Everyone knows testosterone and growth hormone play significant roles in building muscle and strength. Perhaps those who know this best are athletes, especially bodybuilders. In men, testosterone plays a key role in the development of male reproductive tissues, such as the testis and prostate, as well as promoting secondary sexual characteristics like increased muscle, bone mass, and the growth of body hair.1 Growth hormone (GH) is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. Human growth hormone is primarily used by people for its anabolic, or muscle-building, properties.2
Bodybuilders and athletes who want to increase these two hormones are often led to believe their gym routine will trigger an increase in both, thus resulting in improved muscle mass. However, new research from scientists at McMaster University reveals that exercise-induced testosterone and growth hormone does not play a role in building muscle after lifting weight, and those who are looking to alter these hormones through various exercise routines are doing so in vain.3
Two separate studies, published in the Journal of Applied Physiology and the European Journal of Applied Physiology, were performed to determine if the anabolic hormones testosterone and growth hormone influenced muscle protein synthesis. Protein synthesis is the process that ultimately results in increased muscle mass. The first study consisted of both male and female participants, and each participated in an intense leg exercise. Even though there was a 45-fold difference in testosterone increase, men and women produced new muscle protein at exactly the same rate.4
The second study analyzed the post-exercise hormonal responses of 56 young men, aged 18 to 30. These men trained five days a week, for twelve weeks. Some men gained no muscle mass, while some gained a significant amount. Their levels of testosterone and growth hormone after exercise, however, showed no relationship to muscle growth or strength gain. Contrarily to what was hypothesized, researchers found that cortisol was related to the gain in muscle mass. This was surprising as cortisol is thought to have the opposite effect of anabolic hormones, reducing protein synthesis and breaking down tissue.5
“While testosterone is definitely anabolic and promotes muscle growth in men and women at high doses, such as those used during steroid abuse, our findings show that naturally occurring levels of testosterone do not influence the rate of muscle protein synthesis,” said Daniel West, lead author of both studies and a graduate student in the Department of Kinesiology at McMaster.6
The results of these studies are interesting considering the popular belief that exercises such as the squat and deadlift trigger anabolic hormone spikes, resulting in increased muscle mass. “The idea that you can or should base entire exercise training programs on trying to manipulate testosterone or growth hormone levels is false,” says Stuart Phillips, a professor in the Department of Kinesiology. “There is simply no evidence to support this concept.”7
