Incorporation of heart rate variability into police tactical group small unit tactics selection

Objective:
Police tactical group (PTG) occupational requirements are known to expose officers to high levels of physical, mental, and emotional stressors. As such, selection courses must ensure candidates are not only physically, but mentally and emotionally suitable. Assessing personnel for suitability requires a holistic approach; wearable technologies may provide organizational decision makers additional objective information to optimize candidate selection. Heart Rate Variability (HRV), one metric obtainable from wearable technology, has been increasingly utilized as a stress biosignal, but the value of HRV data in the context of specialist police selection remains limited.

Hypothesis:
HRV analysis will effectively identify higher performing candidates attending PTG selection?

Methods:
This study was a prospective cross-sectional study of three male PTG candidates completing a highly demanding selection course. HR and HRV were measured from 1300 – 1800 on a single day of tactical maneuver training. HRV was analysed as follows: R to R interval (RRI) length, root-mean-square of successive RRI differences (RMSSD), percentage of adjacent RR intervals varying by at least 50ms (pRR50), nonlinear short-term variability (SD1), and nonlinear long-term variability (SD2).

Data:
Measures of central tendency were generated; the maximum, minimum, mean, and standard deviation were reported for each HRV measure and visualized with a box plot.

Results:
Data from one participant appeared to skew the mean results. The maximum values for mean RRI (Max: 709ms, Min: 580ms, Mean: 632.67±67.68ms), RMSSD (Max value: 42.3ms, Min value: 18.8ms, Mean: 26.8±13.43ms), pRR50 (Max value: 12.47%, Min value: 1.98%, Mean: 5.76±5.82%), SD1 (Max value: 29.9ms, Min value: 13.3ms, Mean: 18.93±9.50ms), and SD2 (Max value: 61.1ms, Min value: 37.5ms, Mean: 49.87±11.84ms) all occurred in the same participant. That participant also held the lowest maximum HR (138bpm), lowest mean HR (85bpm) and was the highest performer as rated by unit leadership.

Conclusions:
Given the potential discriminatory capacity of HRV in this context, HRV may be a valuable objective metric to support PTG candidate selection by providing objective measurements of holistic stress response.