Load force during manual transport in Parkinson's disease

To search for a physiological method for the measurement of upper extremity dexterity during activities of daily life in Parkinson's disease (PD).

We examined load force output during manual transport in seven patients with PD and 10 healthy controls. PD patients were measured in both the non-medicated and medicated states. The test movement included two continuous sub-movements: an upward-forward transport of an object from the table to the stand, and a downward-backward transport of the object from the stand to the table. Hand movements were recorded using an optoelectronic camera, and load force was measured using a force sensor installed in the test object.

Compared with the controls, PD patients had a different pattern of load force output characterized by slower force development and release, lower peak force, and less dynamic force generation during movement. After medication, the speed of force development and the level of peak force increased in the patients.

These findings suggest that PD impairs the production of preprogrammed movements. The movements observed in the PD patients may result from compensatory strategies relying more on feedback mechanisms.