Comparison of GT3X Accelerometer and YAMAX Pedometer Steps/Day in a Free-Living Sample of Overweight and Obese Adults

in Journal of Physical Activity and Health

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Tiago V. Barreira
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Catrine Tudor-Locke
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Catherine M. Champagne
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Stephanie T. Broyles
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William D. Johnson
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Peter T. Katzmarzyk
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Background:

The purpose of this study was to compare steps/day detected by the YAMAX SW-200 pedometer versus the Actigraph GT3X accelerometer in free-living adults.

Methods:

Daily YAMAX and GT3X steps were collected from a sample of 23 overweight and obese participants (78% female; age = 52.6 ± 8.4 yr.; BMI = 31.0 ± 3.7 m·kg-2). Because a pedometer is more likely to be used in a community-based intervention program, it was used as the standard for comparison. Percent difference (PD) and absolute percent difference (APD) were calculated to examine between-instrument agreement. In addition, days were categorized based on PD: a) under-counting (> −10 PD), b) acceptable counting (−10 to 10 PD), and c) over-counting (> 10 PD).

Results:

The YAMAX and GT3X detected 8,025 ± 3,967 and 7131 ± 3066 steps/day, respectively, and the outputs were highly correlated (r = .87). Average PD was −3.1% ± 30.7% and average APD was 23.9% ± 19.4%. Relative to the YAMAX, 53% of the days detected by the GT3X were classified as under-counting, 25% acceptable counting, and 23% over-counting.

Conclusion:

Although the output of these 2 instruments is highly correlated, caution is advised when directly comparing or using their output interchangeably.

Barreira, Champagne, Broyles, Johnson, and Katzmarzyk are with the Dept of Population Science, Pennington Biomedical Research Center, Baton Rouge, LA. Tudor-Locke is with the Walking Behavior Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA.

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