Have you heard anyone talk about the anabolic response to weight training? The theory is that intense resistance training leads to spikes in anabolic hormones like growth hormone, testosterone, and IGF-1 that boost muscle growth. On the other hand, some studies suggest the release of these hormones in response to training may NOT contribute as much as you think to muscle growth or gains in strength. Not that these hormones aren’t important for muscle growth. The question is whether getting a short-term bump up in these hormones after a workout makes a difference in how much muscle development you get. Is the post-workout anabolic response overrated?
Hormones Involved in Muscle Hypertrophy
You’re probably familiar with the “big three” hormones involved in muscle hypertrophy: growth hormone, IGF-1, and testosterone. In women, testosterone is less important than in men since women produce less testosterone. In women, most of it comes from two glands that lie just above the kidneys – the adrenal glands whereas testosterone in men is produced by the testicles. In fact, men produce about 20 times more testosterone relative to women. Still, women can develop stronger, firmer muscles despite not having testosterone levels equivalent to a man’s. What role does testosterone play in hypertrophy? It boosts muscle growth primarily by increasing muscle protein synthesis.
Growth hormone, produced by the pituitary gland in the brain, is another hormone associated with muscle growth. Growth hormone exerts its effects on muscle primarily through another protein produced by the liver called IGF-1. It’s not clear how much of DIRECT effect growth hormone has on muscle growth. It seems to exert most of its impact on muscle through IGF-1 under the direction of growth hormone.
How Important is Growth Hormone for Muscle Growth?
What’s interesting is some research shows boosting growth hormone stimulates muscle growth mainly in adults who are growth hormone deficient, not healthy adults who already produce enough growth hormone. If you still want to maximize growth hormone release, make sure you’re getting enough shut-eye. Your pituitary gland ramps up production of growth hormone during the deeper stages of sleep, which is why sleep is important for health. Although evidence for a direct effect of growth hormone on muscle growth isn’t that strong, growth hormone can still help you develop a leaner physique. For one, it enhances oxidation of stored fat which can help you get leaner.
So what about the post-workout anabolic response – the bump-up in growth hormone you get in response to training? According to one study, a single session of resistance training does little to enhance biologically active growth hormone in women, contrary to what fitness magazines say. However, consistent weight training over a longer period of time does lead to higher baseline levels of growth hormone. Not only does research suggest that women don’t get a big rise in growth hormone after a single session of resistance training, even if you lift hard, but growth hormone also may not directly impact muscle growth as much as you might think unless you’re growth hormone deficient.
What happens when you give growth hormone supplements? In one study, researchers gave 303 young, healthy males and females (mostly male) athletes growth hormone injections for a total of 20 days. The participants DID experience an increase in lean body mass, although some of the increase was due to fluid retention, BUT the athletes experienced no improvements in muscle strength or athletic performance as a result of receiving supplemental growth hormone.
In yet another study published in the Journal of Applied Physiology, healthy participants did heavy resistance training using large muscle groups, the classical way to boost anabolic response. Some studies also show shortening the rest period between sets maximizes growth hormone release. The group did show an increase in anabolic hormones like growth hormone and testosterone after working out, yet the transient post-workout rise in anabolic hormones didn’t lead to a greater increase in muscle strength or size. This was confirmed by muscle imaging studies.
The Bottom Line
Testosterone and growth hormone, through its effect on IGF-1, are anabolic hormones. Testosterone enhances muscle protein synthesis, making it an anabolic hormone. The effect of growth hormone on muscle growth is a little murkier. It’s difficult to gauge how much direct effect growth hormone has on muscle growth in healthy people. If you were to take high levels of these hormones, you might experience an increase in muscle size and strength although you’d also have to deal with unwanted side effects.
There’s no doubt that heavy resistance training increases anabolic hormone levels transiently. The big question is whether the brief bump-up in anabolic hormones you get from a workout has a significant impact on muscle growth. Regardless, this shouldn’t discourage you from lifting heavy and doing compound exercises. We know this type of training DOES lead to muscle growth and an increase in strength but the small increase in anabolic hormones you get may not be a strong contributing factor.
More important is the breakdown of muscle fibers you get when you lift heavy and the time your muscles spend under tension. You can further increase time under tension by slowing down the speed of each rep. This will also help you limit momentum. Emphasizing the eccentric portion of the movement also leads to more muscle damage, which can translate into greater growth and strength gains. Training hard can lead to big improvements in body composition but it may not be because of the increase in anabolic hormones you get right after a workout.
Am J Physiol Endocrinol Metab. 2006 Dec;291(6):E1177-87.
Breaking Muscle. “Exercise-Induced Testosterone and GH Does Not Build Muscle”
Br J Pharmacol. 2008 Jun; 154(3): 557-568.
Harvard Health Publications. “Growth hormone, athletic performance, and aging”
Journal of Applied Physiology Published 1 January 2010 Vol. 108 no. 1, 60-67 DOI: 10.1152/japplphysiol.01147.2009.
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