Running in the Heat and Humidity

It looks like this summer is going to be a hot and humid one and we are feeling the effects of the heat already. As the temperature rises, your body is working harder to cool you down. Your heart rate increases and breathing becomes more rapid. Add some humidity to the mix and it feels even hotter. What is going on and how do we adapt?

What is going on in the body?

When you run in the heat, your overall body temperature rises. The more body mass (insulation) you have, the more heat your body generates and as you age, you become less adaptable to the heat. When your temperature rises, the blood in your body starts to go to your skin to cool you off through sweating. Air circulation helps the sweat to evaporate and cool you down. But, high humidity prevents the sweat from evaporating from your skin so that your body can’t cool. There is no easy way to calculate the heat index, but here is a handy chart that I found.

When your blood is going to your skin that means that less blood is available to send oxygen to your muscles. This is going to slow you down. Every 5 degrees rise in temperature above 60 degrees can slow your pace by 20 to 30 seconds per mile.

Top that off with each of us loses a different amount of sweat and sodium so the amount of water and electrolytes that each of us needs is going to be different.

How do you best prepare for running in heat and humidity?

Take your time to ease into it. It takes a few weeks for your body to acclimate to the change. During the acclimation period, slow your pace down a bit while keeping the effort the same.

Picking the appropriate clothing is important as well. Wear lightly colored technical clothing and keep it as minimal as possible. If the temperature is above 70 degrees, wear shorts and a tank top. A visor will help to keep the sun out of your eyes while allowing the heat to evaporate through the top of your head and sunglasses will be important as our runs go later into the morning because your eyes can be damaged by the sun.

Our scheduled runs are at the coolest part of the day. Be sure that when you are running on your own, you plan your run for early in the day. Try to run on a route that has shade.

As we have mentioned so many times, hydration will be the most important thing that you can do to keep your body cool. Keep hydrated on all days, not just the ones where you run. Electrolytes become even more important for fluid absorption and retention as you are sweating and losing water, so pay special attention. Your urine should be the color of straw. Darker than that means you aren’t drinking enough and lighter means that you are drinking too much.

You can use a sauna to increase your hyperthermic conditioning. By spending time in the sauna, your body will go through some interesting adaptations including increased blood plasma volume and blood flow to the heart. More plasma means that your blood will flow easily and will take longer to get sticky and thick. Spending time in the sauna will also teach your body to have a lower core temperature and increase your sweat rate. Using a sauna should be done in moderation and be sure to wipe the sweat from your skin when you emerge from the sauna because you just released some toxins from the body.

How about after the run?

You are most likely going to feel a bit more fatigued that you normally do. Your body is still working hard to cool down long after you are done with the run. The blood is going to the skin instead of to the muscles and so recovery is going to be slower. Take your recovery days seriously.

Take an Epsom salt bath. The skin is the easiest way to get lost minerals back into the body. Add two cups to a warm bath, soak for 30 minutes and then rinse in a cool shower. The Epsom salts will also help with muscle fatigue.

Keep hydrating! Your body is about 70-75% water so keep your cells happy and healthy through hydration.

I hope these tips are helpful to you as you acclimate and remember that sweating is a good thing—it means that your body is doing what it should be doing!