Time course analysis reveals gene-specific transcript and protein kinetics of adaptation to short-term aerobic exercise training in human skeletal muscle.
Level 4 - case-series / case-control
Prospective single-arm pre-post intervention study without a concurrent control group
PubMed 24069271 · doi:10.1371/journal.pone.0074098
What was done
Eight healthy, sedentary males completed 14 consecutive days of cycling for 60 minutes per day at 80% of peak oxygen consumption (VO2peak). Skeletal muscle biopsies were taken at baseline and 16 hours after exercise sessions 1, 3, 7, 10, and 14 to assess the time course of mRNA expression, protein content, and mitochondrial markers.
What was found
VO2peak increased by 17.5 ± 3.8% over the 14 days. Markers of mitochondrial adaptation (cytochrome c, COXIV expression, and citrate synthase activity) increased within the first week of training, whereas the mtDNA/nDNA ratio remained unchanged after two weeks. PGC-1α and ERRα protein accumulated during training, and a subset of genes showed transient mRNA increases after the first session before returning to baseline. Specific numeric values for transcript and protein changes were not reported in the abstract.
Why it matters
The study outlines the short-term kinetics of human skeletal muscle plasticity, showing that mitochondrial protein accumulation and enzymatic changes occur within days of initiating high-intensity aerobic exercise, prior to detectable changes in mitochondrial DNA content.
Limits
The sample size was very small (n = 8) and restricted exclusively to healthy, sedentary males. There was no non-exercising control group to account for potential confounding from repeated muscle biopsies, and the intervention was limited to a two-week timeframe.
Cited by
- supports Mitochondrial content in skeletal muscle can increase measurably within a few days or weeks of starting exercise training.