초록 close

The purpose of this study was to examine the effect of 4 week resistance training on myosin heavy chain (MHC; I, I/IIa, IIa, IIa/IIx, IIx, I/IIa/IIx) isoforms in single muscle fiber in young men (age 21.20±2.25, n=10). Subjects were subjected to 4 weeks of isokinetic training and each training session consisted of 10 × 10 maximal 90°/s and 180°/s extension and flexion contractions using a Kin-Com isokinetic dynamometer. To maintain the effective control of the differences of training impact on individuals, the present study adopted the one-leg exercise training or within subject model. Muscle biopsies were obtained from right/left vastus lateralis before and after training. We analyzed MHC isoforms in single muscle fiber by electrophoretic analysis (100 fibers analyzed to each biopsy sample; 4,000 fibers analyzed in total). Mean MHC IIa isoforms in the trained leg were significantly increased by 10% (p<.05), whereas the number of MHC IIx isoforms was decreased by 8% (p<.01). MHC IIa was significantly increrased by 5% (p<.05) in untrained leg. MHC IIx and MHC I/IIa/IIx were decreased by 7% (p<.05) and 1% (p<.05) respectively in untrained leg. However, MHC IIa expression in trained leg was increased by 5%(p<.05) than untrained leg. From the result of this study we confirmed 4 week of training result in significant changes in MHC isoforms in within subject resistance exercise model.