Skyline_Dougie

I rode 85 miles of a century in 108F temperatures this last weekend in Texas. The 15 miles we were short was due to being lost and because we can't read a map or que sheet.

Anyhow, nearly 1/3 of the riders needed to SAG back due to the heat.

Q: Was it the heat or the effect of the heat and lack of hydration? As for myself, at about 65 miles into the 85, I began NOT to sweat. I was drinking plenty of water, and had plenty of gel. I thought I was getting the electrolytes and all else I needed, but it just did not seem to work out for me. I finished, but I was beat. Did I get myself dehydrated? Do I need a better sports drink besides water and an occasional Gatorade? Who uses what and when?

Thanks, and I'll be sure to share this with the others that deffinitely took it too far on a hot day.

Hot in Texas

supcom

If you stopped sweating at mile 65 you would not make it the last 20 miles. Failure to perspire in the heat is a sign of heat stroke and is a critical condition requiring immediate treatment. More likely, the sweat was evaporating as fast as it was produced so you did not feel wet. At 108 deg, the humidity must have been very low.

bbattle

NEVER a good sign to stop sweating. That's when your body just gives up trying to cool you down. You can fry your brain. Always drink lots of water on a ride. I drink water pretty steadily a hour or so before a ride, steadily during a ride, and plenty of water after a ride. And that's just for 30 mile afternoon jaunts in only 90 deg. heat.

I generally carry two bottles, one with water and another with a sports mix that has electrolytes and carbs. Before I run out I'm looking to top them off with more water.

It's not a macho thing to do without water; you can really mess yourself up.


In East and Central Texas, it's still plenty humid at 108 deg. Just like Alabama, though it doesn't get quite that hot here.

sch

Your gut can't handle more than 750-900ml of fluid per hour, and if drinking water only or very sweet fluids (or eating a lot and drinking water) then the max throughput of the gut is even less. **ade is formulated to hit the range of sugar/electrolyte concentration that maximizes throughput of fluids. What happens to fluid in excess of this amount? It stays in your stomach. Which is why you feel bloated and not as thirsty after awhile. On the output side your sweat glands can easily exceed this amount of sweat under hot humid conditions. Combined with increased respiratory loss secondary to heavy breathing and some urine output at least for a while the imbalance can get to be pretty significant by 60-80miles in the conditions you describe. IOW, given the conditions it takes an unusual physiology to go 100miles and not collapse. Prehydration hours in advance can help but also tends to fill the bladder. Drinking a lot in the first few hours when most people tend not to helps.
Acclimation helps but takes about two weeks and requires lots of daily hours in 95F +
and high humidity-not something most of us do in our air conditioned lives. Water only can be dilutional in these conditions and extra sodium/salt is essential. The marathoners that got hyponatremic were mostly slow runners spending 5-8hrs on the course and drinking lots of water. They also probably had some physiologic maladaptions as well since relatively few of the runners had the problem.
Steve

DannoXYZ 

"I was drinking plenty of water, and had plenty of gel."

The "plenty" part is a subjective judgement. What's plenty for you may be completely different from someone else's definition. What was the EXACT amount of water you drank? And during what time-frame?

I've done a lot of 100+ degrees-F rides in Vegas. The dry desert heat really dehydrates you quickly. I've found that I definitely needed salt-tabs along with my energy drinks. Also went through 3 full 20-oz bottles of water per hour! So for your 85-mile ride, I'm guessing you'd need at least 15 20-oz bottles of water. By your 65-mile mark, you should have consumed at least 12 20-oz bottles. If you had less, then you were definitely not drinking enough. Also the cessation of sweating is a sure sign of impending heat-exhaustion. Continuing after that will lead to heat-stroke which can be lethal.

Don't wait until you're thirsty, drink lots and early.