On automatic determination of movement phases in manual transport during the precision grip

Integrated movement and force analysis of the precision grip-lift sequence (grasping an object between index finger acid thumb) is a useful tool in st udies on manipulative hand functions. The everyday Manual Transport tasks, moving objects from one place to another, exhibits powerful test possibilit ies because it includes the precision grip. In this study, as a step toward s the exploitation of these possibilities, we created an algorithm that ext racts sequence of phases in this task. The mathematical and dynamical properties of the movement and force signals were used to determine the start and the end of each phase. The grip-lift synergy was quantified by the correlation coefficient during each phase. Eight patients with Parkinson's Disease (PD) and 10 healthy persons were st udied. The PD patients were tested both in the medicated (ON) and the unmed icated (OFF) state. The object was lifted with the index finger and the thu mb, moved a short distance, and put down on a shelf. The preliminary result s of these experiments displayed significantly higher coordination between the grip and load forces in the initial phases, before the lift was complet ely established, than during the transport phases. This was evident both in PD patients and healthy subjects. This method provides an automatic analysis of the motor performance during an arm-hand movement that is important in daily life to aid in clinical dia gnosis.