Strength training causes a series of physical changes to the body—some obvious and some more obscure. It’s easy to notice external changes like increases in muscle tone and mass. The less obvious ones occur under the surface, in the form of hormonal changes. We recently explored the neural adaptations to resistance training—that is, how the mind communicates with the muscles to produce movement patterns. This time we’ll dive into the hormonal response to exercise, focusing on resistance training in particular. Let’s run through what hormones are and how their presence affects your performance.
Hormones play a significant role in muscle hypertrophy and strength development.
Hormones are chemical messengers that travel through the body and regulate complex actions such as growth, metabolism and fertility, as well as the body’s reaction to physical stress1. In response to signals from the brain, hormones are released directly into the bloodstream from glands that store and produce them. While hormones circulate freely in the blood, they can only dock at their “target” cells, which have a way of identifying them using a sort of antenna on their surface. Once a hormone reaches its target, it causes a biological change by altering protein synthesis.
Bottom Line: hormones travel all throughout the body, carrying messages that help distant parts communicate and create changes orchestrated by the brain.
Hormone production during exercise can vary; factors such as overtraining, nutrition, and sleep can affect your body’s ability to release a normal dose. Anabolic hormones produced in your body like testosterone and growth hormone contribute to protein synthesis in the muscle2. Anabolic effects like accelerated growth of muscle, bone, and red blood cells, and increased neural conduction, help athletes build strength and develop athleticism.
A Battle of Balance: Anabolic vs. Catabolic
Different hormones can have opposing effects in the body. This creates a need for balance, such that one does not overpower the other.
Growth hormone and testosterone are anabolic hormones, meaning they promote muscle building. They also promote life extension, well-being, immunity, and energy and fat-burning. Growth hormone is released during the early stages of deep sleep, and both growth hormone and testosterone respond positively to exercise, working together to build strength in the muscles you train.
At the other end of the hormone spectrum is cortisol. Cortisol is a catabolic hormone, meaning it promotes muscle degradation. Cortisol is released in response to stress, both real and imaginary. The brain perceives moderate exercise as a form of physical stress to the body, releasing cortisol to help the body prepare for a “fight or flight” scenario. As a result, cortisol stimulates protein breakdown in the muscle to release fuel into the bloodstream for quick usage. It also suppresses immune function and bone formation. Other stressors such as lack of sleep, poor diet, and mental stress increase your cortisol release. The catabolic effects of cortisol create a net negative for your training purposes.
Growth hormone and testosterone directly compete with cortisol during resistance training. In a healthy strength program, training improves anabolic hormone release while teaching the body to release less cortisol with each workout. If athletes over-train, via higher volume, intensity or otherwise, their cortisol release skyrockets. The stress of overtraining tips the balance in favor of cortisol and muscle breakdown, and it becomes impossible to build strength in these conditions.
Takeaway: Hormones carry out complex functions in the body. Resistance training can maximize positive hormone effects if it’s conducted in a smart manner, but overtraining will cause serious muscle deterioration and performance inhibition. Use your knowledge of hormones to calibrate your resistance training for peak performance!
2. Robergs, R. A. and Roberts, S. O. (1997). Exercise physiology: Exercise, performance, and clinical applications. Mosby, St. Louis.
3. Episode 3: Strength training- Myths, misconceptions, and application for distance runners https://itunes.apple.com/us/podcast/magness-marcus-on-coaching/id961516002