Comparison of Two Tri-Axial Accelerometric Measures of Energy Expenditure

Abstract

1393 The RT3 Tri-axial Research Tracker (Stayhealthy Inc., Monrovia CA) detects motion in three planes of movement, is capable of storing up to twenty-one days of data, and is the newest generation of the TriTrac-R3D accelerometer. PURPOSE: The purpose of this study was to evaluate the ability of the RT3 to accurately estimate energy expenditure (EE) during treadmill exercise compared to EE measures estimated by the TriTrac-R3D and determined from indirect calorimetry. METHODS: A total of 10 male and 10 female apparently healthy adults [mean (SE) age; 26.7 (0.5) y] performed 10 minutes of treadmill walking at 53.6, 80.4, and 107.2 m/min and treadmill running at 134.0, 160.8, 187.6, and 214.4 m/min. Accelerometers were placed bilaterally at the waist in the anterior axillary position, one on each side of the body. Simultaneous measurements of accelerometry and indirect calorimetry were continuously recorded during exercise. Vector magnitude counts and EE data were analyzed for each treadmill speed using a multivariate analysis of variance and post-hoc pairwise Bonferroniadjusted estimated marginal means. RESULTS: For the RT3 and TriTrac-R3D, there was a main effect of speed for vector magnitude counts (P<0.001), estimated activity EE (P<0.001), and estimated total EE (P<0.001). All RT3 and TriTrac-R3D indicators had steady changes with each increase in speed (P<0.01). The RT3 vector magnitude counts and activity EE were significantly different than the same Tritrac-R3D parameters at 53.6, 80.4, 107.2, 187.6, and 214.4 m/min (P<0.01). For total EE, the RT3 was significantly different than the TriTrac-R3D at 53.6, 80.4, 187.6, and 214.4 m/min (P<0.01). Compared to indirect calorimetry, the RT3 overestimated total EE at all treadmill speeds and the TriTrac-R3D overestimated total EE at all speeds except 214.4 m/min (P<0.001). CONCLUSION: This study indicates that the RT3 and TriTrac-R3D accelerometers significantly overestimated EE compared to indirect calorimetry, that the accelerometers were sensitive to changes across a wide range of treadmill walking and running speeds, and that the similarities in vector magnitude counts, activity EE and total EE estimates between the RT3 and TriTrac-R3D were limited. Supported by the Paso del Norte Health Foundation and The University of Texas at El Paso