Stand-to-sit maneuver in paraplegia after spinal cord injury using functional neuromuscular stimulation

The paralysis resulting from spinal cord injury (SCI) can compromise the independent performance of many activities of daily living. Neuroprostheses utilizing functional neuromuscular stimulation (FNS) are able to restore standing and stepping after SCI by actively contracting the paralyzed muscles. The stand-to-sit maneuver, however, requires good control of eccentric contractions of the knee and hip musculature, which is difficult to achieve with FNS alone. This preliminary study compares the biomechanics of the stand-to-sit maneuver with open-loop FNS to able-bodied in terms of upper extremity forces and sitting impact force. With FNS, the upper extremity forces reached an average of 25% of their body weight more than able-bodied controls during the maneuver. Individuals with SCI also exhibited twice the impact force when making contact with the chair as compared to able-bodied subjects. These large forces and quick descents are potential for injury and an improved method for controlling the stand-to-sit maneuver when using FNS is necessary.