Reaching and grasping are often completed while walking, yet the interlimb coordination required for such a combined task is not fully understood. Previous studies have produced contradictory evidence regarding preference for support of the lower limb ipsilateral or contralateral to the upper limb when performing a reaching task. This coordinative aspect of the combined task provides insight into whether the two tasks are mutually modified or if the reach is superimposed upon normal arm swinging. Collectively, 18 right-handed young adults walked slower, took shorter steps, and spent more time in double support during the combined task compared with walking alone. The peak grasp aperture was larger in walking reach-to-grasp trials compared with standing trials. There was not a strong trend for lower limb support preferences at the reach initiation or object contact. The participants could begin walking with either foot and demonstrated variability of preferred gait initiation patterns. There was a range of interlimb coordination patterns, none of which could be generalized to all young adults. The variability with which healthy right-handed young adults execute a combined walking reach-to-grasp task suggests that the cyclical (walking) and discrete (prehension) motor tasks may have separate motor control mechanisms, as proposed in the two primitives theory.
Bellinger, Pickett, and Mason are with the Department of Kinesiology, University of Wisconsin–Madison, Madison, WI. Bellinger is also with the Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, IL. Pickett is also with the Occupational Therapy Program, University of Wisconsin–Madison, Madison, WI.
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