sEMG signals of ankle movement under different loads

Six male able-bodied subjects participated in this study. The subjects were asked to sit in a chair with their shanks drooping naturally and their whole body relaxed.  During the experiment, the subjects were asked to place their  “unaffected side foot” (left foot) on the moving platform.  At the beginning of the experiment, the subjects were asked to relax and stared at a screen.  A NeuSen WM (China Neuracle company) was used as the sEMG acquisition equipment. The sampling frequency is 1000 Hz and the EMG electrodes are Ag/Cl electrodes. Before the experiment, the skin surface was wiped with alcohol to remove stains from the skin surface in order to reduce the impedance between the electrodes and the skin. After the experiments began, they were asked to perform the movements to the maximum range shown on the screen. The specific process is as follows: (a) keeping relaxed for 4 seconds; (b) performing the ankle joint motion shown on the screen with a constant rotational speed until the rotation limit is reached and this process should be finished within one second; (c) maintaining the rotational angle for 3 seconds; (d) resting for 4 seconds and starting doing the next motion. A set of experiments contained six ankle movements. There was a 5 minutes’ break between each two sets of experiments to prevent muscle fatigue.  Each subject was asked to repeat the experiment for 12 times under each load. In total, 216 (3 loads × 6 movements × 12 times) trials of experiments were completed by each subject. As a result, 6 ×216 = 1296 trails were completed.