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 (MHO 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, Ila, and IIx 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 Ila and IIx isoforms in previously inactive elderly men.
Darryn S. Wiiloughby is with the Muscle Physiology Laboratory, Department of Sports Medicine. College of Nursing, University of Southern Maine, 37 College Ave., Gorham. ME 04038. Stephen C. Pelsue is with the Molecular Genetics Research Laboratory, Department of Applied Medical Sciences, University of Southern Maine.