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.

Toward real-world evaluations of trunk exoskeletons using inertial measurement units.

Trunk exoskeletons are an emerging technology that could reduce spinal loading, guide trunk motion, and augment lifting ability. However, while they have achieved promising results in brief laboratory studies, they have not yet been tested in longer-term real-world studies - partially due to reliance on stationary sensors such as cameras. To enable future real-world evaluations of trunk exoskeletons, this paper describes two preliminary studies on using inertial measurement units (IMUs) to collect kinematic data from an exoskeleton wearer. In the first study, a participant performed three activities (walking, sit-to-stand, box lifting) while trunk flexion angle was measured with both IMUs and reference cameras. The mean absolute difference in flexion angle between the two methods was 1.4° during walking, 3.6° during sit-to-stand and 5.2° during box lifting, showing that IMUs can measure trunk flexion with a reasonable accuracy. In the second study, six participants performed five activities (standing, sitting straight, slouching, 'good' lifting, 'bad' lifting), and a naïve Bayes classifier was used to automatically classify the activity from IMU data. The classification accuracy was 92.2%, indicating the feasibility of automated activity classification using IMUs. The IMUs will next be used to obtain longer-term recordings of different activities performed both with and without a trunk exoskeleton to determine how the exoskeleton affects a person's posture and behavior.

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.