Characterizing the coordination of grasp and twist in neurologically normal and post-stroke individuals
Hamed Kazemi (Author)
"We take for granted the ease with which we use our hands to perform many activities including grasping and twisting using forearm rotation. All of these normal hand actions can be disrupted following damage to the brain due to stroke or traumatic injury. This thesis presents a series of studies exploring how post-stroke subjects and healthy, age-matched subjects coordinate grip force with wrist torque when twisting an object using forearm supination/pronation. To obtain a comprehensive picture of how healthy subjects control grip force I performed a series of experiments under various conditions. Using a robotic interface that we developed for rehabilitation and assessment of hand function, I studied grasp and twist by systematically varying task parameters which included elastic resistance, movement direction, hand dominance, size of grip aperture, grip configuration and speed of rotation. When comparing the temporal/amplitude relationship between grip force and load torque across different task conditions, I found a large degree of similarity, indicating that regardless of how the twisting task is performed there is a similar control structure. Healthy individuals modulated grip force in an approximately linear fashion with load under all conditions tested. In addition, the normal force exerted by the thumb and that exerted by the other fingers were highly correlated. The coordination of grasp and twist did not change with hand dominance or with grip configuration. However, the control of grip force changed with the speed of rotation. The parallel coupling between grip force and load was reduced for the fastest rotations. In addition, small differences were found in the correlation between grip force and load torque for supination over pronation. Results of the study with chronic post-stroke subjects showed that the coordination of grasp and twist was frequently impaired in both the contralesional and ipsilesional hands. This was reflected by a lower correlation between grip force and load torque and between thumb force and finger force than in healthy subjects. In addition, the movements were significantly less smooth and movement time was prolonged using either the ipsilesional or contralesional hand compared to healthy subjects. Overall, use of excessive grip force was not prevalent post-stroke and only a minority of post-stroke subjects used significantly greater grip force to perform the task than healthy subjects. The results provide evidence that the coordination of grasp and twist is frequently impaired bilaterally following unilateral stroke. Not only did the contralesional hand exhibit impairment, but in several cases the ipsilesional hand, often referred to as the "unaffected" hand, also showed profound impairment. This detailed analysis of the kinetics and kinematics of a twisting task provides an objective, quantitative means to characterize grip coordination following stroke and may have implications in developing new strategies for training grip coordination."-- Author's abstract
Thesis, Dissertation, English, 2015
McGill University Libraries, [Montreal], 2015
McGill University