. Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise. Am J Physiol Endocrinol Metab 281: E197-E206, 2001.-The present study was designed to determine whether consumption of an oral essential amino acid-carbohydrate supplement (EAC) before exercise results in a greater anabolic response than supplementation after resistance exercise. Six healthy human subjects participated in two trials in random order, PRE (EAC consumed immediately before exercise), and POST (EAC consumed immediately after exercise). A primed, continuous infusion of L-[ring-2 H5]phenylalanine, femoral arteriovenous catheterization, and muscle biopsies from the vastus lateralis were used to determine phenylalanine concentrations, enrichments, and net uptake across the leg. Blood and muscle phenylalanine concentrations were increased by ϳ130% after drink consumption in both trials. Amino acid delivery to the leg was increased during exercise and remained elevated for the 2 h after exercise in both trials. Delivery of amino acids (amino acid concentration times blood flow) was significantly greater in PRE than in POST during the exercise bout and in the 1st h after exercise (P Ͻ 0.05). Total net phenylalanine uptake across the leg was greater (P ϭ 0.0002) during PRE (209 Ϯ 42 mg) than during POST (81 Ϯ 19). Phenylalanine disappearance rate, an indicator of muscle protein synthesis from blood amino acids, increased after EAC consumption in both trials. These results indicate that the response of net muscle protein synthesis to consumption of an EAC solution immediately before resistance exercise is greater than that when the solution is consumed after exercise, primarily because of an increase in muscle protein synthesis as a result of increased delivery of amino acids to the leg.

This study was designed to determine the response of muscle protein to the bolus ingestion of a drink containing essential amino acids and carbohydrate after resistance exercise. Six subjects (3 men, 3 women) randomly consumed a treatment drink (6 g essential amino acids, 35 g sucrose) or a flavored placebo drink 1 h or 3 h after a bout of resistance exercise on two separate occasions. We used a three-compartment model for determination of leg muscle protein kinetics. The model involves the infusion of ring-(2)H(5)-phenylalanine, femoral arterial and venous blood sampling, and muscle biopsies. Phenylalanine net balance and muscle protein synthesis were significantly increased above the predrink and corresponding placebo value (P < 0.05) when the drink was taken 1 or 3 h after exercise but not when the placebo was ingested at 1 or 3 h. The response to the amino acid-carbohydrate drink produced similar anabolic responses at 1 and 3 h. Muscle protein breakdown did not change in response to the drink. We conclude that essential amino acids with carbohydrates stimulate muscle protein anabolism by increasing muscle protein synthesis when ingested 1 or 3 h after resistance exercise.

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Aging is generally accompanied by weight loss made up of both fat mass and fat-free mass. As more people, including elderly, are overweight or obese, weight loss is recommended to improve health. Health risks are decreased in overweight children and adults by dieting and exercise, but the health benefits of weight loss in elderly, particularly by calorie restriction, are uncertain. Rapid unintentional weight loss in elderly is usually indicative of underlying disease and accelerates the muscle loss which normally occurs with aging. Intentional weight loss, even when excess fat mass is targeted also includes accelerated muscle loss which has been shown in older persons to correlate negatively with functional capacity for independent living. Sarcopenic obesity, the coexistence of diminished lean mass and increased fat mass, characterizes a population particularly at risk for functional impairment since both sarcopenia (relative deficiency of skeletal muscle mass and strength) and obesity have been shown to predict disability. However, indices of overweight and obesity such as body mass index (BMI) do not correlate as strongly with adverse health outcomes such as cardiovascular disease in elderly as compared to younger individuals. Further, weight loss and low BMI in older persons are associated with mortality in some studies. On the other hand, studies have shown improvement in risk factors after weight loss in overweight/obese elderly. The recent focus on pro-inflammatory factors related to adiposity suggest that fat loss could ameliorate some catabolic conditions of aging since some cytokines may directly impact muscle protein synthesis and breakdown. Simply decreasing weight may also ease mechanical burden on weak joints and muscle, thus improving mobility. However, until a strategy is proven whereby further loss of muscle mass can be prevented, weight loss by caloric restriction in individuals with sarcopenic obesity should likely be avoided.