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Comparison between in vivo and theoretical bite performance: Using multi-body modelling to predict muscle and bite forces in a reptile skull

Jones, M.E.H.; Lappin, A.K.; O�Higgins, P.; Evans, S.E.; Fagan, M.J.; Curtis, N.; Jones, M. E. H.; Lappin, A. K.; O'Higgins, P.; Evans, S. E.; Fagan, M. J.


M.E.H. Jones

A.K. Lappin

P. O�Higgins

S.E. Evans

M.J. Fagan

N. Curtis

M. E. H. Jones

A. K. Lappin

P. O'Higgins

S. E. Evans

M. J. Fagan


In biomechanical investigations, geometrically accurate computer models of anatomical structures can be created readily using computed-tomography scan images. However, representation of soft tissue structures is more challenging, relying on approximations to predict the muscle loading conditions that are essential in detailed functional analyses. Here, using a sophisticated multi-body computer model of a reptile skull (the rhynchocephalian Sphenodon), we assess the accuracy of muscle force predictions by comparing predicted bite forces against in vivo data. The model predicts a bite force almost three times lower than that measured experimentally. Peak muscle force estimates are highly sensitive to fibre length, muscle stress, and pennation where the angle is large, and variation in these parameters can generate substantial differences in predicted bite forces. A review of theoretical bite predictions amongst lizards reveals that bite forces are consistently underestimated, possibly because of high levels of muscle pennation in these animals. To generate realistic bites during theoretical analyses in Sphenodon, lizards, and related groups we suggest that standard muscle force calculations should be multiplied by a factor of up to three. We show that bite forces increase and joint forces decrease as the bite point shifts posteriorly within the jaw, with the most posterior bite location generating a bite force almost double that of the most anterior bite. Unilateral and bilateral bites produced similar total bite forces; however, the pressure exerted by the teeth is double during unilateral biting as the tooth contact area is reduced by half. © 2010.


Curtis, N., Jones, M. E. H., Lappin, A. K., O'Higgins, P., Evans, S. E., & Fagan, M. J. (2010). Comparison between in vivo and theoretical bite performance: Using multi-body modelling to predict muscle and bite forces in a reptile skull. Journal of biomechanics, 43(14), 2804-2809.

Journal Article Type Article
Acceptance Date May 29, 2010
Online Publication Date Jul 31, 2010
Publication Date Oct 19, 2010
Print ISSN 0021-9290
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 43
Issue 14
Pages 2804-2809
Keywords Bite force; Multi-body analysis; Muscle force; Skull; Sphenodon; Muscle stress
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