It’s summer and much of the population takes advantage of being outdoors. For many, that includes exercising, often in the heat and full sun, which can exacerbate existing medical conditions and bring on other issues if precautions aren’t taken.
Exercising in the heat can cause dehydration. This means there is less fluid in the body and less blood circulating through the body. Exercising causes the body to sweat, resulting in further fluid loss.
“When you’re dehydrated, the body will naturally compensate and increase your resting heart rate,” says Sunal Makadia M.D., F.A.C.C., director of Heart Failure, Sports Cardiology and Cardiac Rehabilitation at LifeBridge Health. “What that means is that people who are dehydrated and perform vigorous activity are prone to higher stresses on their hearts. With exercise, the heart rate can rise quicker, and the increased stress can cause a variety of issues.”
Exercising while dehydrated can result in fatigue much sooner than if fully hydrated, and it can cause people to be lightheaded and pass out. But if the individual already has a heart condition, that can exacerbate problems.
“When people have an underlying cardiac condition, dehydration increases the demands placed on the heart, increasing the person’s risk to experience adverse symptoms, such chest pain and shortness of breath,” Dr. Makadia says.
Exercising increases body temperature in general. Exercising outdoors in the summer heat can increase body temperature even more, resulting in added sweating and dehydration, with the loss of electrolytes in the blood.
“For all people, especially with those with underlying heart conditions, it’s very important to stay cool and to stay hydrated, especially if they’re going to be exercising outside,” Dr. Makadia adds.
When the body’s core temperature rises above 103 degrees Fahrenheit, dangerous conditions can occur such as heat exhaustion which can progress into heat stroke.
“People experiencing heat exhaustion can feel light-headed, dizzy, muscle weakness, confusion, and nausea. Left unrecognized or untreated, heat stroke can occur,” says Dr. Makadia. “Heat stroke is life threatening. Your body becomes so dysregulated, that it cannot control its internal temperature. It can affect the body’s ability to sweat, and can quickly cause collapse and severe organ damage.”
There are many signs to be aware of when exercising outdoors. If you experience any concerning signs, stop the exercise, seek shelter, hydrate and rest.
- Muscle cramps or weakness
- Dizziness or lightheadedness
- Vision changes
Hydrating following or during exercise is important. Keep in mind that water may not be enough. When the body sweats, it removes salt from the body. Replenishing with water fails to replace the sodium that was lost during the exercise. This can make people more prone to cardiac arrhythmias and the symptoms outlined above. Stay hydrated with fluids that contain electrolytes, especially sodium, on a hot day. Some popular sport drinks can include these nutrients.
“Being outside raises your core temperature, you sweat more and you’re more prone to dehydration,” Dr. Makadia explains. “When you start exercising under these conditions, your heart demands more fluid, more blood, more energy. And if you’re starting low to begin with, it’s going to further increase your risk of experience adverse symptoms.”
Any activity that raises the resting heart rate is considered exercise. For some, it can mean taking a brisk walk around the neighborhood. For others, it’s playing sports like basketball or running. Moderate intensity exercise is considered approximately 50% to 70% of a person’s maximum predicted heart rate.
Dr. Makadia suggests other tips for outdoor exercise:
- Avoid the middle of the day. Exercise is safer in the morning or later in the day when the heat is not extreme.
- Start slow when beginning a new exercise or training program. Begin with 10 minutes and work up to a longer duration in future sessions.
- Include ample time for gentle stretching to aid in preparation and recovery to limit muscle cramping and fatigue.
- If possible, drink 4 to 6 ounces of water every 15 to 20 minutes during exercise in the heat and rehydrate, ideally with a small amount of sodium, following the exercise sessions.
- Exercise at a shady park or on a grassy area if possible. Concrete and asphalt surfaces can absorb heat which can raise the temperature around you when you exercise.
- Avoid roadways to limit exposure to pollution and the natural heat emanating from vehicles.
- Wear sunscreen to protect the body from the sun.
Individuals, especially those with a heart condition, should consult their physicians to ensure that the intended exercise is safe for their specific medical condition. Whatever the exercise, Dr. Makadia recommends the general population use the “age predicted heart rate” as a guideline. To calculate: subtract your age from 220 and then take 70% of the remaining number. Stay within 50% to 70% of the maximum heart rate for moderate intensity exercise and 70% to 85% of the maximum heart rate for vigorous exercise intensity. Patients with heart conditions should typically stay within the moderate range, he says.
The amount of time for exercise recommended also varies by individual. Younger people without any major health conditions can safely exercise at a higher heart rate range for longer periods of time, while others who are older, deconditioned, or who may have underlying conditions should aim for shorter durations of vigorous exercise. It’s also about what the body is already accustomed to withstanding.
“People who are accustomed to exercising indoors in a climate-controlled setting are exposed to vastly different elements in the summer heat. This can make it harder for them to exercise,” says Dr. Makadia. “Getting acclimated to the outdoors allows a person to understand what’s going on in their body a little bit better.”
Dr. Makadia suggests beginning exercise outdoors at 50% level – whether in duration of exercise or distance – to ensure the body can adapt to the elements and avoid dehydration.
Those with diagnosed heart conditions, like a recent heart attack or congestive heart failure, should talk to a cardiologist about beginning a cardiac rehab program as a way to start learning about how and what the body, including the heart, is capable of withstanding. Cardiac rehab programs can provide a baseline to building tolerance and increasing time and intensity of exercise.
Editor’s note: This guest post was provided by LifeBridge Health, a #StrongerHearts Life is Why sponsor. To learn more about the #StrongerHeart initiative, visit: https://www.lifebridgehealth.org/StrongerHearts/StrongerHeartsMD.aspx
Wayne, a lifelong Marylander, is the communications director for the American Heart Association serving Baltimore and Greater Maryland. Reach him at firstname.lastname@example.org.