Whole-muscle and single-fibre contractile properties and myosin heavy chain isoforms in humans

Abstract

The contractile characteristics of three human muscle groups (triceps surae, quadriceps femoris and triceps brachii) of seven young male subjects were examined. The contractile properties were determined from electrically evoked isometric responses and compared with fibre type composition determined from needle biopsy samples. Fibre types were identified using myosin heavy chain (MHC) isoforms as molecular markers with gel electrophoresis (SDS-PAGE) and histochemical ATPase staining. Four contractile parameters (twitch time to peak torque, the maximal rate of torque development, frequency response and fatiguability) were found to be related to fibre type composition. From the biopsy samples, single muscle fibres were isolated and chemically skinned. Isometric tension (Po) unloaded shortening velocity (Vo) and rate of tension rise (dP/dt) were determined. Each fibre was classified on the basis of its MHC isoform composition determined by SDS-PAGE. Fibres belonging to the same type showed identical contractile parameters regardless of the muscle of origin, except minor differences in Po of the fast fibres and dP/dt of slow fibres. The results are in favour of the conclusion that fibre type composition, determined using MHC isoforms as markers, is the major determinant of the diversity of contractile properties among human muscle groups.

Sexual dimorphism of murine masticatory muscle function

“…However, the contractile properties were faster in males than females, particularly in rise and relaxation with tetanic stimulation. This is most likely caused by the increased proportion of MHC 2b fibers in the male ADM muscles, which is the fiber type that produces the fastest shortening velocity (16)(17)(18). This observation is consistent with previous characterizations of fiber type distributions in murine masticatory muscles (5,19), where male muscles are comprised of a greater proportion of MHC 2b fibers both in number and proportional area.…”

Critical determinants of combined sprint and endurance performance: an integrative analysis from muscle fiber to the human body

“…Certainly, increases in muscle mass will improve peak power production by the muscle, irrespective of its fiber-type distribution. The proportion of fast-type fibers is also critical to peak power production because it determines maximal muscle-fiber contraction velocity (27,58,59). Optimal pedaling velocity during sprint cycling has been shown to relate to the proportion of fast-type fibers in musculus vastus lateralis (30) and their proportion of the cross-sectional area (31).…”

Are cultured human myotubes far from home?

“…The muscle fibers that express MyHC-β are characterized as slow, fatigue resistant and oxidative (type 1 muscle fibers), whereas the fibers that express MyHC-2A are fast oxidative (type 2A muscle fibers), and the MyHC-2X fibers are fast glycolytic (type 2X muscle fibers). Most human muscles consist of all three muscle fiber types in varying degrees, depending on the functional demands of the muscle (Harridge, et al, 1996), age and gender (Schiaffino and Reggiani, 2011). Studies performed in rodents have demonstrated that MyHC isoforms expressed in differentiated myotubes were identical to the MyHC expression pattern in the muscle fibers from which the satellite cells were isolated (Dusterhoft andPette, 1993, Rosenblatt, et al, 1996).…”