Iceman Cometh .....didnt end so well

I've had lots of experience with dehydration, so I can tell you that it'll definitely mess you up. Low electrolytes will contribute as well. I've used Gu Brew before on short/medium runs, but for races that are long or where I sweat a lot, it doesn't seem to do the trick for me.  Some people will use salt tabs...I've done it a few times, but only on really long races.

The other thing too with racing in colder conditions is that its really easy to get dehydrated - you don't quite realize how much you're sweating.

Another thing that's a possibility is if you changed anything about your nutrition plan or didn't practice a nutrition plan.  Its really important to race the way you train.

By the way, good job powering through what obviously was not a very pleasant experience.

Thank you for the replies!

-Pre race meal @ 7am : 1 plain bagel, 1 banana, 1 yoghurt, 1 small coffee, 1 20oz bottle of water. The only pre race meal change was the coffee.

-During the hour before the race: 1 20oz bottle gatorade, 1 GU gel 15 mins before the start with a couple of mouth fulls of water.

-Wave start was at 10.45am

-Admittedly of late i have been doing most of my hard bike sessions on the trainer, and during those sessions i almost always use only water. During tri season i was doing 2 hard 1hr interval sessions outdoors - most of them were in the morning so i would have a gel when i woke up and bottle of GU brew on the bike.

-Both of you made a good point that i probably havent sufficiently trained with the same nutrition as what i raced with.

Congrats on a new PR for Iceman!  I raced it as well last weekend.  What an awesome day it was indeed!

One huge difference between mtb racing and tri's is the more frequent and sometimes extended redlining.  In tri's we often stay at threshold for extended periods without quite going redline.  In mtb you tend to redline for sometimes more extended periods before you get a stretch of course you can actively recover.  Our bodies will deal with this unique stressor sometimes in quite a different way than extended periods at threshold. 

What was your mtb training like prior to the race?  Did you do a lot of interval & negative split training to adapt your body to living in a deficit state for extended periods?  Much like triathlon learning to live on the edge of anaerobic, learning to live well into anaerobic and recover is a learned trait.