an important buffer which can neutralize organic acids accumulated from protein breakdown, and also help to neutralize lactic acid released from muscle during anaerobic glycolysis. When lactic acid combines with bicarbonate, carbon dioxide gas and water are formed. The carbon dioxide is excreted through the lungs. By increasing the concentration of bicarbonate in blood, the buffering capacity is increased for lactic acid. B. Carbohydrate Loading It was previously recommended that a 3 day regimen be used to load glycogen stores (3-5) but during rest days prior to an event it is now recommended that a 65-70% carbohydrate diet be ingested as discussed above. Many athletes also load carbohydrates just before an event. This pre-exercise loading depends on the period remaining until exercise and will vary from 1 to 4 gm carbohydrate/kg as follows (6):
Example: for a 64 kg athlete -
1 hr. before exercise: 64 g. of carbohydrate 2 hr. before exercise: 128 g. “ 3 hr. before exercise: 192 g. “ 4 hr. before exercise: 256 g. “
During exercise it is recommended that 15 to 30 gm/ half hour be ingested (7,8). The most rapid glycogen depletion occurs immediately after exercise. Waiting 2 to 3 hours after exercise to ingest carbohydrates reduces the rate of glycogen repletion, while taking 50 to 75 grams of carbohydrate within 30 minutes followed by 50 to 75 gm every 2 hr can help speed glycogen repletion (9). C. Branched Chain Amino Acids The branched chain amino acids (isoleucine, leucine, and valine) have a special role in metabolism. Alanine is one of the most important amino acids used for glucose synthesis between meals or in the fasting state via the Alanine Cycle (see below). Alanine → liver to form glucose NH2 removed to form pyruvate in the process then pyruvate to glucose by gluconeogenesis
Glucose formed from Alanine is then utilized, releasing pyruvate Pyruvate → muscle where it gains an NH2 to form Alanine again