Bodybuilding.net - Bodybuilding Forum

After about an hour of weight training there is a natural spike in your cortisol and testosterone levels. The hormones are normally produced when your body is stressed (fight or flight). As you adjust to the resistance regime and to prevent too much of these hormones being present, your body stops producing them. Too much of something is not good for you right?
The outcome is that there can be a rapid drop in testosterone perhaps to below pre-training levels. It may take day or two before it returns back to your pre-training level. If you try to have sex during this period when your testosterone level is low you may find you have no libido or sex drive.
If you are overtraining you may make the situation worse by creating large peaks in testosterone which will be followed by large drops. It could mean extended periods where your body is not producing more testosterone because of the very high levels made during training,
Bodybuilders do say that they feel their sex drive improves when they take a couple of weeks off. This shows that your body can recover if given the chance. As you get bigger your resting testosterone level should increase provided you’re not over training.
If you have a low testosterone level and are concerned that bodybuilding may have caused or influenced changes in your testosterone, consult a health-care professional.