Does elevating your heart rate during exercise have the same effect on you as a fight or flight response?

- asks Anh Nguyen from San Jose, California

An electrocardiogram, or EKG, which measures the electrical activity of the heart. [CREDIT: NIH]
By | Posted June 11, 2007
Posted in: Ever Wondered?, Life Science
Tags: , , ,

An off-duty police officer is playing basketball with his buddies. His heart rate is up and he’s sweating, but he can still see and move well enough to drive around his defender, run toward the basket and score. When he gets tired, he takes a quick breather and drinks some water.

The same officer is on duty later that night. He’s stopped a suspicious vehicle and is approaching the car from the passenger’s side when he sees the car’s occupant fumbling under his seat. The officer yells for him to freeze, bringing up his service pistol. The person in the car ignores him and comes up with a gun, brandishing the weapon. The officer’s heart is pounding as time almost seems to stop. He has tunnel vision – all he can see is the danger in front of him. He squeezes off several rounds, although later he can’t recall hearing his own gunshots.

The hypothetical officer’s heart rate is similar in both cases. But while heart rate during exercise might be similar to that in a high stress “fight or flight” situation, the two situations affect our bodies in very different ways.

Your heart rate is controlled through your nervous system, specifically by the sympathetic and parasympathetic pathways. Simply put, the sympathetic nervous system prepares your body for action, while the parasympathetic nervous system prepares you for rest. Medical experts often use the analogy of an accelerator and a brake, as the systems work together to keep your heart rate and other bodily functions under control.

During exercise, the sympathetic and parasympathetic nervous systems gradually change your heart rate through the release of hormones and other chemical messengers. As muscles demand more energy, the sympathetic nervous system increases heart rate, blood pressure and breathing. The body eventually works up to a target heart rate for exercise – for example, a healthy 25-year-old would have a range of 117 to 166 beats per minute (bpm). After exercise, or during a rest period, the parasympathetic nervous system gently applies the brakes and brings you back down to a resting heart rate.

Body changes during a fight or flight response, however, are anything but gradual. That’s because fight or flight is the body’s on-the-spot answer to high stress situations, such as those experienced by emergency responders or soldiers in combat. In these instances, the sympathetic nervous system readies the body for action with a massive dose of hormones, such as adrenaline, boosting heart rate within a few seconds to a level that would take minutes to reach during exercise.

Because of the huge hormonal boost during fight or flight, the body experiences other changes at various heart rate levels that would not happen during exercise. Experts consider a flight or fight heart rate of 115 to 140 beats per minute optimal for sustaining rapid, coherent thinking and quick reactions. But above 140 bpm, the sympathetic nervous system begins shutting down certain “unnecessary” bodily functions in order to focus on survival.

• At 145 bpm, you lose most of your ability to do complex motor skills or movements – remember how people in movies fumble to get a door open during critical moments?

• At 170 bpm, tunnel hearing and tunnel vision kick in, a response that allows your body to focus all its attention on the immediate danger at hand.

• Above 170 bpm, your thinking is reduced to the primitive fight or flight response. Running (or charging) is at its peak performance. The vast majority of people also tend to lose control of their bladder and bowels at this stage because even those functions consume resources that the body prefers to save for fighting or running.

People whose duties put them in high-stress situations often train themselves to manage high-intensity stress, so that the fight or flight response doesn’t completely hijack their actions. But if you’re just shooting some hoops with some friends, there’s no reason to stress.

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  1. This article is flawed. Where is this research data coming from to substantiate the claim of tunnel vision and bladder control loss at 170bpm? I’m 29 and I regularly climb mountains on my bike with a heart rate of 180-185 (for 20-30 mins at a time) and feel great. I do road riding and racing and a regular 4 hour 60 mile ride on Saturday mornings up 5,000 ft of mountain roads with an HR between 150 and 180 usually. I assure you, I don’t “lose control of my bladder” above 170 bpm nor do I have tunnel vision. Those are normal heart rates for me, with my maximum HR being about 198.

    Scott, July 10, 2007 at 3:37 am
  2. Dear Nguyen-Ahn,

    You wrote an excellent article (I see you used wikipedia to do some research re parasympathetic/sympathetis NS). In response to Scott’s criticisms, I offer the following clarifications:

    Dear Scott, please note that author clearly stated: “Because of the huge hormonal boost during fight or flight, the body experiences other changes at various heart rate levels that would not happen during exercise.”

    In other words, Scott, when you are in “flight or fight mode”, your body works/reacts differently than when you’re exercising; i.e. intestines do shutdown at those heart rates when in flight or fight mode because of the influence of massive amounts of epinephrine (i.e. adrenaline).

    BTW you must be fantastic shape to sustain 180-185bpms for 30 minutes. But be careful, you seem to be waaaaaay over the safe limits THRZ; max upper rate should be 160-170 bpm for you age. Unless you know something different that we all benefit from.

    Kumar, July 23, 2007 at 4:24 pm
  3. My apologies,

    I mean’t Jeremy Hsu not Nguyen-Ahn

    Dear Jeremy Hsu,

    You wrote an excellent article (I see you used wikipedia to do some research re parasympathetic/sympathetis NS). In response to Scott’s criticisms, I offer the following clarifications:

    Dear Scott, please note that author clearly stated: “Because of the huge hormonal boost during fight or flight, the body experiences other changes at various heart rate levels that would not happen during exercise.”

    In other words, Scott, when you are in “flight or fight mode”, your body works/reacts differently than when you’re exercising; i.e. intestines do shutdown at those heart rates when in flight or fight mode because of the influence of massive amounts of epinephrine (i.e. adrenaline).

    BTW you must be fantastic shape to sustain 180-185bpms for 30 minutes. But be careful, you seem to be waaaaaay over the safe limits THRZ; max upper rate should be 160-170 bpm for you age. Unless you know something different that we can all benefit from.

    Kumar, July 23, 2007 at 4:28 pm
  4. Hi I am doing some research and this seems highly relevant. I would like to cite you, but mine is a formal academic paper, so I would need to understand how these results were achieved.

    Do you have a fuller version – fascinating stuff.

    Kind Regards,
    Kate

    Kate, October 10, 2007 at 6:17 am
  5. I have read so many articles siting the maximum heart rate calculation. Surely with so many factors influencing it it cannot be that simple. I am a 50yr old 140lb woman and I work out on a crosstrainer and treadmill and spin – and maintain a heart rate of between 175 and 185 for the most part. Is it dangerous I feel great no dizzyness or nausea and I can bring it back down to 130 within 2mins – to finish my workout with weights..

    Deborah, December 19, 2007 at 10:27 am
  6. very interesting views presented here, I’ve often wondered if there were any dangers associated with exercising up to (and probably slightly beyond) one’s recommended max heart rate .. I often row sustaining a heart rate of 175 … sometimes reaching 190. my max heart rate is calculated at 185. anyone know of any potential problems here?

    Kay Sanya, January 3, 2008 at 10:22 am
  7. Hi, I am a 70 yr old healthy male. I work out daily and am 170 lbs and 5’8″. I find if I work out taking my heart rate to the 150 plus area I get a good workout. If I follow the rule and deduct 70 from 220 I should only go as high as 130. Is it dangerous to run higher than the calculated max?

    Peter Thomas, February 12, 2008 at 10:53 am
  8. How was a two minute rest period established to check ones resting heart rate after exercising?

    Is it true that ones resting heart rate should be taken directly after awaking from a night of sleep while still in bed?

    Joel, February 24, 2008 at 6:13 pm
  9. Through the years, I have known of the “inaccuracy” of the HRmax prediction formula most commonly referenced (HRmax = 220 – age [for males]). If nothing else, I am a prime example. While it has been a while since I used my HRM, my most recent recollection of data (probably about a year ago) was that my HRmax from a race was in excess of 200 bpm. Reasonably assuming the data was from within the last 2 years, my “predicted” HRmax should have been 180 (220-40 = 180). Often, in MTB, or more so in CX races, I will average in excess of 180 bpm.

    I cringe when I here people referencing the oft-quoted formula above. I did a quick Google search for “heart rate 220” and came up with what seems to be a relevant, short history of this formula written by Robergs and Landwehr from U of NM (http://faculty.css.edu/tboone2/asep/Robergs2.pdf). Briefly, their conclusions:

    1. There is no published research for the “equation”. The equation is a linear best fit of a relatively small data set.

    2. There is no acceptable method to estimate HRmax. Many have performed other experiments, from which they have made observations of HR and provided there own formula for HRmax. However, the formulae always have a large error of prediction.

    3. If interested in VO2max, using the “predicted” HRmax in estimating one’s VO2max can result in considerable errors (greater than the predicted HRmax!).

    Bottom line is we are all individuals, with different hearts (some could say based on my high HR that I have a small heart! ). We ride bikes. Our performance is not governed by what HR we ride at. HR capacity can be a contributor to one’s performance, but not the “rule”. There are many other factors that affect your “performance”. Basically, how long can you apply “a” force to the pedals/cranks. Then there are skills, efficiency aerodynamics, etc., etc., etc. Volumes could be written (and have been!) on these topics.

    So, use the “classic” HRmax formula with caution (or not at all ).

    Blaine, April 8, 2008 at 7:38 pm
  10. Internet amateurs at their worst. Except for the cyclist evrybody else is clutching at straws. This is not science but blundering around in the dark ages. Wikipedia is certainly no source for accurate information. What a waste of time.

    James, May 8, 2008 at 7:57 am
  11. hi im kayla and im doing an experiment for my biology class. i have a question……what types of energy drinks effects you the most ? monster or red bull

    kayla, May 21, 2008 at 10:35 am
  12. I am a 17 yr 8 month girl distance runner. I train year round and run between 45-50 miles per week in the summer. I run about 40 miles per week during racing season and alternate hard runs (tempo, intervals) with easy run/ recovery days. During my hard run days, like today, I have noticed that my heart rate will increase to around 180-183. I was running 6 x 1000 m at race pace. After the first two 1000’s, my heart rate was around 182 bpm at the end of each 1000. During the next four 1000’s, which I ran just a few seconds slower, my heart rate actually dropped in #3 & 4 to around 178 at the end. And during my last two, my heart rate did not get over 176, but I was totally exhausted and my perceived exertion was 100%. I don’t understand why my heart rate wouldn’t continue to rise as my effort increases and I get progressively more tired.
    thoughts?

    R Jarrard, September 27, 2008 at 2:43 pm
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    jessica twinley, October 21, 2008 at 6:49 pm
  17. I am 46 and while riding a bike 2-3 times a week my HR averages 174 for a 1 hour run (which tires me but doesn’t kill me). I am not a regular exerciser. 10 years ago, I got it up to 208 during a stress test and the cardiologist said I just needed to exercise more regularly. Had another ST and it was 196 a year ago and again doctor said nothing wrong with EKG or anything else, just higher than NORMAL people. Please ‘splain Lucy!

    Long Don, November 6, 2008 at 2:33 am
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  20. I’ve been working out for years (age 21), and have recently taken a few months off to recover from an injury. when i returned to the gym with my buddy, we continued at our regular rate, and after some fairly intense cardio mixed with push-ups, i felt progressively dizzy and experienced tunnel-vision with a loss of balance. i didn’t check my heart-rate after the workout, so i can’t be sure if it was simply being too far over my limit, but it certainly has never happened before. i went and sat down, putting a cold wet cloth on the back of my neck (thanks to a concerned gym-goer) and soon cooled off enough to continue with weights. the sudden worsening of what i was feeling may have been contributed to by my feeling that i may have pushed my heart too far and possibly put my life in danger, but i’m curious to know if this is fight-or-flight, overexertion or a mix of both?

    (for the record, i start basic training for the military soon, so i’ve been trying to get as much cardio as i can)

    Pete, March 16, 2010 at 6:25 am
  21. I’m 46 with a MHR of about 190. I cycle a lot and am usually between 165 – 185 BPM. The 220 formula just isnt accurate. If I stuck in the ranges it says I wouldnt get anywhere on my bike or be able to keep up with my buddies.

    Arne, October 2, 2011 at 12:54 am
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