Key Concepts about Physical Activity Guidelines

Physical Activity Guidelines for Americans

In 2008, the Department of Health and Human Services produced the first comprehensive set of recommendations on physical activity issued by the federal government¹. The 2008 Physical Activity Guidelines for Americans were based on science reviewed by the Physical Activity Guidelines Advisory Committee (PAGAC), a panel of 13 leading experts in the field of exercise science and public health.  The panel conducted a review of scientific data on physical activity and health published since the release of the 1995 Centers for Disease Control (CDC)/American College of Sports Medicine (ACSM) joint recommendation.²

The PAGAC affirmed the 1995 CDC/ACSM recommendation.  However, committee members emphasized that limitations of existing scientific evidence preclude researchers from suggesting that 30 minutes of moderate-intensity physical activity 5 days each week has additional health benefits beyond 150 minutes of activity spread across an interval less or greater than 5 days per week.  As a result, the Guidelines simplified the previous recommendations, stating that adults should achieve the equivalent of at least 150 minutes of moderate-intensity aerobic activity in bouts of 10 minutes or greater spread throughout the week. Table 1 presents examples of moderate- and vigorous-intensity activities.

Table 1. Examples of Aerobic Physical Activities and Intensities*

Moderate Intensity (MET 3.0 – 5.9)

Walking briskly (3 miles per hour or faster, but not race-walking)

Water aerobics

Bicycling slower than 10 miles per hour

Tennis (doubles)

Ballroom dancing

General gardening

Vigorous Intensity (MET ≥ 6.0)

Race walking, jogging, or running

Swimming laps

Tennis (singles)

Aerobic dancing

Bicycling 10 miles per hour or faster

Jumping rope

Heavy gardening (continuous digging or hoeing, with heart rate increases)

Hiking uphill or with a heavy backpack

*Table 1 is adapted from the 2008 Physical Activity Guidelines for Americans¹.

The Physical Activity Guidelines for Americansdefine physical activity any bodily movement produced by the contraction of skeletal muscle that increases energy expenditure above a basal level. However, the Guidelines focus on the subset of physical activity that enhances health.  Health enhancing physical activity can be obtained in many ways. Thus, while planned exercise yields many health benefits, physical activity recommendations may be met through a number of daily activities. Current research seeks to measure physical activity accumulated throughout the day across four domains: 

• Leisure-time
• Household Chores and Yard Work (Domestic)
• Transportation
• Occupation

The NHANES physical activity questionnaire measures frequency and duration of participation in leisure-time, household chores and yard work, and transportation physical activity. In later courses of this tutorial, we will teach you how to prepare an analytic dataset that you can use to compare the weekly physical activity volume of NHANES respondents to the 2008 Physical Activity Guidelines for Americans. (You also can use other established guidelines or sets of criteria to evaluate physical activity volume of NHANES study participants).

 

National Surveys for Physical Activity and Cardiovascular Fitness

Physical activity surveillance and assessment allows public health researchers to monitor trends in the achievement of recommended amounts of activity, compare levels of activity in the US to levels in other countries, and identify barriers to improving levels of physical activity. Several national health surveys are used to monitor physical activity (See Table 2). These surveys measure activity across the four physical activity domains with varying modes of data collection. 

Of these, NHANES is the only national survey that has, in addition to collecting self-reported physical activity behaviors, obtained objective measures of physical activity from an accelerometer (2003-2006), and assessed cardiovascular fitness through use of a submaximal fitness evaluation (1999-2006).

Table 2. National Surveys for Physical Activity³

Survey*	Target Population	Data Collection Mode	Data Collection Frequency	Physical Activity Domains
NHANES	Children and adults in US (Approx. 10,000 respondents in 2001-2002)	Personal interview and Physical examination	Ongoing, 2-year cycles	Leisure-time Domestic Transportation
BRFSS	Adults (aged ≥18 years) in US states, territories, and the District of Columbia (Approx. 304,000 respondents in 2004)	Telephone interview (one adult per household)	Annual (fixed core questions asked every year; rotating core questions asked every other year)	Leisure-time Domestic Transportation
NHIS	Adults and children in US states and the District of Columbia (Approx. 100,000 respondents in 2004; 31,000 adults sampled for physical activity)	Personal interview (household interview survey)	Annual	Leisure-time
YRBSS	US high school students in  (grades 9–12). 15,200 respondents in 2003	School-based student self-administered paper survey	Every 2 years	Leisure-time Domestic Transportation
SHPPS	US school districts, state education organizations, and classrooms	Self-administered mail survey (state, district levels); computer assisted personal interviews (school, classroom levels)	Periodic (1994, 2000, 2006)	Physical activity Policies and curricula

⁶Table 2 is adapted from Kohl III HW, and Kimsey CD. “Physical Activity Surveillance.” In: Epidemiologic Methods in Physical Activity Studies. Ed. Lee IM. New York: Oxford University Press, 2009. 124-136.

*Abbreviations: NHANES: National Health and Nutrition Examination Survey; BRFSS: Behavioral Risk Factor Surveillance System; NHIS: National Health Interview Survey; YRBSS: Youth Risk Factor Behavior Surveillance System; SHPPS: School Health Policies and Programs Study.