UTILITY OF THE TRITRAC-R3D ACCELEROMETER DURING BACKPACKING 258

Abstract

The purpose of this study was to determine the utility of the TriTrac-R3D as a valid instrument in the estimation of energy expenditure (EE) as compared to the Aerosport TEEM 100 Metabolic Analysis System. The data storage capability of the TriTrac allows for the long-term estimation of EE. The TriTrac monitors physical activity in movement counts and converts these via software (v2.03) into kcals/min. Prior to the field tests, the subject underwent a maximal stress test to validate the Aerosport with the SensorMedics 2900 metabolic cart. Subsequently, a HR-VO2 regression was developed for backpacking by submaximal treadmill testing with the subject wearing a backpack loaded to 20kg (25% of body weight). The subject hiked in the field wearing the same backpack load on ten different days in order to establish the validity of the TriTrac. Each of these ten hikes were on a measured, level gradient, outdoor course with the subject hiking for one hour at normal walking gait (3 mph) with the Aerosport carried in the backpack. The mean kcals/min (6.39±.69) calculated from the Aerosport VO2 during the field tests was significantly different from the TriTrac kcals/min(5.32±.50) [t(9)=3.32, p=.009]. A 2-day field study at Grand Canyon National Park revealed a significant difference [t(212)=8.34, p<.001] between the mean kcals/min (5.51±1.51) calculated from the HR-VO2 regression equation with the TriTrac kcals/min(4.47±1.02) when hiking down grade. There was also a significant difference [t(254) = 28.91, p<.001] between the HR-VO2 kcals/min(10.39±3.32) and the TriTrac kcals/min (4.14±.78) for the hike back up. Thus, the TriTrac underestimated EE in every instance, and did not distinguish between uphill and downhill hiking.