Muscular, temporal, and spatial responses to shoulder exosuit assistance during functional tasks

Area of Science:

• Robotics
• Biomechanics
• Human-Computer Interaction

Background:

• Shoulder exosuits show potential for assisting individuals with neuromuscular impairments in daily activities.
• Limited research exists on how humans adapt their movements when using shoulder exosuits.
• Understanding human adaptation is crucial for optimizing exosuit design and effectiveness.

Purpose of the Study:

• To evaluate the impact of a cable-driven shoulder exosuit on muscle activity and kinematics during reaching and drinking tasks.
• To quantify motor learning and adaptation in healthy subjects using the shoulder exosuit.
• To provide insights into human-exosuit interaction principles for future development.

Main Methods:

• Developed a cable-driven shoulder exosuit for assistance during upper limb movements.
• Recruited 18 healthy subjects to perform reaching and drinking tasks with and without exosuit assistance.
• Quantified changes in muscle activity (electromyography) and joint kinematics.
• Assessed learning through changes in movement duration and actuator switch timing over multiple trials.

Main Results:

• The shoulder exosuit significantly reduced mean and integrated muscle activity in the anterior, middle, and posterior deltoid muscles.
• Exosuit assistance led to kinematic adaptations, with subjects allowing their arms to follow assistive forces.
• Subjects demonstrated learning by reducing movement duration and activating the exosuit actuator earlier with practice.
• Reduced movement duration correlated with decreased integrated muscle activity across deltoid muscles.

Conclusions:

• Shoulder exosuits effectively reduce muscle effort during functional tasks, indicating their potential to enhance independence for individuals with neuromuscular impairments.
• Observed kinematic responses and learning adaptations highlight key principles for human-exosuit interaction.
• Findings inform future exosuit designs by demonstrating how users adapt to and learn to utilize assistive robotic devices.