HIIT Produces Increases in Muscle Power and Free Testosterone in Male Masters Athletes

This study tested whether a six-week high-intensity interval training program could improve peak power output and testosterone levels in male athletes aged 60 and older. Seventeen men (average age 60) completed nine HIIT sessions over six weeks — each session consisting of six 30-second sprints on a cycle ergometer with three minutes of active recovery between each effort.

The results were significant. Peak power output increased by approximately 8%, and relative peak power adjusted for body weight showed similar gains. Free testosterone — the biologically active form that declines steadily with age — increased measurably across the group. Total testosterone trended upward but did not reach statistical significance, suggesting that the free testosterone increase was the primary hormonal adaptation.

For men over 50, this is one of the most directly relevant studies available. The participants were not young athletes — they were masters-level endurance athletes already in their 60s. The protocol was brief (nine sessions total), the individual sessions were short, and the results were measurable in both power output and hormonal markers. It demonstrates that low-volume, high-intensity sprint work can produce meaningful physiological changes in older men — including the hormonal adaptations that matter most for muscle maintenance, energy, and quality of life as we age.