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Last updated: 15-Jan-2007

Lack of Exercise

Research on the relationships between physical inactivity and health is complex due to the variety of interventions, activity measures and target outcomes that can be considered.

The concept of exercise itself, for example, needs to be fine-tuned. Experts identify three types of activities to maintain a healthy body: endurance, flexibility and strength exercises. Even choosing to focus on the general category of physical activity is not so simple, because it needs to be distinguished from various forms of physical fitness. Nevertheless, the most commonly targeted risk factor in this area is basic physical inactivity or sedentariness as measured by the time spent during the day in certain types of work-related functions or leisure-time exercise.

The rationale for pursuing exercise in weight control includes the evidence that maintenance of weight loss is enhanced with adherence to exercise programs.[1] There is also a theoretic base for utilizing exercise in weight reduction. Energy is expended in the body in a number of ways:[2]

  • thermic effect of physical activity; this can range from 0% of total expenditure to more than 50% in elite athletes
  • thermic effect of food (10-15% of expenditure relates to digestion and absorption)
  • resting metabolic rate, the amount of energy needed to maintain the structure and function of the body, accounting for 60-70% of all expenditure

Exercise can increase the expenditure in each of these pathways, as well as sometimes affecting the other side of the equation and reducing energy (i.e., food) intake; the latter effect may be primarily psychological, i.e., improved body image, self-esteem and mood allowing for better adherence to healthy eating.

Standard guidelines for physical activity commonly suggested 30 minutes or more of moderate-intensity physical activity on all, or most, days of the week; the recommended length of time per day has recently been increased to 60 minutes, especially for children.[3],[4] The following are considered examples of moderate-intensity physical activities:[5] normal walking, golfing on foot, slow biking, raking leaves, cleaning windows and light restaurant work. Jogging, brisk walking, shovelling snow and racquet sports are examples of vigorous activities.


The benefits of more strenuous exercise must be weighed against potential adverse effects, including injury, osteoarthritis and myocardial infarction. As another incentive for following a moderate daily regime, data has shown that risks associated with occasional vigorous exercise decrease when a person is engaged in regular physical activity.[6]

 

Data Sources

Several reviews will be consulted to evaluate the effectiveness of interventions aimed at increasing the level of physical activity. Cochrane is just beginning its work in this area. Of the 36 reviews in their database with either “exercise” or “physical activity” in the title, most are related to activity as an intervention in itself for various disease conditions, and only a few looked at physical activity as a preventive measure. The projects examining interventions that promote physical activity are still in the protocol stage.

The Canadian Task Force on Preventive Health Care (under its previous title, the Canadian Task Force on the Periodic Health Examination) offered a brief review of promotion in the primary care setting in 1994.[7] A more extensive review of interventions to increase physical activity was completed in 2001 by the US Task Force on Community Preventive Services (TFCPS), the group which also contributed a valuable synthesis of data on smoking interventions used in the previous section of this report. This provided an update of the literature review in the landmark US Surgeon General report of 1996, Physical Activity and Health. The UK Health Development Agency, which is cautious about some of the non-experimental studies included by the TFCPS, offers a useful “review of reviews” to test and augment the conclusions reached by the US Task Force.

The TFCPS divides the interventions to increase physical activity into four major categories, the last two still being under development:

  • informational approaches,
  • behavioural and social approaches,
  • environmental and policy approaches, and
  • urban planning approaches.

The TFCPS outline will be adapted to fit the grid which has been developed in previous sections.[8]

As has been the pattern in this report, each intervention will be briefly described and the evidence base outlined. In the end, many of the interventions currently demonstrate a scarcity of high-quality research data and / or a lack of consistent positive effect on physical activity behaviour.

 

Community-based Interventions

These interventions are large-scale, intense projects with messages directed to large audiences through different types of media, including radio and television, newspapers, billboards and mailings. The information transferred is meant to change knowledge about the benefits of physical activity, enhance awareness of opportunities to increase physical activity, and explain methods for overcoming barriers and negative attitudes impeding access to those opportunities.[9]

Community-wide campaigns have typically been a multi-component effort that also included support groups, counselling, risk factor screening and education, community events, and environmental efforts such as creating new walking trails or building exercise facilities. A complication of such interventions is the impossibility of isolating individual components for evaluation.

In a review of 10 studies, community-wide campaigns were effective in increasing physical activity, with the pooled results suggesting a median 4% growth in the proportion of people who were active.[10] This result seems to contradict the 3 well-known field trials conducted in the US in the 1980s; the studies (2 of which were included in the 10 studies noted above) were all geared towards reducing cardiovascular disease and included a range of interventions. Generally, the effectiveness of these and other community-wide approaches were described by the US Surgeon General report as “disappointing” as the gains in physical activity were mixed and, when present, modest.[11] The US Surgeon General report depended on a more limited range of studies; the pessimistic conclusion may reflect the original high hopes that surrounded the launch of these large-scale, expensive projects. The “bottom-line” is that 4% growth in physical activity, though significant, would have to be described as modest.

Mass Media Campaigns

Promotional and informational campaigns can use various media to reach a large, undifferentiated audience. These interventions are distinguished from community-wide projects by the absence of other intervention components.

One review found only 3 relevant studies. The outcome measures were the percentage of people doing a specified level of activity, change in energy expenditure and /or the percentage of the population which was sedentary. Some but not all measures showed a modest trend towards increasing levels of physical activity. The TFCPS rated the small number of studies as low in quality, and recommended caution around this intervention.[12]

The US Surgeon General report also concluded that mass media campaigns have had little impact on physical activity rates in populations.[13] However, given the intense commitment to and effectiveness of advertising in other spheres (e.g., marketing unhealthy lifestyles), it does not seem prudent to abandon this mode of intervention quite yet. The fact is that each media campaign is unique, and the most effective ones may still be in the future.

A promising example is the 10,000 steps initiative in various jurisdictions, which has sometimes been paired with pedometer (step counter) give-aways.[14] Although the research is still at an early stage,[15] many people can reach 10,000 steps a day by adding a 30-minute walk to their other routines, which can lead to significant health benefits, including weight loss.[16] Dr. Plotnikoff of the University of Alberta is testing four different strategies to encourage people with type 2 diabetes to get regular physical activity, including the use of pedometers combined with booklets to record the number of steps taken each day.[17] A much larger “natural experiment” was launched across Canada a year ago which involved the distribution of thousands of pedometers, mass advertising and a web-based evaluation system.[18]

Point-of-Decision Prompts

Signs can be placed by elevators and escalators that encourage people to use nearby stairs, with messages stressing either health benefits or weight loss. Note that this intervention can also be categorized under regulatory and economic approaches (see below).

In 5 single-intervention studies (i.e., only looking at the effect of the signs), posted messages were found to increase the number of people using stairs. Baseline rates of stair use were generally low, ranging from 4.8% to 39.6%. Adding point-of-decision prompts increased stairway usage by an average of 54%.[19]

Individually-Adapted Health Behaviour Change

These interventions focus on teaching behavioural management skills, usually in the context of social environments structured to support individuals making changes. Group or individual behavioural counselling is often part of the intervention, typically with involvement by friends or family. These kinds of interventions sometimes are found in the home, school, or work environment.

There are behaviour change programs that teach skills to individuals to help them incorporate physical activity into everyday life. The programs, which usually are tailored to individual interests and readiness for change, include goal-setting, building social support, problem-solving and relapse resistance.

All of the interventions evaluated by the TFCPS were delivered in group settings or by mail, telephone and other directed media. In 18 studies, behaviour change maneuvers directed at individuals were effective in increasing physical activity as measured by various indicators. The median estimates based on pooled results indicated a 35% increase in the time spent being physically active and 64% increase in energy expenditure. The studies recruited participants from communities, workplaces and schools. A limitation in this review was the lack of information about length of follow-up.[20]

As a comparison, the UK Health Development Agency noted two reviews covering a total of 13 RCTs where individuals were drawn from the community for treatment. Interventions included: weekly group counselling, mailed self-help materials (some based on the stage-of-change approach), exercise testing and prescription, telephone advice and support, supervised exercise in a facility, and behaviour modification. The evidence suggested the following conclusions:[21]

  • interventions targeting individuals are effective in producing short-term changes in physical activity, and could even be effective over longer terms (though, according to the US Surgeon General review, the evidence for sustained changes is not strong)
  • sustained changes are most likely with behavioral modification skills adapted to individual needs and /or regular contact with an exercise specialist
  • longer-term changes are possible with a focus on moderate intensity physical activity such as walking; recourse to vigorous sport or exercise facilities is not essential for health benefits[22]

Community (Non-Family) Social Support

There are interventions that focus on building and maintaining social networks that support behaviour change, e.g., buddy systems, walking groups, and workplace networks.

A review identified 9 relevant studies, the majority of which showed an increase in the time spent in, or frequency of, physical activity. The median net increase in time spent in physical activity increased by a range of 20-44%.[23]

 

Workplace-based Interventions

Workplaces have been seen to afford unique opportunities to enhance physical activity levels for the same reasons that tobacco control is often emphasized in such settings. One of the main attractions is simply the amount of time people spend at work, creating an accessible population possibly open to health promotion initiatives.

Examples of interventions, which are mostly directed at individuals, include:[24]

  • health screening and counselling for physical activity
  • goal-setting, reinforcement and relapse prevention
  • testing, prescription and instruction at workplace fitness facilities

The TFCPS did not isolate the workplace as a platform for physical activity enhancement, though some occupational results are incorporated in its other categories. This lack of focus is perhaps surprising in that workplace physical activity programs are reported to reduce short-term sick leave and health care costs and increase productivity.[25] It is true, on the other hand, that the evidence support for such claims appears to be meager. The same is true for overall obesity control: “very little literature explicitly addresses the promotion of healthy weights through worksite policies.”[26]

Workplace programs were evaluated in the Surgeon General report, as well as by one other major review article. [27] The conclusion is that typical workplace interventions have yet to demonstrate a significant increase in physical activity or fitness. One reason for this might be low program participation rates by employees.

Some research has examined ecological or multi-level approaches in the workplace.[28] The theoretical framework, which is not particular to occupational settings or physical activity, looks at improving a health category across a whole system in a community. The levels which can be identified include:[29]

  • intrapersonal or individual factors, e.g., employee fitness level
  • interpersonal or social factors, e.g., peer and boss influences
  • institutional / organizational / cultural factors, e.g., the leadership commitment to promoting physical activity
  • community factors, e.g., integration with wider physical activity campaigns
  • public policy, e.g., governmental incentives for focusing on physical activity

Note that the physical environment is meant to be incorporated in the other levels.

Many institutional level interventions have been suggested for physical activity in the workplace, including:[30]

  • providing activity breaks
  • encouraging “walking meetings”
  • on-site exercise facilities or reimbursement for off-site access
  • incentives for employees who “active commute” by bicycle, etc.
  • install lockers, showers and convenient bike storage
  • attractive stairwells conveniently located
  • communication and collaboration with employees to value health
  • friendly competition and rewards for group success

According to the Alberta Centre for Active Living, the ecological or multi-level approach to workplace physical activity intervention holds the greatest promise for increasing participation rates and activity levels; no experimental or other evidence is offered to support this claim.[31]

 

School-based Interventions

There are curricular programs in schools which focus on providing information about physical activity. These health education classes, which typically also address other issues such as smoking and nutrition, are often aimed at the behavioural skills for good decision-making.

A review of 10 studies showed highly variable effects, with a balance between intervention groups which showed increased physical activity and those which showed negative changes in self-reported behaviour.[32]

One systematic review from 2002 found 2 physical activity trials that specifically measured BMI changes. No significant improvements were noted in the students of the intervention groups.[33]

School-based Physical Education

Programs exist which seek to change physical education curricula to make physical education classes longer and / or more frequent, or to have students be more active during the class while at the same time enhancing the health education aspects.

Of the 13 studies identified in one review, 4 specifically measured time spent in moderate to vigorous physical activity in class and found an average increase in time was 50%. A total of 11 studies reported a significant increase in aerobic capacity.[34] These sorts of results have been part of the motivation for extensive physical education advocacy initiatives in North America, for example, PE4Life.[35]

College-age Physical and / or Health Education

Programs exist on campuses which are geared to educate post-secondary students about physical activity and encourage participation. Both a behavioural change component and actual supervised physical activity are usually included.

Only 2 studies were found in one review, with consistent increases in physical activity in the short-term, but a decline back to baseline at 2 year follow-up.[36]

 

Home-based Interventions

The most successful of the behavioural change programs adopted a home-based supervised physical activity, where the supervision was delivered by telephone and supported by printed material. The telephone support may be crucial; an Australian study published in 2004 showed no benefit at 2 and 8 month follow-up with stage-of-change physical activity materials which were simply mailed to participants.[37] The US Surgeon General report of 1996 confirms that most effective intervention components use frequent telephone contact as well as self-monitoring and incentives.[38]

Health Education to Reduce TV Viewing & Video Game Playing

Some interventions have focused on educating children about the importance of physical activity in combination with a behavioural challenge to eliminate or reduce time in front of the TV or video game screen.

A review of 3 studies, though observing sizable decreases in time spent with television and video games, did not see a consistent, significant concomitant increase in physical activity.[39]

In a 1999 study, Robinson provided curricular material geared to reduce time watching television and other video material, and found significant change in body fat measures after 7 months.[40] Although the result is being reported in the physical activity section of this report, reflecting the assumption that a reversal of sedentariness mediated the weight changes, it very well could represent a combined intervention which includes dietary improvements. As a November, 2004, review concluded: “the usual depiction of food and obesity in television has many documented negative consequences on food habits and patterns.”[41]

Involvement of Family Members

Programs can enlist the involvement of family members, sometimes with specific enhancements to encourage support of each subject receiving the main physical activity intervention. The supportive relationship can be between parents and children or between spouses. Interventions typically include joint or separate educational sessions on health, goal-setting, problem-solving, or family behavioural management. Actual physical activity may be included, plus other events if the intervention is linked to a wider school program. The combination of techniques makes it difficult to isolate the family support component.

A review of 11 studies demonstrated mixed evidence, with some producing more physical activity and some less. When home and school interventions were specifically compared with school-only approaches, there was no difference in effectiveness.[42]

 

Clinical Interventions and Management

The healthcare setting is potentially significant as a high proportion of Canadians visit a physician at least annually.[43] Patients report that primary care clinicians are expected sources of preventive health information.[44] The Canadian Health Promotion Survey showed that 60% of people making improvements in physical activity levels did so because of information about the dangers of being sedentary.[45] Other surveys suggest that less than 50% of physicians counsel patients about physical activity,[46] and even when it is provided, the counselling tends to be brief.[47],[48]

A recent review in the UK[49] assessed the following interventions:

  • brief physician advice or counselling in primary care,
  • referral to exercise specialists for education and counselling, and
  • input and support in outpatient clinics or health education classes

Brief Advice / Counselling

Brief advice can be effective, though only leading to modest, short-term gains in physical activity.[50],[51] The best results for brief advice (sometimes with back-up material) focuses on a single-factor intervention, i.e., physical activity only, and specifically activities of moderate intensity.

The Canadian Task Force on the Periodic Health Examination suggested there was insufficient evidence to show that intensive counselling interventions by general practitioners will influence sedentary individuals to be more active.[52] This is consistent with the assessment of US Preventive Services Task Force. [53],[54] Several other recent reviews have also reported on the scarcity and variability of evidence linking increased physical activity with counselling in primary care.[55],[56],[57] One Canadian reviewer suggested the opposite conclusion, stating that intensive and repeated counselling by primary healthcare providers can increase physical activity.[58]

Future studies may alter this ambiguous scenario, but in the meantime, guided by a spirit of “intuitive prudence” concerning the known health benefits of physical activity, many health agencies continue to recommend routine physical activity counselling in the primary care setting.[59] The conclusion of an Australian review is that “interventions in primary care will not be sufficient to increase physical activity levels in the population and need to be incorporated within multi-faceted, community-wide strategies to address this risk factor.”[60]

A few studies examine efforts outside of primary care. The evidence is equivocal about interventions in an outpatient clinic, but referral to exercise specialists can produce long-term physical activity improvements; in the latter case the result depended on a personalized exercise plan and incentives (i.e., reduced costs at a recreation centre).[61] Trained nurse practitioners have conducted effective physical activity promotion teaching.[62] One other venue that has produced good results for older patients is health education classes run by well-trained counselors.[63]

Continuing Medical Education

The key intervention that has been examined at the healthcare system level is attempting to improve the physical activity counselling skills and motivation of physicians through continuing medical education or other special programs. One study noted that counselling methods adopted for physical activity are sometimes ineffective.[64]

Canadian surveys of physicians have reported the following barriers to regular, effective physical activity counselling:[65]

  • time constraints
  • lack of financial incentives
  • lack of standard protocols
  • lack of success in counselling role
  • lack of appropriate training

Physicians in Canada who have been trained in physical activity counselling report greater confidence and up to a fourfold increase in the frequency of such counselling in their practice.[66],[67] One recent response to the variability of protocols was the suggestion in Nova Scotia,[68] following the lead of the Canadian Task Force on Preventive Health Care, to adopt the same “5 As” format which has been used in smoking cessation:

  • assess physical activity level, capacity and knowledge;
  • advise about risks and benefits;
  • agree on goals and a personalized action plan;
  • assist in finding community resources and creating social support; and
  • arrange follow-up and reinforcement[69]

Only 3 studies were found by the 1996 US Surgeon General report which looked at improving the physical activity counselling skills of physicians. The results point to small positive effects, with 7 to 10% of sedentary patients starting to be physically active.[70] One study included additional policy-level features, namely, reimbursement for counselling time and automatic reminders built into the physician’s practice.[71]

Exercise Therapy

It was already noted that the Cochrane review of exercise in unhealthy weight is still in process. The available effectiveness data will be outlined, but the most significant results will be found under combined interventions in the next major section of this report. This is because it is relatively rare to find exercise studied in isolation from a modified diet.

A 1995 meta-analysis of 28 exercise studies suggested that the level of weight loss achieved by increased exercise alone, i.e., without controlling caloric intake, is small. For instance, men only lost 3 kg more than sedentary controls over 30 weeks.[72] Another meta-analysis rated weight training as a more effective exercise than running, walking or cycling; it allowed men to lose 0.13 kg per week.[73]

Although the evidence to support using exercise in weight loss is limited, large-scale cross-sectional and longitudinal studies such as the Canadian Fitness survey have shown the efficacy of exercise in weight maintenance: “people who were habitually more active were found to be less obese.”[74] Thus exercise and general physical activity may have a role in preventing obesity and preventing worsening of already established overweight. Of course, it is important to remember that exercise has health benefits beyond weight reduction.

 

Regulatory and Economic Interventions

To affect whole populations, interventions in this category are directed to physical and organizational structures rather than to individuals. The aim is to increase physical activity through changing social networks or norms, creating new laws and policies, and sometimes enhancing community resources and facilities, or at least access to them (e.g., policies related to disability).

Various innovative but untested policy proposals have been put forward, such as removing taxes on exercise equipment and offering incentives to employers who promote physical activity and fitness.[75]

Transportation Policy to Encourage Non-Motorized Transit

Several agencies are conducting major review projects on the connection between transportation policy and physical activity levels, though most work is still at the stage of identifying the general links between transportation and health.[76] A US Department of Transportation roundtable began to engage this topic more thoroughly in 2004. An excerpt from their summary report reveals the close connection between transportation planning and the next major category of this report, namely, urban planning (see below):[77]

Because transportation systems affect options available for physical activity, transportation planners can have a substantial impact on the health of their communities. A community designed with sidewalks and bicycle trails that connect people's homes to their neighbors and to schools, stores, offices, parks, and other destinations encourages higher physical activity levels than one where most daily destinations can only be reached by automobile.

Good motivation exists to pursue this avenue of physical activity enhancement. It is well known that many trips currently involving automobiles are very short; an alternative such as cycling or walking a half hour a day would halve the risk of developing heart disease, equivalent to the effect of not smoking.[78] Although useful literature is beginning to emerge,[79],[80],[81],[82] incorporation of physical activity and health goals into transportation planning is a new and evolving area.

Financial levers that discourage urban sprawl and automobile commuting, such as gasoline taxes, tolls, subdivision fees and commuter subsidies, may lead to walking-friendly communities and / or more active commuting patterns, e.g., walking to transit stations.

In the only systematic review of this area, which focused on walking and cycling in particular, the best evidence suggested that such interventions have not yet proven effective, and certainly are no better than publicity campaigns or behaviour change programs.[83]

An integrated approach is certainly the “exception rather than the rule” as indicated by a 2002 review of US transportation plans which could not yet identify any examples of substantive integration of health and activity goals.[84] A major literature review of this area identified the research agenda for the future:[85]

Transportation planning agencies considering whether to include physical activity dimensions require analytical methods and scientific data to determine the significance of relationships between transportation, activity, and health, and relevance to their jurisdictions. Planners will also benefit from documentation of experiences of peers incorporating health and activity goals into planning processes. This should include before and after technical evaluations of short- and long-term effects to demonstrate the extent to which transportation affected physical activity and, ultimately, whether community health improved.

Urban Planning Approaches

The link between zoning, land use and built form, and various aspects of health, including physical activity, is an active area of research and discussion.[86],[87] According to a survey of studies, one of the more important determinants of physical activity is a person’s immediate environment (i.e., neighborhood).[88] Relevant environmental variables for enhanced activity include the presence of sidewalks, traffic calming, adequate street lighting, dog control, enjoyable scenery, regular observation of others exercising, and low crime levels. The growing conclusion is that new insight is required in urban design and planning in order to reverse the unhealthy trends of suburban sprawl:

While older cities and towns were planned and built based on the practical idea that stores and services should be within walking distance of residences, the design of most new residential areas reflects the supposition that people will drive to most destinations. Work, home, school, and shopping are often separated by distances that not only discourage walking but may even necessitate the use of a car in order to reach any destination safely.[89]

The US Active Living by Design national program office, a leading agency on the connection between urban planning and physical activity, made a presentation to Health Canada in 2004 which laid out a framework for development in this category:[90]

  • Preparations: building partnerships, vision, and a plan of action
  • Promotions: mass media for awareness and public education
  • Programs: e.g., safe routes to school, trail events, bicycle friendly communities
  • Policies: site schools to be pedestrian-friendly, zoning for mixed use
  • Projects: build network of paths, traffic calming, scenic landscaping

One of the potentially useful tools being promulgated for planners is the Health Impact Statement which, similar to an environmental assessment, would be recommended or required for any development proposal. The World Health Organization defines a health assessment as “a combination of procedures, methods and tools by which a policy, programme or project may be judged as to its potential effects on the health of a population, and the distribution of those effects within the population.”[91]

To have full confidence in any of these approaches will require an increase in basic information. Even such a central “doctrine” of environmental health planning as the association between the degree of suburban sprawl and obesity rates[92] has been recently called into question.[93] In fact, the strongest proponents of the connection between urban planning and physical activity admit that the best evidence of a connection between environmental factors and, say, utilitarian walking and biking, comes from transportation studies, and that these “are insufficient to conclude community design impacts overall physical activity.”[94] Actually isolating specific urban planning interventions and testing their impact on physical activity (and other health determinants) will be a major research challenge in the next decades.[95]

 

Comprehensive Strategies

There are various efforts made by workplaces, community coalitions and government agencies to change the local environment in terms of the opportunities for physical activity. The initiatives can include creating walking trails, building exercise facilities or improving access to existing resources. Usually such projects are part of multi-component program, where the individual initiatives cannot be isolated. Hence the whole package is evaluated as a unit. The additional components can include training in using exercise equipment, risk factor screening and referral to healthcare providers, and fitness campaigns. According to one review, creating or improving access to places for physical activity increased the frequency of exercise by a median of 48%.[96]

[1] Shaw K, Del Mar C, O’Rourke P et al. Exercise for obesity Cochrane Database of Systematic Reviews, 2004.

[2] Shaw K, Del Mar C, O’Rourke P et al. Exercise for obesity Cochrane Database of Systematic Reviews, 2004.

[3] See, for example, the US Surgeon General’s Call to Action to Prevent and Decrease Overweight and Obesity, 2001. Available at http://www.surgeongeneral.gov/topics/obesity/ (accessed November 2004).

[4] Nutrition Recommendations for Canadians: Draft Recommendation on Energy. Available at http://www.hc-sc.gc.ca/hpfb-dgpsa/onpp-bppn/comment_period_rec_on_energy_e.pdf (accessed November 2004).

[5] A moderate amount of physical activity uses approximately 150 Calories (kcal) of energy per day, or 1,000 Calories per week.

[6] Beaulieu MD. Physical activity counselling. In: Canadian Task Force on the Periodic Health Examination. Canadian Guide to Clinical Preventive Health Care. Ottawa: Health Canada, 1994.

[7] Beaulieu MD. Physical activity counselling. In: Canadian Task Force on the Periodic Health Examination. Canadian Guide to Clinical Preventive Health Care. Ottawa: Health Canada, 1994.

[8] Source: http://www.thecommunityguide.org/pa/default.htm (accessed November 2004). Also in Kahn EB, Ramsey LT, Brownson RC et al. The effectiveness of interventions to increase physical activity. a systematic review American Journal of Preventive Medicine 2002; 22(Suppl 4): 73-10.

[9] Kahn EB, Ramsey LT, Brownson RC et al. The effectiveness of interventions to increase physical activity. a systematic review American Journal of Preventive Medicine 2002; 22(Suppl 4): 73-10.

[10] Kahn EB, Ramsey LT, Brownson RC et al. The effectiveness of interventions to increase physical activity. a systematic review American Journal of Preventive Medicine 2002; 22(Suppl 4): 73-10.

[11] Physical activity and health: a report of the Surgeon General. Atlanta, GA: US Department of Health and Human Services, 1996.

[12] Kahn EB, Ramsey LT, Brownson RC et al. The effectiveness of interventions to increase physical activity. a systematic review American Journal of Preventive Medicine 2002; 22(Suppl 4): 73-10.

[13] Physical activity and health: a report of the Surgeon General. Atlanta, GA: US Department of Health and Human Services, 1996.

[14] For example, see the description of the Queensland, Australia project at http://www.centre4 activeliving.ca/Publications/WellSpring/2003/ Spring/10000Steps.html (accessed December 2004).

[15] Tudor-Locke C, Bassett DR. How many steps/day are enough? Preliminary pedometer indices for public health Sports Medicine 2004; 34(1): 1-8.

[16] See for example the results summarized on the website at http://www.diabetesincontrol.com/ studies/steps.pdf (accessed December 2004).

[17] For details see http://www.google.ca/search?q=cache:XdB6dQ1gXBIJ:www.cihr-irsc.gc.ca/e/ 25276.html+british+columbia+pedometers&hl=en (accessed December 2004).

[18] CIHR Institute of Nutrition, Metabolism and Diabetes (at Simon Fraser University). Available at http://www.cihr-irsc.gc.ca/e/18058.html (accessed December 2004).

[19] Task Force on Community Preventive Services. Available at http://www.thecommunityguide.org/pa/ default.htm (accessed November 2004).

[20] Task Force on Community Preventive Services. Available at http://www.thecommunityguide.org/pa/ default.htm (accessed November 2004).

[21] Hillsdon M, Foster C, Naidoo B et al. The Effectiveness of Public Health Interventions for Increasing Physical Activity Health Development Agency, 2004.

[22] A study has shown that those with the highest cardiorespiratory fitness levels consistently walked more than those with lower levels. Stofan JR, DiPietro L, Davis D et al. Physical activity patterns associated with cardiorespiratory fitness and reduced mortality: the Aerobics Center Longitudinal Study American Journal of Public Health 1998; 88(12): 1807-13.

[23] Kahn EB, Ramsey LT, Brownson RC et al. The effectiveness of interventions to increase physical activity. a systematic review American Journal of Preventive Medicine 2002; 22(Suppl 4): 73-10

[24] Dishman RK, Oldenburg B, O'Neal H et al. Worksite physical activity interventions American Journal of Preventive Medicine 1998; 15(4): 344-61.

[25] Physical activity and health: a report of the Surgeon General. Atlanta, GA: US Department of Health and Human Services, 1996.

[26] Raine KD. Overweight and Obesity in Canada: A Population Health Perspective. Centre for Health Promotion Studies, University of Alberta, 2004.

[27] Dishman RK, Oldenburg B, O'Neal H et al. Worksite physical activity interventions American Journal of Preventive Medicine 1998; 15(4): 344-61.

[28] Stokols D, Pelletier KR, Fielding JE. The ecology of work and health: research and policy directions for the promotion of employee health Health Education Quarterly 1996; 23(2): 137-58.

[29] McElroy KR, Bibeau D, Steckler A et al. An ecological perspective on health promotion

programs Health Education Quarterly 1988; 15: 351-377.

[30] Fruits and Vegetables and Physical Activity at the Worksite. California 5 a day Worksite Program, no date. Available at http://www.phi.org/pdf-library/dhs-worksite.pdf (accessed November 2004).

[31] Program description at http://www.centre4activeliving.ca /Research/2003Workplace/ BeforeYouStart.htm (accessed November 2004).

[32] Kahn EB, Ramsey LT, Brownson RC et al. The effectiveness of interventions to increase physical activity. a systematic review American Journal of Preventive Medicine 2002; 22 (Suppl 4): 73-10.

[33] University of York. The prevention and treatment of childhood obesity Effective Health Care 2002; 7(6).

[34] Kahn EB, Ramsey LT, Brownson RC et al. The effectiveness of interventions to increase physical activity. a systematic review American Journal of Preventive Medicine 2002; 22(Suppl 4): 73-10.

[35] Website available at http://www.pe4life.org/ (accessed November 2004).

[36] Kahn EB, Ramsey LT, Brownson RC et al. The effectiveness of interventions to increase physical activity. a systematic review American Journal of Preventive Medicine 2002; 22(Suppl 4): 73-10.

[37] Marshall AL, Bauman AE, Owen N et al. Reaching out to promote physical activity in Australia: a statewide randomized controlled trial of a stage-targeted intervention American Journal of Health Promotion 2004; 18(4): 283-7.

[38] Physical activity and health: a report of the Surgeon General. Atlanta, GA: US Department of Health and Human Services, 1996. See also King AC. Role of exercise counselling in health promotion British Journal of Sports Medicine 2000; 34: 80-1; and the review in Castro CM, King AC. Telephone-assisted counseling for physical activity Exercise & Sport Sciences Reviews 2002; 30(2):64-8.

[39] Kahn EB, Ramsey LT, Brownson RC et al. The effectiveness of interventions to increase physical activity. a systematic review American Journal of Preventive Medicine 2002; 22(Suppl 4): 73-10.

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[46] Wechsler H, Levine S, Idelson RK et al. The physician's role in health promotion revisited--a survey of primary care practitioners New England Journal of Medicine 1996; 334(15):996-8. Some estimates are as low as 12% of physicians prescribing exercise appropriately in their practice.

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