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clinmed/2004060001v1 (June 29, 2004)
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Title:
Increasing physical activity: an exercise in evidence based practice?



AUTHORS:

Oliver Morgan1

1. Public Health Specialist Trainee, Kensington and Chelsea Primary Care Trust, London, UK


SUMMARY

There is considerable evidence to show that physical activity can lower blood pressure, reduce the risk of coronary heart disease and stroke, help to achieve weight loss and manage diabetes, reduce the risk of developing some types of cancer and degenerative bone disease as well as relieving depression. Epidemiological studies suggest that in order to maintain good health, we should partake in at least 30 minutes of moderate physical activity on five or more days of the week. However about 70% of the population in England is not active at this level. Three types of community-based intervention to increase physical activity have been studied: educational, behavioural and social and environmental. However, evidence of effectiveness for these interventions is weak. This presents a difficult dilemma for public health organisations – we know that physical activity is good for health, but we don’t know how to increase it in the community.


INTRODUCTION
We all intuitively know that exercise is important for maintaining good health. While most people would correctly identify its role in coronary heart disease, strong evidence exits to show that being physically active also has many other health benefits.

While important, this evidence alone is of limited use for public health practitioners who want to develop physical activity programmes within their Primary Care Trust. For this they also need to consider how much exercise is required for good health and whether their population is active at these levels. Furthermore, evidence is needed to inform which community-based programmes are likely to be most effective. Here we briefly consider the evidence behind each of these questions and draw conclusions for public health practitioners interested in promoting physical activity.

HEALTH AND PHYSICAL ACTIVITY
In the US, it is estimated that as much as 12% of all deaths are attributable to lack of physical exercise. Data from the UK suggest that physical inactivity is responsible for over a third of coronary heart disease (CHD) mortality, greater than smoking and diet and almost as much as high blood cholesterol (Table 1). Being physically inactivity also contributes to weight gain and the development of type 2 diabetes as well as musculo-skelteal problems such as osteoporosis and degenerative conditions such as osteoarthritis. Furthermore, some studies suggest that sedentary people may have 1.2 to 3.6 greater risk of colon cancer compared to active people. Physical health is also associated with a person’s psychological well-being and people who are physically active report greater self-esteem, enhanced mood and confidence in their physical functioning with possible beneficial effects for relieving symptoms of depression and anxiety. Adverse effects of physical activity are mostly due to musculosketetal injuries, metabolic abnormalities (particularly hypoglycaemia in diabetics), accidents associated with outdoor activities such as cycling and asthma attacks in susceptible individuals. Two studies of Acute Myocardial Infarction (AMI) in people taking exercise suggested that the absolute risk is low (0.3 to 2.7 events per 10,000 person hours of exercise).



APPROPRIATE LEVELS OF PHYSICAL ACTIVITY
Earlier guidelines for physical activity, developed by the American College of Sports Medicine (ACSM), recommended 20-30 minutes of continuous exercise at a vigorous or high-intensity level on three or more days of the week. However these guidelines were designed to increase cardiorespiratory and muscular fitness and were considered inappropriate for the majority of the inactive population who are unlikely to participate in high-intensity gym or sports activities. Subsequently, a meta-analysis by Berlin and Colditz showed a no threshold relationship between exercise intensity and CHD and that even moderate-intensity activities (such as walking and cycling) could produce clinically significant health benefits. Furthermore, (weaker) epidemiological evidence suggested that rather than taking continuous exercise on one occasion, health benefits could be achieved by accumulating physical activity over the course of a day. This evidence formed the basis for the revised set of guidelines adopted by the Department of Health in 1995; individuals should partake in at least 30 minutes of moderate physical activity accumulated on five or more occasions per week.

POPULATION LEVELS OF PHYSICAL ACTIVITY
Several surveys have assessed levels of physical activity in England. The first large survey of physical activity was the Allied Dunbar National Fitness Survey in 1989. Since then the Health Survey for England (HSE) has included physical fitness several times (1991-1994, 1998, 1999). A third source of physical activity information is available from the Health Education Monitoring Survey (HEMS) (1995, 1996, 1998), which was commissioned by the Health Education Authority to measure a range of health promotion indicators. All three surveys measured physical activity as a component of the time spent being active, intensity and frequency. This included occupational activity, activity at home, walking and sports & exercise. However, the HEMS survey included a wider range of occupations as contributing to physical activity levels, resulting in slightly lower estimates for sedentary people.

The surveys show that only about 33%-41% of men and 20%-30% of women are active at recommended levels (Figure 1). Between 24%-35% of men and 26%-43% of women were classed as sedentary, participating in less than 30 minutes of physical activity on at least one day a week. Physical activity varies considerably by age, with levels of physical activity decreasing rapidly amongst the older age groups. In the 1998 HEMS survey, almost 45% of men and 51% of women 65-74 years were sedentary. This proportion increased to 64% of men and 72% of women over 75 years.

STRATEGIES TO INCREASE PHYSICAL ACTIVITY IN THE COMMUNITY
There have been many different interventions at the community level to encourage people to become more physically active. A review of the published literature by Kahn et al (2002) defined three types of community intervention to increase physical activity: Informational approaches, behavioural and social approaches and environmental and policy approaches (Table 2). Informational approaches aim to increase physical activity by providing information that will motivate people to change their behaviour. These approaches often complement the medical model of disease management, for instance by supporting the management of cardiovascular disease. Behavioural and social approaches are often based on health promotion models in order to change individual and group behaviour. These interventions appear to be more effective in younger children and in a family setting than when provided within a school setting. Finally, environmental and policy approaches intend to increase opportunities for physical activity by providing gym facilities or activities in which to participate. Exercise referral schemes, which are becoming increasingly popular in the UK, are an example of this type of intervention.

Although there is evidence that some of these interventions may be effective at increasing levels of physical activity, it is not clear whether these gains are maintained in the longer term or result in better health outcomes. Unfortunately, many of these studies report interventions that are too intensive to be reproduced in a service setting and few consider their cost effectiveness. Disappointingly, physical activity interventions appear to be least effective amongst the least active individuals. However, increasing physical activity in this group would provide the greatest public health gain.



DISCUSSION
The majority of people in the UK do not take enough exercise. The effect on health is all too apparent when we consider the burden of obesity, type II diabetes and cardiovascular disease; lack of physical activity should be considered as great a threat to health as smoking. There is strong evidence that partaking in at least 30 minutes of physical activity on five or more occasions per week can prevent and reverse/manage conditions associated with physical inactivity. However, the evidence for community-based interventions is much weaker.

This presents a dilemma for public health practitioners – we know that physical activity is good for health, but we don’t know how to get people in the community to become more active. For example, the National Service Framework for Coronary Heart Disease recommends physical activity as a preventative measure, but does not address the lack of evidence-based interventions with which to achieve this. In 2001, the Department of Health published a guidance document
Exercise Referral Systems: A National Quality Assurance Framework. However, the document is notable for an almost complete lack of evidence to support its guidelines. In order to address this gap in the evidence, a £2.6 million initiative called LEAP (Local Exercise Action Pilots) was launched by the Department of Health, the Countryside Agency and Sport England. Nine Primary Care Trusts will introduce and evaluate a range of interventions over a two-year period. However, it is unclear whether sufficient resources will follow to fund other PCTs to develop similar programmes.

CONCLUSION
Limited evidence for effective community-based approaches presents a significant challenge for public health professionals in Primary Care Trusts. In an environment under pressure to achieve targets within a limited budget, programmes without good evidence of effectiveness are often a ‘hard sell’. Nevertheless, with the majority of people not taking enough exercise and such strong evidence that physical inactivity is bad for health, it would be imprudent for Primary Care Trusts to not act.

REFERENCES
         

1. US Department of Health and Human Services. Physical Activity and Health: A report of the Surgeon General: Center for Disease Control and Prevention, National Centre for Chronic Disease Prevention and Health Promotion, 1996.
2. British Heart Foundation. British Heart Foundation Statistics Website: http://www.heartstats.org, 2003.
3. Department of Health. Diabetes National Service Framework, 2002.
4. Department of Health. More people, more active, more often. Physical activity in England. A consultation paper. London: Crown Copyright, 1995.
5. Royal College of Physicians. Medical Aspects of Exercise, 1991.
6. Health Education Authority. Health Update 5: Physical Activity, 1995.
7. Oberman A. Exercise and the primary prevention of cardiovascular disease. Journal of Cardiology 1985;55:109-22.
8. American College of Sports Medicine. The recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness in healthy adults. Medicine & Science in Sport and Exercise 1990;22:265-74.
9. Wimbush E. A moderate approach to promoting physical activity; the evidence and implications. Health Education Journal 1994;53:322-36.
10. Berlin J, Colditz G. A meta-analysis of physical activity in the prevention of coronary heart disease. American Journal of Epidemiology 1990;132:612-28.
11. Blair S, Kohl H, Paffenbarger D. How much physical activity is good for human health? Annual Review of Public Health 1992;12:99-126.
12. Activity and Health Research. Allied Dunbar national Fitness Survey: Main Findings. London: Sports Council and Health Education Authority, 1992.
13. Khan Eea. The effectiveness of interventions to increase physical activity. American Journal of Preventative Medicine 2002;22(4S):73-107.
14. Naidoo B, Thorogood M, McPherson K, Gunning-Shepers L. Modelling the effects of increased physical activity on coronary heart disease in England and Wales. Journal of Epidemiology and Community Health 1997;51(2):144-150.
15. Department of Health. National Service Framework for Coronary Heart Disease, 2001.
16. Department of Health. Exercise Referral Systems: A National Quality Assurance Framework. 2001.
17. Department of Health. Local Exercise Action Plans: www.doh.gov.uk, 2003.




This Article
Right arrow Abstract Freely available
Services
Right arrow Similar articles in this netprints
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Morgan, O. W
Right arrow Search for Related Content
PubMed
Right arrow Articles by Morgan, O. W
Related Collections
Right arrow Public Health:
Prevention and health promotion


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