Extreme Hydration Issues

Since 2001, over 90,000 cyclist's have joined Cycling Forums to discuss topics from general cycling to equipment, training, racing and travel or vacation destinations (especially in europe during the tour de france). We also feature an great deals in our online store, 100's of articles, classifieds and product reviews.

I've had two MTB races this year which I've had to pull out of from dehydration. Frankly, I could sweat for Britain! But in race conditions, with a high HR over many hours (4-6), I just cannot keep the fluids.

I'm starting to think that I should enter 50-60k races instead of 100k events.

Has anyone else got this problem?

Also, base level advice regarding hydration has already been taken, I drink loads, I supplement with electrolytes, it's just that I sweat at a rate which is simply not normal.