An American, a Briton and a Dutchman walk around. It may seem like the start of a joke, but it’s actually the end of a USC-led study that could impact future research on physical activity.
Using fitness trackers, an international team of scientists studied how physically active people consider themselves to be physically active, compared to their actual level of physical activity.
Research has found that no one succeeds. The American answers suggest that they are as active as the Dutch or the English. Older people think they are as active as young people. In reality, however, Americans are much less active than Europeans, and older people are less active than younger people.
Does this mean that Americans lie about their physical activity, or that the Dutch and the English humbly underestimate theirs?
This means that people from different countries or from different age groups may have very different interpretations of the same survey questions.
Arie Kapteyn
“This means that people from different countries or from different age groups may have very different interpretations of the same survey questions,” he said. Arie Kapteynlead author of the study and executive director of the Economic and Social Research Center at USC Dornsife College of Letters, Arts and Sciences.
Kapteyn believes that differences in perception of fitness are driven by cultural and environmental differences.
For example, Americans rely heavily on cars while Dutch people frequently walk or cycle to work and for simple errands, Kapteyn said.
The study was published April 11 in the Journal of Epidemiology and Community Health.
Fitness in America: Perception vs. Reality
For the study, the scientists followed 540 participants from the United States, 748 people from the Netherlands and 254 from England.
The men and women in the study, aged 18 and over, were asked in a survey to report their physical activity on a five-point scale, ranging from inactive to very active. They also wore a wrist-based fitness tracker (an accelerometer) so scientists could measure their actual physical activity over a seven-day period.
The researchers found that the Dutch and English were slightly more likely to rate themselves towards the ‘moderate’ center of the scale, while Americans tended to rate themselves at the ends of the scale, i.e. as ‘very active’. or “inactive”. But overall, the differences in how people in the three countries reported their physical activity were small or non-existent.
Wearable devices have revealed some hard truths: Americans were much less physically active than the Dutch and English. In fact, the percentage of Americans in the inactive category was almost twice as high as the percentage of Dutch participants.
Reality Bytes by Age Group
A comparison of fitness tracking data by age group reveals that people in all three countries are generally less active as they get older. That said, inactivity seems more widespread among older Americans than among participants from other countries: 60% of Americans are inactive, compared to 42% of Dutch and 32% of English.
The researchers found that, in all three countries, the disparities between perceived and actual activity levels were greatest among participants who reported being “very active” or “very inactive.”
“Individuals in different age groups just have different standards of what it means to be physically active,” Kapteyn said. “They adjust their standards based on their circumstances, including their age.”
Kapteyn said that since physical activity is so essential to healthy living, accurate measurements are important for science. The results indicate that scientists should proceed with caution when interpreting and comparing the results of international fitness studies that have used standardized questionnaires.
“When you rely on self-reported data, you’re not just relying on people to share a common understanding of survey terms, but to accurately remember the physical activity they report,” Kapteyn said. . “With the wide availability of low-cost activity trackers, we have the potential to make future studies more reliable.”
Co-authors of the study are Htay-Wah Saw from the Center for Economic and Social Research at USC Dornsife College, James Banks from the University of Manchester, Mark Hamer from Loughborough University, James Smith from RAND Corp.Andrew Steptoe from University College London, Arthur van Soest from Tilburg University and Annemarie Koster from Maastricht University.
The US portion of the research was funded by grants from the National Institute of Agingincluding $243,170 (R-37AG25529 to James Smith at RAND and one for $127,060 (R01AG20717) to Kapteyn at USC.
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