Training in the range of 5 to 7 will also Power Growth decrease the amount of lactic acid that is secreted within the muscles. Lactic acid is a metabolic waste product that is produced as the body burns carbohydrates for fuel. Lactic acid accumulates in the muscle tissue at increased rates the longer you exercise. By limiting the amount of lactic acid production you will decrease muscle catabolism and create an environment in the body where greater amounts of energy can be generated.http://rockhardfacts.com/power-growth/