Heat acclimation

It’s summer, and that means dealing with the heat.  When it comes to avoiding the heat, runners have it easy compared to triathletes.  Races can be started early in the morning, and longer races (like marathons) tend to be held in the spring or fall and not in the hottest months of the year.

Because of a little thing called “the swim,” however, triathlons, are typically held in those hot months to ensure that the bodies of open water are not too cold to swim in.  Additionally, triathlons are typically longer than running events with the sprints lasting from 1-1.5 hours (compared to a 5k which will typically last between 20-30 minutes).  Because the run is at the end of the triathlon, triathletes typically run later in the day than runners.  The end result is that when triathletes are competing in the run, it tends to be quite a bit warmer than when runners are competing in running races of similar distances.

One of the first things I did when it started heating up in Salt Lake City was look up the historical average high temperature in Coeur d’Alene on August 21st.  The average was 83° which was better than I was expecting, but, of course, that’s only the average.  It could be much higher.  Last year, it was well over 100° in June.

Because I know I’m likely going to be running a marathon in over 80°, I know I need to get used to running in the heat.  So I’ve been doing my best to embrace afternoon workouts.  Specifically, I’ve been trying to do runs in the afternoon instead of carefully crafting my schedule to avoid all evening runs (which I’ve definitely done in the past).  We’ve been going through a hot spell in Salt Lake City, so I’ve had some runs in the upper 80s and one in the upper 90s so far.  In addition to my runs, I’ve been cycling in some warm weather as well.  That just doesn’t stand out as much because cycling in the heat is much more pleasant than running in the heat.

It’s been hot here…

Really, all I knew about heat acclimation was “Run in heat.  Get used to heat.”  So I wanted to do a little research and learn more about it (in other words, make sure I’m doing it right).  It turns out that “Run in heat.  Get used to heat” covers the basics pretty well.  However, I found some interesting more scientific explanations and advice in this article: Consensus recommendations on training and competing in the heat

Essentially, when you exercise in the heat, your body adapts, and its cooling mechanisms become more efficient.  Your body becomes more efficient at sweating (in other words, you learn to sweat more).   The blood flow to your skin increases which allows your body to release more heat (basically, your hot blood gets pumped to your skin where it can lose some of its heat).  You begin to maintain a more efficient fluid-to-electrolyte balance.  All these things help you perform better in the heat.  Of course, when I’ve been acclimating to the heat, I haven’t noticed any of these adaptations particularly (except maybe the sweat one…), but I have noticed that I feel more comfortable in the heat than I did three weeks ago, and it doesn’t sap my energy to step outside like it did when the temperature first spiked.

I was surprised when I read just how quickly heat acclimation happens.  Athletes can gain benefits of heat acclimation within six days, and it usually only takes a few weeks of daily exposure to reap the full benefits.  While this theoretically means I could avoid afternoon runs for another few weeks, I’d rather play it on the safe side.  I’m not exercising in the heat every single day, and adaptation doesn’t occur as quickly when you are not out in the heat each day.

Really, heat acclimation is pretty simple.  Is it hot outside?  Then go for a run/bike ride/whatever!  While the article I read specifically lists certain durations, frequencies, and intensities of the workouts in certain studies on heat acclimation, it also stated clearly that continuing your regular exercise regimen (but in the heat) is an effective way to acclimate to hot weather.  Ultimately, the effectiveness of heat acclimation depends on how often you exercise in the heat, how long your sessions are, and how intense the workouts are.  Personally, I’ve been electing to limit my hot runs to short-to-medium length runs of moderate intensity.  I do longer and more intense bike rides in the heat.  It’s a little more complicated if you are training for a competition in a climate that is much hotter than the climate in which you are training.  However, if you find yourself in this position, creating hot conditions indoors can serve as a reasonable substitute for exercising in the heat outdoors.

One important point to keep in mind as you begin acclimating to the heat is hydration.  You will be sweating more.  You will need more water.  Strangely, there isn’t a consensus as to when dehydration while exercising starts to affect your performance.  The studies don’t agree.  Some say that losing as little as 2% of your body weight in water is enough to limit your performance.  Others have found that losing up to 4% of your body weight in water still doesn’t negatively affect performance.  However, regardless of exactly how much water you consume while exercising (whether that be “some” or “a lot”), it’s important to start your exercise fully hydrated.  So drink during the day.  Drink water with your meals.  Make sure that you are hydrated going into your hot workouts because that’s probably more effective than trying to reach a fully hydrated state during your hot workouts.

I’m not an expert on heat acclimation, of course.  I’ve been working on acclimating myself and I’ve done some reading on the topic.  If you’d like to read more, I’d suggest starting with the article I posted earlier.  It’s peer-reviewed and discusses a lot of the current research on the topic and covers some of the controversy and disagreement among researchers as well.  Although many of the studies it references are not free online, some are and others have a free abstract online.

(Also, just an extra pro-tip: If you really want to get used to suffering in hot weather, just get a really old car without a working AC and drive home for thirty minutes every day in 90° weather.  Suddenly, 80° will feel refreshing!)




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