What percentage of adults in the United States meet the required physical activity guidelines to achieve the threshold for health benefits?

Front Public Health. 2019; 7: 135.

Abstract

The new 2018 Physical Activity Guidelines for Americans provides updated recommendations for physical activity behavior. These guidelines remove the requirement for physical activity to be obtained in bouts of at least 10 min. The purpose of the present study was to provide an updated estimate of the proportion of adults meeting the physical activity guidelines, based on nationally representative data using accelerometers. Data from 6,525 adults were included in this study. The proportion of adults meeting the physical activity guidelines according to the Department of Health and Human Services and according to the American College of Sports Medicine were estimated using [a] lifestyle activities and [b] ambulatory activities only. Estimates of the proportion of adults meeting the physical activity guidelines ranged from 3.4 to 95.6%, even when based on the same data. The large range of these estimates suggest that challenges exist when using accelerometer data to estimate the levels of physical activity behavior in the population. Further, the large range indicates that, perhaps, physical activity guidelines should not be used as a reference point for behavior change. Instead, we suggest that efforts should be made to promote physical activity in reference to current behavior.

Keywords: physical activity guidelines, physical activity behavior, accelerometers, physical activity surveillance, Physical Activity Guidelines for Americans

In 2018, the U.S Department of Health and Human Services [DHHS] and the Physical Activity Guidelines Advisory committee published the second edition of the Physical Activity Guidelines for Americans [1]. Although much of the guidelines are consistent with the previous edition, the new physical activity guidelines indicate “moderate-to-vigorous physical activity [MVPA] of any duration may be included in the daily accumulated total volume of physical activity” [p. A-5], contrasting with the prior guidelines, which indicated that MVPA had to be in bouts of at least 10 min in duration.

According to the previous set of guidelines, estimates of physical activity behavior using device-based measurement [i.e., accelerometers] indicate that the percentage of adults achieving sufficient levels of physical activity is extremely low [2, 3]. However, since removing the 10-min bout requirement, device-based estimates of physical activity prevalence according to the new guidelines have not been documented. With this change, it is likely that the proportion of adults meeting the physical activity guidelines will artificially change or be corrected, not based on any difference in population behavior, but due to the change in the physical activity guideline itself. If every minute of physical activity counts, then previous estimates of population levels of physical activity have likely been underestimated.

To quantify the prevalence of adults meeting the new guidelines, we estimated the proportion of the adult population meeting the physical activity guidelines, with and without the 10-min bout requirement. The criteria for meeting the physical activity guidelines were based on [a] the DHHS Physical Activity Guidelines for Americans [1], and [b] the American College of Sports Medicine [ACSM] [4]. The DHHS and ACSM physical activity guidelines differ slightly because the DHHS Physical Activity Guidelines for Americans recommends 150 min of moderate-intensity equivalent activity per week, while the ACSM recommends a combination of days and minutes per week [30 min on at least 5 days per week] of moderate-intensity equivalent activity. Only the DHHS Physical Activity Guidelines for Americans removed the 10-min minimum bout requirement. We decided to also use the ACSM guideline to estimate the proportion of the adult population meeting the physical activity recommendation because we speculate that the ACSM may follow the lead of the DHHS and also remove the 10-min minimum bout requirement when their guidelines are eventually updated. Thus, we aimed to be more informative and complete in our analyses.

In addition, for each set of guidelines, we estimated the proportion of adults meeting the physical activity guidelines when MVPA was defined by “lifestyle activities” [accelerometer count threshold representing activities of daily living] and “ambulatory activities” [accelerometer count threshold representing exercise specifically related to walking/running activities]. Together, these data describe several estimates of physical activity prevalence that are based on [a] DHHS 2018 and ACSM's 2011 physical activity guidelines for Americans with and without the 10-min minimum bout requirement, and [b] two cut-point criteria for defining MVPA. Our analyses were based on accelerometer data, thus limiting our analyses to the proportion of adults meeting the cardiorespiratory, “aerobic” guidelines only.

Methods

We analyzed data from the 2003–2004 and 2005–2006 cycles of the National Health and Nutrition Examination Survey [NHANES], of U.S. children and adults [5], which uses a stratified multistage probability sampling design to produce a nationally representative sample of the civilian non-institutionalized U.S. population. More recent datasets are not yet available. We limited our potential study sample to the 10,637 NHANES respondents aged 18 years or older who participated in both the interview and physical examination components of the survey. Of 10,637 adults who participated in both the interview and examination components of NHANES during 2003–2006, accelerometer data was collected on 9,601 of the participants. Of these we excluded data from 3,076 participants for the following reasons: accelerometer not calibrated or reliable,