A Method for Numerical Simulation of Single Limb Ground Contact Events: Application to Heel-Toe...

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A Method for Numerical Simulation of Single LimbGround Contact Events: Application to Heel-ToeRunningR. R. NEPTUNE a , I. C. WRIGHT a & A. J. VAN DEN BOGERT ba Human Performance Laboratory, University of Calgary , Calgary, AB, T2N 1N4b Department of Biomedical Engineering , The Cleveland Clinic Foundation , Cleveland, OH,44195Published online: 28 Mar 2007.

To cite this article: R. R. NEPTUNE , I. C. WRIGHT & A. J. VAN DEN BOGERT (2000) A Method for Numerical Simulation ofSingle Limb Ground Contact Events: Application to Heel-Toe Running, Computer Methods in Biomechanics and BiomedicalEngineering, 3:4, 321-334, DOI: 10.1080/10255840008915275

To link to this article: http://dx.doi.org/10.1080/10255840008915275

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loads are influenced by factors such as the taskbeing performed, anatomy, muscle coordination andequipment selection (e.g. footwear). For a givenmovement or task, muscle coordination and equipment selection are factors that can be altered withinlimitations to help reduce musculoskeletal loading.But it is not clear a priori how these factors willaffect the loading because of the highly nonlineardynamics and complex lower extremity movementkinematics. Changes in the movement caused byaltered muscle forces and equipment selection resultin changes in the muscle kinematics, and therefore, changes in the muscle forces. These circular dynamic interactions within the musculoskeletal system make these responses difficult to predictand interpret, and the effects are often counterintuitive. Understanding the dynamic interactions andthe changes in joint loading associated with interventions is required for injury prevention and thedesign of safe and effective rehabilitation protocols. However, experimental studies have been limited in their ability to quantify joint loading duringnormal movement tasks due to technical and ethicallimitations.

The effect of muscle properties, coordinationchanges and equipment selection on musculoskeletal loads can be examined systematically usingtheoretical musculoskeletal models. Such modelsrequire a sufficiently realistic mathematical representation of the skeletal dynamics, muscle forcesand their dependence on length, velocity and activation, and contact forces with the environment. Twodimensional (2D) sagittal plane models of humanlocomotion have been developed to simulate thevarious portions of gait (e.g. Davy and Audu, 1987;Pandy and Berme, 1988; Gerritsen et al., 1998;Piazza and Delp, 1996) and the impact phase ofrunning (Gerritsen et al., 1995; Cole et al., 1996).But the three-dimensional (3D) kinematic couplingwithin the lower extremity limits the ability of these2D models to quantify joint loading accurately. Stacoff et al., (1988) suggested that foot pronation isan important shock absorption mechanism duringrunning and Nigg et al., (1993) identified a kinematic link between pronation and internal rotation

of the tibia which may generate undesired loads atthe knee. Therefore, a 3D musculoskeletal model isneeded to investigate locomotion and the associatedjoint loading.

Three-dimensional models of human locomotionhave been developed (Gilchrist and Winter, 1997;Ju and Mansour, 1988; Pandy and Berme, 1989;Yamaguchi and Zajac, 1990), but these modelswere often simplified to reduce the computationaldemands. These models either restricted certain jointmovements to the sagittal plane, did not includeindividual muscle actuators governed by activationdynamics and the force-length and velocity relationships, or they did not simulate the contact betweenthe foot and ground at impact. Modeling the 3Dmovement at all joints is necessary to examine jointloading during non-sagittal plane movements (e.g.cutting and turning) and both the individual muscleforces and the ground contact force play an important role in determining the internal joint loads during dynamic movements. As computational speedsincrease, the feasibility of producing full 3D simulations of human locomotion incorporating thesenecessary features is becoming more realistic.

Therefore, the objective of this project was todevelop a 3D musculoskeletal model of the lowerextremity with individual muscle actuators andground contact elements and to generate a forwarddynamic simulation of subject-specific movementsthat can be applied to studies of lower extremityloading during dynamic activities. Then, multiplesubject-specific simulations may be performed andthe results analyzed statistically, similar to theanalysis of a group of human subjects. As anapplication of the model, heel-toe running wasexamined because it is associated with a highinjury rate for both young (32%) and older (41%)age populations (Matheson et al., 1989). This highinjury rate yields an overall yearly incidence rateof running injuries between 37% and 56% (vanMechelen, 1992). Running is a highly dynamicmovement with both a rapid impulsive loading phaseat impact and a phase with large actively generatedmuscle forces that might contribute to the injuryrate. Thus, a theoretical model of running may

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A Method for Numerical Simulation of Single Limb Ground Contact Events: Application to Heel-Toe...

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