Analysis of head-to-head impact in football with human finite element model considering pre-impact cervical muscle activation

American football is characterized by its intense collision, which can induce serious injuries such as concussions and head trauma. Therefore, the evaluation of the safety of players is mandatory. In this study, we have developed a new finite element analysis model to evaluate the head kinematic response in American football. The novelty of our model is the incorporation of the effect of cervical muscle strength and pre-impact cervical muscle activation on head kinematics response. This model is based on the head-neck model extracted from the Total HUman Model for Safety (THUMS). The finite element analysis of the hit movement, which is frequently seen during the American football practices, is performed with four different cervical muscle conditions; (i) early pre-impact activation, (ii) late pre-impact activation, (iii) weak muscle strength, and (iv) No pre-impact activation. We also performed an experiment to measure head kinematics response and torso rotation in the hit movement of American football players by mouthguard sensors and video motion capture system for model validation. The four conditions parameter study shows that the time history of head angular velocity with pre-impact muscle activation is better agreement with our experimental results. Therefore, it is important to model the pre-impact cervical muscle activation in the finite element analysis for evaluating the head kinematic response accurately. We also found that higher cervical muscle strength and earlier cervical muscle activation decrease the head angular acceleration at 20-35 ms after the head collision. This suggests that, in the case of low-intensity head collision, strengthening cervical muscles and activating them before the head impact by anticipating the collision can reduce head angular acceleration.