Assessment of Upper Limb Joints Position During Reach and Grasp Functions in Different Heights and Weights in Sub-acute Stroke Patients

Introduction Up to 75% of stroke survivors suffer persistent UL sensorimotor impairments, which considerably affect their ability to reach, pick up, and hold on to objects. Such deficits dramatically reduce the independence and, consequently, the quality of life, of post-stroke patients, and means for improving the effectiveness of post-stroke UL rehabilitation are much sought after. A prominent post-stoke UL impairment, which is strongly correlated with the level of the general post-stoke impairment and considerably affects daily activities and independence, is an impairment in reach-to-grasp (RTG) movements. Specifically, following stroke, movements become less smooth, less accurate, and less efficient than those of healthy individuals. As a result of such impairments, compensatory movements emerge, whereby the movement goal is achieved using an abnormal muscle activation pattern-e.g., excessive trunk displacement and a frontal hand orientation for grasping-which can lead to pain and fatigue. Retraining the coordination of RTG movements is, therefore, a major goal of post-stroke rehabilitation.

Despite extensive studies of post-stroke RTG movements, information is limited on how the height and weight of objects affect the ability of the impaired UL to reach and hold on to these objects - two crucial abilities for performing daily activities. Previous studies have shown that the height of the target object affects post-stroke RTG movements-namely, when post-stroke patients reach to higher targets, they recruit excessive compensatory muscles in the impaired UL, take longer to reach the target, demonstrate increased endpoint error, shoulder flexion, and abduction range of motion, and activate different muscle patterns to stabilize their trunks-highlighting the need to consider the height of target objects when formulating intervention programs to improve post-stroke RTG movements. However, most available studies of post-stroke UL RTG movements employed virtual tasks, which cannot accurately represent the physical world; It has been shown that, in both in stroke survivors and healthy individuals, an RTG task in a virtual 2D environment is slower, shorter, less straight, less accurate, and involves smaller ranges of shoulder and elbow joint excursions than an RTG task in a real, physical environment. These findings and others stress the importance of using real, daily objects of different heights to characterize and treat post-stroke UL RTG movement impairments. In addition, moving the arm while holding an object requires the individual to (unconsciously) increase the grip force to prevent the object from sliding, which may be impaired in post-stroke patients. However, clinical practitioners typically employ designated tools to measure grip forces after stroke-e.g., a dynamometer or a Pinch,-Grip,-Lift-and-Hold apparatus-rather than daily objects. The investigators are not familiar with studies that test lifting everyday objects of different weights following a stroke. Therefore, the first aim of the proposed study is to characterize the RTG movements and the grasp forces of post-stroke patients, as compared with those of healthy control individuals, attempting to reach, grasp, and lift real, functional, daily objects placed at different heights and of different weights.

Aim: to identify key differences between the RTG movements of post-stroke patients and healthy controls toward real objects of different weights and placed at different heights.

Comprehensively characterize the quality and efficacy of task-oriented RTG movements of sub-acute post-stroke patients and of healthy individuals to real, functional objects of different weights, placed at different heights (vertical distance from the participant), using a motion-capture system and a force sensor. Each participant repeats a RTG movement 18 times, 3 times each height and condition of cup (empty or full).

A total of 60 participants will take part in this study. Thirty hospitalized post-stroke patients will be recruited from the inpatient population of "Bet Hadar" geriatric rehabilitation center. In addition, thirty age-matched healthy control participans will be recruited from the community.