The envelope of motion of the cervical spine and its influence on the maximum torque generating capability of the neck muscles

Evaluating the impact of weight and center of mass on comfort in head-mounted displays

This study investigates the impact of the weight and centre of mass (COM) position of Head-Mounted Displays (HMDs) on the subjective evaluation of users during prolonged wearing tasks. This study involved 88 participants completing 1860 sets of experiments under three conditions: sitting still, turning the head, and moving, providing subjective evaluations of wearing HMDs. A static torque testing device was used to simulate neck torque under flexion states. Using Aligned Rank Transform (ART) data, A Multifactor Analysis of Variance (MANOVA) was conducted to analyse the relationship between subjective comfort and the weight and centre of mass (COM) of HMDs. Using cluster analysis to classify head length and identify the relationship between head length and comfort. A Support Vector Regression (SVR) model was ultimately established, providing detailed weight range references for the engineering design of HMDs.

Evaluation of Apparatus and Protocols to Measure Human Passive Neck Stiffness and Range of Motion

Understanding of human neck stiffness and range of motion (ROM) with minimal neck muscle activation ("passive") is important for clinical and bioengineering applications. The aim of this study was to develop, implement, and evaluate the reliability of methods for assessing passive-lying stiffness and ROM, in six head-neck rotation directions. Six participants completed two assessment sessions. To perform passive-lying tests, the participant's head and torso were strapped to a bending (flexion, extension, lateral bending) or a rotation (axial rotation) apparatus, and clinical bed, respectively. The head and neck were manually rotated by the researcher to the participant's maximum ROM, to assess passive-lying stiffness. Participant-initiated ("active") head ROM was also assessed in the apparatus, and seated. Various measures of apparatus functionality were assessed. ROM was similar for all assessment configurations in each motion direction except flexion. In each direction, passive stiffness generally increased throughout neck rotation. Within-session reliability for stiffness (ICC > 0.656) and ROM (ICC > 0.872) was acceptable, but between-session reliability was low for some motion directions, probably due to intrinsic participant factors, participant-apparatus interaction, and the relatively low participant number. Moment-angle corridors from both assessment sessions were similar, suggesting that with greater sample size, these methods may be suitable for estimating population-level corridors.

User experience with ultrawide curved displays: A mixed methods analysis

Due to the trend of replacing dual displays with ultrawide (UW) curved displays, we used a mixed methods analysis to investigate the user experience with UW curved displays. We conducted an experimental laboratory study that quantified user self-selected positions for three displays - 24 in. flat panel, and 34 in. and 40 in. UW curved displays. Participants were first provided with a familiarization protocol, and they then positioned the display. The self-selected UW display viewing distances were within current recommendations; however, viewing distance increased with display size, potentially challenging small work surface depths and may have been in response to feeling "overwhelmed" by larger displays. Head twist range of motion increased with display width. While all displays were within recommendations, participants commented that less head twisting was a factor in choosing the 34 in. over the 40 in. display. Practitioners should assess potential workstation limitations and the potential impact on neck twist angles when installing ultrawide displays.

A novel Cervical Spine Protection device for reducing neck injuries in contact sports: design concepts and preliminary in vivo testing

Head and neck injuries are common in contact sports such as American football. Different mechanisms can produce such injuries, including compressive impact forces on the crown of the helmet with the neck in a flexed chin-down position. The aim of this paper was developing and testing a novel Cervical Spine Protection Device (CSPD) designed to keep the neck within its safe physiological range. The cervical spine range of motion (ROM) of ten participants was measured under four conditions: free; wearing a football gear; wearing the CSPD; and wearing the CSPD underneath the gear. The CSPD was tested in terms of passive and active restraint of head motion, and for its capability to improve endurance time of the neck extensor muscles. Wearing the CSPD resulted in a significant 40-60% reduction in ROM across the three anatomical planes, and in increased endurance of the neck extensor muscles (FREE: 114 ± 57 s; CSPD: 214 ± 95 s; p = 0.004). In quasi-static loading conditions the CSPD was capable of keeping the neck within its physiological range, thus it may be used to decrease the risk of severe injuries due to dangerous chin-down positions.