Effects of lifelong exercise and age on transcriptome dynamics in MHC I and MHC IIa muscle fibers at baseline and in response to resistance exercise

RNA-Seq was used for the first time to investigate the effects of resistance exercise on transcriptome dynamics in slow myosin heavy chain (MHC) I and fast MHC IIa muscle fibers among 3 groups of men. Vastus lateralis muscle biopsies were obtained before and 4 hours after resistance exercise. A total of 25 males were included in this investigation. The participants included 8 lifelong exercisers (74±1y), 9 old healthy non-exercisers (75±1y), and 8 young exercisers (25±1y). Vastus lateralis biopsies were obtained in conjunction with a resistance exercise bout (bilateral knee extensions with 3x10 reps at 70% of 1-RM) and included a basal biopsy and another biopsy 4 hours after the exercise session. From each biopsy sample, individual muscle fibers were isolated. After myosin isoform identification of isolated fibers via SDS-PAGE, RNA extraction of MHC I and MHC IIa muscle fibers was performed. Thus, each resulting sample contained total RNA from either MHC I or MHC IIa muscle fibers. A total of 100 samples were analyzed using RNA-Seq. The study design allowed us to examine the acute effects of resistance exercise on transcriptome dynamics in MHC I and MHC IIa muscle fibers with age and exercise.