Exploring heart rate variability as a human performance optimisation metric for law enforcement

Tactical personnel, inclusive of police officers, face complex challenges over potentially decades-long careers. These cumulative exposures may manifest as allostatic load, impairing health, fitness, and performance. Allostatic load describes increased vulnerability to psychophysiological dysfunction resulting from prolonged overstress exposure. Monitoring for this risk is an important step towards its mitigation. Heart rate variability (HRV) analysis can noninvasively acquire psychophysiological overstress information in tactical environments. HRV theory and principles are well established, however, the integration of HRV in tactical workflows, especially for end-users, has received limited research attention. Therefore, the overarching aim of this programme of research was to determine the utility of HRV assessment in the support of specialist police and their organisations and to alert stakeholders to potential instances of psychophysiological overstress. Chapter 1 introduces HRV concepts within tactical contexts. Components of tactical work that may be best appreciated with HRV analysis are highlighted. Principles in this introduction are further articulated in a systematic review (Chapter 2). Chapter 2 reports on the undertaken systematic review which summarised and critically appraised studies of HRV applications across tactical populations. Of 296 initially identified studies, twenty were included. The volume of evidence suggested that HRV effectively supports health and performance measures in tactical environments. However, literature gaps were identified; most notably, there was limited evidence available regarding HRV in specialist police professions, thus warranting this research. As professional requirements and potential allostatic load sources differ during specialist police selection and subsequent specialist police operational contexts, two research arms were devised to pragmatically address this critical gap. Chapter 3 illustrates the research structure in further detail and outlines which studies address specific literature gaps within specialist police and in which of the two developed research arms. Methodological approaches are also described. Chapters 4, 5, 6, and 7 encompass HRV application in initial specialist police selection. Chapter 4 introduces the first field study, building on the findings from Chapter 2 (Studyiii1) that HRV assessment may be more valuable than traditional heart rate (HR)measurement for monitoring tactical training as HRV is capable of measuring stress holistically. The primary aim therefore was to investigate whether HRV was more sensitive than HR at monitoring workload during specialist police selection activities. As aerobic fitness is associated with workload during these tasks, a secondary aim was to investigate relationships between HRV, HR, and maximal aerobic fitness. As illustrated by a time-series plot, HR values were unremarkable while HRV values were potentially depressed, and tentatively indicative of overstress. Estimated maximal aerobic fitness (20-m shuttle run) was significantly positively correlated with HRV, but there was no relationship with HR. When a linear regression model was applied, neither HRV nor HR were predicted by 20-m shuttle run scores. Chapter 5 aimed to determine the effectiveness of HRV in differentiating between candidates that failed to complete specialist selection from those who succeeded. HRV was defined as the percentage of R-R intervals that varied by at least 50ms (pRR50). Data were summarised in a heat map. A logistic regression model was generated that effectively predicted attrition but did not identify the most successful candidate. Therefore, the aim of Chapter 6 was to profile HRV characteristics of that successful candidate and consequently a detailed HRV time series plot was generated. Contextual analysis was applied, and the candidate demonstrated continued performance even under apparent duress, both physical and psychological in nature. The subsequent studies (7-9)then aimed to consider HRV monitoring at the operational level where such duress exposures occur frequently. Noting that success in training is distinct from operational performance, Chapters 7, 8, 9,and 10 examined the use of HRV monitoring in operational contexts. The purpose of Chapter 7 was to identify if HRV analysis could classify candidate performance in specialist police selection during occupationally realistic tactical operations scenarios which required fluid psychomotor skills, teamwork, and leadership while under duress. Qualitative analysis of descriptive statistics indicated that the HRV data of one participant were substantially different from his peers. This candidate was also the highest performer, suggesting a relationship between HRV and occupational aptitude. Given that specialist police often work rotating shift schedules which may lead to sleep deprivation, introducing another source of allostatic load, the aim of Chapter 8 was to determine the extent to which HRV may detect differences between specialist police that worked an overnight shift and those that were off duty overnight. HRV was analysed in11 male specialist police officers who were either off-duty or on overnight duty prior to engaging in specialist assessment activities. All officers experienced HRV perturbations from the assessment, but post-assessment HRV was greater amongst those who were coming on duty. HRV values continued to decline after assessment success amongst those that worked the night prior to training, potentially indicating greater stress loads in those that worked the overnight shift. Chapter 9 further explored HRV changes observed in Chapter 8. The aim was to identify relationships between physical fitness as measured by completion time on a primarily anaerobic occupational obstacle course, and HRV response during firearms qualification and subsequent stress training. HRV was assessed as the within-operator change from pre- to post-qualification and post-training. HRV was reduced after training but not after qualification. A linear regression model indicated that obstacle course completion time predicted HRV changes from baseline to both post-qualification and post-training. While stressful training and overnight shifts are regularly encountered in specialist police work, other tasks, such as serving in Directing Staff (DS) roles on selection courses for future candidates are also important duties and present as a nexus between operations and selection. Thus, Chapter 10 considered the critical operational role of DS cadre. The purpose of this study was to monitor and analyse the HRV of one DS member during their 24-hour shift on a candidate selection course. The findings of this case study suggested that DS may be subject to stress levels not unlike those of candidates. This is of note as selection courses are highly taxing and arduous, and officers may serve as DS on more than one course per year and still be required to perform their operational duties.DS requirements during selection courses should therefore be considered appropriately in the overall deployment and operational task scheduling paradigm.Each previous chapter considered important elements of service in a specialist police organisation. The final chapter (Chapter 11) summated the findings from this programme of study, contextualised the works in terms of the bodies of literature with which they were most associated, and highlighted overall limitations as well as plausible future directions. A final supplementary chapter, aimed to provide an operational guide for utilising HRV data in tactical settings, contributed to further support translation of research to practice. In this supplementary chapter, shortcomings of using HRV were reviewed and solutions to avoid flawed analysis provided, as are the key lessons learned from this thesis. In essence, the presentation and visualisation of HRV data may be as critical to the application of HRV analysis as the measurements themselves in tactical settings

The impact of body armor on physical performance of law enforcement personnel: A systematic review

Abstract Background The law enforcement officer profession requires performance of arduous occupational tasks while carrying an external load, consisting of, at minimum, a chest rig, a communication system, weaponry, handcuffs, personal protective equipment and a torch. The aim of this systematic review of the literature was to identify and critically appraise the methodological quality of published studies that have investigated the impacts of body armour on task performance and to synthesize and report key findings from these studies to inform law enforcement organizations. Methods Several literature databases (Medline, CINAHL, SPORTDiscus, EMBAS) were searched using key search words and terms to identify appropriate studies. Studies meeting the inclusion criteria were critically evaluated using the Downs and Black protocol with inter-rater agreement determined by Cohen’s Kappa. Results Sixteen articles were retained for evaluation with a mean Downs and Black score of 73.2 ± 6.8% (k = 0.841). Based on the research quality and findings across the included studies, this review determined that while effects of body armour on marksmanship and physiological responses have not yet been adequately ascertained, body armour does have significant physical performance and biomechanical impacts on the wearer, including: a) increased ratings of perceived exertion and increased time to complete functional tasks, b) decreased work capability (indicated by deterioration in fitness test scores), c) decreased balance and stability, and d) increased ground reaction forces. Conclusions Given the physical performance and biomechanical impacts on the wearer, body armour should be carefully selected, with consideration of the physical fitness of the wearers and the degree to which the armour systems can be ergonomically optimized for the specific population in question

Field monitoring the effects of overnight shift work on specialist tactical police training with heart rate variability analysis

Police work exposes officers to high levels of stress. Special emergency response team (SERT) service exposes personnel to additional demands. Specifically, the circadian cycles of SERT operators are subject to disruption, resulting in decreased capacity to compensate in response to changing demands. Adaptive regulation loss can be measured through heart rate variability (HRV) analysis. While HRV Trends with health and performance indicators, few studies have assessed the effect of overnight shift work on HRV in specialist police. Therefore, this study aimed to determine the effects overnight shift work on HRV in specialist police. HRV was analysed in 11 SERT officers and a significant (p = 0.037) difference was found in pRR50 levels across the training day (percentage of R-R intervals varying by >50 ms) between those who were off-duty and those who were on duty the night prior. HRV may be a valuable metric for quantifying load holistically and can be incorporated into health and fitness monitoring and personnel allocation decision making