Caffeine

Risk v. Benefit of Caffeine
Posted by Larry on April 22, 2004:
In Reply to: Boston Marathon - Coffee Consumption Survey (or lack of) posted by Steve on April 22, 2004:

David Costill from Ball State, very well known and highly regarded exercise physiologist, studied the science of LD running did a study about 20+ yrs ago about the effect of caffeine consumption on endurance athletes. I attended a series of seminars and lectures he presented and had the opportunity to correspond with him over a semester in the late 70's.

He proved that roughly two cups of coffee (I vaguely remember it as 300mg of caffeine but maybe someone can check or correct me?)consumed within 1-2 hrs of a marathon can be a tremendous benefit to endurance athletes (sorry, 4-6 hrs helps less other than waking you up and getting things moving if you know what I mean).

Without getting too far into the science of it, we know that glycogen in the muscles is one of the main sources that fuels the effort to run 26m. After about 2-3hrs of fairly intense effort you WILL or will nearly exhaust the available glycogen and will find muscles unable to continue to function at the same level (if at all) or function very efficiently (often accompanied by big drop in blood sugar) we've come to know the net of all this as "the wall". The use of gatorade and gu type products can help you keep blood sugar up, allowing you to avoid the associated mental "bonk" that often occurs late in a long race. The gatorade and gu aren't going to replace glycogen while out there but as I understand it, the extra blood sugar will keep your concentration skills more sharp and will give a less potent, less efficient form of fuel for the tough miles.

As to caffeine, in a simplified way when using it your body functions a bit like a hybrid car (using battery power and gas engine together). Use of caffeine appropriately can spare some muscle glycogen by allowing you to use more free fatty acids in your blood stream as a source of fuel in the first hour of the effort. It can enable you to preserve more of the potent fuel, glycogen, for later in the race. All of this assumes all other things are equal and that you running in somewhat ideal and relatively efficient circumstances. (i.e. not 87 degrees for those less acclimatized, not wildly mountainous terrain, not too fast or for that matter not too slowly causing you to be out for hours longer than planned. All of those factors would certainly complicate matters as we saw on Monday.

It has been long held that caffeine functions as a diuretic and thus could add to or cause dehydration. Accordingly it seems that a certain amount of caution would be in order to avoid MORE dehydration on a hot day or in a very long race, all in spite of any potential benefit to your energy stores. I saw something on the topic of caffeine as a diuretic in the news recently but haven't checked into it a detailed way. The story was that the diuretic effect of caffeine had been overstated (not necessarily related to caffeine for endurance athletes) and was less of a problem than once thought. It would be interesting to read or hear a bit more about it.

Somebody mentioned water v. gatorade v. gu in a race. Mr. Costill wrote about this before gu and equivalent products were available and he essentially said that room temp or slightly cooler water empties the stomach in about 30 min and serves the physiological needs of the body to function rather well when exercising for extended periods. His studies showed that most athletes are not nutritionally deficient and accordingly that electrolyte balances aren't a real limiting factor in most trained endurance athletes which minimized the need for some of what the sports replacement drinks offer. He felt that hydration was far more important. The sugar is the thing in the sports drinks, if made in the right proportions it certainly can keep blood sugar higher, can provide a less efficient source of fuel but of course empties the stomach much more slowly, adding potential for further dehydration AND upset to the stomach. If mixed too strong it can cause a bigger problem in all these areas including potential for a reaction in the form of a hypoglycemic crash following the excessive sugar intake.

I wonder if Gary is right and if the best approach might be using water for hydration purposes and then periodically supplementing with Gu to keep blood sugar up? The timing would be important or you'd just be adding sugar to the water in your stomach I suppose (and then, why not just use gatorade?).

I should add here that I am certainly not a current scholar or vaguely an expert in these areas. I haven't kept up with new research in the last 15+ yrs and only have a hobby interest in the subject. Can others add anything more current?

It is a good discussion.