Everything You Need To Know About Running In Hot Weather

Summer training ain’t easy. With skyrocketing temperatures, high humidity and a scorching sun, it can feel like it’s impossible to get in a good run. How can you get your exercise without burning up?

This post originally appeared on Strength Running

A long run or fast workout is hard enough, let alone a race. Like a friend of mine always says: In the heat, I don’t compete! Even if you just take your run easy and skip the hard workouts, how are you even supposed to just feel good when running in the heat and humidity of summer?

Training well through the heat and humidity of summer takes a careful approach that combines timing, gear, and an understanding of why exactly it’s so damn hard to run in the heat in the first place.

But of course, it will still be tough. Last year at the Heartbreak Hill Festival put on by Runner’s World, I was talking to another runner about a race she ran in Miami. She was lucky to meet Kara Goucher and Shalane Flanagan (two professional distance runners) who told her: “I’ll take running at altitude over running in Miami any day!”

Even the pros hate summer running!

Instead of complaining about how difficult it is to run in the heat, let’s see how we can make the best of it without injuring ourselves or putting our health in danger. And maybe even help make the fall our fastest season yet.

Why Is It So Hard To Run In The Heat?

If you’ve read Christopher McDougall’s fantastic book Born to Run, you’ll remember that humans are amazing endurance animals when it comes to running for a host of reasons. We have:

• A huge Achilles tendon that produces a significant energy return while running.
• A (mostly) hairless body and highly evolved sweat system.
• Big butts. I cannot lie: according to Harvard professor Daniel Lieberman, our glutes are “running muscles”.
• A special ligament that attaches the spine to the skull and keeps our head from bobbing as we run.

Can you guess which adaptation here is impacted by running in the summer? It’s our incredible sweat system, of course.

Perspiration helps cool us off because as our sweat evaporates from your skin, it takes heat with it. But when humidity rises, it reduces your body’s evaporation rate because there’s already so much water in the air. Soon, you feel overheated and have to slow down.

If you live in an arid place where the humidity is low, a hot summer day can still wreak havoc on your training for two important reasons.

First, the dry air evaporates sweat from your body almost as quickly as you’re producing it, so you can become dehydrated much more quickly. If you start a run slightly dehydrated or run long without any fluids, your performance will significantly decrease (and you’ll feel like death).

Second, as you become more and more dehydrated throughout a run, your heart needs to work harder to pump your blood because it’s becoming thicker (among a few other reasons too). This is called cardiac drift: your heart rate increases over the course of a run even when the intensity stays the same.

Let’s not also forget the heat and sun, both of which increase your core body temperature. As soon as you start getting too warm, running will feel much more difficult. Your “Rate of Perceived Exertion” (RPE) will increase even if you’re running a pace that’s usually comfortable.

Less evaporation because of higher humidity levels, increased chance of dehydration, and a higher core body temperature means that you’ll have to run slower to maintain the same effort. An unfortunate reality of summer training.

The Dangers Of Running In The Heat

This article isn’t meant to scare you. After nearly 16 years of competitive racing and running in the heat and humidity of New England and the mid-Atlantic states, I’ve never been seriously affected by the heat in any meaningful way. Neither have any of my teammates in college and high school — and we raced and ran very tough workouts in brutal temperatures sometimes.

But that doesn’t mean the dangers aren’t real. If you run too hard at noon in July, you might experience some type of heat illness. Here’s what you need to know so you can avoid these setbacks.

Heat Cramps: Muscle spasms that are caused by large fluid and electrolyte losses from sweating. They can occur while exercising but also hours after your run. No need to worry, they’re not serious — but make sure you stay hydrated and get enough electrolytes with sports drinks or fruit like bananas.

Severe dehydration: We’re all familiar with dehydration. Up to a 4% loss in fluid levels from exercise is still safe, but any more than that and you may experience dizziness, fatigue, and even mental disorientation.

Prevent this level of dehydration by starting your run already hydrated (your pee should be a straw colour) and replacing your lost fluids as soon as you finish running. You can figure out exactly how much fluid you’ve lost by weighing yourself before and after a hot run.

Heat Exhaustion: If you work out too hard in the heat, you may come down with heat exhaustion — a case of dehydration, headache, nausea, and a core body temperature of up to 104 degrees. It’s much more common in runners who aren’t adapted to the heat.

If you think you have heat exhaustion, stop running, get out of the sun, and cool down with a cold drink and preferably air-conditioning. And next time, run earlier in the day!

Heat Stroke: Danger! Heat stroke is very serious because your core body temperature is probably over 40 degrees C. Symptoms include disorientation and clumsiness, confusion, poor balance, and a lack of sweating. Immediate medical attention is required where you’ll be cooled with a cold bath, air conditioning, and cold liquids.

At the 1978 Falmouth Road Race, Alberto Salazar (two-time winner of the NYC Marathon) suffered heat stroke and collapsed at the finish line after falling to tenth place. He was rushed to the hospital with a temperature of 107 (!) degrees F and read his last rites in a tub of ice water. Luckily Salazar recovered and went on to become one of the greatest coaches our sport has ever seen.

What You Can Do To Beat The Heat

The heat of summer isn’t the time to run your hardest workout and biggest distance weeks — unless you’re super careful. Keep these tips in mind to stay safe and healthy:

Run by effort, not pace. Running in the heat is the perfect opportunity to work on the skill of running by feel. Instead of strictly following pace targets that you might normally follow, run by time and effort rather than distance and pace.

Run early. There’s no perfect time to run in the heat of summer. But the early morning hours offer the lowest temperatures and a break from the strongest hours of sunlight (even though the humidity will be at its highest).

Get off the roads! Asphalt and concrete absorb heat and radiate it back onto your poor, wilting body. The summer months are a good time to try more trail running. You have to run a little slower on trails and they’re usually shaded, both of which will keep you slightly cooler. Win-win.

Don’t wear dark colours or cotton. Gear matters in extreme conditions so dress appropriately! Synthetic fabric like polyester is used in most running gear these days — take advantage of it.

Start your run hydrated (and keep hydrating). Even though hydration has been overemphasised in the last decade (see Waterlogged by Dr Tim Noakes), it’s important to hydrate well before and after your run. Unless you’re running more than 75-90 minutes, you probably don’t need to take any water with you. But learn what works for you.

Plan your run around water. I never carry any fluid with me on a run — even a 20 miler in the summer. Instead, I run by fountains in public parks where I can swig some water and stay hydrated. If you live in a dry climate, running through sprinklers can help you stay cool, too. And who doesn’t love frolicking through a sprinkler?

The Advantages Of Running In The Heat

With all the whining we do about summer training, it can actually make you a better runner. Running in the heat causes our body to acclimatise to the conditions and adapt:

• Your body gets better at sending blood from your core to your skin, helping to dissipate heat.
• With all that blood rushing to your skin, your muscles now get less oxygenated blood. So to compensate, your body produces more.
• The body gets better at controlling its core temperature and it won’t increase as much after you’ve acclimatized.
• You start sweating sooner at a lower body temperature to improve the cooling process.
• Sweat contains less salt so you’ll maintain the right electrolyte balance (with a proper diet and hydration).

All these adaptations improve your efficiency and make you ready to run even faster as soon as the heat and humidity drop in the fall. So embrace the heat and run through it!

Then again, there’s also some evidence to consider that suggests that summer training is difficult because you think it will be difficult. But tell me that after I shuffle home from a track workout in the sun and I might throw you out of my living room window.

It’s useful to know that at least some of the drudgery of running in the heat might be because of our brain. It may present a good opportunity to “train your brain” to be comfortable being uncomfortable.

When you do, you’ll be in a good position to run a lot faster this fall. Take advantage of the physical and mental adaptations you’ve gained from a summer of uncomfortable running.

You might just surprise yourself at what you’re able to run in a few months!

Everything You Need to Know About Running in the Heat This Summer [Strength Running]

Jason Fitzgerald is a 2:39 marathoner and USATF-certified running coach at Strength Running. Get his latest coaching advice and free injury prevention course here.

Image adapted from Clandann2 (Pixabay) and Nemo (Pixabay). Photos by Run Racing (Flickr), U.S. Army Corps of Engineers (Flickr), KnowYourMeme.