A model-based parametric study of soft tissue vibrations during running (original) (raw)
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Journal of Biomechanics, 2010
A previously developed mass-spring-damper model of the human body is improved in this paper, taking muscle activity into account. In the improved model, a nonlinear controller mimics the functionality of the Central Nervous System (CNS) in tuning the mechanical properties of the soft-tissue package. Two physiological hypotheses are used to determine the control strategies that are used by the controller. The first hypothesis (constant-force hypothesis) postulates that the CNS uses muscle tuning to keep the ground reaction force (GRF) constant regardless of shoe hardness, wherever possible. It is shown that the constant-force hypothesis can explain the existing contradiction about the effects of shoe hardness on the GRF during running. This contradiction is emerged from the different trends observed in the experiments on actual runners, and experiments in which the leg was fixed and exposed to impact. While the GRF is found to be dependent on shoe hardness in the former set of experiments, no such dependency was observed in the latter. According to the second hypothesis, the CNS keeps the level of the vibrations of the human body constant using muscle tuning. The results of the study show that this second control strategy improves the model such that it can correctly simulate the effects of shoe hardness on the vibrations of the human body during running.
The effects of footwear on impact force during running: a model-based study
A lumped-parameter model of the human body during running was previously developed. The model was used to study the effects of footwear on the impact force during running. However, the parameters of the model were considered constant regardless of the shoe type. Experimental studies have shown that the stiffness and damping of the human body are adjusted in accordance with the stiffness and damping of the shoe-ground system. In this paper, we study how the parameters of the model are adjusted, when the shoe parameters change. The original model is improved by adding a controller which resembles the function of the CNS. The effects of footwear on the impact force are studied by using the improved model. Three different bound limits are used for the model parameters to study the effects of the upper and lower parameter limits on the results. It has been shown that the model can explain the contradictory observations about the effects of footwear on the impact force.
The natural frequency of the foot-surface cushion during the stance phase of running
Journal of Biomechanics, 2011
Researchers have reported on the stiffness of running in holistic terms, i.e. for the structures that are undergoing deformation as a whole rather than in terms of specific locations. This study aimed to estimate both the natural frequency and the viscous damping coefficient of the human foot-surface cushion, during the period between the heel strike and the mid-stance phase of running, using a purposely developed one degree-of-freedom inverted pendulum state space model of the leg. The model, which was validated via a comparison of measured and estimated ground reaction forces, incorporated a novel use of linearized and extended Kalman filter estimators. Investigation of the effect of variation of the natural frequency and/or the damping of the cushioning mechanism during running, using the said model, revealed the natural frequency of running on said foot-surface cushion, during the stance phase, to lie between 5 and 11 Hz. The ''extended Kalman filter (EKF)'' approach, that was used here for the first time to directly apply measured ground forces, may be widely applicable to the identification process of combined estimation of both unknown physiological state and mechanical characteristics of the environment in an inverse dynamic model.
A model-based parametric study of impact force during running
Journal of Biomechanics, 2007
This paper deals with the impact force during foot-ground impact activities such as the running. A previously developed model is used for this study. The model is a lumped-parameter one consisting of four masses connected to each other via linear springs and viscous dampers. A shoe-specific nonlinear function is used for representation of the ground reaction force. The authors have previously showed that the previous version of the model as well as its simulation is incorrect. This paper slightly modifies the previous model so as it is able to produce results in agreement with the experiments. Then, the modified model is simulated for two typical shoe types. A parametric study is also conducted. The parametric study concerns with the effects of masses, mass ratios, stiffness constants, and damping coefficients on the dynamics of the impact. It is shown that the impact forces increase as the rigid and wobbling masses increase. However, the increase in the impact forces is not the same for all the masses. It is found that the impact force increases as the touchdown velocities increase. Simulations imply that the variations of the damping coefficients result in larger variations of the impact force compared to the stiffness. The effect of the variation of gravity on the simulated impact force is also explored. It is concluded that both the first and the second peaks of the impact force are increased with gravity. An in-depth discussion is included to compare results of the current paper with results of other investigators. r
Greene Coleman 2015 Elastic Spring Constants for Running Shoes: A Mathematical Model
Background: Running shoe compliance and track surface stiffness can reduce peak vertical foot forces. It is therefore of interest to measure directly the force-deflection curve for running shoes in the heel and forefoot areas. This study compares these measurements with similar work on track and field surfaces, and derives a mathematical stress-strain model useful over the entire force range.
Journal of Biomechanics, 2010
Several spring–damper–mass models of the human body have been developed in order to reproduce the measured ground vertical reaction forces during human running (McMahon and Cheng, 1990; Ferris et al., 1999; Liu and Nigg, 2000). In particular, Liu and Nigg introduced at the lower level of their model, i.e. at the interface between the human body and the ground, a nonlinear element representing simultaneously the shoe midsoles and the ground flexibility. The ground reaction force is modelled as the force supported by this nonlinear element, whose parameters are identified from several sets of experimental data. This approach proved to be robust and quite accurate. However, it does not explicitly take into account the shoe and the ground properties. It turns out to be impossible to study the influence of shoe materials on the impact force, for instance for footwear design purposes. In this paper, a modification of the Liu and Nigg's model is suggested, where the original nonlinear element is replaced with a bi-layered spring–damper–mass model: the first layer represents the shoe midsole and the second layer is associated with the ground.Ground is modelled as an infinite elastic half-space. We have assumed a viscoelastic behaviour of the shoe material, so the damping of shoe material is taken into account. A methodology for the shoe-soles characterization is proposed and used together with the proposed model. A parametric study is then conducted and the influence of the shoe properties on the impact force is quantified. Moreover, it is shown that impact forces are strongly affected by the ground stiffness, which should therefore be considered as an essential parameter in the footwear design.
Parameter identification for vertical ground reaction forces on feet while running
Sports Engineering, 2015
The human foot is subjected to ground reaction forces during running. These forces have been studied for decades to reduce the related injuries and increase comfort. A four-degree-of-freedom system has been used in the literature to simulate the human body motion during the touchdown. However, there are still inconsistencies between the simulation results and experimental measurements. In this study, an optimization technique is proposed to obtain the required parameters to estimate the vertical ground reaction force using the measurements from actual runners. The touchdown velocities of the rigid and wobbling body masses were also treated as optimization variables. It was shown that the proposed parameters can be adjusted to represent a particular shoe type. Specifically, vertical ground reaction force parameters and touchdown velocities were obtained for shoes with various insole properties and cushioning technologies. The results of this study suggest that the human locomotion system reacts to the shoe properties by regulating the velocities of the body wobbling and rigid masses. The magnitude and the load rate obtained using the proposed parameters are consistent with the experimental data. It is shown that the viscoelastic properties of the shoe will significantly affect the load rate but not the load magnitude.
Modelling of Muscle Force Distributions During Barefoot and Shod Running
Journal of human kinetics, 2015
Research interest in barefoot running has expanded considerably in recent years, based around the notion that running without shoes is associated with a reduced incidence of chronic injuries. The aim of the current investigation was to examine the differences in the forces produced by different skeletal muscles during barefoot and shod running. Fifteen male participants ran at 4.0 m·s-1 (± 5%). Kinematics were measured using an eight camera motion analysis system alongside ground reaction force parameters. Differences in sagittal plane kinematics and muscle forces between footwear conditions were examined using repeated measures or Freidman's ANOVA. The kinematic analysis showed that the shod condition was associated with significantly more hip flexion, whilst barefoot running was linked with significantly more flexion at the knee and plantarflexion at the ankle. The examination of muscle kinetics indicated that peak forces from Rectus femoris, Vastus medialis, Vastus lateralis,...
Use of Ground Reaction Force Parameters in Predicting Peak Tibial Accelerations in Running
Journal of Applied Biomechanics, 1993
Ground reaction force data and tibial accelerations from a skin-mounted transducer were collected during rearfoot running at 3.3 m/s across a force platform. Five repetitive trials from 27 subjects in each of 19 different footwear conditions were evaluated. Ground reaction force as well as tibial acceleration parameters were found to be useful for the evaluation of the cushioning properties of different athletic footwear. The good prediction of tibial accelerations by the maximum vertical force rate toward the initial force peak (r2 = .95) suggests that the use of a force platform is sufficient for the estimation of shock-absorbing properties of sport shoes. If an even higher prediction accuracy is required a regression equation with two variables (maximum force rate, median power frequency) may be used (r2 = .97). To evaluate the influence of footwear on the shock traveling through the body, a good prediction of peak tibial accelerations can be achieved from force platform measurem...
Modeling of heel strike transients during running
Human Movement Science, 1994
The goal of this study is to develop a mathematical model that can describe the dissipation and attenuation of the shock wave initiated during the impact of the foot striking the ground. A three-degree-of-freedom spring-damper--mass system was conceived as an equivalent model of the lower extremity. The mathematical model that was developed was used to investigate the shock absorption phenomena of the human body. The model and solution procedure were verified by a drop test. The instant of the impact of landing was assumed to be equivalent to foot strike transients.