Effect of Two Common Head-Mounted Augmented Reality Systems on Muscle Force and Blink Rate of Electric Utility Power Plant Operators

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Augmented reality (AR) is a technology that combines real and virtual information presented to the user in an interactive way in real time. The Microsoft HoloLens and RealWear HMT-1 are two common types of head-mounted AR available to industrial field workers. These two AR systems were tested on how they affected blink rate, an indicator of eye strain, and electromyographic (sEMG) activity of the neck and shoulder muscles of electric utility power plant operators while they performed five routine inspection tasks of coal equipment. The inspection tasks were conducted under three conditions: HoloLens, HMT-1, and No AR (regular method). Workers communicated with the HoloLens with a right-hand gesture and by voice input to the HMT-1. The duration of the inspection tasks ranged from an average of 10 to 28 sec. Twelve experienced power plant operators participated in the study. sEMG) of the right and left sternocleidomastoid, splenius, semispinalis capitis, and upper trapezius muscles were measured, and a small camera recorded blink rate of the right eye. Results reveal generally no significant differences in 50th and 90th percentile sEMG between the three conditions for all eight muscles. Although the means of blink rate appeared consistently lower with the HoloLens than the No AR and HMT-1 (approximately 4.4 blinks/min), these differences were not significant at the 0.05 level (p=0.06 to 0.17). Future studies should investigate a larger sample size of workers wearing AR devices for longer time periods (> 30 min) to determine long-term effects of AR devices on muscle activity and eye strain. A system of hardware, software, and experimental protocol was developed that follow-up studies may employ to test physiological effects of AR devices.