SummaryThe effects of branched-chain amino acid (BCAA) supplementation on the lactate threshold (LT) were investigated as an index of endurance exercise capacity. Eight trained male subjects (21 Ϯ 2 y) participated in a double-blind crossover placebo-controlled study. The subjects were randomly assigned to two groups and were provided either a BCAA drink (0.4% BCAA, 4% carbohydrate; 1,500 mL/d) or an iso-caloric placebo drink for 6 d. On the 7th day, the subjects performed an incremental loading exercise test with a cycle ergometer until exhaustion in order to measure the LT. The test drink (500 mL) was ingested 15-min before the test. Oxygen consumption (V · O 2 ) and the respiratory exchange ratio (RER) during the exercise test were measured with the breath-by-breath method. Blood samples were taken before and during the exercise test to measure the blood lactate and plasma BCAA concentrations. The same exercise test was performed again 1 wk later. BCAA supplementation increased the plasma BCAA concentration during the exercise test, while plasma BCAA concentration decreased in the placebo trial. The RER during the exercise test in the BCAA trial was lower than that in the placebo trial ( p Ͻ 0.05). The V · O 2 and workload levels at LT point in the BCAA trial were higher than those in the placebo trial (V · O 2 : 29.8 Ϯ 6.8 vs. 26.4 Ϯ 5.4 mL/kg/min; workload: 175 Ϯ 42 vs. 165 Ϯ 38 W, p Ͻ 0.05, respectively). The V · O 2 max in the BCAA trial was higher than that in the placebo trial (47.1 Ϯ 5.7 vs. 45.2 Ϯ 5.0 mL/kg/min, p Ͻ 0.05). These results suggest that BCAA supplementation may be effective to increase the endurance exercise capacity. Key Words branched-chain amino acid, lactate threshold, energy metabolism, endurance exercise capacity, trained individuals Branched-chain amino acids (BCAA), valine, leucine and isoleucine, are used in skeletal muscle during exercise as an energy source ( 1 -4 ). The proteolysis of whole-body protein and amino acid utilization as an energy source has been reported to increase during exercise ( 5 -7 ). In addition, leucine oxidation has been reported to enhance with the increase in exercise intensity ( 8 , 9 ), and the plasma BCAA concentration has been reported to decrease with prolonged exercise ( 10 ). BCAA metabolites enter the TCA cycle directly as acetyl-CoA and/or succinyl-CoA not via the glycolytic pathway, and therefore lactate is not produced during BCAA metabolism ( 2 ). As a result, the increase in BCAA oxidation induced by the BCAA supplementation is thus considered to decrease lactate production during exercise. De Palo et al. has reported that BCAA ingestion following chronic BCAA supplementation suppresses the increase in blood lactate level during exercise in athletes ( 11 ).The blood lactate concentration drastically increases during exercise beyond the intensity of the lactate threshold (LT) level, because anaerobic glycolysis becomes the dominant energy pathway ( 12 ). Therefore, the LT is thus considered to reflect the energy metabolism, especially the g...

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We examined the effect of running training on age-related changes in cardiac myosin isozyme composition in rats. Female Fischer 344 rats (6, 12, 20, and 27 months old) were divided into two groups: sedentary control and trained. The trained group rats were trained by treadmill running for up to 60 minutes per day, 5 days per week for 8 weeks at up to 30 m per minute. In sedentary control rats, the proportion of V1 myosin, that is, alpha-myosin heavy chain (MyHC) isoform, decreased progressively from 6 to 27 months of age. In the younger age groups (6 or 12 months old), there was a shift from V1 myosin to V3 myosin (beta-MyHC isoform) in trained hearts. However, the training program did not induce a cardiac myosin isozyme transition in older rats (20 or 27 months old). These results suggest that the mechanisms mediating the responses of cardiac muscle to running training alter during aging.

Effects of dietary comp sition of pre ・ exercise meal on liver and musde 9 且 ycogen dep且 etion and lipOlytic activity during prolonged exercise in rats ： comparison of ahigh ． carbOhydrate diet and a high ・ fat diet