Heat Acclimation for Runners


I’m saddened to report that it is STILL in the 90s in North Carolina.  And not much better in Virginia, where I’ll be moving in just a few weeks.  Someday, maybe I’ll live in a place where it’s 70 degrees year round, but for now I’ll just have to daydream about being able to breathe when I run….and get my body acclimated to the temps I actually live in.

Depending on where you live, summer might be the best time for running (….Canada? Maine?), or it could be the worst (hello, southeast!).  But your fall races aren’t going to run themselves, so running in the heat is, for most of us, unavoidable.  Here’s the key: in order to succeed with running in the heat, you must first allow your body to ACCLIMATE, or become accustomed to it. Below, I’ve laid out a generalized plan for how to better manage the heat within 2-3 weeks.

First:  you can (kind of) avoid having to acclimate altogether by shifting the timing of your runs.  If you’re typically a morning person, try waking up a little earlier to get out while it’s still cool.  If you already run before heading off to work or school, this is going to be the easiest option for you – you may not need to change your schedule at all.  If you typically run in the evening, 5pm is going to be pretty brutal.  Maybe try waiting till 8pm, once the sun is a little lower.  Can’t switch your schedule?  Try bringing some of your runs indoors.  This is the least optimal choice, especially if you’re training for a road race (remember the specificity principle!), but it’s better than chancing a dangerous heat index (see last week’s article on heat illness for more guidance on when to take it indoors).  

Is exercising in the heat unavoidable?  There are steps you can take to make it safer and easier. This process – adapting to the higher temps and humidity – usually takes at least two weeks, and can take longer depending on just how hot it is outside and how different the temperature is from, say, your spring runs. If you are overweight or older, heat acclimation will take you longer than two weeks.

Step 1: cut your volume and intensity.  Start small – whatever distance and speed you can handle while keeping your RPE within a notch or two of where it usually is while you run. Your pace may be slower – for example, you may find that on a clear, brisk spring day you can run an 8:00 minute mile at an RPE of 7, but once the temperature and humidity climb, your running 8:45 pace at that same RPE of 7.  With heat acclimitization, it’s best to use RPE as your training guideline – it’s a much more accurate measure of how hard your body is working than your pace is!


Step 2:  Add distance.  Over the course of a week or two, increase the distance of your daily runs by about 25% per week.  Again, your RPE should be within 1-2 points of where it is normally. It’s safest to keep your runs on the easy side in terms of pace until your mileage is back where it typically is.

Step 3: Once you are back at your typical mileage, you can start pushing the pace back to where it normally is.  At this point, your body will be more accustomed to the heat and your risk of heat related illness is reduced.  However, increasing the pace may still feel a little harder than it usually does – that’s okay. It’s going to take more than two weeks for runs in the heat to feel effortless. Again, time of day can come in handy here. If you have speed work on the schedule, it might be best to get this done early in the morning or late in the evening when it’s cooler.  You’ll be able to hit your goal times with less effort.

Again, that’s a pretty conservative acclimatization plan – depending on the temperature and how you feel, you may be able to work through this faster, or you may need more time. It’s not scientific, but I find that in general people have an easier time acclimating to heat when they live in regions that typically experience these temps.  Let’s say you’re traveling to Georgia for the Peach Tree Road Race.  You’re going to have a much easier time running in the heat if you’re from North Carolina than if you’re flying down from Maine. Regardless, it always helps to:

-Make sure you have access to water and electrolytes before, during, and after training

-Find shade whenever possible

-Make sure to give yourself an extra 10-15 minutes to cool down (walk) at the end of your workout

-If you CAN jump in a pool/stream/lake afterward – do it!

If you find yourself struggling to acclimate to the heat, or you begin to experience symptoms of heat illness, please consult a licensed healthcare provider in your area.

Summer is my least favorite season for outdoor training precisely because of the heat – but with targeted focus to your training and a large amount of patience, you can make it work.  Just think of how good that November race is going to feel!

Happy running!

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