Workout Heart Rate Accuracy?

Discussion in 'Apple Watch' started by syan48306, Oct 5, 2017.

  1. syan48306 macrumors 6502a


    Apr 15, 2010
    So I got myself a series 3 SS model and I've been trying out the workout function but seem to be getting strange heart rate monitoring results. During a workout I would look down at the watch and a couple times during the workout the heart rate monitor would be grayed out as if it completely lost detection of the HR. It would drop down to a resting ish heart rate of 64. Then it would eventually come back. I thought it might be because I swiped over to change to another song but that just doesn't feel right.

    Has anyone else experienced something like this?

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  2. Mlrollin91 macrumors G5


    Nov 20, 2008
    Ventura County
  3. ripper998 macrumors regular

    Jun 19, 2010
    I dont have that issue with my series 2. Before I get going though on the elliptical, I tighten my strap
  4. deeddawg macrumors 604

    Jun 14, 2010
    Also note that in general, wrist-worn optical HR readers can have difficulty in any activities where the wrist is tensed up a lot.
  5. loplop macrumors newbie

    Sep 26, 2017
    I’ve been using an AW for cycling, running, and tennis since getting my S0. For me, I need to have just the right balance between tightness and looseness to get good readings. Just a bit too tight and the readings stop, too loose and the same. I’ve grown accustomed to about the right tightness, although I’m struggling a little more with my Milanese band (received with my new S3) as its so adjustable. Also, the sport bands work better for me with respect with HR tracking; I surmise they allow a little expansion in my wrist without getting too tight, as the woven bands tend to provide less accurate readings during latter parts of long workouts.

    As far as accuracy, running (or walking) shows the least variability for me, followed by cycling which usually takes longer to register at the beginning and has a few dropouts throughout. HR tracking during tennis is very poor for me, although I’m not sure why as I don’t wear it on my dominant/racquet hand, and I don’t have a two-handed backhand...

  6. MJ22 macrumors regular

    Oct 3, 2017
    I have a fitbit with HR (still waiting for my AW3 to ship!!) and the HR sometimes doesn’t read when I’m very sweaty and moving around a lot. It goes in and out pretty well and settles quickly into what seems like an accurate zone.

    Remember these are just devices and aren’t perfect. If you’re overall getting decent readings I would not think a thing of it. I’ve read that the AW has one of the more accurate HR monitors out there.
  7. syan48306 thread starter macrumors 6502a


    Apr 15, 2010
    That's interesting because I'm using the Milanese band and I never thought it might be the issue. It's so adjustable and it stays tight, I didn't think would be the issue.

    I'll pay attention to the tightness next time.
  8. loplop macrumors newbie

    Sep 26, 2017
    Try various tightness levels over a couple handfuls of workouts. It took me about a month to really get a feel for what worked for me (with S0 on WatchOS 1, it's definitely better now on WatchOS 4 so you might get in the zone more quickly).

    I tend to look at the AW HR monitoring as an averaged set of data points--not perfect, but representative of the activity. I do have a Scosche Rhythm+ for times I want better accuracy, but I mostly used it to get comfortable with the AW's performance. I'm not a world-class athlete trying to peak for a particular race, and I have a large enough base of fitness to know about where I should be and use the AW measurements to guide me where I feel corrections in training are necessary. It's definitely good enough for that.
  9. risenphoenixkai macrumors regular

    Oct 14, 2008
    It has very little to do with how tight/loose you wear the Watch (unless it's so loose that it's flopping around and/or losing contact with your wrist completely).

    What you describe is occurring primarily because optically-based heart rate monitors (like what the Watch uses) are highly susceptible to having their readings muddled by any kind of restricted blood flow to the extremities (your hands, in this case). This occurs in many different kinds of workouts, but I've found it most blatantly apparent when lifting weights.

    Basically any kind of exercise that constricts or constrains blood flow to your arms is going to result in low heart rate readings, or no readings at all. This includes things like lifting weights, tennis, and, if you're strangling the hell out of the grips, riding a bicycle.

    If you want truly accurate heart rate readings during these types of exercise, the solution is simple: get a chest strap heart rate monitor and pair it to the Watch via Bluetooth.
  10. loplop macrumors newbie

    Sep 26, 2017
    Yes, of course. Generally, what you say is true (although not applicable in the examples I have). And it follows that tightening the strap can do exactly what tightening your grip can do ;)

    Try it for yourself. If you’re as lean as I am, strap tightness can easily restrict blood flow. Results will vary for each individual.

    Something else I thought of for the OP: for me, HR monitors require a little bit of moisture on my skin to work well. Sweat works, but that takes 5-10 mins into a workout to come into play. Saliva can suffice.
  11. syan48306 thread starter macrumors 6502a


    Apr 15, 2010

    Clearly this isn't working haha.

    This is just a "indoor walking" exercise so it really shouldn't be that hard for the watch to keep track of my heart rate. I did notice that it seemed to go dark when I swung my arms while walking. The watch is snug on a Milanese loop so it's not really moving. Perhaps I'll try wearing it further up on my arm rather than on my wrist to give it a flatter part of my arm to read.

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10 October 5, 2017