Silvia Azaña, an embryologist at inviTRA, talks in this video about whether intense exercise negatively affects male fertility:
Moderate exercise is healthy and improves seminal parameters compared to men who don't include exercise in their daily activities.
But virtue lies in the middle ground, and excessive physical activity typical of professional athletes, competitors, triathletes, and marathon runners does seem to affect seminal quality.
This decrease in seminal quality seems to be related to a reduction in testosterone levels and an increase in oxidative stress. Reactive oxygen species would increase too much with intense physical exercise. So, they would exceed the body's, uh, antioxidant capacity to neutralize them. This imbalance causes oxidative stress and, therefore, can lead to poorer seminal quality and greater sperm DNA fragmentation.
Therefore, prolonged, very intense, or too frequent exercise could affect a man's semen quality.
