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Following up on my post on maximizing carbohydrate absorption during exercise a few months ago, I got an interesting e-mail from a triathlete named Josh (yeah, I’m still way behind in catching up on e-mail since the trip to Nepal!). His question was basically: Forget about averages, how high can an individual outlier push his or her rate of carb absorption, with training and good genetics?
I’m a tall and lean guy and at Ironman this past year I ate 600 calories [150 g] per hour for 5 hours on the bike and ate at around 450 cal [~112 g]/hour on the run. That’s well in excess of ANY average rate that anyone has ever suggested is “possible on average”…
It’s an interesting question. After all, as Josh pointed out, the average marathon time is around four hours, but we don’t focus our training discussions on how to be average. So I dug up Asker Jeukendrup’s recent review of multiple transportable carbs to see if it would shed any light.
The first key point, of course, is the difference between ingestion and absorption. While Josh was ingesting 150 g an hour, that doesn’t mean all those carbs were reaching his muscles — they could be hanging around in his stomach, or passing through his intestine without being absorbed into the bloodstream, destined for an eventual rear exit. A very nice table in Jeukendrup’s paper sums of the results of 13 studies: Continue reading “How many carbs can a super-carb-absorber absorb during a triathlon?”