Arm-free paraplegic standing. II. Experimental results

For pt. I see ibid., vol. 6, no. 2, p. 125-38 (1998). In pt. I, the authors proposed an approach for restoring unsupported standing to thoracic-level paraplegics. The theoretical analysis and simulation of an underactuated double inverted pendulum, representing the standing subject, showed that arm-free standing might be achieved. Here in pt. II, the authors present the mechanical apparatus which they used in their experiments and experimental results from tests of the balance-control strategy. They demonstrate that an intact and a paraplegic subject could perform quiet standing with the ankle stiffness set to 8 Nm/° or even less (the intact subject). Both were also able to recover from disturbances, imposed by the artificial ankle joint of the apparatus. Introducing cognitive auditory feedback greatly improved the standing abilities of both subjects