The Role Of Hormones In Running

All training affects your hormone, or endocrine, system.

It’s important, says Anthony Hackney, a professor of exercise physiology at University of North Carolina-Chapel Hill and the co-author of Sports Endocrinology, to understand the balance of hormones. The key hormones for an athlete to know about are growth hormone (or human growth hormone, HGH), insulin and insulin-like growth factors, cortisol, and testosterone.

Growth hormone triggers the adaptive response in your muscles, says Tom Cotner, Ph.D., the running coach for Seattle-based Club Northwest. Growth hormone is an anabolic hormone that promotes growth. It targets the muscles and cells that are being stressed by exercise and makes them receptive to adaptation. The muscles actually adapt during recovery.

We naturally secrete growth hormone during the delta wave part of sleep, but as we get older we have less and less time in that deep sleep. During exercise, we also secrete growth hormones but in smaller quantities. It doesn’t kick in, either, until after about 10 minutes of exercise, Cotner says, and there are diminishing returns after 75 minutes.

Because growth hormone is secreted from the pituitary gland in response to energy expenditure it’s possible to “game the system,” Cotner says, by training more than once a day, doing more intense exercise, or taking an ice bath after exercise, which expends energy.

But, as the weeks of exercise accumulate, the amount of growth hormone secreted for anyone workout decreases and your body adapts. If you really wanted to “see the hormones go crazy,” Hackney says, you’d get the most response from being very out of shape and then starting to work out.

The most commonly overlooked hormones involved in exercise are the insulin-like growth factors and insulin. Insulin-like growth factors are stimulated by growth hormones and bind to cells to regulate cell growth and processes. Insulin oversees the cells’ uptake of glucose and storage of glycogen, necessary to ensure we have the right energy pathways available for our training.

In the regular course of things—if you’re eating well, sleeping, and exercising—these hormones work to self-regulate and maintain a balance.

“Some are going up, some are going down,” Hackney says.

We can throw that balance out of whack, though, from overtraining. “You can overload your endocrine system,” Cotner says.

Cortisol is released from the adrenal gland and is an anti-inflammatory and a catabolic hormone that breaks down cells. In an average person, cortisol breaks down about 1 percent of muscle proteins daily, which are then replaced as induced by growth hormone and insulin-like growth factor. With training, cortisol breaks down 3-5 percent of muscle proteins in the body every day, Cotner says. Too much training releases too much cortisol and essentially breaks down too many proteins.

Too much training can also decrease the levels of testosterone in the body. Testosterone, found in both men and women, increases muscle mass and decreases recovery time. But while intense workouts can increase testosterone levels, too much long, easy training can drive them down.

Overtraining is the most likely thing to throw off an athlete’s hormone balance, which leads to all the symptoms associated with over-training: sleeplessness, extreme muscle soreness, elevated resting heart rate, or overall fatigue. Generally, if you experience those symptoms, you should dial it back. But knowing exactly how much training is too much can be challenging.

“If I knew exactly how much was too much, I’d be a lot richer,” Hackney says.

Other things that can impact the hormone balance include life stress, which causes a release of cortisol, epinephrine and norephedrine. A lack of sleep can stall your secretion of growth hormone, as can alcohol, Cotner says. One beer, he says, can decrease the amount of growth hormone secreted by 25 percent. Age also decreases the amount of growth hormone and slows down the entire system. That’s why older athletes often experience the two-day lag effect of soreness from a workout—which can also happen to young female athletes, who have less growth hormone and testosterone.

Not eating enough calories, a particular problem for female athletes, can cause a disruption in the whole system. The right mix of protein (6 grams) to carbohydrates (30 grams) in the recovery window after a workout helps delay cortisol secretion and getting enough iron is essential to red blood cell production, regulated by naturally-occurring EPO. Any sickness or trauma will also force your body to prioritize hormone regulation to those things first.

Trying to bump up levels of some hormones is common in a variety of forms. People sleep in altitude tents to increase levels of EPO naturally by decreasing oxygen supply. Over-the-counter supplements promise to increase testosterone or HGH levels. But “a lot of those things don’t work,” Hackney says.

Even the things that do work in the short-term—resistance exercises have been shown to elevate short-term levels of growth hormone, testosterone and insulin-like growth factors—aren’t proven to make you faster in the long run, Hackney says.

Illegal doping agents definitely increase hormone levels and can sometimes increase performance, both Hackney and Cotner say. But, there are legal consequences, severe health consequences, and sometimes even death from messing with your hormone balance artificially. The complicated system is good at self-regulating and it’s hard to know what all the side effects of changing one thing will be.