The energetic effect of hip flexion and retraction in walking at different speeds: a modeling study

Jian Jin, Dinant Kistemaker, Jaap H. van Dieën, Andreas Daffertshofer, Sjoerd M. Bruijn*

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

In human walking, power for propulsion is generated primarily via ankle and hip muscles. The addition of a ‘passive’ hip spring to simple bipedal models appears more efficient than using only push-off impulse, at least, when hip spring associated energetic costs are not considered. Hip flexion and retraction torques, however, are not ‘free’, as they are produced by muscles demanding metabolic energy. Studies evaluating the inclusion of hip actuation costs, especially during the swing phase, and the hip actuation’s energetic benefits are few and far between. It is also unknown whether these possible benefits/effects may depend on speed. We simulated a planar flat-feet model walking stably over a range of speeds. We asked whether the addition of independent hip flexion and retraction remains energetically beneficial when considering work-based metabolic cost of transport (MCOT) with different efficiencies of doing positive and negative work. We found asymmetric hip actuation can reduce the estimated MCOT relative to ankle actuation by up to 6%, but only at medium speeds. The corresponding optimal strategy is zero hip flexion and some hip retraction actuation. The reason for this reduced MCOT is that the decrease in collision loss is larger than the associated increase in hip negative work. This leads to a reduction in total positive mechanical work, which results in an overall lower MCOT. Our study shows how ankle actuation, hip flexion, and retraction actuation can be coordinated to reduce MCOT.

Original languageEnglish
Article numbere14662
Pages (from-to)1-22
Number of pages22
JournalPeerJ
Volume11
DOIs
Publication statusPublished - 18 Jan 2023

Bibliographical note

Funding Information:
Sjoerd M. Bruijn and Jian Jin are funded by a VIDI grant no. (016.Vidi.178.014) from the Dutch Organization for Scientific Research (NWO). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Publisher Copyright:
Copyright 2023 Jin et al.

Funding

Sjoerd M. Bruijn and Jian Jin are funded by a VIDI grant no. (016.Vidi.178.014) from the Dutch Organization for Scientific Research (NWO). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Keywords

  • Ankle push-off
  • Dynamic walker
  • Energetics
  • Hip flexion
  • Hip retraction
  • Metabolic cost
  • Modeling approach

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