End-state comfort and joint configuration variance during reaching

Area of Science:

• Motor control
• Cognitive psychology
• Biomechanics

Background:

• Two main approaches to motor control exist: task-specific constraints from cognitive psychology and multi-element synergies from the principle of motor abundance.
• These approaches have typically been studied independently, focusing on comfort ratings or joint configuration variance, respectively.

Purpose of the Study:

• To integrate cognitive psychology and motor abundance principles in understanding motor control.
• To investigate the relationship between perceived comfort and joint configuration variance during goal-directed movements.

Main Methods:

• Participants performed pointing movements to targets in the frontal plane.
• Comfort ratings of final postures were collected.
• Joint configuration variance was quantified in relation to pointer endpoint position and orientation.

Main Results:

• Consistent comfort ratings were observed across different targets.
• All movements demonstrated multi-joint synergies stabilizing pointer position and orientation.
• Less comfortable postures showed higher joint configuration variance than more comfortable ones, contrary to expectations.

Conclusions:

• Multi-joint synergies effectively stabilized pointer endpoint position and orientation across varying comfort levels.
• The study integrates comfort perception with motor abundance principles, suggesting complex interactions in motor control.
• Findings challenge the assumption that greater comfort correlates with lower joint variance.