In addition to the support provided by the exoskeleton, EMG-triggered FES is delivered to two muscles, selected by the therapist based on the subject-specific needs. For each stimulated muscle, the residual volitional EMG signal is detected and used to trigger the onset of a predetermined stimulation sequence applied to the muscle itself. In case the muscle does not reach the pre-defined threshold, the stimulation sequence is automatically started after a time-out. EMG signals are acquired at 4kHz, the stimulation frequency is set at 25Hz, the pulse width is fixed at 300µs, while the stimulation intensity is set at the beginning of the training session on each muscle individually at a value tolerated by the subject and able to induce a functional movement. Separate EMG and stimulation (Pals® electrodes, Axelgaard Manufacturing Ltd) are placed over each muscle belly. When the stimulation starts, EMG signals are continuously measured in order to provide a visual feedback about the patient's volitional involvement at the end of the execution of each task. An adaptive linear prediction filter is used to estimate the volitional EMG during hybrid muscle contractions. If the mean value of the volitional EMG estimate during the stimulation phase is over a pre-defined threshold, a happy emoji is shown to the patient through the GUI; conversely, if it is below the pre-defined threshold a sad emoji is shown in order to promote the active involvement of the subject. A fast and automatic calibration procedure is required before the beginning of each session. This procedure aims at setting the current amplitude and the EMG threshold values. During the procedure the subject is asked to be relaxed. Specifically, three thresholds are set on each muscle: two of them are used to trigger the stimulation, one in case the muscle is activated as first and one in case the muscle is activated as second one; the third threshold is used to define the subject's active involvement in the task. The thresholds are defined as twice the mean volitional EMG during a phase of no stimulation (first threshold), during a phase of stimulation of the other muscle (second threshold), and during a phase of simultaneous stimulation of the two muscles (third threshold).