for the evaluation of the mean proportions and range of individual difference of muscle fiber types in human Gastrocneminus, Soleus, Peroneus longus and Tibialis anterior muscles, respectively. Flash-frozen muscle sections obtained from 15 cadavers were stained for H&E, trichrome, PAS, regular & reversed myosin ATPase, succinic dehydrogenase (SDH), acid phosphatase (Ac-Pase) and alkaline phosphatase (Alk-Pase). The results obtained were as follows. 1) Differentiation of muscle fiber types was not evident in H&E and trichrome stained specimen. Three types of muscle fibers were, however, evident in PAS-stained sections according to the degree of positivity in observed skeletal muscles. 2) Two fiber types (Types I and II) were only differentiated and the predominant muscle fiber type was type I by regular myosin ATPase reaction in Gastrocnemius, Soleus, Peroneus longus and Tibialis anterior muscles. 3) Three muscle fiber types (Type I, IIa and IIb) were, however, differentiated and the predominant muscle fiber type was type IIa, contrary to patterns of regular myosin ATPase in skeletal muscles except for Soleus muscle by reversed myosin ATPase stains. Only two muscle fiber types (Type I and II) and predominant type I fibers were shown in Soleus muscle. 4) SDH stains showed three types of muscle fiber except Soleus muscle. The mean proportions(%) of type 1 fibers were 48.0% in Gastrocnemius, 62.3% in Soleus, 40.8% in Peroneus longus, and 39.8% in Tibialis anterior muscles, respectively. 5) The mean proportions (%) of muscle fiber types in human skeletal muscles were markedly different, according to individuals and various enzyme histochemical stains. 6) The size of muscle fibers was relatevely small in type I fibers compared with type IIb. 7) Evaluation for the combination patterns of various enzyme histochemical activities showed that the common muscle fiber types (Type I, IIa and IIb) were markedly reduced in the mean proportions and unusual rare muscle fibers predominant. This predominance of unusual muscle fiber types and marked discrepancy in muscle fiber types between regular and reversed myosin ATPase seemed to be ascribed to decreased muscle enzyme activities following postmortem period.