2 / 2

    Numerous studies (9,12,15,16,21,26,37) have suggested that exercise, including light to moderate intensities, has many benefits for people with cancer. Some of the benefits of exercise include: increases in cardiovascular, pulmonary, and muscular functioning produced by regular exercise result in improved oxygen consumption, stroke volume, cardiac output, vascularization of muscles, lymphatic circulations, metabolic rate, muscle tone, strength, coordination, and balance (28). During cancer treatment, chemotherapy, radiation and surgery can cause lasting effects to various biological systems. The benefits of exercise for the systems of cardiovascular, pulmonary, musculoskeletal, and endocrine are discussed briefly below.

    During exercise, the heart pumps increased volumes of blood to supply oxygen and nutrients and remove carbon dioxide and metabolic wastes; the respiratory system handles an increased workload, exchanging oxygen and carbon dioxide between the blood and the atmosphere. The nervous system and various hormones have important roles as well, integrating the body's response to exercise and regulating the metabolic changes that occur in muscle and other tissues (19). Exercise appears to influence host defense against both viral infection and cancer. Exercise also causes the release of several cytokines involved in resistance to tumors, which may also influence the activity of cytotoxic cells.

    Moreover, stress influences resistance to tumor growth and some stress hormones released during exercise such as corticosteroids or catecholamines can modulate the ability of immune cells to kill tumor cells (18). Thus it can be postulated that exercise may influence host defense against tumor growth via directly or indirectly modulating the activity of cytotoxic cells. Most research in this area has focused on natural killer (NK) cells, with relatively less attention given to the effects of exercise on cytotoxic T lymphocytes and monocyte cytotoxicity (18).

    The decline in functional capacity experienced by 1/3 or more of cancer patients, regardless of the stages of the disease, can be attributed to hypokinetic conditions developed from prolonged physical inactivity. This hypokinetic condition may cause the reduction in the efficiency of the energy systems (metabolic pathways) that may lower the assimilation of energy substrates by the body that are essential for the daily task performance. Also the hypokinetic condition may have some effects on hormone levels that could lead to further homeostatic unbalance. These modifications that may occur due to physical inactivity could led to a malfunctioning of many systems within the body, which can also be correlated to high levels of fatigue experienced by the patient.

    Exercise has been suggested by many researchers (9,12,15,16,21,26,27) as a rehabilitative solution for energy loss in cancer patients. Defined as rhythmic contraction and relaxation of large muscle groups over an extended period of time, aerobic exercises have been shown to improve physical capabilities in cancer patients (13). In a study conducted by Dimeo et al. (13), the most significant results of the study was that the patients experienced a clear reduction of fatigue and could carry out normal daily activities without limitations.

    More often than not, cancer patients are not as active during and after treatment as they were before treatment, or even diagnosis. Reductions in activity cause muscle atrophy, changes in muscle properties, and reductions in bone density. Muscle atrophy and reduced bone density lead to diminished musculoskeletal strength and performance, and contribute to an increased risk for bone fractures and musculoskeletal injuries (2). Musculoskeletal atrophy and changes in muscle properties contribute to declines in cardiovascular efficiency. Declines in cardiac efficiency are reflected in increased heart rate and blood pressure at rest and with submaximal exercise. Reductions in cardiovascular efficiency combined with elevations in cholesterol levels and decreases in HDL levels from inactivity contribute to an increased cardiovascular risk profile (1).

    Declines in pulmonary function that result from inactivity may include a dulled ventilatory response, diminished airflow and respiratory muscle function, and impairments in gas exchange from ventilation/ perfusion mismatches, shunting, and declines in diffusion that predispose people to respiratory disease such as pneumonia (2).

    Some initial clinical concerns about exercise in cancer patients include: a) the potential immunosuppressive effects of vigorous exercise, b) the increased likelihood of pathological bone fractures arising from compromised bone integrity, c) possible worsening of cardiotoxicity from chemotherapy and/or radiation, d) severe pain, nausea, and fatigue that may be intensified by physical exercise, and e) the inability and/or unwillingness of cancer patients to tolerate exercise given their weakened physical and emotional condition (11). Despite all of these concerns, there is a growing body of evidence that shows how exercise can benefit cancer patients (9,12,15,16,21,26,27).

Can exercise help reverse the effects of cancer treatment?

    Cardiovascular benefits of exercise for cancer patients were shown to be evident in patients that had no signs of impaired cardiac function before cancer treatment (14). In this study, no patients in the training group developed clinical signs of cardiotoxicity during the 2 months after chemotherapy. For women with breast cancer, a fitness program that included aerobic exercise would decrease the risk of developing cardiovascular disease and osteoporosis (20). Because treatment for breast cancer often results in a decrease in natural or exogenous sources of estrogen, these women face a greater risk of developing cardiovascular disease and osteoporosis.

    Cancer treatment has been shown in some cases to be harmful to the cardiovascular system. The heart in a cancer patient becomes less efficient in pumping blood to organs and tissues, therefore compromising the ability to perform daily activities and reaching high levels of fatigue. Exercise can promote cardiovascular training again throughout aerobic activities, allowing the heart to become more efficient in supplying blood to the body, and lowering the levels of fatigue experienced by the patient.

    Pulmonary benefits from exercise in regards to the damage done by the cancer treatment is related to improvements in the lung volume, decreased work of breathing, and better ability for gas exchange. Athletic performance can be measured through many physiological variables observed in exercise training. However, most pulmonary function measures do not apply for this performance prediction. No substantial relationship appears between athletic performance and vital capacity, total lung capacity, or forced expiratory volume (17). The most useful adaptation is probably an increase in the endurance capacity of respiratory muscles. When the respiratory muscles become trained due to exercise, the patient would experience a relief of the heavy breathing due to the fact that energy expenditure by these muscles would be lowered. Also, a more efficient gas exchange ratio would proportionate a more effective oxygen distribution to the systems throughout the body.

    Given the fact that alveoli of a cancer patient are diminished in number, and compromised by alveolar septas thickening, the exercise effects on the cancer patient pulmonary system is not known. One hypothesis is that the alveoli regenerate due to a supposed increase in blood supply to this organ, however the septas thickening does not seem likely to be reversible.

    The side effects of cancer treatment on the musculoskeletal system have demonstrated physiological improvements from exercise interventions. The loss in lean body mass that is reported during cancer treatment is still not well explained. This reduction in skeletal muscle could be attributed to surgery reduction, treatment depletions, and inactivity during recovery. This loss in muscle may be responsible for the exertion of higher energy needed to produce enough contractile forces required during energy performance or during sitting or standing (13,21,25). Exercise may stimulate various benefits to the musculoskeletal system. Such benefits include the development of new healthy cells that will replace the healthy cells that died from the cancer treatment. This process has been shown to give patients the strength gains needed to perform daily activities, more motivation and energy, and improvement in the patient’s overall quality of life.

    The endocrine system appears to be a biological system that suffers severe consequences in regards to cancer treatments (mainly radiation). These alterations may lead the patients to experience future complications in systems other than the one already compromised by the illness. For example, the decreased production of hormones thyroxine and triiodothyronine have biological effects on oxygen consumption, the central and peripheral nervous system, skeletal and cardiac muscle, carbohydrate and cholesterol metabolism, and growth and development (30). Also, alterations in metabolism can potentially lead to future heart complications. Heart complications can occur because of the increased amount of cholesterol due to the decreased carbohydrate metabolism.

    Exercise interventions may have an important role in returning hormone levels back to pre-cancer levels. Exercise may stimulate release of hormones that may have been suppressed, as well as helping to increase the metabolic pathways efficiency that was compromised by cancer. All these alterations that may occur with exercise interventions could potentially help cancer patients to improve their functional capacities. Improvements in metabolism, fluid balance, oxygen transportation, and central and peripheral nervous system functioning would create an overall homeostasis. This homeostasis would possibly give the patient an overall feeling of wellness.

Conclusion

    Exercise may be one of the most potent interventions for cancer patients, but with this also comes risks. Not all exercises are created equal. To be effective and safe, exercise should be prescribed, and include these five criteria: 1) Status of the individual, 2) Type of exercise, 3) Intensity of exercise, 4) Frequency of exercise, and 5) Duration of exercise (5). Anaerobic and aerobic exercise training should be an integral component in the lifestyle of people fighting through or recovering from cancer.

    Because the latency period for some late toxicities is many years after completion of treatment, the consequences of permanent tissue damage across the lifespan are unknown (30). Exercise could possibly be a link physiologically that slows, or even reverses the effects of chemotherapy, radiation therapy, and surgery. More investigations still need to occur in the area of exercise as rehabilitation for cancer patients. Regardless, all the findings of the research up to now have shown that moderate exercise is beneficial for the cancer patients (cardiovascular, pulmonary, musculoskeletal, and endocrine systems included).

    Among the many symptoms associated with cancer and its treatment, fatigue is one of the most prevalent symptoms, and yet fatigue is the least understood. Clinically knowing that exercise has helped alleviate some or all of the feelings of fatigue in cancer patients, there remains a very promising future for research in the years to come.

References

1. American College of Sports Medicine: ACSM’s Guidelines for Exercise Testing and Prescription, 6th edition, Baltimore, Maryland: Williams & Wilkins Publishing Company, 2000.

2. American College of Sports Medicine: ACSM’s Resource Manual for Guidelines for Exercise Testing and Prescription, 3rd edition, Baltimore, Maryland: Williams & Wilkins Publishing Company, 1998.

3. Bryne J., J.J. Mulvihill, and M.H. Myers (1987) Effects of treatment on fertility in long-term survivors of childhood or adolescent cancer. New England Journal of Medicine, 317:1315-1321.

4. Burke M.B., G.M. Wilkes, and K. Ingwersen. Cancer chemotherapy; a nursing process approach 2nd edition. Sudbury, Massachusetts: Jones and Barlett Publishers, 1996.

5. CancerSource.com (Quabeck, 1994; Tait, 1990; Ginsberg and Comis, 1984; Seltzer, Goldstein, and Herman, 1983)

6. Carroll P.V., C.R. Emanuel, and M. Thorner (1998) Growth hormone deficiency in adulthood and the effects of growth hormone replacement: a review. Journal of Clinical Endocrine Metabolism, 83:382-395.

7. Chernecky C.C. and B.J. Berger. Advanced and critical care oncology nursing; managing primary complications. Philadelphia, Pennsylvania: W.B. Saunders Company, 1998.

8. Chipman J.J., A.F. Attanasio, and M.A. Birkett (1997) The safety profile of Growth Hormone replacement therapy in adults. Clinical Endocrinology, 46:473-481.

9. Courneya K.S. and C.M. Friedenreich (1999) Physical exercise and quality of life following cancer diagnosis: a literature review. Annuals of Behavioral Medicine, 21(2): 171-179.

10. Courneya, K. and C.M. Friedenreich (1997) Relationship between exercise pattern across the cancer experience and current quality of life in cororectal cancer survivors. The Journal of Alternative and Complementary Medicine, 3:215-226.

11. Courneya K.S., J.R. Mackey, and L.W. Jones (2000) Coping with cancer: can exercise help? The Physician and Sports Medicine, 28(5): 49-73.

12. Derman W.E., K.L. Coleman, and T.D. Noakes (1999) Effects of exercise training in patients with cancer who have undergone chemotherapy, abstracted. Medicine of Science and Sports and Exercise, 31(5): S368.

13. Dimeo, F.C., B. Rumberger, and J. Keul (1998) Aerobic exercise as therapy for cancer fatigue. Medicine and Science in Sports and Exercise, 30: 475-478.

14. Dimeo F.C., M.H.M. Tilmann, H. Bertz, L. Kanz, R. Mertelsmann, and J. Keul (1997) Aerobic exercise in the rehabilitation of cancer patients after high dose chemotherapy and autologous peripheral stem cell transplantation. Cancer 79(9), 1717-1722.

15. Durack E.P. and P.C. Lilly (1998) The application of an exercise and wellness program for cancer patients: a preliminary outcome report. Journal of Strength and Conditioning, 12(1): 3-6.

16. Durack E.P., P.C. Lilly, J.L. Hackworth (2000) Physical and psychosocial responses to exercise in cancer patients: a two-year follow-up survey with prostate, leukemia, and general carcinoma. Journal of Exercise Physiology (online) Accessed March 6, 2001
    (http://www.css.edu/users/tboone2/asep/jan12b.htm)

17. Hayward, R. Cardiopulmonary physiology: the physiological response at rest and during exercise. Greeley, Colorado: UNC, 1999.

18. Mackinnon, L.T. Advances in exercise immunology. Champaign, Illinois: Human Kinetics, 1999.

19. Microsoft Encarta Encyclopedia 99. Microsoft Corporation

20. Mock V., M.B. Burke, P. Sheehan, E.M. Creaton, M.L. Winningham, S. McKenney-Tedder, L.P. Schwager, M. Liebman (1994) A nursing rehabilitation program for women with breast cancer receiving adjuvant chemotherapy. Oncology Nursing Forum, 21:899-908.

21. Mock V., M.E. Ropka, V.A. Rhodes, M. Pickett, P.M. Grimm, R. McDaniel, E.M. Lin, P. Allocca, J.A. Dienemann, M.E. Haisfielf-Wolfe, K.J. Stewart, and R. McCorkle. (1998) Establishing mechanisms to conduct multi-institutional research - fatigue in patients with cancer: an exercise intervention. Oncology of Nursing Forum 25(8), 1391-1397.

22. National Cancer Institute (2000) Fatigue: PDQ Supportive care/ screening/ prevention information. (http://www.graylab.ac.uk/cancernet/)

23. Oliveria, S.A., and I. Lee (1997) Is exercise beneficial in the prevention of prostate cancer? Sports Medicine, 23(5): 271-278.

24. Otto S. Oncology Nursing, 3rd edition. St. Louis, Missouri: Mosby Publishing Company, 1997.

25. Reich, P.R. and J.E. Metcalf. The facts about chemotherapy: a guide for cancer patients and their families. Mount Vernon, New York: Consumer Reports Books, 1991.

26. Schultz K.H., C. Szlovak, and H. Schultz (1998) Implementation and evaluation of an ambulatory exercise therapy based rehabilitation program for breast cancer patients. Medical Psychology, 48:398-407.

27. Schwartz A.L. (1999) Fatigue mediates the effects of exercise on quality of life. Quality of Life Research, 6:529-538.

28. Smith S. (1996) Physical exercise as an oncology nursing intervention to enhance quality of life. Oncology Nursing Forum 23(5), 771-778.

29. Souhami R. and J. Tobias. Cancer and its management, 3rd edition. Malden, Massachusetts: Blackwell Science Ltd., 1998.

30. Yarbro C.H., M.H. Frogge, M. Goodman, and S.L. Groenwald. Cancer Nursing: principles and practice, 5th edition. Sudbury, Massachusetts: Jones and Barlett Publishers, 2000.

| Inicio |

	http://www.efdeportes.com/ · FreeFind
revista digital · Año 8 · N° 57 | Buenos Aires, Febrero 2003   © 1997-2003 Derechos reservados