Rapidly digested and absorbed proteins enhance the muscle protein synthesis response following resistance exercise, with the degree of hyperaminoacidemia suggested to be an important consideration. However, most studies have used supplemental protein sources, with little focus on how consumption of protein within a mixed meal influences postprandial amino acid (AA) responses.
PURPOSE: To examine the pattern of postprandial AA responses to consuming whey protein isolate before or within a mixed meal after resistance exercise.
METHODS: Eight resistance trained men (age 21 (1) y; body mass 80.2 (8.4) kg; body fat 13 (6) %) completed two trials in a randomized order. Trials consisted of ~1 h lower-body resistance exercise, a 30 min post-exercise feeding period and a further 150 min supine rest period. Post-exercise nutrition was identical in composition (400 mL water at 0 min; an oat flapjack + 600 mL
water at 15-30 min) and included 20 g of whey protein isolate, which was either consumed in the drink at 0 min (SUPP) or mixed into the oat flapjack consumed at 15-30 min (MEAL). Blood samples were taken every 15-30 min post-exercise to determine amino acid, glucose and insulin concentrations.
RESULTS: Compared to MEAL, leucine and essential AA (EAA) concentrations were higher at 15-50 min and lower at 120-180 min in SUPP (P<0.05), whilst total AA (TAA) concentrations were higher at 30-50 min and lower at 150 min in SUPP. Peak leucine (SUPP 414 (70) mmol/L; MEAL 216 (40) mmol/L; P<0.001), EAA (SUPP 2404 (411) mmol/L; MEAL 1502 (235) mmol/L; P<0.001) and TAA (SUPP 4860 (759) mmol/L; MEAL 3450 (467) mmol/L; P<0.01) concentrations were all greater during SUPP vs MEAL, with peak concentrations also achieved earlier in SUPP. Total postprandial area under the curve for leucine, EAA and TAA concentrations were all greater during SUPP (P<0.05). There were no between-trial differences for glucose or insulin responses (P>0.05).
CONCLUSIONS: Consumption of protein in supplemental form prior to, rather than within a mixed meal, facilitates a more rapid and pronounced postprandial aminoacidemia following resistance exercise. This might offer some advantage where maximizing the anabolic effect of resistance exercise is desirable.
This project received no funding. The whey protein isolate was provided by Volac International Ltd.