I was a personal trainer for 7 years and have a B.S. in Exercise Physiology as well as a level 1 certification from ACE (American Council on Exercise). You will hear a lot of different opinions and the only constant with any of it is everyone is different.

So here is a starting place. This really works for me. I live in Kansas City, MO where we have very hot and humid summers so hydration while out training is very crucial. I aim for 30-40 oz. of liquid per hour. My drink of choice is Hammer Nutritions HEED. It contains plenty of calories, sodium chloride, potassium, and NO simple sugars (easier on the stomach). 2/3 of the 30-40 oz. is HEED the other 1/3 is water.

I have read and experienced for myself that more than 40 oz. per hour is too much. Your stomach just doesn't empty that fast and you end up with that sloshy feeling.

One more thing, if it's that hot slow down. Conserve your water and your energy. You can not replace it as fast as you lose it.

Hope this helps a little bit.

Hydration is crucial my good friend during trainning or racing in any given endurance sport.
The impact of fluid and electrolyte deficit can really make the difference of finishing strong s given race or become part of the DNF list. Besides the effort that our body sustains is big...particulary over our kidneys...so to keep them working, fluid intake is crucial.
Remember the phrase of: "What works for athlete A might not work for athlete B"...but reading and learning the basics is important to star putting together your our personal hydration strategy and formula
Here in this very site there is a couple of piece to read about that are really easy to grasp, and to put in practice:

http://www.trifuel.com/triathlon/nutrition/tri-to-drink-001409.php
http://www.trifuel.com/triathlon/nutrition/hydration-top-5-mistakes-000701.php
http://www.trifuel.com/triathlon/nutrition/hydration-strategy-000870.php

Those three are pretty good...also you can get your hands on some calculators for hydration they are of good help after you learn to use them...they are pretty easy to use. There is one at the Powerbar site, and in Runners World site too...
Hope this helps my friend and best of luck!

Thanks UltraRunner,

Here is what I did. I was drinking a waterbottle every ten miles, avg like 19.5 mph on bike (so right around 20 oz every 1/2 hour). It was about 1/2 gatorade 1/2 water. I had a HR monitor and was avg. around 150-155, my anaerobic is 168. I hit about mile 70 and took a bathroom break, it was very concentrated. Took in some more water. Mile 80 felt good but started to slow down. Then mile 90 came and started to feel dizzy so I got off. That's when I threw up. I couldn't hold anything down for the next 2 hours.

I actually live in the town where hammer nutrition is at. I ran a 1/2 IM before and used perpetuem. It didn't sit well in my stomach at all. Gatorade seem to work fine on my long rides, but it was never that hot. I completely understand all our bodies are different. I'm just not sure if I was taking in enough or what. My muscles definetly felt fine, but maybe I was still pushing to much. I have a couple more 1/2 IM this summer, do you think I should switch my nutrition plan or just stick with it and wait until next year.

Thanks, Brian

Sounds like to me that you got dehydrated and your body overheated. Been there. We have to remember that the more water we lose the lower our blood volume gets which makes it harder for the heart to pump. So your HR increases. In addition, we are forced to slow down in hot environments because the blood is sent to the surface to cool it so that the body cools down.

As for what to do for the rest of the season...I would keep it simple, i.e. Gatorade and water with some gels for calorie replacement. One of the main rules of race day is NOTHING NEW! If you don't have time to train with it don't race with it.

One more note. Start hydrating 3 days prior to your event. I aim for 1 to 1.5 gallons of water each day leading up to the event. Yes, you will be in the bathroom a lot. But it pays off on race day.

I hope some of this helps. Best of luck to you in your races!

Brian,

I don't weigh myself before and after workouts much anymore, but that was how I found out that my rate of fluid loss was higher than normal. I just used the scale at the gym.

I don't think it's possible to replace all fluid lost while competing. Even at 52 oz an hour, I'm taking in less than I'm losing in high heat. I think the best you can do is flatten the curve, you can't reverse it.

As I noted above, for those of us who obviously sweat more than most, I think the most important action you can take is to experiment (in training) with how much fluid intake you can tolerate. Don't accept the conventional wisdom, as it may ot apply to you. Unfortunately, as you push the edge of that envelope, you're going to experience some discomfort...as I have learned first hand! I never actually vomited, but I came close (when I discovered that even MY cast iron stomach cannot tolerate 78 oz an hour on the bike!!!!)

Also, don't forget that, as the volume of fluid loss and intake rises, the importance of maintaining appropriate electrolyte levels becomes ever more important.