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Coingestion of protein and/or free amino acids with carbohydrate has been reported to accelerate postexercise muscle glycogen synthesis due to an increase in the insulin response.To determine the extent to which the combined ingestion of carbohydrate and a casein protein hydrolysate with or without additional free leucine can increase insulin levels during postexercise recovery in endurance-trained athletes. To determine how this affects whole-body plasma glucose disposal during postexercise recovery.Fourteen male athletes (age: 24.3 ± 0.8 yr; V̇O2max: 62.9 ± 1.4 mL·kg−1·min−1) were subjected to three randomized crossover trials in which they performed 2 h of exercise (55% Wmax). Thereafter, subjects were studied for 3.5 h during which they ingested carbohydrate (CHO: 0.8 g·kg−1·h−1), carbohydrate and a protein hydrolysate (CHO-PRO: 0.8 and 0.4 g·kg−1·h−1, respectively), or carbohydrate, a protein hydrolysate, and free leucine (CHO-PRO-LEU: 0.8, 0.4, and 0.1 g·kg−1·h−1, respectively) in a double-blind fashion. Continuous infusions with [6,6-2H2] glucose were applied to quantify plasma glucose appearance (Ra) and disappearance rates (Rd).Plasma insulin responses were 108 ± 17 and 190 ± 33% greater in the CHO-PRO and CHO-PRO-LEU trial, respectively, compared with the CHO-trial (P < 0.01). Plasma glucose responses were lower in the CHO-PRO and CHO-PRO-LEU trial compared with the CHO-trial (35 ± 5 and 42 ± 11% lower, respectively; P < 0.01). Plasma glucose Ra and Rd were greater in the CHO versus the CHO-PRO and CHO-PRO-LEU trials (P < 0.05). Glucose Rd represented 100 ± 0.03% of Ra in all trials.The combined ingestion of a protein hydrolysate and/or free leucine with carbohydrate (0.8 g·kg−1·h−1) substantially augments insulin secretion, but does not affect plasma glucose disposal during the first 3.5 h of postexercise recovery in trained athletes.