ABSTRACT
Objective To investigate the effect from helmet mass and deviation of mass center on neck muscle activity in military pilots. Methods Based on AnyBody software platform, a musculoskeletal model of head neck complex was established including C0, C1-C7, T1 and 136 muscles. Concentrated loads were applied to simulate the role of helmet. Strength from seven main muscle groups under different helmet mass, mass center and +Gz acceleration loads were simulated and calculated.Results When mass center of the helmet and the head coincided with each other, the muscle groups (such as semispinalis, levator scapulae, splenius capitis and cervicis) which took charge of extension were activated. Muscle strength increased with helmet mass linearly and +Gz acceleration loads would make this increase multiplied. Flexion muscle began to work when mass center of the helmet moved backward, so did the lateral bending muscles when mass center of helmet moved in the right-and-left direction. Conclusions Helmet mass and its center have an obvious influence on neck muscle activity in military pilots. The musculoskeletal model established in this paper can be used to calculate the change in muscle strength under different situations and conduct a quantitative analysis for helmet design and validation.
ABSTRACT
Objective To analyze the dynamic response and strain of the major muscles in head-neck complex of pilot with or without wearing the helmet during carrier aircraft arrested deck landing. Methods Ten-rigid body dynamic model of human head-neck complex was created including head, seven cervical vertebrae and two thoracic vertebrae; mechanical properties of the ligaments, intervertebral discs and other surrounding soft tissues were described by lumped parameter method; mechanical properties of the 15 pairs of muscles in this human head-neck complex were represented by non-linear stress-strain relationship. The model was validated by using experimental data of dynamic responses from the human head-neck complex in a set of different types of automobile crashes. Results The overload curve and strain of this 15 pairs of muscles in head-neck complex of the pilot during arrested deck landing were obtained. The results showed that the extension of splenius cervicis was the largest. The strain of splenius cervicis could reach 50% when the pilot wore the helmet, and it could reach as high as 56% if the helmet’s weight was 2.7 kg. Conclusions Wearing helmet would extend the stretch of neck muscles, and the simulation result could be used for further evaluation on head/neck injury of the pilot.
ABSTRACT
Objective To analyze the neck muscle activity during head flexion and explore the cause of muscle fatigue in human head and neck. Methods A musculoskeletal model of head neck complex was established based on AnyBody software platform, and the muscle strengths during head flexion were simulated according to the input data measured by Vicon motion capture system, which were validated with the literature data. Results The neck muscles played a major role during head flexion. The force assignment mode among muscles was different during 45% and 75% flexion process. The integral of muscle strengths on flexion angle WM could reflect the muscle fatigue to some extent. Since the largest WM was found in the semispinalis cervicis and multifidus muscles during head flexion, it may indicate that those muscles have the easy tendency to be fatigue. Conclusions The musculoskeletal model established in this paper can provide a technical support for the exploration of neck fatigue mechanism.