How to Run Through a Hot Summer

There is a reason why marathon season is either the fall or spring—it is way too hot in the summer!

Just like high altitudes, summer weather poses very real challenges to runners. The body simply cannot perform as well in high temperatures and humidity levels. Expectations need to be lowered and paces kept more reasonable.

To overcome those challenges, runners need a careful training approach that strategically uses timing, gear, and an understanding of the specific reasons why it’s so hard to run in the heat. With successful summer training, runners can set themselves up for an even better fall racing season.

Why is Running in the Heat so Difficult?

Summer training is hard for a variety of reasons that include temperature, humidity, and sun exposure.

Heat is clearly the largest obstacle. Hot weather raises the body’s core temperature, making running feel harder. Your RPE (rating of perceived exertion) will skyrocket.

Humidity is also a challenge. High levels of humidity prevent sweat from evaporating from our skin—a potent cooling mechanism. But even low levels of humidity, often felt in more arid environments, make running difficult because they increase fluid loss and dehydration. This leads to thicker blood, requiring more energy to pump the same amount. The condition is often called cardiac drift, where the heart needs to pump more quickly and forcefully to move viscous blood.

These unfortunate realities of summer training mean that runners will need to slow down to maintain the same effort.

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Beware the Dangers of Running in Summer

Summer running, therefore, has risks. A variety of heat illnesses can strike any runner who’s too aggressive on a hot July day, so it’s critical to understand the warning signs.

Heat cramps are muscle cramps caused by large fluid and electrolyte losses. They’re much more common after running than during, but they’re not serious. Stay hydrated and consume enough electrolytes with sports drinks or fruit.

Dehydration is common—and luckily, it is often not very serious. It’s still safe to lose up to 4% of your body weight during exercise! But any more than that and you risk dizziness, fatigue, and disorientation. Always make sure to start every run adequately hydrated. Drink 4-8 ounces of water or sports drink per hour during longer runs, and replace lost fluids as quickly as possible after finishing.

Heat exhaustion is a combination of dehydration, headache, nausea, and a high core body temperature of up to 104 degrees. If you experience these symptoms, stop running and get inside to cooler temperatures away from the sun. Rehydrate as fast as possible!

Heatstroke is the most serious of the heat illnesses and presents with a core body temperature of 105 degrees or more. The body shuts down even more so than during heat exhaustion, with symptoms of disorientation, clumsiness, confusion, poor balance, and often a lack of sweating. Get medical attention immediately. You’ll likely need to be cooled with a cold bath or ice.

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How to Make Summer Training Bearable

Despite the drawbacks of running in the summer, it’s a great time to be outside celebrating the capabilities of the human body. Just be careful! Here are seven ways to make running in the heat more bearable:

1. Run by effort, not pace. Your body only understands effort anyway.
2. Run early when the temperature is lowest and the sun is weakest.
3. Run trails, where there is ample shade and no asphalt to radiate the sun’s energy back to your body.
4. Lower your expectations. In adverse environments, performances won’t be as impressive.
5. Dress appropriately with synthetic fabric that doesn’t absorb sweat. Light colors will also reflect, rather than absorb, the sun’s energy.
6. Always start each run properly hydrated. If you run first thing in the morning, drink a big glass of water or sports drink before getting out of bed.
7. Carry fluids with you for runs longer than 60-90 minutes (or run near public water drinking fountains). If you can find a sprinkler to run through, all the better!

RELATED: How and Why You Should Mix Up Your Long Runs

The Advantages of Running During Summer

Despite the disadvantages of summer running, there are also many benefits that will make you a more efficient and faster runner. Not only does the body get better at dissipating heat and conserving electrolytes, but it also produces more red blood cells and becomes more efficient at controlling its core temperature.

These positive adaptations help you perform better in hot conditions. But they also make you perform even better in cooler temperatures, making autumn one of the best opportunities to race fast.

Embrace the heat—cautiously and with prudence—and there’s no doubt you’ll be ready to race new personal bests this fall season!

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