DESIGN, CONSTRUCTION, AND TESTING OF A DIFFERENTIAL RESISTANCE ELLIPTICAL EXERCISE MACHINE (DREEM) TO REDUCE LEG STRENGTH ASYMMETRY POST-STROKE

Abstract

Stroke is a primary cause of long-term disability. A common outcome is hemiparesis, an imbalance of muscular strength and poor motor control between the two body sides. Resulting gait abnormalities beget compensatory motor patterns, leading to overuse of the stronger leg resulting in pain and injuries. Emerging research indicates that differential leg resistance during exercise may help reverse these effects; however, the size and expense of existing commercial devices may prohibit home use for many. Elliptical machines show promise due to their inherent mechanical simplicity, compactness, and affordability. Here, we present the design, construction and pilot testing of a novel Differential Resistance Elliptical Exercise Machine (DREEM). Design constraints included motor assistance, “free-wheeling” (allows the user to pedal faster than the motor and encounter resistance), and walker accessibility. It was hypothesized that by altering the crank arm length on one side, differential forces between legs could be achieved and controlled. A device was prototyped with a forward flywheel configuration so that it was compatible with a commercial walker. The device was user tested with load cells coupled to each pedal and a motion capture system. The results indicated that shortening one crank arm increased the mean forces exerted by the associated leg, providing preliminary evidence for an affordable home-based rehabilitative exercise device for those living post-stroke.