This is an excerpt from Physical Activity and Mental Health by Angela Clow & Sarah Edmunds.
PAGs are evidence-based summary statements on the health benefits of physical activity and represent a high level consensus on what the scientific evidence has demonstrated by describing, in a summary format, the "dose" of the behaviour required to gain the benefits. National guidelines aimed at the whole population (as opposed to specific populations defined by a medical condition) focus on the optimal amount of activity to prevent disease and promote health and well-being. PAGs indicate the type (e.g., aerobic activity, strength training, weight bearing), frequency (e.g., 3 days/wk), duration (e.g., 30 min) and intensity (e.g., moderate, vigorous) (see figure 2.2) of physical activity to undertake and for what benefits. These detailed specifications reflect the latest science on the topic.
PAGs need to be updated periodically because evidence about the relationship between physical activity and health changes over time and knowledge grows. Some guidelines are more general in nature, whereas others provide very specific details; this usually reflects the state of knowledge at that time. Through a review and revision process, more specific details are added to PAGs when available. For example, in various national PAGs, guidelines relating to maintaining musculoskeletal strength have been revised over time and now include details on how much strength training is required for good health (World Health Organisation, 2010) and, specifically, for preventing falls and treating depression (Singh, Clements & Singh, 2001).
The dose - response relationship: Increasing benefits from increasing amounts (expressed in frequency, duration and intensity) of activity. Reprinted, by permission, from I. Vuori, 1995, Terveysliikunta [Health and physical education]. UKK Institute for Health Promotion Research (Tampere, Finland).
National guidelines are an important component of a population-based approach to addressing any public health issue. First, such guidelines communicate a consensus on the scientific evidence of the importance of the issue. They describe the strength of the science in terms of the volume as well as the quality (determined based on the quality of study designs and research methods used) of the evidence. Communicating scientific consensus is important because it removes doubt and speculation about the validity of the health issue and its importance. This scientific consensus can also be used to advocate for resources and programmes. However, just because guidelines exist does not mean that everyone agrees about what the science says - far from it. However, these disagreements, or alternative interpretations of overall findings to date, are usually communicated in technical reports that accompany the publication of PAGs and are not fully accessible to the general public.
The process of developing PAGs usually involves leadership by a high-level institution. This adds credence to the message that the issue is important. For example, several national and international health agencies, such as the American Heart Association (Haskell et al., 2007), have developed guidelines on physical activity. National governments, usually the ministry of health, often lead the development process and endorse national PAGs. This endorsement is very useful because it specifies the government's position on physical activity and thereby provides the opportunity for interested parties such as charities and public health directors to leverage the government into supporting further action and funding for programmes and services aimed at increasing physical activity. This might include government endorsement of counselling and clinical services for inactive patients, as has been trialled in the United Kingdom (Bull & Milton, 2011). Government involvement and endorsement can also prevent policy inaction. The absence of an official position on physical activity can block funding and further development of a national population-based approach.
One important role of PAGs is to direct community-level actions aimed at increasing physical activity in the whole population. The details in PAGs about the type, frequency, duration and intensity of activities required for different age groups can provide clinicians, health care practitioners and others with direction on what types of programmes to provide and promote to patients and the wider community.
PAGs should drive and direct action not just at the level of individuals and service providers but also at all levels - national, regional and local - of government. If the national government endorses PAGs, ideally with multiparty political support, the government should be held accountable when levels of physical activity are not improving and can be expected to include physical activity promotion as part of ongoing disease-prevention and health-promotion strategies. The role of PAGs and national surveillance of risk factors is discussed in more detail later in this chapter.
Development of the First National Physical Activity Guidelines
Epidemiological studies of exercise and health were well advanced by the 1970s. The American College of Sports Medicine released the first set of recommendations in 1975 and released another set in 1980 (American College of Sports Medicine, 1975, 1980). These recommendations were predominantly directed at cardiorespiratory fitness and suggested that people undertake vigorous-intensity aerobic exercise 3 times/wk for 20 min each time. This was a practical interpretation of the exact recommendation from 1975, which suggested that people undertake 20 to 45 min of physical activity 3 to 5 days/wk at 70% to 90% of heart rate (i.e., vigorous intensity) (American College of Sports Medicine, 1975). The focus on aerobic exercise for increasing fitness continued to dominate and influence health messages about physical activity until the early 1990s. However, guidelines began to recommend moderate-intensity physical activity rather than vigorous-intensity activity, and by the mid-1990s the focus shifted from cardiorespiratory fitness to health benefits. This new position on physical activity was communicated in a landmark set of recommendations from the office of the U.S. surgeon general in the report "Physical Activity and Health" (U.S. Centers for Disease Control and Prevention, 1996).
In the mid-1990s, epidemiological evidence started to show that people with different health conditions require slightly different amounts of physical activity. Although the recommendation for 30 min of moderate-intensity activity on most days remained valid for preventing heart disease and diabetes, studies showed that slightly more physical activity was recommended for preventing cancer. Further, studies identified that the amount of activity required for weight loss or preventing weight gain was greater than that required to prevent chronic disease (Haskell et al., 2007). For example, the International Association for the Study of Obesity recommendations made a clear distinction between the minimum physical activity required for health benefits and the amount required for preventing weight gain. The recommendations state that "45 to 60 min (60-90 min for formerly obese individuals) of moderate-intensity physical activity daily is needed to prevent the transition to overweight or obesity" (Saris et al., 2003). Furthermore, research has now shown that the amount of physical activity required by young people differs from that of adults. The overall amount of physical activity recommended for children is twice that recommended for adults and is usually expressed as "at least 60 min/day" (Canadian Society for Exercise Physiology, 2011a; Saris et al., 2003).
These different recommendations make the development of PAGs complex. However, a core and consistent interpretation of the evidence is that 30 min of moderate-intensity physical activity on most days of the week is associated with maximum overall population benefit and the prevention of major noncommunicable diseases. This same dose has been expressed as "at least 150 min/wk of moderate-intensity activity" in the most recent global, U.S. and U.K recommendations (Department of Health, 2011b; U.S. Department of Health and Human Services, 2008a; World Health Organisation, 2010).
Current Best Practice in Developing Guidelines
Figure 2.3 illustrates the process of developing guidelines. The first step is establishing the need for guidelines. This need is often defined by policymakers, public health scientists, advocates and, sometimes, the community. Then a process for guideline development needs to be agreed on by interested parties, with actions planned in sequence and, ideally, a linkage between the PAG development process and other aspects of national or regional physical activity policy and strategy development (step 1 in figure 2.3). The next stage comprises reviewing the scientific evidence and creating an updated summary of what the research says and how this information differs from that in previous guidelines. A number of countries, notably Canada and, most recently, the United Kingdom and United States, have undertaken this process. Tremblay and colleagues (2010) extensively discuss this process with reference to the recent Canadian guidelines along with frameworks and a checklist for auditing data quality in the review stage.
Once the science has been reviewed, the next stage is developing communication messages based on the evidence and testing these messages with the target audience for acceptability, comprehension and usefulness. This step is part of developing a communications strategy for disseminating the evidence (stages 3 and 4 in figure 2.3). It requires resources for conducting the qualitative and quantitative research and the involvement of communications and media specialists in framing the messages correctly so that they will have optimal impact on the target populations. The final stages (stages 5-7 in figure 2.3) involve disseminating the message to the community, professional groups and other stakeholders. Historically, those developing PAGs have put considerable effort into the technical and scientific stages and have often neglected message development and communication. Frequently, only informal and unpaid communication channels are used after the launch of PAGs. Thus, a very important step in PAG development and dissemination is the final public health promotion component.
Framework for developing physical activity guidelines. Adapted from Bauman et al. 2006.
Global, Regional and National Physical Activity Guidelines
Table 2.1 summarises the 2011 global PAGs and provides examples of regional (i.e., European and Western Pacific islands) and national guidelines. Quite a few countries in Europe have their own national PAGs, and many of these countries (e.g., Finland, Switzerland, the Netherlands, United Kingdom) have been engaged with implementing national population-based approaches for some time (Department of Health, 2011b; Ministry of Health, Welfare and Sport, 2011; Swiss Federal Office of Sports, 2006; UKK Institute, 2009). Other countries in Europe have officially or unofficially adopted the guidelines published by the U.S. Centers for Disease Control and Prevention in 1996 and the more recently updated 2008 version.
PAGs in other regions of the world are patchy. Australia (Department of Health and Ageing, 2005b) and New Zealand (Sport and Recreation New Zealand, 2005) have had national guidelines for some time. In Australia, guidelines exist for all ages, from young children (Department of Health and Ageing, 2004) to older adults (Department of Health and Ageing, 2005b), although all guidelines are more than 5 yr old and arguably are due for updating to reflect the latest science. Far fewer examples of PAGs exist in South America, Asia, the Middle East and Africa because physical activity promotion is relatively new in these regions. Countries in which national action on physical activity is beginning have often used the U.S. guidelines as an international benchmark. This has allowed the countries to develop an agenda of physical activity promotion without being hindered by the absence of PAGs. However, in some countries, adopting the PAGs of another country is not politically or culturally welcome or appropriate. Either these countries have developed their own PAGs (a recent example from the Middle East is Brunei; Ministry of Health, 2011) or very little physical activity promotion has occurred.
The absence of a set of official global guidelines did not hinder the World Health Organisation (WHO) from developing the Global Strategy on Diet, Physical Activity and Health in 2004 (World Health Organisation, 2004). Since the publication of the 2002 health report (World Health Organisation, 2002), the focus on the need for greater action to prevent noncommunicable disease and address mental health has increased. To address these issues, WHO commenced developing global guidelines in 2007. WHO launched the final global recommendations on physical activity in 2010 after a 2 yr process involving global and regional consultations (World Health Organisation, 2010). These global guidelines are now available for adoption and use by countries with no national PAGs. Because the guidelines are from WHO, the leading international health agency, the scientific quality and relevance of these guidelines are usually accepted.
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