Abnormal upper extremity coordination can be expressed in the form of atypical muscle synergies that result in limited and stereotypic movement patterns when an individual with hemiparetic stroke attempts to support the arm against gravity. These movement constraints are functionally disabling. We have developed and are employing the Arm Coordination Training 3D Device (ACT 3D). This report documents evidence supporting the efficacy of an impairment-specific dynamic reaching protocol for a group of individuals with chronic stroke and was taken as part of a larger randomized controlled trial (RCT). Six individuals with stroke were trained to actively support their arm while reaching to various outward targets over a period of eight weeks. The intervention was progressed by increasing the level of required active limb support or gravitational loading experienced by the participant during reaching repetitions as performance improved. Reaching work area was evaluated pre- and post-intervention for ten different support levels along with a battery of clinical assessments performed by a blinded physical therapist. There was a significant effect of session (pre vs. post) with an increase in reaching work area and a concurrent significant improvement on some of the clinical impairment assessments. This data suggests that specifically targeting the abnormal joint torque coupling impairment is an effective strategy for improving reaching work area following hemiparetic stroke. Following the completion of this study physical therapists will have new evidence supporting the application of an intervention employing rehabilitation robotics for individuals with chronic and severe hemiparetic stroke.