Single muscle fiber gene expression with resistance training in young women

Abstract

The purpose of this investigation was to examine fiber type specific gene expression (GE) before and after 12 weeks (36 sessions) of progressive resistance training (PRT) for the knee extensors. Muscle biopsies were taken from vastus lateralis of 8 young women (23 ± 2 y, 67 ± 5 kg) before and 4 h post the 1st(acute) and 36th (chronic) training session. Myogenic (MyoD, myogenin, MRF4) and proteolytic (atrogin‐1, MuRF‐1, myostatin) GE was measured in mRNA from pooled myosin heavy chain (MHC) I and IIa fibers, using real‐time RT PCR. After the 1st training session, myogenin and MRF4 GE induction (p<0.05) was targeted to the MHC I fibers, while myostatin GE decreased (p<0.05) and MuRF‐1 GE increased (p<0.05) in both fiber types. After 12 weeks of training the basal level GE of myogenin (MHC I) and MRF4 (MHC I and IIa) increased (p<0.05). In response to the 36th training bout, myogenin GE induction (p<0.05) and myostatin GE reduction (p<0.05) was targeted to the MHC IIa fibers. There was a trend (p=0.07) for MuRF‐1 to increase in both fiber types after the 36th session. In summary, these data suggest that 12 weeks of PRT alters basal level myogenic GE. Interestingly, the MHC IIa specific response for myogenin and myostatin in the chronic phase may be important for the fast‐twitch fiber adaptation that occurs with resistance training in young individuals. Supported by NIH grant AG18409.