Technical Reliability Assessment of the Actigraph GT1M Accelerometer

Abstract

The purpose of this study was to determine the reliability of the Actigraph GT1M (Pensacola, FL, USA) accelerometer activity count and step functions. Fifty GT1M accelerometers were initialized to collect simultaneous acceleration counts and steps data using 15-sec epochs. All reliability testing was completed using a mechanical shaker plate to perform six different test conditions in Experiment 1 and 18 test conditions in Experiment 2. The overall intra- and inter-instrument reliability of the GT1M was CV_intra = 2.9% and CV_inter = 3.5% for counts and CV_intra = 1.1% and CV_inter = 1.2% for steps. No batch effects were evident in the 50 GT1Ms. The Actigraph GT1M accelerometer demonstrated good reliability for measuring both counts and steps. However, the ability of the GT1M to consistently detect acceleration at a given acceleration and frequency condition varied widely. Future studies clarifying the filtering limitations and the threshold necessary to detect the occurrence of movement are warranted.

Key words:

• frequency
• pedometer
• filter
• acceleration

ACKNOWLEDGMENTS

This study was supported by FCT—SFRH/BD/23088/2005. Disclaimer: This study was not funded in any way by the accelerometer manufacturer. The results of this study do not constitute endorsement by the authors of the product described herein.