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Running in the real world: adjusting leg stiffness for different surfacesA running animal coordinates the actions of many muscles, tendons, and ligaments in its leg so that the overall leg behaves like a single mechanical spring during ground contact. Experimental observations have revealed that an animal's leg stiffness is independent of both speed and gravity level, suggesting that it is dictated by inherent musculoskeletal properties. However, if leg stiffness was invariant, the biomechanics of running (e.g. peak ground reaction force and ground contact time) would change when an animal encountered different surfaces in the natural world. We found that human runners adjust their leg stiffness to accommodate changes in surface stiffness, allowing them to maintain similar running mechanics on different surfaces. These results provide important insight into mechanics and control of animal locomotion and suggest that incorporating an adjustable leg stiffness in the design of hopping and running robots is important if they are to match the agility and speed of animals on varied terrain.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Ferris, D. P.
(University of California Berkeley 94720-3140, United States)
Louie, M.
Farley, C. T.
Date Acquired
August 22, 2013
Publication Date
June 7, 1998
Publication Information
Publication: Proceedings of the Royal Society of London. Series B. Biological sciences
Volume: 265
Issue: 1400
ISSN: 0962-8452
Subject Category
Life Sciences (General)
Funding Number(s)
Distribution Limits
NASA Discipline Musculoskeletal
Non-NASA Center

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