Sleep is necessary for muscle growth and muscle repair. Working out hard and not getting ample sleep can cause your muscles to tear down and result in injury and other complications.  Regular sleep gives your body time to repair the microscopic tears you make in your muscles when you do a workout and rest your central nervous system overnight. Restoring your muscles gives them time to gain energy and strength for the next day.  Your body produces a muscle-building hormone called growth hormone when you sleep. This occurs in the deep sleep stage of sleeping when your muscles are completely relaxed. The growth hormone production is lessened when you are not sleeping enough and leaves you feeling sore and weak the next morning.  Not getting enough sleep increases your appetite-inducing hormone, causing you to eat more during the day. It also lowers your sensitivity to insulin and your muscle’s fuel source called glycogen is not replenished enough.  Additionally, getting ample sleep improves your muscle coordination, helping with reaction times, muscle accuracy, and overall muscle performance. This is why, as an athlete, it is recommended to get 8 or 9 hours of good sleep every night for adequate recovery and performance.