Upon exposure to heat on a regular basis during exercise, the human body makes a number of changes that allow for greater aerobic performance (duration or intensity) in heat. Most studies have observed significant changes in sweat rate and composition as well as performance when athletes complete workouts for 60 to 90 minutes in moderate heat (heat index 80 - 95F) at least every other day during an acclimation period lasting two to three weeks. Acclimation can be maintained by completion of one or two warmer weather (midday) workouts per week. Fluid and salt intakes should be such that they replace the bulk of water and sodium lost via sweat during any exercise. Athletes should estimate their sweat rates on a regular basis in a variety of conditions (temperature, humidity, wind) as the rate will change as they become acclimated to heat.---via UltraRUNNING OnlineThe human body is an amazing machine, folks. The sooner you start to treat yours as a well oiled machine, and less as a garbage disposal, the sooner you will be able to appreciate what it is fully capable of.
Last summer was the first time that I noticed the benefits of heat acclimating. I added Cactus Rose (a 50 miler at the end of October in the Hill Country of Texas) to my schedule for the first time, and I knew there was a good chance that it would get very hot before the end of this race. I knew I had to get my body used to functioning in the heat if I would be able to stay strong throughout 50 miles of climbs over rocky terrain, with no tree cover. So, I added in mid day and early afternoon runs to my rotation. I didn't do every run at these times. The rest of my workouts were early mornings when it was still warm, but not scorching. Towards the later part of the summer, I started to notice something. Even though the morning temperatures were the same as they had been all summer, these runs started to almost feel cool! And my mid day runs were tolerable, even though is was every bit as hot, or hotter than it was when I started this process.
Don't get me wrong - my body still reacted the same way to these runs - I would be drenched in sweat by the time I hit the mile mark, but I no longer felt the heat the same way. Even better - my heart rate no longer soared at a lower rate of exertion like it did in the beginning of the summer. My body had adapted to these conditions, and I was a stronger runner because of this.
This is where I am in my training for the Big Butt 50k in July. This race has bad idea written all over it, so the best I can do is prepare myself as much as possible and hope for the best. Most ultras start at 6, or at the latest 7 a.m., since you will be out there for the better part of the day. Of course, since this one is July 28th in Clinton, Mississippi, they have decided to forgo the cooler hours and start the race at 8 a.m., well after the sun has risen. In a strange way, I see this as a further challenge, and all I can think is "Bring it on Big Butt" - Yeah, that is just fun to say.
So today I ran 6 miles, finishing a little after noon. Not sure what time I started - this was a no watch/no GPS kinda day. It sucked. My heart rate was way too high for the amount of effort I was putting out, I got a little nauseous a couple of times, and I had to walk for about 30 seconds at mile 4, and again at mile 5. I also drank approximately 30 oz of water during this run. Once I got home, I mixed my recovery drink and headed out to the picnic table to stretch, where I left a puddle of sweat, then came inside and wrote in my high tech training log, where I left another puddle of sweat.
I am thankful that through experience, I know that this will get easier. But, for now, it kinda bites. :)