Wrist torque estimation during simultaneous and continuously changing movements: surface vs. untargeted intramuscular EMG

This data was recorded for emg based force/Torque estimation. EMG and torque signals were collected during simultaneous, isometric, but continuously varying contractions, corresponding to two wrist DoF. The experiment was carried out in two trials with a 5-min rest in between. Each trial included six combinations of tasks, separated by 2 min of rest to minimize the effect of fatigue. The performed tasks were categorized into individual and combined (simultaneous) DoF to test the ability to estimate isolated torque and torque in two simultaneous DoF. The selected DoF were wrist flexion/extension (DoF1) and wrist supination/pronation (DoF2). The following six tasks were chosen: wrist flexion/extension, supination/pronation, simultaneous flexion + pronation/extension + supination. We chose to use only the two DoF, because no commercially available prosthetic device is currently capable of ulnar and radial deviation. All tasks were dynamically varying, following a sinusoidal profile lasting 30 s at maximum amplitudes of 3 Nm and 2 Nm for men and women, respectively. Torque level was limited to 2 Nm for female subjects, because concerns were raised during pilot testing about the combined movements being uncomfortable for higher torque levels. On the contrary, 2 Nm was too easy for most male subjects, thus 3 Nm was adopted to allow similar EMG activation for female subjects. The first and last 3 s of each profile consisted of a rest period. Sinusoidal profiles were used to elicit dynamic contractions, requiring constant changes in the torque (and EMG intensity) level of the performed task. The subjects were seated in a chair with their right arm placed in an arm rest, while the left arm was left relaxed on the table. Subjects were asked to track one profile or two simultaneous profiles, depending on whether it was a single DoF or two simultaneous DoF,The order of the tasks was randomized, and subjects received visual feedback as to how closely they tracked the profiles. The subjects were given sufficient time for training and to become familiar with the profiles. The frequency of the profiles was 0.5 Hz.