Passive Ankle Dorsiflexion EMG Analysis

Surface electromyographic (EMG) signals were recorded from the SOL, medial gastrocnemius (MG), lateral gastrocnemius (LG), and tibialis anterior (TA) in the left lower leg. Ag-AgCl electrodes (Vitrode F-150S, Nihon Kohden, Tokyo, Japan) with an inter-electrode distance of 20 mm were used for EMG acquisition from each muscle (Saito et al., 2019 (link)). The amplifier was set to a gain of 1,000-fold with a band-pass filter between 5 Hz and 1 kHz (AB-611J, Nihon Kohden). The EMG signals and torque signals were simultaneously sampled at 4 kHz using an AD converter (PowerLab, ADInstruments, Melbourne, Australia) and stored on a personal computer using software (LabChart 7, ADInstruments). The root-mean-square (RMS) values of EMG signals of the SOL, MG, LG, and TA during the passive ankle dorsiflexion test were determined for the initial 5° and for the final 5° of dorsiflexion, respectively (Mizuno, 2023 (link)). In each intervention, the RMS values of EMG signals in the lower leg muscles ranged from 21.6 to 41.6 μV for the initial 5° and 21.5 to 40.3 μV for the final 5° of dorsiflexion. Thus, it was ensured that subjects relaxed their lower legs during the passive ankle dorsiflexion test by surface EMG recordings.