Simultaneously varying back stiffness and trunk compression in a passive trunk exoskeleton during different activities: A pilot study.

Passive trunk exoskeletons support the human body with mechanical elements like springs and trunk compression, allowing them to guide motion and relieve the load on the spine. However, to provide appropriate support, elements of the exoskeleton (e.g., degree of compression) should be intelligently adapted to the current task. As it is not currently clear how adjusting different exoskeleton elements affects the wearer, this study preliminarily examines the effects of simultaneously adjusting both exoskeletal spinal column stiffness and trunk compression in a passive trunk exoskeleton. Six participants performed four dynamic tasks (walking, sit-to-stand, lifting a 20-lb box, lifting a 40-lb box) and experienced unexpected perturbations both without the exoskeleton and in six exoskeleton configurations corresponding to two compression levels and three stiffness levels. While results are preliminary due to the small sample size and relatively small increases in stiffness, they indicate that both compression and stiffness may affect kinematics and electromyography, that the effects may differ between activities, and that there may be interaction effects between stiffness and compression. As the next step, we will conduct a larger study with the same protocol more participants and larger stiffness increases to systematically evaluate the effects of different exoskeleton characteristics on the wearer.Clinical Relevance- Trunk exoskeletons can support wearers during a variety of different tasks, but their configuration may need to be intelligently adjusted to provide appropriate support. This pilot study provides information about the effects of exoskeleton back stiffness and trunk compression on the wearer, which can be used as a basis for more effective device design and usage.

Corrections to "A Pilot Study of Varying Thoracic and Abdominal Compression in a Reconfigurable Trunk Exoskeleton During Different Activities" [Jun 20 1585-1594].

Presents a corrected version of Table A-II in the above named paper.

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.

Design and Pilot Evaluation of a Reconfigurable Spinal Exoskeleton.

Low back pain is a leading cause of disability, and there is a tremendous need for nonsurgical, nonpharmaceutical interventions to manage it. Versatile spinal exoskeletons have been proposed as a method of supporting or augmenting the wearer, but experimental data from human subjects are limited, and the effects of such exoskeletons remain poorly understood. We thus present a prototype of a reconfigurable spinal exoskeleton that features easily adjustable resistance and compression at multiple spinal levels, allowing us to study the effect of different exoskeleton configurations on the body. In a pilot evaluation with a single subject, both thoracic and abdominal compression were found to affect trunk angle, low back moment and the electromyogram of the erector spinae, though different exoskeleton configurations had different effects during different tasks. This supports the premise that intelligent mechanical adjustments of a spinal exoskeleton are necessary for optimal support or augmentation of the wearer, though the results need to be examined in a larger, varied sample of subjects.