Applications of heart rate variability monitoring in tactical police training

Purpose: Police work is known to be a physically, mentally, and emotionally demanding profession. Special Emergency Response Teams (SERTs) are tasked with responding to the most high-risk scenarios. Further, many SERT operators serve on teams as a collateral duty beyond their regularly scheduled police work. As such, these personnel often attain very high levels of physical fitness but may be vulnerable to accumulating excessive chronic stress. Heart rate variability (HRV), the analysis of the difference in time between individual beats of the heart, shows promise as a field measurement of holistic load because of its sensitivity to the dynamic regulatory patterns that both intrinsically and extrinsically regulate cardiac activity. However, little HRV research has been conducted to date among SERT personnel. 
Methods: The aim of this study was to identify potential relationships between a measure of physical fitness (occupational obstacle course completion time) and time-domain HRV (pRR50) in a pilot cohort of SERT personnel. This research was conducted in compliance with the Declarations of Helsinki and with IRB approval. Prospective 3-lead ECGs were captured from 8 male SERT operators prior to and following a firearms training event. HRV was assessed as the within-operator change from baseline to post-training of the percentage R-R intervals varying by 50 ms (∆pRR50). 
Results: Obstacle course time correlated significantly with ∆pRR50 r(8) = 0.712, p = 0.048. More fit operators (as measured by obstacle course time) were more resilient to HRV changes during training. 
Conclusions: These results indicate the HRV monitoring is feasible in the field environment and can provide human performance optimization personnel with an additional meaningful tool for the objective measurement of stress in a tactical police environment. Organizations should promote fitness in personnel and may especially consider anaerobic capacity and recovery as a means of mitigating stress vulnerability based on the results of this study.
Practical Applications: These results establish precedent for further investigations into HRV monitoring utilization in tactical police units. The findings of this study also indicate that more fit operators were more physiologically resilient to demands imposed by the training exercise. Specifically, anaerobic capacity and recovery may be key performance indicators within this population and warrant further investigation. TSAC practitioners may consider utilizing HRV measurement to support human performance optimization efforts within their organizations.