Enhancing exploratory learning behaviour in people with stroke undertaking iPAM robot assisted upper limb exercises

This paper describes how semiautomated variation in active upper limb exercise is achieved by the iPAM robotic rehabilitation system. The iPAM system is used to deliver assisted therapeutic upper limb exercise for people with stroke. An admittance control scheme allows the assistance to be tailored to an individual´s needs. A key aspect of motor learning is variation in practice. Therefore a key aspect of robotic rehabilitation systems is that they allow exploration of voluntary movement strategies to maximise motor learning. We investigated the potential for the iPAM system to provide semiautomated variation in upper limb exercise within the context of a single exercise session. Detailed information about iPAM assisted exercise was captured in a person with stroke undergoing iPAM rehabilitation treatment. A functional reaching movement appropriate for the individual was prescribed by a physiotherapist using the iPAM system. The individual was asked to make 30 repetitions of the movement using iPAM. Three levels of assistance were used to determine their impact on the inherent variation in practice resulting from the patient - iPAM interaction. Kinematic and kinetic data of the upper limb joints are presented, together with measures of the patient´s performance in the task. The variance and coordination of the movement attempts is determined using a principle component analysis to reveal the effect of varying the level of assistance. The results show that iPAM does allow individual variation in practice within a single session without need for redefining exercise prescriptions. The degree of variation that the system allows is adjustable within limits based on initial clinical assessment. Without appropriate assistance the pattern of upper limb movement may be adversely affected. This can be mitigated by using the iPAM controller to direct assistance to upper limb joints independently.