So, what goes on when we exercise and compete in the heat? And, what can you do both during workouts and races, and after them, to cope with the heat?
Your body is already working hard to keep you cool as you exercise. Nearly three-quarters of the energy we generate is dissipated as heat and only a quarter of it is actually put toward forward momentum. That’s a lot of heat for the body to expel and regulate. The heart is not only pumping O2 enriched blood to the working muscles but also to the skin to counteract heat accumulation. Veins expand to get that blood as close to the skin surface as possible and sweat evaporates to further the cooling process. Even though we may feel like we’re in a blast furnace, we are cooler than we would otherwise be if these things didn’t occur.
For every degree Fahrenheit your core temperature rises, the heart has to be approximately 10 bpm (beats per minute) higher. Elevated HR further exacerbates the burning of precious muscle glycogen and electrolytes. The act of drinking fluids helps offset the rise in core temperature to a degree (pun intended), but at some point our liquids tend to warm up as well, at which point they don’t help so much. The body gets into a huge tug-o-war between trying to supply the body with what it needs to perform and regulating heat. These two things are at odds and when generating heat overtakes heat dissipation, bad things can happen such as heat exhaustion and heat stroke – or worse, death.
When we exercise and sweat, we are losing liquid at a faster rate than we can replace it. The more we sweat, the more we create a drop in blood volume due to the high water content within our blood. Less water in our system equals less blood volume. Lower blood volume means that for every beat of your heart, less O2 and fewer nutrients are pumping through your system. Hence for the elevated HR as you dehydrate and/or heat up. The key is to hydrate as much as you can without hyper-hydrating. Hyper-hydration, also known as hyponatremia, is also a life-threatening situation. If when hydrating you start to feel your stomach bloating, stop drinking immediately. The bloating is due to the receptors in your GI Tract becoming fatigued and losing the ability to continue emptying the stomach. We’re still thirsty, so we keep drinking and exacerbate the bloating because more and more fluids are sitting idle in the stomach. Instead, stop drinking and allow the body to re-find stasis. You will know because the bloated feeling will go away and you’ll feel normal again. That is your cue to start drinking again.
One thing you can do to help keep your core temperature down is to ice your bottles. For the bottle you will drink first, fill it halfway with ice. For your additional bottles, you can freeze them completely. By the time you need them, they will have thawed yet should still be cool to cold. There’s nothing more refreshing than drinking cold liquid when you feel hot. Another thing you can do is carry an extra bottle of straight ice water. When you feel the heat building up in your head (a clear indicator your core temp is quickly rising), take this ice water and squirt it over your head, neck and chest. Whew! Instant relief! You should be able to get 3-4 solid douses from one water bottle and the cooling aspect will do you good. The goal isn’t to just keep going in the heat, but to keep going strong.
So, once you’re done with a workout in the heat, what can you do to promote recovery so you can come back and do it all over again either later that day or the next day? First thing is to down a big glass of ice water. Get the rehydration process kickstarted and also cool down your core temperature a little bit. Chances are you may not be in the mood to eat anything. In fact, the thought of food might make you downright nauseous. That’s OK. Listen to the body and don’t force feed yourself. You will be ready to eat in 15-60 minutes, still well within the window of opportunity to maximize recovery. If you find yourself without an appetite, drink the ice water and then jump into a cool shower. As you acclimate to the cooler water, turn the temperature down incrementally until it’s running as cold as you’re able to stand. Let the water flow over your head, arms and legs so it hits the blood at the skin’s surface. After about 10 minutes in the shower, you should feel refreshed and much more comfortable temp-wise.
The punchline is that the more quickly you can calm the body down and return it to stasis, the more quickly it can focus on repairing the damage done by the heat and the effort of the workout both. Contrary to popular belief, the cooling down of the body actually facilitates blood flow throughout the body and accelerates the return to resting HR, resting blood lactate and normal pH levels. Now, while you may have tried or want to try ice baths, there’s more research stating ice baths are less effective at promoting recovery. The premise is that they are too much of a shock to the body and can actually promote increased soreness for the next couple days. Better to start with cool flowing water that you gradually turn to “comfortable cold”.
Once you’re ready to consume some food, it probably makes sense to first turn to some sort of recovery shake. This is because liquids do sit easier in the GI Tract than solids and take less blood to break down and process. Eating solids right after is fine, but it might make more sense to save the solid meal for a couple hours after you ingest the recovery shake. My favorite smoothie is a banana, frozen berries, some Greek yogurt, a spoonful of chocolate peanut butter, a scoop of whey protein and almond/coconut milk. Blends up well and the frozen fruit gives it a nice, cold temperature. Great stuff!
During the rest of the day, be extra sensitive to drinking water. You’ve lost a lot more liquid than you may think, so your goal should be to have normal-colored urine before dinner time (assuming you’re ending your workout around lunchtime; so call it a handful of hours later). You don’t want to guzzle a gallon of water right after the workout. Likewise, you want to avoid stopping rehydration after the initial glass of ice water and smoothie. Every hour, drink 12-16 ounces (a half-liter) of water until your urine is its normal color. You don’t need to strive for clear, but dirty yellow is too dark.
Lastly, an easy way to better acclimate to the heat is to spend more time outside. You don’t have to be active. You can walk the dogs in the heat of the day, or simply spend time outside – either in direct sun or in the shade – doing what you might normally do indoors. It doesn’t have to be all day, either. Start with 15 minutes and build it up to an hour from there. A little goes a long way. Also, minimize the use of A/C; when you do need it, set the thermostat for 74-76 degrees rather than, say, 68. A/C is arguably the worst invention for allowing us to cope with the heat (as great as A/C can feel at times!). You can also minimize the use of A/C in your car. Drive with the windows down; allow for a little sweat. Let your body do what it was meant to do when it’s hot outside.