Sleep is a vital part of your ability to grow muscle, which is why we have grouped Nighttime Sleep Formulas in the Growth Enhancers category. Sleep allows users to conserve energy and restore brain cells – both of which fuels mental alertness and growth. By contrast, a lack of sleep can hinder a person’s ability to build muscle. This category includes a range of products said to help increase REM sleep, which in turn can allow the body to attain an optimal state for muscle recovery and growth. However, these products are not just marketed as a way to improve sleep with muscle gains as a helpful by-product. In fact, many of these products include ingredients said to help increase lean mass alongside those thought to improve sleep quality.