Hot and humid summer weather can make even a familiar workout feel more difficult. Ann Swartz, Professor of Kinesiology at the University of Wisconsin-Milwaukee Joseph J. Zilber College of Public Health, recently joined WUWM’s Lake Effect to explain why exercising in the heat places additional strain on the body and how people can stay active safely.
According to Swartz, humidity can be an even greater challenge than high temperatures because it limits the body’s ability to cool itself.
The body primarily releases heat through evaporative cooling. As a person becomes warmer, the body produces sweat. When that sweat evaporates, it helps lower body temperature. However, when the air is humid, sweat does not evaporate as effectively.
“It’s not the heat, it’s the humidity” is more than a familiar Midwestern saying, Swartz explained. During hot and humid conditions, the cardiovascular system must work harder to support physical activity while also helping the body release heat. As a result, exercise may feel more difficult and heart rate may rise more quickly.
Plan outdoor activity around the heat
Swartz encourages people to consider the time of day before exercising outdoors. The sun is generally most intense between 10 a.m. and 4 p.m., so early morning or evening workouts may be safer and more comfortable.
People should also adjust the intensity and length of their workouts based on the conditions. Slowing down, taking additional breaks and choosing a shaded route can help reduce the risk of overheating.
Clothing can also make a difference. Swartz recommends lightweight, breathable and moisture-wicking clothing that supports evaporation. Light-colored clothing reflects sunlight rather than absorbing it. A hat or visor and sunscreen can also provide protection from the sun.
Hydrate before, during and after exercise
Staying hydrated is essential because sweating causes the body to lose water. Dehydration can make it more difficult to regulate body temperature.
Swartz recommends drinking approximately 16 to 20 ounces of water one to two hours before exercising, followed by a few additional sips shortly before beginning.
For workouts lasting less than 60 minutes, plain water is generally sufficient for most recreational exercisers. People exercising for more than an hour or completing a high-intensity workout may benefit from an electrolyte drink.
Electrolytes should not be overconsumed, however. Many electrolyte beverages contain sodium and added sugar, and consuming more than the body needs may cause stomach discomfort or an electrolyte imbalance.
After exercising, people should continue drinking fluids to replace what was lost through sweat. One way to estimate fluid loss is to weigh yourself before and after a workout. A decrease in weight can help indicate how much fluid needs to be replaced.
Help children and young athletes stay hydrated
Children may be less likely to stop playing or practicing to drink water. Parents, coaches and caregivers can help by placing drinks in an easy-to-find location and scheduling regular hydration breaks.
Foods with a high water content, such as watermelon, can also help children replace fluids.
Young athletes participating in sports such as football may face additional risks because helmets, pads and uniforms can trap heat. Swartz recommends frequent breaks, removing helmets during rest periods when appropriate and drinking water or an electrolyte beverage.
Do not skip warmups and cooldowns
Although muscles may already feel warm on a hot day, a proper warmup remains important. A warmup prepares the heart, lungs and other body systems for increased activity.
A gradual cooldown helps those systems return safely to their resting levels and may reduce dizziness or fainting after exercise. During hot weather, Swartz recommends extending both the warmup and cooldown and completing them in a shaded area when possible.
Know the signs of overheating
Early warning signs of heat-related illness can include:
- Excessive thirst or sweating
- Muscle cramps
- Headache
- Dizziness or lightheadedness
- Unusually rapid heart rate
Anyone experiencing these symptoms should immediately reduce their intensity or stop exercising, move to a shaded or air-conditioned location, remove unnecessary clothing and drink water or an electrolyte beverage.
A fan or cool compress can also help lower body temperature. Cool compresses may be especially effective when placed on areas with greater blood flow near the skin, including the forehead, back of the neck or armpits.
More serious symptoms, including confusion, a racing pulse or no longer sweating despite being very hot, may indicate a medical emergency. Emergency medical assistance should be contacted immediately.
Swartz emphasized that exercise benefits physical and mental health, but people should remain attentive to their bodies and avoid pushing through symptoms of heat-related illness.
“You’re doing something good for your body when you’re exercising outside,” Swartz said. “You want to make sure that you’re kind to it and you don’t overstress it when it’s so hot and humid out.”
Listen to the full conversation with Ann Swartz on WUWM’s Lake Effect. The interview begins at approximately the 25-minute mark.