
The muscles actually adapt during recovery.

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

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. All training affects your hormone, or endocrine, system.
