Calorie/Carb Intake

noonievut

I posted this in the Health & Nutrition forum but I thought afterward that this maybe a better forum...any advise is appreciated.

I recently rode a 100km with an avg HR between my Aerobic & High Intesity level (I went harder than I usually would, as I was fighting a strong wind most of the way). When the ride was over, my HRM showed I had burnt 3,700 calories. I felt great throughout the whole ride but by the last 8-10km I had nothing left in the tank and struggled to make it home.

I think my fluid intake was fine as it was a cool day and I drank about 3 bottles of water and 1 amino, but I think I didn't have enough food. For this ride I started with 2 slices of toast w/peanut butter and espresso before the ride, then 1 clif bar, one granola bar and 1 gel during the ride. I spaced it out and thought all was good until the last part of the ride.

So, how does one calculate how many calories/carbs are required on a ride? Also, for 100-170km rides do you need more than bars & gels, or does it not make a difference?

Thanks.