Location: Delta Obesity Prevention ResearchTitle: Comparison of GT3X accelerometer and Yamax pedometer steps/day in a free-living sample of overweight and obese adults Author
Submitted to: Journal of Physical Activity and Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2011
Publication Date: 2/1/2013
Citation: Barreira, T., Tudor-Locke, C., Champagne, C., Broyles, S.T., Johnson, W.D., Katzmarzyk, P.T. 2013. Comparison of GT3X accelerometer and Yamax pedometer steps/day in a free-living sample of overweight and obese adults. Journal of Physical Activity and Health. 10(2):263-270. Interpretive Summary: In recent years there has been a steady introduction of new, objective physical activity assessment instruments (i.e., accelerometers and pedometers) to the market. The increased availability of new instrument options creates the need for evaluation of their measurement properties, and their potential feasibility for use by researchers, practitioners, and the general public. We compared the outputs of the Yamax pedometer and the GT3X accelerometer in a sample of free-living adults from the Lower Mississippi Delta. Both devices were worn concurrently, and the results showed a high correlation between the pedometer and accelerometer steps; however, the mean values for the accelerometer were lower than for the pedometer. Caution is needed when directly comparing the output of these two instruments or using their output interchangeably.
Technical Abstract: 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. 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/kg2). 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). The YAMAX and GT3X detected 8,025 +/- 3,967 and 7,131 +/- 3,066 steps/day, respectively, and the outputs were highly correlated (r = 0.87). 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. Although the output of these two instruments is highly correlated, caution is advised when directly comparing or using their output interchangeably.