Grip type and task goal modify reach-to-grasp performance in post-stroke hemiparesis

Abstract

This study investigated whether grip type and/or task goal influenced reaching and grasping performance in poststroke hemiparesis. Sixteen adults with poststroke hemiparesis and twelve healthy adults reached to and grasped a cylindrical object using one of two grip types (3-finger or palmar) to achieve one of two task goals (hold or lift). Performance of the stroke group was characteristic of hemiparetic limb movement during reach-to-grasp, with more curved handpaths and slower velocities compared with the control group. These effects were present regardless of grip type or task goal. Other measures of reaching (reach time and reach velocity at object contact) and grasping (peak thumb-index finger aperture during the reach and peak grip force during the grasp) were differentially affected by grip type, task goal, or both, despite the presence of hemiparesis, providing new evidence that changes in motor patterns after stroke may occur to compensate for stroke-related motor impairment.

Figure 1

(A) Experimental setup. (B) Palmar and 3-finger (3Fgr) grip types are shown. (C) Sample traces of hand velocity (top), aperture (middle), and grip force (bottom) during a hold trial using a palmar grip are shown for a control subject (solid lines) and a stroke subject (dotted lines). Arrows indicate calculated peak values; horizontal lines below x-axis (time) indicate amount of elapsed time from reach start (t=0) and object contact (i.e. reach end) for both the control subject’s (solid line) and stroke subject’s (dotted line).

Figure 2

Effect of group. Right reach paths (wrist sensor, sagittal plane, medial view) from a control (left panel) and stroke (right panel) subject during 3 trials using a 3Fgr grip to lift the object. O indicates object contact. (B) Reach path ratios and (C) peak resultant hand velocities are shown for the control (filled circle) and stroke (open circle) groups when using 3Fgr and Palmar grip types during the Hold and Lift tasks. Values represent group means ± SE. Lower reach path ratios and higher peak velocities indicate more efficient, faster reach performance.

Figure 3

A–D. Effect of grip type. (A) Reach times, (B) contact velocities, (C) peak apertures, and (D) peak forces are shown for the control (filled circle) and stroke (open circle) groups when using 3Fgr and palmar grip types. Significant post-hoc comparisons are indicated by asterisks only for differences between grip type within each group (Control and Stroke), where *p<.05 and ***p<.0001. All post-hoc results are reported in-text. E-F. Effect of task goal. (E) Reach times are shown for the control (filled circle) and stroke (open circle) groups during the Hold and Lift tasks. Within-group post-hoc: Control p=.47; Stroke p=.49. (F) Peak forces are shown for the 3Fgr (black square) and palmar (gray square) grip types during the Hold and Lift tasks. Within-grip post-hoc: 3Fgr p=.29; Palmar p=.68. Values represent group means ± SE.

Figure 4

Grip-related change in reach time, contact velocity, peak aperture, and peak force within each subject in the stroke group, collapsed across task goals. Change (Δ) is the difference in performance between the palmar and 3-finger grip types. Positive values indicate palmar > 3-finger; negative values indicate 3-finger > palmar. Subjects (e.g. H73, H66, etc.) are sorted along x-axis by increasing (A) number of days post-stroke and (B) score on ARAT (normal = 57), shown across top of graphs. Dashed line indicates mean change in the control group.