Calories vs Carbs
@Sheila Leard - I’ve always managed my races with calorie counting, but have noticed others count carbs (eg, Tim O’Donnell AskMeAnything on SlowTwitch).
What would you say are the advantages / disadvantages of counting carbs vs calories (or vice versatility)?
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@Rich Stanbaugh I saw TO's response that he shoots for about 110 - 120 gm of carbs per hour. That's about 440 - 480 calories per hour! I've followed his story of how he bonked on the marathon in 2019. He blamed it on running out of glycogen. So this year he used UCAN (slow acting carbs) and gels (fast acting) and Roctane, no Gatorade! I had to think about that.
I don't believe there are any true hard and distinct advantages or disadvantages. Depending on the conditions of the race would sway the decision. Typically when going by calories per hour there will be mixed macros. An Ultra Run definitely needs mix macros for satiety. But for a hot and faster race carbs should be the deciding factor ... even for those folks who are good fat burners. If you are going by calories / hour and the protein and fat is too high it will be difficult to access energy to make ATP efficiently. Carbs are still the most efficient way to make ATP. Establishing carbs per hour first then add in fats and protein if needed for satiety and to avoid gut issues with ingesting just carbs.
On another note. Intact protein vs free amino acids have some pros and cons. The studies on BCAA's have shown that free aminos vs whole food protein can help reduce central fatigue in a long race. Paraphrasing form a study: tryptophan is taken up by the brain during endurance exercise. Ingestion of BCAAs may reduce the uptake of tryptophan by the brain and thereby delay fatigue, [reduces serotonin].
*Roctane has BCAA's .