It’s not only that getting enough sleep helps muscles grow. Without adequate sleep muscle mass decreases. Human growth hormone (HGH), is one of the primary compounds that allows muscles to recover and grow. Among other functions, our bodies need it to actually use the amino acids present in the protein we eat. As it happens, the time when the bloodstream is flooded with the stuff is - you guessed it - during sleep. Without a good quantity and quality of sleep, the body simply cannot do these things well.