Comparison of the Histochemical and Contractile Properties of Human Gastrocnemius Muscle

Abstract

Contractile and histochemical properties of the human gastrocnemius muscle were compared in 21 male athletes ranging from 20 to 29 years of age. Surface electrical stimulation was used to determine muscle twitch parameters. The contractile variables of the muscle twitch were: latency (L), time to peak force (TPF1 and TPF2), peak force (Pf1 and Pf2), half-contraction time (1/2 CT), and half-relaxation time (1/2 RT). Muscle samples from the belly of the medial gastrocnemius muscle were obtained using the needle biopsy technique. The samples were treated histochemically for myosin ATPase in order to classify the fibers as slow twitch (ST) or fast twitch (FT) and to determine fiber areas. Multiple correlations were performed between the contractile and histochemical variables. The results demonstrated significant (p < 0.05) positive relationships between the calculated twitch recordings and percentage of FT fibers (R = 0.85), percentage of ST fibers (R = 0.85), relative percent area of FT fibers (R = 0.84), and relative percent area of ST fibers (R = 0.84). The results suggest that fiber type percentage and relative percent area determined using myosin ATPase are related to electrically stimulated isometric contractile properties. J Orthop Sports Phys Ther 1991;13(6):322-328.