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Author Notes:

Correspondence: karenliu@cc.gatech.edu

Conceptualization: YSS SH LHT CKL. Data curation: YSS SH HH. Formal analysis: YSS SH.

Funding acquisition: LHT CKL. Investigation: YSS SH HH. Methodology: YSS SH LHT CKL.

Project administration: LHT CKL. Resources: YSS SH LHT CKL. Software: YSS SH CKL.

Supervision: LHT CKL. Validation: YSS SH HH LHT CKL. Visualization: YSS.

Writing – original draft: YSS SH HH LHT CKL. Writing – review & editing: YSS LHT CKL.

The authors would like to thank Dr. Young-Hui Chang and Dr. Randy Trumbower for use of their equipment.

Competing Interests: The authors have declared that no competing interests exist.


Research Funding:

This work was supported by the National Science Foundation (NSF), Grant EFRI-1137229.


  • Legs
  • Joints (anatomy)
  • Knee joints
  • Mechanical energy
  • Walking
  • Ankle joints
  • Musculoskeletal system
  • Myalgia

Stair negotiation made easier using novel interactive energy-recycling assistive stairs.


Journal Title:



Volume 12, Number 7


, Pages e0179637-e0179637

Type of Work:

Article | Final Publisher PDF


Here we show that novel, energy-recycling stairs reduce the amount of work required for humans to both ascend and descend stairs. Our low-power, interactive, and modular steps can be placed on existing staircases, storing energy during stair descent and returning that energy to the user during stair ascent. Energy is recycled through event-triggered latching and unlatching of passive springs without the use of powered actuators. When ascending the energy-recycling stairs, naive users generated 17.4 ± 6.9% less positive work with their leading legs compared to conventional stairs, with the knee joint positive work reduced by 37.7 ± 10.5%. Users also generated 21.9 ± 17.8% less negative work with their trailing legs during stair descent, with ankle joint negative work reduced by 26.0 ± 15.9%. Our low-power energy-recycling stairs have the potential to assist people with mobility impairments during stair negotiation on existing staircases.

Copyright information:

© 2017 Song et al.

This is an Open Access work distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).
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