Firing of a Cannon: Psychophysical Evaluation of Ergonomic Hazards

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Musculoskeletal-related occupational illnesses and injuries comprise a large majority of military medical encounters and result in decreased combat readiness and degraded human performance. The United States of America has the most sophisticated and technologically advanced military in the world. Consequently, they are constantly challenged with the requirements of reducing health hazards associated with the use, maintenance and testing of new and evolving technology. Ensuring the well-being of personnel operating, maintaining or testing military equipment is paramount to mission success. Heavy artillery tasks when deployed to combat zones are notoriously dangerous. Our study to evaluate the ergonomic risk factors of a heavy artillery task was initiated because military personnel had experienced a high rate of injuries during routine heavy artillery training exercises after returning home from combat. A three day study was conducted that spanned a complete heavy artillery firing exercise. Twenty-five military personnel were interviewed about their prior injury experience during the first day, while the cannons were being set-up. The live-fire exercise was directly observed by the research team on days two and three, and video recordings were taken for subsequent analysis. Non-invasive verbal inquiry every 8 to 12 minutes was used to collect psychophysical measures of exertion, fatigue and pain using the Borg Scale. Human errors in executing the established SOP for firing the cannon were counted during the exercise and verified during the video analysis. Twenty-five personnel were evaluated during the study. Sixteen of 25 (64%) reported becoming injured during a routine training exercise after returning home from combat, and four (16%) were on limited duty because of an injury suffered prior to our study. Of the sixteen previously injured personnel, nine (56%) reported injuries that were related to their back. Ten of the sixteen (62%) previously injured personnel recalled becoming injured while lifting or moving cannon rounds. Personnel perceptions of exertion, fatigue and pain increased throughout each day over the course of both days. In addition, the number of errors committed by personnel also increased over the course of each day. The recommended crew size for firing the cannon was ten, but due to personnel on limited duty assignments or injured, crew sizes of only 6 and 7 personnel per cannon were observed. The small number of personnel per cannon limited task rotation and increased the workload for the operators. Battlerelated injuries are often considered to be the major source of disability for military personnel and soldiers are often considered at a low risk of injury while stationed in home port. Our study uncovered that the exposure profile during a routine training exercise led to degradations in performance and increased the risk of developing musculoskeletal disorders. Recommendations included maintaining the recommended crew size to allow for task rotation; reducing the rounds fired per exercise; proving aids to raise cannon rounds from the ground level; and a redesign of the loading tray task. A biomechanical analysis of the high-risk tasks involved in heavy artillery firing is warranted given the high rate of injuries suffered by military personnel.