• Highlights
• Introduction
• Recommended Exercise Methods
• Exercise's Effects on the Heart
• Exercise's Effects on Diabetes
• Exercise's Effects on Bones and Muscles
• Exercise's Effects on the Lungs
• Exercise's Effects on Weight
• Exercise's Effects on Other Conditions
• Complications
• Motivation
• Resources
• References

Exercise

Description

An in-depth report on the benefits and types of exercise.

Exercise's Effects on Other Conditions

Effect of Exercise on Cancer

A number of studies have indicated that regular exercise may reduce the risk of breast, prostate, and colon cancer. Exercise not only lowers a woman's chance of getting breast cancer, it can help those who have received chemotherapy for the disease fight off fatigue. 

A 2004 study showed that prostate cancer cells have a 27% reduction in growth when exposed to exercise serum (blood serum taken from patients who exercise) compared to control serum, suggesting that exercise changes blood chemicals to be less hospitable to cancer cells.

Physical activity has been said to lower a man's risk of colon cancer, but data linking exercise to a lower risk in woman has been inconsistent. A 2006 study published in the International Journal of Cancer concluded that exercise may not reduce a woman's risk of colon cancer. Previous studies, including the Nurses Health Study and the American Cancer Society's Cancer Prevention Study II, found that exercise reduced a woman's risk of colon cancer by 30-40%. The prospective cohort study involved nearly 32,000 mostly postmenopausal women who were participating in a breast cancer trial. The women were given questionnaires and asked to rank their exercise habits according to light, moderate, and heavy activity. The study author says the conflicting result may be due to a misclassification of certain activities.

Effects on the Gastrointestinal Tract

Endurance athletes often report stomach problems, such as bloating, diarrhea, and gas, even at rest. Experts suggest 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.

Effects on Kidney Disease

Patients with end-stage kidney disease who exercise four to five times per week have better survival rates than those who are less active, researchers involved in the Dialysis Morbidity and Mortality Wave 2 study report. However, the majority of study participants said that severe physical limitations that prevented them from exercising that often.

Effects on Neurologic Diseases and Mental Decline

Studies have shown that regular exercise, particularly walking, helps reduce one's risk for memory loss. A 2005 study found that older men who walked less than a mile daily had a 71% higher risk of dementia than those who walked more than two miles a day. An earlier study found that walking regularly protects women from mental decline. To date, there are no clear theories for the apparent benefit, although a preliminary study in mice suggests that physical activity changes the way brain-damaging proteins are metabolized in the brain, thus slowing the development of Alzheimer's disease. (Stretching and weight training appear to have no such effects.)

Aerobic exercise has been linked with improved reaction time, perception , and math skills in people of all ages.

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

Some research has suggested that exercise may have antidepressant effects. Although there is little strong evidence that exercise can help manage depression, a number of studies have suggested benefits. Research findings include:

• Just 30 minutes of brisk exercise three times a week was as effective as medication in relieving the symptoms and reducing relapse in many patients with mild to moderate depression.
• Over half of older women with depression that did not respond to medication improved with 10 weeks of exercise. (About a third of women who did not exercise also improved during that time.)
• Studies on elderly, depressed patients report modest benefits from exercise, even in those who do not response to antidepressants. (Simply participating in a group activity may help improve mood.)
• 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.
• A 2003 study found that physical inactivity is strongly linked to depression in children 8 to 12 years of age.

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. 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. A study comparing yoga to aerobic exercise found that men have 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

Moderate exercise in healthy pregnant women does not increase the risk for miscarriage, preterm labor, or rupture of the membrane. Not exercising increases the risk for complications, including low-birth weight babies. Exercising increases the fetal heart rate, which in turn protects the baby.

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.

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 buildup. 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 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.

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 - 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. (Pregnant women should not use hot tubs or steam baths, which can cause fetal damage and miscarriage.)

Note: Strenuous exercise may affect the flavor of breast milk for a short time afterward. Nursing mothers who engage in such activity might want to wait about an hour after exercising before they feed their infant.

• Review Date: 3/6/2006
• Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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