Weight shifts by the electrical stimulation in seating for the prevention of pressure ulcer

Pressure ulcer is the injury state by continuous normal or shear stress on the skin for spinal cord injury(SCI) patients. Even though functional electrical stimulation recently receives much attention as a promising method for the pressure ulcer prevention in plegic patients or elderly people, its protocol has not been developed yet. In order to determine which muscle can be stimulated for the pressure ulcer prevention, pressure distributions on the buttock and thigh by the functional electrical stimulation on gluteus maximus, sartorius and hamstring in the seating posture were analyzed. Ten normal young male volunteers who have no physical problem and are able to take normal sitting posture participated in the experiment. Muscles were stimulated once per five seconds, totally six times during thirty seconds by the MP150 stimulator. Ground reaction force and pressure distribution on the stimulated buttock and thigh increased when gluteus maximus was stimulated. Pressure on the stimulated thigh slightly decreased with the individual stimulation of sartorius or hamstring. When both gluteus maximus and sartorius were stimulated at the same time, pressure on the unstimulated buttock and thigh decreased significantly. With the simultaneous stimulation of sartorius and hamstring, both pressure on the stimulated thigh and ground reaction force significantly decreased. Results showed that due to the electrical stimulation, the body weight transferred to the stimulated side and the pressure of the opposite side relatively decreased. There are more synergistic effects on the weight shift, when glueteus maximus is stimulated simultaneously with sartorius or hamstring. In spite of the limitation of surface electrical stimulation on healthy subjects, this study would be very useful to prevent pressure ulcer and select the muscles to stimulate effectively for the elderly and spinal cord injury patients.