Evaluation of applied forces and EMG of the young, aged & stroke population in a 3D arm workspace

The objectives of this study were to evaluate 11 muscle electromyograms (EMGs) while performing force application tasks in a 3D workspace, and to identify challenging regions within the workspace in which subjects had difficultly generating forces in desired directions. Each subject (4 young healthy adults, 4 older with stroke-induced disability, 4 age-matched older) applied forces (8 lbs desired) in 6 directions at 19 locations spatially distributed in the workspace. The normals could meet the force threshold levels except for the 2 female aged participants for the Right force direction. The stroke group had common difficult directions of Up and Right. The muscle activations were dependent upon the applied force direction, with Up force being associated with maximum EMGs. Maximum variation in the EMGs was in the right and far region for the young adults and in far and low region for the older adults. The stroke subjects' shoulder-arm EMGs showed less directional variability in the regions of workspace, and considerable compensatory trunk movement, unlike the normals.