Acute and chronic effects of resistance training on skeletal muscle markers of mitochondrial remodeling in older adults.

We investigated the acute and chronic effects of resistance training (RT) on skeletal muscle markers of mitochondrial content and remodeling in older, untrained adults. Sixteen participants (n = 6 males, n = 10 females; age = 59 ± 4 years) completed 10 weeks of full-body RT (2 day/week). Muscle biopsies from the vastus lateralis were obtained prior to RT (Pre), 24 hr following the first training session (Acute), and 72 hr following the last training session (Chronic). Protein levels of mitochondrial electron transport chain complexes I-V (+39 to +180%, p ≤ .020) and markers of mitochondrial fusion Mfn1 (+90%, p = .003), Mfn2 (+110%, p < .001), and Opa1 (+261%, p = .004) increased following chronic RT. Drp1 protein levels also increased (+134%, p = .038), while Fis1 protein levels did not significantly change (-5%, p = .584) following chronic RT. Interestingly, protein markers of mitochondrial biogenesis (i.e., PGC-1α, TFAM, and NRF1) or mitophagy (i.e., Pink1 and Parkin) were not significantly altered (p > .050) after 10 weeks of RT. In summary, chronic RT promoted increases in content of electron transport chain proteins (i.e., increased protein levels of all five OXPHOS complexes) and increase in the levels of proteins related to mitochondrial dynamics (i.e., increase in fusion protein markers) in skeletal muscle of older adults. These results suggest that chronic RT could be a useful strategy to increase mitochondrial protein content in older individuals.