CYCLING PERFORMANCE TIPS
J Appl Physiol. 2009 Apr;106(4):1394-402. Epub 2008 Nov 26
Howarth KR, Moreau NA, Phillips SM, Gibala MJ
Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
Coingestion of protein with carbohydrate (CHO) during recovery from exercise
can affect muscle glycogen synthesis, particularly if CHO intake is
suboptimal. Another potential benefit of protein feeding is an increased
synthesis rate of muscle proteins, as is well documented after resistance exercise.
In contrast, the effect of nutrient manipulation on muscle protein kinetics
after aerobic exercise remains largely unexplored. We tested the
hypothesis that ingesting protein with CHO after a standardized 2-h
bout of cycle exercise would increase mixed muscle fractional
synthetic rate (FSR) and whole body net protein balance (WBNB) vs.
trials matched for total CHO or total energy intake. We also examined
whether postexercise glycogen synthesis could be enhanced by adding protein
or additional CHO to a feeding protocol that provided 1.2 g CHO x kg(-1) x h(-1),
which is the rate generally recommended to maximize this process. Six active
men ingested drinks during the first 3 h of recovery that provided
either 1.2 g CHO.kg(-1).h(-1) (L-CHO), 1.2 g CHO + 0.4 g protein x kg(-1) x h(-1)
(PRO-CHO), or 1.6 g CHO x kg(-1) x h(-1) (H-CHO) in random order. Based
on a primed constant infusion of l-[ring-(2)H(5)]phenylalanine, analysis
of biopsies (vastus lateralis) obtained at 0 and 4 h of recovery showed
that muscle FSR was higher (P < 0.05) in PRO-CHO (0.09 +/- 0.01%/h) vs.
both L-CHO (0.07 +/- 0.01%/h) and H-CHO (0.06 +/- 0.01%/h). WBNB assessed
using [1-(13)C]leucine was positive only during PRO-CHO, and this was
mainly attributable to a reduced rate of protein breakdown. Glycogen
synthesis rate was not different between trials. We conclude that
ingesting protein with CHO during recovery from aerobic exercise
increased muscle FSR and improved WBNB, compared with feeding
strategies that provided CHO only and were matched for total CHO or total
energy intake. However, adding protein or additional CHO to a feeding
strategy that provided 1.2 g CHO x kg(-1) x h(-1) did not further enhance
glycogen resynthesis during recovery.