Heat versus Humidity

I want to start off by saying I love running in heat. My wife says I am part tortoise, as when I get into the bright and hot sun, I get energized and am ready to go. Last summer, for example, some of my best runs were on 90+ degree days. I personally hate cold weather. An upper 40's race is just insanely uncomfortable for me and my muscles get tight quickly despite my warm-up efforts. But more than the cold, I loathe humidity. It is my achilles heal.

So, why is it that my body seems to stop working properly when there is extreme humidity? And yes, extreme humidity is typically joined with the upper ends of warm to extremely hot temperatures as well.

As you run, your internal body temperature increases. Your body needs to release this heat, and what better way than to sweat and give off heat. The three technical ways your body cools are by thermal radiation (your body giving off heat), evaporation of perspiration (the cooling sensation you get when you are sweating), and heat convection (for non-scientific purposes, this is the same as giving off heat as well). I will analyze how each of these plays a role on hot with low to no humidity, hot with moderate to high humidity, and warm with moderate to high humidify days.

Hot with Low to No Humidity

If you turn on a heater that goes to 70 degrees in a room that is already 70 degrees, assuming the heater is not expelling higher heat to get "up to temperate", there will be no affect from the heater, as the surrounding air is the same temperature. The body is like this in that if your internal temperature rises, it will try to dispel the heat into the outside environment surrounding your body. This basically means through your skin, your body lets out heat that is absorbed into the surrounding air. However, on really hot days, the temperature outside may be equal or greater to your interval temperature. This means your body has basically lost 2 methods of cooling itself. I am not going to touch on the medical implications, because that is not what I am concerned about; but you can look up things like body overheating, heat stroke, etc. So, that means your body will be perspiring a lot more in order to try and cool itself.

For me, this works like a charm. But I am constantly keeping hydrated before, during, and after my run. This is imperative, otherwise, your body will be losing too much water too quickly, and you will get dehydrated even quicker.

Hot with Moderate to High Humidity

With the heat part in mind from the prior section, you now run into the next issue; there is a high level of moisture in the air. So guess what folks, you are out of luck. Not only are the two cooling methods form the heat not able to occur, but with the high humidity, the perspiration on your body cannot evaporate and cool you since the moisture level is the same or greater in the surrounding air. For swimmers, this is an issue, as you can easily overheat while swimming in many gym pools, such as ones that keep their pools around 82 degrees Fahrenheit or warmer. One of the few solutions to this is cold hydration. I stress cold hydration because if you can't cool from the outside, you need to cool from the inside.

For me, this is a major issue, as my water bottles on my hydration belt usually have the ice melted by mile 3, so when I really start needing water, I am drinking warm to almost hot water. For any product designers, I am tired of sending recommendations to you about how to insulate small bottles without compromising weight. So, how do I stay cool? I try to plan my outside runs based on "water stations". I will fill up a few larger bottles with ice and cold water. When I come back for a loop in my run I'll stop for a minute, have some ice cold (hopefully) water, and then I am invigorated and ready to go until my next loop.

Warm with Moderate to High Humidity

This is a really tricky condition; if you are not used to running in weather like this, then your body and mind will be in for a shock. First off, warm is defined as a cooler temperature than your internal body temperature. With the high humidity, you lose the ability for the sweat to evaporate in order to cool your body, however, you will be sweating a lot. This can create a false sense of cooling. The false sense is that you may think you are getting cooled due to the amount of sweat being generated and the coolish feeling since the temperature isn't excessively hot, but your body will actually be starving for cooling. With the temperature being warm, your body will still be able to dissipate heat to the surrounding environment, but at fairly low amounts. This means you are still having issues cooling. The solution here is to just stay hydrated with cool to cold liquid. Having a hydration belt, pack, or just having a bottle you can get to when you need it during your run should do the trick.

For me, this is not usually much of an issue, because I can't get myself up early enough or out late enough where the heat has gone down but the humidity is still up. I still make sure to train in this condition though, since you never know when you are going to have to race the day after a good rain and it's summer time (or whatever time of year depending on where you live).

Other Cooling Methods

I am not really going to dive too much into this, but it's important to know that you can drastically aid your body in cooling by wearing the right type of clothing. Cotton is not very good when it comes to heat, humidity, and sweat. You tend to become a soppy mess and overheat easily. You honestly get what you pay for. Good sweat wicking material is key; Under Armour and Nike Dry Fit are my two favorites. Nike's gear is usually loose fitting enough without being baggy, and allows for a full range of movement in all conditions and positions. Under Armour makes ridiculously great compression style clothing that really gets the sweat off of your skin and helps with cooling. It's also very breathable and there are many benefits to compression-wear. I'll have to do an article at some point on compression gear, as there is a lot of hype and confusion behind it. Also, don't forget to have sweat wicking running socks...man do they help. I use Nike and Puma (Puma is my favorite). Sorry, not a real fan of the other brands...I have tried them and have not been impressed.