Effects of high intensity resistance and low intensity endurance training on myosin heavy chain isoform expression in highly trained rowers.Int J Sports Med. 2003 May; 24(4):264-70.IJ
An important mechanism of muscle adaptation to exercise is the alteration of myosin heavy chain (MHC) isoform expression. This study investigated the effect of a high intensity resistance training (HIRT) and a low intensity endurance rowing (LIER) on MHC isoform expression in highly trained human muscle. Six well-trained male rowers underwent a training program consisting of a 3-week HIRT and a 3-week LIER, each followed by one-week of recovery. Muscle samples were taken from vastus lateralis before and at the end of each training and recovery phase. MHC isoform was analyzed by SDS-PAGE using silver stain and MHC isoform mRNA by RT-PCR. The maximum oxygen uptake and power output did not change after the training. MHC isoform composition did not change over HIRT or LIER, and there was a decrease in MHC I with concomitant increase in MHC IIa after recovery following HIRT. HIRT led to mRNA upregulation of MHC Ialpha, Ibeta and IIx (127 %, 148 % and 117 %, respectively, p < 0.05), but not MHC I protein (60 % vs 62 %, NS), and LIER led merely to MHC Ibeta mRNA upregulation (131 %, p < 0.05). Thus, different responses of MHC isoform expression to HIRT and LIER occurred in the highly trained muscle, and a "ceiling effect" in terms of MHC I expression could be observed. The upregulation of MHC Ialpha mRNA in human skeletal muscle documented in this study may encourage further observations in this field.