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PODSTAWY 06/2006

Physical activity

1. Introduction

In the battle for weight control and general good health, a lot of attention has been paid to the type and amount of the food and drink we consume. Less attention has been given to the amount of energy we use up by being physically active. Yet the two are closely linked. Unlike our ancestors, we do not generally need to exert a great deal of energy to find food. Advances in technology through motorised transport, automation, and labour-saving equipment, mean that there are fewer opportunities to exert energy for most people. It has been shown that around 70% of populations in westernised countries are not sufficiently active for optimal health and weight maintenance.

2. What do we mean by "physical activity"?

Physical activity, exercise, fitness - all of these terms are routinely used to refer to being physically active. Yet, in scientific terms, they all mean slightly different things. The most commonly used terms are defined in the table below.

 DEFINITIONS RELATED TO PHYSICAL ACTIVITY
Physical activity All bodily movements that result in energy expenditure. This includes daily routine activities such as household jobs, shopping, work.
Exercise Planned and structured repetitive movements designed specifically to improve fitness and health.
Sport Physical activity that involves structured competitive situations governed by rules. In many European countries, the term sport is used to include all exercise and leisure time physical activity.
Physical fitness A set of attributes such as stamina, mobility, and strength that relate to ability to perform physical activity.

Physical activity refers to all energy expended by movement. The major contributors are everyday activities that involve moving the body around, such as walking, cycling, climbing stairs, housework, and shopping, with much of it occurring as an incidental part of our routines. Exercise, on the other hand, is a planned and purposeful attempt, at least in part, to improve fitness and health. It might include activities such as brisk walking, cycling, aerobic dance, and perhaps active hobbies such as gardening and competitive sports.

Fitness is largely the result of our levels of physical activity, however genetic factors also play a role, with some lucky individuals having a natural capacity and physique to excel at certain activities. This becomes more noticeable in competitive sports, such as distance running or weight lifting, where the best performers often have a genetically superior body that is in peak condition through vigorous training. The important point to remember though is that evidence to date shows it is regular participation in physical activity (rather than any inherited component of fitness) that is linked to good health. This means that everyone, whether they are naturally athletic or not, can benefit from being more active!

3. What are the benefits of physical activity?

The benefits of being physically active are numerous and range from a reduced risk of certain diseases and conditions to improved mental health.

3.1 Coronary heart disease and stroke

Coronary heart disease (CHD) is the leading cause of death in Europe. Maintaining an active lifestyle and at least a moderately high level of aerobic fitness can halve the chances of either dying from or contracting serious heart disease. The benefits of exercise on heart health can be felt at even moderate levels of activity with the greatest benefits being seen when sedentary individuals become moderately active. Regular walking, cycling or four hours of recreational activity per week are all associated with a reduced risk of heart disease. Physical activity has also been shown to aid recovery from heart disease with exercise-based cardiac rehabilitation programmes effective in reducing further deaths. The effects of physical activity on stroke are less clear with studies showing inconsistent findings.

3.2 Obesity and overweight

Weight maintenance is the enery intake and energy expenditure. When intake is higher than expenditure over a certain period of time overweight and obesity develop. It is thought that obesity is a direct result of changes in our environment including the increased availability of labour saving devices, motorised transport, home screen entertainment and easier access to calorie rich foods at a lower cost. The incidence of obesity has trebled in the last 20 years and in European countries 10-20% of men and 10-25% of women are now obese (Body mass index >30). Evidence is mounting that a reduction in levels of physical activity is a major factor in this trend.

There are several studies that show the benefits of an active and fit lifestyle for the prevention of obesity. In particular, activity appears to help protect against the weight gain typical of middle age.

In those who are already overweight or obese, exercise can assist with weight loss when combined with a low-energy (low calorie) diet and improves body composition by preserving muscle tissue and increasing fat loss. Physical activity is also effective in reducing abdominal fatness or "apple shape" (where fat deposits accumulate around the stomach and chest area), the fat distribution associated with an increased risk of diabetes and heart disease. Furthermore, those who maintain exercise are more likely to sustain any weight loss over the long term.

Perhaps the greatest benefit of physical activity for obese individuals is its effect on their health risk profile. It has been shown that obese people who manage to keep active and fit reduce their risk of heart disease and diabetes to levels consistent with those of non-obese individuals. This would suggest that it is not unhealthy to be fat as long as you are fit. 

3.3 Adult onset diabetes

The incidence of type 2 diabetes has risen rapidly. This is often attributed to a rise in obesity, however, there is strong evidence to show that inactivity is also a risk factor. Studies indicate that more active individuals have a 30-50% lower risk of developing diabetes than their sedentary peers. Exercise has been shown to delay or possibly prevent glucose intolerance turning into diabetes and also has benefits for those who are already diagnosed with diabetes. A small number of well designed studies have shown that exercise such as walking or cycling, carried out three times a week for 30-40 minutes, is able to produce small but significant improvements in glycaemic (blood sugar) control in diabetics.

3.4 Cancer

Being physically active appears to reduce the risk of certain cancers, with moderate to vigorous activity offering the greatest protection. For example, being physically active reduces the risk of developing colon or rectal cancers by 40-50%. Physical activity may also have an impact on some other cancers but evidence is still being gathered.

3.5 Muscle and bone health

Disorders and diseases affecting the muscles and bones, (such as osteoarthritis, low back pain and osteoporosis), can benefit from regular exercise. Exercise training produces stronger muscles, tendons and ligaments and thicker, more dense bone. Physical activity programmes designed to improve muscle strength have been reported to help older adults to maintain balance , which may result in a reduction in falls.

Exercise can also be effective in preventing low back pain and reduces reoccurrence of back problems. It is not clear, however, which type of exercise works best on back pain. Physical activity has not been shown to help prevent osteoarthritis but walking programmes have been shown to help reduce pain, stiffness and disability and improve strength, mobility and overall ratings of life quality.

Exercise training (involving weight bearing in addition to 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 can help to prevent or delay the onset of osteoporosis but cannot reverse osteoporosis once it has developed.

3.6 Mental well-being

Several well-designed studies have shown that physical activity can reduce clinical depression and can be as effective as traditional treatments such as psychotherapy. Regular physical activity over several years may also reduce the risk of depression recurring.

Physical activity has also been shown to improve psychological well being in people who are not suffering from mental disorders. Numerous 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 and improve reaction to stress and the quality and length of sleep. Exercise has also been shown to improve aspects of mental functioning such as planning, short-term memory and decision making.

Physical activity appears to be particularly beneficial for older people by reducing the risk of dementia and Alzheimer disease.

4. What are the costs of inactivity?

The human body is designed for movement and a sedentary lifestyle has been linked to illness and premature death. A review of 44 studies found that individuals, who maintain a reasonable amount of activity, particularly in their middle and later years of life, are twice as likely as their sedentary counterparts to avoid early death and serious illness. This level of health benefit is similar to that gained by avoiding smoking, and inactivity is now recognised as one of the risk factors for heart disease.

How does this translate into economic costs? Although disease and early death cause suffering to victims and their friends and family, there are high economic costs in terms of sickness absence from work and health care. Most of the studies have been conducted in the USA where it has been estimated that 18% of heart disease cases (at a cost of $24 billion -1995 $ value-) and 22% of colon cancer cases (at a cost of $2 billion) in the population may be caused by inactivity. It is now known that the average medical costs for active people are 30% lower than those for inactive people.

In Britain, where obesity rate is the highest in Europe (around 20% of the population, this being at least partially, a result of inactivity) the cost of obesity, has been estimated to be £500 million, causing 18 million days of sickness absence per year.

5. What are the risks associated with physical activity?

No action is without risk and exercise is no exception. For example, the risk of sudden cardiac death increases by a factor of 5 during vigorous exercise for fit individuals and by a factor of 56 for unfit individuals. There is also an increased risk of injury, particularly to feet, ankles and knees, while taking part in exercise or vigorous sports. Finally, much press attention has focussed on "exercise addiction", whereby people become 'hooked' on exercise to the detriment of other aspects of life such as work and social relationships. Although a syndrome of exercise dependence has been identified, it is extremely rare and more likely to accompany other mental problems such anorexia nervosa, excessive neuroticism and obsessive-compulsive disorders.

6. How much physical activity do we need?

For many years, exercise and health promoters adopted training guidelines for the improvement of cardiovascular fitness that involved quite vigorous exercise using large muscle groups in continuous work for a minimum of 20 minutes at a vigorous intensity (equivalent to 60-80% of maximum heart rate). Unfortunately, this level of exercise proved too difficult to achieve for the majority of people, with most remaining inactive.

The most recent recommendations from the USA and the UK are for regular bouts of activity at moderate levels of intensity. Moderate intensity physical activity, 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. A daily 20-minute brisk walk will induce improvements in cardiovascular fitness and other physical and mental health benefits. Current recommendations emphasise brisk walking on most or all of the days of the week for 30 minutes at a time. Evidence suggests that the same amount of exercise taken in two or three shorter bouts can be almost as effective and may also be more manageable on a daily basis.

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. For those who dislike or are unable to do planned exercise, avoiding or reducing the time spent in sedentary pursuits such as watching television may be just as useful. To provide maximum benefit for all areas of the body, a range of specific strengthening and stretching exercises is also needed. This is particularly important for older people.

The moderate exercise message does not overrule the extra benefits provided by more vigorous activity, particularly in terms of improving heart health and glucose metabolism.

The recommendations from the Quebec Consensus Statement on Physical Activity, Health and Well-Being provide useful physical activity guidelines.

SUMMARY OF RECOMMENDATIONS FROM THE QUEBEC CONSENSUS STATEMENT ON PHYSICAL ACTIVITY, HEALTH AND WELL-BEING (1995)
 Activities should:
  • 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 fulfil 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

7. Conclusions

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 improve their muscle and bone health. They are also likely to improve their psychological well-being and life quality. Not only does physical activity have the potential to add years to life, but the evidence is also accumulating that it can add life to years.

The promotion of physical activity requires concerted effort from several agencies to help individuals reduce their sedentary time and increase their physical activity, and to change the environment to encourage people to be more active. National, regional and local governments need to work with planners of transport and building, schools, work places, and health authorities to encourage more activities such as walking, cycling, sport and active leisure. At the same time individuals share the responsability to establish lifestyles that include daily physical activity.

Bibliography

  • Andersen, L.B., Schnor, P., Schroll, M., & Hein, H.O. (2000). All-cause mortality associated with physical activity during leisure time, work, sports, and cycling to work. Archives of Internal Medicine, 160, 1621-1628.
  • Biddle, S.J.H., Fox, K.R., & Boutcher, S.H. (2000). Physical activity and psychological well-being. London: Routledge.
  • Bijnen, F.C., Feskens, E.J., Caspersen, C.J., Nagelkerke, N., Mosterd, W.L., & Kromhout, D. (1999). Baseline and previous physical activity in relation to mortality in elderly men: the Zutphen Elderly Study. American Journal of Epidemiology, 150, 1289-1296.
  • Medicine and Science in Sports and Exercise (1999), Nov; 31 (11 Supplement).
  • Blair, S.N. & Hardman, A. (1995). Special issue: Physical activity, health and well-being - an international scientific consensus conference. Research Quarterly for Exercise and Sport, 66 (4).
  • Fogelholm, M., Kukkonen, M., & Harjula, K. (2000). Does physical activity prevent weight gain: A systematic review. Obesity Reviews, 1, 95-111.
  • Lawlor, D. A., & Hopker, S. W. (2001). The effectiveness of exercise as an intervention in the management of depression: systematic review and meta-regression analysis of randomised controlled trials. British Medical Journal, 322, 1-8.
  • Prentice, A.M., Jebb, S.A. (1995). Obesity in Britain: Gluttony or Sloth. British Medical Journal, 311, 437-439.
  • Sports Council and Health Education Authority. (1992). Allied Dunbar National Fitness Survey. London: Sports Council/HEA.
  • US Department of Health and Human Services (PHS). (1996). Physical activity and health. A report of the Surgeon General (Executive Summary). Pittsburgh, PA: Superintendent of Documents.
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