Comparison of the RT3 Research Tracker and Tritrac R3D accelerometers.

This study compared the RT3 Research Tracker accelerometer to the Tritrac R3D accelerometer in both laboratory and field settings and tested the hypothesis that the RT3 records higher physical activity counts and smaller standard deviations than the R3D. The RT3 is relatively new and untested and its concurrent validity with existing instruments and physical activity needs to be assessed before being used in research. In this study the RT3 had higher average recordings of physical activity counts in all of the nine testing situations than the R3D. However, in terms of agreement between the instruments, the RT3 might be 582 below or 1,236 above (activity counts) the R3D in assessing physical activity. These results do not establish that the RT3 is more consistently measuring higher physical activity counts than the R3D. Comparing vector magnitude with oxygen consumption and heart rate across the 0% grade testing conditions indicated that the RT3 and R3D are sensitive to changes in various intensities of level ambulation. When the 5%, 10%, and 15% grade on the treadmill protocols were analyzed, low correlations between oxygen consumption and heart rate with vector magnitude responses were found for both the RT3 and R3D. Differences in agreement between the RT3 and R3D did not vary in any systematic way over the range in testing conditions which substantiates that the RT3 and R3D accelerometers are sensitive on flat surfaces but are insensitive to changes in grade.