Comparison of the human-exosuit interaction using ankle moment and ankle positive power inspired walking assistance

Author(s)

Grimmer, Martin ^[1] ; Quinlivan, Brendan T. ^{[2, 3]} ; Lee, Sangjun ^{[2, 3]} ; Malcolm, Philippe ^{[4, 5]} ; Rossi, Denise Martineli ^[6] ; Siviy, Christopher ^{[2, 3]} ; Walsh, Conor J. ^{[2, 3]}

Affiliation

^[1] Tech Univ Darmstadt, Inst Sports Sci, Magdalenenstr 27, D-64289 Darmstadt - Germany

^[2] Harvard Univ, John A Paulson Sch Engn & Appl Sci, Cambridge, MA 02138 - USA

^[3] Harvard Univ, Wyss Inst Biol Inspired Engn, Cambridge, MA 02138 - USA

^[4] Univ Nebraska, Dept Biomech, Omaha, NE 68182 - USA

^[5] Univ Nebraska, Ctr Res Human Movement Variabil, Omaha, NE 68182 - USA

^[6] Univ Sao Paulo, Dept Hlth Sci, Ribeirao Preto Med Sch, Ribeirao Preto, SP - Brazil

• Document type: Journal article
• Source: JOURNAL OF BIOMECHANICS; v. 83, p. 76-84, JAN 23 2019.
• Web of Science Citations: 3

Abstract

Previous ankle exoskeleton assistance techniques that were able to demonstrate metabolic reductions can be categorized into those that delivered moment profiles similar to the biological ankle moment throughout the stance phase, and others that delivered positive power only during push off. Both assistance techniques and a powered-off condition were compared in treadmill walking (1.5 m s(-1)) with a soft exosuit. We hypothesized that both techniques can result in a similar metabolic reduction when providing a similar level of average positive exosuit power at each ankle (0.12 W kg(-1)) and hip (0.02 W kg(-1)) while the underlying global center-of-mass and local joint biomechanics would be different. We found a similar net metabolic rate reduction of 15% relative to walking with the suit powered-off for both techniques. The ankle moment inspired technique showed larger magnitudes of reductions for biological moment and power at the hip and the ankle. The ankle power inspired technique might benefit from higher biological efficiency, when reducing positive instead of negative power at the knee and when almost keeping the isometric function of the plantarflexors before push-off. Changes at the ankle caused energetic reductions at the knee, hip and the center-of-mass. A major contribution to metabolic reduction might be based on them. As the lower limb biomechanics that led to these reductions were different, we believe that humans alter their gait to maximize their energetic benefit based on the exosuit assistance. For further insights on mechanisms that lead to metabolic reduction, joint mechanics and muscle-tendon dynamics must be analyzed in combination. (C) 2018 The Authors. Published by Elsevier Ltd. (AU)

• FAPESP's process: 15/02116-1 - Investigating musculoskeletal implications of wearing a soft exosuit
• Grantee: Denise Martineli Rossi
• Support type: Scholarships abroad - Research Internship - Doctorate