Problem
Industry partner: fleXstructures GmbH
fleXstructures GmbH was founded in 2012 as a spin-off company of Fraunhofer ITWM. Since then, the company has developed into a global technology leader in the area of digital layout and validation of flexible components such as cables and hoses. More than 130 customers worldwide use IPS software in their product development and product realization processes. As an innovative and very research-oriented company, fleXstructures has established sustainably strong partnerships with the Fraunhofer ITWM in Kaiserslautern and the Fraunhofer Chalmers Centre for Industrial Mathematics in Gothenburg, both members of ECMI and active in the ECMI special interest group "Mathematics for the Digital Factory".
Modeling and simulation of muscle fatigue effects
Foreword
The ergonomic layout of workplaces in production and manufacturing is an important requirement for maintaining the productivity, health and well-being of human workers. Digital human models (DHM) like IMMA [1] are very useful tools that incorporate a variety of mathematical modeling techniques to support this objective by simulating tasks performed by human workers. Such simulations help to assess the physical loads acting on the human body.
In this industrial application context, mathematical models that account for fatigue effects under repetitive physical action are not yet considered in state-of-the-art DHM, although such effects are important for an ergonomic evaluation of working tasks.
Therefore, fleXstructures GmbH is interested in the exploration of different approaches to muscle fatigue modeling for applications in DHM.
Task
A model should be devised that can be utilized to simulate fatigue effects in human muscles subject to repetitive contraction. The model should be implemented for the concrete example of single-arm biceps curls.
To complement this, an approach should be developed to test and validate the model using experimental data, possibly from own experiments with a group of people.
An appropriate protocol of the experimental procedure should be developed and described precisely in the report. Parts of the procedure are e.g.: The choice of weights, the number of repetitions per series, the speed of execution, the prescribed posture of the subject when performing the experiment, the composition of the test group and similar information.
The presentation of the results should address a qualitative and quantitative discussion of model features and should contain a concept to adapt the model parameters to experimental data. Also, the model capabilities to represent characteristics that account for gender, age, varying physical conditions should be considered. Other questions of interest are: How can the model be used for diagnostic purposes? Can training effects be observed by interpreting simulation results?
Background
Digital human models are biomechanical multibody systems actuated by simplified mathematical models of muscles [2].
In biomechanics, there are variety of modeling approaches for human muscular structures, ranging from simple data-based models of look-up table type, over Hill-type muscle models of intermediate complexity representing muscles as ensembles of active string-like structures, up to very complex 3D finite element models incorporating the simulation of different metabolic processes.
Correspondingly one finds approaches of varying complexity to model fatigue effects in muscles. A generic approach of rate equation type proposed in [3] can be coupled with all types of muscle models, and could be utilized as a basis to solve the modeling task.
References
[1] IPS IMMA – Intelligently Moving Manikin
[2] The Fraunhofer research project EMMA-CC
[3] Liu J.Z., Brown R.W., Yue G.H., (2002), "A Dynamical Model of Muscle Activation, Fatigue, and Recovery", Biophysical Journal 82(5):2344-2359, doi: 10.1016/S0006-3495(02)75580-X
