Kat and I were just tested metabolically by my coach Janda Ricci Muun at Seaside Cycles in Manchester, Mass. The primary goal was to see from where I derived my calories during training. What percentage do I get from free fatty acids (HUGE RESERVE SUPPLY) or muscle glycogen (LIMITED SUPPLY)? We want to know how much I will need to supplement during my Ironman race in Austria next month. This is ground breaking stuff and really opened my eyes to my personal need to stay on top of nutrition. Lets just say, I am not genetically made to go long distances without resupplying food wise. Kat on the other hand, is made for this. Maybe I should stick to sprint racing. Here are the numbers.
My sweet spot is 200-215 watts. I am burning about the same amount from fats as I am glycogen. ( 6 – 7 calories of glycogen per min. at that zone + 7 – 8 calories worth of FFAs)
At that rate, we’re looking @ 360 – 420 calories worth of glycogen per hour being expended. We’ll call it 420 just to be safe.

420 x 5.5 hours on the bike = 2310 calories worth of MG depleted. In other words, I dont store this amount of sugar in my muscles and I will bonk by the end of the ride if I dont eat during it.

If I consume 350 calories per hour on the bike (i.e. 25 oz. of sport drink + 2 x gels), that reduces the deficit to 385 calories. Add to that the swim (we’ll say 500 calories worth of MG depleted) and we’re down 835 (roughly 1400 calories worth of MG remaining). Assuming 10 calories of MG per min. on the run, we’re looking at 600 calories of MG per hour expended or a little over 2 hours until bonk.

Consuming 250 calories of sugar per hour = we only lose 350 per hour on the run.

350 x 3.5 hour run = 1225 calories expended and I cross the line with about 175 calories worth of MG left in his system in 10.5 hours.
Tad da…..its as easy as that. LOL