... Whenever?
Here's a question many people have, if jerking off will raise testosterone levels:
23Q. I want to start working out to build muscle mass.
Some of my friends say masturbation will increase testosterone, but others say it will decrease testosterone. What effect will masturbation have?
Masturbation is very unlikely to decrease testosterone levels. Semen is not the source of testosterone, and ejaculation will not cause testosterone levels to go down.
All other things being equal, increased sexual activity -- including masturbation -- tends to increase testosterone levels. But these levels depend upon many factors including age, time of day, overall level of physical activity, and general health. Psychological factors can cause changes in testosterone levels: levels go up in men who believe they are going to become more sexually active, levels can be affected by whether a person knows in advance that he will be test for testosterone, and so forth.
In your case, the increase in physical activity accompanying your workouts will probably have a much greater effect on your testosterone levels. If you are a young male AND working out, your testosterone level is likely to be so high that any difference masturbation (or other sexual activity) might make will be insignificant.
In much older men (over 40 years old), especially those with fewer sexual activities of other kinds, masturbation might increase testosterone levels significantly--which is not to suggest that masturbation might replace a reasonable program of physical exercise.
Although athletes were once advised to avoid sexual activities (including masturbation) *immediately* before athletic performances, studies have not found any scientific basis for this advice. So far as I know there have been no studies of the effects of abstinence *throughout* training, and probably there won't be because it would be difficult to find athletes who would agree to be abstinent for a prolonged time and no way to tell whether they really were. At any rate, nothing special about masturbation would cause it to have a bigger effect for better or worse than any other kind of sexual activity.
