Effect of a gravity-compensating orthosis on reaching after stroke: evaluation of the Therapy Assistant WREX

Arch Phys Med Rehabil. 2008 Nov;89(11):2121-8. doi: 10.1016/j.apmr.2008.04.022.


Design: Within-subjects repeated-measures design evaluating reaching with and without the Therapy Assistant Wilmington Robotic Exoskeleton (WREX).

Setting: Laboratory.

Participants: Stroke survivors (N=10) with chronic upper-extremity hemiparesis.

Interventions: Not applicable.

Main outcome measures: Arm movement kinematics (Optotrak Certus motion detection system), muscle activity for biceps, triceps, anterior deltoid, and brachioradialis muscles (bipolar surface electromyography).

Results: Significant improvements of reaching distance occurred for all subjects across all targets (P<.001) when using the Therapy Assistant WREX. While the self-selected peak speed of hand movement during the reach decreased significantly with the Therapy Assistant WREX (P<.001), use of the Therapy Assistant WREX led to improved quality of movement as signified by a decrease in jerk (P<.001) and a shift in the timing of the peak speed to an earlier point in the movement (P<.001). Electromyographic muscle activity analysis showed that use of the Therapy Assistant WREX led to a reduction in biceps activity across all targets during the reach (P<.05), in conjunction with a marginally significant reduction in activity of the anterior deltoid (P<.055). No changes were observed in triceps (P=.47) or brachioradialis activity (P=.28).

Conclusions: By reducing requirements for shoulder activation, the Therapy Assistant WREX improved reaching performance among stroke survivors compared with free reaching, thereby potentially facilitating practice of functional tasks.

Publication types

  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Biomechanical Phenomena
  • Electromyography
  • Equipment Design
  • Female
  • Gravitation
  • Humans
  • Male
  • Middle Aged
  • Orthotic Devices*
  • Paresis / rehabilitation*
  • Stroke Rehabilitation*
  • Therapy, Computer-Assisted / instrumentation*
  • Upper Extremity*