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Running and Racing in the Heat

Here in Maine, we had one final heat wave of the summer well into September. Highs well into the 80s with high humidity and sticky, stagnant air can be a recipe for disaster for endurance athletes. It seems like September days of reliable fall weather are gone. Summer still reigns in September in Maine.

I recently volunteered at an aid station for the Megunticook 50k trail race on the coast of Maine and saw a lot of runners suffering in the heat. We went through many buckets of water offering sponge baths and dolled out plenty of ice and popsicles to keep runners cool. Heat can cause cramping, GI distress, dehydration, dizziness, etc. Let’s look at some of the things you can do to keep yourself moving comfortably in the heat.

One of the reasons GI distress is so common in the heat is that our body systems are competing for blood. When we exercise in the heat, our body shuttles blood to the skin to dump heat. Our sweat literally comes from our blood. We sweat more in the heat to help us cool off. If we don’t replace the fluid lost in our sweat, we become dehydrated, our blood volume drops and our body systems start competing for our blood.  Our working muscles require blood to provide oxygen and fuel. Digesting food also requires blood but takes a back burner when our body is heating up and our working muscles are demanding oxygen and fuel. In this scenario, resources can be limited for digestion. Instead of being quickly absorbed, whatever fuel we consume may sit in our gut and slosh around causing GI discomfort. 

Battling GI discomfort in the heat is all about staying hydrated and keeping cool. Luckily you can train your body to handle the heat better. Let’s look at each of these tactics.

  1. Get used to it!

The more you exercise in the heat, the more tolerant you will become. Training for heat can be as simple as easing into it slowly. If your running season starts off warm and gradually heats up, that’s great heat training. If you land suddenly in a hot climate you will have to figure out how to ease into the heat. Embrace early morning runs. Run slower and for shorter distances at first. Go easy on the intensity. Let your body get used to the heat. There are specific heat protocols that involve a sauna that can be very effective in heat training. Here is a link to a great article put out by TrainingPeaks about how to approach heat training.

2.   Stay hydrated!

Staying hydrated will always make exercising in the heat easier. Sweat rate is unique to each person. So is the sodium content of sweat. Learning a little bit about your own sweat rate and sweat sodium content will make it easier to take care of yourself on those hot days. Anyone can perform a basic sweat test. It involves weighing yourself, naked, before you run (pee before you weigh yourself); going out for a regular 45-60 minute run; stripping down again after your run, wiping off any sweat on your skin, and weighing yourself again. The difference between your pre-workout weight and your post-workout weight represents the amount of fluid you lost as sweat during your run (don’t pee anytime during this process and don’t eat anything). If you drank water during your run you need to factor that into your equation (figure the weight of the fluid consumed and add that to the difference in weight pre and post-workout). This number divided by how long you ran for, is your sweat rate for those particular environmental conditions (temperature, humidity, etc.) Precision Hydration offers some great tools for learning more about your own personal sweat rate and for estimating the sodium content of your sweat. Why do we care? If you know your sweat rate and the sodium content of your sweat, you can more accurately replace these losses to avoid dehydration and overhydration (drinking too much can cause problems too). This is super helpful in the heat and in any long race.

3. Stay cool!

Whatever you can do to cool yourself down will help your body perform better in the heat. Tuck ice into your hat or into a bandana wrapped around your neck or down the front of your shirt. Drink cold fluids. Eat cold foods like popsicles. You can even pre-cool by consuming cold fluids and foods before you hit the trail. Ice vests are a thing too. Cool off with cold water sponge baths (let’s hope your race aid stations are as prepared as we were at the Megunticook 50k). Slowing down will also help your body cool down. If you don’t cool down, your body will force you to slow down anyway. 

Fall, thankfully, has finally arrived here in Maine but next time you’re headed south or when summer inevitably comes again next year, do what you can to get used to it, stay hydrated, and stay cool so you can handle the heat!

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