Neck Muscle Activation Levels During Frontal Impacts
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH HUMAN EFFECTIVENESS DIRECTORATE
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Helmet-mounted systems, such as night vision goggles and helmet-mounted displays, are designed to enhance pilot performance however, they may also affect pilot safety during ejection due to the change in helmet inertial properties. The effects of variable helmet weight and bracing ability on subject response during impact are unknown. Electromyogram EMG is a useful tool to investigate the mechanics of bracing and the relationships to helmet weight and impact acceleration. In addition, EMG could be used to help establish the relationship between the potential for neck injury and the force exerted by the neck muscles due to bracing. EMG can be used to determine the activation timing of the muscles and to estimate the force produced by the muscles in a dynamic environment. A series of tests were conducted on a Horizontal Impulse Accelerator using male and female volunteers to investigate the effects of helmet weight on human response to short-duration frontal impacts of variable magnitude. Helmet weights ranged from 0 lb no helmet to 4.5 lbs, and acceleration levels were 6, 7, 8 and 10 g. The MyoMonitor Portable EMG System by DelSys was used to collect data from ten subjects. The electrodes were placed on the right and left upper trapezius and sternocleidomastoid. Amplitude and frequency components of the signals were evaluated to determine the amount of force exerted by the muscle. Root Mean Squared RMS amplitude analysis indicated that, in general, the muscular strain increased with increasing Gx acceleration levels. The trapezius produced more force than the sternocleidomastoid. Activity of both muscle groups was synchronized, by their RMS values, with head and neck motion. A method of collecting EMG data during short-duration impact accelerations was developed. It was demonstrated that in fact the neck muscles can respond quickly to the short-duration impacts.
- Anatomy and Physiology
- Protective Equipment