Coach Tip Tuesday: Thriving in (Not Just Surviving) the Heat

By the end of July/beginning of August each year, I’ve read a lot of Post-Workout Comments from athletes that mention the heat.  And not only do athletes mention the heat, they complain about it.  (A lot.)  

I get it; training or racing when it’s warm is uncomfortable.  It can and does definitely impact performance and how one feels during a workout.  However, while these things are definitely true, it doesn’t mean that the heat is The Worst.  It is possible to not only train (and race!) in hot conditions, but thrive in them.

How Your Personal HVAC System Works

A majority of the issues that athletes experience in hot conditions come down to thermoregulation, which is the body’s ability to maintain its core temperature.  The body needs to keep its core temperature within a few tenths of degrees of its normal (a normal range is 97.7ºF to 99.5ºF).

When the ambient conditions are hot, our internal body temperature also rises.  In order to combat this and try to maintain that constant core temperature, the body sends blood to our skin to off-load the heat that is rising in the core.  Additionally, the body also sweats and leaves a layer of moisture on the skin that cools us down as it evaporates.

Proper hydration is essential when talking about how to thrive in the heat.  The water in your body is your body’s natural coolant.  When you sweat, your body needs to pull the water needed for sweat from somewhere.  It will default to using your blood plasma (the watery part of your blood), but as blood plasma volume drops, the body will then seek to find that water from other sources (such as the organs, muscles, and other soft tissues) in order to replenish it.

Hydration is so critical because it helps to maintain that all-important blood plasma.  If you send your body into a state where it is pulling water from your soft tissues, you are at risk for extreme medical conditions such as heat stroke, rhabdomyolysis, and more.  

Less important than your overall health, but still significant: Performance decreases with just a 2% dehydration rate.  How much your performance suffers depends on the duration of your activity, the intensity of what you’re doing, and how dehydrated you are, but if you can expect your performance to decrease by 30% if you are 5% dehydrated.  Additionally, your ability to tolerate heat (both subjectively and objectively) decreases dramatically if you are dehydrated.

If you are dehydrated prior to a workout (meaning that you start the workout in a dehydrated state), your performance can be reduced by as much as 45%.  Even if you do start a workout properly hydrated, the stress of being in a hot environment alone is enough to cause a 7% decrease in performance.  So, it’s very, very important for you to be properly hydrated before and during a workout or a race in order for you to perform the best you can in those conditions.

I’ve said it before many times (and I’ll probably say it until I retire from coaching ;) ), but I have observed that hydration is and continues to be the element that athletes undervalue the most.  It impacts everything - your performance, how you feel, how you recover, and how you are able to tolerate subsequent training in your plan.  

Acclimatization Is Key

Acclimating yourself to hot conditions is the only way that exercising in the heat will not feel terrible.  The only way.  I don’t usually deal in absolutes, but this one is true.  If you don’t expose your body to hot conditions consistently over a period of weeks, it will never adapt to be able to function well in them.

It takes approximately two weeks for the body to adapt to hot conditions.  This means two consecutive weeks (without breaks) of exposure to hot conditions in each of your workouts.  It will feel uncomfortable the entire time your body is adapting.  The entire time.  That’s the “bad” news.

The good news is that it is possible for the body to adapt and once it does, you will not only feel better, but you will perform better.  Studies have shown that heat training is at least as beneficial as altitude training (and may actually be more beneficial than altitude training) for performance not only in extreme environments, but in temperate environments.

I’ve written before about how the body acclimatizes to the heat, but it bears repeating now:

When you acclimatize to the heat, two very important changes occur in your body.  The first is that your total blood volume increases.  (Specifically, your plasma and your red blood cell volumes increase.)  This enables your body to improve the blood flow to your skin and muscles as well as keep your heart rate, skin, and body temperatures lower, which enables you to exert yourself more in terms of time and intensity.  The second adaptation is that the composition of your sweat changes so that you lose fewer electrolytes as you sweat (up to 50% fewer!).  This enables your body to retain them and use them for muscle function.

Pre-Hydration & Pre-Cooling

Pre-hydration is a really effective strategy for managing hot conditions.  Consuming sodium-rich liquids such as miso soup or chicken broth the day before a big workout or a hot workout will help get sodium and fluids into your bloodstream where you need them while working out.  

Additionally, maintaining adequate daily hydration (i.e. consuming an appropriate amount of liquids each and every day) will help ensure that you begin your workout or race at your very best, since your body will be ready to properly use its internal cooling system.  A baseline, very generalized target for how much hydration you should consume on a day without any workouts is 50% of your body weight in pounds in fluid ounces.  (For example, if you weigh 180 pounds, you should aim to consume 90 fluid ounces of hydration each day.)  If you have a workout on a particular day, that number should be higher.

Pre-cooling allows you to start a workout or race with a lower core temperature.  Starting with that lower temperature allows you to maintain a lower core temperature for a longer period of time before it rises to the level where you feel fatigued.

You can pre-cool yourself by keeping your core body temperature lower in the 24 hours before a big workout or race.  Pre-cooling techniques include staying in the shade or air conditioning, not getting into saunas, and not doing any activities that drive your heart rate (and therefore your core temperature) up.  You can also submerge yourself in cool water (such as a shower, pool, or bathtub) for 15-20 minutes right before you begin your workout.  Drinking something cold (such as a slushy or otherwise very icy beverage) helps to lower your core temperature and create a heat sink, which means you not only store less heat, but you store it more slowly.  Finally, you can use cool towels on your skin to lower your skin temperature.  Place these in key areas such as your neck, but don’t actually place ice next to your skin as a pre-cooling technique, as it can construct your blood vessels and drive your core temperature up before you start your workout.

Females, Take Note

Everything I’ve written so far applies to both genders, but there are a few things that females should be aware of that do not apply to men.

Women sweat less than men and their sweat is more diluted.  In addition, women have fewer sweat glands per square inch on their bodies and their sweat glands are distributed toward their arms and hands.  (Conversely, men have more sweat glands in their torsos.)  Women also start sweating later than men do because women vasodilate, then sweat, which is a fancy way of saying that our core temperature has to rise to a higher number/threshold than a man’s does in order to begin sweating.

Finally, how women respond to heat losses varies depending on what phase of their menstrual cycle they are in due to the changes in estrogen and progesterone that occur over the course of one’s menstrual cycle.  In the high-hormone phase (days 15-28 in an average cycle) of the menstrual cycle, women are less sensitive to the heat because their skin temperatures and blood flow are lower in that phase.  Conversely, women have a harder time tolerating heat in the low-hormone phase of their cycle (days 1-14 in an average cycle).

The phases of life as they pertain to menstruation also impact how females tolerate heat.  Menstruating females tolerate heat differently than perimenopausal women.  Women who are in menopause tolerate heat differently in that phase of their lives, and finally, when a women is through with menopause, her body is (permanently) changed yet again in terms of heat tolerance.  Thankfully, endurance exercise actually helps offset and improve some of the hormonal changes that occur in menopause, meaning that endurance training itself can help a post-menopausal woman tolerate heat better.

Manage Expectations & Adjust As-Needed

On hot days, you will need to modify your expectations of what you can do in a workout or a race.  Remember, even if you start the workout or race properly hydrated, performance will decrease by 7% in hot conditions.  As such, it’s important to adjust the goals of the workout or race.

If you are aiming for pace-based (time-based) targets, it may be necessary to adjust the pace goals of a particular workout; this is especially true if you are in the aforementioned two-week acclimatization period.  You may need to adjust to monitor your heart rate to make sure your average heart rate doesn’t go too high, or you may need to modify a workout or race to be completed entirely on effort.  Remember that RPE will always, always serve you well if you take the time to learn it and develop the self-awareness to truly detect how you are feeling.

You may also need to adopt a different strategy for a workout in hot conditions.  For instance, you may need to incorporate regular walk intervals into a run.  On a bicycle workout, you may need to take longer rest periods in between workout intervals.  For a swim in very warm water, you may need to keep your effort much lower so you don’t overheat (sweating into hot water is, well, hot!).

Hot days are not the days to have a big ego and think that you can power through a workout or race the same way you could in conditions that are 40ºF cooler.  Be honest about the ambient conditions and make an appropriate modification so you can still challenge yourself and be successful in your workout or race.

Survive AND Thrive

Understanding how the body works and functions in hot ambient conditions can help make the extra effort to acclimatize, properly hydrate, pre-hydrate, pre-cool, and manage efforts worth it.  If you take the time to do these things (and especially hydrate!), you will be set up to not only survive hot days, but thrive in them.

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