You may have heard that exercise increases testosterone levels. And that more testosterone means more muscle growth. But how much truth is there in these claims?
WHAT IS TESTOSTERONE?
Testosterone is the most important androgen (male sex hormone). Testosterone concentrations in blood are low before puberty and rise to adult values during puberty.
Testosterone is produced in the adrenal glands and (in men) in the testes, approximately 7 mg/day in men. Testosterone concentrations are much lower in women. In this article we focus on the situation with men, in particular natural bodybuilders.
Testosterone fulfills vital functions with regard to, among other things, body composition, heart, bones, sexual organs, skin and kidneys.
DOES EXERCISE INCREASE TESTOSTERONE?
Several studies have examined how exercise affects testosterone levels in men. Here’s what they found.
The biggest increases in testosterone occur during compound exercises with free weights, such as the barbell squat, for several reasons. First of all, you use more ‘stabilizing’ muscles all over your body than with machine exercises. In addition, free weight exercises generally activate the muscles to a greater extent than machine exercises.
Other factors also play a role in the degree of testosterone increase during strength training: how hard you train, how many sets you do, how long you rest, how much training experience you have, how high your fat percentage is and how old you are.
HIGH INTENSITY INTERVAL TRAINING (HIIT)
HIIT stands for high-intensity interval training and is a very intensive form of interval training. With HIIT, short, very intensive efforts are alternated with equally short or often even shorter breaks. This allows you to train very intensively for a longer period of time and keep your heart rate high.
A 2021 meta-analysis from the Sport and Health University Research Institute (10 studies) found that HIIT temporarily increases testosterone after training. Still, levels typically return to baseline levels within 30 minutes.
The study also found that HIIT increases production of the ‘stress hormone’ cortisol, potentially negating the benefits associated with a rise in testosterone levels.
Some research suggests that endurance training has a positive impact on testosterone levels, provided you train at a high intensity and for long enough. Lower intensity endurance training is not challenging enough to increase testosterone.
DO TESTOSTERONE PEAKS AFTER EXERCISE INCREASE MUSCLE GROWTH?
Testosterone and muscle growth are inextricably linked, which is why bodybuilders quickly prick up their ears as soon as the T-word is mentioned. More testosterone means more muscle mass, right? Unfortunately, the truth is more complicated.
We have found that strength training increases testosterone levels. However, we also saw that most research shows that these increases are temporary: testosterone rises sharply after a workout and returns to baseline shortly afterwards. In addition, most research shows that training does not increase testosterone production in the long term.
The amount of muscle mass you build mainly depends on the degree of overload during training, and after training through nutrition and rest. The temporary increase in testosterone levels, during and immediately after training, is in fact only a by-product. A necessary by-product, by the way, because the testosterone increase probably compensates for the increase in another hormone value as a result of strength training, namely that of (catabolic) cortisol.
INCREASE YOUR TESTOSTERONE
There are other things you can do to maintain or even increase your testosterone level, but as long as you stay within the natural range, their influence on muscle growth is minimal. So you can only build ‘extra’ muscle mass if you exceed that margin and you need anabolic steroids for that.
Strength sports and intensive cardio are associated with an increase in testosterone levels. However, this is only a temporary increase and is necessary to compensate for the increase in catabolic cortisol. The short testosterone peak therefore does not result in additional muscle growth.