Exploring the Interaction Between Head-Supported Mass, Posture, and Visual Stress on Neck Muscle Activation

Area of Science:

• Biomechanics
• Human Factors Engineering
• Occupational Health

Background:

• Military aviators frequently report neck pain (NP).
• Risk factors for NP include head-supported mass, awkward postures, and mental workload.
• Interactions between these factors may explain constant low-level muscle activation during helicopter flight.

Purpose of the Study:

• To assess neck muscle activity under varying interactions between helmet, posture, and visual stress.
• To investigate the biomechanical effects of a simulated "helo-hunch" posture on military aviators.
• To understand the contributing factors to neck pain in aviators.

Main Methods:

• Neck muscle electromyography (EMG), head kinematics, subjective discomfort, perceived workload, and task performance were measured.
• Sixteen subjects performed eight 30-minute test conditions with varied physical loading (helmet donned/doffed), posture (symmetric/asymmetric), and visual stress (low/high contrast).
• Testing occurred in a simulated "helo-hunch" seating environment.

Main Results:

• Wearing a helmet reduced EMG median frequency cycles in the left cervical extensor and left sternocleidomastoid.
• Asymmetric posture increased normalized EMG activity in the right cervical extensor and left sternocleidomastoid.
• High visual stress reduced EMG cycles in the right cervical extensor.

Conclusions:

• A complex interaction exists between helmet load, postural stress, and visual stress in the "helo-hunch" posture.
• These findings offer insights into how visual factors influence biomechanical loading.
• Results can inform the design of controls to mitigate neck pain in aviators.