Effect of backrest on head-cervical spine biodynamics in seated human: A finite element study

This paper studied the effect of backrest support (no backrest support (NBS), ergonomic backrest support (EBS) and non-ergonomic backrest support (N-EBS)) on the biodynamics of the head-cervical spine. Using a previously developed finite element model of a 3D body-seat system, modal and random response analyses were done under vertical white noise excitation (between 0 and 20 Hz at 1 m/s 2 r.m.s). The results showed that modal frequencies at 5.45 and 7.33 Hz (EBS), 4.23 and 6.05 Hz (N-EBS) and 4.14 and 4.84 Hz (NBS) significantly influenced the vertical vibration of the seated human body. Compared to the NBS model, the peak frequencies of the head and neck response increased by 33% and 55% in the N-EBS and EBS models, respectively, and peak amplitudes at the front of the head increased by 25% (N-EBS) and 45% (EBS), while those at the back of the head-cervical spine decreased consistently. The response of the different positions of the head varied most significantly in the EBS model, with peak frequency and difference of 53% and 30%, respectively. All back supports showed the highest stress at C5–C6 of the cervical disc, with a peak between 1 and 2 Hz. Notably, EBS reduced the vertical cervical response but increased the anterior-posterior response. This paper provided a new idea for studying the biodynamics of the head-cervical spine as well as theoretical and applied guide for the safe and comfortable design of seats and the reduction of cervical spine injuries.