Mitochondrial adaptations to high intensity interval training in older females and males.
Level 3 - non-randomized controlled study
Prospective pre-post interventional study without a non-exercise control group
PubMed 31145037 · doi:10.1080/17461391.2019.1615556
What was done
Twenty-two older sedentary adults (11 males, 11 females) completed 6 weeks of supervised high-intensity interval training (HIIT) 3 days per week. The protocol consisted of 5 x 1 min cycling intervals (at 124 ± 3% max power output for sessions 2–6 and 135 ± 3% for sessions 7–20) interspersed with 1.5 min recovery. Muscle biopsies were obtained at baseline and 72 hours after the final session to measure mitochondrial respiratory capacity, citrate synthase (CS) activity, and mitochondrial proteins (MnSOD, complex I–V). Body composition and VO2 max were also assessed.
What was found
VO2 max increased and body fat percentage decreased after HIIT in both sexes (p < 0.05). Citrate synthase activity and protein content of MnSOD and complexes I–V increased in both sexes. Coupled and uncoupled mitochondrial respiratory capacity increased only in males. Mitochondrial respiratory capacity normalised to CS activity did not change in either sex. Exact baseline and post-intervention numerical values were not reported in the abstract.
Why it matters
This study shows that short-term low-volume HIIT can stimulate muscle mitochondrial biogenesis and improve cardiorespiratory fitness in older adults, though sex differences may influence changes in functional respiratory capacity.
Limits
The study had a small sample size (n = 22 total, 11 per sex) and lacked a non-exercise or moderate-intensity control group. The 6-week duration leaves long-term clinical and functional outcomes unexamined, and exact quantitative data with variance measures were omitted from the abstract.
Cited by
- supports Mitochondrial content in skeletal muscle can increase measurably within a few days or weeks of starting exercise training.