The functional electrical stimulation component
muscle contraction, orthosis, spasticity
CONTRACTION
As depicted in Fig. The FES device is configured to generate galvanically isolated, biphasic, charge-balanced, and current-controlled pulses with a frequency of 35 Hz and a pulse width of 300 µs. The stimualtion intensity (current amplitude) is selected and set for each individual by an OT when setting up and calibrating the device. To determine the appropriate FES intensity for an individual, the OT begins stimulating the targeted muscle at a low intensity and progressively increases the intensity until a level of muscle contraction sufficient for a functional movement is achieved without causing discomfort. This intensity is proportional to the individual's body structure and the targeted muscle and can reach up to 100 mA (amplitudes beyond 50 mA are not tested if no discernible muscle contraction is elicited.). It is worth noting that while the beneficial effects of FES rehabilitation devices on spasticity are well known, for participants with high levels of spasticity, the use of FES alone may not be enough to achieve functional UE motion, or may require stimulation intensities that are intolerable. This was the sole rationale for developing a hybrid orthosis that combines a motorized orthosis with a FES orthosis to give the OT more options to choose from based on the severity of the injury and the rehabilitation stages.