Facial muscle tissues play a fundamental role in mastication, facial expression, and speech, yet their mechanical behaviour remains poorly characterised, particularly with respect to nonlinear and strain-rate-dependent responses. This lack of experimental data limits the accuracy of biomechanical models used in surgical simulation, soft-tissue reconstruction, and computational analysis of the human face. Although strain-rate effects and viscoelasticity have been widely reported in skeletal muscle tissues, corresponding data for facial muscle tissues remain scarce [1,2]. The present study investigates the mechanical behaviour of human facial muscle tissues under controlled ex vivo loading, with emphasis on strain-rate sensitivity and its implications for constitutive modelling. Facial muscle tissues were harvested from multiple human cadavers of varying sex and preservation condition, including both fresh and formalin-fixed specimens. A broad range of facial muscles was examined to capture anatomical and functional variability, including, for example, the masseter, buccinator, and zygomatic muscles. After dissection, tissues were cleaned of surrounding fat layers and prepared as standardised specimens for uniaxial tensile testing. An initial failure assessment was performed to determine the approximate rupture strain of each specimen, which varied substantially across tissues. Based on these measurements, a five-cycle viscoelastic loading protocol with progressively increasing stretch levels was defined. Experiments were conducted at two strain rates, 1% s⁻¹ and 10% s⁻¹, while force–displacement data were continuously recorded. The results demonstrate a clear strain-rate-dependent response across all examined tissues, with higher strain rates consistently producing increased stiffness. Although this trend was observed in all samples, the magnitude of the rate effect varied among tissues, indicating tissue-specific viscoelastic behaviour. These findings highlight the importance of incorporating strain-rate sensitivity and tissue variability in facial muscle modelling and will support the development of advanced constitutive frameworks for facial biomechanics. REFERENCES [1] [1] Lu, Y.T., Zhu, H.X., Richmond, S., Middleton, J., A visco-hyperelastic model for skeletal muscle tissue under high strain rates, Journal of Biomechanics, 43(13), 2629–2632, 2010. [2] Van Loocke, M., Lyons, G.M., Hutchinson, J.R., Viscoelastic properties of passive skeletal muscle