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US Physical Activity Guidelines: Current state, impact and future directions
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US Physical Activity Guidelines: Current State, Impact and Future Directions Rajeev Singh MD, MBA , Anish Pattisapu MD , Michael S Emery MD, MS, FACC PII: DOI: Reference:
S1050-1738(19)30140-9 https://doi.org/10.1016/j.tcm.2019.10.002 TCM 6715
To appear in:
Trends in Cardiovascular Medicine
Please cite this article as: Rajeev Singh MD, MBA , Anish Pattisapu MD , Michael S Emery MD, MS, FACC , US Physical Activity Guidelines: Current State, Impact and Future Directions, Trends in Cardiovascular Medicine (2019), doi: https://doi.org/10.1016/j.tcm.2019.10.002
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Inc.
US Physical Activity Guidelines: Current State, Impact and Future Directions
Rajeev Singh MD, MBAa, Anish Pattisapu, MDa, Michael S. Emery MD, MS, FACCa,b
a
Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, Indiana.
b
Indiana University Health, Center for Cardiovascular Care in Athletics, Indianapolis, Indiana.
Michael S. Emery, MD, MS, FACC, Assistant Professor of Clinical Medicine, Krannert Institute of Cardiology, Indiana University School of Medicine, 1800 North Capital Avenue, E371, Indianapolis, IN 46202 [email protected]
Abstract Regular physical activity is one of the most powerful methods to lower the risk of all-cause mortality, help control multiple medical co-morbidities and improve overall quality of life. For optimal health it is recommended that adults obtain at least 150 minutes per week of moderate-intensity or 75 minutes per week of vigorous-intensity aerobic exercise per week along with at least 2 days of muscle-strengthening activity. Despite the known health benefits of exercise and long-standing recommendations from major health, medical and fitness societies, only half of Americans meet these guidelines. The Physical Activity Guidelines for Americans, 2nd edition from the U.S. Department of Health and Human Services provides an update from the 2008 guidelines adding specific recommendations for pre-school children while emphasizing the need to reduce sedentarism across the age spectrum (“move more and sit less”). This document provides a summary of the 2018 Physical Activity Guidelines for Americans as well as the impact of inactivity on health and future directions to improve utilization.
Keywords
Physical activity, guidelines, mortality, quality of life, exercise
Introduction The beneficial effects of physical activity on multiple facets of health have long been known (13). The updated Physical Activity Guidelines for Americans, 2nd edition (4) from the U.S. Department of Health and Human Services is the synthesis of decades of accumulated knowledge and understanding. This update of the 2008 Health improvement in the Physical Activity Guidelines (PAG) (5) continues to serve as the primary, authoritative statement from the US federal government for evidence-based guidance on physical activity, fitness and health. Evidence summarized shows decreased rates of morbidity and mortality in cardiovascular diseases, various cancers, improvement in brain health in all age ranges, obesity, decreased falls, benefits in pregnancy and peripartum, arthritis, and comorbid disease such as diabetes, hypertension, multiple sclerosis, etc. Since the last guidelines were published in 2008, there has been a tremendous increase in the understanding of the benefits of physical activity with the current update continuing to define easy to understand key concepts and definitions. The second edition was developed in collaboration with the Centers for Disease Control and Prevention, the National Institutes of Health, and the President’s Council on Sports, Fitness & Nutrition. The depth of knowledge in these documents is exemplified by the widely represented Physical Activity Guidelines Advisory Committee (6) of 17 core members divided into 9 subcommittees [Aging, Brain Health, Cancer – Primary Prevention, Cardiometabolic Health and Prevention of Weight Gain, Exposure, Individuals with Chronic Conditions, Promotions of Physical Activity, Sedentary Behavior, and Youth] and 3 work groups [Physical Fitness, Youth to Adult Transition, and Pregnancy and Postpartum] as well as outside experts, consultants, and support staff. The importance of this diversity is reflected by the inclusion of geographically varied institutions, different educational and professional backgrounds, as well as representatives from a wide range of associations and coalitions. Taken as a whole, these varied resources highlight the broad nature of physical activity counselling and delivery across all fields of health care and fitness.
Definitions Physical activity consists of any movement via skeletal muscle requiring energy expenditure. More specifically, exercise is defined as activity planned for the purpose of health and physical fitness. In essence, exercise is a subcategory of physical activity but not synonymous with it. Physical activities for the purpose of conditioning and/or sport are more consistent with exercise (i.e. physical fitness) whereas physical activities for the purpose of performing regular daily activities (e.g. occupation, household) are usually not performed with the intent of improving physical fitness (7). Exercise can be further differentiated into multiple types:
Aerobic: relating to cardiorespiratory or endurance activity
Anaerobic: higher levels of activity surpassing the usual oxygen-metabolic pathways
Muscle-strengthening: resistance training and weightlifting requiring muscular activation against an external object or bodyweight
Bone-strengthening: weight-bearing activities producing a force against the body
Balance: actively resisting forces that cause falls
In practicality, most physical activities involve some combination of the aforementioned stressors and it is notable that mortality is reduced regardless of which activities produce energy expenditure. Intensity, duration and frequency are key components relating exercise type to the overall concept of dose. Intensity of exercise is typically quantified in terms of the metabolic cost of a particular activity. Absolute intensity is commonly represented in METs (metabolic equivalent of task). 1 MET (3.5 ml/kg/min of oxygen consumption) is considered the resting metabolic rate for sitting quietly while awake. A common schema differentiates activities into vigorous-intensity (6 or more METs), moderateintensity (3 METs to less than 6 METs), light-intensity (1.6 METs to less than 3 METs), and sedentary behavior (less than 1.5 METs) (Table 1). Relative intensity relates the intensity of activity to the patient’s own functional status or the individual’s level of effort during the activity. Relative intensity accounts for differences in fitness, age, and comorbidities between individuals. For example, the same absolute
intensity (e.g. 4 METs) may represent a maximal effort for one individual with cardiovascular disease but be relatively light for someone in good health. Duration and frequency are inter-related concepts of exercise quantification. Duration refers to the total time accumulated in a single bout or session of exercise. Frequency captures the number of exercise sessions over a defined period of time such as weeks or months. The duration and frequency when taken together are often represented in the literature as hours/week. Dose (incorporating frequency, duration and intensity as well as type of activity) and volume (dose over a longer period of time) are important in discussing physical activity. When measuring absolute exercise intensity, the total dose is the combination of METs, duration and frequency and is often expressed as MET-hours/week or MET-minutes/week. These factors allow clinicians and researchers to better quantify the importance of achieving recommended physical activity goals in relation to all-cause mortality and morbidity benefits across multiple disease domains and well-being indices. When interpreting the guidelines, it is important to understand the rationale and definition used for their “strength of the evidence” which is based on the type of evidence (randomized controlled trials, meta-analyses, non-randomized trials, observational studies, etc.) as well as the number of studies. Strong indicates consistent results across studies and populations. Moderate or reasonable corresponds to reasonably consistent studies. Weak or limited means inconsistent results across studies and populations. Prior Guidelines The 1st edition of the Physical Activity Guidelines for Americans was released in 2008 (5). The 2008 PA Guidelines coalesced the health benefits of physical activity for children/adolescents, adults across the age spectrum including those with chronic disease, pregnancy/postpartum, and adults with disabilities. An initial key theme was to avoid inactivity with some physical activity being better than none. The clear message was that regular physical activity over time results in long-term health benefits. For substantial health benefits, the 2008 PAGs recommended aerobic exercise of at least 150 minutes a week of moderate-intensity, 75 minute of vigorous-intensity (Table 1) or an equivalent combination in adults with “bouts” lasting a minimum of 10 minutes. Adults were also recommended to do muscle
strengthening involving all major muscle groups at least twice a week (Table 1). Children and adolescents were recommended to accumulate 60 minutes or more or physical activity with most being aerobic exercise of moderate- or vigorous-intensity (vigorous at least three times a week) in addition to musclestrengthening and bone-strengthening at least three times a week. Unfortunately, the uptake of the 2008 PAGs did not have the broad-reaching impact that health officials would have expected. National survey data from 2009 revealed that only ~36% of US adults were even aware of these PAGs with less than 1% having knowledge of the moderate-intensity activity recommendations (8). Data in adolescents were also discouraging with data showing less than 20% engaging in recommended levels of both aerobic and strength training activities and almost 50% meeting neither guideline (9). Sedentary behaviors (e.g. prolonged sitting such as television or video watching of 2 hours or more per day) after the introduction of the 2008 PAGs were quite high with data from the National Health and Nutrition Examination Survey (NHANES) showing prevalence rates of 62% in children, 59% in adolescents, 65% in adults and 84% in older adults 65 years (10). Over the observed time period only children demonstrated a significant, albeit small, reduction in prolonged sitting (-3.4%) with increased sedentary trends in older adults (+3.5%). In 2017, the Center for Disease Control and Prevention (CDC) using the Behavioral Risk Factor Surveillance System survey reported that 26.6% of responding adults do not engage in leisure-time physical activity(11). Similarly, only a little more than half (54%) sufficiently met the aerobic guidelines laid out in the 2008 Physical Activity Guidelines for Americans (150 minutes/week of moderate intensity or 75 minutes/week of vigorous intensity exercise) in the 2017 National Health Interview Survey (NHIS) data (12). A separate analysis from the NHANES data showed that adherence rates to the recommended activity level of 150 minutes of moderate or 75 minutes of vigorous activity in adults from 2007-2008 to 2015-2016 did not significantly change over time but time spent in sedentary behavior significantly increased by approximately 40 minutes per day (13). This is particularly concerning as modifiable risk factors such as the rate of adult and childhood obesity continue to increase in the United States (Figure 1) with the prevalence of adult obesity at 39.8% in 2015-2016 (14).
2018 Guidelines, What’s new With the 2nd edition of the Physical Activity Guidelines for Americans, the committee continues to underscore the strong evidence of physical activity on health benefits across the age spectrum. Several changes are introduced compared to the 2008 PA Guidelines which is highlighted by the addition of recommendations for preschool-aged children and the emphasis on shifting behavior from sitting to being more active for everyone (see Table 2). The target level of 150-300 minutes of moderate intensity physical activity (500-1,000 MET) per week in adults for optimal health is continually reinforced. However, it is understood that many do not achieve the goal levels for optimal health. The new guidelines now highlight even light-intensity physical activity and its impact on reduced all-cause mortality with any amount and length (bouts) of exercise having a beneficial impact on overall health. The 2008 PA Guidelines for adults had previously recommended that any bout of physical activity be performed for a minimum of 10 minutes. When comparing continuous versus accumulative exercise, a meta-analysis of 19 studies by Murphy et al. found no differences in terms of cardiorespiratory fitness, blood pressure, as well as a majority of biomarkers (15). With the elimination of this minimum time-limit, the committee is striving to decrease sedentary behavior by highlighting the immediate effects of physical activity such as reduced anxiety and blood pressure as well as improved sleep, cognitive function and insulin sensitivity. The Physical Activity Guidelines Advisory Committee (PAGAC) Grade was Strong for showing strong evidence of greater sedentary behavior related to higher all-cause mortality, diabetes, cardiovascular events and varying with amount of moderate-vigorous intensity physical activity as well as positive perception of quality of life. In addition, PAGAC Grade was Moderate for sedentary behavior linked to endometrial, colon and lung cancers. Recommendations for school-aged children and adolescents were available in the 2008 version. The new guidelines now include support of physical activity starting in pre-school children age 3 and older which include improvement in bone health and weight. While no specific dose is defined, it is recommended that this group accumulate 3 hours per day of activities of any intensity including
structured activities to promote movement. School-aged and adolescents are recommended 60 minutes a day of moderate-to-vigorous intensity physical activity with specific emphasis also noted on performing bone-strengthening activities at least 3 days a week and muscle-strengthening at least 3 days a week. It is stressed that parents and other adults, including healthcare providers, are a vital component to promoting physical activity to this younger age group with encouragement of participation in a variety of activity types and finding age-appropriate opportunities to do so. For older adults, the guidelines are similar to adults in terms of dose (intensity and duration). However, it is understood older adults have more chronic conditions and relative-intensity now plays a vital role. In addition, a multicomponent approach should be considered. PAGAC Grade Strong for targeted physical activity levels in fall prevention (30-40% risk reduction) and trauma related to falls as well as improving physical function. It is mentioned more research is needed to evaluate yoga, tai chi, qigong, dance and active video gaming (ie. using Nintendo Wii Fit PlusTM) in older adults as well as doseresponse effect for chronic comorbidities such as chronic obstructive pulmonary disease and Parkinson’s Disease (16). PAGAC graded Strong for improved cognition, attention, memory in all ages but particular note is made for older adults with Strong evidence for reduced risk of Alzheimer’s Disease and cognitive impairment and Moderate evidence in improving cognitive impairment in dementia. In relation to pregnancy and the peripartum period, PAGAC grade was Strong for evidence of inverse relationship of both gestational diabetes mellitus and postpartum depression. Limited evidence noted for depression and anxiety during pregnancy and Limited evidence with regard to preeclampsia. Target levels are similar to adults with at least 150 minutes of moderate-intensity aerobic activity a week. It is important to note that adults previously very active can continue to be physically active. Adults with chronic health conditions and adults with disabilities have similar target levels of physical activity as adults with a notion of performing muscle-strengthening activities involving all major muscle groups at least twice a week. In addition, relative-intensity again plays a factor and the guidelines promote avoiding inactivity and consulting with his or her healthcare provider as well.
Cost of Healthcare from Inactivity Inadequate physical activity results in marked increases in healthcare costs. A study by Carlson et al. merged data from the NHIS from 2004-2010 with Medical Expenditure Panel Survey (MEPS) from 2006-2011 and showed an estimated 11.1% aggregate of health care expenditures after adjusting body mass index (BMI) related to inadequate physical activity (17). This study also showed a BMI adjusted mean difference of $1,313 expenditure per capita inactive to active and $576 insufficiently active to active as well as an estimated $117 billion (C.I. $76 billion - $158 billion) per year expenditure related to inadequate physical levels. Globally, it was estimated that $67.5 billion was spent in health-care expenditure and productivity losses related to five major noncommunicable diseases and all-cause mortality in 2013 (18). Using MEPS data for 2012-2013, Salami and colleagues estimated an average additional annual pharmaceutical expenditure of $519 per adult related to inadequate physical activity – not including additional expenditures for other comorbidities (19). Exercise at the Extremes Data compiled from multiple studies by the scientific committee for the 2008 Physical Activities Guidelines demonstrated that at least 2 to 2.5 hours a week of moderate-intensity physical activity is sufficient to significantly lower all-cause mortality (5). However, even small amounts of physical activity are beneficial and the described relationship between physical activity and outcomes is curvilinear with the largest gains yielded from an inactive to a mild or moderately active lifestyle (Figure 2) (20, 21). A 20% reduction in all-cause mortality has been observed with just 1.5 hours per week of moderate-tovigorous activity whereas to reduce mortality another 20% requires an additional 5.5 hours of activity (5). Even the transition from sitting behaviors to any activity has been shown to decrease all-cause and cardiovascular mortality (22). Stamatakis et al. reported that among 149,077 participants with an 8.9-year median follow-up, one of the main determinants to all-cause mortality was sedentarism (sitting ≥8 hours/day) with a dose-response manner to sitting time in the least active groups (23). Comparatively Xu et al. used uncompensated sedentary metabolic equivalent hours (USMh as 1 MET/h) to relate all-cause mortality by accounting for sitting hours and negating the amount of MET equivalents per hour
performed of physical activity (24). They concluded that sitting in excess of 7 MET-hour per day with subtraction of physical activity MET/h had independent association to all-cause mortality. Subsequently, public health campaigns have used the phrase “move more and sit less” in order to promote the concept that any amount of physical activity is better than none (25-27). On the opposite end of the spectrum, there has been considerable debate and controversy about the extreme ranges of physical activity that well exceeds the current physical activity guidelines (28-30). Eijsvogels and colleagues analyzed previous trials and found that there was no further reduction in cardiovascular disease mortality with vigorous activity beyond 11 MET-h/week however moderateintensity physical activity showed further reductions in cardiovascular disease mortality beyond recommended levels with no clear evidence of an upper limit. (20). Wasfy et al. demonstrated similar results in their analysis and found that high dose exercise is still associated with lower mortality than sedentarism with some flattening of the curve beyond the current optimal recommended dose (31). The largest published cohort (661,137 subjects from 6 pooled studies) demonstrated an upper threshold for mortality at 3-5 times the current physical activity guidelines but no harm at levels 10 or more times the recommended minimum (32). Future Directions In 2019, the American College of Cardiology (ACC) and American Heart Association (AHA) published Guidelines of the Primary Prevention of Cardiovascular Disease (33). The dose of physical activity recommended (class I recommendation) of at least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic physical activity for adults to reduce atherosclerotic cardiovascular disease is the same as the PA Guidelines. Additionally, the ACC/AHA Guidelines emphasize that primary prevention as a multifaceted and team-based approach will have the biggest impact on overall prevention of cardiovascular disease in the future (Figure 3). Scientific publications and guidelines have been crucial to understanding and synthesizing the beneficial effects of physical activity. While this is laudable, ultimately the key to improving health outcomes is figuring out a way to get people to actually “move more and sit less.” We must find actual
ways to incentivize people or to get them to come to the reality that this is how they are best going to improve their health, longevity and quality of life. No one owns “fitness” and healthcare providers, employers, government agencies, insurance companies, fitness professionals/societies, etc. need to provide the population with straightforward and accessible resources with low barriers of entry and adequate support. This is about health, and while it is a business, that business should not exclude others providing valuable resources that may have a model different from their own. Conclusions The Physical Activity Guidelines for Americans, 2nd edition has a very important role in promoting physical activity and thereby translating to reductions in morbidity and mortality. The costs, both financial and quality of life, from sedentary behaviors and suboptimal physical activity are substantial. The new guidelines promote physical activity of any amount as it translates to risk reduction despite not hitting target goals: “move more and sit less.” As continued research accrues, more and more evidence will be presented as well as understanding the benefits in many other areas of health. Healthcare providers play a pivotal role to provide counseling, share the trends of the current healthcare field, promote activity and connect patients to appropriate resources to improve outcomes. Declaration of Competing Interest: None
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Table 1: Examples of Moderate- and Vigorous-Intensity Activity as well as Muscle-Strengthening Activity to Meet 2018 Physical Activity Guidelines [adapted from Centers for Disease Control and Prevention (34)] Moderate-intensity aerobic
Vigorous-intensity aerobic
Muscle-strengthening activities
activities (>150 min/week)
activities (> 75 min/week)
(at least 2 days/week working all major muscle groups)
Brisk walking (>3 miles/hour)
Hiking uphill, race walking,
Weight lifting
jogging/running Water aerobics
Swimming laps
Resistance bands
Bicycle riding (<10 miles/hr)
Bicycle riding (>10 miles/hr)
Body weight exercises (pushups, pull-ups, sit-ups)
Tennis (doubles)
Tennis (Singles)
Ballroom dancing
Aerobic dancing
General gardening
Heaving gardening (digging, hoeing)
Table 2: Top 10 Things to Know about the Second Edition of the Physical Activity Guidelines for Americans [adapted from Office of Disease Prevention and Health Promotion (35)] 1. The 2nd edition of the Physical Activity Guidelines for Americans provides evidence-based recommendations with new guidelines for children ages 3-5 and updated guidelines for youth ages 6-17, adults of all ages, women during pregnancy/post-partum and adults with disabilities and chronic health conditions 2. New guidelines for children ages 3-5 recommend activity throughout the day by encouraging active play to enhance growth and development for at least 3 hours per day. 3. Youths 6-17 years should obtain at least 60 minutes of moderate-to-vigorous physical activity per day to include aerobic as well as those activities that lead to muscle and bone strengthening. 4. The recommended amount of physical activity for adults remains the same as the previous edition: at least 150 minutes of moderate- or 75 minutes of vigorous-intensity activity with at least 2 days of muscle-strengthening activity per week (see Table 1). 5. Physical activity has multiple health benefits independent of other healthy behaviors such as nutrition. 6. All physical activity can help offset the risks of multiple comorbidities (heart disease, hypertension, all-cause mortality, etc) many of which are linked to sedentarism. “Move more and sit less.” 7. “Any amount of physical activity has some health benefits.” The 2nd edition of the Physical Activity Guidelines removes the prior recommendation of a minimum of 10-minute bouts of exercise in order to promote Americans to move more frequently. 8. Physical activity has immediate health benefits. 9. Meeting the Physical Activity Guidelines consistently has the biggest long-term health benefits. Newly established benefits from the 2008 Physical Activity Guidelines includes
cognition in youth, prevention of multiple cancers, decreased risk of dementia, lower risk of falls and injuries from falls, gestational diabetes, postpartum depression and risk of excessive weight gain for all groups. 10. Many chronic medical conditions including osteoarthritis, hypertension, type 2 diabetes, anxiety/depression, dementia, ADHD, Parkinson’s disease and others can be managed more effectively with physical activity with reduced risk of all-cause mortality and improved quality of life.
Figure 1: Trends in obesity prevalence among adults ages 20 and over (age adjusted) and youth aged 2-19 years: Unites States, 1999-2000 through 2015-2016. [reproduced from Hales et al. (14)]
1
Significant increasing linear trend for both adults and youth from 1999-2000 through 2015-2016
Figure 2: The Curvilinear Relationship Between Physical Activity and Cardiovascular Risk. A similar increase in physical activity yields different risk reductions across the activity spectrum. Physical inactivity is associated with the highest risk, whereas high aerobic exercise volumes are associated with the lowest risk. [reproduced from Eijsvogels et al. (20)]
Figure 3: The multifaceted and team-based approach to the primary prevention of cardiovascular disease [reproduced from Arnett et al. (33)]
US Physical Activity Guidelines: Current State, Impact and Future Directions Rajeev Singh MD, MBA , Anish Pattisapu MD , Michael S Emery MD, MS, FACC PII: DOI: Reference:
S1050-1738(19)30140-9 https://doi.org/10.1016/j.tcm.2019.10.002 TCM 6715
To appear in:
Trends in Cardiovascular Medicine
Please cite this article as: Rajeev Singh MD, MBA , Anish Pattisapu MD , Michael S Emery MD, MS, FACC , US Physical Activity Guidelines: Current State, Impact and Future Directions, Trends in Cardiovascular Medicine (2019), doi: https://doi.org/10.1016/j.tcm.2019.10.002
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Inc.
US Physical Activity Guidelines: Current State, Impact and Future Directions
Rajeev Singh MD, MBAa, Anish Pattisapu, MDa, Michael S. Emery MD, MS, FACCa,b
a
Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, Indiana.
b
Indiana University Health, Center for Cardiovascular Care in Athletics, Indianapolis, Indiana.
Michael S. Emery, MD, MS, FACC, Assistant Professor of Clinical Medicine, Krannert Institute of Cardiology, Indiana University School of Medicine, 1800 North Capital Avenue, E371, Indianapolis, IN 46202 [email protected]
Abstract Regular physical activity is one of the most powerful methods to lower the risk of all-cause mortality, help control multiple medical co-morbidities and improve overall quality of life. For optimal health it is recommended that adults obtain at least 150 minutes per week of moderate-intensity or 75 minutes per week of vigorous-intensity aerobic exercise per week along with at least 2 days of muscle-strengthening activity. Despite the known health benefits of exercise and long-standing recommendations from major health, medical and fitness societies, only half of Americans meet these guidelines. The Physical Activity Guidelines for Americans, 2nd edition from the U.S. Department of Health and Human Services provides an update from the 2008 guidelines adding specific recommendations for pre-school children while emphasizing the need to reduce sedentarism across the age spectrum (“move more and sit less”). This document provides a summary of the 2018 Physical Activity Guidelines for Americans as well as the impact of inactivity on health and future directions to improve utilization.
Keywords
Physical activity, guidelines, mortality, quality of life, exercise
Introduction The beneficial effects of physical activity on multiple facets of health have long been known (13). The updated Physical Activity Guidelines for Americans, 2nd edition (4) from the U.S. Department of Health and Human Services is the synthesis of decades of accumulated knowledge and understanding. This update of the 2008 Health improvement in the Physical Activity Guidelines (PAG) (5) continues to serve as the primary, authoritative statement from the US federal government for evidence-based guidance on physical activity, fitness and health. Evidence summarized shows decreased rates of morbidity and mortality in cardiovascular diseases, various cancers, improvement in brain health in all age ranges, obesity, decreased falls, benefits in pregnancy and peripartum, arthritis, and comorbid disease such as diabetes, hypertension, multiple sclerosis, etc. Since the last guidelines were published in 2008, there has been a tremendous increase in the understanding of the benefits of physical activity with the current update continuing to define easy to understand key concepts and definitions. The second edition was developed in collaboration with the Centers for Disease Control and Prevention, the National Institutes of Health, and the President’s Council on Sports, Fitness & Nutrition. The depth of knowledge in these documents is exemplified by the widely represented Physical Activity Guidelines Advisory Committee (6) of 17 core members divided into 9 subcommittees [Aging, Brain Health, Cancer – Primary Prevention, Cardiometabolic Health and Prevention of Weight Gain, Exposure, Individuals with Chronic Conditions, Promotions of Physical Activity, Sedentary Behavior, and Youth] and 3 work groups [Physical Fitness, Youth to Adult Transition, and Pregnancy and Postpartum] as well as outside experts, consultants, and support staff. The importance of this diversity is reflected by the inclusion of geographically varied institutions, different educational and professional backgrounds, as well as representatives from a wide range of associations and coalitions. Taken as a whole, these varied resources highlight the broad nature of physical activity counselling and delivery across all fields of health care and fitness.
Definitions Physical activity consists of any movement via skeletal muscle requiring energy expenditure. More specifically, exercise is defined as activity planned for the purpose of health and physical fitness. In essence, exercise is a subcategory of physical activity but not synonymous with it. Physical activities for the purpose of conditioning and/or sport are more consistent with exercise (i.e. physical fitness) whereas physical activities for the purpose of performing regular daily activities (e.g. occupation, household) are usually not performed with the intent of improving physical fitness (7). Exercise can be further differentiated into multiple types:
Aerobic: relating to cardiorespiratory or endurance activity
Anaerobic: higher levels of activity surpassing the usual oxygen-metabolic pathways
Muscle-strengthening: resistance training and weightlifting requiring muscular activation against an external object or bodyweight
Bone-strengthening: weight-bearing activities producing a force against the body
Balance: actively resisting forces that cause falls
In practicality, most physical activities involve some combination of the aforementioned stressors and it is notable that mortality is reduced regardless of which activities produce energy expenditure. Intensity, duration and frequency are key components relating exercise type to the overall concept of dose. Intensity of exercise is typically quantified in terms of the metabolic cost of a particular activity. Absolute intensity is commonly represented in METs (metabolic equivalent of task). 1 MET (3.5 ml/kg/min of oxygen consumption) is considered the resting metabolic rate for sitting quietly while awake. A common schema differentiates activities into vigorous-intensity (6 or more METs), moderateintensity (3 METs to less than 6 METs), light-intensity (1.6 METs to less than 3 METs), and sedentary behavior (less than 1.5 METs) (Table 1). Relative intensity relates the intensity of activity to the patient’s own functional status or the individual’s level of effort during the activity. Relative intensity accounts for differences in fitness, age, and comorbidities between individuals. For example, the same absolute
intensity (e.g. 4 METs) may represent a maximal effort for one individual with cardiovascular disease but be relatively light for someone in good health. Duration and frequency are inter-related concepts of exercise quantification. Duration refers to the total time accumulated in a single bout or session of exercise. Frequency captures the number of exercise sessions over a defined period of time such as weeks or months. The duration and frequency when taken together are often represented in the literature as hours/week. Dose (incorporating frequency, duration and intensity as well as type of activity) and volume (dose over a longer period of time) are important in discussing physical activity. When measuring absolute exercise intensity, the total dose is the combination of METs, duration and frequency and is often expressed as MET-hours/week or MET-minutes/week. These factors allow clinicians and researchers to better quantify the importance of achieving recommended physical activity goals in relation to all-cause mortality and morbidity benefits across multiple disease domains and well-being indices. When interpreting the guidelines, it is important to understand the rationale and definition used for their “strength of the evidence” which is based on the type of evidence (randomized controlled trials, meta-analyses, non-randomized trials, observational studies, etc.) as well as the number of studies. Strong indicates consistent results across studies and populations. Moderate or reasonable corresponds to reasonably consistent studies. Weak or limited means inconsistent results across studies and populations. Prior Guidelines The 1st edition of the Physical Activity Guidelines for Americans was released in 2008 (5). The 2008 PA Guidelines coalesced the health benefits of physical activity for children/adolescents, adults across the age spectrum including those with chronic disease, pregnancy/postpartum, and adults with disabilities. An initial key theme was to avoid inactivity with some physical activity being better than none. The clear message was that regular physical activity over time results in long-term health benefits. For substantial health benefits, the 2008 PAGs recommended aerobic exercise of at least 150 minutes a week of moderate-intensity, 75 minute of vigorous-intensity (Table 1) or an equivalent combination in adults with “bouts” lasting a minimum of 10 minutes. Adults were also recommended to do muscle
strengthening involving all major muscle groups at least twice a week (Table 1). Children and adolescents were recommended to accumulate 60 minutes or more or physical activity with most being aerobic exercise of moderate- or vigorous-intensity (vigorous at least three times a week) in addition to musclestrengthening and bone-strengthening at least three times a week. Unfortunately, the uptake of the 2008 PAGs did not have the broad-reaching impact that health officials would have expected. National survey data from 2009 revealed that only ~36% of US adults were even aware of these PAGs with less than 1% having knowledge of the moderate-intensity activity recommendations (8). Data in adolescents were also discouraging with data showing less than 20% engaging in recommended levels of both aerobic and strength training activities and almost 50% meeting neither guideline (9). Sedentary behaviors (e.g. prolonged sitting such as television or video watching of 2 hours or more per day) after the introduction of the 2008 PAGs were quite high with data from the National Health and Nutrition Examination Survey (NHANES) showing prevalence rates of 62% in children, 59% in adolescents, 65% in adults and 84% in older adults 65 years (10). Over the observed time period only children demonstrated a significant, albeit small, reduction in prolonged sitting (-3.4%) with increased sedentary trends in older adults (+3.5%). In 2017, the Center for Disease Control and Prevention (CDC) using the Behavioral Risk Factor Surveillance System survey reported that 26.6% of responding adults do not engage in leisure-time physical activity(11). Similarly, only a little more than half (54%) sufficiently met the aerobic guidelines laid out in the 2008 Physical Activity Guidelines for Americans (150 minutes/week of moderate intensity or 75 minutes/week of vigorous intensity exercise) in the 2017 National Health Interview Survey (NHIS) data (12). A separate analysis from the NHANES data showed that adherence rates to the recommended activity level of 150 minutes of moderate or 75 minutes of vigorous activity in adults from 2007-2008 to 2015-2016 did not significantly change over time but time spent in sedentary behavior significantly increased by approximately 40 minutes per day (13). This is particularly concerning as modifiable risk factors such as the rate of adult and childhood obesity continue to increase in the United States (Figure 1) with the prevalence of adult obesity at 39.8% in 2015-2016 (14).
2018 Guidelines, What’s new With the 2nd edition of the Physical Activity Guidelines for Americans, the committee continues to underscore the strong evidence of physical activity on health benefits across the age spectrum. Several changes are introduced compared to the 2008 PA Guidelines which is highlighted by the addition of recommendations for preschool-aged children and the emphasis on shifting behavior from sitting to being more active for everyone (see Table 2). The target level of 150-300 minutes of moderate intensity physical activity (500-1,000 MET) per week in adults for optimal health is continually reinforced. However, it is understood that many do not achieve the goal levels for optimal health. The new guidelines now highlight even light-intensity physical activity and its impact on reduced all-cause mortality with any amount and length (bouts) of exercise having a beneficial impact on overall health. The 2008 PA Guidelines for adults had previously recommended that any bout of physical activity be performed for a minimum of 10 minutes. When comparing continuous versus accumulative exercise, a meta-analysis of 19 studies by Murphy et al. found no differences in terms of cardiorespiratory fitness, blood pressure, as well as a majority of biomarkers (15). With the elimination of this minimum time-limit, the committee is striving to decrease sedentary behavior by highlighting the immediate effects of physical activity such as reduced anxiety and blood pressure as well as improved sleep, cognitive function and insulin sensitivity. The Physical Activity Guidelines Advisory Committee (PAGAC) Grade was Strong for showing strong evidence of greater sedentary behavior related to higher all-cause mortality, diabetes, cardiovascular events and varying with amount of moderate-vigorous intensity physical activity as well as positive perception of quality of life. In addition, PAGAC Grade was Moderate for sedentary behavior linked to endometrial, colon and lung cancers. Recommendations for school-aged children and adolescents were available in the 2008 version. The new guidelines now include support of physical activity starting in pre-school children age 3 and older which include improvement in bone health and weight. While no specific dose is defined, it is recommended that this group accumulate 3 hours per day of activities of any intensity including
structured activities to promote movement. School-aged and adolescents are recommended 60 minutes a day of moderate-to-vigorous intensity physical activity with specific emphasis also noted on performing bone-strengthening activities at least 3 days a week and muscle-strengthening at least 3 days a week. It is stressed that parents and other adults, including healthcare providers, are a vital component to promoting physical activity to this younger age group with encouragement of participation in a variety of activity types and finding age-appropriate opportunities to do so. For older adults, the guidelines are similar to adults in terms of dose (intensity and duration). However, it is understood older adults have more chronic conditions and relative-intensity now plays a vital role. In addition, a multicomponent approach should be considered. PAGAC Grade Strong for targeted physical activity levels in fall prevention (30-40% risk reduction) and trauma related to falls as well as improving physical function. It is mentioned more research is needed to evaluate yoga, tai chi, qigong, dance and active video gaming (ie. using Nintendo Wii Fit PlusTM) in older adults as well as doseresponse effect for chronic comorbidities such as chronic obstructive pulmonary disease and Parkinson’s Disease (16). PAGAC graded Strong for improved cognition, attention, memory in all ages but particular note is made for older adults with Strong evidence for reduced risk of Alzheimer’s Disease and cognitive impairment and Moderate evidence in improving cognitive impairment in dementia. In relation to pregnancy and the peripartum period, PAGAC grade was Strong for evidence of inverse relationship of both gestational diabetes mellitus and postpartum depression. Limited evidence noted for depression and anxiety during pregnancy and Limited evidence with regard to preeclampsia. Target levels are similar to adults with at least 150 minutes of moderate-intensity aerobic activity a week. It is important to note that adults previously very active can continue to be physically active. Adults with chronic health conditions and adults with disabilities have similar target levels of physical activity as adults with a notion of performing muscle-strengthening activities involving all major muscle groups at least twice a week. In addition, relative-intensity again plays a factor and the guidelines promote avoiding inactivity and consulting with his or her healthcare provider as well.
Cost of Healthcare from Inactivity Inadequate physical activity results in marked increases in healthcare costs. A study by Carlson et al. merged data from the NHIS from 2004-2010 with Medical Expenditure Panel Survey (MEPS) from 2006-2011 and showed an estimated 11.1% aggregate of health care expenditures after adjusting body mass index (BMI) related to inadequate physical activity (17). This study also showed a BMI adjusted mean difference of $1,313 expenditure per capita inactive to active and $576 insufficiently active to active as well as an estimated $117 billion (C.I. $76 billion - $158 billion) per year expenditure related to inadequate physical levels. Globally, it was estimated that $67.5 billion was spent in health-care expenditure and productivity losses related to five major noncommunicable diseases and all-cause mortality in 2013 (18). Using MEPS data for 2012-2013, Salami and colleagues estimated an average additional annual pharmaceutical expenditure of $519 per adult related to inadequate physical activity – not including additional expenditures for other comorbidities (19). Exercise at the Extremes Data compiled from multiple studies by the scientific committee for the 2008 Physical Activities Guidelines demonstrated that at least 2 to 2.5 hours a week of moderate-intensity physical activity is sufficient to significantly lower all-cause mortality (5). However, even small amounts of physical activity are beneficial and the described relationship between physical activity and outcomes is curvilinear with the largest gains yielded from an inactive to a mild or moderately active lifestyle (Figure 2) (20, 21). A 20% reduction in all-cause mortality has been observed with just 1.5 hours per week of moderate-tovigorous activity whereas to reduce mortality another 20% requires an additional 5.5 hours of activity (5). Even the transition from sitting behaviors to any activity has been shown to decrease all-cause and cardiovascular mortality (22). Stamatakis et al. reported that among 149,077 participants with an 8.9-year median follow-up, one of the main determinants to all-cause mortality was sedentarism (sitting ≥8 hours/day) with a dose-response manner to sitting time in the least active groups (23). Comparatively Xu et al. used uncompensated sedentary metabolic equivalent hours (USMh as 1 MET/h) to relate all-cause mortality by accounting for sitting hours and negating the amount of MET equivalents per hour
performed of physical activity (24). They concluded that sitting in excess of 7 MET-hour per day with subtraction of physical activity MET/h had independent association to all-cause mortality. Subsequently, public health campaigns have used the phrase “move more and sit less” in order to promote the concept that any amount of physical activity is better than none (25-27). On the opposite end of the spectrum, there has been considerable debate and controversy about the extreme ranges of physical activity that well exceeds the current physical activity guidelines (28-30). Eijsvogels and colleagues analyzed previous trials and found that there was no further reduction in cardiovascular disease mortality with vigorous activity beyond 11 MET-h/week however moderateintensity physical activity showed further reductions in cardiovascular disease mortality beyond recommended levels with no clear evidence of an upper limit. (20). Wasfy et al. demonstrated similar results in their analysis and found that high dose exercise is still associated with lower mortality than sedentarism with some flattening of the curve beyond the current optimal recommended dose (31). The largest published cohort (661,137 subjects from 6 pooled studies) demonstrated an upper threshold for mortality at 3-5 times the current physical activity guidelines but no harm at levels 10 or more times the recommended minimum (32). Future Directions In 2019, the American College of Cardiology (ACC) and American Heart Association (AHA) published Guidelines of the Primary Prevention of Cardiovascular Disease (33). The dose of physical activity recommended (class I recommendation) of at least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic physical activity for adults to reduce atherosclerotic cardiovascular disease is the same as the PA Guidelines. Additionally, the ACC/AHA Guidelines emphasize that primary prevention as a multifaceted and team-based approach will have the biggest impact on overall prevention of cardiovascular disease in the future (Figure 3). Scientific publications and guidelines have been crucial to understanding and synthesizing the beneficial effects of physical activity. While this is laudable, ultimately the key to improving health outcomes is figuring out a way to get people to actually “move more and sit less.” We must find actual
ways to incentivize people or to get them to come to the reality that this is how they are best going to improve their health, longevity and quality of life. No one owns “fitness” and healthcare providers, employers, government agencies, insurance companies, fitness professionals/societies, etc. need to provide the population with straightforward and accessible resources with low barriers of entry and adequate support. This is about health, and while it is a business, that business should not exclude others providing valuable resources that may have a model different from their own. Conclusions The Physical Activity Guidelines for Americans, 2nd edition has a very important role in promoting physical activity and thereby translating to reductions in morbidity and mortality. The costs, both financial and quality of life, from sedentary behaviors and suboptimal physical activity are substantial. The new guidelines promote physical activity of any amount as it translates to risk reduction despite not hitting target goals: “move more and sit less.” As continued research accrues, more and more evidence will be presented as well as understanding the benefits in many other areas of health. Healthcare providers play a pivotal role to provide counseling, share the trends of the current healthcare field, promote activity and connect patients to appropriate resources to improve outcomes. Declaration of Competing Interest: None
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Table 1: Examples of Moderate- and Vigorous-Intensity Activity as well as Muscle-Strengthening Activity to Meet 2018 Physical Activity Guidelines [adapted from Centers for Disease Control and Prevention (34)] Moderate-intensity aerobic
Vigorous-intensity aerobic
Muscle-strengthening activities
activities (>150 min/week)
activities (> 75 min/week)
(at least 2 days/week working all major muscle groups)
Brisk walking (>3 miles/hour)
Hiking uphill, race walking,
Weight lifting
jogging/running Water aerobics
Swimming laps
Resistance bands
Bicycle riding (<10 miles/hr)
Bicycle riding (>10 miles/hr)
Body weight exercises (pushups, pull-ups, sit-ups)
Tennis (doubles)
Tennis (Singles)
Ballroom dancing
Aerobic dancing
General gardening
Heaving gardening (digging, hoeing)
Table 2: Top 10 Things to Know about the Second Edition of the Physical Activity Guidelines for Americans [adapted from Office of Disease Prevention and Health Promotion (35)] 1. The 2nd edition of the Physical Activity Guidelines for Americans provides evidence-based recommendations with new guidelines for children ages 3-5 and updated guidelines for youth ages 6-17, adults of all ages, women during pregnancy/post-partum and adults with disabilities and chronic health conditions 2. New guidelines for children ages 3-5 recommend activity throughout the day by encouraging active play to enhance growth and development for at least 3 hours per day. 3. Youths 6-17 years should obtain at least 60 minutes of moderate-to-vigorous physical activity per day to include aerobic as well as those activities that lead to muscle and bone strengthening. 4. The recommended amount of physical activity for adults remains the same as the previous edition: at least 150 minutes of moderate- or 75 minutes of vigorous-intensity activity with at least 2 days of muscle-strengthening activity per week (see Table 1). 5. Physical activity has multiple health benefits independent of other healthy behaviors such as nutrition. 6. All physical activity can help offset the risks of multiple comorbidities (heart disease, hypertension, all-cause mortality, etc) many of which are linked to sedentarism. “Move more and sit less.” 7. “Any amount of physical activity has some health benefits.” The 2nd edition of the Physical Activity Guidelines removes the prior recommendation of a minimum of 10-minute bouts of exercise in order to promote Americans to move more frequently. 8. Physical activity has immediate health benefits. 9. Meeting the Physical Activity Guidelines consistently has the biggest long-term health benefits. Newly established benefits from the 2008 Physical Activity Guidelines includes
cognition in youth, prevention of multiple cancers, decreased risk of dementia, lower risk of falls and injuries from falls, gestational diabetes, postpartum depression and risk of excessive weight gain for all groups. 10. Many chronic medical conditions including osteoarthritis, hypertension, type 2 diabetes, anxiety/depression, dementia, ADHD, Parkinson’s disease and others can be managed more effectively with physical activity with reduced risk of all-cause mortality and improved quality of life.
Figure 1: Trends in obesity prevalence among adults ages 20 and over (age adjusted) and youth aged 2-19 years: Unites States, 1999-2000 through 2015-2016. [reproduced from Hales et al. (14)]
1
Significant increasing linear trend for both adults and youth from 1999-2000 through 2015-2016
Figure 2: The Curvilinear Relationship Between Physical Activity and Cardiovascular Risk. A similar increase in physical activity yields different risk reductions across the activity spectrum. Physical inactivity is associated with the highest risk, whereas high aerobic exercise volumes are associated with the lowest risk. [reproduced from Eijsvogels et al. (20)]
Figure 3: The multifaceted and team-based approach to the primary prevention of cardiovascular disease [reproduced from Arnett et al. (33)]