In this article, frog gastrocnemius muscles are studied, and a multi-model identification presented. A transfer function is defined with few parameters to simulate striated muscle (Gastroctnemius) behaviour, for inclusion in a future real-time salamander computer model. A two-model structure permits description of both contraction and relaxation properties. Here, two physiological influences, fatigue and fibre types, are taken into account. A multi-model structure for each fibre type (fast (IIB), intermediate (IIA) and slow (I) fibres) is also used for inclusion in a future agonist-antagonist structure computer model.