Abstract: Felids, during intense activities such as jumping and sprinting, adjust their posture by twisting and stretching their body to disperse limb impact and minimize injury. This self-stabilization mechanism has garnered significant attention for inspiring biometric robot design. This study investigates the flexibility and cushioning characteristics of a cat’s spine, focusing on its biomechanical properties. A high-fidelity 3D model was used to test the range of motion (ROM) under six conditions, simulate dorsiflexion to analyze stress distribution. The torsional and compressive stiffness were tested by using five cat spinal specimens. the flexibility principles of the flexible cat’s spine were explained via morphological insights. Results indicate that the cat spine has the least rotational stiffness in axial rotation, followed by extension and lateral bending, with a compressive stiffness of 53.62?±?4.68 N/mm. Stress during dorsiflexion is evenly distributed across vertebrae. The vertebrae heights account for 90.34% of total spinal length with a mean height-to-width ratio of 1.04. Cats’ spines, with more articulations and elongated vertebrae, allow for significant twisting and bending, aiding in rapid body posture adjustments and impact mitigation. These biomechanical traits could inspire the design of robots for confined rescue operations.

Key words: Cat spine · Biomechanical characterization · Finite element analysis · Morphological measurement · Flexibility testing