Effects of Body Mass Index and Tilt Angle on Output of Two Wearable Activity Monitors

• Autores: Yuri Feito, David R. Bassett, Brian M. Tyo, Dixie L. Thompson
• Localización: Medicine & Science in Sports & exercise: Official Journal of the American College of Sports Medicine, ISSN 0195-9131, Vol. 43, Nº. 5, 2011, págs. 861-866
• Idioma: inglés
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• Resumen

  • ABSTRACT: Accelerometer-based activity monitors have been used to provide objective measures of physical activity and energy expenditure (EE) in free-living individuals. However, output from these devices has not been compared among normal, overweight, and obese individuals.

    Purpose: The purpose of this study was to examine the effects of body mass index (BMI) and device tilt angle on activity counts recorded by wearable monitors in a controlled laboratory setting. A secondary aim was to examine the effects of these variables on estimated EE.

    Methods: Seventy-one healthy adults wore an Actical and an ActiGraph GT1M on the right and left hip, respectively, while walking at 40, 67, and 94 m·min-1. EE was measured by indirect calorimetry and compared with estimated values using published equations. Three-way repeated-measures ANOVA were used to examine differences in outcome variables (activity counts and EE) between speeds, BMI, and tilt angle for each device.

    Results: No significant differences in activity counts were observed among BMI categories for either the Actical or ActiGraph (P > 0.05). For the Actical, however, among those with an absolute tilt angle <10°, the obese group recorded higher activity counts than the normal weight group (P = 0.01). Using the Heil two-regression model, the Actical overestimated EE by up to 35% at the intermediate speed and up to 12% at the fastest speed (P < 0.001). The Freedson METs regression equation yielded closer estimates of EE than the Freedson kilocalorie regression equation.

    Conclusions: Our findings indicate that the Actical has limitations when comparing individuals with varying BMI and tilt angles in a controlled laboratory environment. The ActiGraph seems to be a more suitable device for making these comparisons.