Hot weather training – smart or crazy?

Woman performing hot weather training

By Paul Clifford

Let’s talk hot weather training. How hot does it need to get to before you so no to exercise? 27, 30, 35 degrees? Why do you say no at your limit? Is it that you don’t like getting that hot because it’s too uncomfortable?  Is it because training is just too hard at that temperature? Or is it because you feel it is unsafe and you’ll do some damage to yourself?

People have different tolerances for hot weather training.  With records continually being broken in Australia for hot days, the question about how safe hot weather training is will become more relevant.

In reading a number of research papers on the topic of hot weather training there seems to be consensus that there is no one recommended environmental temperature limit for safe hot weather training.  What you need to concern yourself with is your own core body temperature.  37 degrees Celcius is the accepted average normal core body temperature of a healthy resting adult.  Once your core body temperature gets to about 40 degrees Celcius during exercise that is probably going to be your limit.  This limit of 40 degrees Celcius (104 degrees Fahrenheit) was found consistently in a study by González-Alonso et al 1999.

Now you might be saying to yourself “I won’t know what my core body temperature is” and that is almost certainly going to be the case.  Fortunately for us, the research says our body anticipates rises in core body temperature and starts giving us some warning signs.  Importantly this includes the body slowing us down.  Tucker et al 2004 found this to be the case.  Tucker’s study found that in hotter conditions cyclists in a 20k time trial went slower from the start than fellow cyclists in a slightly cooler time trial.  It appears that the brain paces us in order to keep us within an acceptable core temperature range.

So the moral of the story, to keep yourself safe when hot weather training, you must listen to your body.  If your body is saying “no worries champ” – in other words you are not feeling light headed or sick or that it’s a real struggle to push on, even though its 33 degrees outside, then you may well be ok to continue.  The research says that you are unlikely to suddenly end up with heat exhaustion or heat stroke.  That will usually only happen if you stubbornly refuse to listen to the body’s warning signals and in rare circumstances where the body’s temperature regulation system fails.

So here are a few things you can do when hot weather training to look after yourself.  Of course these are tips in the event that you decide you want/need to train in the heat.  An obvious alternative would be to train in early morning or evening when it has cooled down:

  1.  Lower your expectations on performance.  You need to accept that in hot weather your exercise performance will suffer.  As an example, when running you are going to have to expect slower times.  Click on the temperature calculator to see how much slower you are likely to be depending on your normal pace and the temperature.  A word of caution for many regarding temperature readings above 90 degrees Fahrenheit (32 degrees Celcius).  I would anticipate that for many the figures stated for 95 and 100 Fahrenheit underrate the likely impairment.  Be ready for much slower times and at these temperatures, listen closely to your body and be ready to pull out as soon as warning signs appear.
  2. Consider pre-cooling – you can delay your core temperature reaching its limit prior to exercise by cooling yourself with an ice vest, cold air, water immersion or by wearing an ice towel.  The ice vest is probably best as it will cool more of your body and if you are performing in an event, you can wear it right up until race time.  Although there are limited studies done looking at the effects of pre-cooling on training performance, there are a small number of studies indicating that pre-cooling allows athletes to perform longer before reaching core temperature limit and improves performance rates in cycling and running.
  3. Acclimatize to the heat – if you are serious about getting better at running in hot weather then you need to practice running in the heat.  Obviously run within your limits, but as you do it more you will become more accustomed to it.   Studies have shown athletes improve their performance by 7% as a result of training in the heat.  The downside is that true acclimatisation may take 5-10 days and require 60 minutes of exposure on each occasion.  This is likely to be impractical for a lot of people and a strategy only the really serious would bother with.    
  4. Limit your warm up – when it’s hotter you may not have to warm up as much.  I remember doing a significant number of laps of the athletic track prior to a race when I was younger and my teacher thought I was crazy.  “You’ll wear yourself out” he said.  In fact what I was doing was warming myself up as it was reasonably cool weather and I didn’t want to waste the first few kilometres of the race warming up.  However, when it’s hotter it is likely that an involved warm up routine is unnecessary.  If it’s hot, doing several laps pre-run may simply elevate your core temperature and end the run prematurely.  A few stretches and focusing on keeping cool pre-run may be enough.

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  1. DannyBryant says:

    I ran last week in 35 degree heat. It was supposed to be an ‘easy’ 8k run in my program but I found it very tough, due to the heat. Basically, I had no energy. This week I ran the same run but at 7am. It was still humid but only 17 degrees. I found it to be a lot more enjoyable, although I was surprised that I only ran 3 seconds per km faster than last week. I suppose that proves your point that it more to do with body temperature than simply outside temperature. Of course, there are a lot of variables to account for. Since I ran so early in the morning, it took me a little while to get going and I didn’t eat before the run this week. Next time I’ll take a cold shower before my run and see how that goes. Thanks for your article it certainly is a worthwhile consideration when you’re trying to do some running this time of year.

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