Skeletal muscle mitochondria in the elderly: effects of physical fitness and exercise training.
Level 3 - non-randomized controlled study
Combination of cross-sectional/case-control comparisons and a non-randomized single-arm prospective exercise intervention
PubMed 24438376 · doi:10.1210/jc.2013-3983
What was done
Researchers investigated whether skeletal muscle mitochondrial decline is caused by aging per se or inactivity across three designs in older adults (60–80 years): 1. A cross-sectional study (n = 80) assessing the relationship between peak oxygen uptake (graded exercise test) and mitochondrial volume density (MitoVd, vastus lateralis electron microscopy). 2. A case-control study comparing chronically endurance-trained older adults with age- and sex-matched sedentary controls. 3. A prospective 4-month exercise intervention in sedentary older adults. Outcomes included MitoVd, electron transport chain protein complexes (Western blot), biogenesis mRNAs (quantitative RT-PCR), and in vivo oxidative capacity (ATPmax via 31P-MRS).
What was found
Peak oxygen uptake strongly correlated with MitoVd in 80 older adults. Endurance-trained older adults had higher MitoVd, ATPmax, and specific electron transport chain protein complex levels than sedentary peers. The 4-month exercise intervention restored MitoVd, ATPmax, and biogenesis transcription factors in sedentary subjects. No exact numeric values, effect sizes, or p-values were provided in the abstract.
Why it matters
These findings suggest that age-associated skeletal muscle mitochondrial loss and dysfunction are primarily driven by physical inactivity rather than aging itself, and that late-life aerobic exercise can reverse these deficits.
Limits
The abstract omits sample sizes for the case-control and intervention sub-studies, reports no numerical values or statistical precision estimates, and uses an uncontrolled pre-post design for the exercise intervention rather than a randomized trial.
Cited by
- supports Physical exercise increases the number, size, and health of mitochondria in the body.