Different effects on human skeletal myosin heavy chain isoform expression: strength vs. combination training

Abstract

Myosin heavy chain (MHC) isoform expression changes with physical training. This may be one of the mechanisms for muscular adaptation to exercise. We aimed to investigate the effects of different strength-training protocols on MHC isoform expression, bearing in mind that α- MHCslow(newly identified MHC isoform) mRNA may be upregulated in response to training. Twelve volunteers performed a 6-wk strength training with maximum contractions (Max group), and another 12 of similar age performed combination training of maximum contractions and ballistic and stretch-shortening movements (Combi group). Muscle samples were taken from triceps brachii before and after training. MHC isoform composition was determined by SDS-PAGE silver staining, and mRNA levels of MHC isoforms were determined by RT-PCR. In Max group, there was an increase in MHC2A (49.4 to 66.7%, P< 0.01) and a decrease in MHC2X (33.4 to 19.5%, P < 0.01) after training, although there was no significant change in MHCslow. In Combi group, there was also an increase in MHC2A (47.7 to 62.7%, P < 0.05) and a decrease in MHCslow (18.2 to 9.2%, P < 0.05) but no significant change in MHC2X. An upregulation of α-MHCslow mRNA was, therefore, found in both groups as a result of training. The strength training with maximum contractions led to a shift in MHC isoform composition from 2X to 2A, whereas the combined strength training produced an MHC isoform composition shift from slow to 2A.

Development of a Diagnostic Method for Detecting Increased Muscle Protein Degradation in Patients with Catabolic Conditions

“…Strength training reportedly leads to muscle hypertrophy, whereas endurance training without causing hypertrophy induces protein remodeling, altering the proportions of type I and type II myosin heavy chains and increasing the levels of enzymes, including those that are involved with oxidative phosphorylation (29 -32). Finally, the combination of strength and endurance training could activate different intracellular signaling processes or stimulate specific cell types (e.g., mature muscle cells versus satellite cells), resulting in different responses in terms of protein expression and exercise capacity (25,26,33,34). Regardless, our results indicate that endurance training can benefit hemodialysis patients who exhibit increased muscle proteolysis.…”

Neuromuscular mechanics and hopping training in elderly

“…No changes were observed in muscle architecture with training, which may suggest that muscle hypertrophy was not an explanation for this increased stiffness. However, higher fascicle stiffness could be achieved with shifted myosin-heavy-chain (MHC) isoform composition of muscle fibers from slow (I) to fast (IIa), as shown by Liu et al (2003) with combined strength plus ballistic stretch-shortening type-of training. Unfortunately, passive twitch was not measured or muscle biopsies taken in the present study in order to confirm the speculation.…”

Efeitos do treinamento neuromuscular na aptidão cardiorrespiratória e composição corporal de atletas de voleibol do sexo feminino

“…Primeiro, por reduzir o percentual da força máxima durante a corrida, melhorando a perfusão de sangue oxigenado para os músculos ativos (16) . Segundo, por induzir transição das fibras musculares IIB para IIA, que possuem maior potencial oxidativo que as fibras IIB (14) . As atletas de voleibol apresentaram importante melhora da aptidão cardiorrespiratória em resposta ao treinamento realizado, evidenciado pelo aumento do consumo máximo de oxigênio e do limiar anaeróbio; mas essa melhora não pode ser atribuída apenas ao treinamento com pesos, pois estudos realizados com mulheres submetidas a treinamento de força encontraram pouca ou nenhuma melhora na capacidade aeróbia (15,16,17) , de modo que os benefícios aqui demonstrados devem ter ocorrido devido à associação dos treinamentos com pesos, saltos, técnico e tático.…”

“…A combinação do treinamento de força de alta intensidade com força explosiva, pela técnica de pliometria, demonstrou ser um méto-do eficiente para melhoria da altura alcançada nos salto vertical (11,12) . Porém, a realização do treinamento de força máxima e potência concomitantemente ao treinamento aeróbio é um possível exemplo de interação negativa entre tarefas do treinamento, principalmente do ponto de vista do desenvolvimento da força muscular, pois proporciona adaptações distintas em diversos sistemas orgânicos, como, por exemplo, nas proteínas musculares contrácteis, na densidade mitocondrial, na densidade capilar e nas enzimas oxidativas (13,14) . Estudos que investigaram os efeitos do treinamento com pesos em mulheres encontraram pouca (15,16) ou nenhuma (17) melhora na aptidão cardiorrespiratória.…”