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Police Performance Under Stress

Since lower stress levels potentially equate to greater chances of winning critical encounters, police trainers strive to facilitate the achievement of “optimal performance” for their officers through various techniques. These include skill proficiency, biofeedback (heart rate and breathing), reality-based training (RBT), and even through actual experience such as that found in FTO programs.

Since perceptions and emotions play a large role in one’s reaction to stressors, they cannot be ignored in policing. This is a profession in which officers are sometimes unrealistically expected to be unemotional and composed at all times. Just what exactly is stress and how does it affect performance?

In one of the most comprehensive definitions, McGrath defines stress as the “interaction between three elements: perceived demand, perceived ability to cope, and the perception of the importance of being able to cope with the demand.” This definition encompasses not only an officer’s own skill and confidence compared to the task at hand, but also the relative importance of handling the challenge successfully.

Stress in law enforcement can range from a rookie handing out his very first citation to a seasoned veteran responding to a lethal attack. It can encompass taking a sniper shot from a rooftop, dealing with an irate citizen, or even experiencing an inflamed internal affairs complaint initiated by a malicious command officer. While each stressor has its own characteristics, the toll on the human body can be exceedingly destructive if not dealt with properly.


The pursuit of performing well under stress is certainly not new to the police profession. Most of our research comes from the field of psychology. More recently and more specifically, the field of sport psychology has contributed to the journey.

Yerkes and Dodson related stress and performance a century ago when they studied rats placed under induced “stress” consisting of a mild electrical shock. Their findings eventually led to the “Inverted-U Theory.” This basically suggests a relationship between performance and stress in the shape of an upside-down “U.”

In other words, as stress increases, performance improves up to a point. After this peak point, stress begins to become too great, and then performance diminishes. Although not without its critics, the theory has withstood the test of time because it makes intuitive sense and is virtually impossible to disprove. Of late, however, the field has moved on to more acceptable theories that encompass many differing variables. So why hasn’t the police profession moved ahead as well?

Optimal Performance Zone

Since heart rate is one of many factors that can indicate stress levels in most people, Siddle took this a step further and attempted to put actual heart rate values on the Inverted-U. An “Optimal Performance Zone” was created with a range of 115 to 145 beats per minute (bpm). This zone was based on the onset of physical skill loss / improvement at specific heart rates.

The studies Siddle used to incorporate heart rate into a generalized optimal performance zone, however, involved physical exertion rather than psychological and/or emotional stress. There may not have been at the time, but now there is a well-established difference between heart rate elevation due to physical exertion and heart rate elevation due to stress. It would be difficult, at best, to generalize one to the other.

Although the Inverted-U Theory is well-known within the police training arena, many essential components have unfortunately been omitted or forgotten over the years. Siddle included these components in his book “Sharpening the Warrior’s Edge.” However, much of the information has been left behind.

For example, even in basic psychology text books, both task complexity characteristics and personality characteristics are mentioned as affecting one’s performance, relating these characteristics to an individualized Inverted-U. Rarely, if ever, are these mitigating factors even mentioned in defensive tactics programs.

Anxiety and Task Complexity

Let’s define two terms of anxiety. Trait anxiety is a person’s general predisposition to respond across many situations with high levels of anxiety. State anxiety is a person’s anxiety at a particular moment. Generally, the higher the trait anxiety, the higher the state anxiety.

Task complexity is influenced by a number of components and is broken down into three categories. First is decision characteristics (number of decisions necessary, number of alternative decisions, speed of decisions necessary, required sequence of decisions). Second is perception characteristics (number of stimuli needed, number of stimuli present, duration of stimuli, intensity of stimuli, and clarity of correct stimulus among conflicting stimuli).

Third is motor act characteristics of the skill (number of muscle actions needed to execute the skill, the amount of coordination of actions required, precision and steadiness required, and fine motor skills required).

Based on a point system to determine the overall “complexity score” of any given task, the higher the complexity score, the lower the stress level should be for optimal performance. Conversely, the lower the complexity score, higher levels of stress are acceptable to successfully complete the task.

Hence, someone performing a very complex task who also happens to have high trait anxiety and high state anxiety will perform worse than someone who has low state and trait anxiety performing a simple skill. Even Yerkes and Dodson a century ago realized that each person would have his own individualized “Optimal Performance Zone” based on personality and task complexity characteristics.

Relating this to police positions, a SWAT team would certainly want a “calm, cool and collected” personality on the trigger of a sniper rifle and an adrenaline-pumped muscle-head on the business end of a battering ram. At any rate, Siddle’s basic concepts had a positive influence on police physical skills training in that skill simplicity with teaching physical skills was emphasized (gross motor skills) as well as controlling stress via influencing heart rate by controlling respiration.

IZOF Model

Because humans are so different and complex, attempting to categorize or generalize an optimal performance zone to one specific heart rate range would be virtually impossible. Rather than trying to reinvent the wheel, the police profession may be better off looking to the athletic profession in terms of improving physical and mental skills under elevated stress levels. When comparing athletes to officers and operators, both must perform physically and cognitively well while experiencing elevated stress.

Skill level, training, and physical fitness all affect performance, and there are consequences to poor performance, although more severe in the police profession with the potential loss of life. Professional athletic organizations have spent millions of dollars developing techniques and systems for improving physical and mental performance under stress. Why not tap into that which has already been developed?

In the IZOF Model, or the “Individual Zones of Optimal Functioning,” personality characteristics, maturity level, trait anxiety, state anxiety, coping skills, task complexity and skill proficiency all play a part in determining one’s performance levels and optimal zones.

Additionally, these zones are not without change and will cultivate based on personal development, physical skill improvement, maturity, and practical experience. This, of course, is much more complex and difficult than the simple Inverted-U Theory with definitive heart rate zones plopped onto the graph, but human performance is very complex!

Empirical Heart Rate Data

Heart rate data has been collected by LouKa Tactical Training for the past six years using the Polar S810 heart rate monitor in many arenas including police academy physical fitness sessions; police academy firearms training sessions; police academy emergency vehicle operations; police academy RBT in Ann Arbor, MI; in-service RBT across the country; on-duty actual incidents, with and without physical exertion; and during one officer’s voluntary TASER® exposure.

Some general observations could be made based on the empirical heart rate data collected. There was no specific heart rate range for “optimal performance” that could be generalized to everyone. Some cadets and most officers did not lose fine and complex motor skills at elevated stress levels as indicated by heart rate. Very few (but some) lost most skills during low stress incidents. This could be because of any number of things such as a lack of police experience, a lack of maturity, a new task versus trained task, high trait anxiety, and/or high state anxiety.

Absent physical exertion, the lower the heart rate curve, the better the performance. The higher the HR curve, the worse the performance, although not necessarily bad or catastrophic performance. The more frequent the HR spikes, the worse the performance, and in very rare cases, even catastrophic performance.

Experience related most to proficient performance and to lower heart rate curves, as can be witnessed by overlapping HR graphs of in-service officers of varying levels of experience.

For example, two officers participated in RBT as partners. Each had a different number of years working the street and thus differing levels of “street experience.” Both were exposed to identical stimuli in RBT, but the officer with more experience will almost always show a lower HR curve than the more inexperienced partner, sometimes up to 40 to 50 beats per minute lower.


Utilizing biofeedback, i.e., heart rate and respiration rate, is but one of many possible interventions to stressful situations. Recording and downloading heart rate data can provide valuable information to cadets, in-service officers, FTOs and police trainers. This can lead to improved performance on the street. Other interventions exist. Training to skill proficiency leads to higher confidence, which results in better performance under stress.

Reality-based training (RBT) is, of course, another great tool to stress inoculation and improving performance. Keep in mind, however, that even RBT loses its stressor capabilities with seasoned veterans who experience it on a regular basis. The challenge to RBT trainers is keeping the scenarios realistic while still inducing a startle or stress response.

Imagery, mental rehearsal and positive self-talk are powerful tools in controlling stress, performance, and ultimately outcomes. An offensive rather than defensive mindset will help the officer formulate a plan in advance and expect the worse, thus staying ahead of the reactionary curve. Concentration skills development can help an officer stay focused on the immediate task at hand while minimizing distractions.

Physical Fitness

With physical exertion, proficient performance was observed in “stressful” incidents by self-proclaimed “physically fit” officers. Less proficient performance and elevated heart rates were observed in self-proclaimed “physically unfit” officers.

An exercise routine not only releases endorphins on a regular basis, but also improves skill level and confidence. Appropriate body weight allows for efficiency of movement in emergency situations. Open-chained or reactionary drills add to the ability to react to physical stimulus.

Plyometrics (explosive muscular movements) greatly improve police-specific striking, kicking, and sprinting abilities, which can all equate to elevated performance on the street. A physically fit body has more efficient heart and lung capacity during stressful situations.

The cardiovascular system is able to recover quickly after physical demands. Respiratory muscles can shuttle more oxygen to the brain and muscles. Bone, tendon and muscle strength result in less likelihood that an officer will be put out of the fight due to injury. If an inevitable injury does occur, a fit body has a higher tolerance to pain and stress, which just might be the difference in a life-or-death struggle.

Proper nutrition and a constant blood sugar level are imperative as the brain and muscles require adequate carbohydrates to perform optimally when the “fight-or-flight” system is activated. This can result in clearer mental functioning under stress, and efficient and powerful muscular movements.

This is easily achieved by keeping pre-planned food available at all times and snacking every few hours. Adequate carbohydrates are imperative to muscle and brain function, and adequate protein is needed to maintain adequate muscle, tendon and ligament strength to perform the emergency task without injury.

Looking to the Future

Monitoring heart rate is one of many methods to keep track of and control stress levels for some people. It is still a valuable tool for police and military trainers who strive for current and future performance-improving applications.

Heart rate graphs are currently being used to provide objective data to support dismissal from basic academies when deficient performance is present during RBT. They are currently being used in FTO programs and in-service RBT for awareness of one’s own performance zone. Heart rate monitors could be useful during emergency response and vehicle pursuits in the future, and they may even have a place in the career-selection process (not everyone was meant to be a police officer). More specifically, they may be used for selections relating to fitness such as bicycle patrol, as well as for stress performance positions and for specialty-within-specialty positions such as a sniper on the SWAT team.

The “gold” standard, of course, would be actual on-duty incidents. Perhaps one day there may even be a “heads up” display in an officer’s patrol vehicle along with a real-time monitor in the communications center as the officer pursues an armed robbery suspect during a high-speed pursuit. Abnormally high readings may trigger a calming voice over an internal speaker to bring the officer’s stress level back into his personal IZOF.

Whatever the future, heart rate monitors are certainly not “the only tool” but they have the potential to be “one of the tools” in the field of optimal human performance.

Kathleen Vonk has worked the street since 1988, currently with the Ann Arbor, MI Police. She has a B.S. in exercise science and a B.A. in criminal justice. She designed and implemented a Police Wellness Instructor program for the Michigan Commission on Law Enforcement Standards, which can be tailored to any state. She can be reached at

Published in Law and Order, Oct 2008

Rating : 10.0

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Posted on : Jan 8 at 9:45 AM By Franklin

Siddle has no college degree and no military service. Yet he is quoted over and over and over, finally someone has questioned his writing.

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