Based on all the research on the topic of testosterone responses to exercise, it appears that intense, short duration exercise is best for increasing circulating levels of this anabolic hormone. However, the opposite also appears to be true. Excessive amounts of endurance training are shown to reduce circulating testosterone levels in men.
Scientists from the University of North Carolina have revealed that some endurance athletes possess lower testosterone levels than sedentary men. It seems that the high metabolic load of endurance training suppresses hormone secretion in some parts of the brain (hypothalamus and pituitary gland) – the areas that control testosterone production.
I don’t think that a few hours of recreational cycling once a week will reduce your anabolic hormone output. Conversely, anabolic hormone suppression does appear to increase with training load in endurance athletes. Therefore, endurance athletes need to structure their training to prevent this undesirable effect.
