Yes, exposure to extremes of heat, cold, and high altitude, and air pollution alters physiological responses to exercise and impairs physical performance.

Exercising in the Heat
Exercising in warm weather or environments can be safe if you know how to adjust your exercise program or physical activity to the conditions. It is important to note that serious heat illness is more likely to occur in people who are overexerting and not as well conditioned.

When exercising, you are exposed to external and internal heat. External heat comes from a combination of environmental temperature and humidity, known as the heat index . Humidity decreases the effectiveness of sweat evaporation to cool you. Heat radiation from surfaces such as pavement, concrete, or sand may make you feel hotter.

With exercise, internal heat production increases as much as 15 to 20 times more than resting levels. This is dependent on fitness levels, body surface, exercise parameters (intensity and duration, clothing worn, and state of hydration.)

Sweating is important and is controlled by the thermostat in your brain, the hypothalamus, which senses body temperature rise and sends signals to dilate blood vessels near the body surface. Approximately 85% of heat loss is through sweat. Adequate fluid intake allows the body to maintain a cooling balance through sweating.

When your body fails to regulate its internal temperature, you can suffer from heat cramps, heat fatigue, heat exhaustion or heat stroke. Be aware of these symptoms:

Heat Cramps:
Cramps in the legs, arms and stomach. To treat, stop exercising, cool down, massage the cramps, and drink plenty of fluids (avoid salt). The body's thermoregulatory responses are intact.

Heat Fatigue:
Weakness, dizziness, headache, rapid pulse and low blood pressure. The body still sweats but contains less fluid. To treat, stop exercising, get out of the heat, and apply ice packs to your armpits and groin area.

Heat Exhaustion:
More pronounced weakness and dizziness; cold, clammy skin; headache, mental confusion, rapid, weak pulse, and a temperature as high as 104 degrees. The body is unable to regulate heat. Hospitalization/intravenous fluids and cooling measures are required.

Heat Stroke:
The body loses its ability to sweat, with the temperature rising as high as 106 degrees. Symptoms include the following: disorientation, loss of coordination, hot dry skin with no sweating, rapid pulse, vomiting, diarrhea, and unconsciousness. Immediate cooling and hospitalization is required.

Chart numbers represent perceived temperature

Common Sense Tips for Exercising in the Heat

• Allow 14 days for your body to acclimate if you are in a new environment. Reduce the intensity of your exercise by half of your regular exercise intensity and then slowly increase it over a 2 week period.
• Drink plenty of fluids. Clear urine and a full bladder every 2 to 3 hours indicate adequate hydration.
• Avoid caffeine and alcohol, which act as diuretics. Also avoid carbonated or sugary drinks, because they might slow fluid absorption.
• Do not wait till you are thirsty to drink. Drink as often as you can before your workout, and try to drink 5 to 10 ounces of water every 15 minutes while exercising.
• Exercise during the coolest part of the day before 10 A.M. or after 6 P.M.
• Pay attention to the heat index, the combination of heat and humidity.
• Exercise on cool surfaces like grass or white concrete instead of black pavement.
• Wear light colored, breathable clothing such as cotton. Dress in layers.
• In humid weather when the sweat is not evaporating, carry a towel to wipe the sweat away.
• If you start to feel the effects of heat illness, stop your workout, seek shade and start drinking fluids.
• If you take medication, check with your doctor before exercising. Some medicines can interfere with the body's ability to regulate its internal temperature.

Exercising in Cold Weather
Howling winds and freezing temperatures do not mean you have to give up outdoor exercise until spring. When you are prepared for it, outdoor winter exercise can be healthy and invigorating.

Hypothermia is a drop in body temperature and can be potentially fatal. Death usually is the result of heart failure.

In colder temperatures, the heart tolerates less exertion because the body reacts to cold by constricting small arteries. This reduces the loss of body heat by shifting the warm blood away from the skin surface. When this natural phenomenon occurs the heart must work harder to pump blood through the narrowed arteries. The extra load on the heart decreases its capacity to respond to exercise. Inhalation of cold air and exposure of the hands to cold may cause reflexive coronary artery constriction, reducing the supply of oxygen containing blood to the heart muscle. In either case, angina may be felt.

Wind, snow, rain, and cold temperatures are all factors that can steal your body heat. Wind serves to remove the layer of air your body has heated. (See wind chill chart below.)

Remember, you still have the capacity to sweat when you are working out in the cold. Cotton absorbs moisture, which cools the body. Instead, use as the first layer fabrics that help moisture evaporate by drawing it away from the body, such as silk, nylon or polypropylene. A cotton material can serve as the second layer to absorb the moisture. Wool is also a good material to wear because it is warm even when wet.

Common Sense Tips for Exercising in the Cold

• When outdoors, avoid sudden exertion. Warm up first. In cold weather, the muscles take longer to stretch out.
• Wear layers, and jackets that can be unzipped or buttoned. This will allow excess heat to dissipate without you having to remove your clothing in cold weather.
• Wear a hat and scarf. As much as 40% of the body's heat can be lost through the head. Keeping the hands and feet warm will also prevent heat loss. Wool socks and heavy shoes are essential.
• Avoid alcoholic beverages before going outside in the cold. The initial sensation of warmth is caused by surface blood vessels dilating which is drawing warmth away from the body's vital organs.
• Go inside and get warmed up when cold.
• Cover your mouth, nose and throat. When the temperature drops so does the amount of moisture in the air. When breathing in cold air, some will have a reflex coronary artery constriction, that may result in angina.
• Cover your hands with mittens or gloves whether shoveling snow or going out to start the car. Certain individuals experience reflexive coronary artery constriction that may cause angina.

Exercise and Air Pollution
Although air pollution may not be as much of a problem in rural areas, it is a major problem in most large metropolitan areas. Your lungs may be exposed to pollutants such as ozone, carbon monoxide, sulfur dioxide, and sulfuric acid. Exercisers breathe more heavily and will more likely inhale more pollutants than nonexercisers. Some common symptoms experienced include dizziness, shortness of breath, throat irritation, difficulty breathing, and excessive coughing during or immediately after the workout. Those with asthma, other lung disorders, or heart disease will be more vulnerable to experiencing these symptoms.

Even though air pollutants will have different effects on the body, they all reduce the body's ability to utilize oxygen. Almost all the oxygen in one's body is transported through the blood by hemoglobin. Carbon monoxide, for example, which is emitted from car exhaust, has a much greater attraction to hemoglobin than oxygen. Therefore, when there are high concentrations of carbon monoxide, the oxygen supply to the body is reduced, which greatly reduces your working capacity.

Common Sense Tips for Exercising in Polluted Air

• Minimize exposure by exercising in the early morning or evening hours.
• Avoid exercise on heavily congested streets or between 12 noon and 4 P.M.
• Air currents can disperse pollutants, so it is better for you to exercise in open, windy locations.
• If there is an air pollution alert in your area, try to work indoors.
• If you cannot avoid exercising in pollution, keep your workouts light and short. Wear a protective mask, covering nose and mouth, to decrease the percentage of polluted air breathed.
• If you suffer from asthma or lung disease, in addition to your heart disease, try scheduling your workouts indoors until pollution levels drop.

Exercise and Altitude Changes
Iowa's elevation ranges from 480 feet (Osceola County) to 1670 feet (Lee County) above sea level. Its elevation does not present a problem when exercising. But if you vacation in an area that is at a higher altitude you should be aware that your exercise or working capacity is inversely related to the altitude. In other words, the higher the altitude, the lower your ability to work at the same intensity level. This is because the pressure exerted by oxygen at high altitudes is less than at sea level. As a result, it is more difficult for the body to deliver oxygen to the working muscles. At an altitude of 7500 feet above sea level, your ability to obtain oxygen is diminished by 12.5 percent.

Acute mountain sickness can be acquired at altitudes greater than 5000 feet above sea level, so you need to be aware of its symptoms. They include headache, unusual shortness of breath at rest or with exertion, malaise, loss of appetite, nausea or vomiting, abdominal pain, and / or diarrhea. These symptoms also often occur when you are rapidly ascending to a higher altitude.

Common Sense Tips When Exercising at Increased Altitudes

• Travel is safe between the altitudes of 3000 to 9000 feet above sea level for most individuals. Because of your cardiac condition, you should consult with your CHAMPS staff and physician before traveling to higher altitudes.
• Reduce the intensity of your exercise workout and be conservative for the first several days of exercising in higher altitudes. Pay attention to your RPE. The body starts to adapt to the stress of a particular altitude and it partially acclimatizes after 2 to 3 weeks.

Exercise and Fluid Replacement
The body has about 2.5 million sweat glands. Because the total body is composed of 60% water and the muscles 70% water, drinking fluids is vital for digestion, tissue building, lubrication and temperature control.

Exercise increases the body's metabolic rate and its production of energy. The total amount of heat produced depends upon both the intensity (how hard) and duration (how long) of the exercise bout. The harder you work the faster the rate of heat production, while the longer you exercise the greater the total heat produced. Humans have several avenues of heat loss available to them: conduction, convection, radiation and evaporation. Evaporation involves heat loss through the vaporization of sweat. Sweat is primarily water but it does include a number of important electrolytes (such as sodium and chloride). Typically, when substances are lost via sweat, it is more important to replace water than electrolytes. This is true especially when competing or vigorously working out for long periods of time. The composition of the replacement drink and what quantities and intervals the fluids should be consumed are especially important if you are vigorously exercising for more than an hour.

Ways to prevent excessive fluid losses are allowing yourself to accommodate to the environment. Training itself will increase blood volume, thus reducing the impact of dehydration on blood volume. In addition, training in the heat produces an earlier onset of sweating during exercise thus fostering cooling, and results in a more dilute sweat, thereby conserving electrolytes.

Common Sense Tips with Exercising Related to Fluid Replacement

• Note color of urine. Darker color may indicate the onset of dehydration and the need to replenish fluids.
• Avoid carbonated drinks, which can cause gastrointestinal distress and may decrease the volume of fluids consumed.
• Avoid beverages containing alcohol or caffeine. They are diuretics and tend to contribute to fluid loss.
• An optimal fluid replacement beverage should taste good, stimulate fluid absorption, maintain proper fluid balance in the body, and energize working muscles.
• Water is a good source of replenishment for exercise lasting less than one hour.
• Keep in mind that the thirst mechanism is not precise. By the time you feel thirsty, you are probably well on the way to becoming dehydrated. Fluid replacement is just as important in cold weather.

For the more competitive exerciser

• Drink 16 ounces of a cold beverage (40-50 degrees F) thirty minutes before competition.
• The beverage should contain 6-8% carbohydrate and less than 280 mg sodium and less than 200 mg of potassium per quart.
• Drink 6-8 ounces of the beverage at 10-15 minute intervals during the competition.

Title Page