Skip to main content
Key Specialties
Cardiology Diabetology Endocrinology Gastroenterology Geriatrics and Gerontology Gynecology and Obstetrics Hematology Infectious Disease Internal Medicine Nephrology Neurology Oncology Pediatrics Respiratory Medicine Rheumatology Surgery
Congress Coverage
2024 ACC Congress 2023 ESMO Congress 2023 EASD Congress 2023 ERS Congress 2023 ESC Congress
Clinical Collections
Advances in Alzheimer’s

At a glance: The STEP trials

A round-up of the STEP phase 3 clinical trials evaluating semaglutide for weight loss in people with overweight or obesity.
ADVANCED SEARCH
Log in
Top
Journal of NeuroEngineering and Rehabilitation
Published in: Journal of NeuroEngineering and Rehabilitation 1/2017

Open Access 01-12-2017 | Research

Reducing the metabolic cost of walking with an ankle exoskeleton: interaction between actuation timing and power

Authors: Samuel Galle, Philippe Malcolm, Steven Hartley Collins, Dirk De Clercq

Published in: Journal of NeuroEngineering and Rehabilitation | Issue 1/2017

Login to get access

Abstract

Background

Powered ankle-foot exoskeletons can reduce the metabolic cost of human walking to below normal levels, but optimal assistance properties remain unclear. The purpose of this study was to test the effects of different assistance timing and power characteristics in an experiment with a tethered ankle-foot exoskeleton.

Methods

Ten healthy female subjects walked on a treadmill with bilateral ankle-foot exoskeletons in 10 different assistance conditions. Artificial pneumatic muscles assisted plantarflexion during ankle push-off using one of four actuation onset timings (36, 42, 48 and 54% of the stride) and three power levels (average positive exoskeleton power over a stride, summed for both legs, of 0.2, 0.4 and 0.5 W∙kg−1). We compared metabolic rate, kinematics and electromyography (EMG) between conditions.

Results

Optimal assistance was achieved with an onset of 42% stride and average power of 0.4 W∙kg−1, leading to 21% reduction in metabolic cost compared to walking with the exoskeleton deactivated and 12% reduction compared to normal walking without the exoskeleton. With suboptimal timing or power, the exoskeleton still reduced metabolic cost, but substantially less so. The relationship between timing, power and metabolic rate was well-characterized by a two-dimensional quadratic function. The assistive mechanisms leading to these improvements included reducing muscular activity in the ankle plantarflexors and assisting leg swing initiation.

Conclusions

These results emphasize the importance of optimizing exoskeleton actuation properties when assisting or augmenting human locomotion. Our optimal assistance onset timing and average power levels could be used for other exoskeletons to improve assistance and resulting benefits.
Appendix
Available only for authorised users
Footnotes
1
Normal walking is used to refer to walking without an exoskeleton. Active exoskeletons refer to exoskeletons which use external energy to assist walking while passive exoskeletons store and re-use energy which is generated by the user and thus do not need external energy input. Powered walking refers to walking with exoskeleton assistance (both for passive and active exoskeleton assistance). Walking with the exoskeleton without assistance of the device (e.g. with the assistive spring disengaged for passive devices or without active assistance for active devices) is referred to as walking with zero-work instead of ‘unpowered’ exoskeleton walking (e.g. [3, 10]) to avoid confusion when concerning passive exoskeletons [5]. Tethered exoskeletons refer to a connection with off-board hardware or power source. Autonomous exoskeletons refer to devices were all hardware and power sources are carried by the user.
 
Literature
1.
Mitchell C. Pedestrian mobility and safety: a key to independence for older people. Top Geriatr Rehabil. 2006;22:2006.CrossRef
2.
Cavagna G, Heglund N. Mechanical work in terrestrial locomotion: two basic mechanisms for minimizing energy expenditure. Am J Physiol. 1977;233:R243–61.PubMed
3.
Malcolm P, Derave W, Galle S, De Clercq D. A simple exoskeleton that assists plantarflexion can reduce the metabolic cost of human walking. PLoS One. 2013;8:e56137.CrossRefPubMedPubMedCentral
4.
Mooney LM, Herr HM. Biomechanical walking mechanisms underlying the metabolic reduction caused by an autonomous exoskeleton. J Neuroeng Rehabil. 2016;13:1–12.CrossRef
5.
6.
7.
Gregorczyk KN, Hasselquist L, Schiffman JM, Bensel CK, Obusek JP, Gutekunst DJ. Effects of a lower-body exoskeleton device on metabolic cost and gait biomechanics during load carriage. Ergonomics. 2010;53:1263–75.CrossRefPubMed
8.
Quinlivan BT, Sangjun L, Malcolm P, Rossi DM, Grimmer M, Siviy C, et al. Assistance magnitude vs. metabolic cost reductions for a tethered multiarticular soft exosuit. Sci Robot. 2017;2:eaah4416.CrossRef
9.
Jackson RW, Collins SH. An experimental comparison of the relative benefits of work and torque assistance in ankle exoskeletons. J Appl Physiol. 2015;119:541–57.CrossRefPubMed
10.
Sawicki GS, Ferris DP. Mechanics and energetics of level walking with powered ankle exoskeletons. J Exp Biol. 2008;211:1402–13.CrossRefPubMed
11.
Sawicki GS, Ferris DP. Powered ankle exoskeletons reveal the metabolic cost of plantar flexor mechanical work during walking with longer steps at constant step frequency. J Exp Biol. 2009;212:21–31.CrossRefPubMed
12.
Koller JR, Jacobs DA, Ferris DP, Remy CD. Learning to walk with an adaptive gain proportional myoelectric controller for a robotic ankle exoskeleton. J Neuroeng Rehabil. 2015;12:97.CrossRefPubMedPubMedCentral
13.
Kuo AD. Energetics of actively powered locomotion using the simplest walking model. J Biomech Eng. 2002;124:113.CrossRefPubMed
14.
15.
Zelik KE, Huang TWP, Adamczyk PG, Kuo AD. The role of series ankle elasticity in bipedal walking. J Theor Biol. 2014;346:75–85.CrossRefPubMed
16.
Robertson BD, Farris DJ, Sawicki GS. More is not always better: modeling the effects of elastic exoskeleton compliance on underlying ankle muscle-tendon dynamics. Bioinspir Biomim. 2014;9:46018.CrossRef
17.
Galle S, Malcolm P, Derave W, De Clercq D. Uphill walking with a simple exoskeleton: plantarflexion assistance leads to proximal adaptations. Gait Posture. 2015;41:246–51.CrossRefPubMed
18.
Galle S, Malcolm P, Derave W, De Clercq D. Adaptation to walking with an exoskeleton that assists ankle extension. Gait Posture. 2013;38:495–9.CrossRefPubMed
19.
Galle S, Malcolm P, Derave W, De Clercq D. Enhancing performance during inclined loaded walking with a powered ankle-foot exoskeleton. Eur J Appl Physiol. 2014;114:2341–51.CrossRefPubMed
20.
Galle S, Derave W, Bossuyt F, Calders P, Malcolm P, De Clercq D. Exoskeleton plantarflexion assistance for elderly. Gait Posture. 2017;52:183–8.CrossRefPubMed
21.
Malcolm P, Quesada RE, Caputo JM, Collins SH. The influence of push-off timing in a robotic ankle-foot prosthesis on the energetics and mechanics of walking. J Neuroeng Rehabil. 2015;12:14.CrossRef
22.
Hermens HJ, Freriks B, Disselhorst-Klug C, Rau G. Development of recommendations for SEMG sensors and sensor placement procedures. J Electromyogr Kinesiol. 2000;10:361–74.CrossRefPubMed
23.
Donelan JM, Kram R, Kuo AD. Mechanical and metabolic determinants of the preferred step width in human walking. Proc R Soc Lond B. 2001;268:1985–92.CrossRef
24.
Dempster WT. Space requirements of the seated operator. WADC Tech Rep. Dayton: Wright Patterson Air Force Base; 1955. p. 55–159.
25.
O’Connor CM, Thorpe SK, O’Malley MJ, Vaughan CL. Automatic detection of gait events using kinematic data. Gait Posture. 2007;25:469–74.CrossRefPubMed
26.
Kuo AD, Donelan JM, Ruina A. Energetic consequences of walking like an inverted pendulum: step-to-step transitions. Exerc Sport Sci Rev. 2005;33:88–97.CrossRefPubMed
27.
Donelan JM, Kram R, Kuo AD. Mechanical work for step-to-step transitions is a major determinant of the metabolic cost of human walking. J Exp Biol. 2002;205:3717–27.PubMed
28.
Adamczyk PG, Collins SH, Kuo AD. The advantages of a rolling foot in human walking. J Exp Biol. 2006;209:3953–63.CrossRefPubMed
29.
30.
31.
Winiarski S, Rutkowska-Kucharska A. Estimated ground reaction force in normal and pathological gait. Acta Bioeng Biomech. 2009;11:53–60.PubMed
32.
Donelan JM, Kram R, Kuo AD. Simultaneous positive and negative external mechanical work in human walking. J Biomech. 2002;35:117–24.CrossRefPubMed
33.
Glantz SA. Primer of biostatistics. New York: McGraw-Hill Medical; 2012. p. 65–7.
34.
De Luca CJ, Merletti R. Surface myoelectric signal cross-talk among muscles of the leg. Electroencephalogr Clin Neurophysiol. 1988;69:568–75.CrossRefPubMed
35.
Handford ML, Srinivasan M. Robotic lower limb prosthesis design through simultaneous computer optimizations of human and prosthesis costs. Sci Rep. 2016;6:19983.CrossRefPubMedPubMedCentral
36.
37.
Winter D. Biomechanics and motor control of human gait: normal, elderly and pathological. Waterloo: Waterloo Biomechanics; 1991.
38.
Lipfert SW, Günther M, Renjewski D, Seyfarth A. Impulsive ankle push-off powers leg swing in human walking. J Exp Biol. 2014;217:1218–28.CrossRefPubMed
39.
van Dijk W, Meijneke C, van der Kooij H. Evaluation of the Achilles ankle exoskeleton. IEEE Trans Neural Syst Rehabil Eng. 2016;99:PP1.
40.
41.
Seo K, Lee J, Lee Y, Ha T, Shim Y. Fully autonomous hip exoskeleton saves metabolic cost of walking. Stockholm: Proceedings of the IEEE International Conference on Robotics and Automation (ICRA); 2016. p. 4628–35.
42.
Young A, Foss J, Gannon H, Ferris DP. Influence of power delivery timing on the energetics and biomechanics of humans wearing a hip exoskeleton. Front Bioeng Biotechnol. 2017;5:4.CrossRefPubMedPubMedCentral
43.
Witte KA, Zhang J, Jackson RW, Collins SH. Design of two lightweight, high-bandwidth torque-controlled ankle exoskeletons. Seattle: Proceedings of the IEEE International Conference on Robotics and Automation (ICRA); 2015. p. 1223–8.
44.
Norris JA, Marsh A, Granata KP. Powered ankle-foot orthoses: efficiency at the expense of decreased stability? J Biomech. 2007;40:S2.CrossRef
45.
Farris DJ, Robertson BD, Sawicki GS. Elastic ankle exoskeletons reduce soleus muscle force but not work in human hopping. J Appl Physiol. 2013;115:579–85.CrossRefPubMed
46.
Felt W, Selinger JC, Donelan JM, Remy CD. “Body-in-the-loop”: optimizing device parameters using measures of instantaneous energetic cost. PLoS One. 2015;10:e0135342.CrossRefPubMedPubMedCentral
47.
Koller JR, Gates DH, Ferris DP, Remy CD. Confidence in the curve: establishing instantaneous cost mapping techniques using bilateral ankle exoskeletons. J Appl Physiol. 2017;122:242–52.CrossRefPubMed
48.
Koller JR, Gates DH, Ferris DP, Remy CD. “Body-in-the-Loop” Optimization of Assistive Robotic Devices: A Validation Study. Ann Arbor: Proceedings of Robotics: Science and Sustems; 2016.
49.
van Dijk W, van der Kooij H. Optimization of human walking for exoskeletal support. Seattle: Proceedings of the IEEE Int Conf Rehabil Robot; 2013.
Metadata
Title
Reducing the metabolic cost of walking with an ankle exoskeleton: interaction between actuation timing and power
Authors
Samuel Galle
Philippe Malcolm
Steven Hartley Collins
Dirk De Clercq
Publication date
01-12-2017
Publisher
BioMed Central
Published in
Journal of NeuroEngineering and Rehabilitation / Issue 1/2017
Electronic ISSN: 1743-0003
DOI
https://doi.org/10.1186/s12984-017-0235-0

Other articles of this Issue 1/2017

Journal of NeuroEngineering and Rehabilitation 1/2017 Go to the issue

Research

Kinesthetic deficits after perinatal stroke: robotic measurement in hemiparetic children

Review

Robot-assisted assessment of muscle strength

Research

Effects of somatosensory electrical stimulation on motor function and cortical oscillations

Review

Sensorimotor Learning: Neurocognitive Mechanisms and Individual Differences

Research

Overground vs. treadmill-based robotic gait training to improve seated balance in people with motor-complete spinal cord injury: a case report

Research

Changes in tibialis anterior architecture affect the amplitude of surface electromyograms