Effects of strength, endurance and combined training on myosin heavy chain content and fibre-type distribution in humans

Abstract

This study investigated the effect of strength training, endurance training, and combined strength plus endurance training on fibre-type transitions, fibre cross-sectional area (CSA) and MHC isoform content of the vastus lateralis muscle. Forty volunteers (24 males and 16 females) were randomly assigned to one of four groups: control (C), endurance training (E), strength training (S), or concurrent strength and endurance training (SE). The S and E groups each trained three times a week for 12 weeks; the SE group performed the same S and E training on alternate days. The development of knee extensor muscle strength was S>SE>E ( P<0.05) and has been reported elsewhere. The reduction in knee extensor strength development in SE as compared to S corresponded to a 6% increase in MHCIIa content ( P<0.05) in SE at the expense of the faster MHCIId(x) isoform ( P<0.05), as determined by electrophoretic analyses; reductions in MHCIId/x content after S or E training were attenuated by comparison. Both S and SE induced three- to fourfold reductions ( P<0.05) in the proportion of type IIA/IID(X) hybrid fibres. S also induced fourfold increases in the proportion of type I/IIA hybrid fibres within both genders, and in a population of fibres expressing a type I/IID(X) hybrid phenotype within the male subjects. Type I/IIA hybrid fibres were not detected after SE. Both S and SE training paradigms induced similar increases (16-19%, P<0.05) in the CSA of type IIA fibres. In contrast, the increase in CSA of type I fibres was 2.9-fold greater ( P<0.05) in S as compared to SE after 12 weeks. We conclude that the interference of knee extensor strength development in SE versus S was related to greater fast-to-slow fibre-type transitions and attenuated hypertrophy of type I fibres. Data are given as mean (SEM) unless otherwise stated.

Muscle mechanical properties of strength and endurance athletes and changes after one week of intensive training

“…However, a comparison between completely different training contents seems to be difficult to realize, since it is impossible and impracticable to match strength and endurance workloads when including a variety of specific training methods. Nevertheless, comparisons between the effects of strength and endurance training loads on contractile properties have been done by a variety of authors (Costill et al, 1976;Putman et al, 2004).…”

Effect of heavy strength training on thigh muscle cross-sectional area, performance determinants, and performance in well-trained cyclists

“…However, concurrent strength and endurance training has been shown to impair the development of power production compared with strength training alone Kraemer et al 1995). It has also been shown that training strength and endurance concurrently interferes with the development of muscle hypertrophy (Kraemer et al 1995;Putman et al 2004). Bastiaans et al (2001) found that replacing a portion of the endurance training with lightly loaded explosive strength training improved short-term peak power output more than endurance training alone.…”

Adaptações neuromusculares ao treinamento de força e concorrente em homens idosos.

“…Ainda, um maior sincronismo de fibras musculares, embora não seja sugerido como fator importante para a melhora da força máxima, resulta em um menor tempo de obtenção da força máxima, sendo, portanto, um mecanismo responsável pelo aumento na taxa de produção de força [9][10][11] . Já as adaptações morfológicas ao TF incluem o aumento da área de secção transversa fisiológica (AST) da fibra muscular 17,24 , o que resulta no aumento na AST do músculo 13 , bem como no aumento na espessura muscular 6 e uma modificação entre as isoformas de cadeia pesada de miosina, o que ocorre a partir de uma conversão de fibras do subtipo IIX para o subtipo IIa 17,24 . Modificações na AST da fibra são comumente avaliadas a partir de técnicas histoquímicas realizadas após biópsia muscular 17 , enquanto modificações na AST total do músculo e na espessura muscular são avaliadas a partir de técnicas de imagem como ressonância magnética 23 , tomografia computadorizada 9 ou ultrasonografia 6,13 .…”