Myosin heavy-chain mRNA expression after a single session of heavy-resistance exercise

This study determined the effects of a single session of heavy-resistance exercise on myosin heavy-chain (MHC) mRNA expression, along with the expression of the transcription factors Myo-D, myogenin, and Id-1.

Four male subjects participated in a control group (CON) and seven in a resistance-exercise group (REX). REX performed one resistance-exercise session employing three sets of 8-10 repetitions at 75-80% one-repetition maximum on the squat, leg press, and leg extension. Vastus lateralis biopsies were obtained pre, post, and at 6 h postexercise.

In regard to CON, no significant differences were located for any criterion variable (P > 0.05). For REX, elevations of 38.19%, 45.61%, and 74.24% (P < 0.05), respectively, occurred at 6 h-post for Type I, IIa, and IIx MHC mRNA. Myo-D and myogenin mRNA were elevated 27.28% and 23.58% postexercise (P < 0.05), respectively, but no change was observed in Id-1 mRNA. Elevations at 6 h-post of 46.85% and 46.41% (P < 0.05), respectively, occurred for Myo-D and myogenin mRNA with no change in Id-1. Myo-D and myogenin protein increased 57.91% and 52.30%, respectively, postexercise and 317.56% and 254.08 at 6 h-post (P < 0.05), whereas no change was noted for Id-1. Myofibrillar protein was elevated 84.52% at 6 h-post (P < 0.05). Type I and IIa MHC mRNA at 6 h-post were correlated with myogenin mRNA and protein postexercise and 6 h-post, whereas Type IIx at 6 h-post was correlated with Myo-D mRNA and protein postexercise and 6 h-post (P < 0.05).

These results indicate that the mRNA expression of all three MHC isoforms is up-regulated after a single session of heavy-resistance exercise and that Myo-D and myogenin seem to play a role in MHC isoform gene expression.