Mediolateral stability during gait in people with Parkinson's disease

Gait control is a clinical problem in people with Parkinson’s disease (PD). Gait variability leading to instability is commonly measured using spatio-temporal variables like step length, step time, step width and cadence. Another measurement that provides information about directional instability is harmonic ratios (HRs). The purpose of this study was to examine the relationship between step width and mediolateral stability using HRs in people with Parkinson’s disease (n = 19) and age matched controls (n = 19). The participants walked at their preferred pace and then with a wider step width and narrower step width. The results showed that the PD group exhibited lower HRs compared to controls in preferred gait and a narrower step width. As expected, HRs were lower for both groups when walking with a narrow step width compared to preferred gait, but counter to expectations, the decrease was similar between groups. Overall, these data indicate that step width directly influences ML-HRs, and that decreased ML dynamic balance with PD severity may be related to a reduction in step width. The information gathered in this study may help in improving intervention strategies for gait instability.