A passive upper limb exoskeleton effectively reduces shoulder muscle activity over a large shoulder workspace

Area of Science:

• Ergonomics and Human Factors
• Biomechanics
• Occupational Health

Background:

• Industrial upper limb exoskeletons aim to prevent shoulder musculoskeletal disorders by reducing muscle load during overhead tasks.
• Existing research primarily focuses on exoskeleton support for overhead work, leaving a gap in understanding their effectiveness across a broader shoulder workspace.

Purpose of the Study:

• To evaluate the support provided by the Ottobock Paexo Shoulder exoskeleton across a wide range of shoulder movements, from overhead to hip height.
• To assess the impact of varying exoskeleton support levels on muscle activity, upper body kinematics, and user subjective feedback during static and dynamic tasks.

Main Methods:

• Utilized 3D motion capture and surface electromyography (EMG) to record upper body kinematics and muscle activity.
• Collected subjective user feedback via questionnaires on comfort and perceived support.
• Compared performance with no exoskeleton, a disengaged exoskeleton, and two levels of exoskeleton support (moderate and high) during tasks with an electric screwdriver.

Main Results:

• Exoskeleton support significantly reduced deltoid muscle activity in abducted shoulder postures, including non-overhead positions (-9 to -24%).
• Modest kinematic changes were observed (decreased shoulder flexion, increased abduction), but dynamic movement patterns remained unaffected.
• Increased exoskeleton support led to greater objective effects but also increased subjective perception of change and decreased perceived comfort.

Conclusions:

• The Ottobock Paexo Shoulder provides biomechanical support beyond traditional overhead tasks.
• A trade-off exists between the level of exoskeleton assistance and user comfort, suggesting a need for optimized human-exoskeleton interaction.
• Further development is necessary to enhance user-exoskeleton synergy for effective long-term prevention of musculoskeletal disorders in industrial settings.