Risk factors associated with live fire training: Buildup of heat stress and fatigue, recovery and role of micro-breaks

Abstract

BACKGROUND: Forty five percent of on-duty firefighter deaths every year are cardiovascular (CV) related. Heat stress and fatigue buildup are two common occupational risk factors for firefighters. These risk factors may increase the firefighters’ chances of having cardiac events or even death. OBJECTIVE: Buildup of heat stress and fatigue in firefighters and their recovery from these stresses during live-fire training exercises was investigated. METHODS: Twenty full time firefighters, from two different fire-stations, performed live-fire training exercise constituting three real life firefighting scenarios and rest periods incorporated in between the scenarios. Core body temperature (CBT) and heart rate (HR) were measured in real time, using an FDA approved radio pill and a polar heart rate belt. Baseline and post-scenario measurements of perceptions of physical exertion, thermal stress and respiratory distress were also collected. RESULTS: Heart rate and CBT increased significantly with the progression of the training. The HR and CBT levels at the end of each rest period were significantly higher than the baseline values. The actual rest periods provided after each scenario were shorter than the time needed for adequate recovery. Most of the firefighters crossed the industrial limit of hyperthermia and maximum recommended level of HR elevation from baseline. Firefighters from one of the stations took micro-breaks during scenarios and were found to spend less percent time over the limit of hyperthermia. These firefighters also needed less time to recover to baseline levels of HR and CBT. CONCLUSIONS: There was significant heat stress and fatigue buildup as a result of the live-fire training exercise. Longer rest periods should be provided between scenarios to ensure recovery. Also, taking micro-breaks during a live fire training scenario might help in preventing heat stress and fatigue buildup.