How hot is too hot for running?

What about in a gym on a treadmill or indoor track?

I dislike the heat, but living in NE it doesn't get as hot as it is where you are. How'd it go?

 Was going to put my two sense in, but Lauren stole my thunder.... couldn't have said it better myself.. (yes that's a compliment Lauren

1. At 8:30 it starts cooling off considerably. Bring water or sports drink (duh-if we have to tell you this you have other issues to deal with) and walk if you get dizzy.

2. Yes.

I do most of my running in the late afternoon heat here in FL.  If I'm going more than 3 miles, I'll usually take a water bottle along with me.  I watch my HR very closely and slow down or walk if I start to get overheated.  I always wear a hat.  I usually don't take my cell phone with me, but I do wear my ID bracelet all the time, just in case.

Mark

I've got a 2.5 hr run this afternoon and they are calling for upper 90's with 101 Heat Index.  I'm going to run on a trail (for shade), run with a fuel belt and refill it every chance I get.

Just don't do dumb and it's generally ok.  Listen to your body.  There is a difference between, this hurts and this is bad for me.  Finding that line is the fun part.  :P

Damn.  I'm sitting in my air-conditioned office, and apparently I'm pushing too hard. 

Just for the record, you won't stop sweating from exertional heat stroke. That only happens in non-exertional heat stroke (little old ladies that live alone and have no air conditioning....).

You are more prone to heat injury when humidity is high because your evaporative cooling ability is taken away. Basically you are insulated by a layer of warm sweat on your skin. We likely all have some degree of heat exhaustion during hot training days. Our core temps go up, we dehydrate to some degree. Heat stroke is actually a diagnosis of exclusion, it get's ruled out or ruled in when you are in the hospital and they determine whether you have rhabdomyolysis (muscle breakdown) or end-organ damage (kidneys get clogged up when they are unable to clear the enzymes released from tissue destruction). 

Over my time in the Ranger Regiment we had dozens and dozens of very strong healthy guys who's core temp would go up over 108 degrees, the highest I saw was 112 degrees. All occured during high humidity, usually on a standard 5 mile run at 8:00/mile pace. We conducted some extensive studies, including having 50 guys swallowing a capsule with a temperature sensor that could be scanned at mile points along the run. Average temp at the end of the run was around 102 degrees, with a few as high as 104. Probably the guys that go off the charts are either predisposed to heat intolerance, dehydrated, or taking meds (caffeine and ephedra were the usual suspects...).

Bottom line is to acclimate and pay attention to your body. Hydrate during the day leading up to your run. Avoid caffiene in excess. I personally enjoy running in the heat.

Yeah, it's the weirdest sensation too.  You know you're hot.  But at the same time, you feel chilled.  I was about 3/4 mile into the run portion at my race on Sunday.  That's when I knew I was in trouble and that I had to take it very easy and just stay focused on taking care of myself and stop worrying about my time. I spent several minutes under the tent at the next aid station, alternating drinking cold water and pouring it over my head.

And I WAS well hydrated.  I had at least 1 liter of sports drink in the hour or so before the race, and 1+ liter of sports drink on the bike.  It was just too darn hot.