Effect of glucose supplement timing on protein metabolism after resistance training.

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Abstract
Roy, B. D., M. A. Tarnopolsky, J. D. MacDougall, J. Fowles, and K. E. Yarasheski. Effect of glucose supplement timing on protein metabolism after resistance training. J. Appl. Physiol. 82(6): 1882–1888, 1997.—We determined the effect of the timing of glucose supplementation on fractional muscle protein synthetic rate (FSR), urinary urea excretion, and whole body and myofibrillar protein degradation after resistance exercise. Eight healthy men performed unilateral knee extensor exercise (8 sets/∼10 repetitions/∼85% of 1 single maximal repetition). They received a carbohydrate (CHO) supplement (1 g/kg) or placebo (Pl) immediately ( t = 0 h) and 1 h ( t = +1 h) postexercise. FSR was determined for exercised (Ex) and control (Con) limbs by incrementall-[1-13C]leucine enrichment into the vastus lateralis over ∼10 h postexercise. Insulin was greater ( P < 0.01) at 0.5, 0.75, 1.25, 1.5, 1.75, and 2 h, and glucose was greater ( P < 0.05) at 0.5 and 0.75 h for CHO compared with Pl condition. FSR was 36.1% greater in the CHO/Ex leg than in the CHO/Con leg ( P = not significant) and 6.3% greater in the Pl/Ex leg than in the Pl/Con leg ( P = not significant). 3-Methylhistidine excretion was lower in the CHO (110.43 ± 3.62 μmol/g creatinine) than Pl condition (120.14 ± 5.82, P < 0.05) as was urinary urea nitrogen (8.60 ± 0.66 vs. 12.28 ± 1.84 g/g creatinine, P < 0.05). This suggests that CHO supplementation (1 g/kg) immediately and 1 h after resistance exercise can decrease myofibrillar protein breakdown and urinary urea excretion, resulting in a more positive body protein balance.