Abstract
The effect of oral L-ornithine hydrochloride (0.1 g/kg BW) on energy expenditure during a rest period from 120 to 180 min after resistance exercise was evaluated by indirect calorimetry. Healthy male subjects who have no habit of resistance training underwent resistance exercise (chest press, lat pulldown, leg press, shoulder press, leg extension, and leg curl), with 3 sets of each exercise and 10 repetitions in each set at 90-s intervals, 30 min after ingestion of ornithine or placebo. Plasma ornithine levels immediately after, and 120 and 180 min after, resistance exercise were significantly greater after ingestion of ornithine than of placebo (Treatment: F = 347.1, P p2 = 0.95; Interaction: F = 160.7, P p2 = 0.95), but no significant difference in serum growth hormone levels was observed between the two treatments (Treatment: F = 0.1, P = 0.751, ηp2 = 0.01; Time: F = 1.7, P = 0.229, ηp2 = 0.16; Interaction: F = 2.4, P = 0.155, ηp2 = 0.21). Although there was no between-treatment difference in energy expenditure during the rest period 120 to 180 min after resistance exercise (Treatment: F = 0.1, P = 0.718, ηp2 = 0.02; Time: F = 0.1, P = 0.767, ηp2 = 0.01; Interaction: F = 0.1, P = 0.112, ηp2 = 0.26), with ornithine ingestion carbohydrate oxidation was significantly greater than with placebo from 170 to 180 min after exercise (Treatment: F = 0.8, P = 0.383, ηp2 = 0.09; Time: F = 9.7, P = 0.013, ηp2 = 0.52; Interaction: F = 5.8, P = 0.039, ηp2 = 0.39). Moreover, 180 min after exercise, serum free fatty acid levels after ornithine ingestion were lower than after placebo (Treatment: F = 0.3, P = 0.602, ηp2 = 0.03; Time: F = 34.6, P p2 = 0.79; Interaction: F = 5.6, P = 0.042, ηp2 = 0.38). A similar trend in 3-hydroxybutylate was observed. In conclusion, ornithine ingestion before resistance exercise may enhance post-exercise carbohydrate oxidation without changing total energy expenditure.
Highlights
Many studies have reported that resistance exercise can improve body composition [1,2]
Because there is a decrease in resting respiratory exchange ratio after resistance exercise is finished [4,5,6], lipid oxidation may be increased after this kind of exercise
Levels of growth hormone and other endocrine hormones are elevated by resistance exercise [8], and studies of the dynamics of lipid metabolism have evaluated the effects of injected noradrenaline or growth hormone in humans [9,10]
Summary
Many studies have reported that resistance exercise can improve body composition [1,2]. Because there is a decrease in resting respiratory exchange ratio after resistance exercise is finished [4,5,6], lipid oxidation may be increased after this kind of exercise. For 24 h afterward, resistance exercise has an effect comparable to that of aerobic exercise on total energy expenditure and on the lipid oxidation ratio [7]. Levels of growth hormone and other endocrine hormones are elevated by resistance exercise [8], and studies of the dynamics of lipid metabolism have evaluated the effects of injected noradrenaline or growth hormone in humans [9,10]. Growth hormone secretion is enhanced by resistance exercise or endurance exercise, and by oral ingestion of amino acids such as glutamine, arginine, or ornithine [11,12,13]. We demonstrated that ingestion of ornithine before resistance exercise enhances
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