The best strategies to keep bodies cool in a heatwave, according to researchers

Full body immersion or cooling the extremities will help maintain healthy body temperatures


An Iranian street vendor pours water on his face to cool off during a heatwave in Tehran, Iran, 02 August 2015. Photograph: Abedin Taherkenareh/EPA

As we hit high-heat season in the Northern Hemisphere, it is useful to clarify tactics that can be used to help maintain healthy body temperatures. These tips are not commonly known and can be adopted by anyone, anywhere. While I am a climate scientist, my funded work is in the area of heat transfer, particularly in the human body. I work with medical companies to maintain healthy body temperatures during surgeries or other situations. I also deal with scald burns and I often serve in burn injury litigation.

Here are some key tips. First, avoid hyperthermia in the first place – drink plenty of fluids, avoiding direct sunlight, trying to get a respite from heat each day, avoiding physical exertion during the hottest parts of the day are all great suggestions. But, if you need to lower a body temperature, Dr. Robert Huggins, VP of Research and Athlete Performance at the Korey Stringer Institute suggests:

The general rule is to cool as much of the body’s surface as possible …. the larger the area you cool and the colder the device you use to cool it the faster the cooling rate. An appropriate goal is to use a method that cools at a rate of 0.15°C per minute. This can typically be achieved by immersion techniques using a tub or other basin filled with ice cold water or via rotating cold ice towels over the body.

During exercise if there is limited access to the entire body (e.g. football or fire-fighters), cooling the hands, face and feet will help, and if possible, use a fan to increase evaporation from these surfaces. However, when heat stroke is suspected, these strategies are not nearly as effective as whole body methods; opt for immersion cooling.

So how do you know if someone is suffering from hyperthermia or heat stroke? A great resource is the Korey Stringer Institute, which lists many symptoms for heat stress such as fatigue, weakness, pale appearance, headache, nausea, vomiting, fainting, dizziness, and others. The heat stroke treatment they recommend, while geared toward athletes, is still useful for the rest of us. 

The list removal of clothing and equipment, cooling of the athlete using 30 minutes of whole body immersion in cold water (or a cold shower), call for medical treatment, and other tips found here. A journal publication was published in 2010 that also recommended cold-water immersion for treatment of exertional heat stroke. That publication does warn that over cooling can lead to hypothermia, so care must be taken.

In many actual situations, full body immersion isn’t possible. What can people do then? Well, there is extensive evidence that supports the cooling of the hands, face and feet. The technical term for these areas is glabrous (non-haired). These areas are excellent at transferring heat and in fact, the body can increase the blood flow to these regions which, when cooled, flows back to the body providing core cooling. 

One paper looked at the impact of cooling athletes’ palms on their ability to recover between exercise sets. They found that “palm cooling hastened heat removal”. Another publication, just out in 2015 in the journal Wilderness and Environmental Medicine compared cold packs applied to the neck, groin and armpit with cold packs applied to the cheeks, palms and feet. That study found that applying cold packs to the cheeks, feet, and hands almost doubled the cooling effect. They write:

Application of cold packs to glabrous skin surfaces was more effective for treating exercise-induced heat stress than the traditional CCP cooling intervention. This novel cooling technique may be beneficial as an adjunctive treatment for heat-related illness in the prehospital environment.

These studies should be viewed as helpful however they often deal with lower temperature heat stress; for very high body temperatures, immersion is recommended.

Another recent publication, this time in one of the top biomedical engineering journals, looked at heat transfer in people that were insulated, again they found effective cooling in individuals when the hand was targeted with 10°C (50°F) water.

For people who are interested in learning more, a great resource is this 2014 PhD Dissertation from the University of Connecticut. That study looked at the effects of hand cooling and found that while it shows some promise, more research is needed, particular on the interactions of hand cooling with other factors.