A Pilot Study of Varying Thoracic and Abdominal Compression in a Reconfigurable Trunk Exoskeleton During Different Activities

Objective: Trunk exoskeletons are a new technology with great promise for human rehabilitation, assistance and augmentation. However, it is unclear how different exoskeleton features affect the wearer's body during different activities. This study thus examined how varying a trunk exoskeleton's thoracic and abdominal compression affects trunk kinematics and muscle demand during several activities. Methods: We developed a trunk exoskeleton that allows thoracic and abdominal compression to be changed quickly and independently. To evaluate the effect of varying compression, 12 participants took part in a two-session study. In the first session, they performed three activities (walking, sit-to-stand, lifting a box). In the second session, they experienced unexpected perturbations while sitting. This was done both without the exoskeleton and in four exoskeleton configurations with different thoracic and abdominal compression levels. Trunk flexion angle, low back extension moment and the electromyogram of the erector spinae and rectus abdominis were measured in both sessions. Results: Different exoskeleton compression levels resulted in significantly different peak trunk flexion angles and peak electromyograms of the erector spinae. However, the effects of compression differed significantly between activities. Conclusion: Our results indicate that a trunk exoskeleton's thoracic and abdominal compression affect the wearer's kinematics and muscle demand; furthermore, a single compression configuration is not appropriate for all activities. Significance: The study suggests that future trunk exoskeletons should either be able to vary their compression levels to suit different activities or should have the compression designed for a specific activity in order to be beneficial to the wearer.