Overall Effect
Several studies suggest that moderate-intensity cardio can slightly increase testosterone in the short term, especially in untrained men. However, chronic high-volume endurance training is associated with reduced total and free testosterone levels.

• A 2018 study found that endurance-trained men had significantly lower testosterone compared to sedentary controls
• In contrast, moderate aerobic exercise over 12 weeks increased testosterone levels in obese men
• Eight endurance-trained males (19-49 years) completed a resting control session and three treadmill runs of 40, 80, and 120 min at 55% of VO2max. The ratios of anabolic hormones (testosterone and DHEAS) to cortisol were greater during the resting session and the 40-min run compared to the longer runs. At a low intensity, longer duration runs are necessary to stimulate increased levels of testosterone, DHEAS and cortisol and beyond 80 min of running there is a shift to a more catabolic hormonal environment.

Factors That Maximize the Effect

• Low to moderate cardio (50–70% VO2max)
• Medium Duration (<45 minutes)
• Consistency (2–3x per week)

• Obese or sedentary men often experience testosterone increases with regular cardio — primarily due to improved insulin sensitivity, reduced inflammation, and body fat loss

• Older men may be more hormonally responsive to moderate aerobic activity compared to younger, already-active individuals

Conclusion
Cardio’s impact on testosterone depends on how you do it. Moderate, well-programmed cardio can support testosterone production, particularly in those with excess body fat or sedentary lifestyles. But excessive endurance training without recovery may blunt testosterone and increase cortisol. For optimal hormonal health, cardio should complement (not replace) resistance training and be adjusted based on goals, intensity, and recovery.