Assessment of active and passive restraint during guided reaching after chronic brain injury

We report the use of a mechatronic device for assessing arm movement impair ment after chronic brain injury. The device, called the "Assisted Rehabilit ation and Measurement Guide," is designed to guide reaching movements acros s the workspace, to measure movement and force generation, and to apply con trolled forces to the arm along linear reaching paths. We performed a serie s of experiments using the device in order to identify the contribution of active muscle and passive tissue restraint to decreased active range of mot ion of guided reaching (i.e., "workspace deficits") in a group of five chro nic, spastic hemiparetic, brain-injured subjects. Our findings were that pa ssive tissue restraint was increased in the spastic arms, as compared to th e contralateral, nonparetic arms. Active muscle restraint, on the other han d, was typically comparable in the two arms, as quantified by measurements of active arm stiffness at the workspace boundary during reaching. In all s ubjects, there was evidence of movement-generated weakness, consistent with a small contribution of spasticity to workspace deficits. These results de monstrate the feasibility of mechatronic assessment of the causes of decrea sed functional movement, and could provide a basis for enhanced treatment p lanning and monitoring following brain injury. (C) 1999 Biomedical Engineer ing Society. [S0090-6964(99)01106-6].