Modelling of the hamstring muscle group by use of fractional derivatives

This paper deals with a viscoelastic model of the hamstring muscle group. The model includes fractional derivatives of stretching force and elongation, as well as restrictions on the coefficients that follow from the Clausius-Duhem inequality. On the basis of a ramp-and-hold type of experiment, four rheological parameters have been calculated by numerical treatment ab initio. Riemann-Liouville fractional derivatives were approximated numerically using the Grunwald-Letnikov definition. Obtained results were verified by use of the Laplace transform method. The stretching force in time domain involves Mittag-Leffler-type function. (C) 2009 Elsevier Ltd. All rights reserved.