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When is it too Hot for a CrossFit Workout?

How to train CrossFit in the heat

It’s that time of year again. Summer, when the days are longer and the sun is hotter, can either super- charge your CrossFit workout or knock you on your butt!

A vigorous workout in the summer heat can certainly lead to serious health consequences, but, to the surprise on no one who has ever sweated through and benefitted from Bikram yoga program, it can also enhance the performance impact of the activity. To quote Don Schlitz, who wrote the song most likely to be sung by the every one of the slightly-overserved patrons of any karaoke bar south of the Mason-Dixon Line – The Gambler  – “You gotta know when to hold ‘em, know when to fold ‘em, know when to walk away and know when to run!

The Heat is On

Glenn Fry – 1985

Your mama probably warned you about playing outside in the summer heat and most likely you disregarded everything that saintly woman ever said!  Like a lot of motherly admonitions, this advice to “play in the shade” was based some science and some old wives’ tales.

First off, the bad news. She was right. If you overdo anything – from playing golf to flipping truck tires in a CrossFit class – when the temperature is 103 in the shade, you can find yourself dehydrated, disoriented or dead. Fortunately, dying from a heat stroke is extremely rare. One will typically become incapacitated with heat exhaustion symptoms long before the Grimm Reaper of Heat comes to fetch you!

According to the Center for Disease Control and Prevention (CDC), about 2,000 U.S. citizens die of heat-related causes each year. The agency notes, “Exposure to extreme natural heat poses a public health problem because it may result in heat-related illness (e.g., heat cramps, heat exhaustion, heat syncope, and heat stroke) and heat-related death. Exposure to extreme natural heat also may result in death because it exacerbates preexisting chronic conditions (e.g., cardiovascular, cerebral, and respiratory diseases), and because patients receiving psychotropic drug treatment for mental disorders and those taking medications that affect the body’s heat regulatory system or have anticholinergic effects are more susceptible to heat effects.”  

Hot Fun in the Summer Time

Sly and the Family Stone – 1969

For all of the bad news about the dangers of working out in the heat, there is some great news for athletes who want to increase the physical benefits of their work. While there will be copious sweat involved but slugging through a WOD when it’s hot as hell can result in exponential gain.

According to an article in Men’s Health Magazine, a heat-wave workout can do wonders for the athlete’s performance. “Researchers from the University of Oregon tracked the performance of 12 very high-level cyclists (10 male, two female) over a 10-day training period (with two days off in the middle) in 100-degree heat. Another control group did the exact same exercise regimen in a much more comfortable, 55-degree room. Both groups worked in 30% humidity.

Researchers discovered that the cyclists who worked through the heat improved their performance by 7% (a noticeable and significant amount in cycling), while the control group did not show any improvement. What surprised researchers most was that the experimental group not only showed that they had achieved a level of heat acclimation, but the training also helped them to function better in cooler environments.”

How to CrossFit outdoors

This research points to some “magic numbers” for working out in the heat:


The number of degrees Fahrenheit you need to elevate your core body temperature during training sessions.


The number of minutes you want to have that elevated core temperature maintained during your heat training to make sure that you’re truly getting the heat acclimation benefits.

5 to 10  

The number of days you need to train in the heat. In order to really heat acclimate the way the researchers were proposing an athlete must go out and exercise in the heat for five to ten days, with pretty significant exposure at times.

Drop it Like its Hot

Snoop Dogg and Pharrell -2004

Dr. Michael Landers  who is  a sport medicine physician in Dallas and a member of the physician referral line at Texas Health Spine & Orthopedics Center has some words of advice for those who decide to take on the hot summer WOD’s

“It’s critical to stay hydrated,” Dr. Landers said. “You sweat more as it gets hotter and more humid. You need to ensure you are replacing those fluids as you run, bike, or do other workouts in such extreme weather.”

He recommends consuming 16 to 24 ounces of water two hours before exercising in hot temperatures. Past that, he says to take in another six to eight ounces of fluids every 15 to 20 minutes of exercise.  

“The humidity is also an important factor to consider for summer workouts,” he said. “During and after exercise, the body is cooled by the evaporation of sweat. When it is humid the athlete does not experience as much of that evaporative cooling effect because the air is saturated with humidity. On days when it is both hot and humid, take the WOD inside.

“The most important consideration for these summer workouts is proper acclimation,” Dr. Lander said. “In the summer we spend a lot of time in air conditioned spaces and when it comes time to exercise outdoors the sudden heat overwhelms the body.  Try to acclimate to the heat a few hours before your workout by going outside or at least raising the inside temperature.

“Finally, it is very important to take it easy in the beginning and gradually work into the extreme heat. Wear breathable clothing and ramp up the intensity over days. Don’t try to go full-bore if you are not used to the heat.”

He noted some signs to watch out for.

Heat Exhaustion Symptoms: Profuse sweating, severe headaches, dizziness and intense thirst.

Heat Stroke Symptoms: Lack of sweat in spite of heat, a core body temperature greater than 104 degrees Fahrenheit, with complications involving the central nervous system that occur after exposure to high temperatures. Other common symptoms include nauseaseizures, confusion, disorientation, and sometimes loss of consciousness or coma.

If these symptoms are noticed, call 911 immediately!

Have you had good experiences or bad experiences with working out in the hot summer sun? Contact us and we’ll share your story with our readers.