How Changes in Muscle Activity and Range of Motion Represent User Perceptions of Back-Support Exoskeleton Performance

Area of Science:

• Biomechanics
• Human-Computer Interaction
• Wearable Technology

Background:

• Objective metrics for exoskeleton performance lack alignment with user perception.
• Understanding user perception is crucial for developing effective soft back-support exoskeletons.

Purpose of the Study:

• Investigate relationships between muscle activity, joint kinematics, and user perceptions (comfort, support, pain, mobility, overall experience) of soft back-support exoskeletons.
• Examine how user preferences across subjective factors influence exoskeleton selection.
• Assess the alignment between subjective feedback and objective biomechanical metrics.

Main Methods:

• Ten able-bodied individuals performed trunk bending and weight-lifting tasks with various soft back-support exoskeleton configurations.
• Recorded lower back muscle activity and trunk/knee joint kinematics using wearable sensors.
• Quantified similarity between subjective feedback and objective metrics using a similarity index.

Main Results:

• User perceptions of comfort, pain absence, and mobility restriction showed high consistency (>90%).
• Participants preferred low-strength bands for comfort and mobility, but high-strength for biomechanical support.
• Exoskeleton selections represented a compromise between comfort and support preferences.
• Comfort, pain absence, and mobility were strongly linked to trunk range of motion (p < 0.01).
• Muscle activity partially reflected perceived support (median similarity 73.7% for bending, 63.6% for lifting).

Conclusions:

• User perception of soft back-support exoskeletons is multifaceted, encompassing comfort, pain, and mobility.
• Exoskeleton selection involves balancing competing user preferences for comfort and biomechanical support.
• Trunk range of motion is a significant objective correlate of key user perceptions.
• Muscle activity offers some insight into perceived support, but user experience is complex.
• Findings provide a foundation for aligning objective biomechanical metrics with subjective user experience in exoskeleton design.