Why Our Heart Rate Spikes When We're Stressed
Stress, behavior, and the modern world.
Posted March 13, 2023 | Reviewed by Devon Frye
- Many modern people, including many modern first responders, are under increasing stress.
- This stress can produce behaviors which can prove essentially self-destructive.
- Elements of this situation may have derived from adaptations to the ancient world that are no longer useful.
- Awareness of the sources and characteristics of our stress responses can help us to deal with them in the modern world.
Clinical colleagues inform me that they are seeing dramatically rising levels of stress in their clients and patients. This is especially true for law enforcement officers and other first responders, who must perform their duties with substantially fewer resources and a substantially higher operational tempo than were typical even a few years ago. But in a very real way, the average person under stress is in a similar if somewhat less operationally-hazardous boat.
Rising stress produces medical dangers, of course. But we also see substantial dangers to our well-being in our own psychology and behaviors, especially under enhanced levels of pressure and tension.
One fairly good if somewhat limited way of assessing human stress lies in the measurement of heart rate. Medical authorities seem to be in agreement that normal adult human heart rates range between 60 and 100 beats per minute, with most healthy people congregating toward the lower part of that spectrum. This range of heart rates is where we are healthy, and within that range, lower is typically better. So why on earth are we able to experience higher and more destructive heartbeat ranges when we're under greater stress?
The psychology of first responders shows us the reason. Normal heart rates are simply not high enough to provide enough bloodborne resources to cope with the exigencies of tactical stress, whether it involves fighting off assailants, running from predators, or exerting ourselves to save babies from burning buildings. For these higher-stress situations, most authorities are in agreement that the proper heart rate zone is 115 to 135 beats per minute (some authorities add a few extra points to that range, but they are in the minority).
This higher range of heart rates allows us access to a broader spectrum of the types of behaviors we're likely to need under high stress. The adrenergic activity of the "HPA Axis" (Hypothalamus-Pituitary-Adrenal system), which operates most strongly under conditions of high physiological demand, gives us more bloodborne resources where they are needed. These in turn allow us greater physical strength, greater physical endurance, greater speed, and even greater resistance to pain. This enhanced physicality can get us through some bad moments.
Unfortunately, higher heart rates, with concomitant rises in blood pressure, vasodilation, and related bodily functions, result in a reduction of bloodborne resources available to our prefrontal cortex and other important brain areas; and in any complex situation involving other human beings, this can present a significant problem.
Even between the heart rates of 115 and 135, optimal for the human "fight-or-flight" response, we begin to see problems. Our ability to engage in fine motor behaviors begins to diminish, and we start to see tendencies toward less precise thinking (e.g., Sharps, 2022).
As our heart rates climb beyond that point, into the 170s, we may start to see genuinely maladaptive behavior. People experiencing very high heart rates may experience partial paralysis. They may engage in excessively submissive behavior. They may even wet themselves, or defecate in whatever clothing they happen to be wearing.
These are not particularly useful behaviors under most circumstances, and perhaps especially not for law enforcement officers. Partial paralysis means you're not going to be very good at dealing with any oncoming threat. Submission in a law enforcement officer (or for that matter in a soldier in battle, an attorney in a trial, or an executive in a tense meeting) is also likely to prove singularly unhelpful; and urinating and defecating copiously in one's clothing is not exactly going to be at a social premium either.
Why do these things happen?
It is important to realize that human beings have a long evolutionary history; we are not only the products of the modern world, but of a bygone world as well in which very large predators had a significantly determinative effect on our futures.
In that world, these currently maladaptive behaviors may have been very helpful. Partial paralysis? 'Possums have been playing that trick for millions of years; most predators can't tolerate the bacterial smorgasbord of the recently dead, so an unmoving prey creature may be left untasted.
Submission? Symbolic submissive gestures are involved in the surrender behaviors of a number of mammals, including some primates. Submission at the right time can stave off maiming or even death, and may very well have done so in humans or human ancestors before we had the ingenuity to invent total war.
Loss of bladder and bowel control? Our predators, creatures like sabertooths and Dinofelis, literally the terrible cat, had olfactory senses dozens or hundreds of times better than our own. A sudden marination in our own special sauces, so to speak, may have moved a big cat from a predatory state of "RAARGH!" to a highly avoidant state of "EWWW," perhaps literally in a heartbeat.
But these extreme behaviors occur with very elevated heart rates. Does anybody ever really experience a heart rate in the 170s? My friend and colleague, physiologist Riccardo Fenici, provided the answer (Fenici & Brisinda, 2004).
Certain agencies of the Italian federal police are staffed by the best-conditioned law enforcement officers I have ever met. Fenici measured the normal heart rates of these young (male) officers and found that their average heart rate lay in the low 60s. Then he measured their heart rates again on the firing range. There was no physical threat; the only excitement might have derived from competition.
Yet the officers' heart rates jumped into the 160s, within a reasonable range of the partial paralysis and defecation potential of the 170s; one can imagine what these officers' heart rates would have been if the targets had been shooting back.
And these officers were all young and in great shape.
The ancient world is still with us, and it shapes our stress responses. Yet if we are aware of these factors, we can shape their influence to our advantage. We will see how this can happen, in more detail, in our next Forensic View.
Fenici, R., & Brisinda, D. (2004, October). Cardiac and Psycho‐Physiological Reaction During Police Action and Combat Shooting. Society for Police and Criminal Psychology, Rome, Italy.
Sharps, M.J. (2002). Processing Under Pressure: Stress, Memory, and Decision-Making in Law Enforcement (3rd ed.). Park City, Utah: Blue 360 Media.