The effects of a robot-controlled haptic leash compared with an instrumented cane on gait and posture in post-stroke and older adults

Haptic tensile forces in the direction of locomotion were used in a virtual environment to investigate the adaptation and post-adaptation effects on steady-state walking in older post-stroke (n=14) and healthy age-matched adults (n=14). Increased walking velocity was observed in both post-stroke and control groups by as much as 0.11 m/s and 0.14 m/s, respectively, as subjects adapted to walking with a haptic force. Gait velocity was then maintained above baseline after force removal to an extent comparable to walking with a cane, suggesting a post-adaptation effect. These velocity changes were explained by both decreases in stride time and increases in stride length. Further investigation revealed that, with increased haptic forces, the body's center of mass in post-stroke participants tended to shift towards the paretic side in the mediolateral plane compared to walking with a cane, or even free walking. This effect was most robust in lower functioning post-stroke as compared to higher functioning post-stroke and healthy subjects. Results suggest that increases in velocity with the use of a haptic force may be accompanied by increased usage of the paretic side. Further study will assess the coordination of bilateral limbs to further ascertain these findings.