Population Health: Behavioral and Social Science Insights

Physical Activity: Numerous Benefits and Effective Interventions

By James F. Sallis and Jordan A. Carlson

Abstract

Physical activity has been required for obtaining food, work, and transportation throughout human history, until recently. Physical inactivity is now one of the leading causes of death, responsible for an estimated 5.3 million deaths per year worldwide, through its effects on cardiovascular diseases, diabetes, and some cancers. Physical activity's benefits for brain structure and function have emerged more recently. Prevalence rates of meeting physical activity guidelines vary dramatically, depending on whether self-report or objective measures are used. However, prevalence of meeting physical activity guidelines appears to be low among adults and youth in the United States and is decreasing worldwide. Thus, physical inactivity has been identified as a global pandemic. Numerous interventions to increase physical activity have been demonstrated to be effective in systematic reviews. Some interventions target individuals, such as educational programs delivered by in-person counseling, telephone, or computer. Other interventions target groups and organizations, such as social support groups, school physical education, and comprehensive worksite programs. Environmental interventions to improve access to and the quality of walkable neighborhoods, facilities for pedestrians and cyclists, and recreation facilities can also be effective. However, there is limited evidence that effective interventions are being widely implemented. Failure to act on the evidence of burden of disease, low prevalence, and effective interventions is costing millions of lives each year. Research priorities include implementation and dissemination of effective interventions, economic analyses of physical activity, and "natural experiments" to evaluate multi-level and policy interventions.

Introduction

Physical activity comprises a set of behaviors that appears to play a unique role in health and well-being due to a wide range of benefits. Physical activity is a strong protective factor from premature mortality, most of the leading chronic diseases, risk factors for chronic diseases, and common mental health problems, such as depression and anxiety and Alzheimer's disease.1 Possibly because physical activity requires integrated and coordinated functioning of the whole body, it appears to benefit many biological systems. Throughout human history, physical activity has been required for obtaining food, working, getting from one place to another (transportation), and performing household chores. Dance and sports were developed in virtually every culture for pleasure and cultural expression.

Mechanization started during the Industrial Revolution and replaced many types of labor, both at work and at home. Activity is no longer required to obtain food. Automobiles have largely replaced walking for transportation in recent decades. Dance and leisure have become mostly spectator activities, while the ever-increasing options for electronic entertainment have become the dominant form of leisure activity. These long-term trends have helped produce inactive lifestyles in most of the world's populations, and the profoundly negative consequences for health have been extensively documented. Physical inactivity has become one of the biggest threats to worldwide health.2

Though many evidence-based interventions are available to increase physical activity, they have not been widely implemented; the prevalence of sufficient physical activity in the United States remains low, with few signs of improvement. Thus, there is a compelling need for increased attention to and investment in physical activity interventions.3

In this chapter, we summarize the numerous health effects of physical activity, with a special focus on less-familiar effects on brain and cognitive functioning. Prevalence, trends, and correlates of physical activity are briefly summarized. Substantial research has produced a diverse array of evidence-based interventions. Rationales for research, policy, and improved practice for physical activity are presented.

Breadth and Strength of Health Impacts

A recent analysis revealed that physical inactivity is responsible for over 5 million deaths annually worldwide, which is similar to the death toll of tobacco smoking.4 The World Health Organization estimates that physical inactivity is the fourth leading cause of death globally; lower than hypertension and tobacco smoking, similar to obesity, and higher than dietary patterns and hyperglycemia. Most of the inactivity-related deaths are in low- and middle-income countries, so this is not just a concern in high-income countries.2 Some consider physical inactivity to be a global pandemic.3 Physical inactivity also is the fourth underlying cause of death in the United States, with an estimated 200,000 deaths per year. This is about half the deaths attributable to tobacco smoking but twice the deaths attributable to alcohol use and low intake of fruits and vegetables.5

Physical activity affects health and disease through many pathways and systems. The Report of the Physical Activity Guidelines Advisory Committee consisted of almost 700 pages of systematic literature reviews.1 They found strong evidence that physical activity reduces risk of premature mortality, coronary heart disease, high blood pressure, stroke, metabolic syndrome, type 2 diabetes, breast cancer, colon cancer, depression, and falling, and it is associated with improved body composition, bone health, functional health, and cognitive health. It is likely that physical activity provides a broader range of documented health benefits than any other factor (e.g., behavior, medication, or medical procedure).

The strength of the effects of physical activity on leading chronic diseases is notable. In a recent review, I-Min Lee and colleagues4 conservatively calculated that physical inactivity accounts for 5.8 percent of deaths from coronary heart disease, 7.2 percent from type 2 diabetes, 10.1 percent from breast cancer, and 10.4 percent from colon cancer. These calculations, while impressive, are almost certainly underestimated because they were adjusted for risk factors that are affected by physical activity such as obesity, lipids, and glucose. A U.S. study indicated that inactive adults would gain 1.3 to 3.7 years of life expectancy by becoming active at age 50.6 This result compares favorably to 2.3 to 2.5 years gained among smokers who quit at age 50 and 0.5 to 0.7 years gained by all obese people becoming normal weight at age 50.7 A recent study using national U.S. data estimated that 9-11 percent of aggregate U.S. health care expenditures were associated with physical inactivity.8

Brain and Cognitive Health

This section summarizes substantial recent evidence showing that the cognitive decline of aging can be ameliorated through physical activity. A review of three meta-analyses on physical activity interventions in older adults concluded that the beneficial effects on cognitive functioning were medium to large for executive functioning (e.g., working memory, reasoning, problem solving; d (effect size) = 0.58), with somewhat smaller effects for spatial (d = .36), controlled (d = .33), and speed tasks (reaction time; d = .19; see Figure 1).9 Furthermore, a meta-analysis of 12 randomized trials in older adults with dementia found that physical activity ameliorated cognitive impairments (d = .57).10

Figure 1. Effect sizes and 95% confidence intervals for effects of physical activity on cognitive functioning in older adults

Figure shows effects sizes and 95 percent confidence intervals for the effects of physical activity on cognitive functioning in older adults. It shows that the beneficial effects of physical activity were medium to large for executive functioning, including working memory, reasoning, and problem solving; beneficial effects were somewhat smaller for spatial, controlled, and speed tasks.

Source: Kramer, Erickson, 2007.9 Used with permission.

Physical activity also has benefits for children's cognitive functioning.11 A meta-analysis of 44 studies in children found small to medium effect sizes for physical activity on various cognitive measures, with the largest effect for perceptual skills (d = .49; refer to Figure 2).12 A single 20-minute bout of physical activity resulted in improved response accuracy, better performance on an academic achievement test, and more brain activity during cognitive tasks.13

Figure 2. Effect sizes and 95% confidence intervals for effects of physical activity on cognitive functioning in youth

Figure shows effect sizes and 95 percent confidence intervals for effects of physical activity on cognitive functioning in youth. It shows that the effects of physical activity on cognitive functioning were small to medium in youth, with the largest effect for perceptual skills.

Source: Sibley, Etnier, 2003.12 Used with permission.

While evidence supports the use of brain training games to improve cognitive functioning, the cognitive benefits from brain training typically do not transfer to cognitive tasks other than the task on which the training was based.14 By contrast, the cognitive benefits of physical activity are both large and generalized, meaning the benefits are observed across multiple systems in the brain.15,16

Several mechanisms link physical activity to improved brain health and cognition. Physical activity stimulates brain-derived neurotropic factor (BDNF) and insulin-like growth factor 1 (IGF-1).11 These proteins released in the brain trigger angiogenesis, the growth of new blood vessels in the brain, and neurogenesis, the growth of new neurons in the brain, which contribute to learning and memory.17

Prevalence and Trends of Meeting Physical Activity Guidelines

The overwhelming evidence about the numerous health benefits of physical activity was the basis for the first official physical activity recommendations in the United States1 and from the World Health Organization.18 The basic recommendation for adults is to accumulate at least 150 minutes of moderate intensity physical activity weekly, 75 minutes of vigorous intensity activity weekly, or some combination of the two. The main recommendation for youth is to accumulate at least 60 minutes per day of moderate to vigorous physical activity.

The prevalence of physical activity varies dramatically by measurement method, with higher prevalence estimates based on self-reports and lower estimates based on objective measures. However, by all methods the prevalence of meeting guidelines is low. Physical activity among adults in the United States is generally higher among younger people, males, people with higher education, and non-Hispanic whites. The groups with lower physical activity are generally at higher risk of chronic diseases. Based on self-reports of leisure time physical activity, prevalence rates of meeting guidelines in 2005 ranged from 62 percent in men aged 18-24 to 44.5 percent in men over 65 and from 52.7 percent in women aged 18-24 to 36.3 percent in women over 65.1 Comparisons across 122 countries using the International Physical Activity Questionnairea yielded an estimate that 31 percent of adults worldwide were insufficiently active. The range was 4.7 percent in Bangladesh to 71.9 percent in Malta, with the United States having an inactivity prevalence of 33.5 percent for men and 47.4 percent for women.19 Active transportation to work was compared across 16 high-income countries. The United States had one of the lowest rates of walking to work (3 - 4 percent); the rate of walking to work in China, Germany, and Sweden was 20 percent. The United States also had one of the lowest rates of cycling to work (0.5 - 3 percent), which was much lower than in China, Denmark, and the Netherlands (>20 percent).

Prevalence rates for adolescents were compared for 105 countries. About 80 percent of 13-15 year-olds did not meet the youth physical activity guideline of 60 minutes every day, based on self-report.19

Four countries (Norway, Portugal, Sweden, United States) have conducted national prevalence studies of adults using objective accelerometers that are typically worn for 1 week and provide minute-by-minute activity levels. Variation across countries was modest for men, with the United States having the lowest average of moderate-to-vigorous physical activity (33 minutes per day) and Portugal having the highest (37 minutes per day). There was more variation for women, ranging from 19 minutes per day in the United States to 45 minutes per day for Portugal.19 Using a rigorous method of scoring the accelerometer data, prevalence of meeting guidelines among U.S. adults was less than 5 percent.20 Samples of adolescents from 10 countries (N > 30,000) had accelerometer data. Minutes of physical activity per day ranged from 45.9 in the United States to 83.6 in Norway.19

Though physical activity prevalence estimates vary, it is most likely that at least a majority of adults and youth are exposed to the multiple, strong, and negative health consequences of physical inactivity. On all measures except self-reported physical activity of adults, people in the United States are low, if not the lowest, in international comparisons. Research to identify the modifiable factors that account for these international differences could point the way to promising interventions.

Physical Activity Trends

Though trends for tobacco consumption are available for about 100 years, and trends that allow estimates of food intake are available for many decades, national physical activity surveillance for adults was only initiated in the mid-1980s in the United States. The National Health Interview Survey (NHIS) assessed leisure time physical activity in a national sample of adults, and results from 1997-2006 show no change over time (Figure 3).1,21 Short-term trends for adolescent physical activity from the Youth Risk Behavior Surveillance System (YRBSS)b similarly showed no change from 1999 to 2006.1

Long-term trends in active transportation can be derived from periodic travel studies conducted by the U.S. Department of Transportation. Over 40 percent of students walked or cycled to school in 1969, but by 2001 the prevalence had declined to about 14 percent.22 Brownson and colleagues23 found long-term evidence supporting conclusions that physical activity at home, at work, and for transportation have declined substantially among Americans in the past 50 years, though leisure time physical activity has remained relatively stable.

Figure 3. Reported physical activity by adults in the United States

Figure shows fairly stable levels of physical activity as reported by adults in the United States for the period 1997 to 2006. Reports were either no leisure-time physical activity (about 40 percent of the population), regular moderate or vigorous physical activity (about 30 percent of the population), or muscle strength and endurance activities (15 to 20 percent of the population).

Source: Physical Activity Guidelines Advisory Committee1; Healthy People 202021 Used with permission.

Etiology of Physical Activity: From Genes to Built Environments

Hundreds of studies have examined correlates (cross-sectional) and determinants (prospective) of physical activity. Such studies identify possible mechanisms of change that can be targeted in physical activity interventions, but the number and diversity of potential etiological variables demonstrate the challenges faced by those attempting to improve public health through increasing physical activity.

An analysis of reviews identified a wide range of variables consistently related to physical activity, including factors at biological, psychological, social, organizational, environmental, and policy levels of analysis.24 Biology is working against efforts to increase physical activity. The age decline in physical activity documented in humans, rats, fish, and insects has been attributed to loss of dopamine receptors in the nucleus accumbens. This area of the brain links movement and reward centers, so as they age, people become less able to derive pleasure from movement.25 It is clear that genes affect physical activity, based on heritability estimates. Genes could be involved in variations in experiencing reward and pain from physical activity, but few specific genes have been linked to physical activity.24

Understanding psychological and social correlates and determinants of physical activity can provide guidance to the design of interventions. Psychological correlates/determinants include intention to be active and self-efficacy, or confidence in one's ability to be active in specific situations. Stress may be a barrier to physical activity. Surprisingly, social support and social norms were not consistently identified as correlates/determinants by the reviews.24

Built environment correlates/determinants of physical activity is a relatively recent topic of research on modifiable factors that when properly designed could have long-term effects on large populations. Environmental factors are expected to have effects that are specific to the domain of physical activity, with walking being the most studied physical activity outcome.26 For example, walking for transportation is expected to be higher among those living in neighborhoods with shops and services nearby (i.e., mixed use) and connected streets. The literature generally supports this hypothesis for youth but less so for adults.24 Walking for leisure is expected to be related to the aesthetics of the area, presence of sidewalks, and design of street crossings. Leisure activity more generally is expected to be related to proximity of recreational facilities, such as parks. These hypotheses have generally been supported in the literature for youth and adults.24 Total physical activity was consistently related to at least one variable in five categories of neighborhood environments, especially recreation facilities, transportation environments, and aesthetics. These results illustrate the important role that city planners, transportation engineers, and parks and recreation sectors need to play in creating activity-supportive environments.

Multiple Effective Interventions

The science of physical activity interventions is well advanced, based on more than 30 years of research, much of it supported by the National Institutes of Health (NIH). Many evaluated interventions are based on theories of behavior change, randomized controlled trials are common, and the literature is frequently reviewed.27 This section highlights systematic reviews of interventions mainly targeted to non-clinical populations.

Interventions can be designed to change one or more of the levels of influence outlined in ecological models of behavior, including individuals, groups, organizations, communities, environments, and policies.28 Most evaluated interventions target individuals and groups, and many randomized controlled trials have been reported. Except for interventions that only provide group exercise classes, most behavior change programs strive to enhance motivation and teach skills that allow individuals to modify their own behaviors. Modes of communication include individual counseling, group classes, printed materials, telephone counseling, and more recently, Web sites, text messaging, and mobile apps. There is a substantial literature targeting organizations and communities as a means of reaching large numbers of people with behavior change programs and creating supportive social environments. Studies of organizational interventions conducted in schools, worksites, and faith-based institutions are often randomized, but studies targeting whole communities are almost always quasi-experimental.

Recently, environmental and policy interventions and multi-level interventions have become more common, informed by ecological models of behavior.29 Environmental interventions have ranged from signs promoting the choice of stairs rather than nearby escalators to construction or renovation of sidewalks, parks, and trails. These studies often are "natural experiments" or opportunistic aluations of interventions not controlled by investigators but implemented by local governments. Evaluations of environmental and policy changes on a larger scale—such as multi-year multi-component bicycle promotion, implementation of new zoning laws, or construction of public transit facilities—use uncontrolled pre-post evaluations, post-test-only comparisons with control areas, or historical data. Though multi-level interventions that include environmental and policy changes are expected to produce broad and long-lasting impacts, less rigorous study designs must be used than with interventions targeting individuals.

In the United States, the most definitive reviews for population health purposes are from the Web-based Guide to Community Preventive Services, sponsored by the Centers for Disease Control and Prevention (CDC).c The reviews of physical activity interventions were published in the early 2000s.30 Types of interventions included information, behavioral and social, organizational, and environmental and policy; the results of the review are shown in Table 1. Several intervention types were identified as effective, while others had insufficient evidence. A subsequent analysis found good cost-effectiveness for virtually all of the interventions.31 The most cost-effective approach was signage to encourage stair use, though these interventions had small effects. Individually-adapted behavior change interventions had the lowest cost-effectiveness, but they produced the strongest effects (35-43 percent of recommended daily physical activity).

Table 1. Physical activity intervention recommendations from the Community Guide to Preventive Services

Strategy Level of Evidence
Point-of-decision prompts Effective
Community-wide campaigns Effective
Mass media campaigns Insufficient
School-based PE Effective
Health education Insufficient
Family support Insufficient
Social support Insufficient
Individually-adapted program Effective
Places for PA + outreach Effective

Source: Kahn, Ramsay, Brownson, et al., 2002.30 Used with permission. Note: PA = physical activity; PE = physical education.

A further "Community Guide" review of built environment interventions was based mainly on cross-sectional studies (i.e., post-intervention comparisons).32 Community-scale design and land use studies often compare walkable communities defined by mixed use (destinations within walking distance of homes), high residential density, grid-like pattern of connected streets, and sidewalks to suburban-style, automobile-oriented communities with separation of land uses, low residential density, and poorly connected streets. Residents of walkable communities had a median of 161 percent more physical activity, providing strong evidence of effectiveness. Street-scale urban design and land use interventions consisted of improved lighting, landscaping, traffic calming, improved sidewalks, and safer street crossings. These approaches were also found to be effective.32

Heath and colleagues33 conducted a review of systematic reviews of physical activity interventions targeting individuals and groups; the results are shown in Figure 4. Though effect sizes varied substantially, interventions of all types and with all specific populations were significant, with two exceptions. The lowest significant effect sizes were with computer-tailored programs and counseling in health care. Among the strongest effect sizes were those for Web-based programs, after school programs, and programs including use of pedometers.

Figure 4. Meta-analysis of physical activity intervention effect sizes with 95% confidence intervals

Figure depicts the results of a meta-analysis of data on physical activity interventions targeting individuals and groups and shows effect sizes and 95 percent confidence intervals for 12 variables.

Source: Heath, Parra-Perez, Sarmiento, et al., 2006.33 Used with permission.

Mozaffarian and colleagues34 conducted a systematic review of population-based physical activity interventions. Numerous intervention types were judged to have sufficient evidence to justify widespread implementation. Some findings confirmed results of "Community Guide" reviews: signs encouraging stair use, enhanced school physical education, and community-scale land use and walkability. Other recommended interventions reflected more recent evidence for schools (comprehensive multi-behavior programs, improved playgrounds and equipment, classroom activity breaks), worksites (comprehensive multi-behavior programs, scheduled time for physical activity at work, fitness centers at work), and communities (improved access to parks, improved safety of pedestrian facilities to support walking to school, improved traffic safety, improved aesthetics).

A report from the President's Council on Fitness, Sports and Nutrition35 on strategies to increase physical activity in young people found that most of the interventions with strong evidence of effectiveness were in schools, such as using multiple strategies to increase physical activity throughout the school day and providing highly active physical education. Active commuting to school and classroom activity breaks had less support. Various interventions in preschool and community built environment strategies had suggestive evidence. After school programs, family-based programs, and interventions in primary care had insufficient evidence (Table 2).

Table 2. Conclusions about effectiveness of youth physical activity interventions

Strategy Level of Evidence
Multi-component school programs Sufficient
Physical education Sufficient
Active transportation Suggestive
Activity breaks in classroom Suggestive
School physical environment Insufficient
After school Insufficient
Preschool and childcare settings Suggestive
Built environment Suggestive
Home & family Insufficient
Primary care Insufficient

Source: President's Council on Fitness, Sports, and Nutrition, 2013.35 Used with permission.

Although there is some disagreement across reviews regarding support for specific intervention types, all reviews identified multiple interventions with strong evidence of increasing physical activity. Strategies targeting individuals, organizations, and community built environments were found to be effective. However, not all interventions were supported by the evidence. Thus, interventions need to be carefully selected for further implementation, and continued research is needed for understudied approaches and those with conflicting results.

Effective Strategies Not Implemented

Despite the availability of evidence-based and cost-effective interventions targeting individuals, groups, organizations, communities, and built environments, there is little indication that any of these interventions are being widely implemented in the United States. However, it is difficult to know with certainly because there is little surveillance of physical activity intervention implementation. There seems to be no systematic implementation of individually-tailored counseling or group behavior change programs. Even the most cost-effective intervention, signs encouraging stair use, is rarely applied. Almost all community-wide physical activity campaigns in the United States have been conducted in the context of research. Investment in pedestrian and bicycle facilities has remained less than 1 percent of Federal transportation funds, with the exception of a spike to 2 percent investment during the American Recovery and Reinvestment Act in 2009-2010.36 Even though Web-based physical activity programs are plentiful, most are not evidence-based and have not been designed consistent with principles of effective behavior change.37

Physical education may be the largest societal investment in a physical activity intervention, and this is one of the few interventions for which some surveillance occurs. Though most States have physical education requirements, they vary widely and mainly address minutes of class time. Most physical education is not consistent with evidence-based practices of optimizing physical activity, and there is substantial evidence that on average, only about one-third of physical education class time is spent in physical activity.38 However, in recent years 16 States have adopted laws or regulations requiring students to be active at least 50 percent of physical education class time or specifying that students must achieve a certain amount of physical activity throughout the school day, usually 30 minutes. Though this attention to physical activity in schools is encouraging, none of the regulations provide sufficient monitoring, consequences, or funding.39 Thus, it is unlikely these regulations will have much effect.

There have been some recent major funding programs for environment, policy, and systems approaches to obesity prevention that included physical activity. "Stimulus" funding during the recession for Communities Putting Prevention to Work (CPPW; 2010-2012) and Affordable Care Act funding for Community Transformation Grants (CTG; 2012-2014) were administered by the CDC. However, the CTG program was cancelled before most interventions had begun. Both programs provided hundreds of millions of dollars for cities and States to support environment and policy interventions that were likely to be consistent with recent evidence,34 so these programs may be among the largest commitments to physical activity interventions in U.S. history. Unfortunately, it is not clear how much of the funding was devoted to physical activity interventions, to what extent evidence-based interventions were supported, or what the effects were. Evaluation results are still pending.

Conclusions

The current status of the physical activity field is that the tremendous potential for public health benefit has not been achieved due to failure to widely implement the many evidence-based interventions. Physical inactivity is the fourth leading cause of death in the United States and worldwide,2,5 and physical activity appears to be unique as a behavior that positively affects so many major diseases and conditions.1 The need for improving physical activity is urgent, given the burden of disease, low prevalence rate, and flat (leisure time activities) or declining (active transportation) trends in both adults and adolescents.21,22 The tools for increasing physical activity are available in the form of numerous evidence-based and cost-effective interventions. Thus, the physical activity research field has had dramatic successes in building evidence in several critical areas, though many questions remain. The biggest problem in the physical activity field is the failure to act on the evidence and make serious and well-funded efforts to implement evidence-based interventions.

Recommendations for Practice

Increased commitment to physical activity promotion is needed in the government, non-profit, and private sectors. Limited commitment can be seen at the Federal Government level, with CDC having a very small Physical Activity and Health Branch, the Department of Health and Human Services and NIH lacking offices for coordinating physical activity work, and the Department of Education having no person in charge of physical education. Most State public health departments typically have one person devoted to physical activity, who may not be full time in that role and is often paid through a CDC grant. Increased funding for physical activity in all of these agencies is a prerequisite for making progress.

The lack of commitment also can be seen in the private sector, with most physical activity enterprises such as health clubs, dance studios, and Web sites not implementing evidence-based strategies. Insurance companies rarely pay for physical activity interventions, except for time-limited programs for people with specific diagnoses such as cardiac rehabilitation. These industries are encouraged to commit to broad implementation of evidence-based interventions. Partnerships with the public health sector and scientific community are encouraged to increase uptake of evidence-based interventions.

Recommendations for Research

Given that physical activity affects so many biological systems, it is reasonable to expect widespread effects on gene expression. Because of the possibility that inactive lifestyles could increase risk of disease in offspring, research on the effects of physical activity on gene expression and epigenetics should be increased.

Studies of the multiple economic and societal costs of physical inactivity and the co-benefits of physical activity should be prioritized. Economic data could be more effective than health outcome data to persuade decisionmakers to increase investments in physical activity interventions.

Evidence that physical activity, particularly active transportation, could contribute to reducing carbon emissions needs to be strengthened and quantified.40 Exploring and quantifying diverse indirect and non-health impacts of active transportation and related built environment and policy interventions is a significant research need that would require collaborations between NIH and other agencies such as the Department of Transportation and the Environmental Protection Agency.

Reasons for the wide variation in physical activity across countries are not clear. A better understanding of effective strategies used around the world to promote physical activity should lead to better interventions that could be adapted and applied in the United States.

Measurement of physical activity is an ongoing challenge. Though substantial progress has been made in objective assessment using accelerometers and pedometers, further improvements in both electronic and self-report measures are needed. For example, integration of accelerometer measures with global positioning systems (GPS) and geographic information systems (GIS) allows assessment of the time and space dimensions of physical activity. This combination of methods can be used to improve assessment of both active and passive modes of transportation, as well as identify the times and places of active recreation. Mobile phones and commercial accelerometers could be used on a large scale for research and ongoing monitoring of physical activity in the population.41 Another priority is to reduce the cost and simplify the use, data management, and data analysis of electronic measures such as accelerometers.

Self-report measures will continue to play an important role in research and public health surveillance.42 One priority is to use electronic devices, such as smart phones and smart watches, to improve self-reports by triggering queries based on time, place, or movement patterns. Another priority is to improve assessment of physical activity in the specific domains of leisure, transport, occupation, and household, because interventions need to be specific for each domain.

Enhanced electronic and self-report measures of physical activity could improve all facets of physical activity research, with the most critical contributions likely being (1) updating physical activity guidelines and (2) evaluating interventions. Almost all epidemiologic studies of physical activity and health outcomes used in creating physical activity guidelines were based on self-report measures, mainly of leisure time activity.1 Thus, it is not known how the total dose of physical activity relates to health outcomes. It is important to apply objective and domain-specific self-report measures in epidemiological studies to refine understanding of dose-response relations that could lead to updated physical activity recommendations. Limited use of objective measures in intervention studies and excessive use of unvalidated self-reports likely lead to interpretation errors in intervention studies and underestimates of effects. Thus, better physical activity measures in intervention studies could enhance confidence in the results and perhaps reduce inconsistent findings across studies.

Though many effective interventions have been developed, there is a continuing need for stronger interventions as well as interventions tailored to high-risk populations, including demographic subgroups at high risk of inactivity-related diseases. A general recommendation for intervention research is to include cost-effectiveness analyses to assist practitioners and policymakers in selecting among intervention options. Research on individually-targeted interventions should focus on those that integrate technology, because Web- and mobile-based interventions have the potential for widespread impact at modest cost. Technology-based interventions should be assessed among people with low educational attainment, because graphics, photos, and videos may have special appeal for people with limited reading skills.

Multi-level interventions integrating efforts of multiple sectors (e.g., urban planning, transportation, parks, education) have the most potential to change population levels of physical activity over the long term. However, these interventions present several inherent design and methodological challenges, so special funding initiatives will be required to support progress, and more creative, rigorous, and long-term natural experiments are needed.

Because multi-level physical activity interventions require collaborations with decisionmakers in non-health sectors of society, research on effective communication of evidence-based strategies and their benefits to decisionmakers might accelerate the translation of research to practice and policy.

Since many evidence-based interventions for increasing population levels of physical activity exist, current research should focus on identifying how to more effectively translate these interventions into widespread practice. This requires testing implementation and dissemination strategies and adapting interventions for a new population or for scaling up activities.

Because of the profound health consequences, low prevalence rates, and unfavorable trends, a much higher priority on physical activity research is justified.

Authors' Affiliations

James F. Sallis, PhD, Department of Family and Preventive Medicine, University of California, San Diego. Jordan A. Carlson, PhD, Department of Family and Preventive Medicine, University of California, San Diego

Address correspondence to: James F. Sallis, PhD, Department of Family and Preventive Medicine, University of California, San Diego, 3900 Fifth Avenue, Suite 310, San Diego, CA 92103; email jsallis@ucsd.edu.

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a. International Physical Activity Questionnaire, available at http://www.sdp.univ.fvg.it/sites/default/files/IPAQ_English_self-admin_long.pdf.

b. The Youth Risk Behavior Surveillance System is managed by the Centers for Disease Control and Prevention (CDC). Go to http://www.cdc.gov/HealthyYouth/yrbs/index.htm for more information.

c. For more information, go to http://www.thecommunityguide.org/


James F. Sallis James F. Sallis, PhD, is Distinguished Professor of Family Medicine and Public Health at the University of California, San Diego and Director of Active Living Research, a program of the Robert Wood Johnson Foundation. His primary research interests are promoting physical activity and understanding policy and environmental influences on physical activity, nutrition, and obesity. Time Magazine has identified Dr. Sallis as an "obesity warrior." He has authored over 600 scientific publications and is one of the world's most cited authors in the social sciences. Dr. Sallis is President-elect of the Society of Behavioral Medicine.
Jordan A. Carlson Jordan A. Carlson, PhD, MA, is Director of Community-Engaged Health Research, Children's Mercy Hospital, and Assistant Professor of Pediatrics, University of Missouri-Kansas City School of Medicine. His research interests include active living, school-based physical activity, neighborhood walkability, improving uptake and implementation of physical activity interventions, and physical activity measurement technology.

 

Page last reviewed July 2015
Page originally created September 2015
Internet Citation: Physical Activity: Numerous Benefits and Effective Interventions. Content last reviewed July 2015. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/professionals/education/curriculum-tools/population-health/sallis.html