Journal article
The effects of ankle stiffness on mechanics and energetics of walking with added loads: a prosthetic emulator study
Journal of neuroengineering and rehabilitation, Vol.16(1), pp.148-148
11/21/2019
DOI: 10.1186/s12984-019-0621-x
PMCID: PMC6873504
PMID: 31752942
Abstract
Background The human ankle joint has an influential role in the regulation of the mechanics and energetics of gait. The human ankle can modulate its joint 'quasi-stiffness' (ratio of plantarflexion moment to dorsiflexion displacement) in response to various locomotor tasks (e.g., load carriage). However, the direct effect of ankle stiffness on metabolic energy cost during various tasks is not fully understood. The purpose of this study was to determine how net metabolic energy cost was affected by ankle stiffness while walking under different force demands (i.e., with and without additional load). Methods Individuals simulated an amputation by using an immobilizer boot with a robotic ankle-foot prosthesis emulator. The prosthetic emulator was controlled to follow five ankle stiffness conditions, based on literature values of human ankle quasi-stiffness. Individuals walked with these five ankle stiffness settings, with and without carrying additional load of approximately 30% of body mass (i.e., ten total trials). Results Within the range of stiffness we tested, the highest stiffness minimized metabolic cost for both load conditions, including a 3% decrease in metabolic cost for an increase in stiffness of about 0.0480 Nm/deg/kg during normal (no load) walking. Furthermore, the highest stiffness produced the least amount of prosthetic ankle-foot positive work, with a difference of 0.04 J/kg from the highest to lowest stiffness condition. Ipsilateral hip positive work did not significantly change across the no load condition but was minimized at the highest stiffness for the additional load conditions. For the additional load conditions, the hip work followed a similar trend as the metabolic cost, suggesting that reducing positive hip work can lower metabolic cost. Conclusion While ankle stiffness affected the metabolic cost for both load conditions, we found no significant interaction effect between stiffness and load. This may suggest that the importance of the human ankle's ability to change stiffness during different load carrying tasks may not be driven to minimize metabolic cost. A prosthetic design that can modulate ankle stiffness when transitioning from one locomotor task to another could be valuable, but its importance likely involves factors beyond optimizing metabolic cost.
Details
- Title: Subtitle
- The effects of ankle stiffness on mechanics and energetics of walking with added loads: a prosthetic emulator study
- Creators
- Erica A. Hedrick - University of Nebraska at OmahaPhilippe Malcolm - University of Nebraska at OmahaJason M. Wilken - University of IowaKota Z. Takahashi - University of Nebraska at Omaha
- Resource Type
- Journal article
- Publication Details
- Journal of neuroengineering and rehabilitation, Vol.16(1), pp.148-148
- DOI
- 10.1186/s12984-019-0621-x
- PMID
- 31752942
- PMCID
- PMC6873504
- NLM abbreviation
- J Neuroeng Rehabil
- ISSN
- 1743-0003
- eISSN
- 1743-0003
- Publisher
- Springer Nature
- Number of pages
- 15
- Grant note
- NASA Nebraska Space Grant Fellowship P20GM109090 / Center for Research in Human Movement Variability of University of Nebraska at Omaha, NIH University of Nebraska at Omaha
- Language
- English
- Date published
- 11/21/2019
- Academic Unit
- Physical Therapy and Rehabilitation Science
- Record Identifier
- 9984295048502771
Metrics
15 Record Views