Wednesday, December 19, 2007

Physical activity and health

The evidence linking inactive living with a range of physical and mental diseases and disorders is now accepted by leading authorities world wide. People need to move more and more often. Unfortunately, the majority of the population, particularly those most likely to benefit, such as the middle aged and elderly, are unlikely to become more active. Individuals should take personal responsibility and establish lifestyles that involve healthier eating and more daily physical activity.
Physical activity refers to all energy expended by movement, including everyday activities, such as walking, cycling, climbing stairs, housework, and shopping, occurring as an incidental part of our routines. Exercise, on the other hand, is a planned and purposeful attempt to improve fitness and health that might include activities such as brisk walking, cycling, aerobic dance, and perhaps active hobbies such as gardening and competitive sports such as distance running, or lifting weight
In the past 20 years or so extensive evidence has established that inactivity causes illness and premature death. Those who maintain a reasonable amount of activity, particularly across the middle and later years, are twice as likely to avoid early death and serious illness, leading to the recognition of inactivity as the fourth primary risk factor for heart disease. Further good news suggests that the process of becoming fitter produces distinct benefits and it appears that it is never too late to make some changes and experience these positive outcomes.
Physical activity has both preventive and therapeutic effects.
Coronary heart disease and stroke
Coronary heart disease remains the leading cause of death in developed countries. Maintaining an active lifestyle, and a moderately high level of aerobic fitness, halves the chances of either dying from or contracting serious heart disease. There is a clear
dose response relationship, with the change from sedentary to moderately active producing greatest health benefits. Regular walking produces a reduction in CHD events, cycling to work, active commuting to work, and four hours of recreational activity per week or at least 800 kcals of leisure time activity per week are all associated with reduced risk.
The preventive and therapeutic effects of physical activity on stroke are less clear with studies showing inconsistent results.
Obesity appears to be a direct result of environmental conditions that involve easy access to motorized transport, labor-saving devices, home screen entertainment, and cheap, high dens
ity food.. The evidence that reduced physical activity has been a determinant of this increase is

stronger than the evidence for increased energy intake
There are several prospective studies that indicate the benefits of an active and fit
lifestyle for the prevention of obesity.. Furthermore, those who maintain exercise are much
more likely to sustain any weight loss long term than those who rely on dietary management alone.
Perhaps the greatest benefit of physical activity for the obese is its impact on health risk profile. Reviewed observational studies concluded that obese people who managed to keep active and fit reduced their risk of heart disease and diabetes relative to non-obese levels. This would suggest that it is not unhealthy to be fat as long as you remain fit. It also puts into question whether obesity is more hazardous than inactivity.
Adult onset diabetes
There is strong evidence to show that inactivity may be a causal factor on the incidence of Type 2 diabetes. Prospective studies indicate a strong negative relationship between activity and contraction of diabetes, with risk reductions of 33-5
0% recorded for active groups .Walking, cycling and active hobbies such as gardening are associated with lower risk but it is likely that the greatest gains are made with moderate to vigorous activity. The strong relationship is plausible as the muscle is a critical site for glucose metabolism.

Exercise has been shown to delay or possibly prevent progression of glucose intolerance to the diagnosis of diabetes. Exercise also has benefits for those who are already diagnosed with diabetes. A small number of well designed studies have also shown that an activity program of walking or cycling, carried out three times a week for 30-40 minutes, is able to produce small but significant improvements in glycemic control in diabetics.

Involvement in occupational or leisure time physical activity carries a reduced risk of mortality from cancer a leading cause of ill health and death. Moderate to vigorous activity appears to be most beneficial. The strongest protective effect is for colon or colorectal cancers producing a 40-50% risk reduction.
Physical activity also helps prevent lung cancer with a 40% risk reduction evident after control for smoking and other lifestyle factors. Similarly there are benefits for breast cancer but not prostate or testicular cancer.
There has been less attention paid to the impact of exercise in the treatment or management of cancer. Although there is as yet insufficient evidence to suggest that progress of the disease can be slowed by exercise, it does appear to have benefits for life quality including improved psychological well-being and reductions in fatigue and nausea.
Bone and muscle health
Diseases such as low back pain, osteo-arthritis and osteoporosis are a major cause of human suffering, reduced life quality and lost work productivity. Exercise training produces stronger muscles, tendons and ligaments and thicker more dense bone which improves functional capacity and allows greater independent living in older people. Physical activity programs designed to improve muscular strength also helps older adults to maintain balance and a reduction in falls. It can be effective in preventing low back pain and also reduces reoccurrence of back problems. Physical activity has not been shown to prevent osteo-arthritis but walking programs have indicated important beneficial effects. Exercise can reduce pain, stiffness and disability and improve strength, mobility and overall ratings of life quality.
Exercise training involving, weight bearing moderate to vigorous activity, can increase bone mineral density and bone size in adolescents, help maintain it in adults and slow decline in older age. This in turn prevents or delays the onset of osteoporosis but cannot reverse osteoporosis once it has developed. The effect is specific to those bones loaded by the exercise.
Mental well-being
The case for physical activity and health has largely been made on the evidence for its prevention of diseases such as CHD, cancer, obesity and diabetes. The World Health Organization has estimated that mental illness, largely in the form of depression and anxiety, will be the leading cause of disability and a major cause of loss of life by the year 2020. In addition to increased incidence of serious mental illness there is concern for the increasing numbers who suffer chronic or recurrent mild to moderate symptoms of depression. Several well designed studies have now shown that physical activity can reduce clinical depression.
Exercise can be as effective as traditional treatment such as psychotherapy as it can offer a cheap alternative. Physical activity also improves psychological well-being in those who are not suffering from serious mental disorders. Several hundreds of studies have documented improvements in subjective well-being, mood and emotions, and self-perceptions such as body image, physical self-worth and self-esteem. Furthermore, both single bouts of activity and exercise training reduce anxiety stresses, and also improve quality and length of sleep.
Physical activity is particularly helpful for older people as it reduces risk of dementia and Alzheimer disease and improves executive aspects of mental functioning such as planning, short-term memory and decision making. Clearly, physical activity has tremendous potential to improve quality of life throughout the lifespan.
Risks of physical activity
The risk of sudden cardiac death is elevated by five times during vigorous exercise for fit individuals and 56 times for unfit individuals. Any risks accompanying exercise are far outweighed by the benefits and the reductions in disease risk that fitness brings. There is also an increased risk of injury, particularly to feet, ankles and knees, while taking part in exercise or vigorous sports.
Physical activity recommendations
When people become more active, they reduce their risk of early death from heart disease, some cancers and diabetes. They manage their weight better, increase their tolerance for physical work, and they improve their muscle and bone health. They are also likely to improve their psychological well-being and life quality. And, physical activity has the potential to add years to life.
For many years, exercise and health promoters adopted training guidelines for the improvement of cardiovascular fitness involving vigorous exercise using large muscle groups in continuous work for a minimum of 20 minutes at an intensity equivalent to 60-80% of maximum heart rate. Unfortunately, after almost two decades of promoting this there has been little increase in the people exercising at this level. It seems that it is too rigorous for most people. The evidence also indicates that it is not essential to work so hard in order to appreciate health gains. There is a curve of diminishing returns regarding physical activity level and health benefit with the greatest gains to be made by individuals changing from the sedentary to moderately active category.
The physical activity promotion message is now to take regular activity of a moderate intensity, equivalent to brisk walking, is thought to be achievable by a much larger percentage of the population as it can be reasonably incorporated into daily routines and is less physically demanding. Current recommendations emphasize brisk walking on most or all of the days of the week for 30 minutes at a time, even when the same amount is taken in two or three shorter bouts.
This is essentially a general recommendation. Different types and intensities of activity will improve different elements of health and fitness. For example, a gentle stroll at lunchtime, although not sufficiently intensive to create an improvement in circulatory fitness, may provide a healthy break from work, enhance mood and reduce stress, while also contributing to weight management. The accumulation of small but regular periods of movement during work or leisure can also make a significant difference to energy balance and weight control in the long term. Simply standing for one hour instead of sitting watching TV each day, for example, will expend the equivalent of 1 - 2 kgs of fat per year. A daily 20-minute brisk walk will make a difference of 5 kgs per year, and for most people there will be improvements in cardiovascular fitness and potential for other physical and mental health benefits.

There may also be a benefit in reducing the amount of time spent in sedentary persuits such as watching television. To provide maximum benefits for all areas of the body, a range of specific strengthening and stretching exercises will also be needed. This is particularly important for older people.

  • Involve large muscle groups

  • Impose more than a customary load

  • Require a minimum total of 700 kcal/week

  • Be performed regularly and if possible daily

In practice, sustained rhythmic exercise, such as brisk walking for 20-30 minutes would fulfill this requirement in most adults.

For further maximum health benefits, activities should:

  • Include some periods of vigorous activity

  • Include a variety of activities

  • Exercise most of the body’s muscles, including trunk and upper body

  • Expend up to 2000 kcals/week

  • Be maintained throughout life

The Japanese work ethic includes some calisthenics (mild physical exercise) during the workday. They believe the workout helps promote productivity. Some American companies are studying the validity of the relationship, but a few firms are not exactly convinced. This sign was posted on a company bulletin board: “This firm requires no physical fitness program. Everyone gets enough exercise jumping to conclusions, flying off the handle, running down the boss, flogging dead horses, knifing friends in the back, dodging responsibility, and pushing their luck.”
Energy Used in Activities – (Use this guide to obtain an approximation of the calories you burn daily compared to the calories you ingest. If input consistently exceeds output, you need to burn more calories.)
Calories burned by a 130-lb person performing the following activities for an hour:

Around the house –
Mopping floor – 224
Cleaning windows – 216
Washing dishes – 168

Cooking – 164
Doing laundry – 156
Dusting – 148
Making a bed – 144
Ironing – 116
Talking on phone – 88
Sleeping – 72
Pleasure –
Walking dog – 284
Pushing baby stroller – 228
Gardening – 200
Baking cookies – 128
Writing a love letter – 104
Holding hands – 80
Reading a book – 76
Watching TV – 76
At Work
Strolling – 124
Writing at desk – 104
Bowling – 250
Golf – 230
Swimming, ¼ mph – 270
Volleyball – 320
Roller skating – 320
Bicycling 5 ½ mph – 190
Mowing lawn – 396
Shoveling dirt – 372
Painting outside – 272
Weeding – 252
Raking leaves – 192
Painting inside – 120
Running – 420
Climbing hill – 360
Walking moderate – 180
Walking fast – 270
Driving car – 160
Standing – 100

Sharpening pencil – 104
Writing at desk – 104
Typing (electric) – 96
Attending a meeting – 72
Diet and Exercise Prolongs Life
Very recently two new studies based on a large U.S. diet and health survey demonstrate the benefits of exercise and diet in reducing health risks and prolonging life.
The first shows people who follow a Mediterranean-style diet rich in vegetables, fruits, whole grains, and healthy oils, such as those found in fish, olives, and nuts, were less likely to die of cancer, heart disease, or any other cause over a five-year period.
The second shows people who engaged in moderate exercise like walking for at least 30 minutes a day most days of the week, as recommended by national guidelines, were 27% less likely to die during the study than non-exercisers. Even a smaller amount of exercise produced benefits in reducing the risk of death over the short-term, but those healthy benefits increased with more frequent and vigorous exercise.
The studies, published in the Archives of Internal Medicine, were both based on data collected from the National Institutes of Health-AARP Diet and Health Study involving 566,407 AARP members aged 50 to 71 in six U.S. states who filled out diet and exercise questionnaires between 1995 and 1996.
In the first study, researchers looked at the effect of the Mediterranean diet on the risk of death over five years. This diet has gained in popularity in recent years thanks to research that shows countries that follow the diet, rich in fruit and vegetables and low in saturated fat, have lower rates of heart disease and other health problems. This study confirmed those healthy effects and showed men and women who followed a Mediterranean diet were 20% less likely to die from any cause during the study.
In the second study, researchers compared the risk of dying during the study to rates of exercise. The results showed that people who were moderately active for at least 30 minutes a day, most days of the week were 27% less likely to die than those that were inactive. The health benefits of exercise increased with more vigorous activity. Those who engaged in vigorous activity had a 32% lower risk of death during the study; a level of physical activity that was less than recommended was linked to a 19% lower death risk.
One final benefit in becoming active – you save on electricity bills when the TV is switched off while doing the chores.

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