Long distance running lowers testosterone; sprint training increases it

From This study, Effect of altered reproductive function and lowered testosterone levels on bone density in male endurance athletes: "Relatively short duration exercise bouts at maximum or near maximum intensity appear to increase serum testosterone levels, with measurable changes evident within minutes. However, with prolonged acute submaximal exercise bouts of approximately two hours or longer, suppression of circulating testosterone is noted which may remain for several days. "

You will likely lower your testosterone level if you run great distances, and you can raise your testosterone by doing all-out sprints. Sprints might not be an option for those with old injuries. I am eight months out from a torn Achilles tendon. My tendon is not quite right and never will be. I also run a 15 % probability of re-injuring it. I have no problem going all out on a recumbent bike and can elevate my pulse to my maximum after just a few sprints.

Sprints are very demanding but they are of short duration. A similar result can be obtained by doing high intensity strength training which is also demanding but short in duration. We can show you how to do both at New Orleans Fitness Trainers and at Austin Personal Training.