(72) PHYSIOLOGICAL STRESS ACCUMULATION IN LAW ENFORCEMENT OFFICERS ACROSS A MULTI-DAY ACTIVE SHOOTER TRAINING COURSE

Purpose: Research on active shooter scenarios in law enforcement has typically focused on officer performance, rather than the physiological demands of these activities. Heart rate variability (HRV) provides an indication of physiological stress and has been used in tactical populations, where higher HRV is indicative of readiness. The purpose of this study was to investigate the physiological stress accumulation (measured via HRV) in law enforcement officers (LEO) during a multi-day active shooter training course. Methods: Data for seven officers (age: 37 ± 12.12 years; height: 176.71 ± 8.66 cm; body mass: 90.26 ± 18.50 kg) were collected during a four-day active shooter training class which included multiple scenarios and officer interactions with a “shooter” and/or “victim”. Zephyr heart rate (HR) monitors were used to collect physiological data (HR and HRV), while training duration was recorded by researchers. Each day was broken down into active (scenario participation), inactive (practice, rest or briefing), and total training time for analysis. The Zephyr devices measure HRV using an algorithm that calculated a rolling 300 beat standard deviation of the normal-to-normal intervals (SDNN). A repeated measures ANOVA was used to identify changes in active, inactive, and total HR, HRV, and training durations across the four-day training course, with significance set at p ≤ 0.05. Results: Active and total HRV was significantly lower on day four compared to day two (p ≤ .001 and .008, respectively), while there was no significant difference in inactive HRV. Total HR was significantly higher on day one compared to days two and three (p = .033 and .002, respectively), and was significantly lower on days two and three compared to day four (p = .021 and 0.18, respectively). Scenario times were significantly longer on day one than any other training days (p ≤ .005), and day two was significantly shorter than all other training days (p ≤ .001). Conclusions: HRV was significantly reduced over the four days of training, suggesting that the participating LEOs accumulated physiological stress during the course. The first and last days of training elicited higher HRs during scenario participation than the other training days, presumably due to day one being the first introduction to the scenarios, and day four being the longest duration scenarios that were reflective of the culmination of skills. Additionally, day one resulted in the lowest amount of inactive time compared to all other training days (p ≤ .02), which could indicate that there were insufficient recovery periods between scenarios to reduce HR. Practical Applications: HRV has been shown to be sensitive to cognitive processing tasks, especially when sustained attention is required. While an active shooter training course is not necessarily indicative of the daily tasks of LEOs, the prolonged and observed physiological stress that is accumulated could be representative of variable shift work, special teams and assignments, and in worst case scenarios, real-world active shooter events. Acknowledging the physiological responses of officers during active shooter training for various scenarios may inform future training sessions (e.g., decision-making and shooting with elevated HR, breathing techniques, etc.). This information may also strengthen the need for officers to engage in recovery techniques to reduce the amount of stress, both physiological and psychological, that they accumulate on the job. Acknowledgements: None