EXERCISE

March 2002

WHAT ARE THE GOALS OF EXERCISE?

General Guidelines

The goals of exercise are the following:

Improve oxygen delivery and metabolic processes.
Build strength and endurance.
Decrease body fat.
Improve movement in joints and muscles.
Improve sense of well being.

Most evidence on the benefits of exercise focus on heart protection. A 2001 study, however, indicated that overall fitness reduced mortality rates in men from non-cardiac causes nearly as well as it did from heart-related deaths. (The more fit the individual, the lower the risk.) No one is too young or too old to exercise. The US Surgeon General recommends at least 30 minutes of moderate exercise, such as brisk walking, nearly every day.

There are risks, however, to strenuous exercise, which people should discuss with a physician. The American Heart Association recommends that 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.

Fifty percent 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.

WHAT EXERCISE METHODS ARE RECOMMENDED?

The sweat experts divide exercise into three general categories:

Aerobic (also called endurance).
Strength (also called resistance).
Flexibility.

A balanced program should include all three. (Speed training is also a major category, but is generally practiced only by competitive athletes.)

Rules for Any Exercise Method

A few simple rules are helpful as you develop your own routine.

Don't eat two hours before vigorous exercise.
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 light-headedness.

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 five 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, is a danger for older people, and may 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 (Endurance) Training

Benefits of Aerobic Exercise. Regular aerobic exercise provides the following benefits:

Builds endurance.
Keeps the heart pumping at a steady and elevated rate for an extended period, boosts HDL (the "good") cholesterol levels, and helps control blood pressure.
Strengthens the bones in the spine.
Helps maintain normal weight.
Improve one's sense of well being.

Types of Aerobic Exercise. Aerobic exercise is usually categorized as high or low impact. Examples of each include the following:

Low to moderate impact exercises: walking, swimming, stair climbing, step classes, rowing, and cross-country skiing. Nearly anyone in reasonable health can engage in some low to moderate impact exercise. Brisk walking burns as many calories as jogging for the same distance and poses less risk for injury to muscle and bone.
High impact exercises: running, dance exercise, tennis, racquetball, squash. High-impact exercises should be performed no more than every other day and less for those who are overweight, elderly, out of condition, or have an injury or other medical problem that would preclude high-impact.

Aerobic Regimens. As little as one hour a week of aerobic exercises is helpful, but three to four hours per week are optimal. Some research indicates that simply walking briskly for three or more hours a week reduces the risk for coronary heart disease by 65%. In general, the following guidelines are useful for most individuals:

For most healthy young adults, the best approach is a mix of low and higher impact exercise. Two weekly workouts will maintain fitness, but three to five sessions a week is better.
People who are out of shape or elderly should start aerobic training gradually with five to 10 minutes of low-impact aerobic activity every other day and build toward a goal of 30 minutes per day, three to seven times a week. (For heart protection, frequency of exercises may be more important than duration.)
Swimming is an ideal exercise for many elderly and certain people with physical limitations, including pregnant women, individuals with musculoskeletal problems, and those who suffer from exercise-induced asthma.
People who seek to lose weight should aim for six to seven low impact workouts a week.

One way of gauging the optimal intensity of exercise is to aim for a "talking pace," which is enough to work up a sweat and still be able to converse with a friend without gasping for breath. As fitness increases, the "talking pace" will become faster and faster.

Shoes and Clothing. All that's really necessary for a workout is a good pair of shoes that are well made and fit well, 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 outdoor 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.

Aerobic-Exercise Equipment. Home aerobic exercise machines can be adapted to any fitness level and can be used day or night. Before investing in and bringing home any exercise machine, however, 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.

Very inexpensive exercise machines tend to be flimsy and hard to adjust, but many sturdy machines are available at moderate prices. 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, however, they are not always accurate.

The following are a few observations on specific equipment:

A good floor mat is important to provide cushioning for all home exercises.
A simple jump rope improves aerobic endurance for people who are able to perform high impact exercise. Jumping rope should be done on a floor mat plus a surface that has some give to avoid joint injury.
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, however, may be even better than treadmills for elevating heart rate and increasing calorie expenditure and oxygen consumption.)
Stationary bikes condition leg muscles and 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 also condition leg muscles. They 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.

Shoes for Sports
Aerobic dancing	Sufficient cushioning to absorb shock and pressure that is many times greater than ordinary walking. Arches that maintain side-to-side stability. Thick upper leather support. Toe-box. Orthotics may be required for people with ankles that over-turn inward or outward. Soles should allow for twisting and turning.
Cycling	Rigid support across the arch to prevent collapse during pedaling. Heel lift. Cross-training or combo hiking/cycling shoes may be sufficient for casual bikers. Toe clips or specially designed shoe cleats for serious cyclers. In some cases, orthotics may be needed to control arch and heel and balance forefoot.
Running	Sufficient cushioning to absorb shock and pressure. Fully bendable at the ball of the foot. Sufficient traction on sole to prevent slipping. Consider insole or orthotic with arch support for problem feet.
Tennis	Allows side-to-side sliding. Low-traction sole. Snug fitting heel with cushioning. Padded toe box with adequate depth. Soft-support arch.
Walking	Lightweight. Breathable upper material (leather or mesh). Wide enough to accommodate ball of the foot. Firm padded heel counter that does not bite into heel or touch ankle bone. Low heel close to ground for stability. Good arch support. Front provides support and flexibility.

Heart Rate Goal. It helps to aim for a heart rate of roughly 70% to 85% of its maximum rate during actual exercise. Exercise does not increase the maximum heart rate. It strengthens the heart so that it can pump more blood at this maximum level and can sustain this level longer with less strain. (Note: abundant data show that attaining target heart rate is not the key to the health benefits of physical activity--exercising at a steady pace is the first goal.)

To determine ones own maximum heart rate per minute simply subtract one's age from 220.

To determine heart rate, do the following:

Measure the pulse by pressing the first two fingers of one hand gently on either the artery on the inside of the wrist or on a carotid artery (located under the jaw either on the right or left side of the front of the neck).
Count pulse beats for 10 seconds.
Multiply the result by six. This gives the per-minute total. [ See Table Target Heart Rates for a 10-sec. Pulse Count.]

Some exceptions may apply:

A study on older adults suggests that they should aim for 60% to 73% of peak heart rate.
Swimmers should use a heart rate target of 75% of the maximum and then subtract 12 beats per minute. The reason for this is that swimming 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.

TARGET HEART RATES FOR A 10-SEC. PULSE COUNT
Age	Low	High
	(70% max.)	(85% max.)
20	23	28
30	22	27
40	21	26
50	20	24
60	18	23

VO2 Max. Serious exercisers may use a VO2 max calculation, which measures the amount of oxygen inhaled and exhaled while exercising at the highest possible level. The most accurate testing method employs computers, but anyone can estimate V02 without instrumentation (with an accuracy of about 95%):

After running at top pace for 15 minutes, round off the distance run to the nearest 25 meters.
Divide that number by 15.
Subtract 133.
Multiply the total by 0.172, then add 33.3.

Olympic and professional athletes train for VO2 max levels above 80. But for the average person interested in fitness, a VO2 max equaling between 50 and 80 is considered an excellent score for overall fitness.

Strength or Resistance Training

Benefits of Strength Exercise. While aerobic exercise increases endurance and helps the heart, it does not build upper body strength or tone muscles. Strength-training exercises provide the following benefits:

Builds muscle strength while burning fat.
Helps maintain bone density.
Improves digestion.
It appears to lower LDL (the so-called "bad") cholesterol levels.

Strength exercise is beneficial for everyone, even people in their 90s. It is the only form of exercise that can slow and even reverse the decline in muscle mass, bone density, and strength that occurs with aging. (Please note: people at risk for cardiovascular disease should not perform strength exercises without checking with a physician.)

Types of Muscle Contractions. There are three types of muscle contractions involved in strength training:

Isometric contractions. There is no change in the length of the muscle. For example, pushing against a wall.
Concentric contractions. These movements shorten muscles (for example, the "up" phase of when the bicep curls up while lifting weights).
Eccentric contractions. These movements lengthen muscles (the "down" phase as the weights are lowered).

Strength-Training Regimens. Strength training involves intense and short-duration activities. For beginners, adding 10 to 20 minutes of modest strength training two to three times a week may be appropriate. The following are some guidelines for starting a strength regimen:

The sequence of a strength training session should begin with training large muscles and multiple joints at higher intensity and end with small muscle and single joint exercises at lower intensities.
Both concentric (shortening) and eccentric (lengthening) muscle actions should be performed. Emphasizing eccentric contractions (the movements that lengthen muscles) is of increasing interest. This approach involves slowing and increasing the duration of these "down" movements. It appears to significantly increase blood flow, and some evidence suggests it may achieve stronger muscles more quickly and improve cardiovascular function compared to a standard movements. It may be particularly beneficial for older people and some people with chronic health problems. Eccentric training increases the risk for muscle soreness and injury, however, and this approach is still controversial.
Strength training involves repetitions, i.e., moving specific muscles in the same pattern against a resisting force (such as a weight) for a preset number of times. In the beginning, most people can start with one set of eight to 12 repetitions per muscle group with low weights.
Students should first choose a weight that is about half of what would require a maximum effort in one repetition. (In other words, if it would take maximum effort to do a single repetition with a 10-pound dumbbell, than the person would start with a five-pound dumbbell.) As individuals are able to perform one or two repetitions over their routine, weights can be increased by 2% to 10%.
Breathe slowly and rhythmically. Exhale as the movement begins; inhale when returning to the starting point.
The first half of each repetition typically lasts two to three seconds. The return to the original position lasts four seconds.
An alternative technique called "super slow" training stretches out one repetition to a 14-second count. This method places far more stress on the muscle group, so fewer repetitions are needed. A full week of recovery is required before repeating this workout. The goal is to initiate changes in the muscles so that the body continues to burn calories after the exercise. Some people report dramatic results from this approach, but scientific verification of these anecdotes is not available. It is very tedious, in any case, and people have a hard time sticking with it. People with high blood pressure should not use this approach.
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.

Strength-Training Equipment. Unlike aerobic exercise, strength training almost always requires some equipment. Strength-training equipment does not, however, have to cost anything. 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. Many wearable weights are available to help strengthen and tone the upper body. Dumbbells (ranging in weight from one to 10 pounds) and resistance bands, for example, are inexpensive, portable, and effective. Ankle weights strengthen and tone muscles in the lower body. (Such wearable weights should not be worn during high-impact aerobics or jumping.) Handgrips strengthen arms and are good for relieving tension. A pull-up bar can be mounted in a doorway for chin-ups and pull-ups. More elaborate and expensive home equipment for working body muscles is also available, costing from $100 to over $1,000. No one should purchase or use strength-training equipment without instruction from a professional.

Flexibility Training (Stretching)

Benefits of Flexibility Training. Flexibility training uses stretching exercises for the following benefits:

Preventing cramps, stiffness, and injuries.
Allowing a wider range of motion (i.e., the amount of movement a joint and muscle has).
Certain flexibility practices, such as Yoga and Tai Chi, also involve meditation and breathing techniques that reduce stress. Such practices appear to have many health and mental benefits and may be very suitable and highly beneficial for many older people and patients with certain chronic diseases.
Certain stretching exercises are particularly beneficial for the back.

Flexibility Training Regiments. Authorities now recommend performing stretching exercises for 10 to 12 minutes at least three times a week. The following are some general guidelines:

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).
Breath evenly and constantly while holding the stretch.
Inhale when returning to a relaxed position. (Holding one's breath defeats the purpose; it causes muscle contraction and raises blood pressure.)
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, often only the abdomen.

Specific Tips for Older People and Exercise

Studies continue to show that it is never too late to start exercising. At any age, even small improvements in physical fitness and activity (such as walking regularly) can prolong life and independent living. Still, about half of Americans over 60 describe themselves as sedentary.

The following tips for exercising may be helpful:

Any older person should have both complete physical and medical examination and professional instruction before starting an exercise program.
In starting out, remember the adage "Start low and go slow." For sedentary, older people one or more of the following programs may be helpful and safe: low impact aerobics, gait training, balance exercises, tai chi, self-paced walking, and lower extremity resistance training using elastic tubing or ankle weights. (Even in the nursing home, programs aimed at improving strength, balance, gait, and flexibility have significant benefits.)
Strength training assumes even more importance as one ages, because after age 30 everyone undergoes a slow process of muscular erosion. The effect can be reduced or even reversed by adding resistance training to an exercise program. One 2000 study found that men between the ages of 60 and 75 have the same potential to gain strength as men in their 20s. As little as one day a week of resistance training improves overall strength and agility. Strength training also improves heart and blood vessel health and general well being.
Power training, which aims for the fastest rate at which a muscle or muscle group can perform work, may be particularly helpful for older women in strengthening muscles and preventing falls.
Flexibility exercises promote healthy muscle growth and help reduce the stiffness and loss of balance that accompanies aging, easing these activities.

WHAT ARE THE EFFECTS OF EXERCISE ON THE HEART AND CIRCULATION?

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 and sustain its maximum level with less strain. The resting heart rate of those who exercise is also slower because less effort is needed to pump blood.

Inactivity is one of the four major risk factors for coronary artery disease, on par with smoking, unhealthy cholesterol, and high blood pressure. However, exercise helps improve heart health in people with many forms of heart disease and can even reverse some risk factors, such as some of the effects of smoking.

People who exercise the most often and vigorously have the lowest risk for heart disease, but any exercise is beneficial. Studies consistently find that light to moderate exercise is even beneficial in people with existing heart disease. However, anyone with coronary artery disease should seek medical advice before beginning a workout program.

General Guidelines for People at Risk for Heart Disease

In one study of older men with heart disease, even four hours of recreational activity on the weekend (e.g., golf, light gardening, and walking) reduced mortality rates compared to men who remained sedentary. Anyone with heart disease or risk factors for developing it, however, should seek medical advice before beginning a workout program. Patients with heart disease can nearly always exercise safely as long as they work out under medical supervision.

Still, it is often difficult for a physician to predict health problems that might arise as the result of an exercise program. At-risk individuals should be very aware of any symptoms warning of harmful complications while they exercise. [See Warning Box, Heart Attack and Sudden Death from Strenuous Exercise.]

Some experts believe that anyone over 40 years old, whether or not they are at risk for heart disease, should have a complete physical examination before starting or intensifying an exercise program. Some physicians use a questionnaire for people over 40 to help determine whether they require such an examination:

Has any doctor previously recommended medically supervised activity because of a heart condition?
Is chest pain brought on by physical activity?
Has chest pain occurred during the previous month?
Does the person faint or fall over from dizziness?
Is bone or joint pain intensified by exercise?
Has medication been prescribed for hypertension or heart problems?
Is the person aware of or has a doctor suggested any physical reason for not exercising without medical supervision?

Those who answer "yes" to any of the following questions should have a complete medical examination before developing an exercise program.

Stress Test. A stress test helps determine the risk for a heart event from exercise. Anyone with a heart problem or history of heart disease should have a stress test before embarking on an exercise program. Experts currently also recommend this test before a vigorous exercise program for older persons who are sedentary, even in the absence of known or suspected cardiovascular disease. It is expensive, however, and some experts believe that it may not be necessary for many older people with no evident health problems or risk factors. They recommend instead a carefully monitored program, starting out with low-intensity exercises and gradually building up.

Heart Attack and Sudden Death from Strenuous Exercise

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.

High-Risk Individuals. In general, the following people should avoid intense exercise or embark on it only with carefully monitoring:

Strenuous physical exertion is never recommended for people who suffer from uncontrolled diabetes, uncontrolled seizures, uncontrolled high blood pressure, a heart attack within six months, heart failure, unstable angina, significant aortic valve disease, or aortic aneurysm.
Older people should be cautious. Studies report that older people who first embark on vigorous exercise are at slightly higher than average risk for a heart attack during the first year, but over time, regular exercise is likely to reduce this risk.
Sedentary people should be cautious. 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.
Young people with genetic or inborn heart disorders should avoid intensive competitive sports.
People who use anabolic steroids to stimulate production of muscle tissue higher risk for stroke and heart attack.

The risk for heart attack from exercise should be kept in perspective, however. Some form of exercise carefully tailored to their specific conditions has benefits for most of these individuals. And in many cases, particularly when the only risk factors are being sedentary and older, exercise can often be increased over time until it is intense.

Hazardous Activities for High-Risk Individuals. The following activities may pose particular dangers for high-risk individuals:

Intense workouts (snow shoveling, slow jogging, speed walking, tennis, heavy lifting, heavy gardening) may be particularly hazardous for people with risk factors for heart disease, particularly older people. They tend to stress the heart, raise blood pressure for a brief period, and may 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.

Listening for Warning Signs. It should be noted that according to one study, at least 40% of young men who die suddenly during a workout have previously experienced, and ignored, warning signs of heart disease. In addition to avoiding risky activities, the best preventive tactic is simply to listen to the body and seek medical help at the first sign of symptoms during or following exercise. They include the following:

Irregular heartbeat.
Undue shortness of breath.
Chest pain.
Weakness.

Heart-Protective Benefits of Exercise

Studies continue to show that physical activity and avoiding high-fat foods are the two most successful means of reaching and maintaining heart healthy levels of fitness and weight.

Effect of Exercise on Coronary Artery Disease and Cholesterol Levels. The following are some observations on the effects of exercise on coronary artery disease and cholesterol:

People who maintain an active lifestyle have a 45% lower risk of developing heart disease than do sedentary people. Even moderate exercise reduces the risk of heart attack. One 2001 study of women found that just one hour of walking a week was associated with a lower risk for heart disease. The effects were similar even in women at high risk for developing heart disease.
People who are on a cholesterol-lowering diet are successful in actually lowering their risk for heart disease only if they also follow a regular aerobic exercise program.
Some studies suggest that for the greatest heart protection, it is not the duration of a single exercise session that counts but the total daily amount of energy expended. Therefore, the best way to exercise may be in multiple short bouts of intense exercise.
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, most likely because it raises HDL levels-the so-called good cholesterol. (Note, however, it may take up to a year of sustained exercise to make any significant difference on HDL levels.)
Aerobic exercise appears to open up the blood vessels and, in combination with a healthy diet, may improve blood-clotting factors.
Resistance (weight) training offers a complementary benefit to aerobics by reducing LDL levels (the so-called bad cholesterol).
Exercises that train and strengthen the chest muscles may prove to be very important for patients with angina.

Effects of Exercise on Blood Pressure. 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.

High-intensity exercise may not lower blood pressure as effectively as moderate intensity exercise. The following are some observations that support this approach:

In one study, 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 Yoga and 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.

Effects of Exercise on Stroke. The benefits of exercise on stroke are less established than on heart disease, but recent studies are suggesting a positive association:

According to one analysis of a group of 11,000 men, those who burned between 2,000 and 3,000 calories a week (about an hour of brisk daily walking five days a week) cut their risk for 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.
A 2000 study of women also found substantial protection from brisk walking or striding (rather than casual walking.)

Effects of Exercise on Heart Failure. 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.

Studies continue to report benefits from exercise training. In one study, heart failure patients as old as 91 years old increased their oxygen consumption significantly after six months of supervised treadmill and stationary bicycle exercises.
Progressive resistance training may be particularly useful for heart failure patients since it strengthens muscles, which commonly deteriorate in this disorder. Even simply performing daily handgrip exercises can improve blood flow through the arteries.

Experts warn, however, that exercise is not appropriate for all heart failure patients.

WHAT ARE THE EFFECTS OF EXERCISE ON 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.

Benefits of Exercise for People with Diabetes

People with diabetes are at particular risk for heart disease, so the heart protective effects of exercise are very important for this patient population. Moderate exercise, in fact, protects the heart in people with type 2 diabetes, even if they have no risk factors for heart disease other than diabetes itself.
Regular exercise, even of moderate intensity, improves insulin sensitivity. One study reported that yoga helped patients with type 2 diabetes reduce their need for oral medications.
Studies suggest that regular, moderate, aerobic exercise lowers the risk for developing diabetes in the first place in overweight people, even if they don't lose weight. Lifestyle changes that include both exercise and weight loss can prevent diabetes even in high-risk individuals.
There is some indication that aerobic exercise before and during pregnancy can lower glucose levels and may be protective for women at risk for or who have gestational diabetes. (Any pregnant woman should check with her physician before embarking on a vigorous exercise regimen.)

Some Precautions for People with Diabetes Who Exercise

The following are precautions for all people with diabetes, whether type 1 or 2:

Because people with diabetes are at higher than average risk for heart disease, they should always check with their physicians before undertaking vigorous exercise. For best and fastest results, frequent high-intensity (not high-impact) exercises are best for people who are cleared by their physicians. For people who have been sedentary or have other medical problems, lower-intensity exercises are recommended using regimens designed with physicians.
Strenuous strength training or high-impact exercise is not recommended for uncontrolled diabetes. Such exercised exercises can strain weakened blood vessels in the eyes of patients with retinopathy. High-impact exercise may also injure blood vessels in the feet.

Patients who are taking medications that lower blood glucose, particularly insulin, should take special precautions before embarking on a workout program.

Glucose levels swing dramatically during exercise, people with diabetes should monitor their levels carefully before, during, and after workouts.
Patients should probably avoid exercise if glucose levels are above 300 mg/dl or under 100 mg/dl.
To avoid hypoglycemia, diabetics should inject insulin in sites away from the muscles they use the most during exercise.
They should also drink plenty of fluids. Before exercising, they should also avoid alcohol, which increases the risk of hypoglycemia.
Insulin-dependent athletes may need to decrease insulin doses or take in more carbohydrates prior to exercise but may need to take an extra dose of insulin after exercise. Stress hormones released during exercise may increase blood glucose levels, in non-diabetics insulin is released to control this. The diabetic therefore needs to test their blood sugar and take an extra dose as instructed by their diabetes healthcare provider.

EFFECTS ON MUSCLES, BONES, AND JOINTS

Muscle strength declines as people age, but studies report that when people exercise they are stronger and leaner than others in their age group.

Effects on Osteoarthritis

One study on patients with osteoarthritis compared one group who embarked on an aerobic and resistance exercise program with another that received patient education only. The exercising group developed less disability and pain and showed a better ability to perform physical tasks. Although strong evidence for the benefits of exercise on osteoarthritis is lacking, there are some reasons to believe that arthritis can be improved with activity:

Low-impact aerobics 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.
Strengthening exercises build muscle strength while burning fat and maintaining bone density. Some experts encourage patients to emphasize strengthening leg muscles as a first treatment step, even before using pain relievers. They fear that patients who rely on pain killing drugs may overuse knees, which do not have muscle tissue sufficiently strong enough to protect the joints from further damage.
Range-of-motion exercises increase the amount of movement in a joint and muscle. In general, they are stretching exercises. The best examples are Yoga and Tai Chi, which focus on flexibility, balance, proper breathing. They also lower stress levels, help to reduce blood pressure, and may even have beneficial effects on cholesterol levels.

Warning Note: Osteoarthritis patients should avoid high-impact sports such as jogging, tennis, and racquetball. They should strive for short but frequent exercise sessions guided by physical therapists or certified instructors.

Effects on Osteoporosis (Loss of Bone Density)

Benefits of Exercise on Osteoporosis. Exercise is very important for slowing the progression of bone loss (osteoporosis) and reducing the risk for falls that cause fractures. Older women are at highest risk for this disease but older men are also at risk. Children should begin exercising before adolescence, since bone mass increases during puberty and reaches its peak between ages 20 and 30. In fact, one study suggests that exercise may help increase bone mass in teenagers even more effectively than high calcium intake.

Specific exercises may be especially helpful for preserving or building bone or both:

Weight-bearing exercise are very beneficial for bones in people of all ages, even older people. This approach applies tension to muscle and bone, and the body responds to this stress by increasing bone density, in young adults by as much as 2% to 8% a year. Careful weight training can also be very beneficial for elderly people, particularly women. In addition to improving bone density, weight-bearing exercise reduces the risk for fractures by improving muscle strength and balance, thus helping to prevent falls.
Regular brisk long walks improve bone density and mobility. In older women, even moderate exercise (as little as an hour a week) helps reduce the risk for fracture. (Everyone who is in good health should aim for more, however.)
Exercises specifically targeted to strengthen the back can be beneficial in improving posture and may even reduce kyphosis (hunchback) in people with osteoporosis.
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.

Female Athlete Triad. Some young female athletes who exercise very intensely and are subject to intense pressure to remain thin are at risk for the so-called female athlete triad. This triad of symptoms includes menstrual dysfunction, eating disorders, and osteoporosis. Eating disorders among young female athletes is estimated at 15% to 62%. Women at higher risk include ballet dangers, gymnasts, and divers. Continued intense exercise causes a stress response in which estrogen (the primary female hormone) declines. Estrogen loss then can lead to infertility and osteoporosis. Iron depletion and anemia may also be a problem in women who exercise frequently, even at moderate intensity. A physician should be consulted for any of these concerns.

Effect of Exercise on Back Pain

Effects of Sedentary Life. People who do not exercise regularly face an increased risk for low back pain, especially during times when they suddenly embark on stressful unaccustomed activity, such as shoveling, digging, or moving heavy items. Although no definitive studies have been done to prove the relationship between lack of exercise and low back pain, sedentary living is probably a primary nonmedical culprit contributing to this condition. Lack of exercise leads to the following conditions that may threaten the back:

Muscle inflexibility (can restrict the back's ability to move, rotate, and bend).
Weak stomach muscles (can increase the strain on the back and can cause an abnormal tilt of the pelvis).
Weak back muscles (may increase the load on the spine and the risk for disc compression).
Obesity, associated with sedentary lifestyle (puts more weight on the spine and increases pressure on the vertebrae and discs). Studies report only a weak association between obesity and low back pain, however.

Benefits for Chronic Back Pain. People in with sudden and severe back pain should not exercise. Specific exercises can be important during recovery, however, as well as for patients with chronic low back pain. In one study, for example, patients with back pain lasting for an average of 18 months were assigned eight one-hour exercise sessions over four weeks. They showed greater improvement in nearly every area, including reduced pain and increased capacity, compared to patients who did not exercise. In another study, patients who chose a passive route (massage and heat therapy) experienced slower recovery from pain than those who exercised (although after a year their conditions did not appear to differ much). Some studies suggest that the positive impact of exercise on low back pain does not depend on improving strength and flexibility but on changing the patients' attitudes toward their disability and pain. Some exercise programs used for prevention or for chronic low back pain include the following:

Low Impact Aerobic Exercises. Low-impact aerobic exercises, such as swimming, bicycling, and walking, can strengthen muscles in the abdomen and back without over-straining the back. Programs that use strengthening exercises while swimming may be a particularly beneficial approach for many patients with back pain.
Lumbar Extension Strength Training. Exercises called lumbar extension strength training are proving to be effective. Generally, these exercises attempt to strengthen the abdomen, improve lower back mobility, strength, and endurance, and enhance flexibility in the hip and hamstring muscles and tendons at the back of the thigh.
Yoga, Tai Chi, and Chi Kung. These practices combine low-impact physical movements, breathing exercises, and meditation. Some studies suggest they may be very helpful in preventing recurrences of lower back pain.
Flexibility Exercises. Whether flexibility exercises alone offer any significant benefit is uncertain. One study suggested that any benefits derived from flexibility exercises are lost unless the exercise regimens are sustained.
Retraining Deep Muscles. Of interest are studies that are finding a link between low back pain and impaired motor control of deep muscles of the back and trunk. According to these studies, contraction exercises specifically designed to retrain these muscles may be effective for patients with both acute and chronic pain.

It is important for any person who has low back pain to have an exercise program guided by professionals who understand the limitations and special needs of back pain and who can address individual health conditions. One study indicated that patients who planned their own exercise did worse than those in physical therapy or physician-directed programs.

Hazardous Effects on the Back. On the other side of the coin, improper or excessive exercise is also an important risk factor for back pain. [For more information see What Are the Hazards of Exercise?]

WHAT IS THE EFFECT OF EXERCISE ON CHRONIC LUNG DISEASE AND ASTHMA?

Unsurprisingly, patients with chronic lung problems have difficulty exercising. Shortness of breath is a major limitation in most patients, but in about a third, muscle fatigue is an even greater problem. Although exercise does not improve lung function, training helps many patients with chronic lung disease by strengthening their limb muscles, thus improving endurance and reducing breathlessness.

Effects of Exercise on Asthma

Some studies are indicating that long-term exercise may help control asthma and reduce hospitalization. One 2000 study found that aerobic exercise improves breathing capacity and function in-patients with mild asthma. People who enjoy running should probably choose an indoor track to avoid pollutants. Swimming is particularly excellent for people with asthma. Yoga practice, which uses both stretching, breathing, chest expansion, and meditation techniques may have specific benefits that include stress reduction as well as airway opening. One study reported that two thirds of patients who practiced yoga regularly were able to reduce or eliminate their asthma medications.

Exercise-Induced Asthma. About 40% to 90% of asthma cases are exercise-induced asthma (EIA), in which exercise triggers coughing, wheezing, or shortness of breath. It occurs most often in children and young adults and during intense exercise in cold dry air. EIA is triggered only by exercise and is distinct from ordinary allergic asthma in that it does not produce a long-term increase in airway activity (as allergic asthma does). People who only have EIA, then, do not require long-term maintenance therapy. (Some people, however, have both types.) There is some evidence that patients with EIA may also experience an asthmatic response hours after physical activity; more research is needed to confirm this. The warm-up and cool-down periods, which are important for any exercise regimen, may help reduce EIA events. A study of military recruits found that exercise-induced asthma attacks did not hinder their ability to perform or train, suggesting that EIA is not a reason to exclude people from physically demanding occupations.

Effects of Exercise on Emphysema

Walking is the best exercise for people with emphysema. Patients should try to walk three to four times daily for five to 15 minutes each time. Devices that assist ventilation may reduce breathlessness that occurs during exercise. Using breathing patterns that involve a long slow exhalation and a rapid inhalation may improve the ventilation in the lungs of these patients. As with asthma, yoga or martial arts exercises, such as tai chi, that emphasize breathing techniques and balanced movements may be particularly beneficial for these patients.

WHAT EFFECT DOES EXERCISE HAVE ON OBESITY AND WEIGHT LOSS?

Exercising helps people reduce their weight, maintain weight loss, and can help 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. Losing weight requires both exercise and calorie restriction. In addition, if a person exercises but doesn't diet any actual pounds lost may be minimal because dense and heavier muscle mass replaces fat.

Nonetheless, regardless of weight loss, a fit body will look more toned and be healthier. And exercise even without dieting adds benefit. For example, one study found that overweight but fit people have half the death rate of overweight and unfit people. And, studies suggest that people who have trained for a long time develop more efficient mechanisms for burning fat and are able to stay leaner.

The following are some suggestions and observations on exercise and weight loss:

The treadmill burns the most calories of standard aerobic machines. It may be particularly effective when used in short multiple bouts during the day. In fact, exercise sessions as short as 10 minutes in duration that are done frequently (about four times a day) may be the most successful program for obese people.
Even vigorous workouts do not immediately burn great numbers of calories. The metabolism remains elevated after exercise, however, and the more strenuous the exercise, the longer the metabolism continues to burn calories before returning to its resting level. This state of elevated metabolism can last for as little as a few minutes after light exercise to as long as several hours after prolonged or heavy exercise.
Resistance, or strength, training should be included in any regimen. If performed two or three times a week, it is excellent for replacing fat with muscles.
Fidgeting may be very helpful in keeping pounds off. Regular exercise is certainly the best course, but for people who must sit for hours at work, frequently shifting positions while sitting may have some benefit.
Exercise improves psychological well being and replaces sedentary habits that usually lead to snacking. Exercise may even act as a mild appetite suppressant. People who exercise are more apt to stay on a diet plan.
It is important to realize that as people slim down, their initial level of physical activity becomes easier and they burn fewer calories per mile of walking or jogging. The rate of weight loss slows down, sometimes discouragingly so, after an initial dramatic head start using diet and exercise combinations. People should be aware of this phenomenon and keep adding to their daily exercise regimen.
As people age, they also need to exercise more to keep off the same amount of weight.
Changes in fat and muscle distribution may differ between men and women as they exercise. Men tend to lose abdominal fat (which lowers their risk for heart disease faster than reducing general body fat). Exercise, however, does not appear to have the same effect on weight distribution in women. In one interesting study women who underwent aerobic and strength training lost fat in their arms and trunk, but did not gain muscle tissue in these regions. On the other hand, they gained muscles but achieved no change in fat mass in their legs.

Warning Note. Because obesity is one of the risk factors for heart disease, so anyone who is overweight must discuss their exercise program with a physician before starting.

WHAT EFFECTS DOES EXERCISE HAVE ON OTHER CONDITIONS?

Effect of Exercise on Cancer

A number of studies have indicated that regular, even moderate, exercise may reduce the risk of colon cancer and, in fact, any cancer related to obesity. A number of studies have also suggested that regular exercise, particularly if it is vigorous, reduces risks against breast cancer in women and prostate cancer in men.

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.

Effects on Infectious Illness

Although long-term effects of regular exercise are known to improve health, the immediate effect of exercise on the immune system is uncertain. In people who already have colds, exercise has no effect on the illness' severity or duration of the infection. However, people should avoid strenuous physical activity when they have high fevers or evidence of viral illness. 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.

Effects on the Gastrointestinal Tract

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. For example, in one 2000 study, exercise was associated with a lower risk for ulcers in men (although not in women.) Older people who exercise moderately may have a lower risk for severe gastrointestinal bleeding.

Effects on Neurologic Diseases and Mental Decline

A 2001 study reported that older people who regularly exercised had lower rates of mental deterioration, Alzheimer's, and dementia of any type. Aerobic exercise is linked with improved mental vigor, in all people, 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. Another study found that walking regularly protects women from mental decline, and in fact, the more they walked per week, the more protection they enjoyed. (Stretching and weight training appear to have no such effects.)

People with existing neurologic diseases, such as 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.

Effects on Emotional Disorders

Although there is little strong evidence that exercise can help manage depression, a number of studies have suggested benefits. The following are some examples:

A 2000 study reported that 30 minutes of brisk exercise three times a week may be just as effective as medication in relieving the symptoms of mild to moderate depression and reduces the risk of relapse.
A 1999 study on exercise in the elderly reported that after 26 weeks, exercise was as effective as antidepressants. (Antidepressants relieved depression earlier, however.)
One study found that teenagers who were active in sports have a greater sense of well being than their sedentary peers; the more vigorously they exercised, the better their emotional health.

Specific exercises may be particularly beneficial:

Aerobics. Either brief periods of intense training or prolonged aerobic workouts can raise chemicals in the brain, such as endorphins, adrenaline, serotonin, and dopamine, that produce the so-called runner's high. And, of course, weight loss and increased muscle tone can boost self-esteem.

Yoga. Yoga practice, which involves rhythmic stretching movements and breathing have been found to positively affect mood and may have clinical potential as a technique for improving and stabilizing mood. One study, in fact, suggested that men actually may have better results with yoga than with aerobic exercise. In the study men experienced significantly lower levels of tension, fatigue, and anger after yoga than after swimming. (Yoga and swimming tended to produce equal benefits in women.)

Effect of Exercise on Pregnancy

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 generally recommend the following precautions for pregnant women who exercise:

Fit women who have exercised regularly before pregnancy may work out intensely as long as the physician approves and no discomfort occurs.
As a rule, for previously sedentary low-risk expectant mothers, the pulse rate should not exceed 70% to 75% of the maximum heart rate or more than 150 beats per minute. (In one study, such women exercised to 150 to 156 beats per minute three times a week without any harmful effects, but any woman should check with their physician before embarking on such a program.)
According to one study, vigorous exercise may improve the chances for a timely delivery. All pregnant women, however, 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.)

The following are specific exercises that may benefit the pregnant woman:

Swimming and water aerobics may be the best option for most pregnant women. Swimming has 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 six times a day. This involves contracting the muscles around the vagina and urethra for three seconds 12 to 15 times in a row.

WHAT ARE THE HAZARDS OF EXERCISE?

Effect of Strenuous Exercise on the Heart

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. The great majority of these heart events occur in high-risk individuals. For example, 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 declines for those who get in shape gradually and stay fit through regular activity. [For detailed information see Box Heart Attack and Sudden Death from Strenuous Exercise.]

Injuries from High Impact Exercise

Competitive running or high-impact aerobics pose a high risk for a number of injuries in bones and muscle. High-impact exercise can also damage the inner ear, causing dizziness, ringing in the ear, motion sickness, or loss of high-frequency hearing. The effect of high-impact exercise on the back is not entirely clear. Some research suggests that over time, it may increase the risk for degenerative disc disease. A survey of people who played tennis, however, found no increased risk for low back pain or sciatica.

Some research further suggests that in people unused to exercise, intense activity increases production of harmful particles in the body called oxygen free radicals. These unstable particles bind to other molecules and injure muscle tissue. Muscle pain in this case is delayed for 24 to 48 hours after exercise.

The following are people at higher than average risk for high-impact injuries:

About half of people at any age who participate in competitive running or high impact aerobics experience minor injuries at least once a year. Young, intensely competitive athletes may be at risk for permanent injury. Studies are conflicting over whether intensive high impact sports in younger people cause long-term degenerative joint disease.
As more older people start exercising, there has also been a risk for injuries. Between 1990 and 1996, injuries from active sports increased by 54% in people age 65 and older.
Women are far more likely than men to suffer knee injuries. Urinary incontinence also affects many female athletes who engage in high-impact exercise.
Tennis players are at high risk for injuries from repetitive force on the shoulder joint.
Preventing High Impact Injuries. Even young people are at risk for injury form high-impact exercise. The following may be helpful for preventing injury:
Wear shock-absorbing footwear with weight-dampening inserts.
Combine weight lifting with jumping exercises. This may prevent injury by strengthening hamstrings and improving coordination.
Vary training and alternate easy and harder workouts.
Be careful to warm up, cool down, and stretch. Flexibility is the key to preventing many muscle strains.
Take days off now and then. The risk of injury increases when athletes train more than five times a week.

Because of the association between high-impact exercises and oxidation, some experts suggest that eating foods rich in antioxidants, such as vitamins A, C, and E, may be worth trying. Such foods include many fresh fruits and vegetables, and are certainly recommended in any case.

Treating Minor Injuries. Most mild or moderate injuries respond well to a simple, four-step treatment: rest, ice, compression, and elevation (RICE). This regime works well for both spot injuries and chronic problems. Ice packs, which minimize inflammation and pain, can help acute injuries and can be useful for the first few hours after a chronically injured area is exercised. Heat, ultrasound, whirlpool, and massage may speed healing if applied a day or two after the initial injury or for warm-up before another workout session.

Improper Mechanics and Hazardous Effects on the Back and Shoulders

Incorrect movements can literally cause mechanical problems in the muscles. They are usually the result of improper exercise instruction and inattention. As examples, a single jerky golf swing or incorrect use of exercise equipment (especially free weights, nautilus, and rowing machines) can cause serious back injuries.

Between 30% and 70% of cyclists experience low back pain. (One 1999 study reported that 70% of cyclists reported improvement simply by adjusting the angle of the bicycle seat.)

Dehydration

Everyone should drink lots of fluid during intense exercise. Thirst is often a poor indicator of dehydration in people who exercise, particularly older people, and they often underestimate the amount of fluid they need. During a tough workout in a hot environment, the body can lose two liters of fluid per hour through sweat. Anyone who exercises intensively should take the following precautions:

Drink six to eight ounces of fluid about 15 minutes before a workout, and then pause regularly during exercise for more.
Water is the best choice for replenishing body fluids. Glucose-sodium-potassium solutions, the so-called "sports drinks," that promise instant energy are apparently no better than water at improving endurance during prolonged intense running. Studies on two of these drinks (Endurox, Sports) reported no benefit from their use.
Caffeinated beverages like coffee and soft drinks give short bursts of energy but can actually reduce fluid. According to one study, caffeine before a workout temporarily raises blood pressure and reduces blood flow to inactive limbs.

Contrary to popular belief, drinking fluids will not cause cramps. Adequate hydration, in fact, helps prevent the painful involuntary muscle spasms that sometimes occur during exercise.

Hyperthermia (Overheating)

Overheating, or hyperthermia, can be a problem with strenuous exercise or when working out in hot weather. Overheating can cause mild to life-threatening conditions. Heat exhaustion, a moderate form of hyperthermia, is characterized by the following symptoms:

Lightheadedness, nausea, headache, hyperventilation, fatigue, and loss of concentration.
A high temperature (above 103° F), possibly accompanied by complaints of chills and clammy skin.

Individuals should rest in a cool, dry place, drink plenty of fluids, and bring down their body temperature with ice packs pressed against the skin.

Heatstroke. Heatstroke is the most dangerous complication of hyperthermia. The victim may suddenly cease sweating, after which symptoms such as altered consciousness, seizures, and even coma, may quickly follow. Heat stroke is a medical emergency and requires immediate cooling of the victim in an ice-water bath or with ice packs. One study suggests that risk for serious complications from exercising in high temperatures may persist as late as the following day, even if the weather has cooled down.

Frostbite and Hypothermia

Precautions also need to be taken in cold weather. When exercising in winter, dress in layers, including gloves and socks, which create insulated air pockets that trap heat. In cold weather, wear shoes with less ventilation than those worn in the summer. Fingers, toes, ears, and nose are most susceptible to frostbite. From stinging or aching, frostbite progresses to numbness. Fingers and toes may become white. Soaking the extremities in warm water can help, but only once there is no risk of refreezing, since a second bout of frostbite after thawing can accelerate tissue damage. Hypothermia can be life threatening and can occur even after prolonged exposure to temperatures that are above freezing. The condition is characterized by extreme fatigue, mental confusion, apathy, and a lack of coordination. The victim should be warmed as soon as possible with blankets, body heat, and warm fluids.

HOW CAN A PERSON BE MOTIVATED TO EXERCISE?

Motivating Children

In a 2001 study, children between the ages of three to 17 averaged at least 30 minutes of moderate exercise daily and at least 60 minutes of low-intensity activity. These encouraging results were unexpected and differed from previous studies which showed far less average activity among children. Still, they still do not meet the standards for aerobic activities. Experts state that children should be vigorously active for at least 20 to 60 minutes three to five days a week. Parents and educators must become more involved to offset cultural pressures that prevent activity.

Role of Parents. Parents must make conscious efforts to oppose cultural pressures on their children, such as television, computers, and video games, not only for their children, but themselves. Even children who aren't interested in joining a Little League team may enjoy a round of catch with their parents, walking in the park, or swimming in a local lake.

Role of Schools . Early school physical education programs can make a significant difference and the earlier these routines are learned, the more likely they will be carried forth into a healthy adulthood. Schools should emphasize team cooperation or individual improvement and self-mastery. Studies have shown that people tend to give up more quickly and feel less competent if their perceptions of success are based only in comparison to their peers. Unfortunately, many school officials equate physical health only with athletic success. And, even athletically gifted youngsters often fail to continue training after graduation once they lose the encouragement of coaches and fans, their only gauge of self-worth.

People mature at different rates, and there seems to be a genetic component to coordination, strength, speed, and one's response to resistance exercise. Nonetheless, everyone should strive to be as fit as they possibly can, given their strengths and limitations.

Motivating Adults

In a 2001 report, only 25.4% of adults reported that they engaged in recommended levels of activity; nearly 46% reported insufficient exercise and 28.7% were sedentary. These trends had remained steady for eight years, from 1990 to 1998.

Weight loss is the greatest motivator to exercise for women and muscle tone is the primary motivator for men. Unfortunately, cosmetic effects may take a long time to become apparent, discouraging people from continuing even though their health is improving. Much more important should be the health benefits exercise has for everyone.

Even small efforts can boost fitness levels and lay the groundwork for a healthy lifestyle. Some motivational tips are as follows:

Think of exercise as a "menu" rather than a "diet." Choose a number of different physical activities that are personally enjoyable, such as sports, dancing, or biking.
Stick to a prepared schedule and record progress.
Develop an interest or hobby that requires physical activity.
Adopt simple routines, like climbing the stairs instead of taking the elevator, walking instead of driving to the local newsstand, or canoeing instead of zooming along in a powerboat.
Try cross training (regularly switching from one type of exercise to another). Studies suggest it is more beneficial than focusing only on one form of exercise.
Exercise with friends.
Join a gym or take classes. Many affordable programs are available.
For those who can afford them, personal trainers can be very helpful and are available in many gyms and exercise clubs. 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.

WHERE ELSE CAN INFORMATION BE OBTAINED ON EXERCISE?

Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Division of Nutrition and Physical Activity. 4770 Buford Highway, NE, MS K-46, Atlanta, Georgia 30341-3717. Call (888-CDC-4NRG) or on the Internet 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 91403-3297. Call (800-BE-FIT86) or (800 YOUR BODY) or on the Internet (www.afaa.com)

American Council on Exercise, 4851 Paramount Drive, San Diego, California 92123. .Call ((800) 825-3636) or on the Internet (http://www.acefitness.org/).
Organization provides information on exercise and gives names of personal trainers in local areas.

Nicholas Institute of Sports Medicine and Athletic Trauma, 130 East 77th Street 10th Floor, New York, NY 10021. Call (212) 434-2700 or (http://www.nismat.org/)
A website from the first hospital-based facility dedicated to sports medicine. (Located at Lenox Hill in New York City.) Has excellent information on sports injuries, prevention, and treatment.

Shape Up America! 6707 Democracy Blvd, Suite 107, Bethesda, Maryland 20817. On the Internet (http://www.shapeup.org/sua/).
Excellent site founded by Everett Koop, MD to educate the public on fitness and health. Offers a number of calulators for body fat and results give risk group. Many fact sheets and good links are available.

Only on the Internet

Offers a number of calculators for weight and exercise (http://www.self.com/calculators/ )

Ivillage (http://www.ivillage.com/diet/experts/fitfriday/archive/)

RECENT LITERATURE

Review Date: March 2002

This Report Reviewed by:

Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

Stephen A. Cannistra, MD, Oncology, Associate Professor of Medicine, Harvard Medical School; Director, Gynecologic Medical Oncology, Beth Israel Deaconess Medical Center

John E. Godine, MD, PhD, Metabolism, Harvard Medical School; Associate Physician, Massachusetts General Hospital

Edwin Huang, MD, Gynecology, Harvard Medical School; Physician, Massachusetts General Hospital

Daniel Heller, MD, Pediatrics, Harvard Medical School; Associate Pediatrician, Massachusetts General Hospital; Active Staff, Children's Hospital

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Theodore A. Stern, MD, Psychiatry, Harvard Medical School; Psychiatrist and Chief, Psychiatric Consultation Service, Massachusetts General Hospital

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