Raising from a chair by the help of open-loop electrical stimulation of knee extensors is well accepted in paralyzed persons. However, electrically stimulated knee extensors provide only low joint moments during raising. Thus, the effort of upper extremities during standing-up is extensive. The aim of the investigation was to study the Influence of the stimulation of ankle plantar flexors and hip extensors on the efficiency of standing-up process. Spinal cord injured subject performed raising from sitting to standing position with surface electrical stimulation. Different combinations of stimulated muscle groups were studied. The stimulation amplitude changed with respect to the current phase of the sit-to-stand process. The vertical arm support force was used to divide standing-up into three phases. The handle reaction force vector was assessed by a robot wrist sensor. The body movement was measured with a contactless optical system. The ground and seat reaction force vectors were determined with force plates. A 3-dimensional model of the human body was used to assess the joint torques. No considerable differences were observed between the different types of raising. Additional electrodes on hip extensors and ankle plantar flexors seem not to be justified for daily FES use. Standing-up is a relatively quick ballistic process. It appears that the patient cannot react in time in order to use his stimulated lower extremities to support the standing-up to a larger extent.
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