This is true, regardless of whether or not you are exercising, and happens largely because of an increased release of growth hormone during short periods of fasting. (chestsculpting.com)
The average recommended sleep of 7 to 9 hours of deep uninterrupted sleep has proven itself to be excellent in the natural release of growth hormone. (fitnessandpower.com)
Even if you don't care about leg development, lower body training will help upper body development through a greater release of growth hormone. (onnit.com)