A recent study in the European Journal of Applied Physiology found that intense endurance exercise can cause low testosterone and lowered sex hormone levels in men, which translates into poor reproductive health and low fertility.
Previous studies found comparable fertility issues in women whose fitness routines are endurance focused, most commonly manifested in impaired menstrual cycles.
The good news is, this can be fixed - by getting off the street, spin class, or treadmill, and into the weight room.
Strength training can help reduce these symptoms by improving hormone levels to help counter the stress from cortisol and related catabolic hormones that cause inflammation and damage to the reproductive organs.
Research suggests there is a middle ground to reproductive health such that individuals who like to run and cycle can improve their fertility and overall health by incorporating strength training.