spacer gif spacer gif spacer gif spacer gif Online submission spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

First published online February 1, 2008
Journal of Experimental Biology 211, 467-481 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.008573
This Article
Right arrow Figures Only
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Related articles in JEB
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Google Scholar
Right arrow Articles by Herr, H.
Right arrow Articles by Popovic, M.
PubMed
Right arrow PubMed Citation
Right arrow Articles by Herr, H.
Right arrow Articles by Popovic, M.

Angular momentum in human walking

Hugh Herr1,2,* and Marko Popovic1

1 The MIT Media Laboratory, 20 Ames Street, Cambridge, MA 02139, USA
2 The Harvard-MIT Division of Health Sciences and Technology, 20 Ames Street, Cambridge, MA 02139, USA

* Author for correspondence (e-mail: hherr{at}media.mit.edu)

Accepted 2 December 2007

Angular momentum is a conserved physical quantity for isolated systems where no external moments act about a body's center of mass (CM). However, in the case of legged locomotion, where the body interacts with the environment (ground reaction forces), there is no a priori reason for this relationship to hold. A key hypothesis in this paper is that angular momentum is highly regulated throughout the walking cycle about all three spatial directions [Formula], and therefore horizontal ground reaction forces and the center of pressure trajectory can be explained predominantly through an analysis that assumes zero net moment about the body's CM. Using a 16-segment human model and gait data for 10 study participants, we found that calculated zero-moment forces closely match experimental values (Formula; Formula). Additionally, the centroidal moment pivot (point where a line parallel to the ground reaction force, passing through the CM, intersects the ground) never leaves the ground support base, highlighting how closely the body regulates angular momentum. Principal component analysis was used to examine segmental contributions to whole-body angular momentum. We found that whole-body angular momentum is small, despite substantial segmental momenta, indicating large segment-to-segment cancellations (~95% medio-lateral, ~70% anterior–posterior and ~80% vertical). Specifically, we show that adjacent leg-segment momenta are balanced in the medio-lateral direction (left foot momentum cancels right foot momentum, etc.). Further, pelvis and abdomen momenta are balanced by leg, chest and head momenta in the anterior–posterior direction, and leg momentum is balanced by upper-body momentum in the vertical direction. Finally, we discuss the determinants of gait in the context of these segment-to-segment cancellations of angular momentum.

Key words: biomechanics, biped, locomotion, angular momentum, human


Related articles in JEB:

THE ROLE OF ANGULAR MOMENTUM IN WALKING
Kathryn Phillips
JEB 2008 211: 0. [Full Text]  



This article has been cited by other articles:


Home page
 J. Exp. Biol.Home page
K. Phillips
THE ROLE OF ANGULAR MOMENTUM IN WALKING
J. Exp. Biol., February 15, 2008; 211(4): i - i.
[Full Text] [PDF]


© The Company of Biologists Ltd 2008