Comparison of forward and backward postural perturbations in mild-to-moderate Parkinson's disease.
Chiahao Lu, Sommer L Amundsen-Huffmaster, Kenneth H Louie and 6 others
PMID 33360643WHAT IT FOUND
People with Parkinson's disease showed no difference from controls in the number of steps taken to recover balance after backward or forward perturbations.
However, a detailed analysis of body sway identified a distinct difference during forward stepping, suggesting subtle motor control issues that standard step counts miss.
Key findings
01The number of steps required to recover balance did not differ significantly between the Parkinson's disease group and the control group overall.
02A principal components analysis of center of pressure data revealed a significant difference between the groups during forward stepping, but not during backward stepping.
03The detailed sway analysis correlated with the number of steps taken, where a higher score indicated less Parkinsonian movement patterns.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The study used a laboratory treadmill perturbation, which differs from clinical settings or real-world slips and trips. Participants with Parkinson's disease were tested off medication, which may not reflect their balance capabilities during their typical 'on' medication state. The step count is a coarse measure (integer only) and may miss subtle timing or quality differences in movement that the sway analysis captured. The study included only mild-to-moderate cases, so findings may not apply to severe Parkinson's disease.
Declared interests
The authors declare no conflicts of interest.
The easy way to misread this
Do not conclude that backward pull tests are ineffective for screening Parkinson's disease based on this study. The lack of difference in step counts suggests that simple step counting is insensitive to subtle deficits, not that backward perturbations are clinically irrelevant. The study shows that detailed sway analysis, not step count, reveals the forward-stepping deficit.