Search Results

You are looking at 1 - 2 of 2 items for :

  • Author: Jay L. Alberts x
  • Athletic Training, Therapy, and Rehabilitation x
  • Refine by Access: All Content x
Clear All Modify Search
Restricted access

Changes in Multi-Joint Performance with Age

Rachael D. Seidler, Jay L. Alberts, and George E. Stelmach

The purpose of this study was to determine whether elderly adults exhibit deficits in the performance of multi-joint movements. Two groups of subjects (mean ages, 68.9 and 30.1 years, respectively) participated in this experiment. Subjects performed planar arm pointing movements to various targets. One target could be achieved via elbow extension only, while the remaining 3 required both elbow extension and horizontal shoulder flexion, thus requiring coordination at the 2 joints. In contrast to the young adults, the elderly adults produced movements that became less smooth and less accurate with increasing shoulder joint contribution. The results imply a selective coordination deficit for the elderly adults. In addition, the elderly adults coactivated opposing muscles more than the young adults for the single-joint movement. However, the elderly adults reduced coactivation at both joints for the 2-joint actions, while the young adults did not. These data suggest a relationship between high coactivation levels and good performance for elderly adults. It may be more difficult for the elderly to implement high coactivation levels for multi-joint movements because of the increased energy costs and complexity of planning required in comparison to the single joint actions. Thus, to achieve motor performance, elderly persons appear to use coactivation in a manner that is fundamentally different than young adults.

Restricted access

Comparison of Pallidal and Subthalamic Stimulation on Force Control in Patient's with Parkinson's Disease

Jay L. Alberts, Christopher M. Elder, Michael S. Okun, and Jerrold L. Vitek

The aim of this study was to determine the effects of unilateral deep brain stimulation (DBS) on the control and coordination of grasping forces produced by Parkinson's disease (PD) patients. Ten advanced PD patients with unilateral DBS in the globus pallidus (GPi) or the subthalamic nucleus (STN) (5 patients in each group) performed a functional bimanual dexterous manipulation task. Experiments were performed in the “Off” medication state with DBS “On” and “Off.” DBS resulted in (a) significant clinical improvements, (b) greater maximum grip force for both limbs, (c) reduced movement time, and (d) bilateral coupling of grasping forces. There were no significant differences between the GPi and STN groups for any clinical or kinematic measures. DBS of the GPi and STN leads to an improvement in the motor functioning of advanced PD patients. Improvement in force-timing specification during DBS might allow PD patients to employ a feedforward method of force control.