Bodybuilders try to manipulate their testosterone and growth hormone levels through exercise routines, as these anabolic hormones are known to promote muscle growth. But according to two separate studies, these anabolic hormones do not influence muscle protein synthesis, the process that leads to increased muscle mass.
“A popular mindset for weightlifters is that increased levels of hormones after exercise play a key role in building muscle,” explains Daniel West, lead author of both studies and a graduate student in the Department of Kinesiology at McMaster University, Canada. “That is simply not the case.”
In the first study, researchers measured exercise-induced testosterone, claimed to contribute to increases in muscle protein synthesis, in both male and female participants after intense leg exercise. Their findings showed that although the men had a 45-fold increase in testosterone compared to the women, all participants were able to make new muscle protein at exactly the same rate.
“Since new muscle proteins eventually add up to muscle growth, this is an important finding,” says West. “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.”
In the second study, researchers examined exercise-induced hormonal responses in 56 young men, following intense leg exercise at the midpoint of a 12-week exercise training study. The men experienced an increase in muscle mass, ranging from almost nothing to more than 5.4 kilogram. However, their measured 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,” says Stuart Phillips, a professor in the Department of Kinesiology. “There is simply no evidence to support this concept.”
West, D., & Phillips, S. (2011). Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training European Journal of Applied Physiology, 112 (7), 2693-2702 DOI: 10.1007/s00421-011-2246-z
West, D., Burd, N., Churchward-Venne, T., Camera, D., Mitchell, C., Baker, S., Hawley, J., Coffey, V., & Phillips, S. (2012). Sex-based comparisons of myofibrillar protein synthesis after resistance exercise in the fed state Journal of Applied Physiology, 112 (11), 1805-1813 DOI: 10.1152/japplphysiol.00170.2012