2.2. Experimental setup

As shown in Figure 1, a dowel, 20.25 cm long and 4.9 cm in diameter, rested horizontally on a cradle of a custom-made support stand (inner width = 9 cm; outer width = 15 cm; height = 23.5 cm; depth = 5 cm) secured to the table. The dowel, positioned at 75% of the participant’s maximum arm reach, was centered to align with the participant’s acromion process. A target hole, 5.3 cm in diameter, was centered in front of the support stand at about 50% of the participant’s maximum reach. A taped line, positioned at 25% of the participant’s maximum reach, designated the starting position of the tested hand before each trial. To assess reach-to-grasp kinematics, three electromagnetic markers of the motion-tracking system, 3D Guidance trakSTAR NDI, were secured to the radial styloid and dorsal surface of the distal phalanges of the thumb and index fingers of the tested hand. An opaque screen occluded the participant’s view of the dowel prior to the start of each trial. Audio and video were recorded of the experiment. The video camera was positioned to capture each participant’s side view, with the tested hand and eye level in the frame. Video recordings were stored for offline analyses.

A dowel rested horizontally on a cradle of a stand secured to the table. The dowel, positioned at 75% of the participant’s maximum arm reach, was centered to align with the participant’s acromion process. A target hole was centered in front of the apparatus at about 50% of the participant’s maximum reach. A taped line, positioned at 25% of the participant’s maximum reach, designated the starting position of the tested hand. Three electromagnetic markers were secured to the radial styloid and dorsal surface of the distal phalanges of the thumb and index fingers of the tested hand. An opaque screen (not pictured) occluded the participant’s view of the dowel. The video camera framed the tested hand and side view of the eyeline.