The best training routine, diet and supplement program will not compensate for insufficient rest, and sleep is the best, and only (in some instances), way of getting this rest. Professor Michael Colgan went as far as to say: even if your training and nutrition program can straight for the mouth of God almighty, without adequate rest your body will fail to adapt. During sleep, growth hormone is produced and protein synthesis (provided protein is consumed prior to sleep) occurs. These are only two beneficial aspects of sleep. Energy consumption reduction and brain cell restoration are two other aspects equally important for bodybuilders. research has shown, sleep is important for many reasons. For bodybuilders, sleep is particularly important as it restores brain function and alertness in preparation for intense training sessions. Sleep also enhances muscular recovery through protein synthesis and human growth hormone release. Getting eight to ten hours of quality sleep every night will promote these factors as well as general well being. Recovery will take a backward step if one does not prioritize sleep, so get to sleep if you want to grow. Full article : http://www.bodybuilding.com/fun/drobson5.htm