Did I blow up?

Mike

I finished my first Ironman yesterday. Day went extremely well for the most part. Looking back, I'm curious about something. I'm going to give you a summary of the day and my prior training and then ask a question at the end. The first 13 miles, I felt like a rock star and thought i was holding a pace I could carry to the end. From mile 13 and beyond on the run, I struggled. Physically, each step I took, my muscles felt like they could snap. I felt with each wrong step, I could have pulled a muscle. Never did I feel light headed or like I wasn't going to finish. I never felt just absolutely exhausted. I had to walk and run the last 12 miles. That said, I'm 190 lbs, took in about 300 - 400 calories per hour, temperature all day was high 60's to low 70's. I used carbo pro 1200 to accomplish my calories. also took electrolyte supplements and took in some banana on bike. Prior to this ironman the longest i had ever rode was the 5+ hrs on your program, which took me about 90 miles. Did 1 marathon 5 years ago. Followed your program pretty much to a T. this is my 3rd year of training for triathlons (prior I've always been active at a high level - college soccer). I competed my first 70.3 about 6 wks prior to Ironman. last year i did 4 olympic distance tri's. With that information, Did I blow up on the run or did I just not have a sufficient base to support my pace? What is your interpretation of blowing up? My interpretation of blowing up is not supplying your body enough fuel.

also, what is the purpose of cola on the run? calories, caffiene, sodium?