Effects of Voluntary Wheel Running Training on Myosin Heavy Chain Isoform Composition in Rat Plantaris Muscle

The effects of voluntary running training were investigated in the 13-week-old female Fischer344-rats (N=12). Animals were divided into two groups : sedentary (S ; N=6) or voluntary running training (VT ; N=6) group at 5-week of age. Animals in group VT were given free access to the running wheel for 8 weeks. Body weight of two groups was significantly increased during training period. The average running revolution of group VT was 10483±1041 (mean±SD) per day (Min. ; 1 506±287， Max. ; 17601±1539). Heart weight and relative heart weight of group VT were significantly higher than group S. The plantaris (PLA) weight and the relative PLA weight of group VT were significantly higher than group S. No change of protein concentration was observed in two groups. In protein content， the value of group VT was significantly higher than that of group S. In the myosin heavy chain (MyHC) isoform composition of the PLA muscle， no change of type I MyHC isoform was observed with training， while， type II d MyHC isoform of group VT was significantly higher than that of group S. Moreover， type II a MyHC isoform of group VT was significantly higher than that of group S. Relatively， type II b MyHC isoform of group VT was significantly lower than that of group S. These results indicate that voluntary running training causes the great changes of myosin heavy chain composition and hypertrophy in the rat plantaris muscle