抄録
For the purpose of the restoration of hands-free paraplegic standing using functional electrical stimulation (FES) and an artificial feedback postural control system, electromyogram (EMG) was analyzed in normal subjects during standing, and postural sway from foot pressure was estimated. In the EMG study, activities of 24 muscles, 22 on the left and two on the right, were simultaneously recorded during eight motions: forward, backward, right-leaning, and left-leaning and their reverse motion. The t-test, results showed that the activity of the muscles of the posterior shank, hamstrings, erector spinae, and quadratus lumborum increased in forward leaning. In contrast, the activity of the gluteus maximus did not show an obvious increase. In backward leaning, the activities of the tibialis anterior and quadriceps femoris increased. In coronal plane motion, the gluteus medius, tensor fascia latae, and shank muscles of the weight-bearing leg and the quadratus lumborum of the free leg increased their activities. Four thin film pressure sensors using conductive rubber were put on the big toe, metatarsal head I, metatarsal head V, and heel. The pressure of the heel decreased, and the pressures of other points increased in forward leaning for a normal subject. For paraplegic standing between parallel bars using FES, no sensor output change was observed with leaning because there was less ankle joint stiffness. Therefore, a plastic ankle-foot orthosis was applied to increase the ankle joint stiffness. It was found that postural sway can be estimated by the measurement of foot pressures where there is sufficient ankle joint stiffness. It is expected that these findings will lead to the use of FES to facilitate practical hands-free standing.
