Hydroxyisocaproic acid is an end product of leucine metabolism in human tissues such as muscle and connective tissue. It belongs to 2-hydroxycarboxylic acid group of amino acid metabolites. Hydroxyisocaproic acid functions as an “anti-catabolite and is widely used in the bodybuilding community. Chronic alpha-hydroxyisocaproic acid treatment of rats has been shown to improve muscle recovery after immobilization-induced atrophy. Additionally, a 4-week hydroxyisocaproic acid supplementation of 1.5 g a day was shown to lead to increases in muscle mass during an intensive training period among soccer athletes.