Correlation between contractile strength and myosin heavy chain isoform composition in human skeletal muscle

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Abstract
Correlation between contractile strength and myosin heavy chain isoform composition in human skeletal muscle. Med. Sci. Sports Exerc., Vol. 30, No. 8, pp. 1217-1222, 1998. The purpose of this study was to investigate the relationship between myosin heavy chain (MHC) composition and maximal contraction strength of the human quadriceps femoris muscle. Muscle biopsies were obtained from m. vastus lateralis in young highly physical active males(N = 7). The MHC composition of muscle homogenates was determined by electrophoresis techniques (SDS-PAGE). Isokinetic peak torque and constant-angle torque (50° knee flexion) were obtained during slow (30°·s−1), medium (120°·s−1), and fast (240°·s−1) maximal concentric and eccentric quadriceps contractions and expressed relative to muscle volume. The percentage of MHC II in the quadriceps muscle was positively correlated (rs = 0.61-0.93; P< 0.05-0.01) to maximal concentric quadriceps strength obtained at medium to high knee angular velocity. In contrast, no consistent pattern of correlation was observed for maximal eccentric quadriceps strength. The relationship observed between muscular MHC composition and maximal contractile strength is suggested to appear as a consequence of MHC-related differences in contractile force-velocity characteristics and/or contractile Rate of Force Development (RFD).