Chapter

The Biomechanics of Movement Control

Walter Herzog

in Motor Control

Published in print December 2010 | ISBN: 9780195395273
Published online January 2011 | e-ISBN: 9780199863518 | DOI: http://dx.doi.org/10.1093/acprof:oso/9780195395273.003.0008
The Biomechanics of Movement Control

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The control of joint movements through muscles represents a mathematically redundant problem: that is, there are more muscles than are strictly required for a given task. However, despite this apparent redundancy, movements are performed with a stereotypical pattern of muscle activation and synergistic force sharing. Through direct measurement of multiple muscle forces in freely moving animals, this chapter demonstrates that force sharing patterns depend crucially on the mechanical properties of the muscles: the force-length and force-velocity relationships. Using optimal control theory, force sharing patterns can now be predicted confidently when the mechanical properties of the muscles and their instantaneous contractile conditions are accurately represented in the cost functions used to determine force sharing patterns. Although the mechanical properties and instantaneous contractile conditions of muscles are easy to determine in animal models of motor control, force-length and force-velocity properties for individual human skeletal muscles are still hard to obtain, and the instantaneous contractile properties of in vivo human muscle fascicles during dynamic activities can still only be obtained for a few select muscles and under highly restrictive laboratory conditions. Therefore, accurate predictions of individual muscle forces during human movements will remain a challenge for the future.

Keywords: joint movements; muscles; muscle activation; muscle forces; force sharing patterns

Chapter.  6552 words.  Illustrated.

Subjects: Neuroscience

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