(29-03-08) Effect of dietary protein content during recovery from high-intensity cycling on subsequent performance and markers of stress, infla

Rowlands DS, R?ssler K, Thorp RM, Graham DF, Timmons BW, Stannard SR, Tarnopolsky MA.

Institute of Food, Nutrition and Human Health, Massey University, New Zealand.

Nutrition is an important aspect of recuperation for athletes during multi-day competition or hard training. Post-exercise carbohydrate is likely to improve recovery, but the effect of protein is equivocal. The objective of this study was to determine the effect of post-exercise dietary protein content imposed over a high-carbohydrate background on subsequent performance. Using a crossover design, 12 cyclists completed 3 high-intensity rides over 4 days. Day 1 comprised 2.5 h intervals, followed by repeat-sprint performance tests on days 2 (15 h post) and 4 (60 h post), interspersed with a rest day. During 4 h recovery on days 1 and 2, cyclists ingested either 1.4 g.kg-1.h-1 carbohydrate, 0.7 g.kg-1.h-1 protein and 0.26 g.kg-1.h-1 fat (protein-enriched) or 2.1 g.kg-1.h-1 carbohydrate, 0.1 g.kg-1.h-1 protein, and equal fat (control). At other times, cyclists ingested a standardized high-carbohydrate diet. Anabolism was gauged indirectly by nitrogen balance, stress and inflammation via cortisol and cytokines, skeletal-muscle membrane disruption by creatine kinase, and oxidative stress by malonyl dealdehyde. Sprint mean power was not clearly different on day 2 (0.0%; 95%CL: +/-3.9%), but on day 4 it was 4.1% higher (+/-4.1%) in the protein-enriched condition relative to control. Reduced creatine kinase was possible (26%; +/-30%) but effects on oxidative stress, inflammatory markers, and cortisol were inconclusive or trivial. Overnight nitrogen balance was positive in the protein-enriched condition on day 1 (249 +/- 70 mg N.kg FFM-1; mean +/- SD), but negative (-48 +/- 26 mg N.kg FFM-1) in the control condition. A nutritive effect of post-exercise protein content was not discernible short term (15 h), but a delayed performance benefit (60 h) was observed following protein-enriched high-carbohydrate ingestion.

Source: Appl Physiol Nutr Metab. 2008 Feb;33(1):39-51.

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