Abstract
BackgroundThe pattern of protein intake following exercise may impact whole-body protein turnover and net protein retention. We determined the effects of different protein feeding strategies on protein metabolism in resistance-trained young men.MethodsParticipants were randomly assigned to ingest either 80g of whey protein as 8x10g every 1.5h (PULSE; n=8), 4x20g every 3h (intermediate, INT; n=7), or 2x40g every 6h (BOLUS; n=8) after an acute bout of bilateral knee extension exercise (4x10 repetitions at 80% maximal strength). Whole-body protein turnover (Q), synthesis (S), breakdown (B), and net balance (NB) were measured throughout 12h of recovery by a bolus ingestion of [15N]glycine with urinary [15N]ammonia enrichment as the collected end-product.ResultsPULSE Q rates were greater than BOLUS (~19%, P<0.05) with a trend towards being greater than INT (~9%, P=0.08). Rates of S were 32% and 19% greater and rates of B were 51% and 57% greater for PULSE as compared to INT and BOLUS, respectively (P<0.05), with no difference between INT and BOLUS. There were no statistical differences in NB between groups (P=0.23); however, magnitude-based inferential statistics revealed likely small (mean effect±90%CI; 0.59±0.87) and moderate (0.80±0.91) increases in NB for PULSE and INT compared to BOLUS and possible small increase (0.42±1.00) for INT vs. PULSE.ConclusionWe conclude that the pattern of ingested protein, and not only the total daily amount, can impact whole-body protein metabolism. Individuals aiming to maximize NB would likely benefit from repeated ingestion of moderate amounts of protein (~20g) at regular intervals (~3h) throughout the day.
Highlights
The pattern of protein intake following exercise may impact whole-body protein turnover and net protein retention
Recommendations for dietary protein intake for healthy adults currently provide guidelines according to the total daily quantity of protein intake [1,2], while new guidelines for athletes note the importance of protein intake immediately after a resistance training session [3]
Given the known effect of dietary protein on the enhancement of muscle and whole-body protein synthesis [9] and the apparent advantage to balanced protein ingestion for whole-body nitrogen retention [5], we provided trained young men with isonitrogenous amounts of high quality protein that differed only in the pattern of ingestion to determine its effect on whole-body protein metabolism over a prolonged postprandial period
Summary
The pattern of protein intake following exercise may impact whole-body protein turnover and net protein retention. We determined the effects of different protein feeding strategies on protein metabolism in resistance-trained young men. Recommendations for dietary protein intake for healthy adults currently provide guidelines according to the total daily quantity of protein intake [1,2], while new guidelines for athletes note the importance of protein intake immediately after a resistance training session [3]. Given the known effect of dietary protein on the enhancement of muscle and whole-body protein synthesis [9] and the apparent advantage to balanced protein ingestion for whole-body nitrogen retention [5], we provided trained young men with isonitrogenous amounts of high quality protein that differed only in the pattern of ingestion to determine its effect on whole-body protein metabolism over a prolonged postprandial period. The period of investigation was in the 12h period immediately following a bout of resistance exercise to standardise and take advantage of the accentuated protein synthesis in the exercised muscle over this period [12]
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