How tight to make HRM work?

Discussion in 'Apple Watch' started by tl01, May 13, 2015.

  1. tl01 macrumors 65816

    Joined:
    Jun 20, 2010
    #1
    How tight does your watch have to be to make the HRM work? I have to have it almost uncomfortably tight for it to be accurate. I have a 42mm using the s/m band and I do not have any tattoos.
     
  2. GrindedDown macrumors 6502a

    Joined:
    Jun 4, 2009
    Location:
    Las Vegas
    #2
    I don't have my watch yet, but I would imagine there are a number of factors that can change how tight it needs to be for it to accurately read your heart rate. For someone, like me I am imagining it will be incredibly easy at just about any tightness because I have very veiny arms. Also, the amount of fluids you have in your system may affect this as well. While it would typically affect bioimpedance sensors wayyyy more, it can affect an affect on the size of your veins and how close to the surface they are of your skin.

    Is it that way for you on both of your wrists?
     
  3. dabigkahuna Suspended

    dabigkahuna

    Joined:
    Aug 3, 2010
    Location:
    Oahu
    #3
    I've only had it a bit more than a day but this is what I found:

    First I did some comparisons with just normal stuff (no activity app running). I also checked with an app on my phone which seems pretty accurate since it has matched the number I get on my blood pressure meter. Each time I checked, it was within 1 bpm.

    Next, I tried it during an exercise activity (cycling for almost 2 hours). I had nothing to compare with so I was mostly looking for numbers that were logical and consistent. That is, if I felt like I was making pretty much the same effort over time (or resumed to some effort after a bigger push), I would expect the numbers to not jump all over. This seemed to work out pretty good almost the whole time.

    If I was pushing up a hill, I would get 137-148 (or 162 on one big effort). When cruising steady on fairly flat ground, I would be between 122-127. These numbers seemed reasonable to me compared to my usual resting rate in the low to mid 50s.

    Of course, since, as I understand it, the watch only checks your heart rate once each minute automatically when exercising, it isn't going to react instantly like a dedicated device would.

    I only ran into one brief problem. Climbing up my last hill, I was pushing enough to get it to 144 or so and then I eased up for about 20 seconds and then checked it. It said 76. Not possible, especially since I was still going up hill! It soon got back to 131 though. No idea what the problem was, but it was the only one I experienced.

    Now, as for how tight, that's hard to describe. I can put it on so the pin is in the 3rd tightest position (smaller band size) and it will be pretty darn tight, but wearable. But I'm using the next hole and so far that seems fine. It worked on the next loosest too, but might not if I was doing something active.

    I have sometimes noticed numbers when I go back to check that I wonder about. For example, just now I went to the HR glance and it said that 2 minutes ago it was 85. That surprised me since I've just been sitting here for awhile. But as it calculated a new figure, it said 58 which is likely correct. I've seen this a few times - the questionable number is always one calculated earlier but the new calculation is always lower and more consistent with what I expect.
     
  4. GrindedDown macrumors 6502a

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    Jun 4, 2009
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    Las Vegas
    #4
    I wonder if it is showing the JUST the heart rate that it read from the last reading or if it is showing you a running average of your heart rate for the day and the last time it was updated was 10 minutes ago. That may happen and could make sense as that sort of data is one of the pieces to tell you your total resting calorie expenditure. I could also be ridiculously wrong (please get here SGS so I can find out on my own!!).

    If you keep having that problem where the last taken heart rate is always higher, check what it is right now, mark down the number or just remember it, then check back in 10-15 minutes and check to see if it displays that same number.
     
  5. dabigkahuna Suspended

    dabigkahuna

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    Aug 3, 2010
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    #5
    I've looked back like that because sometimes I've checked it (after noting the most recent reading before it calculates a new one) and then I'll go back to the time before returning to the HR glance again and it will show the one I previously did. So it doesn't seem to be a running average at all.

    I'll try to keep track better, especially when just sitting or lying down for an extended period so my HR should never jump up and see if I still get these higher numbers sometimes.
     
  6. GrindedDown macrumors 6502a

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    Jun 4, 2009
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    Las Vegas
    #6
    Yeah that is pretty interesting behavior to be sure. Not to hijack the thread, but if you do do that, be sure to check back and post your results so these inconsistencies can be better tracked. Other people may find this info and issues with the HRM to be interesting, I know I do.
     
  7. roblognick macrumors member

    Joined:
    Nov 19, 2014
    #7
    I've noticed that my watch needs to be quite tight for it to measure my HR accurately. I used the small sports bands on the third hole. Sometimes, on warm days or during workouts the third hole can become a little too tight so I move it to the fourth hole but this stops the HRM from reading accurately.
     
  8. tivoboy macrumors 68030

    Joined:
    May 15, 2005
    #8
    If you are doing a workout and tracking that, it should be checking your HR every six 6 seconds, ten times a minute, not every minute.

    when not doing a workout and tracking, the activity app is going a measurement every 10 minutes only.
     
  9. dabigkahuna Suspended

    dabigkahuna

    Joined:
    Aug 3, 2010
    Location:
    Oahu
    #9
    Do you know where you got that info? I remember looking for a breakdown on that in various reviews and only found the once a minute reference. Love to get something more official.

    ----------

    Checked it before getting up this morning (I wear it in bead) and it said "8 minutes ago" that it was 105 ! And then did it's new calculation and it was 50. Strange how a new calculation always seems to make sense and the "old" one sometimes is of significantly - or a LOT in this case. And so far always too high.

    We need other people checking this to see if there is a pattern or just my watch.
     
  10. tivoboy macrumors 68030

    Joined:
    May 15, 2005
    #10
    somewhere



    somewhere on the apple site I think the manual referenced the data.. as well, I can tell you in the health app when tracking a workout, I have 10-11 readings per minute
     
  11. dabigkahuna Suspended

    dabigkahuna

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    #11
    I'll have to look again. I really hope that is correct!
     
  12. xraydoc macrumors demi-god

    xraydoc

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    Oct 9, 2005
    Location:
    192.168.1.1
    #12
    I only need my watch to be comfortable for the HRM to be accurate. There's some play in the band -- not freely spinning but leaves no indentations on my wrist -- and it works quite fine.
     
  13. Sphyrna macrumors regular

    Joined:
    Jul 9, 2008
    #13
    I've found when doing a workout I have to wear my watch higher up on my arm for it to be accurate. If I wear it where I normally wear the watch then I get odd readings. I'll be getting 140 bpm from my chest strap and my watch will display 65 bpm. After reading on here the suggestion to wear it higher I tried it and it has been very accurate compared to my chest strap.
     
  14. dabigkahuna Suspended

    dabigkahuna

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    Aug 3, 2010
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    Oahu
    #14
    Found a user guide from Apple online, but can't find this specific info yet.
     
  15. dabigkahuna Suspended

    dabigkahuna

    Joined:
    Aug 3, 2010
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    Oahu
    #15
    Ah, looking at the health app on the iphone I found a listing of all my HR checks. When exercising using the activity app, I commonly found 12 entries for one minute periods (sometimes less - like 7 - not sure why the difference). Since it is just saying when it as added to the health app, it doesn't get more precise than the minute, but if it did it 12 times, that would imply that it is checking every 5 seconds and I'm really happy to have it do it that often.
     
  16. dabigkahuna Suspended

    dabigkahuna

    Joined:
    Aug 3, 2010
    Location:
    Oahu
    #16
    I ran a test using Activity (selected "other" for my exercise, though that may not matter - I wasn't actually exercising!).

    I think I set a calorie goal of 250. I got a tap at the halfway point and when done (took 75 minutes). I as sitting most of the time - I should have made a note of when I did get up. Maybe next time.

    After ending the activity, I went to the iphone health app to see what HR numbers I got. I didn't check how many updates there were for every minute, but all the ones I did check came out to be 12.

    But I also wanted to look for any surprising numbers. For a large section of time, it was between 48-55, but then I started getting some higher. That may have been when I was going into the kitchen or something. Besides the 60's and 70's, I saw some a bit over 100. But the weirdest one was a low of 43 right next to a 77 (the highest during this test was 78 and 43 was the lowest). Remember, these readings are about 5 seconds apart! Most of the numbers around those two were 53-56.
     

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