If you exercise outdoors on a regular basis, you probably can better handle the heat in August than in early summer. With time, your body has acclimated to the heat. Regardless, you’re still susceptible to heat illness – a dangerous condition that develops when your body temperature gets too high.

The first step in preventing a heat-related illness is to recognize the signs and symptoms when your body temperature is high. You should also be aware of how weather-related factors affect your risk. By following our list of precautions outlined below, you can prevent a heat-related illness from occurring as the mercury rises.

How the Body Handles Heat

While exercising in hot weather, your body temperature rises as a result of both activity and air temperature. In response to this increased heat, a number of thermoregulatory adjustments are made so that you maintain a normal core body temperature of 98.6 F.

To cool the body, the heart shunts more blood to the surface of the skin. In doing so, less blood is available for the muscles, making them fatigue and causing the heart to work harder. If the air is humid, sweat can’t evaporate to cool the body, increasing the load on the heart to pump even more blood. For every degree the body’s internal temperature rises, the heart beats about 10 beats per minute faster.

Under normal circumstances, our bodies effectively manage this process and homeostasis is achieved.

Signs & Symptoms of Heat Illness

If you’re exposed to high temperatures and humidity for too long and you sweat heavily or don’t drink enough fluids, the result may be a heat-related illness. On a hot day, the rate of water loss can be double that on a normal day. When you become dehydrated, problems begin.

Heat illness is a general term for the problems caused by activity in high temperatures. Heat illness runs the spectrum from mild symptoms to a life-threatening condition. The three major forms of heat illness include: heat cramps, heat exhaustion and heatstroke.

Heat Cramps. The mildest form of heat-illness is muscle cramps which are painful muscle contractions that typically occur in the legs (calves, quads) and abdominal muscles. At this point, your body temperature may be normal.

Heat Exhaustion. Nausea or vomiting, weakness, headache, dizziness or confusion are signs of heat exhaustion when the body temperature can rise up to 104 F. Fainting (heat syncope) or sudden loss of strength are also tell tale signs. The skin can be cold, pale and clammy. Cooling the body down is key to prevent heatstroke, a more serious condition.

Heatstroke. The most dangerous form of heat illness, heat stroke is preceded by heat exhaustion and its symptoms. With heat stroke, the skin is hot, dry and red. Other signs may include rapid heartbeat, confusion and loss of consciousness. In this condition, the body temperature is greater than 104 F and is unable to cool itself down. Immediate medical attention is crucial to prevent serious organ damage or even death.

Although heat-related illness is a preventable, this condition affects many active people. According to a July 2011 report from the Centers for Disease Control (CDC), from 2001 to 2009 almost 6,000 people annually were seen in emergency rooms for heat-related illness caused by playing sports or engaging in outdoor activities.

In this study, the most common activities linked to heat illnesses were football and exercise, with about 73 percent occurring among males. Among women 20 or older, the most common activities causing heat illness was exercise followed by bicycling, golf and racquet sports.

Factors Affecting Heat

The primary mechanism in cooling our bodies is perspiration. But, sweating is not what really cools us; it's the action of sweat evaporating. That’s why in drier climates we feel cooler because perspiration can easily evaporate. In humid climates, where the air is more saturated with water, perspiration can’t evaporate, limiting the body’s ability to cool itself. Paying attention to Heat Index and Air Quality Index provide cues as to how hot exercising outside will be on a certain day.

The Heat Index combines air temperature and relative humidity (amount of moisture in air) to determine an apparent temperature. For example, a 90 degree day in the desert will feel like 87.9F. However, in the South, where the humidity is much higher, the apparent temperature will feel more like 101.2F. A Heat Index below 80 will feel comfortable; anything above 90 is considered extreme.

Three different types of heat also affect how hot it feels outside: radiant, convective and conductive. Radiant heat is the increase in heating due to direct sunlight and is transferred without contact between two physical surfaces. An example is running on the beach at noon. Convective heat is the increase in heating due to wind above a certain temperature (72 degrees). If you’ve visited Las Vegas in the summertime, you know firsthand that a hot wind is not cooling. Conductive heat is the increase in heat from contact. If you run on pavement that has been cooked by the mid-day sun, your feet will get hotter with each step on the ground. If you’re planning on exercising outdoors, try to avoid these three sources of heat.

Another helpful number is the Air Quality Index (AQI). Typically, on hot, humid days, the AQI is very poor. The stagnant air caused by heat and humidity traps airborne pollutants like car exhaust. These pollutants react in the presence of sunlight to form ozone, a main ingredient in smog. In real-time, you can check out how clean or polluted your outdoor air is by going to the government website, AIRNow. Air quality forecasts (with ratings from Good to Hazardous) are provided for over 300 major U.S. cities. You should avoid exercising outdoors when the AQI is poor (over 100; in red zone) especially if you have asthma or other breathing problems.

How to Avoid Heat Related Illnesses

You can prevent suffering from a heat-related illness by taking some basic precautions, as indicated below:

Drink Plenty of Fluids. One of the most important things you can do to prevent heat-illness is to drink plenty of fluids. Don’t let thirst be your guide; if you’re thirsty, then you’re probably dehydrated. Drink a glass of water before, during and after your workout. If you’re working out for over an hour and you perspire heavily, then a sports drink that replaces your electrolytes is a good choice (Gatorade, PowerAde). Keep in mind that caffeine and alcohol increase your risk for dehydration.

Watch the Weather Report & Adjust Accordingly. If the weather report reads as the 3 H’s: hazy, hot and humid, it’s a sign that you should change your workout routine. If you love the outdoors, start swimming or visit the local water park with your kids. Perhaps the easiest is to move your workout indoors. Renew your gym membership or attend a yoga class.

Exercise Early or Late. Even if you’re not a morning person, getting up early in the summertime is easier as the days get longer. But, working out in the morning has the added benefit of being cooler especially in hot, dry climates. Exercising in the evening is better than in the afternoon but can still be warm especially if you’re running, walking or biking on black pavement that just cooked for hours in the mid-day sun.

Wear Light Colored/Light Weight Clothing. Avoid dark colored clothing as it absorbs the light more. Stick to light-colored, loose fitting workout clothing made from Coolmax or Dri-Fit. Unlike cotton, these high-performance materials wick sweat away from the body. Invest in high-performance socks that keep your feet dry and cool.

Wear Sunscreen & Use Sunglasses. With sunburn, your body has a more difficult time keeping cool. Avoid sunburn altogether by applying a broad spectrum sunscreen at least 15 minutes before heading out. Opt for a water-resistant sunscreen if you tend to sweat heavily. Wear polarized sunglasses to protect your eyes and a cap to protect your face.

Slowly Adapt to the Heat. If you exercise outdoors year-round, your body will slowly adapt to the heat as spring turns into summer. Even if you’re not accustomed to working out in such high temperatures, your body can adapt in about 14 days. In the meantime, give yourself time to adjust by slowing down or cutting back your routine. Remember, it’s more of a strain on your body to exercise in extreme heat versus biting cold.

Know Your Fitness Level. Those who are physically fit are better able to thermoregulate their body in high heat. But, even fine-tuned athletes are susceptible to heat cramps and heat exhaustion so adjust your exercise routine accordingly. Cut back or pare down on really hot days. If you’re overweight or just starting an exercise routine, start slowly and work toward a more intensive workout program.

Know Your Medical Risks. Young children, seniors and those with medical conditions like cardiovascular disease and diabetes are at greater risk in developing a heat-related illness. Alcohol and other drug abuse also affect your risk.

Beware of Medications. Certain medications such as decongestants, appetite suppressants, antihistamines, antihypertensives and antidepressants can hasten dehydration, which can intensify the effects of heat-related illnesses.

Final Note: Take Care of Fido

Planning on having your dog accompany you for a walk or jog on a hot summer's afternoon? If so, be sure to adopt the same precautionary measures with your pet. Why? Because the factors that affect our risk for heat-illness apply equally to dogs. This is especially true for brachycephalic or “flat-faced” dogs such as bulldogs, pugs, Pekingese and Boston terriers. Dogs with this structure feel the effects of heat faster than dogs with a typical nose or head structure.

While humans and dogs maintain and regulate their own body temperature within a set and safe range, our cooling mechanisms are different. Humans sweat to cool off whereas dogs pant. Just like sweating provides a clue to our body temperature, a dog's breathing provides a clue to his body temperature. Warning signs that he is overheating include heaving as he pants, roaring that sounds like asthma, a tired and distressed look and a floppy/red colored tongue.

To keep your dog safe, take him on an early morning run or walk. If the timing is later, exercise in the shade and stay away from hot pavement as it can burn his paws. And, be sure to carry plenty of water before, during and after exercise for you and your best friend.