One of the best parts of summer is the opportunity to be active outdoors — whether it’s running, cycling or hiking. It’s also the time when football teams and other fall sports start having workouts and practices. And unfortunately, every year it seems we hear tragic news reported of someone losing their life on the field due to heat stroke, or a runner collapsing at a race.
Exercising in the heat can be dangerous, for all ages.
Why does exercising in hot weather pose a danger?
Exercising under extreme conditions can add significant stress to the cardiovascular system. The dangers of heat overload is compounded if people are not adequately hydrated prior to starting exercise, wear excessive clothing, or are overweight or obese.
Heat-induced problems are common in football, where are number of issues combine — the weight of the padding adds to the work the person has to do; the added work increases the amount of heat build-up and increases sweating and dehydration; and the padding traps the heat.
A similar condition occurs when people are overweight or obese. The added body fat lies over the muscles and effectively traps the heat from escaping.
Considerable metabolic heat is produced during exercise. To reduce internal heat, blood is brought to the skin surface to be cooled. When we sweat, evaporation helps cool the underlying blood. If environmental conditions are favorable, these mechanisms will adequately prevent the body temperature from rising more than about 2-3 degrees F, even during heavy exercise. Heat injuries usually occur when heat loss is compromised, as when wearing heavy clothing.
During exercise in the heat, dissipating internal body heat is more difficult, and external heat from the environment may add to the total heat load. This results in a higher heart rate than normal at any level of exercise.
A hot, humid environment is the most stressful one for exercising. When the air contains a large quantity of water vapor, sweat will not evaporate readily. Since sweat/evaporation is the most efficient mechanism for cooling the body, adequate cooling may not occur in humid conditions.
Under these conditions, heat exhaustion and heat stroke become dangerous possibilities.
What are the symptoms of heat exhaustion and heat stroke?
Muscle cramping might be the first sign of heat-related illness, and may lead to heat exhaustion or stroke. According to the Centers for Disease Control and Prevention, here is how you can recognize heat exhaustion and heat stroke and what to do.
Symptoms of heat exhaustion
- Heavy sweating
- Cold, pale, and clammy skin
- Fast, weak pulse
- Nausea or vomiting
What you should do:
- Move to a cooler location.
- Lie down and loosen your clothing.
- Apply cool, wet cloths to as much of your body as possible.
- Sip water.
- If you have vomited and it continues, seek medical attention immediately.
Symptoms of heat stroke
- High body temperature (above 103°F)
- Hot, red, dry or moist skin
- Rapid and strong pulse
- Possible unconsciousness
What you should do:
- Call 911 immediately — this is a medical emergency.
- Move the person to a cooler environment.
- Reduce the person’s body temperature with cool cloths or even a bath.
- Do NOT give fluids.
How to stay safe while exercising in the heat
The American Council on Exercise offers the following tips for exercising in the heat:
- Start slowly. Begin exercising in the heat gradually. Becoming acclimated to exercising in the heat takes approximately seven to 10 days. Start by exercising for short periods of time each day.
- Think light. Wear light-colored clothing if exercising in the sun, as white reflects heat better than other colors.
- Wear breathable clothes. Always wear lightweight, well-ventilated clothing. Never wear impermeable or non-breathable garments.
- Stay hydrated. Replace body fluids as they are lost. Drink fluids at regular intervals while exercising, but avoid over-hydration, which can be as dangerous as dehydration. Frequent consumption of small amounts of fluid to minimize sweat-related weight loss is the best practice. Rehydration with water (rather than sports drinks) is adequate except under extreme conditions where greater than 3% of a person’s body weight is lost. Read: Soda worsens dehydration
- Keep air moving around you. Air movement is critical for adequate cooling, and facilitates heat loss. Even in cool conditions, if there is limited air movement (such as exercising indoors on a treadmill or cycle), the microclimate next to the body can become the same temperature as the body and saturated with water vapor from sweat. This will prevent adequate heat loss and put the exerciser at risk of a heat injury.
And be sure to take some common-sense precautions such as limiting outdoor activities to only before noon and after 6 p.m., and stop and come inside whenever you feel overheated. It’s important to teach children to do this as well.
Do you exercise outdoors in the summer? Have you or a loved one ever had symptoms of heat exhaustion or heat stroke? Please share in the comments.
Information sources: “Essentials of Exercise Science for Fitness Professionals,” American Council on Exercise, 2012; The Centers for Disease Control and Prevention, https://www.cdc.gov/extremeheat/warning.html.
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