Orange County (CA) Fire releases study on the connection between cardiovascular strain, heat stress

In an effort to gain insight into the job demands placed on firefighters, the Orange County Fire Authority (OCFA) embarked on a week-long Hydration and Core Body temperature Study at its Regional Fire Operations & Training Facility in August of 2007. The startling results were released Thursday, January 24.

“What stunned us the most was the 91 percent of participants were dehydrated prior to commencing the study,” said Captain Mike Contreras, Wellness & Fitness Coordinator. “We need to reducate firefighters on the signs of dehydration and the potentially
detrimental health and performance effects to help them understand the importance of being properly hydrated prior to an incident, as well as maintaining an optimal hydration level both during and after an incident.”

The study evaluated 126 Orange County firefighters on the effects dehydration and physical stresses placed on them while performing their rigorous duties. It confirmed that firefighters are required to work at a high intensity and that they may also be required to maintain those high work levels for extended periods of time. The personal protective gear (PPE) worn by firefighters weighs up to 60 pounds, and the additional weight alone places an increased demand on the cardiovascular system. So, given the stringent physical demands inherent in the profession, firefighters must be aware of risk factors that may impact cardiovascular health. The same goes for working in hot environments. The high temperature of fire, sometimes combined with high outside temperatures, creates a dangerous environment for firefighters who may be carrying 60 pounds of protective gear and another 40 pounds of fire suppression equipment. The study concluded that firefighters should apply cooling measures as soon as possible after physical activities–especially intense firefighting tasks– to lower their eventual peak core body temperature. One important finding is that even after 20 minutes of rest, few core body temperatures had returned to starting temperatures.

The study shows the connection between cardiovascular strain and heat stress and what can be done to minimize the increase in core body temperature during an incident. It also calls for some action items including educating firefighters on proper hydration and overall fitness, establishing medical screenings for firefighters, and developing rehabilitation protocols. You can view the final report in its entirety on our Web site at

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