Endurance Exercise Duration and Hormonal Response
One concern that many people have when trying to build muscle mass is that performing any type of endurance related cardio activity is going to hinder the results they see.
It is well known that overdoing it on the cardio front will be problematic for building muscle since endurance cardio tends to break muscle tissue down, which is the exact opposite of what you’re trying to accomplish.
But, many of those who are into muscle building take this notion just a little too far and start avoiding all cardio altogether for fears it will prevent any growth at all.
To assess the situation further, we can look at a study published out of the European Journal of Physiology.
In this study, researchers wanted to evaluate the effect of endurance exercise duration on hormone concentrations in male subjects, while controlling the intensity of the exercise.
They had eight endurance trained males complete three treadmill runs of 40, 80 or 120 minutes in duration, running at 55% of their VO2max. Blood samples of the men were taken before the session, and then one, two, three, and four hours after the start of the run, and then analyzed for luteinizing hormone, DHEAS, cortisol, and free and total testosterone levels.
The results after the study was completed indicated that LH was much higher before the sessions had been completed and the total testosterone levels increased during the first hour then showed a steady decline during the next three hours into recovery.
DHEAS increased in a relation to the length of the run, and cortisol was only seen to increase during the 120 minute run, while it showed a continual decline across time in all the other sessions.
Furthermore, the positive ratio of anabolic to catabolic hormones were seen at rest and during the 40 minute run, switching over to favor the more catabolic environment as the run progressed to the lengthier time periods.
Therefore, the practical information we can gain from this study is that if you’re doing endurance training that goes longer than forty minutes, you will be putting your body at a higher chance for muscle breakdown due to favoring of catabolic hormones, but you should be able to train up to that 40 minute point without too much worry.
This is of course assuming a proper nutrition program is being followed from the start and that you are not overtraining with a combination of weight lifting and aerobic work.
Reference:
Copeland, JL. Et al. 2005. Influence of exercise duration on post-exercise steroid hormone responses in trained males. European Journal of Physiology. 94(5-6):505-13.
