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1 Kinesiology, Penn State University, University Park, Pennsylvania, United States
2 Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
* To whom correspondence should be addressed. E-mail: mll11{at}psu.edu.
The purpose of this investigation was to document and quantify age related differences in the coordination of fingers during a task that required production of an accurate time profile of the total moment of force by the four fingers of a hand. We hypothesized that elderly subjects would show a decreased ability to stabilize a time profile of the total moment of force leading to larger indices of moment variability as compared to young subjects. The subjects followed a trapezoidal template on a computer screen by producing a time profile of the total moment of force while pressing down on force sensors with the four fingers of the right (dominant) hand. To quantify synergies we used the framework of the uncontrolled manifold hypothesis. The elderly subjects produced larger total force, larger variance of both total force and total moment of force and larger involvement of fingers that produced moment of force against the required moment direction (antagonist moment). This was particularly prominent during supination efforts. Young subjects showed co-variation of commands to fingers across trials that stabilized the moment of total force (moment stabilizing synergie), while elderly subjects failed to do so. Both subject groups showed similar indices of co-variation of commands to the fingers that stabilized the time profile of the total force. The lack of moment stabilizing synergies may be causally related to the documented impairment of the hand function with age.
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