Submovements in manual tracking: people with Parkinson's disease produce more submovements than age-matched controls.
Lior Noy, Sharon Hassin-Baer, Tsvia Fay-Karmon and 4 others
PMID 40050876WHAT IT FOUND
People with Parkinson's made more small corrective movements and had larger timing and position errors than controls during manual tracking.
This held true across all tested speeds. Older adults without Parkinson's showed similar error patterns to younger adults regarding movement smoothness.
Key findings
01Participants with Parkinson's disease produced significantly more type 3 submovements (small corrective inflection points in velocity) than both older and younger control groups.
02People with Parkinson's had significantly greater timing errors and relative position errors during tracking compared to age-matched controls, who in turn had greater errors than younger controls.
03Submovement rates decreased as movement frequency increased for all groups, but there was no difference in submovement rates between older and younger controls.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
The Parkinson's group had relatively mild symptoms (low MDS-UPDRS scores), so results may not apply to those with advanced disease. The study excluded participants with significant tremor or dyskinesia during writing/drawing, limiting generalizability to those with prominent motor fluctuations. The younger control group consisted mostly of university students, while older controls came from the general community, introducing potential confounds in experience or background. The task was a specific manual tracking game; results may not directly translate to complex functional tasks like eating or dressing. Differences in L-dopa dosage among participants may have influenced mood and performance, which were not controlled for.
Declared interests
Funding was provided by Medtronic and the Mariana & George Saia Research Fund for research in HIV and Parkinson’s disease.
The easy way to misread this
Do not conclude that people with Parkinson's are specifically worse at *slow* movements compared to fast ones. The study found that the increase in submovements for PwP was constant across all frequencies tested. The deficit is in the overall quality of movement (more corrections, more error), not a specific breakdown at low speeds.