Modelling three–dimensional human strength capacity: logistic vs. polynomial surface equations

John M Looft; Laura A Frey-Law

doi:10.1504/IJHFMS.2015.068122

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Modelling three–dimensional human strength capacity: logistic vs. polynomial surface equations

Journal article

Peer reviewed

Modelling three–dimensional human strength capacity: logistic vs. polynomial surface equations

John M Looft and Laura A Frey-Law

International journal of human factors modelling and simulation, Vol.5(1), pp.5-18

01/01/2015

DOI: 10.1504/IJHFMS.2015.068122

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Abstract

One approach to modelling muscle strength is to represent peak torque as three–dimensional (3D) torque–angle–velocity surfaces at the joint level. These nonlinear relationships have been modelled using polynomial equations. However, we hypothesised logistic equations would better represent 3D peak strength based on known 'S–shaped' relationships between torque and velocity. To compare the two approaches, we modelled eight 3D strength surfaces based on previously published data, elbow and knee strength, using polynomial and logistic equations. Both models fit the strength data well, with median R² values of 0.983 and 0.971 for polynomial and logistic equations, respectively. However, when extrapolating the models to a full normal range of motion (0° to 140°) 100% of the polynomial surfaces, but only 25% of the logistic surfaces, displayed non–physiologic strength estimates (i.e., crossed zero). Accordingly, logistic equations may provide equal or better representations of 3D joint strength surfaces for digital human modelling.

Ergonomics

3D strength surfaces

digital human modelling

torque–velocity–angle

muscle force

polynomial equations

normative strength

muscle strength

logistic equations

mathematical modelling

three–dimensional strength surfaces

torque–velocity relationship

peak torque

elbow strength

polynomial surfaces

torque–angle relationship

knee strength

logistic surfaces

Details

Title: Subtitle: Modelling three–dimensional human strength capacity: logistic vs. polynomial surface equations
Creators: John M Looft - 1 Virtual Soldier Research Group, Center for Computer–Aided Design, College of Engineering, University of Iowa, Iowa City, IA 52242, USA
Laura A Frey-Law - 2 Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, 1–252 Medical Education Bldg., Iowa City, IA 52242, USA
Resource Type: Journal article
Publication Details: International journal of human factors modelling and simulation, Vol.5(1), pp.5-18
Publisher: Inderscience Publishers
DOI: 10.1504/IJHFMS.2015.068122
ISSN: 1742-5549
eISSN: 1742-5557
Language: English
Date published: 01/01/2015
Academic Unit: Nursing; Physical Therapy and Rehabilitation Science
Record Identifier: 9984047872202771

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