Raging Hormones

New studies suggest everything we know about muscle growth could be wrong. But are they right?

Fitness news can be confusing. New studies seem to come out every day  — often contradicting previous research and information accepted for years as common knowledge.

Case in point: The headline in the June 14 online edition of Science Daily, picked up by other digital and print media, which read “Bodybuilding Myth Debunked: Growth-Promoting Hormones Don't Stimulate Strength.”  The article refers to recent published scientific journal studies by a team from Canada’s McMaster University which found that spurts of human growth hormone (HGH) and testosterone, which we have long known are stimulated naturally in the body by doing sprints and hard, fast weightlifting, supposedly don’t build much, if any, muscle.

According to graduate student Daniel West, the studies’ lead author, you can’t produce enough of the hormones naturally to make a real difference; only bigger amounts, like that supplied by the injection of artificial testosterone and HGH, will have an effect. The conclusion, then, was that “basing entire exercise training programs on trying to manipulate testosterone or growth hormone levels is false,” said study member Stuart Phillips, a McMaster kinesiology professor. “There is simply no evidence to support this concept."

Those are fighting words to most scientists. The claim that what we’ve all thought is gospel for nearly 20 years — that high-intensity training elicit a hormone response that makes you stronger— is bunk, is being met with skepticism from experts who have been studying and promoting the virtues of ”exercised-induced” HGH and testosterone for many years.

“Testosterone and growth hormone don’t build muscle? Come on — does this pass the common-sense litmus test?” says William Kraemer, Ph.D, of the University of Connecticut, widely regarded since the early 1990s as the dean of researchers studying exercise-induced hormone production. He called West’s conclusions a “simple sound bite” that “doesn’t appreciate the complexity of the human machine.“  Moreover, the studies don't specify the intensity levels of the exercisers in the study. It’s been proven that the higher the intensity of exercise, the greater the hormone release.

You have to look at the processes in the human body as a symphony, not just one or two instruments. Many studies — and magazine readers — don’t want or have time for that kind of complexity. – William Kraemer, Ph.D


Dr. Paul Spector, MD, ASCM, a New York-based physician and Equinox Tier 4 Coach, looked over the studies and agreed with Kraemer. “There are hundreds of hormonal pathways in the body, and to try to draw conclusions so quickly is …well, I don’t think this reputable. It’s shit science.”

The two studies, whose findings were published in the Journal of Applied Physiology and the European Journal of Applied Physiology, don't question that hard exercise increases testosterone and HGH production or that these hormones promote muscle protein synthesis — the process that leads to bigger muscles — at high doses. In fact, both studies showed that hormone levels did spike during and after exercise, and that muscles did get bigger — but not big enough to show that there was a relationship, according to lead author West.

The first study compared the testosterone levels and muscle-growth increases of 8 men and 8 women after they did a single bout of high-intensity leg strength exercise. The exercise raised men’s testosterone levels 45 times as much as it raised the women’s, but when muscle biopsies were taken, the two groups were found to have achieved virtually identical muscle growth. 

To researcher West, the results indicated that, “naturally occurring levels of testosterone do not influence the rate of muscle protein synthesis (growth).” To Spector, that indicated a meaningless, poorly designed study. “16 people? Single bout of exercise?” he said. “You can’t even begin to draw conclusions yet. Exercise takes time to show benefits.”

As Kraemer put it: “The problem is that muscle growth is slow, but [hormonal] signaling is fast. These hormones also naturally go up and down. It’s the repetitive exposure that gives you the composite change. So the fact that you don’t see a correlation right away is meaningless.”

The second study analyzed the hormonal responses of 56 men, aged 18 to 30, who trained five days a week for 12 weeks. Despite various gains in muscle mass ranging from near-zero to 12+ pounds, West’s team saw no correlation between their post-exercise testosterone and HGH and their muscle growth or strength gain. Their conclusion:  Don't structure your workout program toward trying to manipulate testosterone or growth hormone levels.

Of course, Dr. Kraemer is having none of that, questioning everything from the study’s design to what exactly it was measuring. “There are 100 variants of HGH in the pituitary gland — a ‘super-family’— so you can’t look at just one,” he says. “You can’t make conclusions when you only have part of the picture. You have to look at the processes in the human body as a symphony, not just one or two instruments. Many studies — and magazine readers — don’t want or have time for that kind of complexity.”

Paul Spector, openly skeptical of a publish-now, analyze-later culture, worries that the publicity of studies like West’s will have the effect of persuading people that they don’t need to work out hard once in a while. “There’s an unbelievable momentum of an idea based on a crummy study,” he says. “You need to apply some common sense.”

Ultimately, the whole brouhaha may be much ado about nothing. Even if the McMaster studies prove to be the valid, we know for a fact that hard training builds muscle and makes you stronger and faster. So, does it matter what hormones, if any, are helping make that happen?