by Heba Hosny in Training Tips, image by Vincent van der Pas

Advice about running in high humidity climates

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Running in hot and/or humid weather is not recommended unless you really have to. This is because such conditions can take its toll on your bodily functions, especially your heart rate (HR). We always stress on the importance of proper hydration in general but when it’s hot and humid, sufficient hydration is out of the question.

In this article, we will discuss how to cope with the two dreadful H’s – hot &humid – when it comes to hydration and heart rate.

Proper hydration requirements for the hot/humid run

Many runners fall into the trap of believing that they are adequately hydrated while in fact, they are not! So let’s learn some hydration basics and a specific ways to measure your ideal hydration rate.

Basic Hydration Tips

  • If you know ahead that you will be running in a hot/humid weather, drink a lot, and I mean A LOT, the day before
  • Don’t limit your hydration to water. Go for soda and other fluids
  • Also remember that you can get some of your hydration needs through eating water-rich fruits and veggies, such as cucumber, watermelon, plums , and lettuce to name just a few
  • Studies have shown that warm water is slower to absorb compared to cold water. For your hot/humid run, your best bet is to add ice to your fluids while running to ensure better absorption
  • Your choice of hydration fluids should be very personal since runners vary in their stomach reaction to some liquids. For example, some runners would favor Gatorade over water, while others could vomit if they take it. It is best to experiment with liquids and find out which ones suit you best before your big hot and humid day!
  • Also remember that clear urine reflects adequate hydration

How to determine your hydration needs?

There is a very simple method to help you calculate your exact fluid loss during a run. This amount represents your optimal anti-hydration fluid requirements. For best results, make sure to follow these steps on a regular training routine.

  1. Weigh naked before the run
  2. Track your fluid consumption throughout the run
  3. Weigh naked after the run. (Make sure you are completely naked because weighing clothed will give inaccurate result results due to sweat absorption)
  4. Apply the following formula:
    • Post-run Weight – pre-run Weight + fluid Consumed = total lost fluid
    • Divide the total lost fluid by the number of miles you ran
  5. The result will represent your needed fluid consumption rate per mile

Due to the unquestionable importance of hydration, we have dedicated an entire post for proper hydration tips. Enjoy!

Effects of hot and humid runs on your heart rate (HR)

Here are the some statistics that show the impact of the hot and humid weather on your HR:

Humidity impact on your heart rate

Your HR is likely to increase up to 10 beats per minute in humidity levels ranging from 50% to 90%

Heat impact on heart rate

  • Your HR is likely to increase by 2 to 4 beats per minute in temperatures from 60°F to 75°F
  • Your HR is likely to increase up to 10 beats per minute in temperatures from 75°F to 90°F

Here is an example of how the HR of a woman in her 30s will be affected by a hot and humid run, assuming that her typical running HR under Moderate Conditions (60°F heat and 30% humidity) is 145 beats per minute.

If her running temperature was 90°F, then her HR will increase +10
If her running humidity was 70%, then her HR will increase +10
Total HR rate will become 165 beats per minute

The problem with a 165 HR is that it’s almost 90% close to the allowable HR threshold. In other words, if you run under these conditions you will be so close to the high-risk zone because you exert a lot of physical effort that you wouldn’t be able to sustain without dangerous side effects.

So to work around this issue, you must minimize your hot/humid runtime and if you are an avid runner who lives in the hot/humid environment, perhaps becoming an early morning runner would do the trick. Good luck!




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