EFFECTS OF ELEVATION CHANGES AND INSTRUMENT PLACEMENT CALORIC EXPENDITURE ESTIMATES USING A TRIAXIAL ACCELEROMETER

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The development of triaxial accelerometers has represented an attempt to improve the accuracy of uniaxial sensors to estimate caloric expenditure during physical activity. PURPOSE: The purpose of this study was to examine the validity of energy expenditure estimates using the StayHealthy RT3 tri-axial accelerometer (examined at three different body placements) with indirect calorimetry at a variety of elevation grades. METHODS: Fifteen trained subjects ran at a constant self-selected speed on a treadmill at three different grades (0%, 5%, and 10%). Energy expenditure estimates from three RT3 units (placed at the right hip, left hip, and lower middle back) were compared to energy expenditure measured via a Quinton QMC indirect calorimeter. RESULTS: Mean energy expenditure estimates in kcal/min from the four methods are reported in the table below. Caloric expenditure estimates were not significantly different (p > .05) between RT3 devices at the three different body placements. However, each of these estimates significantly overestimated caloric expenditure at 0% grade compared to QMC. Caloric expenditure (as measured by the QMC) increased significantly from 0%–5% grade and 5%–10% grade. However, there were no significant changes in RT3 estimates of energy expenditure with increasing elevation grade CONCLUSION: The RT3 triaxial accelerometer demonstrates significant limitations for quantifying energy expenditure when compared to indirect calorimetry methods, particularly in their ability to quantify elevation-induced changes in caloric expenditure.Table: No Caption Available