I went for a run on June 27 as the rest of the Pacific Northwest huddled indoors due to record-breaking heat.
I’m used to jogging in the heat as a former cross-country runner: I hit the trails around 7:00 a.m. and chose a more shady path
The weather was nice when I left the home, at 76 degrees Fahrenheit, but as soon as I started trotting, I became intensely aware of the hot air against my skin.
After eight kilometers, my surroundings began to swirl, and I had to pull over to the side of the route to rest.
Summer is my favorite season, with its long days and frantic energy, but I loathe working out in the heat.
And, as the world warms as a result of climate change, it’s becoming more difficult to avoid.
So I turned to the pros for advice on how to stick to an exercise routine while staying safe—and when it’s better to forgo workouts entirely.
What effect does heat have on training
The human body is an inefficient machine. They break down the sugar we feed them during activity, gathering the energy that keeps each molecule together.
According to William Roberts, a sports medicine physician at the University of Minnesota Medical School, only 25% of that energy fuels our activity.
The rest leaves as heat, which the body must subsequently release into the environment to maintain its temperature.
To accomplish this, the nervous system activates a variety of systems that help the body cool down.
The heat from our blood is dispersed into the environment as blood vessels at the surface of our skin expand.
We also produce more sweat, which cools us down as it evaporates. (This explains why I turn an embarrassing shade of red when I run.)
The more hot and humid it is outside, the more difficult it is to get rid of surplus heat.
We can’t put heat into already hot air. Sweat can’t evaporate in humid air, either.
According to a 2007 study published in the journal Medicine & Science in Sports & Exercise, our core temperatures can climb as much as 1.8 degrees Fahrenheit for every five minutes of strenuous exercise if we don’t have a way to disperse that heat.
Temperatures that are pleasant for a day spent resting in the park can quickly turn hazardous for a workout, according to Roberts.
The temperature may have felt OK at first during my run during Oregon’s heatwave, but as I huffed and puffed up hills, the heat gathered in my body faster than it could escape—and the early-morning humidity rendered sweating nearly worthless.
What does heat do to the body?
I dipped my body in a swimming hole filled with snowmelt at mile 10 of my run and stayed there for five minutes before feeling cold.
Fortunately, I did. The symptoms I was having—dizziness and intense tiredness—could be signs of heat exhaustion.
According to a 2011 study by an American Family Physician, dunking yourself in cold water is the therapy of choice for heat-related sickness.
Heat exhaustion can be treated with rest, drinks, and relocating to a cooler location, but it can quickly develop to heatstroke, a life-threatening illness that can lead to organ failure.
Heat exhaustion signs are easy to overlook, especially for athletes who are accustomed to pushing through discomfort to reach their goals, according to Katy Griggs, a lecturer in sports performance and health at Nottingham Trent University in England.
“You witness some races where athletes have to be pulled out because they’re collapsing or struggling to get to the finish line,” Griggs adds.
Heat exhaustion symptoms include intense perspiration, nausea, a weak pulse, goosebumps, and a headache, in addition to weariness and disorientation.
Heatstroke is particularly sneaky since it often starts in the central nervous system, which is also the system that warns you when you’re overheating, according to Roberts.
Heatstroke victims may experience confusion or even feel cool rather than heated.
People who have specific medical disorders are more likely to have these problems than others.
Those who take specific drugs or have certain limitations should exercise caution in the heat, according to Griggs.
Blood pressure drugs such as beta-blockers and calcium-channel blockers interfere with the body’s capacity to control its temperature.
Antihistamines, laxatives, and tricyclic antidepressants all have this effect. According to Griggs, people with spinal cord injuries generally can’t sweat or regulate skin blood flow below the injury site.
Similarly, persons with multiple sclerosis sweat less than people without the disease.
As the temperature rises, it’s more important than ever to be safe
The good news is that you can train for high temperatures in the same way you can acclimate to high altitudes.
“The more you expose your body to that environment, the better it will be able to respond later,” Griggs explains.
Your body will manufacture more blood and become more efficient at circulating it to your skin in preparation for those workouts.
When you move, you’ll start sweating sooner and more heavily. You can also lose more water before becoming dehydrated if your blood volume is higher.
The trick is to start slowly, Roberts says: “We’re talking about half the duration and intensity of your typical workout.”
So, if you’re a six-mile runner, cut it down to three or fewer when the weather starts to warm up, whether it’s the first week of spring or during a significant heatwave.
You can gradually increase the intensity again. That was my blunder.
I mindlessly followed my training plan, which said that I should run 10 kilometers.
I didn’t factor in the fact that the temperature was about 20 degrees Fahrenheit higher than usual.
Acclimatization can take some time. Roberts advises athletes who are planning a race or other event that would likely take place in hot weather to start training three months ahead of time, ideally for 30 minutes each day.
There are a few additional basic things you may do to ensure that your body can withstand the heat.
According to Roberts, staying safe in the heat can be as simple as getting a good night’s sleep.
Sleep, hydration, and whether or not you’ve recently been ill all have an impact on your body’s ability to regulate heat.
If it’s hot outside and you’re not well-rested or hydrated, or if you’ve recently recovered from the flu, avoid the workout and go to an air-conditioned gym (provided you’re COVID-19-vaccinated and case counts allow clubs to open safely).
The same is true if you’ve had a few too many drinks the night before. Alcohol not only dehydrates us, but it also hinders our capacity to cool down. Also, go with a friend on those extremely hot days.
“Sometimes it’s a matter of somebody keeping an eye out for you,” Roberts says, adding that a friend can notice changes in your behavior before you do.