Are You as Active as You Think You Are?

When it comes to physical activity levels, our self-perceptions shouldn’t always be trusted, say researchers across the U.S. and Europe.

In a recent study, scientists examined physical activity levels among 1,542 subjects in the U.S., the Netherlands and the U.K. The researchers were curious to learn how the data would stack up against subjects’ own beliefs about how active they were. To find out, the researchers provided participants with wrist accelerometers for 7 days and also asked each person to rate his or her activity level on a 5-point scale: inactive, mildly active, moderately active, active or very active. Participants also reported on physical activity frequency and intensity.

Here’s some of what the researchers learned:

• Accelerometer readings showed that people in the U.K. and the Netherlands were more physically active than those in the U.S.
• In fact, the data showed there were twice as many inactive people in the U.S. as there were in Europe.
• Dutch and English participants tended to report moderate activity levels, whereas U.S. respondents favored extremes: inactive or very active.
• All participants had a tendency to over­estimate their daily activity levels.
• Older participants incorrectly believed they were as active as younger ones.
• Data from the wrist-worn devices classified 60% of older U.S. participants
  as inactive, as opposed to 42% of Dutch participants and just 32% of those in
  the U.K.

The authors suggested that the discrepancies between belief and reality might stem from differences in people’s perceptions of physical activity. This would mean self-reported data is largely unreliable and other means of analysis should be implemented to secure more accurate physical activity accounts.

The authors observed, “The issue is not that simple self-reports of physical activity are less reliable than the more detailed questions for frequency of various levels of physical activity. Rather the problem with both types of questions is that they are understood systematically differently by different groups or by respondents in different countries and hence are unsuitable for use in comparisons across these groups. For that purpose, the use of accelerometry appears indispensable.”

This study appeared in the Journal of Epidemiology & Community Health (2018; doi:10.1136/jech-2017-209703).