I have read in many places that the body can only absorb 400-500 calories per hour, depending on body size.
Mark Alan refers (in last Trimag) to recent research indicating that you can “train” your body to burn more than that. If anyone has seen the scientific research on this, please point it out. It sounds very interesting.
Perhaps I misunderstood you, but the ability to abosrb and to burn is different.
Mark Alan refers (in last Trimag) to recent research indicating that you can “train” your body to burn more than that
I am no Mark Allen, but according to my heart rate monitor I sometimes burn nearly 1000 calories in one hour. In a 25 miles TT I did 2 months ago I cycled only a few minutes more than an hour and I burnt approx 1,200. I know that the Polar I use is only based on a mathemtical estimate. In a medical book I have they refer to running as an acitivity with a mean score of 600 calories per hour.
In terms of the ability of the body to absorb (i.e. from food) I can see that if I am able to abosrb what I burn, I may be able delay the onset of fatigue and sustain activity for a longer duration. How do I train this ability? The only way I am aware of getting a similar effect is by “teaching” the body to rely on fat storage and therefore, using less glycogen. As a result, one is able to abosrb similar quantities to what they burn. If I train my body to absorb more it also means that I rely less on fat and effectively use a higher intensity. Coud you explain how this training is done?
What I’m talking about here is ability to absorb. If you can absorb more, then glycogen depletion would be delayed.
Here’s the quote from August '04 Triathlete Magazine, the article on page 92 is entitled “Race Nutrition - Plan Now For Success Later”, by Mark Allen:
“A160-pound male burns roughly 100 calories per mile when running, or about 700 calories per hour, at high levels of exercise intensity on the bike…Research shows that , in general, a person cannot absorb more than 500 calories per hour. So you can see a 160-pound male looks like he will go into deficit fairly early in an Ironman. But take heart, because additional research has shown that one can develop the ability to absorb more calories per hour if you eat more than the 500 calories per hour during your training.”
I’m wondering if anyone has read about this new research. I know that Mark told us in a seminar here a few years ago that he thinks he probably took in well over 500 calories per hour during his Ironman heyday.
According to the e-caps people its 280 calories
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Ya…I’ve exchanged emails with those guys on this issue. They are way off, in my opinion.
I’m 180lbs and can absorb 600 calories per hour easily. I might try to go higher after reading Mark’s article.
I think I am learning a lot this year about calories burned (thanks to the HRM) and calories consumed both in training and racing, all in preparation of my first IM (Canada in only 4 freakin’ weeks! Aargh!).
Major Points:
First of all, I am only 5’4” and 142 lbs. You really need to adjust numbers on your size. The differences can be rather surprising.
In workouts, I typically burn between 425 and 500 calories per hour either running or cycling (aerobic efforts, mostly zone 2 and a little 3 for 2-6 hours). Races, particularly sprints, can get me up to around 650 calories per hour.
I use Accelerade only in short races, and Accelerade and Hammer gel for long (half-IM and future IMs) races.
At best, I can take in about 300 calories an hour. It is much easier to do this in training when the heart rate is typically 120-140ish. At higher heart rates, say mid 150’s which is near the upper aerobic limit for me, I have found absorption goes noticeably slower.
I am not terribly hungry at the finish of a half-IM. Then again, I am also probably around 15% body fat, which I think I burn pretty well. I did do a very good job this last winter building up an aerobic base. I figure I run a 250-300 calorie per hour deficit during a race. I have yet to learn whether this will bite me in the butt in an IM. My one backup option is the soup broth and coke during the run. (I hope they don’t run out!)
At Blackwater Eagleman this year, I was taking in under 300 calories per hour. I noticed that I was getting a definite boost on the bike after each hit of Accelerade. I probably should have consumed more during the bike. I tried to correct this two weeks later at the Tupperman half-IM by using a four-fold concentration of Accelerade. One, it was a little too intense on the bike after an hour or so, and two, I found that a lot of it was still sitting in my gut when I started the run. I cruised the first 9 miles of the run on just water, letting my stomach settle and managed a good run out of it anyway.
Faster races equals higher stress both cardiovascular and gastro intestinally. Willing yourself to absorb more won’t make it so. The good news is the faster the race, the shorter time wise, and the less you need to worry about nutrition during the race.
Find the solution strength you can handle for the length and intensity of the race. If concerned, pack a little more than you think you will consume. Long races, with lower intensity should allow for more absorption, and one should be able to get close to their maximum limit.
My empirical rules of thumb:
Maximum calories absorbable per hour is proportional to length of race.
Maximum calories absorbable per hour is inversely proportional to race intensity.
Calories needed per hour is proportional to race length.
If you are skinny, you may need to be at the higher limits of your absorption rate.
If your aerobic engine is subpar, you may need to be at the higher limits of your adsorption rate.
Lastly, Lisa Bently in an interview for the 2003 IMC race video, indicated that she burns 800 or more calories per hour in an Ironman. I have to think that Mark Allen and Dave Scott as well as most all pro men burn this much or more. So, even at 500+ calories per hour, Mark would be running a deficit. In my opinion, everyone runs a deficit. You are suppose to stay aerobic for 99% of the race to burn fat to account for the difference as I understand it.
Good Luck.