Preexercise Aminoacidemia and Muscle Protein Synthesis after Resistance Exercise
Burke, Louise M Medicine & Science in Sports & Exercise: POST ACCEPTANCE, 22 May 2012
PURPOSE: We have previously shown that the aminoacidemia caused by the consumption of a rapidly digested protein after resistance exercise enhances muscle protein synthesis (MPS) more than the amino acid (AA) profile associated with a slowly digested protein. Here, we investigated whether differential feeding patterns of a whey protein mixture commencing prior to exercise affect post-exercise intracellular signaling and muscle protein synthesis (MPS).
METHODS: Twelve resistance-trained males performed leg resistance exercise 45 min after commencing each of three volume-matched nutrition protocols: placebo (PLAC; artificially sweetened water); BOLUS (25 g whey protein + 5 g leucine dissolved in artificially sweetened water; 1 x 500 mL); or PULSE (15 x 33 mL aliquots of BOLUS drink every 15 min).
RESULTS: The pre-exercise rise in plasma AA concentration with PULSE was attenuated compared with BOLUS (P<0.05); this effect was reversed following exercise, with two-fold greater leucine concentrations in PULSE compared to BOLUS (P<0.05). One-hour post-exercise, phosphorylation of p70 S6Kthr389 and rpS6ser235/6 was increased above baseline with BOLUS and PULSE, but not PLAC (P<0.05); furthermore, PULSE > BOLUS (P<0.05).
MPS throughout 5 h of recovery was higher with protein ingestion compared with PLAC (0.037 +/-0.007) with no differences between BOLUS or PULSE (0.085 +/-0.013 vs 0.095 +/-0.010 %h-1 respectively, P = 0.56).
CONCLUSIONS: Manipulation of aminoacidemia prior to resistance exercise via different patterns of intake of protein, altered plasma AA profiles and post-exercise intracellular signaling. However, there was no difference in the enhancement of the muscle protein synthetic response after exercise. Protein sources producing a slow AA release, when consumed before resistance exercise in sufficient amounts, are as effective as rapidly digested proteins in promoting post-exercise muscle protein synthesis.