Chapter 53 - An Overview of Ornithine, Arginine, and Citrulline in Exercise and Sports Nutrition

Abstract

In improving sports nutrition and exercise performance, a considerable attention has been focused on the integral components of urea cycle, ornithine, arginine, and citrulline. Supplementation of these vital amino acids results in enhanced production of nitric oxide (NO), detoxification of ammonia and secretion of growth hormone (GH) in the body. NO is effective in the vasodilation of blood vessels, which in turn enhances the delivery of nutrients and oxygen to the working muscle during exercise. As demonstrated in the literature, ammonia is the prime cause of exercise-induced fatigue and has been demonstrated to get metabolized into urea in the urea cycle in the hepatic tissues. Protein synthesis and intake of amino acids into the muscle cells are affected by GH; thus supplementation of these amino acids may cause skeletal muscle hypertrophy. A number of studies exhibited the effects of these amino acid supplements on humans and mammals. Emphasis will be given to assess the effect of supplementation of ornithine, arginine, and citrulline on sports performance and exercise.