The procedure of measuring leg movement and EMG monitoring

When applying the pressure with finger, the precise value of applied pressure cannot be controlled. Therefore, converting the applied pressure value with the corresponding resistance value shown in Fig. 2f and by changing the resistance value, we monitored the EMG signal as well as leg movement simultaneously. To quantitatively analyze leg movement when external pressure is applied, three reference points (knee joints, ankle, metatarsal head) were designated to determine the leg movement angles which were obtained by connecting the three reference points^31,37,61

Two methods are available for measuring EMG signals, including the needle-insertion-based method and conductive patch-based method. Needle-insertion EMG measurement method is invasive compared to the conductive patch-based method, it allows for more precise monitoring by directly recording the electrical signal from muscles. Therefore, we chose the needle-insertion EMG measurement method for more precise analysis of the leg movement according to applied pressure. Supplementary Fig. ²¹ shows the setup of needle-insertion EMG signal measurement by inserting the needles in leg muscle (soleus) which is responsible for leg contraction, with needle spacing of 1 cm and on the back side of the body for the reference electrode. Three electrodes were connected to the commercial EMG module (PSL-iEMG2, PhysioLab) which includes filters and amplifier for noise removal. Amplified and filtered signals are recorded by a voltage-based data acquisition system (DAQ) module (PXIe-6365, National Instruments) with the sampling frequency of 7000 Hz.