Finite element model for the simulation of skeletal muscle fatigue

In the present paper a new approach for the modelling of fatigue effects in skeletal muscle is proposed. This concept is micromechanically motivated. It incorporates the intramuscular connective tissue (passive part of the material) which surrounds the contractile muscle fibres (active part of the material). By sustaining a certain force level, these fibres show fatigue effects, expressed by a decrease of the retentive force. To incorporate such effects in a finite element framework we use a fatigue model that allows us to describe the dynamical processes between active, fatigued and recovered fibres. The chosen modelling strategy facilitates the efficient transport of the known information about physiological processes in the fibre to the three-dimensional macroscopic level where e.g. the dependence of muscle contraction on fatigue effects is studied. Besides the theoretical derivation of the modelling approach, simulations at fibre level as well as at muscle level (for idealised and non-idealised muscle geometries) are investigated. The paper closes with a qualitative comparison of the model with experimental data.