HIIT produces increases in muscle power and free testosterone in male masters athletes
Question
Does replacing normal training with six weeks of low-volume, low-frequency HIIT improve peak power output and alter steroid hormones in male masters athletes?
Summary
Seventeen male masters athletes replaced their usual high-volume aerobic training with supervised low-frequency cycling HIIT for six weeks. Peak power output increased, free testosterone rose slightly, total testosterone did not significantly change, and cortisol increased with a lower testosterone:cortisol ratio, suggesting benefit but also meaningful training stress.
Methodology
- 17 male masters athletes from endurance and team sports.
- 17 participants.
- Cycle ergometer.
- Work intervals: 30 s.
- Recovery: 3 min active recovery.
- Intensity: 40% PPO; mean 126 +/- 22% of power at VO2peak.
- About 18 min interval/recovery time; warm-up not reported.
- Once every 5 days.
- 6 weeks.
- Single-arm prospective cohort with a habitual-training observation phase followed by HIIT
- Peak power, and Steroid hormones were tracked.
Outcomes
PPO
Absolute and relative peak power output increased after HIIT.
Absolute PPO 799 +/- 205 to 865 +/- 211 W, p<0.001, d=0.32; relative PPO 10.2 +/- 2.0 to 11.0 +/- 2.2 W/kg, p<0.001, d=0.38.
Free testosterone
Calculated free testosterone increased slightly after HIIT.
7.0 +/- 1.2 to 7.5 +/- 1.1 ng/dL, p=0.050, d=0.40.
Total testosterone
Total testosterone did not significantly change after HIIT.
15.2 +/- 4.2 to 16.4 +/- 3.3 nmol/L, p=0.061.
Stress hormones
Cortisol increased and testosterone:cortisol ratio decreased after HIIT.
Cortisol p=0.01, d=0.90; T:C p=0.017, d=0.69.
Insights
- For older trained athletes, HIIT every five days can be enough to improve cycling peak power while sharply reducing training volume.
- Recovery spacing matters: the authors selected five-day spacing based on prior recovery data in older males.
Limitations
- Single-arm design
- No randomized control or moderate-intensity comparison
- Male masters athletes only
- Calculated free testosterone
- Lab power outcome rather than competition outcome
Safety
- No adverse events or injuries were reported.
- Participants had general practitioner approval to exercise and HIIT was spaced every five days.