PMID 34063524

Research
All papers

The Effect of High-Intensity Interval Training Periods on Morning Serum Testosterone and Cortisol Levels and Physical Fitness in Men Aged 35-40 Years

Ambroży T, Rydzik Ł, Obmiński Z, Błach W, Serafin N, Błach B, Jaszczur-Nowicki J, Ozimek M

Question

How does an eight-week high-intensity interval endurance-and-strength program affect morning testosterone, cortisol, T/C ratio, VO2max, and physical fitness in men aged 35-40?

Summary

In healthy recreationally trained men aged 35-40, an eight-week supervised high-intensity endurance-and-strength circuit program increased morning testosterone and testosterone-to-cortisol ratio and improved several strength/endurance fitness tests. VO2max did not significantly improve.

Methodology

  • Healthy men aged 35-40 with at least 2 years of recreational training experience.
  • 30 participants.
  • Mixed bodyweight, dumbbell, and kettlebell circuit exercises.
  • Work intervals: 60 seconds high-intensity activity in 2:1 interval portion.
  • Recovery: 30 seconds rest in 2:1 interval portion.
  • Intensity: High-intensity circuit training; exact HR/RPE target not reported.
  • 60 minutes.
  • 3 sessions per week.
  • 8 weeks.
  • Randomized controlled intervention
  • Testosterone, Cortisol, T/C ratio, and VO2max were tracked.

Outcomes

Testosterone

Morning testosterone increased significantly in the experimental group.

Experimental group +36.7%; control +6% not significant.

Improved

Cortisol

Mean cortisol did not significantly change within groups.

Experimental group had about a 12% decrease, but within-group change was not significant.

No clear change

T/C ratio

The testosterone-to-cortisol ratio increased significantly in the experimental group.

Experimental group +59%; control +16% not significant.

Improved

VO2max

VO2max did not significantly improve despite a small numerical increase in the experimental group.

Experimental group about +11.8%, not statistically significant.

No clear change

Fitness tests

Several muscular endurance and power tests improved in the experimental group.

Significant improvements were reported for abdominal/upper-body endurance, pull-up, and standing long jump tests.

Improved

Insights

  • A supervised 60-minute mixed interval and strength-circuit program may improve hormonal and muscular fitness markers in recreationally trained midlife men.
  • This was not a pure cardiorespiratory HIIT protocol; it resembled combined resistance and interval circuit training.
  • VO2max did not significantly improve, so aerobic-fitness claims should be cautious.

Limitations

  • Small sample of men aged 35-40.
  • Only testosterone and cortisol were evaluated among hormonal/biochemical mechanisms.
  • No follow-up to determine persistence after return to prior activity.
  • The intervention combined endurance, interval, and strength training, making the active ingredient unclear.
  • Exercise intensity was not reported with precise HR or RPE targets.

Safety

  • Participants provided a medical certificate indicating no contraindication to high-intensity training.
  • No adverse events or dropouts were reported in the the paper.