As you probably already know, most nitric oxide (NO) boosters use some form of the amino acid citrulline. Citrulline is converted to arginine in the body, which is then converted to NO. Citrulline is not only a powerful NO booster but it also delays fatigue and drives up energy levels. Citrulline also aids in the removal of ammonia from the body. In fact, clinical studies confirm that subjects taking citrulline malate experience less fatigue and have higher energy levels. What many bodybuilders may not realize is that citrulline supplementation may also have an anabolic effect via increasing the rate of muscle protein synthesis. Producing NO is one of the most important mechanisms necessary for increasing blood flow to muscle tissue. A previous study reported that patients who were given a single citrulline supplementation dose had a 24% rise in nitrogen balance. Additionally, recent research in animals has found that inhibiting NO can decrease overall muscle gains and the growth of capillaries within muscle tissue. It can be hypothesized that reduced capillary growth, limiting the availability of nutrients to muscles, is directly related to decreased muscle development. Nitric oxide also allows for an increased delivery of anabolic hormones such as testosterone, growth hormone, and insulin-like growth factor-1, which are key for packing on more muscle. So be sure to include a citrulline based pre-workout supplement for optimal gains in strength and muscle mass.