Firefighting activity is associated with an increased risk of sudden cardiac events. Kales and colleagues have shown that firefighters are 14 times more likely to suffer a sudden cardiac event following an alarm and 136 times more likely to have a sudden cardiac event after fire suppression activities (Kales et al., 2007). Therefore, we investigated heart rate responses to alarms and to working fires, and examined that data when firefighters were placed into categories based on age, BMI, and fitness level.
Cardiac instability (as measured by heart rate variability) is greater in older firefighters than younger firefighters at rest, potentially explaining some of the increased risk of sudden cardiac events in this group. Low-fit firefighters had greater cardiac instability at rest when compared with aerobically trained firefighters. There is a sudden and marked increase in heart rate in response to an alarm, and heart rate response is greater to a potential structure fire than other emergency calls. Peak heart rate responses to a strenuous fire call can reach high levels. We reported average peak values of approximately 160 bpm in our crosstrained firefighters, with individual peak values as high as 180 bpm.
Our data suggest that cross-trained, younger, and leaner firefighters are able to perform more work and thus achieve higher heart rates during strenuous firefighting activities.
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I hope they did not spend a whole lot of money figuring that out.