THE SPORTS DOCTOR

IF YOU CAN’T STAND THE HEAT

THE DANGERS OF WARM WEATHER EXERCISE

By dr. miChael l. groSS

The hottest days of summer are upon us. While your head won’t pop open with steam, special care should be taken while exercising to avoid the hazards of overheating. As the temperature and humidity rise, so does the incidence of environmental heat-related exertional illnesses.

Understanding hot weather dangers and precautions is very important for elite athletes, recreational exercisers and weekend warriors. Some of the dangers include sunburn, dehydration, hyponatremia, heat cramps, heat exhaustion and, at the most, extreme heat stroke.

Exercising in hot weather puts extra stress on your body systems. If you don’t take proper steps when you exercise in the heat, you risk serious injury or illness. Both the exercise itself and the air temperature increase your core body temperature. To help keep cool, your body pumps more blood to circulate near the skin. This leaves less blood to pump to the muscles, which are already working hard, so this increases your heart rate. If you are exercising in humid conditions, this causes another problem. Evaporating sweat from your skin is a major tool for cooling your body. Because sweat doesn’t readily evaporate from your skin in humid weather, your body faces further stress. This pushes your body temperature even higher.

Under normal conditions, your skin, blood vessels and perspiration level adjust to the heat. Normally, sweating regulates our body temperature. However, several factors can limit the sweat mechanism, including intense exercise in high temperatures or high humidity, age, obesity, fever, dehydration, illness, medications and alcohol. When an athlete develops a heat illness, it usually occurs after prolonged exertion and excessive sweating that leads, first to dehydration and then to electrolyte imbalances. But, if you are not in shape or if you have any of the above risk factors, this process can develop quickly. In addition, the hotter and more humid it gets, the greater the risk. Natural cooling systems will fail if you’re exposed to high temperatures and humidity for too long, especially if you sweat heavily and you don’t drink enough fluids. The result may be a heat-related illness. Heat-related illnesses occur along a spectrum, starting out mild but worsening if left untreated.

Heat illnesses include: Sunburn. Sunburn decreases your ability to cool yourself and causes fluid loss. Repeated sunburn increases your risk of permanent skin damage, premature aging and skin cancer.

Dehydration. Dehydration refers to an inadequate amount of fluid in the body. Among athletes who participate in endurance sports or long workouts, dehydration can occur quickly. In general, a person is considered dehydrated when they have lost more than 2 percent of their body weight during exercise. Athletes need to stay hydrated for optimal performance. Studies have found that a loss of two or more percent of one’s body weight due to sweating is linked to a drop in blood volume. When this occurs, the heart works harder to move blood through the bloodstream. This can also cause muscle cramps, dizziness and fatigue and even other heat illnesses.

Hyponatremia. This is most commonly associated with prolonged exertion during sustained, high-intensity endurance activities, such as marathons or triathlons. In most cases, it is attributable to excess free water intake, which fails to replenish the sometimes massive sodium losses that result from sweating. Symptoms of hyponatremia can vary from light-headedness, malaise, nausea, to altered mental status. Risk factors include hot weather, female athletes/exercisers, poor performance and possibly the use of nonsteroidal anti-inflammatory medications.

Heat cramps. Heat cramps are painful muscle contractions, mainly affecting the calves, quadriceps and abdominals. Affected muscles may feel firm to the touch. Your body temperature may be normal.

Heat exhaustion. With heat exhaustion, your body temperature rises as high as 104 degrees Fahrenheit (40 degrees Celsius) and you may experience nausea, vomiting, headache, fainting, weakness and cold, clammy skin. If left untreated, this can lead to heatstroke.

Heatstroke. Heatstroke is a life-threatening emergency condition that occurs when your body temperature is greater than 104 degrees Fahrenheit (40 degrees Celsius). Your skin may be hot, but your body may stop sweating to help cool itself. You may develop confusion and irritability. You need immediate medical attention to prevent brain damage, organ failure or even death.

During hot-weather exercise, watch for signs and symptoms of heat-related illness. If you ignore these symptoms, your condition can worsen, resulting in a medical emergency. Signs and symptoms include muscle cramps, nausea or vomiting, weakness, headache, dizziness and confusion.

If you develop any of these symptoms, you must lower your body temperature and get hydrated. Stop exercising immediately and get out of the heat. If possible, have someone stay with you who can help monitor your condition. Remove extra clothing or sports equipment. Drink fluids (water or a sports drink). If possible, fan your body or wet down your body with cool water. If you don’t feel better within 30 minutes, contact your doctor. If you have signs of heatstroke, seek immediate medical help.

Once you’ve had heatstroke, you’re at a higher risk of getting a heat illness again. Get cleared by your doctor before you return to exercise if you’ve had heatstroke.

When you exercise in hot weather, keep these precautions in mind:

Watch the weather. Pay attention to weather forecasts and heat alerts. Know what the temperature is expected to be for the duration of your planned outdoor activity. More important than temperature alone, is the heat index, the combination of air temperature and humidity that gives

a description of how the temperature actually feels. This is not the actual air temperature. Most weather reports include the heat index along with the temperature. When the heat index is at or over 90 degrees Fahrenheit, extreme caution should be considered before exercising outdoors.

Get acclimated. If you’re used to exercising indoors or in cooler weather, take it easy at first when you exercise in the heat. As your body adapts to the heat over the course of one to two weeks, gradually increase the length and intensity of your workouts. Acclimate to exercising outdoors, altitude and physical condition. General rule of thumb is 10-14 days for adults and 14-21 days for children (prepubescent) and older adults (> 60 years). Children and older adults are less heat tolerant and have a less effective thermoregulatory system.

Know your fitness level. If you’re unfit or new to exercise, be extra cautious when working out in the heat. Your body may have a lower tolerance to the heat. Reduce your exercise intensity and take frequent breaks.

Drink plenty of fluids. Dehydration is a key factor in heat illness. Help your body sweat and cool down by staying well-hydrated with water. Hydrate your body before, during and after your workout. Don’t wait until you’re thirsty to drink. If you wait until you’re thirsty, it’s usually too late. Monitoring your weight loss and ingesting chilled volumes of fluid during exercise at a rate equal to that lost from sweating is a better method to preventing dehydration. If you plan to exercise intensely or for longer than one hour, consider a sports drink instead of water. Sports drinks can replace the sodium, chloride and potassium you lose through sweating. Avoid alcoholic drinks because

Rapid fluid replacement is not recommended for rehydration. Rapid replacement of fluid stimulates increased urine production, which reduces the body water retention.

Individuals involved in a short bout of exercise are generally fine with water fluid replacement of an extra 8-16 ounces. A sports drink (with salt and potassium) is suggested for exercise lasting longer than an hour, such as a marathon, and at a rate of about 16-24 ounces an hour depending upon the amount you sweat and the heat index.

Replace fluids after long bouts of exercise (greater than an hour) at a rate of 16 ounces of fluid per pound of body weight lost during exercise.

Dress appropriately. Lightweight, loose-fitting clothing helps sweat evaporate and keeps you cooler. Try cotton or “wicking” fabrics, which move sweat away from your body. Avoid dark colors, which can absorb heat. If possible, wear a light-colored, wide-brimmed hat.

Avoid midday sun. Exercise in the morning or evening when it’s likely to be cooler outdoors. Hit the streets before 10 a.m. and after 3 p.m. Another stay-cool tip: Run or walk on dirt paths instead of sun-absorbing pavement. If possible, exercise in shady areas or do a water workout in a pool.

Wear sunscreen. Use a sunscreen with a rating of at least SPF-15 dependent upon skin type, even on cloudy days. Re-apply every 2 hours. Use an oil-free formula that won’t interfere with your body’s ability to cool itself down and select a sweat-proof variety to prevent sunscreen from irritating your eyes. Clothing with tight weaves, sunglasses and a lightweight hat with a brim can also help block the sun’s harmful rays.

Listen to your body. If you notice any symptoms of heat illness, stop your workout. It’s not a good idea to “push yourself” in extreme heat. If you feel bad, use common sense and discontinue your workout.

Know your choices. If you’re concerned about the heat or humidity, stay indoors. Work out at the gym, walk laps inside the mall or climb stairs inside an air-conditioned building.

It is important to prepare ahead of time for exercise in extreme heat. Wear clothes that are lightweight, light-colored and breathe easily to allow for proper ventilation of the skin, apply sunscreen on any exposed skin and drink lots of water. If possible, avoid the peak hours of the day as the temperature is at its highest, and when you do begin, start slowly and gradually pick up the pace to allow your body to get accustomed to the heat. On extreme days stay indoors and stay cool. When the weather gets hot, we all want to exercise outside. A little knowledge and care can prevent serious injury and keep us fit.

Michael L. Gross, MD is the founder of Active Orthopedic and Sports Medicine in Hackensack. He is the section chief of sports medicine at Hackensack/Meridian University Medical Center and an assistant professor at Hackensack Meridian School of Medicine.

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