Woman Running

Exercising In The Heat: What You Need to Know

Since we’re just about halfway through the hot and sweaty summer season…

There’s a good chance you’ve attended some family BBQ’s, trips to the lake or beach, or any of the other fun activities that we typically enjoy this time of year.

And with all of that fun, the need to consider factors such as water intake and dehydration becomes even more important...

Not only for feeling and performing your best, but also for your health. Plus, if you have any goals for fat loss or gaining lean muscle ... your ability to stay hydrated this summer will play a crucial role in both!

See, here in the good ol' Midwest (and many other areas across the country), temperatures and humidity levels will be at their peak, making it more and more difficult for the body to cool itself.

The body cools itself by sweating, and during this process, water is lost from the body.

Surprising amounts of water can be lost and it has been reported that the average person can lose around 1.5 to 1.7 liters of fluid every hour during exercise (REF)... which is 50 ounces! 

When water loss reaches 1% of the person’s body mass (approximately one 20 ounce bottle of water for a 170 pound athlete) many aspects of performance begin to deteriorate and this downward spiral increases as the amount of dehydration increases (REF).

The more dehydrated you become, the more your performance and health is impacted.

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A key factor that many athletes do not fully appreciate is the fact that it is nearly impossible for you to drink enough during exercise to adequately hydrate yourself while you continue to exercise in the heat.

The best way to counteract the loss of body fluid is to regularly consume fluid before, during, and after exercise.

The problem here is simply that the stomach has a difficult time absorbing and releasing enough fluid to allow for rehydration to occur (REF).

In other words, once you develop dehydration to any extent, it is very hard to reverse its negative effects without stopping altogether.

If you're out playing a friendly game of soccer or shooting hoops, this is no big deal. However, if you are competing in a tournament or running a race or triathlon, this can have a big-time negative impact on how you will end up performing.

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A negative impact on your performance is one problem, but other very serious problems can also occur to your overall health.

Make no mistake about it, exercising in extreme heat and humidity needs to be taken seriously.

It's tragic, but each summer you read media reports of high school or college-aged athletes succumbing and sometimes tragically losing their lives to heat injuries caused by extreme summer temperatures.

So once again... dehydration is a serious matter that you should be aware of and take steps every day to fight against. Do it for your health, performance, and safety, if nothing else.

Below is a quick summary of the things you need to consider to make sure you can enjoy outdoor exercise:

• Clothing: This is a major consideration and all clothing, if possible, should be lightly-colored, allow for rapid evaporation against the skin, and have good ventilation.

This is easy for runners and cyclists but can be a distinct problem for athletes whose sport requires them to wear a uniform with protective padding.

Hydration Sticks

• Hydrate, hydrate, hydrate: When you know it is going to be hot and humid, you need to take significant strides to make sure you're consuming plenty of water. 

Some guidelines include drinking large amounts of fluids the day before, whether it’s plain water or electrolyte drinks, and to choose foods with high water content such as fresh fruits and vegetables.

Your urine should be clear, and there should be lots of it (see below for more on this).

• Electrolytes: these are essential minerals that are vital for many main functions inside the body. Your body cannot naturally produce them on its own, which is why you need to get them through food or electrolyte drinks. The main electrolytes are sodium, calcium, potassium, chloride, magnesium ... all of which are key factors in proper fluid balance and hydration.

• Within 30 minutes of starting exercise, you should drink 1.5 to 2 cups of water or sports drink, and then during exercise you should strive to drink 1.5 to 2 cups of fluid or sports drink every 15 to 20 minutes resulting in an hourly consumption of around 4.5 to 8 cups of water or sports drink. Try to spread it out though, to help prevent too much fluid from hitting your belly at once.

• Have an idea of how much weight you lost during the exercise session and drink two cups of fluid for every pound you lose.

If you do not know how much weight you lost, then drink liberally until your urine changes from a darker yellow or gold to a pale yellow or clear appearance.

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• Urine Color: As mentioned previously, monitoring your urine color can be used as a guide for how hydrated you are.  When you are well-hydrated, you will produce more urine and its color will be light-yellow or clear.

As dehydration progresses, the color of your urine will transition from a definite yellow to a darker yellow to a gold or orange to brown; the darker your urine becomes, the less of it you will produce.  Always strive to keep your urine as clear as possible.

• Acclimate: It is important to understand that working inside an office with controlled temperature and humidity does not challenge the body much regarding cooling itself.

Therefore, when you change into your workout clothes to go exercise in the middle of the day when temperatures and humidity are elevated, this presents a significant challenge to cool your body.

Try to give your body a chance to acclimate to the more challenging conditions by getting outside regularly and exercising during the times when you plan to compete.

• Warning Signs: Heat injuries can happen to everyone.  Certainly, symptoms such as feeling extremely hot, dizzy, and disoriented are worth mentioning, but if anyone begins to lose their feet or their lunch ... it is time for them to stop whether they want to or not.

• Rapid Cooling: What do you do if you or a friend did overdo it?

First, stop what you are doing and get into an air-conditioned building ... or if outside, a shady area by a building or under a tree.

If you can manage to get into a cool, shaded place with a little air movement, that is even better.  If possible, drink cold water or sports drinks until you begin to feel better.  Do not return to exercising.

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If the person has unfortunately experienced some bout of weakness, passing out, nausea, or gets sick ... these are signs for more aggressive cooling.

The best bet is to have them get into a cold water bath up to their neck.

These are not always available, so making ice packs from a cooler or soaking cold towels in an ice bath and placing them on the person’s neck, groin and armpits can help to cool the body.

These steps should be taken immediately and this may even be a situation to call for medical help.

While higher temperatures and humidity levels can challenge the body’s ability to cool itself, taking a few extra precautions and paying attention to how you are feeling in combination with some common sense can help to prevent significant problems related to the heat.

Once again, the point of this blog is to help you enjoy your outdoor summer activities and workouts...

While being a reminder to hydrate throughout the day, during your activity in the sun, and after as well.

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  4. Sawka, M. N., S. N. Cheuvront, et al. (2005). “Human water needs.” Nutr Rev 63(6 Pt 2): S30-39.
  5. Speedy, D. B., T. D. Noakes, et al. (2001). “Fluid balance during and after an ironman triathlon.” Clin J Sport Med 11(1): 44-50.