We know exercise is good for us but how is it good for preventing cancer growth? What are some of the overall mechanisms of how exercise reduces cancer? What are the main types of exercise? What are some safety aspects and medical contraindications of exercising after a cancer diagnosis? How long after treatment should I exercise?
Two researchers, P. Rajarajeswaran and R. Vishnupriya explain what they discovered in their excellent review of the literature about exercise and cancer and they answer these questions. They found hundreds of relevant studies and they cite 97 of these. This is what they discovered.
โThere is strong evidence for reduced risk of colorectal and breast cancer with possible association for prostate, endometrial and lung cancer with increasing physical activity. In a growing body of research that has investigated exercise in cancer patients; dramatic improvements in physiologic and psychological functioning have been documented in patients participating in exercise programs1.โ
P. Rajarajeswaran and R. Vishnupriya in their review of the literature, entitled: Exercise in Cancer 1 provide useful information in terms of the mechanisms, type of exercise and contraindications.
Mechanisms for all Cancers
- Genetic predisposition of habitually active people. Constitutional factors influence athletic selection or interest in physical activity and susceptibility to cancer.
- Exercise-induced increase in antitumor immune defences. Exercise may increase number and activity of macrophages, lymphokine-activated killer cells and their regulating cytokines; it may increase mitogen-induced lymphocyte proliferation.
- Improved antioxidant defence systems. Strenuous exercise increases the production of free radicals, whereas chronic exercise improves free radical defences by up-regulating both the activities of free scavenger enzymes and antioxidant levels.
- Decreased circulating insulin and glucose. Decreased insulin and insulin-like growth factors. Increased exercise may decrease levels of insulin and bioavailable IGF-I, both of which enhance division of normal cells and inhibit cell death.
Main Types of Exercise
โThe main health related types of exercise are aerobic, resistance and flexibility. The best mode of exercise depends on the person’s goals, health status, and exercise history and cancer experience. Aerobic training is defined as a method of improving cardio-respiratory system (e.g. Cycling, walking)
Resistance training is defined as a method to maintain or improve muscular strength, endurance or power, which is performed against relatively high resistance and few repetitions. Resistance exercise is a potent physiological intervention to increase muscle mass and attenuate muscle wasting. Flexibility training is defined as a method of maintaining or improving length of the muscle.
Radiation and chemotherapy may cause scar formation in joint, which may result in limitation in range of motion and this limitation can be prevented and normal range of motion can be gained by flexibility training. The best mode of exercise for the patient with cancer on treatment has not been determined because of the lack of research. However, no mode of exercise has been determined to be harmful to patient with cancer on treatment either.โ
Contraindications to Exercise
โMedical screening should be conducted for all survivors prior to their participation in an exercise program. General contraindications to exercises are cardiovascular insufficiency (e.g. uncontrolled symptomatic heart failure, acute myocarditis, and recent myocardial infarction), acute infectious diseases, metabolic diseases (e.g. thyrotoxicosis, myxedema), mental or physical impairment leading to inability to exercise.[78]
In addition to general contraindication certain contraindication and precautions are specific to cancer survivors they are; Exercise within two hours of chemotherapy or radiation therapy as increased circulation may increase the effects of treatment, Intravenous chemotherapy within previous 24 hours is also a contraindication for cancer survivors.[80]
Survivors with anemia (Hemoglobin <8g/dl) should not exercise until anemia is improved (Hemoglobin >10g/dl),[81] Bedside exercise programs may be prescribed for these individuals with frequent and short sessions. Hematological values where Absolute Neutrophil count less then 0.5ร10 9ฮผl and Platelet count less then 50×109ฮผl is contraindication for exercise as well.[81] Acute onset of nausea during exercise and vomiting within previous 24-36 hours, unusual fatigability or muscular weakness, disorientation, blurred vision, faintness, pallor, night pain or pain not associated with injury are also signs of contraindication to exercise.[80]
Survivors with immunosuppressants should avoid public gyms until there white blood cell count return to safe level (>500/mm3),[80] bone marrow transplanted survivors should avoid exposure to public places with risk of microbial contamination for one year after transplantation.
Survivors with indwelling catheter should avoid resistance exercise of muscle in the area to avoid dislodgement of catheter. Survivors with significant peripheral neuropathies should avoid exercise of the part because of weakness or loss of balance, stationary bicycle may be used in this situation.[81]โ
Take Home Message
โThese studies suggest that physical activity may help cancer survivors live longer by: reducing the risk of cancer recurrence or slowing cancer progression and reducing the risk of other life threatening diseases including second primary cancers.1โ
- Rajarajeswaran P, Vishnupriya R. Exercise in cancer. Indian journal of medical and paediatric oncology : official journal of Indian Society of Medical & Paediatric Oncology. 2009;30(2):61-70.
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