Examining the Ability of Two Actigraph Models to Detect and Discriminate Between Low Frequency Movements

Abstract

Recently, there has been a notable shift to increasingly more sedentary lifestyles, yet it remains unclear whether inexpensive accelerometers, such as those contained in Actigraph devices, can provide consistent measurements of low magnitude accelerations. This study sought to explore the ability of two Actigraph models to differentiate low frequency oscillations, in reference to higher-end accelerometers with the idle sleep mode disabled (ISM) (Part 1) and enabled (Part 2) in a controlled environment. Eight GT9X, fifteen wGT3X-BT and two higher-end accelerometers (Triaxial ICP) were mounted to a 6-degree of freedom robot, which introduced frequencies ranging from 0.5-2.0 Hz (Part 1) and 0.5-4.0 Hz (Part 2). To compare the models, the minimum, maximum and range of outputs were calculated for each of the frequencies. Part 1 revealed that the Actigraph monitors were able to detect low frequency oscillations; the captured output was similar across the different Actigraph models but was significantly greater than the higher-end devices. Part 2 demonstrated that amplitudes greater than the described 40 m g (0.392 m/s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) threshold were required for the Actigraph monitors to wake up. This study demonstrates that the GT9X and wGT3X-BT Actigraph accelerometers can detect low magnitude movements when the ISM is disabled.