The effect of ornithine ingestion on carbohydrate metabolism during rest after acute resistance exercise in healthy young males

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 < 0.001, ηp2 = 0.98; Time: F = 175.7, P < 0.001, ηp2 = 0.95; Interaction: F = 160.7, P < 0.001, ηp2 = 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 < 0.001, ηp2 = 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.