Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Medical How to calculate dangerous heart rates and blood pressures.

  1. Oct 14, 2011 #1
    In AP Bio we've been learning about blood pressure and pulse, and how to calculate pulse ranges of exercise. But, I was wondering, if we can calculate that, can we also calculate the maximum safe heart rate to within a reasonable range? Also, is it possible to calculate safe blood pressure ranges?

    For the sake of clarity, let safe be defined as anything not unsafe and unsafe to be anything that is of immediate danger.
  2. jcsd
  3. Oct 15, 2011 #2


    User Avatar

    Staff: Mentor

  4. Oct 16, 2011 #3
    I thought he was referring to safe heart rates during exercise. Curious, I googled it, but couldn't find a consensus. Some sites basically claim that if you go over 95% of your "maximum heart rate" (usually calculated 220bbm - age, sometimes 224 - age for women, some sites multiply age by 0.8 or 0.9) you are at severe risk of heart attack. I found one site that claimed flat out, if you go over 220 - age, you will die (which is very clearly wrong, as I have personally exercised with heart rates higher than this formula predicts many times)

    Other sites claim that it is virtually impossible to damage an (otherwise healthy) heart from exercise. Some claim by the virtue that your muscles will stop working, due to lactic acid build up, long before the heart could be damaged. Others, that you will pass out from lack of oxygen to the brain before the heart can be damaged.

    Most (but by no means all) of the more reputable looking sites seem to claim that you shouldn't be concerned about a high heart rate during exercise, no matter how high it gets. Instead they suggest watching out for other problems:
    1. Chest pain
    2. Left arm/shoulder pain
    3. Sudden drop in heart rate
    4. Sudden rise in heart rate that doesn't accompany a sudden increase in exercise intensity
    5. Heart rate doesn't return to near resting rate within ten minutes of ending exercise
    Not all of them included all of these items, but the top 3 were pretty consistent.

    I should add that a few of the reputable looking sites (university health science type sites) fell into the "nothing over 220 - age is safe" category.

    Many sites suggest that the "maximum heart rate" isn't the maximum "safe" heart rate, as is commonly assumed, but rather simply the maximum possible, and that there is significant variation within populations, even for a given age. Some suggest that this maximum can be increased through training. Others suggest that this maximum will naturally decrease as your heart becomes stronger (able to pump more blood per stroke => less strokes required).

    I guess this was a really long winded way of saying "I don't know, and I'm not sure anyone does".
  5. Oct 16, 2011 #4
    No, I found that on Wikipedia. I'm pretty sure it's referring to blood pressures that are dangerous in the long term. Which implies they are relatively safe in the short term (otherwise they wouldn't be listed on a long term chart).

    I think bpm is better understood than blood pressure. Here's the Wolfram Alpha page on me: http://www.wolframalpha.com/input/?i=heart+rate,+17yo,+resting+hr=80. I'm guessing that 173 is probably my maximum safe heart rate. But, the only data I can find on blood pressure is long term data.
  6. Oct 16, 2011 #5
    As I mentioned in my previous post: It's not clear that there is any such thing as a "maximum safe heart rate".

    I haven't taken the time to peruse any of the original research on the subject. If anyone does, or finds a good summary of it, let me know.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook