Often wondered about this myself.

From personal - not scientific data - I think that extreme heat just wears you out. I don't find any benefit - unless you call heat exhaustion a benefit.


EDIT: I'm interpreting your post to mean extreme heat - like going for a long run mid-afternoon. I think it's beneficial to train outside to acclimate to the heat, but not under extreme, sweltering afternoon conditions. I think you can do more harm than good in extreme weather.

Is what you're asking:

(high temps, high HR, low pace) = (low temps, low HR, high pace)

?

I would say no. A lower pace in the heat is only traning your body to deal with additional stress caused by high temperatures. As far as the aorbic systems you are trying to train in your muscles, well, they are not being worked to the capcity (pace) they are used to or capable of.

In the heat, the muscles are forced to try to do more with less as blood (O2) is diverted to the skin in order to flush out the additional heat.

Of course with consistant training, the body adapts to the higher temperature and after a time the efficiency of your internal air conditioner becomes less of a factor.

This is my amatuer opinion anyway.

I think it is a good idea to do some heat workouts if you are planning on racing in the heat. Also, it is probably better to to a heat workout than to skip a workout because of the heat.

My first inclination is "no." Consider that HR is merely an indicator of effort. Since heat also affects HR, you'll have a higher HR in the heat than in cooler weather at the same effort level. The effort determines fitness goal. The HR zone is just a way to guesstimate that effort. So, if you're targeting say, a tempo run in the heat and you rely on HR data only (as opposed to RPE), and if your HR zones are set up according to tests in cooler, drier weather, you may not get yourself up to the proper effort level.

EDIT

Keep in mind that I'm no scientist, and haven't been at this game that long. Also, a benefit you will gain from training in the heat is to see how your body reacts to it.

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Steve Perkins

I personally think workouts in the heat get you acclimated to it. If you are in a race in the heat and there is someone from Texas racing against someone from Maine, I think the person from Texas should do a lot better. At the beginning of the hot season in Texas, my first few workouts are crappy, but after a few weeks they aren't so crappy. You have to be careful of heat exhaustion and dehydration, but if you are careful, I think you can get some benefit from them.

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Another portion of the question is, what amount of percieved effort is dictated by the heat.

Obviously running at equal PE's, one in the heat one in the cool weather, results in different pace. Also obviously at equal PE's HR is higher in the hotter weather.

My personal uneducated completely wild @ss guess is that one is "undertraining" some portions of the system, particularly muscular, but overtraining other portions.

I have no idea if this is equally beneficial or a waste of time.

Certainly some workout is better than nothing, but if the purpose is to "extend" the limits, such as long run, speed etc I question if that is possible to do in extreme conditions as something other than current fitness is the limiting factor.

As other have mentioned if "heat acclimation" is the goal than you're definately doing that.

~Matt

 
This is completly non-scientific but I live, train and race in the heat of South Florida. When my father in-law comes down from Chicago for races the heat just eats him up, decimates him. When I go up there for visits and do training runs in milder weather, my run times compared to heart rate are fairly similar to those down here. My RPE is a bit lower but not dramatically so.

Still, I'd be curious to know what the data on physiological advantages/disadvantages of training in the heat is, other than just acclimitization..