Compensatory arm reaching strategies after stroke: induced position analysis

After stroke, movement patterns of the upper limb (UL) during functional arm reaching change to accommodate altered constraints. These compensatory movement control strategies do not, however, have a one-to-one mapping with posttraining outcomes. In this study, we quantify arm movement control strategies in unilateral and bilateral reaching tasks using induced position analysis. In addition, we assess how those strategies are associated with UL residual impairments and with functional improvement after a specific bilateral arm training intervention. Twelve individuals with chronic stroke were measured while reaching to a box as part of their pre- and posttesting assessments. Other measurements included the Fugl-Meyer Upper Extremity Assessment (FM), Modified Wolf Motor Function Test (WT), and the University of Maryland Arm Questionnaire for Stroke (UMAQS). We identified arm control strategies that did not differ between unilateral and bilateral tasks but did differ by FM impairment level and by predicted gains in WT but not UMAQS. Increased shoulder relative to elbow moment contribution was associated with less impairment and greater gains of speed in functional tasks. These results suggest that one goal of training to achieve better outcomes may be to decrease the abnormal coupling of the shoulder and elbow.