One ergogenic aid that may be useful in some circumstances is the use of creatine at 20 grams per day for 5-6 days and then a maintenance dose of 2 grams per day to improve performance in those who undertake repeated bursts of activity, such as in sprinting or weightlifting.* promotion of mental alertness by athletes can be achieved through the use of caffeine in a dose of about 3-9 milligrams per kilogram of body weight.* a possibly useful - but still under study - ergogenic aid used as an important energy source when carbohydrate stores are depleted are branched-chain amino acids such as leucine, isoleucine, and valine.* an ergogenic aid that increases muscle mass but may also cause uncontrolled growth of the heart or other organs and is banned by the international olympic committee is growth hormone.