The cold, hard facts about running in the heat

Well, it is that time of year, folks. Long hours of daylight, swimming pools, and the kids off from school… vacations?  No, the time of year when our complaints about the weather turn to asking who turned up the heat and my “what the forecast” app comes up with new places where sweat will accumulate. 
 
Now, unless there is some change to the pattern, in half a year we will be back to complaining about the cold.  But until then, us runners will run because fall races were built on summer training.
 
After spending 5 years in Hawaii with the best weather on the planet, my move to Oklahoma has provided a little extra stress on my body as my physiology adjusts for the different weather conditions including temperature and humidity.  Because of the extra work the body has to do to keep us warm in the cold temperatures and cool in the hot temperatures, running pace is going to decrease once the weather blows past ideal conditions.  I won’t define ideal conditions, because while research can give us numbers, most runners will have their own definition of what ideal is for their own body. 
 
When the body is exercising, muscles contracting producing heat as a byproduct of energy production.  Think about it this way, when you are cold and want to warm-up, you will often move around. That movement is a result of muscle contractions, which produce extra energy in the form of heat, not only warming you up but also the air around you.  On a summer day, the temperature outside is already elevated making it harder for the body to rid itself of the extra heat into the environment.  Throw in high levels of humidity and sweat evaporation becomes more difficult, taking away another mechanism in which the body gives off its excess heat.  
 
So what exactly is going on? And why are your runs suffering when the temperature goes up?  Energy metabolism, cardiovascular (heart and blood vessel) function and fluid levels are altered.  Plus the nervous system, which controls the thermostat in the body, is working to fine tune the other body processes to reach optimal temperature. 
 
In a basic continual loop: the more we sweat, the more fluid we lose, the more fluid we lose the less blood volume we have, the less blood volume we have, the more the body tries to keep the blood in our organs (heart, lungs and brain being the big 3) and working muscles.  The lower the blood volume, the lower the amount of blood that can be pumped with each beat of the heart. 
 
This pulls blood away from the surface (the skin)… but:  blood at the surface is how we pull heat out of the body, so the less blood at the surface, the more heat is contained inside the body at the core and the common element in fatigue with exercise is a critically high core temperature.
 
Got all that? Don’t worry, I’ll wait for you to reread it again and process.
 
Ok, now you have it! So let’s move on from there.
 
Monitoring all of this is our brain, serving as the central command center.  It is believed that regardless of what we might try- hydration, electrolytes, gear, fuel- in the end the brain will just slow us down when we get too hot.  Have you ever had your phone just decide that it is too hot to continue working? Yeah, kinda like that, but for the entire body.
 
So… how do you beat the heat?  The best thing to do is try to keep your core temperature down.  Increased fluid intake and even running through the sprinklers (come on, admit you run through the neighbors’ sprinklers on a hot run…) or jumping in the pool can help.  Rescheduling your run to a cooler part of the day, early morning or in the evening, when the sun is dipping low in the sky is another trick.  And, of course, get your body used to the heat by acclimatizing, repeated exercise bouts in the heat to train your physiology to adapt to the stress of the heat, although for some heat you just can’t prepare!
 
But, have no fear, training through the summer can help your body become efficient and maybe, just maybe, your fall race times will dip along with the temperature!