Abstract
Recently we observed that the addition of leucine with protein to high-carbohydrate recovery feeding ingested following intense cycling over 3 days led to a small enhancement in subsequent performance. It is also established that post-exercise protein feeding, both with and without added leucine, attenuates muscle damage and soreness, and can increase muscle-protein synthesis, but the metabolic consequences are largely unknown. PURPOSE: To investigate further putative mechanisms and the effects on metabolism of a post-exercise leucine-protein supplement and confirm a benefit to subsequent performance. METHODS: In a double-blind randomized crossover, 12 male cyclists ingested either a leucine/protein/carbohydrate/fat supplement (LEUPRO; respectively 7.5/20/89/22 g·h-1) or isocaloric carbohydrate/fat control (CON: 119/22 g·h-1) for 1-3 h post-exercise during a 6-day training block. Protein intake was clamped at 1.9 (LEUPRO) and 1.5 g·kg-1d∑-1 (CON). Using stable isotope methodology and LC-MS based metabolomics we determined the impact of LEUPRO on leucine turnover and amino acid metabolism. RESULTS: Following exercise, LEUPRO increased branch-chain amino acids (BCAA) in plasma (2.6-fold; 90%CL ×/÷1.1) and urine (2.8-fold; ×/÷1.2) and products of their metabolism: plasma acylcarnitine C5 (3.0-fold; ×/÷0.9) and urinary β-aminoisobutyrate (3.4-fold; ×/÷1.4). LEUPRO also increased whole-body leucine oxidation (5.6-fold; ×/÷1.1) and synthesis (4.8-fold; ×/÷1.1), and only with LEUPRO was recovery leucine balance (mean ± SD: 580 ± 215 μmol·kg-1h∑-1, control; -43 ± 24 μmol·kg-1h∑-1) and day-1 nitrogen balance (17 ± 20 mg·kg-1, control; -90 ± 44 mg·kg-1) positive. However, subsequent day 2-5 nitrogen balance was positive in CON (111 ± 86 mg·kg-1; LEUPRO: 130 ± 110 mg·kg-1). LEUPRO reduced serum creatine kinase by 21-25% (90%CL ±14%). Despite these effects, the impact of LEUPRO on sprint power was trivial (day 4: 0.4% ±1.0%; day 6: -0.3% ±1.0%). CONCLUSIONS: Despite saturation of post-exercise BCAA metabolism and apparent attenuated tissue damage, a leucine-protein supplement had a trivial effect on performance compared to control, possibly due to both treatment groups being in positive nitrogen balance. Supported by a grant from Nestec Ltd., Vevey, Switzerland.
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