Evidence of Motor Equivalence in a Pointing Task Involving Locomotion

Abstract

A pointing task was performed both while subjects stood beside and while subjects walked past targets that involved differing movement amplitudes and differing sizes. The hand kinematics were considered relative both to a fixed frame of reference in the movement environment (end effector kinematics) and to the subject's body (kinematics of the hand alone). From the former view, there were few differences between standing and walking versions of the task, indicating similarity of the kinematics of the hand. However, when the hand was considered alone, marked differences in the kinematics and spatial trajectories between standing and walking were achieved. Furthermore, kinematic analyses of the trunk showed that subjects used differing amounts of both flexion-extension and rotation movements at the waist depending on whether they were standing or walking as well as on the constraints imposed by target width and movement amplitude. The present results demonstrate the existence of motor equivalence in a combined upper and lower extremity task and that this motor equivalence is a control strategy to cope with increasing task demands. Given the complexity involved in controlling the arm, the torso, and the legs (during locomotion), the movements involved in the present tasks appear to be planned and controlled by considering the whole body as a single unit.

Effects of Speed and Visual-Target Distance on Toe Trajectory during the Swing Phase of Treadmill Walking

“…It has been reported that there were no significant differences in the ground reaction forces when subjects visually "targeted" a force plate on a walkway and when they did not [20,21]. However, performing a task during walking has been shown to affect body kinematics, either during manual pointing tasks [22] or visual tasks [15,16]. For instance, subjects walking on a treadmill exhibit an 11% increase in knee flexion just after heel strike while reading 5-digit numbers on a computer screen positioned 4 meters away as opposed to simply staring at a dot at the same distance [16].…”

Coordinating degrees of freedom during interceptive actions in children

“…Trunk contribution to the reaching movement was examined using a methodology first reported by Marteniuk and colleagues (Marteniuk et al 2000;Marteniuk and Bertram 2001), which involved calculating the wrist coordinates from both world-centered and body-centered Significant differences between the two factors, condition and frame of reference, after post hoc analysis; where two conditions have the same superscript there was no significant difference for that variable frames of reference. This analysis revealed that children exhibited a different coordination between the trunk and arm in the three reach and grasp conditions.…”

“…To calculate the data relative to a dynamic, body-centered frame of reference, the trunk (sternum marker) coordinates were subtracted from the wrist coordinates. The latter allowed the determination of the extent to which the body movement contributed to the movement of the hand (Marteniuk et al 2000). Trunk contribution was quantified by calculating the excursion of trunk flexion/extension and trunk rotation.…”

“…With adults participants, Marteniuk and colleagues (Marteniuk et al 2000;Marteniuk and Bertram 2001) demonstrated that the amount of trunk flexion and rotation varied according to whether they reached during standing or during locomotion. This finding required the use of a novel analysis procedure in which the movement of the hand was compared relative to a fixed, world-centered frame of reference (normally used in prehension research), and to a body-centered frame of reference (i.e., the trunk).…”

“…The current experiment was designed to examine this issue. To this end, we compared children's movements from a world-centered to a body-centered frame of reference (Marteniuk et al 2000), as they reached for a stationary ball while standing (condition C1) and walking (C2), and for a moving ball while standing (C3).…”