New research has debunked the long-held bodybuilding myth that growth-promoting hormones build strength and stimulate muscle growth.
Two studies, by scientists at McMaster University, found that exercise-related testosterone and growth hormone supplements do not play an influential role in building muscle after weightlifting, despite the persistent belief that they do. What’s more, bodybuilders who try to manipulate those hormones through exercise routines are wasting their time.
The studies, published in the Journal of Applied Physiology and the European Journal of Applied Physiology, found anabolic hormones — long thought to be essential for building a muscular frame — do not influence muscle protein synthesis, the process that leads to bigger muscles.
"A popular mindset for weightlifters is that increased levels of hormones after exercise play a key role in building muscle," said Daniel West, lead author of both studies and a graduate student in the Department of Kinesiology at McMaster. "That is simply not the case."
In the first study, researchers examined the effects of increased testosterone on male and female participants performing intense leg exercise. Despite a 45-fold difference in testosterone increase, men and women were able to make new muscle protein at exactly the same rate.
In the second study, researchers analyzed the post-exercise hormones in 56 young men, who trained five days a week for 12 weeks in total. The men experienced gains in muscle mass that ranged from virtually nothing to more than 12 pounds, yet their levels of testosterone and growth hormone after exercise showed no relationship to muscle growth or strength gain.
"The idea that you can or should base entire exercise training programs on trying to manipulate testosterone or growth hormone levels is false," said Stuart Phillips, a professor in the Department of Kinesiology. "There is simply no evidence to support this concept."