Author(s): Shaun Porter, Christopher Dalton and Julie Nantel
Reaching forward requires preparing and regulating the trunk progression to avoid falling, but also controlling balance when recovering from it. Objective: To measure postural stability in individuals with Parkinson’s disease (PD) and healthy older adults before, during and when recovering from a Forward Reach Task (FRT). Methods: Nineteen PD (Dx: 5.3 ± 3.8 years; Hoehn and Yahr, 1-3) and sixteen older adults performed the FRT on a force platform and completed the Montreal Cognitive Assessment (MOCA) and self-reported falls (12 months). Center of pressure displacement variability (CoP) and CoP velocity (VCoP) were calculated before (T1), during (T2), and after (T3) reaching. Correlations assessed the relationship between postural stability during these periods, FRT, falls and MOCA scores. Results: Variability in CoP T2 medial-lateral (ML), velocity T1 and T3, p<0.05 were larger in PD compared to Controls. In anterior-posterior (AP) velocity in T1, p<0.05 and T2, p<0.001 and variability in CoP T3 were larger in controls than in PD, p<0.05. In PD, FRT distance was correlated with ML CoP T1 (r=-0.73, p<0.001), CoP T2, T3 (r=-0.59, p<0.01). Conclusion: Older adults showed postural instability in the main direction of the task (AP) whereas those with PD were mostly unstable in the ML direction. In PD, the large contribution of postural control in ML was correlated with decreased reach distance, increased number of falls and disease duration. Altogether this highlights that individuals with PD and more so fallers, rely heavily on postural control in the ML direction before, during and when recovering from a forward reach.
