A musculotendon contribution for multijoint hand control.

Area of Science:

• Biomechanics
• Motor Control
• Human Movement Science

Background:

• Multijoint arm control relies on intersegmental dynamics.
• Understanding musculotendon properties is crucial for coordinated movements.

Purpose of the Study:

• To investigate the contribution of viscoelastic musculotendon properties to coordinated hand movements.
• To quantify the role of passive stiffness torque in joint torque generation.

Main Methods:

• Analysis of two-link planar arm dynamics.
• Modeling of coordinated wrist and finger movements.
• Quantification of passive stiffness torque during repetitive motions.

Main Results:

• Musculotendon passive stiffness torque constitutes over 90% of total passive torque.
• Joint torque contribution varied significantly based on in-phase vs. out-of-phase wrist-finger movements (24 N-cm vs. 6 N-cm peak-to-peak).
• Movement variance remained consistent across different coordination patterns with similar angular excursions.

Conclusions:

• Viscoelastic musculotendon properties are a dominant factor in passive joint torque during arm movement.
• The neural controller likely adapts to interactive musculotendon torque to achieve task-specific hand impedance.
• Coordination patterns influence torque dynamics, but not necessarily movement outcome variability.