A Simple Exoskeleton That Assists Plantarflexion Can Reduce the Metabolic Cost of Human Walking

Philippe Malcolm, Wim Derave, Samuel Galle, Dirk De Clercq

Research output: Contribution to journalArticle

140 Citations (Scopus)

Abstract

Background: Even though walking can be sustained for great distances, considerable energy is required for plantarflexion around the instant of opposite leg heel contact. Different groups attempted to reduce metabolic cost with exoskeletons but none could achieve a reduction beyond the level of walking without exoskeleton, possibly because there is no consensus on the optimal actuation timing. The main research question of our study was whether it is possible to obtain a higher reduction in metabolic cost by tuning the actuation timing. Methodology/Principal Findings: We measured metabolic cost by means of respiratory gas analysis. Test subjects walked with a simple pneumatic exoskeleton that assists plantarflexion with different actuation timings. We found that the exoskeleton can reduce metabolic cost by 0.18±0.06 W kg-1 or 6±2% (standard error of the mean) (p = 0.019) below the cost of walking without exoskeleton if actuation starts just before opposite leg heel contact. Conclusions/Significance: The optimum timing that we found concurs with the prediction from a mathematical model of walking. While the present exoskeleton was not ambulant, measurements of joint kinetics reveal that the required power could be recycled from knee extension deceleration work that occurs naturally during walking. This demonstrates that it is theoretically possible to build future ambulant exoskeletons that reduce metabolic cost, without power supply restrictions.

Original languageEnglish (US)
Article numbere56137
JournalPloS one
Volume8
Issue number2
DOIs
StatePublished - Feb 13 2013

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exoskeleton
walking
Walking
Costs and Cost Analysis
Costs
Heel
Leg
legs
Electric Power Supplies
Gas fuel analysis
Deceleration
respiratory gases
knees
Pneumatics
Knee
Theoretical Models
Tuning
Joints
Gases
Mathematical models

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

Cite this

A Simple Exoskeleton That Assists Plantarflexion Can Reduce the Metabolic Cost of Human Walking. / Malcolm, Philippe; Derave, Wim; Galle, Samuel; De Clercq, Dirk.

In: PloS one, Vol. 8, No. 2, e56137, 13.02.2013.

Research output: Contribution to journalArticle

Malcolm, Philippe ; Derave, Wim ; Galle, Samuel ; De Clercq, Dirk. / A Simple Exoskeleton That Assists Plantarflexion Can Reduce the Metabolic Cost of Human Walking. In: PloS one. 2013 ; Vol. 8, No. 2.
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