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How does the body accomplish what we ask it to do? The body is like an internal combustion engine. It burns fuel and oxygen for energy just as your car engine burns gasoline mixed with oxygen. Just like a car, the body gives off heat as it burns energy. This is why your body temperature rises when you exercise. And, like a car, it gives off waste products as it uses this energy.
Your body utilizes carbohydrates in the diet as its energy source. It converts complex carbohydrates--such as breads, grains, potatoes, and other starches--and sugars in the diet to a fuel substance called glycogen. Glycogen is stored in muscle cells and in large amounts in the liver. The glycogen in muscles combines with oxygen, brought in by the circulating blood from the lungs, and releases energy; this is known as the aerobic energy cycle. The waste products are carbon dioxide and water.
Once the muscle glycogen is exhausted from prolonged exercise, reserve glycogen is released from the liver and carried to muscle cells so that they can continue working. This glycogen release continues until the body's supply of glycogen is totally depleted. At this point, you are basically out of gas.
However, the body has another reserve fuel supply to enable it to keep chugging on. It changes fuels and begins to burn fat instead of glycogen. This is a whole new energy cycle, called the anaerobic energy cycle, in which the waste product released is lactic acid.
The body can easily rid itself of carbon dioxide and water, but it has difficulty getting rid of lactic acid. As you continue to exercise, lactic acid begins to build up in the muscle, and you become more fatigued. This buildup of lactic acid is what causes the burning pain in exhausted muscles and most of the soreness and stiffness you feel the next day.
The longer you can prevent the body from converting to the anaerobic energy cycle, the longer you can put off fatigue and continue to perform at a high level. Thus, you must either improve the supply of oxygen to the muscles or prevent the exhaustion of glycogen reserves. Conditioning the heart can increase the efficiency of oxygen transfer to the muscles. And to keep glycogen stores high, complex carbohydrates should form the bulk of your diet.
The previous chapter gave you specific dietary advice. This chapter looks at the other principles that keep your human engine running smoothly:
Your body has three ways to shed this excess heat: radiation, convection, and evaporation.
In radiation, the increase in body temperature causes the blood vessels in the skin to dilate. This pooling of blood is the reason your skin turns red when you exercise. Large quantities of blood rise to the skin surface, where heat can be radiated to the outside to cool off the body. The problem with radiation is that exercising muscles demand large quantities of blood to supply oxygen and fuel. This reduces the amount of blood available to the skin, so radiation becomes less effective.
Convection relies on the difference between the body's temperature and the air temperature to transfer heat from the body. The closer the air temperature is to 98.6º F (normal body temperature), the less heat is drawn off the body. So as the weather gets hotter and you need to lose more heat, this mechanism becomes less efficient.
We depend mainly on evaporation for temperature control in hot weather. As sweat evaporates, it cools the skin. In hotter weather you sweat more, so this system works well in high temperatures. But if the humidity is high, there is more water in the air, and less sweat is absorbed from the skin through evaporation. With no evaporation, there's no cooling. So exercising on a humid day can be more dangerous than exercising on a hot day. Also, if you keep perspiring without replacing body fluids, you become dehydrated. Since sweat is salty, excessive sweating leads to loss of body salts and potassium, which collectively are called electrolytes.
What you wear while exercising also affects this heat reduction mechanism. If you cover your body with clothes, as football players do from head to toe, or if you wear clothes that don't "breathe," that is, that don't allow sweat to evaporate from the body, you put yourself at risk for a heat problem, either heat exhaustion or heat stroke.
Heat exhaustion is due to dehydration and the loss of electrolytes. It causes you to feel lightheaded and dizzy, and you may even faint. Your cooling mechanisms are working overtime so that you are sweaty, and your skin is cool and clammy. You may also have severe muscle cramps due to the loss of salt and potassium. If you experience these symptoms, stop whatever you are doing, rest in a cool place, and replace your fluids with water or an electrolyte drink such as Gatorade. In severe cases, you may need to have fluids and electrolytes replaced intravenously at a hospital emergency room.
Heat stroke is a true medical emergency. In this case, all of the heat mechanisms have failed, and the body temperature has risen to the point where the brain's regulating mechanism has been knocked out. Body temperature may go as high as 107º to 109º F. The symptoms of heat stroke are red, hot skin; lack of sweating; and, usually, loss of consciousness. Get someone with heat stroke to the emergency room immediately, where an ice bath, ice packs, or a cooling blanket can be used to help lower the body temperature. Someone with heat stroke could die very quickly without treatment.
How can you prevent these heat problems? First, check the temperature and humidity before you exercise. If the temperature and humidity are both high, cut back on your workout for that day or wait till the temperature and humidity have gone down. Wear light, loose clothing that breathes and allows air to circulate.
Second, keep your fluid intake up. Take frequent water breaks, every 15 minutes if possible. You should drink plain water even if you're not thirsty. By the time you become thirsty, it may be too late. You can also drink an electrolyte drink, such as Gatorade, but remember to dilute it, using at least two parts water to one part Gatorade, to help your stomach absorb the high concentration of electrolytes.
Third, do not take salt tablets; they only create more problems. A large amount of salt in the intestines causes the body to extract large amounts of water from body tissues to dilute it, causing further dehydration in the muscles. Adequately salted meals and high-potassium foods, such as bananas, tomatoes, and oranges, should be adequate to maintain your electrolyte levels.
Exercise is essential in maintaining the body's overall well-being. Even modest amounts of exercise can substantially reduce your chances of dying of heart problems, cancer, or other diseases.
Certain well-known risk factors lead to heart disease, including obesity, high blood pressure, high cholesterol, low levels of the "good" (HDL) cholesterol, diabetes, cigarette smoking, and family history of heart disease. Exercise has a dramatic effect on almost all of these risk factors:
The only heart disease risk factor that exercise can't conquer is family history. But even if you have a high incidence of heart disease in your family, you can still reduce the other risk factors and be less likely to suffer from heart disease or a heart attack.
The heart is, after all, a muscle, and any muscle can be strengthened by exercise. The stronger the heart gets, the more easily it can do its job--pumping blood to the rest of the body. A well-conditioned heart has a low resting heart rate. The fewer times it has to beat each minute, the less strain is put on it. And a well-conditioned heart is better able to meet the sudden demand of a burst of activity, such as running for a bus or shoveling snow.
The entire theory behind conditioning the heart is extremely simple. You need to know just two basic terms: predicted maximum heart rate and training range.
The predicted maximum heart rate is the highest number of beats per minute that is safe during any one exercise period. There are two ways to determine this rate. You can undergo a fancy exercise stress test at a cost of $100 to $150, or you can calculate your maximum heart rate with a simple formula: 220 minus your age. For example, a 40-year-old would have a predicted maximum heart rate of 180 beats per minute.
The heart rate must be brought into the training range, which is 70-85 percent of the maximum. This is the heart rate that best conditions the heart. So a 40-year-old, with a predicted maximum heart rate of 180, would have a training range of 126 to 153 beats per minute.
Now the only trick is how to monitor your heart rate. You can buy a heart rate monitor, complete with chest strap and wrist monitor, for $130 to $300. Or you can simply time your pulse. The easiest place to take your pulse during exercise is at the side of the throat, where the carotid artery beats forcefully. Place your index and middle fingers at the base of the neck on either side of the windpipe (see the following figure) and count your heartbeats for 10 seconds. Multiply this number by 6. This tells you the number of heartbeats per minute. Then you can check whether this heart rate falls within your training range.
The type of aerobic activity you choose makes no difference as long as you attain the training range. At the minimum, you need to keep your heart rate in the training range for at least 20 minutes three times a week.
However, recent research shows that even less exercise--12 minutes three times a week--can produce health benefits. This landmark study, carried out by the Institute for Aerobics Research and the Cooper Clinic in Dallas, one of the first large studies to look at women's fitness as well as men's, shows that you can benefit from being just a bit more active. So if you have time for only a short workout, go for it. A little exercise is better than none at all.
If you have any history of heart trouble or orthopedic problems that might make exercise dangerous, see your doctor for a physical exam before starting a program. It was once recommended that any man age 40 or over have an exercise stress test before beginning a rigorous exercise program. However, I now order stress tests only for people who have several heart disease risk factors. Age is not as much a risk as is jump-starting an unconditioned heart. If a sedentary person's heart is only borderline healthy, a conditioning program could put him or her at risk of a heart attack.
Use some common sense when beginning an exercise program. Start slowly and gradually build up to 20 minutes or more during each session. Don't go out for 20 long, hard minutes your very first day. See the section on gradual conditioning on page 7.
When you constantly train at the high end of your target heart rate, you risk problems with fatigue, muscle injury, and stress. Trying to work out like an elite athlete can run you into the ground.
"No pain, no gain" is not the best way to condition yourself. Fatigue and injuries can result from pushing yourself too hard. You will find that you can achieve better results by cutting back on your exercise intensity. For example, running more than 40 miles a week can triple your likelihood of sustaining an injury. So decreasing your mileage to less than 40 per week will help prevent injuries and ultimately keep you running longer.
Overtraining may also increase your susceptibility to colds. Several studies have shown that intense daily training reduces resistance to infectious diseases such as colds and the flu.
In addition, long training sessions may actually slow you down. One study of U.S. college swimmers found that those who swam up to 10,000 meters twice a day lost arm strength and power. After the swimmers tapered their training to 2,700 meters a day for a few days, they recovered their arm power. Thus, too much training may cause you to burn out and prevent you from reaching your goals.
High-intensity training may also counteract the good feelings you get from exercising. Exercise is a great way to reduce stress and anxiety and to lift your mood. But the same swimming researchers found that increasing training intensity and distance at the end of the season made the swimmers feel more tense, depressed, and angry.
Exercise shouldn't be a chore. It should be fun. If your workout feels like work, change your training schedule or try some new type of exercise that reinvigorates you. One of the advantages of cross-training is the use of more than one sport to keep you physically and mentally active. A bored but well-conditioned athlete won't perform up to par.
Almost all sports are based on competition. Even the recreational jogger or health walker will try to attain his or her personal best and go a little farther or faster, and the individual weight trainer try to get in one or two extra repetitions of a weight workout. Striving to reach peak performance is fine until you push yourself past your capacity. This usually occurs at the end of activity, when your muscles are tired and more prone to injury.
There will be days when you feel really good as an athlete and believe that you can do more than you usually do. Despite this euphoria, however, your body may not in fact be capable of suddenly doing the extra exercise. The result often is an injury.
The opposite side of the coin is trying to force yourself to perform on a bad day. Refusing to recognize a bad day also can lead to overfatigue and injury. When you're not feeling up to par, just do what you can comfortably accomplish and leave it at that. Tomorrow will be a better day.
Exercise is very helpful in alleviating stress, releasing tensions, and producing a relaxing kind of fatigue. However, some people go far beyond this normal response and become dependent on daily exercise.
One of the by-products of exercise is the production of naturally occurring brain chemicals called endorphins. These morphinelike substances produce a sense of well-being and relaxation and are responsible for the "runner's high." Some people become addicted to daily exercise because of the production of these chemicals. If they don't exercise, they become depressed and irritable, and they may actually have withdrawal symptoms. If they become injured, they will make life miserable for everyone around them until they can get back to exercising daily.
Many athletes refuse to take time off because of their drive to keep pushing themselves. I often hear athletes say, "I laid off exercise for three days when I pulled a hamstring, but it didn't get better." It can be difficult to get the message across that a hamstring pull may take three weeks to heal. The athlete just doesn't want to hear it.
And once treatment begins, I inevitably hear: "Do I have to stop, or can I keep playing?" This mental outlook often interferes with even the best treatment because the athlete will try to play before he or she is ready.
In this era of drug abuse, a new problem has become widespread: the use of anabolic steroids among high school and college athletes. Steroids are the most dangerous group of legal prescription drugs besides the poisonous chemicals used to treat cancer. These drugs are widely available through an underground black market, mostly through weight-lifting gyms. But even in suburban health clubs, the guys in the weight room commonly know where to find steroids.
An increasing number of teenagers are using steroids to enhance their athletic performance and their appearance. An estimated 260,000 teens, mostly boys in grades 7 to 12, use or have used steroids, according to a survey by the National Institute of Drug Abuse. Another study by Penn State and the American Medical Association puts the figure closer to 400,000.
Steroids have become a major problem among high school and college football players. During football season, in the course of examining high school athletes for injuries I spot one or two players a week who are taking steroids. About 10 percent of college football players admit that they use steroids, mostly to improve athletic performance, according to a National Collegiate Athletic Association poll. Even nonathletes concerned about body image are turning to steroids. In fact, this is the group with the largest increase in steroid use.
Steroids have a wide variety of side effects. The excess of male hormones circulating in the blood can cause a personality change toward increased aggressive behavior. Part of the increase in strength attributed to steroids is due to this aggressiveness; the athlete lifts more because he attacks the weights harder. This aggressiveness may lead teenagers to get into fights and become hard to handle. In high doses, steroids have been reported to cause psychotic episodes.
One of the more serious side effects of steroids is on male reproductive organs. Because of the high level of circulating testosterone, the testicles no longer need to manufacture this hormone, so they begin to shrink. This reduces sperm production and may lead to both impotence and sterility.
In addition, steroids lead to changes in the structure and function of both the kidneys and the liver. These changes can cause chronic health problems in later life and markedly increase the risk of liver cancer.
I believe that the anecdotal reports of heart attacks among athletes will eventually also be linked to steroid use. The incidence of coronary artery disease and heart attacks among 20-year-old steroid users is now being documented. The drug causes a marked rise in total cholesterol levels and a marked drop in levels of HDL cholesterol. Low HDL levels mean that there is nothing to prevent deposits from clogging arteries, including those in the heart. Also, degeneration of the heart muscle itself has been identified in steroid users. This change is irreversible, leaving a heart transplant as the only viable treatment.
Steroid users may also develop a severe form of acne over the upper torso and become prematurely bald. They also are more susceptible to injuries of the bones and tendons because these support structures aren't strong enough to anchor overdeveloped muscles.
I see these problems mostly among football players, shot-putters, discus and hammer throwers, wrestlers, weight lifters, and body builders. If the steroid use is not too prolonged, some of these side effects will reverse themselves once the user stops taking the drugs. However, many problems, such as hair loss and heart problems, are not reversible.
A relatively new group of steroid users are female body builders. More muscular female body builders tend to win more competitions. Women can strengthen their upper bodies with weight training, but the only way to bulk up these muscles is by taking male hormones.
Female body builders not only suffer the same side effects as men, but they also lose breast tissue, develop deeper voices, undergo changes in the structure of their reproductive organs, and grow hair on their faces. None of these changes is reversible. Women on steroids also stop having periods, which is reversible when the steroids are discontinued.
Is it fair for an athlete to compete against another who is artificially built up? I don't think so. Young athletes tell me, "I have to take steroids because the guy across the line is bigger than me." However, when his larger opponent sees that his rival is getting bigger, he takes steroids to keep up. As a result, the one who was bigger to begin with is still bigger, but both athletes have had their bodies ravaged by steroids.
One reason steroid use has become so widespread is that it fits in with society's attitude of self-gratification. High school and college athletes tell me, "I will do whatever it takes to get ahead." Even after I've explained all of the dangers of steroid use, most of them say they still plan to use the drugs because that's the only way they can see to achieve their goals.
When I talk about the side effects of steroids with teens, they say, "It's not going to happen to me." I had the same feeling of invincibility when I smoked cigarettes. Doctors call this the "Superman syndrome." I stopped smoking almost 30 years ago because I was coughing very badly. Once I quit and discovered how much better I felt, I became a strong antismoking advocate with my patients. The only way to keep teens clean is to make sure that they understand all of the dangers and that there is no way of avoiding them. Whether it's cigarettes or steroids, they have to understand that they are mortal like everyone else.
Parents need to be educated about steroids as well. One mother, who told me her teenage son was into body building, asked me to prescribe "the proper dose of steroids so he wouldn't get into trouble." I told her that I don't prescribe or deal in steroids and attempted to talk her out of finding steroids for her son.
The search for a "magic bullet" to improve performance has led athletes to try other drugs. Various vitamins and herbal mixtures sold through catalogs advertised in muscle magazines purportedly improve strength. There is absolutely no evidence that any of them work. An illegal drug called gamma hydroxybutyrate is being sold in body-building and athletic clubs and in some health food stores. The Food and Drug Administration has issued a public health warning stating that this potent drug has powerful side effects, including coma, seizures, and severe breathing problems.
A synthetic version of human growth hormone is said to help turn a soft, mushy body into a lean, lanky physique. Growth hormone has side effects similar to those of steroids plus other side effects that have not yet been carefully studied.
A substance being abused by athletes to enhance stamina and performance is recombinant erythropoietin, known as EPO. This genetically engineered drug was created for people who suffer from kidney failure in order to raise their red blood cell levels. Red blood cells are essential for carrying oxygen, so some athletes and trainers started using the drug to improve the body's ability to carry oxygen.
Injecting the drug does enhance an athlete's performance in aerobic endurance events. Many bicycle racers, marathon runners, and cross-country skiers are suspected of using the drug. Yet doctors and blood specialists have linked EPO to deaths among European professional bicyclists. Thus, even though EPO may raise your aerobic capacity, it may also kill you.