Impairment of hand function with age is a major disabling factor limiting many activities of daily living. A decrease in the hand dexterity may lead to a loss of independence and require external care during most everyday activities. Our present understanding of the functioning of the human hand and changes in its function with age is limited. This makes it imperative to perform studies directed at improved understanding of the hand function and its deterioration with age. Series of studies on control subjects and preliminary findings in a small group of elderly subjects have allowed us to formulate two major hypotheses: (a) Aging is associated with selective impairment of intrinsic hand muscles; and (b) Aging is associated with an increase in force deficit during multi-finger tasks. The following research program has been elaborated for an analysis of possible contribution of these age-related changes to the loss of hand dexterity with age: (1) Confirmation of the preliminary conclusions using a larger subject population and a wider spectrum of tasks; (2) Analysis of the effects of these changes on crucial features of multi-finger synergies such as minimization of secondary moments and patterns of variability of individual finger forces (error compensation among fingers); (3) Analysis of possible changes in finger and hand coordination during more common actions such as gripping and bi-manual object handling; and (4) Analysis of correlations between changes in the indices of finger coordination and activities of daily living that involve hand function. Seven experiments on elderly and control subjects are suggested that include force production by sets of fingers in gripping and pressing tasks, self-imposed perturbations, and bi-manual object handling. The research will combine noninvasive behavioral, biomechanical, electrophysiological, and modeling methods, as well as questionnaires. In one experiment, the results will be compared with indices of the activities of daily living. Disprovable predictions are made for each experiment. We believe that supporting or disproving the two main Hypotheses is important not only for a better understanding of age-related changes in hand muscle coordination but also for development of new rehabilitation approaches to hand function.
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