What is a moment arm? Calculating muscle effectiveness in biomechanical models using generalized coordinates

Michael A. Sherman, Ajay Seth, Scott L. Delp

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review

43 Citations (Scopus)

Abstract

Biomechanics researchers often use multibody models to represent biological systems. However, the mapping from biology to mechanics and back can be problematic. OpenSim is a popular open source tool used for this purpose, mapping between biological specifications and an underlying generalized coordinate multibody system called Simbody. One quantity of interest to biomechanical researchers and clinicians is "muscle moment arm," a measure of the effectiveness of a muscle at contributing to a particular motion over a range of configurations. OpenSim can automatically calculate these quantities for any muscle once a model has been built. For simple cases, this calculation is the same as the conventional moment arm calculation in mechanical engineering. But a muscle may span several joints (e.g., wrist, neck, back) and may follow a convoluted path over various curved surfaces. A biological joint may require several bodies or even a mechanism to accurately represent in the multibody model (e.g., knee, shoulder). In these situations we need a careful definition of muscle moment arm that is analogous to the mechanical engineering concept, yet generalized to be of use to biomedical researchers. Here we present some biomechanical modeling challenges and how they are resolved in OpenSim and Simbody to yield biologically meaningful muscle moment arms.

Original languageEnglish
Title of host publication9th International Conference on Multibody Systems, Nonlinear Dynamics, and Control
PublisherAmerican Society of Mechanical Engineers
ISBN (Print)9780791855973
DOIs
Publication statusPublished - 2013
EventASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, IDETC/CIE 2013 - Portland, OR, United States
Duration: 4 Aug 20137 Aug 2013

Publication series

NameProceedings of the ASME Design Engineering Technical Conference
Volume7 B

Conference

ConferenceASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, IDETC/CIE 2013
CountryUnited States
CityPortland, OR
Period4/08/137/08/13

Bibliographical note

Copyright:
Copyright 2014 Elsevier B.V., All rights reserved.

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