Measuring Pelvis Displacement with Acceleration Sensor

Sensors measuring the electrodermal resistance were placed over the tips of the right index and ring fingers (T.K.K.2701, Takei Kiki, Tokyo). The anterior–posterior displacement of the pelvis was measured using an acceleration sensor (AS-10TB, Kyowa Dengyo, Tokyo) during experiment 2. This acceleration sensor was placed over the skin at the midpoint between the left and right posterior superior iliac spines with an elastic tape (Kunimura et al., 2019a (link),b (link)). The signal from the acceleration sensor was amplified with a high-cut filter of 1 kHz using a strain amplifier (CDV-700A; Kyowa Dengyo, Tokyo). Measuring the acceleration of a body part is a valid and reliable method of estimating motor responses during the postural task (Kavanagh and Menz, 2008 (link)). Previous studies have shown that the displacement of the trunk in quiet stance or during step initiation was successfully measured by the acceleration sensors placed on C7 and L5 (Mancini et al., 2009 (link); Mancini and Horak, 2010 (link)). The analog signals from the acceleration sensor and from the sensors measuring the EDL were converted to digital signals at a sampling rate of 1 kHz using an A/D converter (PowerLab 800S; AD Instruments, Colorado Springs, CO, United States), and the digitized signals were stored on a PC.