Skeletal muscle mitochondrial marker responses to a single bout and 6 weeks of high load versus high volume resistance training in previously trained men.

The effects of high-load (HL) versus high-volume (HV) resistance training (RT) on various molecular outcomes are similar. However, mitochondrial responses remain understudied. Therefore, the purpose of this study was to interrogate mitochondrial mRNA and protein responses to acute and chronic HL versus HV RT. Vastus lateralis biopsies from resistance trained males in two prior studies were assessed. In Study 1, 11 college-aged men completed an acute bout of either HL or HV RT exercises to failure. Biopsies were collected at PRE, 3-h post-, and 6-h post-exercise. In Study 2, 15 college-aged men participated in 6 weeks of supervised unilateral RT where each leg was assigned to either HL or HV RT. Biopsies were collected from both legs prior to and 72 h following last training bout of the intervention. Biopsies from both studies were used to assess mitochondrial mRNAs, and Study 2 biopsies were assayed for mitochondrial proteins and citrate synthase (CS) activity. Results from both studies revealed several significant main effects of time but no significant interactions. Additionally, CS activity, a surrogate of mitochondrial content, decreased following chronic RT (P = 0.016) but no interaction was observed between the HV and the HL leg over time (P = 0.882). In conclusion, while RT resulted in both acute mitochondrial mRNA and chronic CS activity and mitochondrial protein responses, there were no differences in the HL versus HV paradigms on these outcomes.