The human foot and heel-sole-toe walking strategy
09 May 2012
Research, funded by the Wellcome Trust and the Biotechnology and Biological Sciences Research Council, highlights that prosthetic lower limbs and robots' legs could be made more efficient, by making them less human like.
There is one mechanically efficient way of walking: vault over a stiff leg, shove off, then crash into the next vault. Humans achieve this, even when walking in high heels or on tiptoes. Ostriches do too, even though they completely lack a functional ‘heel’. The normal human foot and heel-sole-toe stance, though, has the advantage that it allows those muscles powering the shove (calf) and absorbing the crash (shin) to be largely unloaded during the vault. This is a benefit as muscles use energy when opposing force, but motors don’t – so prosthetics and robotics should not copy human feet.
Walking in high heels, and by ostriches, produces forces remarkably similar to normal human walking, maintaining the economical ‘crash-vault-shove’ strategy predicted from point mass models.
Image by Jim Usherwood, copyright Structure & Motion Lab., RVC, with thanks to Monica Daley and Yvonne Blum.
Usherwood, J.R., Channon, A.J., Myatt, J.P., Rankin, J.W. and Hubel, T.Y. (2012).
The human foot and heel-sole-toe walking strategy: a mechanism enabling an inverted pendular gait with low isometric muscle force? J. R. Soc. Interface. doi: 10.1098.fsif.2012.0179
See also Wellcome Trust press release.
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