Spatial and temporal control of trunk-assisted prehensile actions

Area of Science:

• Neuroscience
• Biomechanics
• Human motor control

Background:

• Understanding the coordination between the arm and trunk during reaching and grasping is crucial for explaining human motor control.
• Previous research has focused on arm movements, but the role of the trunk in prehension is less understood.

Purpose of the Study:

• To investigate the spatial and temporal coupling between arm and trunk movements during a prehension task.
• To test the hypothesis of spatial regularity between grasp and transport components in trunk-assisted reaching.

Main Methods:

• Participants performed a trunk-assisted prehension task involving reaching for and grasping objects.
• Movement amplitude, reach speed, and object size were systematically varied.
• Kinematic data of arm and trunk segments were analyzed.

Main Results:

• Grip aperture formation showed spatial regularity, with peak aperture distance correlating with hand-path length.
• Temporal parameters, including time to peak aperture and peak velocities of arm and trunk, were influenced by object size and reach speed.
• The timing of peak trunk velocity was coupled with peak arm velocity and peak aperture time.

Conclusions:

• The trunk plays an integral role in modulating arm movements and grip aperture formation during prehension.
• Neuromotor synergies coordinate arm and trunk movements to ensure stable grip aperture for object grasping.
• Findings support a state-space control model for reach-to-grasp actions involving trunk kinematics.