Age Related Differences in Multi-Digit Coordination

Open Access
Author:
Olafsdottir, Halla Björg
Graduate Program:
Kinesiology
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
November 13, 2007
Committee Members:
  • Mark Latash, Committee Chair
  • Vladimir M Zatsiorsky, Committee Member
  • Steven Howard Zarit, Committee Member
  • Karl Maxim Newell, Committee Member
Keywords:
  • Aging
  • Coordination
  • hand
  • motor control
Abstract:
This dissertation addresses differences in multi-finger coordination related to aging. It attempts to identify some of the processes that may facilitate the observed decrease in dexterity with advancing age and investigates the effects of strength training on some of these changes. The experiment on the effects of aging on multi-finger coordination in a moment of force production task showed that elderly individuals had a reduced ability to produce synergies that stabilize the total moment and the total force. This suggests that elderly individuals have a decreased ability to coordinate commands to the fingers in order to stabilize action, and in particular rotational action. The two experiments that addressed anticipatory synergy adjustments (ASAs) showed that elderly individuals are not able to manipulate synergies in preparation to a predictable change in the force output to same extent as the younger people. Combined, the results of these studies suggest that aging is associated with a decreased ability to use feed-forward adjustments in preparation for an anticipated change in the performance variable and provide further support for feed-forward nature of ASAs. The experiment on the effects of repetitive testing on indices of finger interaction displayed that repeated testing is not sufficient to generate changes in these indices. These results can be used to support the argument that the training induced changes observed in the last experiment were truly due to training and not familiarity with the experimental setup. The final experiment, investigated the effects of site specific strength training on maximal voluntary force, enslaving and performance on an accurate force production task and functional clinical tests in the elderly. This study showed that strength training has general improving effects on force produced at both sites of both hands regardless if they received training or not but these effects were most prominent at the trained proximal sites whose force is mostly generated by the intrinsic hand muscles. This suggests that focused training of the intrinsic muscles may result in an improved ratio between the intrinsic and extrinsic muscles and allow the extrinsic muscles to be activated to a larger degree. When taken together, this series of studies has enhanced our knowledge of changes in finger interaction and coordination in aging. These studies carry a negative message of impaired multi-finger synergies in the elderly but also a positive message that such changes may be counteracted or even reversed with appropriately designed exercise.