Every summer, as if I have just received a frontal lobotomy and can no longer remember the previous 21 summers, I head out for a run in the Midwestern heat and humidity and think - wow that was slow and hard and awful. And as if I almost have forgotten any exercise science, I feel like I have lost all of my speed and running suddenly feels like I am a brand new athlete, but with a long history of paces and perceived exertions that make me all crazy and think the end is near. I know that I am not alone in this, as I read a lot of athlete logs with similar sentiment. This week we thought we would take a little closer look at what happens when you run in the heat.
First let’s chat about heat acclimation. It is important to understand that you can make serious adaptations to the heat, but it takes time and a proper protocol (which we can talk about in another blog at a later time).
What is Heat Acclimation?
Heat acclimation is the process by which your body adapts to the heat and begins to work more efficiently to shed heat. Specifically, over time the body becomes better at sweating which is how we decrease our body temperature when it is hot outside. The more efficient we are at sweating, the faster we can cool our body. Sweat cools the skin’s surface by the process of evaporative cooling, which means that blood flow to your skin reduces heat stress. This is also why running in the heat is hard - we only have so much blood. It either has to go to the muscles or to the skin to cool the body. For an in depth discussion of the process, here is a great study from 2014. The essence is that heat exposure makes your body a better sweater which in turn prevents you from overheating and rocketing your heart rate through the roof. The physiological process of heat acclimation takes about 2 weeks, but the psychological adaptation can take 6 weeks. Which means if you live some place where the weather is a roller coaster, it can be hard to acclimate as quickly.
Therefore, when you head out and have that awful slogfest of a run, it is important to understand if you are in fact acclimated to the heat.
What if you are Heat Acclimated?
Will the heat still affect your performance. The answer is yes … but not as badly if you are not!
Check out this really great article from Runner’s World that takes a look at performances in 10 degree bands. The effects of heat on performance starts at 59 degrees - so just remember that when you hit the pavement. 59 - freaking - degrees. Dare I say, we would all dream to be running in that today!
Clearly, temperature is an issue, but the best way to determine how you will be affected is to look at the dew point. This makes your body feel even worse than just a high temperature alone. The dew point is the temperature at which water condenses, so the closer the dew point is to the temperature of the air, the harder it will be for your sweat to evaporate and for the body to cool itself. Once the dew point gets above 60, you will feel it on your run. A dew point of 70 is gonna put you in the pain cave and above 75 - well, time to think about maybe hitting the treadmill or really dialing back your run effort.
Now that we understand how the weather plays a role in run times and how you feel about those times - because let’s face it, that is the essence of endurance sports - the constant loop of how you feel and how you think you feel and how you want to feel - what can you do to make those hot AF runs not crush your soul? Here are three simple tips.
LET GO OF PACES. While our athletes use other metrics to guide their runs, it is hard to not equate pace with performance. YOU HAVE TO LET THAT SHIT GO in the heat. It is not only better for your mental health, it is also plain old science. Check out this fun little calculator that you can play with to see how your run is affected at various temps.
STOP BEING MENTAL. A few weeks ago, I was working at a private tri camp in Clermont, Florida with an athlete, which meant that I had to start my long run in the afternoon. It was 104 or something crazy, but I just could not handle being on the treadmill, so I made a plan to run out and backs so I could bail on the run if needed. And also so that I would be able to be close to my fuel and cold water. Once I wrapped my mind around the feeling of running in a sauna, I really had a fabulous run. I totally let go of any pace metrics, kept an eye on my HR, fueled well, and just repeated my mantras over and over.
NUTRITION IS KEY. Make sure you run with proper nutrition; you should do this all the time, but it is even more important in hot weather. Plan a route so that you can get more fuel if needed. Listen to your body and do not try to David Goggins your runs - be smart and safe in the heat.
Finally, remember that there are performance gains made when you adapt to the heat. There is some evidence that they are similar to those gained at altitude - so when that run starts to suck the life out of you, one sweat molecule at a time, lean into it, and know that it will make you stronger!