Exercise and Disease Prevention


Kate Lovett

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Topics in this article:

Introduction

Disease Prevention Benefits of Exercise

Exercise and Heart Disease

Exercise and Cancer

Exercise and Non-Insulin Dependent Diabetes Mellitus

Exercise and Obesity

Exercise and the Immune System

Autoimmune Disease - Rheumatoid Arthritis

Type of Exercise - Frequency, Duration, and Intensity

Conclusion

References

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Introduction

Over the past century we have become increasingly sedentary due to the technical advancements of today's world. Ironically, while machines and improvements in transportation and communication have made our lives easier, studies show that the decline in our physical activity associated with these advancements plays a large role in the decline of our health.

A Surgeon General's report (Anonymous,1996) addresses the finding that continuous and consistent physical activity is proven to enhance longevity and the quality of life for people of all ages. Furthermore, the report notes that although it has been recognized for years that regular physical activity can lead to substantial health benefits, 60% of American adults are not regularly active, and 25% of the adult population are not active at all. Paffenbarger (1996) states that physical fitness and exercise can reduce the risk of diseases such as heart disease, non-insulin-dependent diabetes mellitus, some cancers, osteoarthritis and osteoporosis, and obesity. Studies also show that exercise can promote psychological well-being and reduce feelings of anxiety and depression (http://www.medgraph.com/aboutexercise.html).

The effects of exercise on health risk factors for a few days or weeks may not strike a person as significant, however, physical inactivity over a long period of time, say twenty years, adds up. For example, walking for one hour a day for five days burns about 2000 calories a week. Over a course of a year, a person performing this level of activity would burn about 96,000 calories (http;//www.ccn.cs.dal.ca/Health/CPRC/exercise.html) The negative effects of physical inactivity do add up and influence our health and our lives. Exercise and physical fitness are crucial to "maintaining health, performance capacity, and overall quality of life". (Haskell, 1996)


Disease Prevention Benefits of Exercise

While physical activity and exercise provide health benefits which positively effect a wide range of factors contributing to the quality of life, there are a few overarching areas of disease or health complications where regular exercise predominately reduces risk or aids in controlling disease.

1. Heart disease

2. Some forms of cancer

3. Non-insulin dependent diabetes mellitus

4. Obesity

5. Weakened Immune system

6. Autoimmune disease - Rheumatoid arthritis

Web Links on General Benefits of Exercise:

http://www.ccn.cs.dal.ca/Health/CPRC/exercise.html

http://www.vh.radiology.uiowa.edu/Providers/ClinGuide/PreventionPractice/ACouseling/56.htm


Exercise and Heart Disease

Cardiovascular disease is the leading cause of death in America. The American Heart Association has stated that the leading cause of heart disease is physical inactivity. (http://www.columbia.net/drfrist/exercise.html) The Surgeon General's report (Anonymous, 1996) states that "regular physical activity or cardiorespiratory fitness decreases the risk of cardiovascular disease mortality in general and of coronary heart disease (CHD) mortality in particular. Regular physical activity prevents or delays the development of high blood pressure in people with hypertension". Due to the complexity and the numerous possible causes to heart disease and failure, it is logical that physical activity can reduce that risk of heart disease by influencing different aggravating factors such as coronary artery flexibility and cholesterol level.

A Stanford University (Haskell, 1993) study on exercise and heart disease focused on whether or not running prevented heart disease by increasing the flexibility of the coronary arteries. Heart attacks are caused by inadequate blood flow to the heart. Atherosclerosis is the progressive narrowing of the three main coronary arteries which deliver blood to the heart. The arteries are typically 3 to 4 mm in diameter. In order to prevent problems in blood flow to the heart artheroscle http://www.dpalm2.med.uth.tmc.edu/ptnt/00000385.htm rosis must be prevented or an increase in the diameter of the arteries must occur. Nitroglycerine was given to both runners and nonrunners in attempt to expand the arteries to the point of "maximal pharmacologic dilation". The results showed that the arteries of the runners expanded twice as much as the nonrunners; proving that the coronary arteries of runners are more flexible than the coronary arteries of nonrunners.

Physical activity also aids in the prevention of heart disease by improving a person's cholesterol level. Research on physical activity and cholesterol show that exercise raises the level of "good" cholesterol, lowers the triglyceride level, improves the total cholesterol/HDL ratio, and slightly lowers the level of "bad" LDL cholesterol ("Shaping Up", 1993). The improved cholesterol status of the physically fit is largely due to the fact that overweight people often have an excess fat which increases unhealthy cholesterol status. "The average American male has an HDL (cholesterol) level of 45. A distance runner has a level of about 65. For every one to two point increase in your HDL level, there's a 2 to 4 percent reduction in your risk of heart disease." ("Shaping Up", 1993)

Like any muscle in the body, the heart muscle becomes stronger with regular exercise. With greater coronary artery flexibility, higher HDL cholesterol levels, and lower blood pressure the heart strengthens and is able to do the same amount of work at a lower heart rate.

Web Links on Heart Disease:

http://www.medgraph.com/

http://www.columbia.net/drfrist/exercise.html

http://www.dpalm2.med.uth.tmc.edu/ptnt/00000765.htm

http://www.dpalm2.med.uth.tmc.edu/ptnt/00000384.htm

http://www.dpalm2.med.uth.tmc.edu/ptnt/00000385.htm

http://www.dpalm2.med.uth.tmc.edu/ptnt/00000386.htm

http://www.injersey.com/Living/Health/heart-disease.html

http://www.cardio.com/articles/walking.htm

Exercise and Cancer:

Recent evidence supports that regular, moderate physical activity can prevent some forms of cancer. Exercise is linked to a decrease in the risk of colon cancer, breast tumors, and other malignancies. (Simon, 1992) The Surgeon General's (Anonymous, 1996) report on physical activity states that there is no association with physical activity and rectal cancer and that more data is needed to determine whether or not there is a relationship between physical activity and endometrial, ovarian, or testicular cancers. The report also states that the data associating exercise with a decrease in the risk of breast cancer is inconsistant. However, one study from the University of Southern California (http://www.cancer.med.upenn.edu/cancer_news/exercise_bc.html) states that "women who participate in four or more hours of physical activity per week during their reproductive years reduce their risk of breast cancer by 60 percent, compared to inactive women". Charles Mahan, State Health Officer, also pointed out that "exercise can be added to your routine for early detection--the best way to fight breast cancer". (http://www.state.fl.us/hrs_hsi/public_html/hpw/bratip.html). Although continued study and research in needed in this area, there is sufficient evidence that exercise can be used as a preventative measure for certain types and sites of cancer. (McNamee, 1996)

Web Links on Cancer:

http://www.injersey.com/Living/Health/Cancer/dietexercise.html

http://www.cancer.med.upenn.edu/cancer_news/exercise_bc.html

http://www.state.fl.us/hrs_hsi/public_html/bratip.html

Exercise and Non-Insulin Dependent Diabetes Mellitus

Physical fitness and exercise can aid in preventing the onset of non-insulin dependent diabetes mellitus as well as aid in the regulation of blood glucose for those already suffering from diabetes. The American Diabetes Association (http://www.injersey.com/Living/Health/Exercise/diabetes.html) states that "exercise promotes the entry of glucose into the cells, helping the body to use its food supply more efficiently and to lower blood suger levels". Exercise can be an effective way to prevent the onset of diabetes. Exercise can also be helpful for those who already have diabetes.

Ninety percent of all diabetes have type II diabetes or non-insulin dependent diabetes mellitus. (Henahan, 1996) In type II diabetes, a individual either produces insufficient amounts of insulin or produces sufficient or even excess insulin; but their cells are resistant to the insulin. For both categories of type II diabetics, it is difficult to maintain normal glucose levels. Regular exercising for individuals whose cells are resistant to insulin will aid in the regulation of glucose levels in the blood. Diabetics who take insulin shots can also exercise with caution so that they do not subject themselves to hypoglycemia. (http://envirolink.org/arrs/VRG/diabetes.html #goals)

Exercise also contributes to the prevention of cardiovascular disease which is a common problem and leading cause of death in diabetics. "More than 80% of people with diabetes die from some form of heart and blood vessel disease." (http://sln.fi.edu/bioscihealthy/diabetes.html)

Furthermore, exercise helps in preventing obesity which can lead to diabetes. Almost nine out of ten people with non-insulin dependent diabetes mellitus are overweight. (http://aztec.asc.edu/medical/azse/exer.html) "Diabetics have higher than normal blood fat levels, creating a greater risk for heart disease, but regular exercise also has a positive effect on reducing cholesterol levels and weight." (http://www.injersey.com/Living/Health/Exercise/diabetes.html) Extreme caution and doctor consultation is advised for diabetic exercisers because of the importance of balancing food, exercise, and insulin levels.

Web Links on Diabetes:

http://www.lilly.com/diabetes/managing/exercise.html/?yes

http://www.columbia.net/consumer/datafile/diab6.html

http://www.aztec.asu.edu/medical/azse/exer.html

http://www.injersey.com/Living/Health/Exercise/diabetes.html

http://www.sln.fi.edu/bioscihealthy/diabetes.html

http://www.envirolink.org/arrs/VRG/diabetes.html#goals

Exercise and Obesity

As mentioned previously in the heart disease and diabetes sections, obesity alone, can lead to further complications of an individuals physical health. "Among those who are moderately obese, that is, 150 to 200 percent overweight, moderate weight loss in an obese person can reduce several chronic disease risk factors by 20% to 75%." (Murray, 1994) Obesity places individuals at greater risk for heart disease, cancer, stroke, diabetes and hardening of the arteries. Inactivity results in inefficient use of calorie intake toward energy usage. Emphasis needs to be placed on maximizing fat loss and minimizing lean tissue loss. Specifically, weight loss in an obese individual is ideal when 75% of weight loss is body fat. (Murray, 1994)

It is important that the individual set realistic goals with realistic rates of loss and healthy diet composition. The Yo-Yo effect of losing weight and gaining weight, then losing it again, and then gaining it again presents stress on the body and can cause further complications.(Murray, 1994)

Web Links on Obesity:

http://www.medgraph.com/about exercise.html

http://www.lilly.com/diabetes/managing/exercise.html/?Yes


Exercise and the Immune System

Regular, moderate exercise can be beneficial in fighting off the common cold. There has been relatively little research up until this last decade on how exercise effects the immune system. Up until recently people only noted that marathon runners commonly caught colds after races. Nobody investigated how everyday, moderate exercise affects an individual's ability in staying well. It turns out that the marathon runners who get sick after running have experienced over-training. Their muscle fibers break down due to the extreme exercise and the immune system releases stress hormones in attempt to repair the damage. Evidence shows that excess stress hormones negatively affect the body's immune system's ability to fight of colds. (Shute, 1996)

Research today shows that exercizing helps to increase the number of white blood cells which are central to the immune system's ability to ward off invading organisms. While exercise only increases the white blood cell count temporarily, daily physical activity can only enhance the body's ability to fight off everyday colds. (Shute, 1996)

A study (Shute, 1996) was performed on a group of women age 60 to 80 who were placed into two groups of exercisers and non-exercisers. Those who exercised (walked 37 minutes a day, five days a week, for 13 weeks) were less likely to get sick than the non-exercisers. Specifically, 50% of the non-exercisers caught colds while only 21% of the exercisers caught colds.

While it has not yet been determined at what specific point exercising leads to an excess of stress hormones, it is clear that everyday, moderate walking is beneficial to the immune system. Furthermore, it not only prevents getting sick, but in some cases may help people who are already sick with chronic illnesses. AIDS patients found that they could increase their CD4 cell count by exercising. Anxiety and depression, common among AIDS patients, can also be relieved by exercise. Many people believe that this type of relief will benefit the immune system. (Murray,1996)

Autoimmune Disease - Rheumatoid Arthritis

Physical Activity is important and necessary for "maintaining normal muscle strength, joint structure, and joint function". (Anonymous, 1996) There is no definite link between physical activity and joint damage and osteoarthritis (inflammation of the joints), so long as the exerciser stay within the range of exercise recommended for physical health. (Anonymous, 1996) Rheumatoid Arthritis (RA) is another disease which affect the joints and is also an autoimmune disease. RA involves chronic, symmetric and erosive synovitis of peripheral joints. "Although bed rest is considered therapy for many RA patients, it is only recommended until inflammation subsides. After that, the acute inflammatory response becomes more chronic from downward spiraling of physical conditioning." (Welch,et.al, 1995) Individuals with "RA patients die 10 to 15 years earlier than nonafflicted individuals. But, the research shows a predictably higher mortality rate in RA patients who are inactive." (Welch,et. al, 1995) In summary, exercise and physical activity is an important part of the treatment of rheumatism. It can help to promote a better and longer life. It is important, however, that individual needs are assessed before developing an exercise program. RA patients are divided into four classifications based on their physical abilities and handicaps. Different types of exercise should be implemented according to the level of the patient.


Type of Exercise - Frequency, Duration, and Intensity

"Physical activity refers to any body movement produced by the skeletal muscles and resulting in a substantial increase over the resting energy expenditure." (Malina, 1996) Exercise benefits the individual throughout the entire lifespan and it is never too late to start. As a child, physical activity is crucial to the growth and strengthening of bones and muscles. As an adult, whether 30 years old or 75 years old, exercise is crucial to health maintenance and quality of life. While different individuals have unique needs and specifications for exercise programs, there is a common consensus concerning the average "best" type of exercise.(Pekka, 1995)

1. Frequency and duration:

a) 3 days a week for a total of 60 minutes a day

b) 6 days a week for a total of 30 minutes a day

2. Intensity

a) moderate

b) aerobic exercise - cycling, swimming, jogging, walking, calisthenics, and light-weight training

It is important that the exercise a person chooses is appropriate for their present physical ability. There are three components to exercise - exercise modality, exercise duration, and exercise intensity. (http://www.columbia.net/dfrist/exercise.html) These components need to be balanced so that they meet the needs and the abilities of the individual. If you have been a generally sedentary person up until this point it is recommended that you consult your physician before beginning an exercise program.


Conclusion:

In summary, physical activity and exercise is a crucial and critical component to healthy living. It is never too late to start exercising, so long as the type of physical activity engaged in is appropriate to one's physical ability. Start out slowly and safely and build up to the recommended frequency, duration, and time.

References:

Anonymous (19196). Summary of the Surgeon General's Report Addressing Physical Activity and Health. Nutritional Reviews, 54(9), 280-289.

Haskell, W. (1996). Physical Activity, Sport, and Health: Toward the Next Century. Research Quarterly for Exercise and Sport, 67(3), 37-51..

Haskell, W. (1993). The Heart of the Matter. Runner's World, 28(9), 56-58.

Henahan, S. (1996). Data Growing on Diabetes Prevention, Insulin Resistance. Drug Topics, 140(15), 66-68.

Malina, R. (1996). Tracking of Physical Activity and Physical Fitness Across the Lifespan. Research Quarterly for Exercise and Sport, 67(3), 48-61.

McNamee, D. (1996). A Change in Lifestyle May Prevent Cancer. The Lancet, 348, 1436.

Murray, F. (1994). Weight Management: The Key to Disease Prevention. Better Nutrition for Today's Living, 56(7), 44.

Paffenbarger, R. (1996). Physical Activity and Fitness for Health and Longevity. Research Quarterly for Exercise and Sports, 67(3), 11-30.

Pekka,O. (1995). Descriptive Epidemiology of Health-Related Physical Activity and Fitness. Research Quarterly for Exercise and Sports, 66(4), 303-315.

Shute, N. (1996, December 16). Exercise an Ally in Cold/Flu Battle. Denver Post, pF1.

Simon, H. (1992). Can You Run Away from Cancer? Havard Health Letter, 17(5), 5

Shaping Up. (1993 May). The Saturday Evening Post; Indianapolis, 24.

Welch, G., &Clark, J. (1995). The Other Arthritis. American Fitness, 13(5), 24-28.

 

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