<p>This study presents a novel muscle control algorithm for finite element (FE) human body models to simulate neck muscles’ active contraction, thereby enhancing the biomechanical realism under whiplash loading. The algorithm (based on a Hill-type muscle model) autonomously maintained the head–neck posture under 1 G load conditions and was implemented into a calibrated FE model of the head–neck complex that reflected physiological cervical kinematics. The model maintained stable posture control across various initial positions and responded robustly to dynamic disturbances. Moreover, it successfully reproduced the characteristic S-shaped cervical deformation of the whiplash motion in a rear-end collision simulation. Notably, significant tensile strains were observed in facet joint capsules, particularly at the C2–C3 and C4–C5 levels—regions potentially associated with soft tissue damage. Although the algorithm relies on certain assumptions regarding neutral posture and antagonist muscle activation, it remains computationally efficient and applicable to models with varying anthropometry. In conclusion, this algorithm markedly improves FE models’ predictive accuracy for whiplash injury analysis and offers a promising tool for developing more effective and personalized automotive safety systems. Future work will expand its applicability to vulnerable populations and evaluate the role of head restraints in injury mitigation.</p> Graphical abstract <p>S-shape of the head–neck complex model formed during whiplash-like motion</p> <p></p>