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(Sympathetic Nervous System Arousal, aka Fear -> Fight or Flight)
Human Factors!!!

Heart Rate (beats/min) Cognitive
220 ? bpm <Tilt> <Tilt> <Tilt> <Tilt>
>175 bpm
  • Forebrain shuts down

  • Confusion

  • Loss of memory

  • False memory (seeing something that's not there)

  • Autopilot

  • Scared speechless

  • Behavior contagion (one cop shoots, they all shoot)

  • Preservation (repeated behavior even if it doesn't work, hauling those tools, hose; may stem from survival, for example, continuing to hit the lion with a rock)

175 bpm someplace around 175 maxes out
  • Very reduced cognitive processing
  • Training takes over
  • Extreme vasoconstriction- and return blood flow is plugged; body reserves blood for critical organs needed for survival
  • Loss of peripheral vision (tunnel vision)
  • Loss of depth perception
  • Loss of near vision
  • Auditory exclusion
  • Reduced bleeding from wounds



**Peak performance relating to survival if you are not frozen (an example is tri-athlete running from the lion)**

  • Irrational fight or flight
  • Gross motor responses are at highest level (eg, charging, running)
  • Strength at highest level (lifting, pushing)
  • Voiding of bladder & bowels
  • Freezing
  • Submissive behavior
145 bpm   145+
  • Vasoconstriction of larger blood vessels
  • Complex motor skills degrade (deploying your fire shelter? dialing 911)
maybe 145 bpm
someplace between 115-145
  • Cognitive reaction time is optimal
  **Peak performance relating to complex motor skills - "in the zone": basketball player making the free throw)** 115-135
  • Complex motor skills are optimal
  • Visual perception is acute
115 bpm   115
  • Vasoconstriction of peripheral blood vessels (for example, those in  your hands)
  • Cold clammy hands
  • Fine motor control degrades: fumble fingers (threading a needle, writing, screwing a small bolt on a nut, putting a widget in a tight little hole)


60-85 bpm     **Normal or resting heart rate; body in homeostasis**  

Table linked from theysaid discussion in 2004
Mellie's description of origins from theysaid 2/15/08:

Under high stress conditions such as fear, the entire Sympathetic Nervous System (SNS) is activated, producing a “fight or flight” response: this is an immediate, widespread physiological arousal response. The fear-related stress hormone -- epinephrine (commonly called adrenalin) -- causes physical, cognitive, behavioral, performance and heart rate changes. After the danger passes, nor-epinephrine returns the body to a balance, but because the body has had such a profound change in response to the adrenalin, a backlash often follows.

Many of you probably know this parasympathetic crash. You've probably felt it following prolonged stress arousal during an intense fire season. The parasympathetic system symptoms include profound exhaustion, even nausea, vomiting, dizziness, and depressed heart rate and blood pressure. Nerd on the Fireline once wrote about this on Familysaid- about grumpy firefighters after the season is over. She had a good graphic too... (Safety Expert Dr. Gordon Graham -- the "Predictable is Preventable" guy -- spoke on this topic several years ago at the R5 Chiefs meeting.)

The numbers on the table are ballpark heart rate numbers related to the SNS stress response. There are potentially large individual differences in heart rate relating to physiological arousal and other cognitive, physical, performance and behavioral responses to the stress hormone. Let me be clear, I'm not talking about increased heart rate due to exercise. That's different. Lots of athletes perform optimally when their heart rates are elevated; with conditioning and practice they can perform well physically and cognitively and their stress hormones may not be greatly elevated. However, if they become stressed (fear or performance fear, demands exceed their ability to cope, etc.) their heart rate increases and their performance falls off. The inverted u-shaped arousal :: performance curve was described by Yerkes and Dodson in a very old publication in the early 1900s, if I recall correctly. (OK, here's a description: Yerkes-Dodson Law.)

Also note that people can have high heart rate unrelated to SNS stress. Older people often have higher resting heart rates and may be more reactive to stress and slower to recover than younger people who are better conditioned.

The topic of stress and fight/flight grabbed my attention in a deep way in about 1990 in conjunction with Carnegie Mellon University/ U Pittsburgh post doc program on stress. A bunch of us with different areas of interest (some were involved in cardiovascular stress research at Pitt, dang, can't remember the name of great stress and cardio researcher) were brainstorming correlations between fear-induced stress, different kinds of functioning -- both macro and micro -- and heart rate. A bit later I read a lot of Bob Sapolski's work (Why Zebras Don't Get Ulcers; Stanford University) and Bruce McEwen (The Hostage Brain; Rockefeller University) who looked at the effects of hormones on brain function/fight or flight/ and also the HPA stress axis. They were part of a MacArthur Foundation Working Group on Stress and Health that I had the good fortune to interact with.

The MILITARY ended up being where the rubber hit the road for this kind of research, because they had lots of [willing?? (grin)] subjects and could see some real benefits to studying the psychology of combat [like staying alive and surviving re-entry into the non-war world]. That's where some of the cutoff numbers coalesced: with Dr. Dave Grossman's and Bruce Siddle's research with the military in the mid-90s. Siddle wrote Sharpening the Warrior's Edge. Some really good books by Lt Col Grossman are On Killing and On Combat, the Psychology and Physiology of Deadly Conflict in War and in Peace (this last book with Loren Christensen). (On Killing was nominated for a Pulitzer. Grossman did a lot of lecturing to Police and Military, taught at West point; I think his lecture I heard, the Bulletproof Mind, turned into On Combat. He's a very fine lecturer, dynamic like Gordon Graham.) It's fascinating stuff, Dave lays out a stress related psychomotor physiological aspect of "human factors" that influences decision making and performance.

(Whenever soldiers, police or firefighters are criminally charged, I always pray for a person like Dave Grossman to take their side and put their actions into perspective. It's not black and white. People simply do not know how altered human function, physiology, cognitive performance, reasoning etc are when adrenalin kicks in.)

Bruce, I don't know if Siddle was first to publish or if Grossman was. They may have done the research together. I don't know which journals their original work is published in, maybe it was only available to the military, but their work is important and profound. Good luck with sorting out the table. I wrote it as kind of an off the cuff response to some question on theysaid. Maybe read On Combat first.

Wow, look what I just found: Grossman has a website: Killology Research Group His publications are listed there.


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