Protective effects of exercise: Many studies have found an inverse relationship between exercise and many types of cancer. Exactly how exercise protects individuals against various cancers is difficult to determine. A number of logical theories have been presented.
Regular exercise has a positive effect on the blood by lowering glucose and insulin levels and improving white blood cell function. Hormonal changes include an increase in steroid hormones from the adrenal cortex and improvements in the insulin effects on cancer-fighting T cells. Exercise is also believed to improve vitamin C metabolism. All of these effects could protect the body from cancer.
A more complex area where benefits are likely is cell division, which is rapid in cancers. Exercise increases anti-inflammatory cytokines, which decrease cell division. It also has beneficial effects in preventing the activation of cancer genetic material called oncogenes. Another effect is the promotion of interferon production, which decreases viral reproduction. By decreasing cell reproduction, exercise may slow cancer growth.
Rehabilitation effects of exercise: The main goal of exercise for those who have cancer is to maintain or improve the physical capabilities of the body, resulting in an improved quality of life during and after treatment. No obvious effects of exercise on the immune system of cancer patients have been identified at this time. Some of the immediate effects of exercise on the cancer patient are decreased nausea and lessened symptoms of fatigue.
Part of the goal of exercise for cancer patients is to protect them from other health problems. Exercise helps them maintain healthy weights by decreasing fat but also decreasing the loss of muscle due to inactivity and treatments. Exercise increases blood flow throughout the body, reducing blood clot formation, particularly in the legs. Longer-term health risks such as osteoporosis (loss of bone) and cardiovascular disease are lowered by regular exercise.
Psychological benefits can also be obtained by cancer patients who exercise. Decreased anxiety and depression and improved self-esteem have been found. The ability to be more independent and do normal daily activities can contribute to this improved psychological state. With all of these potential benefits, cancer patients are advised to participate in exercise programs with individualized exercise prescriptions.
Exercise prescription and cancer: Cancer patients must check with their physicians before beginning an exercise program. It is generally recommended that patients first complete a supervised exercise test to determine which types of exercise can be done safely. Exercise tests should not be conducted if the patient has dizziness, shortness of breath, fever, or nausea and vomiting. Exercise tests are usually conducted on a treadmill or stationary bicycle, paying close attention to symptoms and fatigue. This is not be a maximal test to exhaustion but rather a submax test.
The information obtained from the exercise test is used to complete an exercise prescription. Mode, frequency, intensity, duration, and progression are considered. The type of exercise recommended includes activities that work the large muscle groups such as walking and cycling. It is recommended that cancer patients exercise three to five times per week. In cases in which patients have low levels of conditioning, shorter sessions are attempted every day. Cancer patients are advised to exercise at a lower intensity than the general population. For healthy people, the typical heart rate range considered desirable for exercise is 70 to 85 percent of maximum heart rate, and in cancer patients, it is 60 to 70 percent of maximum heart rate. The recommended duration of the exercise session is twenty to thirty continuous minutes. However, many cancer patients may not be able to exercise that long. In these cases, the patients can space out the twenty to thirty minutes with periodic rest intervals. The goal is gradually to shorten the length and frequency of rest periods until the patient can complete the exercise session without stopping. In the healthy population, people progress by gradually increasing intensity, duration, or frequency. This may not be possible for cancer patients because of treatments that may cause regression. Therefore periodic modifications in the exercise program may need to be made.
Several precautions are advised for cancer patients. Treatments frequently lower blood counts, resulting in increased risk for infections, anemia, and bleeding. Blood counts are monitored during treatment and used to determine appropriate exercise times. Patients are advised to stop exercise during periods of low blood counts. Sodium and potassium levels can decrease with excessive vomiting. This decrease can lead to other health complications, and exercise should be avoided during these times. Treatments also can cause severe fatigue. When patients are fatigued, less intense exercise, or a break in exercise, is appropriate.
For cancer patients, lifting heavy weights and exercising on uneven floors that can affect balance are not advised. Conditions that warrant contacting a physician are swollen ankles; unexplained weight loss; shortness of breath with low-level activity; or exercise-induced nausea, vomiting, or unrelieved pain. Dizziness or blurred vision that does not go away with rest needs immediate attention from a physician. By paying attention to these safety measures, cancer patients can exercise safely and effectively.
Exercise, cancer, and fatigue: Cancer treatments such as chemotherapy and radiation cause fatigue in most patients. Incorporating exercise into the treatment gives the expectation of greater fatigue and less willingness to participate. However, appropriate, low-level aerobic exercise can actually decrease fatigue. Strategies exist to improve exercise adherence during cancer treatments.
One important factor is rest. Physical activity and rest must be balanced so there is no interference with nighttime sleep. This is best accomplished with a regular daily routine in which exercise takes place during times when the patient feels best. Reducing stress with regular relaxation techniques is helpful, along with a balanced diet that includes adequate protein. Getting plenty of fresh air, such as exercising outside, is beneficial.
Perspective and prospects: Although much progress is being made in the fight against cancer, it will continue to be one of the major health problems. New drugs and other treatments to force cancer into remission will be developed, giving more hope to cancer patients. However, lifestyle interventions involving exercise, nutrition, and stress management can also be used to help treat and minimize treatment side effects. At the least, lifestyle interventions will improve the quality of life of cancer patients.
The correlation between cancer prevention and exercise has not been investigated to the same extent as exercise and cardiovascular disease. The cardiovascular benefits of exercise were found many years ago, and many studies have been conducted to determine the best exercise practices. As more research is conducted, the mechanisms for decreasing cancer risk will become more evident and the specific types of exercises associated with both prevention and treatment of specific cancers will be identified. This will give health professionals more options for fighting cancer and improving the quality of life for cancer survivors.
In the meantime, cancer patients can participate in appropriate exercise programs that include low-intensity aerobic activities. Health care professionals as well as exercise leaders and trainers need to be continually updated about cancer and the benefits of exercise as additional information is found. Cancer is a challenging disease and all strategies must be used to reduce risk and improve outcomes.
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