Potential of Individual Upper-Limb Muscles to Contribute to Postural Tremor: Simulations From Neural Drive to Joint...

Area of Science:

• Biomechanics
• Neuroscience
• Human Movement Science

Background:

• Identifying key muscles for tremor suppression is crucial but challenging.
• Previous biomechanical models of upper-limb tremor were limited in scope (≤15 muscles).
• Understanding muscle contributions to tremor requires comprehensive biomechanical analysis.

Purpose of the Study:

• To expand previous upper-limb biomechanical models to include 50 muscles.
• To simulate tremor propagation and identify muscles with the highest potential to generate tremor.
• To test previously postulated principles of tremor generation and discover new insights.

Main Methods:

• Developed an expanded biomechanical model incorporating 50 upper-limb muscles.
• Simulated tremor propagation by analyzing input-output gains between neural drive and joint rotations.
• Performed robustness and sensitivity analyses to evaluate model parameter variability effects.

Main Results:

• Confirmed previous principles regarding tremor generation.
• Identified biceps, forearm, and wrist muscles as having the largest gains across various postures.
• Discovered that tremor gains are posture-dependent, with some shoulder and hand muscles also showing significant contributions in specific positions.

Conclusions:

• The expanded model validates prior findings and offers new insights into tremor biomechanics.
• Biceps, forearm, and wrist muscles, along with forearm and wrist degrees-of-freedom (DOF), are primary targets for tremor suppression.
• These findings provide a basis for developing more effective peripheral tremor suppression strategies.