Muscle strength and qualitative myosin heavy chain isoform mRNA expression in the elderly after moderate- and high-intensity weight training

This study was an attempt to determine the effects of 12 weeks of moderate-intensity (MIEX) and high-intensity (HIEX) weight training on the muscular strength and qualitative myosin heavy chain (MHC) isoform mRNA expression in 18 elderly men. Subjects were randomly assigned to either a control group (Con) or training groups of either MIEX or HIEX. Training sessions occurred 3 days/week and involved three sets of 15-20 repetitions at 60%-65% 1-RM for MIEX and three sets of 8-10 repetitions at 75%-80% 1-RM for HIEX. Both upper and lower body strength increased for Con and increased significantly for MIEX and HIEX. No changes in MHC mRNA isoform expression were observed for Con; however, there were increases in Type I MHC and decreases in Type IIx MHC mRNA expression for MIEX and increases in Type I, IIa, and Ex MHC mRNA expression for HIEX. The findings suggest that both moderate- and high-intensity weight training increases muscle strength and the expression of Type I MHC mRNA isoform, while high-intensity weight training also increases the mRNA expression of Type IIa and IIx isoforms in previously inactive elderly men.