Adherence to US Physical Activity Guidance Flattens as Sedentary Time Creeps Up

Adherence to physical activity recommendations has not improved since the release of the first guidelines in this field and in a worrisome new observation, that plateau was accompanied by an increase in sedentary behavior.

The findings, published today in JAMA Network Open, suggest that physicians need to do more, Yang Du, MD (University of Iowa, Iowa City), and colleagues say. “Further nationwide efforts appear to be warranted to not only promote physical activity but also reduce sedentary time in the United States.”

The updated Physical Activity Guidelines (PAG) for Americans, released at the American Heart Association Scientific Sessions last year, upheld key recommendations on aerobic activity set out in the 2008 guidance—namely, that adults should do at least 150 minutes per week of moderate-intensity or 75 minutes of high-intensity aerobic physical activity. The new guidelines went one step further by also urging Americans to sit less, but as Du et al point out, the harms of sedentary behavior have only recently been the subject of study and physicians may not be addressing these risks with their patients.

The new study drew on data from National Health and Nutrition Examination Surveys from 2007 to 2016 and, in a novel approach, considered not only leisure-time activity but also work-related and transportation-related aerobic activity. Among the more than 27,000 respondents, adherence to aerobic activity as defined by the guideline recommendations was 65.2% in 2015-2016—not significantly different from the 63.2% adherence reported in 2007-2008 (P = 0.15 for trend). Notably, time spent sitting increased significantly over time, from a mean of 5.7 hours per day to 6.4 hours between the two periods (P < 001 for trend).

Commenting on the new numbers for TCTMD, Paul Thompson, MD (Hartford Hospital, CT), said he actually found the report “kind of encouraging,” noting that it was appropriate of the authors to include work- and transportation-related physical activity.  

Doing anything is better than doing nothing, and that's really the message that cardiologists should try to get out there. Paul Thompson

“The percentage of people meeting the guidelines has not gone down. If anything it's gone up a little bit, not statistically significant, but it hasn't gone down, so there is some positive stuff here,” he said. “The problem seems to be the increase in the amount of total inactivity, which is not surprising given the widespread use of computers, etc.”

Thompson believes that the numbers speak to the larger problem of physicians being ill-informed and undertrained in counselling patients about aerobic activity, something he pointed out is scarcely covered in medical school. “What physicians should take out of this, cardiologists specifically, is that we all should have an interest in exercise, we should know what our people are doing physically, and we should encourage them to be physically active as best they can be,” he stressed.

A key aspect of the new PAG is that while numbers of minutes per week of moderate and vigorous activity are specified, the requirement has been dropped that a “bout” of exercise only counts if it is 10 minutes or longer. This is a point also emphasized by Katrina L. Piercy, PhD, RD (Department of Health and Human Services, Rockville, MD), in an accompanying editorial. “Ideally, people should meet the PAG targets to obtain the most of the health benefits,” she writes, “but considering that currently 25% of adults do no leisure-time physical activity, any increase in physical activity is good.”

Thompson stressed the same point. For one, physicians need to take the time to ask patients about aerobic activity, so that patients get the message that it’s important. But the larger message should be that every little bit counts. “Doing anything is better than doing nothing, and that's really the message that cardiologists should try to get out there,” Thompson said. “I don't care what you do, just be the Nike commercial and just do it.”