COMPARISON OF ACTIVITY MONITORS WORN DURING TREADMILL WALKING

Abstract

56 This study assessed the ability of four different activity monitors' to discriminate small changes in walking speed and the utility of the activity monitors' estimation of energy expenditure(EE:when appropriate) compared to indirect calorimetry(IC-EE) while walking on a motor-driven treadmill. Twenty-four subjects walked at 2.0, 2.5, 3.0, 3.5, and 4.0 mph (0% grade) for separate 30-min periods. The Tritrac-R3D(TT), Computer Science and Applications, Inc.(CSA), Mini-Logger Series 2000(ML), and Yamax Digiwalker® 500(YX) were secured at the waistline of each subject. A CSA was also worn on the wrist and ankle. Each activity monitor detected significant changes in activity and IC-EE at each treadmill speed. For all speeds there were significant relationships between IC-EE and TT-EE(r=0.94), YX-EE(r=0.85), CSA hip(cts·min-1, r=0.77) and ML(cts·min-1, r=0.75). At all speeds TT-EE significantly overestimated EE by an average of 0.81 kcal·min-1. YX-EE significantly underestimated IC-EE at 2.0 mph (0.80 kcal·min-1) at 3.5 mph and above by an average of 0.32 kcal·min-1. For all speeds TT-EE explains 88% of the variance of IC-EE with standard error of the estimate(SEE) of 0.50 kcal·min-1. For all speeds, CSA hip and body mass as variates explains 85% of the variance of IC-EE with a SEE of 0.58 kcal·min-1 while ML and body mass as variates explains 76% of the variance of IC-EE with SEE=0.70 kcal·min-1. While all methods provided strong correlations between the respective method and IC-EE, TT-EE or CSA, with the knowledge of body mass, are likely the methods of choice to predict EE when walking on a level surface.