Exercise |
The goals of exercise are to improve oxygen delivery and metabolic processes, build strength and endurance, decrease body fat, and improve movement in joints and muscles. All of these benefits are essential to good health, and everyone should try to incorporate an exercise routine into their daily lives. No one is too young or too old to exercise. There are risks, however, to strenuous exercise, which people should discuss with a physician. One-half of all people who begin a vigorous training regime drop out within a year, so the key to attaining and maintaining physical fitness is to find activities that are exciting, challenging, and satisfying. The American Heart Association recommends that healthy individuals engage in 30-minute or longer workouts at least three or four times per week; exercising more than five times a week for 10 to 24 minutes each session is even better. People over 45 who have not had a physical exam in two years or longer, people with serious or chronic medical conditions or who are at risk for heart disease, and people on medication should consult a physician before embarking on a serious exercise program.
Experts divide exercise into three general categories, aerobic, strength, and flexibility, and strongly recommend a balanced program that includes all three. (Speed training is also a major category, but is generally practiced only by competitive athletes.) Gyms and exercise clubs with personal trainers are widely available and can be useful, but they can also be very expensive and are not necessary. Personal trainers without any connection to a well-reputed gym or fitness club should be certified by a major fitness organization, such as the Aerobics and Fitness Association of America (AFAA) or the American Council on Exercise. Exercise videos may also be helpful, but people should be sure they are suited to individual age and health needs and bear the seal of the AFAA.
A few simple rules are helpful as you develop your own routine. Don't eat two hours before vigorous exercise, but drink plenty of fluids before, during, and after a workout. Adjust activity according to the weather and reduce it when fatigued or ill. When exercising, listen to the body's warning symptoms, and consult a physician if exercise induces chest pain, irregular heartbeat, undue fatigue, nausea, unexpected breathlessness, or lightheadedness. Warm-up and Cool-Down Period. Warming up and cooling down are important parts of any exercise routine. They aid the body in making the transition from rest to activity and back again and can help prevent soreness or injury, especially in older people. Warm-up exercises should be practiced for 5 to 10 minutes at the beginning of an exercise session. Older people need a longer period to warm up their muscles. Low-level aerobic exercise is the best approach, such as walking briskly, swinging the arms, or jogging in place. To cool down, one should walk slowly until the heart rate is 10 to 15 beats above resting rate. Stopping too suddenly can sharply reduce blood pressure, a danger for older people, and cause muscle cramping. Stretching is appropriate for the cooling down period, but not for warming up because it can injure cold muscles. Particular exercises may require stretching specific muscles. For example, a jogger or biker might emphasize stretching the hamstrings, calves, groin, and quadriceps, while swimmers would focus on the groin, shoulders, and back.
Aerobic exercises build endurance and keep the heart pumping at a steady but elevated rate for an extended period. Practicing them regularly can enhance cardiac function, boost HDL (the "good") cholesterol levels, strengthen the bones in the spine, and lower the risk of heart attack, high blood pressure, stroke, diabetes, and even some forms of cancer. Aerobic exercise also trims body fat and can improve one's sense of well-being. Jogging, swimming, cycling, stair-climbing, and aerobic dancing are all examples. As little as one hour a week is helpful, but three to four hours per week are optimal. People who are out of shape or elderly should start aerobic training gradually with five to ten minutes of low-impact aerobic activity (e.g., gardening, yard work, or walking) every other day and build toward a goal of 30 minutes per day, three to seven times a week.
Because it is so natural and convenient, brisk walking is an excellent and easy way to accomplish aerobic exercise. Some research indicates that walking at a swift pace burns at least as many calories as running or jogging for the same distance and poses less risk for injury to muscle and bone. A 1999 study further suggested that walking at a brisk pace for three or more hours a week also reduced the risk for coronary heart disease by 65%.
Swimming is an ideal exercise for many people with certain physical limitations, including pregnant women, individuals with musculoskeletal problems, and those who suffer from exercise-induced asthma. Swimming, however, will not raise the heart rate quite as much as other sports because of the so-called "diving reflex," which causes the heart to slow down automatically when the body is immersed in water. For swimming, use a heart rate target of 75% of the maximum and then subtract 12 beats per minute.
Although Americans spend nearly $2 billion on home exercise equipment, all that's really necessary for a workout is a good pair of shoes, well-made, well-fitting, and broken in but not worn down. They should support the ankle and provide cushioning for impact sports such as running or aerobic dancing. Airing out the shoes and feet after exercising reduces chances for skin conditions such as athlete's foot. Comfort and safety are the key words for workout clothing. For out door nighttime exercise, a reflective vest and light-colored clothing must be worn. Bikers, roller bladers, and equestrians should always wear safety devices such as helmets, wrist guards, and knee and elbow pads. Goggles are mandatory for indoor racquet sports. For vigorous athletic activities, such as football, ankle braces may be more effective in preventing ankle injuries than tape.
A lot of money spent on equipment does not always translate into a better workout or better results. A simple jump rope improves aerobic endurance for people who are able to perform high impact exercise. Jumping rope should be done on surfaces that have some give to avoid joint injury. (A good floor mat is important to provide cushioning for all home exercises.) Home exercise machines can be adapted to any fitness level and can be used day or night. For burning calories, the treadmill has been ranked best, followed by stair climbers, the rowing machine, cross country ski machine, and stationary bicycle. Elliptical trainers may be even better than treadmills for elevating heart rate and increasing calorie expenditure and oxygen consumption. Stationary bikes and stair climbers condition leg muscles. Stationary bikes are fairly economical and easy to use safely. The pedals should turn smoothly, the seat height should adjust easily, and the bike's computer should be able to adjust intensity. Stair machines offer very intense, low-impact workouts and may be as effective as running with less chance of injury. Rowing and cross-country ski machines exercise both the upper and lower body.
Cheaper models of exercise machines tend to be flimsy and hard to adjust, but many sturdy, moderately priced machines are available. The higher-end models may utilize computers to record calories burned, speed, and mileage. While their readouts may provide motivation and gauge the intensity of a workout, they are not always accurate. Before investing in and bringing home an exercise machine, it is wise to test it out first at a gym. In addition, initial supervised training when using these machines can reduce the risk of injury that might occur with self-instruction.
A number of sports beverages are sold with the claim that they increase endurance. Studies on two of these drinks (Endurox, Sports) however, reported no benefit from their use.
Where aerobic exercise emphasizes endurance, isometric exercise focuses on strength. Adding 10 to 20 minutes of modest strength training two to three times a week is important for a balanced exercise program. People who only exercise aerobically eventually lose upper body strength. Isometric training builds muscle strength while burning fat, helps maintain bone density, and improves digestion. It appears to lower LDL (the so-called "bad") cholesterol levels. Isometric exercise is beneficial for everyone, even people in their 90s. In fact, strength training assumes even more importance as one ages because after age 30 everyone undergoes a slow process of muscular erosion, which can be reduced or even reversed by adding resistance training to an exercise program. (Please note, people at risk for cardiovascular disease should not perform isometric exercises without checking with a physician.)
Individuals should first select a weight or rubber band tension that allows a maximum of eight repetitions. When 12 repetitions can be completed, a higher weight or tension that limits the individual again to eight repetitions should be used. Once 12 repetitions can be completed at maximum tension, resistance can be lowered and the number of repetitions increased to 15 to 20. While doing these exercises, it is important to breathe slowly and rhythmically. Exhale as the movement begins; inhale when returning to the starting point. The first half of each repetition should last two seconds, and the return to the original position should last four seconds. Joints should be moved rhythmically through their full range of motion during a repetition and not locked up. For maximum benefit, one should allow 48 hours between workouts for full muscle recovery.
Any heavy object that can be held in the hand, such as a plastic bottle filled with sand or water, can serve as a weight. Heavy rubber bands or tubing are excellent devices for resistance training; they are inexpensive, come in various tensions, and are safer and more convenient than free weights for exercising all parts of the body. Latex bands are easier on the hands than tubing. Many inexpensive hand weights are available to help strengthen and tone the upper body. Ankle weights strengthen and tone muscles in the lower body but are not recommended for impact aerobics or jumping. Hand grips strengthen arms and are good for relieving tension. A pull-up bar can be mounted in a doorway for chin-ups and pull-ups.
Flexibility training uses stretching exercises to prevent cramps, stiffness, and injuries. It also ensures a wider range of motion (i.e., the amount of movement a joint and muscle has). Yoga and Tai Chi, which focus on flexibility, balance, and proper breathing, lower stress levels, help to reduce blood pressure, and may even have beneficial effects on cholesterol levels. Authorities now recommend performing stretching exercises for 10 to 12 minutes at least three times a week. When stretching, exhale and extend the muscles to the point of tension, not pain, and hold for 20 to 60 seconds (beginners may need to start with a 5 to 10 second stretch). Remember to breathe constantly while holding the stretch and inhale when returning to a relaxed position.
Certain stretching exercises are particularly beneficial for the back. It is important when doing stretches that involve the back to relax the spine, to keep the lower back flush with the mat, and to work only the muscles required for changing position, usually the abdomen. It is also important to breathe evenly while stretching. Holding one's breath defeats the purpose; it causes muscle contraction and raises blood pressure.
Longevity and Aging Exercise can add healthy and active years to one's life. Moderately fit people, even if they smoke or have high blood pressure, have a lower mortality rate than the least fit. Studies continue to show that it is never too late to start exercising and that even small improvements in physical fitness and activity at any age can significantly lower the risk of death. Simply walking regularly can prolong life and independent living in the elderly. Even in nursing home patients, programs aimed at improving strength, balance, gait, and flexibility have significant benefits. Resistance training is particularly important for the elderly because it is the only form of exercise that can slow and even reverse the decline in muscle mass, bone density, and strength. As little as one day a week of resistance training improves overall strength and agility. Adding workouts that involve fast movements may be even more protective for older people. Flexibility exercises promote healthy muscle growth and help reduce the stiffness and loss of balance that accompanies aging, easing these activities.
Inactivity is one of the four major risk factors for heart disease, on par with smoking, unhealthy cholesterol, and even high blood pressure. Like all muscles, the heart becomes stronger and larger as a result of exercise so it can pump more blood through the body with every beat. Exercise does not increase the maximum heart rate, but a fit heart can pump more blood at this maximum level and can sustain it longer with less strain. The resting heart rate of those who exercise is also slower because less effort is needed to pump blood. For preventing heart disease, frequency of exercises may be more important than duration. Exercise helps improve heart health in people with many forms of heart disease and can even reverse some risk factors, such as the effects of smoking. Unfortunately, studies show that those with the highest heart risks (such as smokers and people who are overweight), and who would most benefit from exercise, are the least likely to persist.
People who maintain an active lifestyle have a 45% lower risk of developing coronary heart disease than do sedentary people. Studies report that people who change their diet in order to control cholesterol and lower the risk for coronary artery disease are successful only when they also follow a regular aerobic exercise program. Brisk walking, jogging, swimming, biking, aerobic dance, and racquet sports, are the best forms of exercise for reducing triglyceride levels (harmful fat molecules) and raising HDL (the so-called good cholesterol) levels. It may take up to a year of sustained exercise for HDL levels to show significant improvement. Aerobic exercise also appears to open up the blood vessels and, in combination with a healthy diet, may improve blood clotting factors. Burning at least 250 calories a day (the equivalent of about 45 minutes of brisk walking or 25 minutes of jogging) seems to confer the greatest protection against coronary artery disease. Even moderate exercise, however, reduces the risk of heart attack, but in terms of raising HDL levels, more is better. Resistance (weight) training offers a complementary benefit by reducing LDL (the so-called bad cholesterol) levels. Triglycerides, which rise after a high-fat meal, can be lowered either with a single, prolonged (about 90 minutes) aerobic session or by several shorter sessions during the day. Before engaging in any strenuous exercise, it is advisable to consult a physician.
Studies indicate that regular exercise helps keep arteries elastic, even in older people, which in turn ensures blood flow and normal blood pressure. Sedentary people have a 35% greater risk of developing hypertension than athletes do. No person with high blood pressure should start an exercise program without consulting a physician. Studies have shown that high-intensity exercise may not lower blood pressure as effectively as moderate intensity exercise. In one study, for example, moderate exercise (jogging two miles a day) controlled hypertension so well that more than half the patients who had been taking drugs for high blood pressure were able to discontinue their medication. Studies have indicated that Tai Chi, an ancient Chinese exercise involving slow, relaxing movements, may lower blood pressure almost as well as moderate-intensity aerobic exercises. Before exercising, people with hypertension should avoid caffeinated beverages, which increase heart rate, the workload of the heart, and blood pressure during physical activity.
The benefits of exercise on stroke are uncertain. According to one analysis of a group of 11,000 men, those who burned between 2,000 and 3000 calories a week (about an hour of brisk walking five days a week) cut their risk of stroke in half. Groups who burned between 1,000 and 2,000 calories or more than 3,000 calories per week also gained some protection against stroke but to a lesser degree. In the same study, exercise that involved recreation was more protective than exercise routines consisting simply of walking or climbing.
Traditionally, heart failure patients have been discouraged from exercising. Now, exercise performed under medical supervision is proving to be helpful for select patients with stable heart failure. In one study, patients between the ages of 61 and 91 increased their oxygen consumption by 20% after six months by engaging in supervised treadmill and stationary bicycle exercises. Performing daily hand grip exercises may improve blood flow through the arteries of patients with heart failure. Experts warn, however, that exercise is not appropriate for all heart failure patients.
Diabetes Diabetes, particularly type 2, is reaching epidemic proportions throughout the world as more and more cultures adopt Western dietary habits. Aerobic exercise is proving to have significant and particular benefits for people with both type 1 and type 2 diabetes; it increases sensitivity to insulin, lowers blood pressure, improves cholesterol levels, and decreases body fat. Regular exercise, even of moderate intensity, improves insulin sensitivity. In fact, studies of older people who engage in regular, moderate, aerobic exercise (e.g., brisk walking, biking) lower their risk for diabetes even if they don't lose weight. Anyone on insulin or who has complications from diabetes must take special precautions before embarking on a workout program.
Exercise helps to reduce pain and stiffness and increases flexibility, muscle strength, endurance, and well being. Exercising also helps people reduce their weight and maintain weight loss. Osteoarthritis patients should avoid high-impact sports such as jogging, tennis, and racquetball. The three types of exercise that are best for people with arthritis are range of motion, strengthening (or resistance), and aerobic exercises. Strengthening exercises include isometric exercises (pushing or pulling against static resistance) and stretching exercises to build strength and flexibility without unduly stressing the joints. These exercises may be particularly important if leg muscle weakness turns out to be a cause of osteoarthritis, as some research suggests. Low-impact aerobics also help stabilize and support the joints and may even reduce inflammation in some joints. Cycling and walking are beneficial, and swimming or exercising in water is highly recommended for people with arthritis. One study compared a group of patients who embarked on an aerobic and resistance exercise program with a group that received patient education; the exercising group developed less disability and pain and showed a better ability to perform physical tasks. Patients should strive for short but frequent exercise sessions guided by physical therapists or certified instructors.
Exercise is very important for slowing the progression of osteoporosis. Women should begin exercising before adolescence since bone mass increases during puberty and reaches its peak between ages 20 and 30. Weight bearing exercise, which applies tension to muscle and bone, encourages the body to compensate for the added stress by increasing bone density by as much as 2% to 8% a year. High-impact weight-bearing exercises, such as step aerobics, are very protective for premenopausal women. These exercises, however, increase the risk for osteoporotic fractures in elderly patients, who would benefit most from regular, brisk, long walks. Even moderate exercise (as little as an hour a week) helps reduce the risk for fracture, but everyone who is in good health should aim for more. Careful weight training is beneficial as well for older women. Low-impact exercises that improve balance and strength, particularly yoga and Tai Chi, have been found to decrease the risk of falling; in one study, Tai Chi reduced the risk by almost half.
One of the most common complaints of modern men and women, lower-back pain, afflicts up to 80% of all Americans. Sedentary living, obesity, poor posture, badly designed furniture, and stress all contribute to back pain. An appropriate exercise program focusing on flexibility and strengthening the muscles in the abdomen may help prevent back problems. Yoga stretching is beneficial and can be incorporated into the warm-up and cool-down periods. The best exercises for athletes with bad backs include swimming, walking, and cross-country skiing. High-impact sports, including aerobic dance and downhill skiing, should be avoided. Exercises that strengthen the abdominal muscles such as partial sit-ups, which maintain the back's normal curve and help support the body's weight, can alleviate stress on the lower back. However, the classic full sit-up (raising your head and shoulders off the floor up to your knees) may aggravate back pain and should be avoided by anyone at risk for lower back problems.
Although exercise does not improve lung function, training helps some patients with chronic lung disease by strengthening their limb muscles, thus improving endurance and reducing breathlessness.
A number of studies have indicated that regular, even moderate, exercise reduces the risk of colon cancer and, in fact, any cancer related to obesity. Moderate exercise may also help reduce the risk for breast cancer and strenuous activity may lower the risk of prostate cancer. A recent study of 100,000 nurses, however, suggested that the benefits of exercise on breast health may be greater or lesser at different times in a woman's life, depending on her menstrual status and estrogen levels. For example, the study found no added protection from exercise in young adulthood (when the disease is uncommon in any case). Several studies are underway to measure the effect of exercise on patients who have been diagnosed with cancer. Even though preliminary, they already suggest that exercise has a positive physical, mental, and emotional effect. Exercise can improve physical strength, functional capacity, and the ability to battle the negative side effects of chemotherapy, including nausea and fatigue. More studies are warranted.
The effect of exercise on the immune system varies on intensity and regularity. Although offering no evidence of improved immunity from exercise, one study reported that people who exercised as little as once a week in employee fitness programs averaged nearly five fewer sick days annually than those who did not participate in such programs. Other studies have also indicated that regular vigorous exercise improves immune function. In people who already have colds, exercise has no effect on the illness' severity or duration of the infection. People should avoid strenuous physical activity when they have high fevers or widespread viral illnesses, however. High-intensity or endurance exercises appear to suppress the immune system while they are being performed. Some highly trained athletes, for instance, report being susceptible to colds after strenuous events; very low fat diets appear to support this negative effect on the immune system. A higher fat-diet may help redress this imbalance (omega-3 fatty acids, found in fish and canola oil are preferred). Whether carbohydrate loading provides much additional value is not clear.
People with multiple sclerosis, Parkinson's disease, and Alzheimer's disease should be encouraged to exercise. Specialized exercise programs that improve mobility are particularly valuable for Parkinson's patients. Patients with neurological disorders who exercise experience less spasticity as well as reduction in, and even reversal of, muscle atrophy. In addition, the psychological benefits of exercise are extremely important in managing these disorders. Exercise machines, aquatic exercises, and walking are particularly useful.
Healthy women with normal pregnancies should exercise at least three times a week, being careful to warm up, cool down, and drink plenty of liquids. Many prenatal calisthenics programs are available. Experts advise, in general, that when exercising, the expectant mother's pulse rate should not exceed 70% to 75% of the maximum heart rate or more than 150 beats per minute. (In one study, previously sedentary low-risk pregnant women exercised to 150 to 156 beats per minute three times a week without any harmful effects, but any woman who did not exercise intensely before becoming pregnant should check with their physician before embarking on such a program.) In any case, fit women who have exercised regularly before pregnancy may work out intensely as long as no discomfort occurs. According to one study, vigorous exercise may improve the chances for a timely delivery. All pregnant women should avoid high-impact, jerky, and jarring exercises, such as aerobic dancing, which can weaken the pelvic floor muscles that support the uterus. During exercise, women should monitor their temperature to avoid overheating, a side effect that can damage the fetus. (No pregnant women should use hot tubs or steam baths, which can cause fetal damage and miscarriage.) Swimming and water aerobics may be the best option for most pregnant women and have special benefits for those with fluid build-up. Water exercises involve no impact, overheating is unlikely, and swimming face down promotes optimum blood flow to the uterus. Performing yoga exercises under the guidance of informed instructors can be very helpful. Walking is also highly beneficial. To strengthen pelvic muscles, women should perform Kegel exercises at least 6 times a day, which involve contracting the muscles around the vagina and urethra for 3 seconds 12 to 15 times in a row.
Endurance athletes often report gastrointestinal distress, such as bloating, diarrhea, and gas, even at rest. Experts suggest, however, that moderate regular exercise, might reduce the risk for some intestinal disorders, including ulcers, irritable bowel syndrome, indigestion, and diverticulosis. Older people who exercise moderately may have a lower risk for severe gastrointestinal bleeding.
Exercise can improve pain from clogged arteries in the legs, a condition called intermittent claudication. The best approach in such cases is to walk until pain develops; then rest until pain resolves before resuming walking. In six-month studies, people had tripled the amount of time they could walk before the onset of pain.
In one large study of risk factors for heart disease, low fitness in obese men was the greatest predictor for lower survival, beating even diabetes. Exercise burns calories and can help individuals fight obesity. Be forewarned, however, that the pounds won't melt off magically. It takes 35 miles of walking or jogging to burn the calories in one pound of fat. In addition, without dieting, weight loss may be minimal with exercise alone because dense muscle mass replaces fat as the body gets more fit. (Nonetheless, a fit body will look more toned and be healthier.) Regular aerobic exercise is a good way to shed pounds (walking and cycling being more effective than swimming). A number of studies have now suggested that exercising daily for several short vigorous sessions (as little as 10 minutes each), particularly with the use of home exercise equipment, may be the most effective method for adhering to an exercise program and losing weight. Abdominal fat is a particular danger to the heart, and abdominal crunches may help replace this fat with muscle. To perform these exercises, the individual lies on the back with the head and shoulders raised; he or she contracts the stomach muscles, curling the torso slightly forward. It is not yet known whether doing such crunches will specifically protect against heart disease, however. Contrary to popular belief, exercise does not increase appetite in people who want to lose weight.
The psychological and emotional benefits from exercise are numerous, and many experts now believe that exercise is a viable and important component in the treatment of emotion disorders. A 1999 review of multiple studies found, across the board, that exercise advances the treatment of clinical depression and anxiety, enhances moods, and improves self-esteem. According to one study, exercise was as effective for improving mood in people with clinical depression as some common forms of psychotherapy. Another study found that teenagers who are active in sports have a much better sense of well being than their sedentary peers; the more vigorously they exercise, the better their emotional health. Yet another study found that regular brisk walking cut the incidence of sleep disturbances in half in people who suffer from them (it should be noted, however, that exercise in the evening can cause sleep disturbances). Both aerobic and nonaerobic workouts are shown to have these positive effects on depression, though rhythmic aerobic and yoga exercises may be particularly helpful for combating stress, anxiety, and sleeplessness. Either brief periods of intense training or prolonged aerobic workouts raise levels of chemicals in the brain, such as endorphins, adrenaline, serotonin, and dopamine, that produce feelings of pleasure, causing the so-called "runner's high." (Contrary to some public reports, the risk of becoming addicted to intense exercise to the point of self-harm is extremely rare.) Aerobic exercise is also linked with improved mental vigor, including reaction time, acuity, and math skills. Exercising may even enhance creativity and imagination. According to one study, older people who are physically fit respond to mental challenges just as quickly as unfit young adults. (Stretching and weight training appear to have no such effects.)
General Guidelines for High-Risk Patients Anyone with coronary artery disease or with several risk factors for developing it should seek medical advice before beginning a workout program. Patients with heart disease, however, can exercise safely as long as they work out under medical supervision and carefully monitor warning symptoms. Strenuous physical exertion is never recommended for people who suffer from uncontrolled diabetes, uncontrolled seizures, heart failure, unstable angina, significant aortic valve disease, or aortic aneurysm. Even some of these conditions, however, such as heart failure, might benefit from mild or moderate exercise under controlled situations.
Often, it is difficult for a physician to predict health problems that might arise as the result of an exercise program. Some physicians use a questionnaire for people over 40 who want to intensify their exercise programs. Those who answer "yes" to the following questions should have a complete medical examination before developing an exercise program: (1) Has a doctor recommended medically supervised activity because of a heart condition? (2) Is chest pain brought on by physical activity? (3) Has chest pain occurred during the previous month? (4) Does the person faint or fall over from dizziness? (5) Is bone or joint pain intensified by exercise? (6) Has medication been prescribed for hypertension or heart problems? or (7) Is the person aware of or has a doctor suggested any physical reason for not exercising without medical supervision?
Some physicians may perform an exercise electrocardiography test, commonly called a stress test, before recommending exercise, particularly for people with heart disease or risk factors for it. Uncommonly, some people may be able to exercise for long periods and still be at risk for a heart attack. A new imaging technique called treadmill myocardial perfusion imaging (MPI), which uses a radioisotope may be able to identify these people. During the test, the patient walks on a treadmill, which gradually moves faster and faster, while the physician monitors his or her heart's activity. It can also establish an individual's maximum heart rate so the physician can tailor an "exercise prescription" to a patient's work capacity.
An estimated 1.5 million heart attacks occur every year; of these, 75,000, or about 5%, occur after heavy exertion, leading to 25,000 deaths. Isometric workouts, such as snow shoveling, tend to stress the heart and raise blood pressure for a brief period. They can also cause spasms in the arteries leading to the heart. Some studies suggest that competitive sports, which couple intense activity with aggressive emotions, are more likely to trigger a heart attack than other forms of exercise. One major study found that sedentary people who throw themselves into a grueling workout increase their risk of heart attack 107 times beyond that which would occur with low or no exertion. This fact should be kept in perspective, however. For the average non-smoking, non-diabetic, 50-year old man, the risk for a heart attack during strenuous exercise is only one in one million. In addition, the risk radically decreases for those who get in shape gradually and stay fit through regular activity. In general, deadly effects from intense exercise occur in people with existing heart disease, in whom dangerously abnormal heart rhythms can occur or the walls of a cholesterol-laden artery can tear, resulting in a blood clot. Even when a seemingly healthy young athlete dies during exercise, an autopsy usually reveals underlying heart disease. At least 40% of young men who die suddenly during a workout have previously experienced, and ignored, warning signs of heart disease, including fainting and chest pains. Sometimes medical screening can detect these silent disorders, but because the abnormalities are so rare, it's impractical to test healthy young adults with expensive echocardiograms. The best preventive tactic is simply to listen to the body and seek medical help at the first sign of symptoms, including irregular heartbeat, undue shortness of breath, chest pain, or weakness.
Because glucose levels swing dramatically during exercise, people with diabetes should monitor their levels carefully before, during, and after workouts. To avoid hypoglycemia (dangerously low blood sugar), diabetics should inject insulin in sites away from the muscles they use the most during exercise. Before working out, people with diabetes should also avoid drugs that increase the risk of hypoglycemia, including beta-blockers and alcohol. Finally, insulin-dependent athletes may need to decrease insulin doses or take in more carbohydrates, especially in the form of pre-exercise snacks (milk is particularly helpful). Because diabetics may have silent heart disease, they should always check with their physicians before undertaking vigorous exercise. Exercise can also pose a threat to those diabetics suffering from proliferative retinopathy (fragile blood vessels that can leak fluid to the back of the eye). Strenuous exercise is not recommended for uncontrolled diabetes.
People with exercise-induced asthma (EIA) should not be reluctant to work out. EIA occurs most often during intense exercise in cold, dry air; exercising in a humid environment, such as an indoor pool, can help. Fortunately, treatment options are excellent and allow people with EIA to exercise vigorously, even at the level of Olympic competition. Studies have shown that individuals with asthma can exercise at an intensity similar to those without asthma, although the cardiorespiratory fitness of a person with asthma may be a bit lower. People with asthma should consult a physician for assessment of the severity of the disorder and for instructions on how to initiate an exercise program. On days when air pollution counts are high, people with asthma should take precautions and avoid exercise.
President's Council on Physical Fitness and Sports, HHH Building, Rm. 738H, 200 Independence Ave. S.W., Washington, DC 20201. Call (202-690-9000) or on the Internet (http://www.whitehouse.gov/WH/PCPFS/html/fitnet.html) They publish an excellent newsletter, Physical Activity and Fitness Research Digest .
Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Division of Nutrition and Physical Activity, MS K-46, 4770 Buford Highway, NE, Atlanta, Georgia 30341-3724. Call (888-CDC-4NRG) or (888-232-4674) or on the Internet (http://www.cdc.gov) or for special information on exercise (www.cdc.gov/nccdphp/dnpa/readyset)
Aerobics and Fitness Association of America, 15250 Ventura Blvd., Suite 200, Sherman Oaks, CA 91403. Call (800-BE-FIT86) or (800 YOUR BODY) or on the Internet (www.afaa.com)
American Council on Exercise, 5820 Oberlin Drive, Suite 102, San Diego, CA 92121-3787. Call (800-529-8227) or on the Internet (http://www.acefitness.org/). Organization provides information on exercise and gives names of personal trainers in local areas.
Shape Up America!, 6707 Democracy Blvd, Suite 107, Bethesda, Maryland 20817. On the Internet (http://www.shapeup.org/). Excellent site founded by Everett Koop, MD former Surgeon General to educate the public on fitness and health. offers a calculation of a person's BMI and results gives risk group. Many fact sheets and good links are available.
Offers a number of calculators for weight and exercise (http://www.phys.com/b_nutrition/00home/home.htm)