Consistent issue with HR spiking after approx 7 to 10 minutes on 935

My very fit and competitive 12-year old runner experiences a consistent issue where her Garmin 935's HR data show a dramatic bump up at around 7 to 10 minutes into what is an otherwise easy (5/10 effort) long run, and then stays high. It does not correspond to her perceived effort at all. Any ideas? This is happening both when worn by itself as well as when using a chest strap.

At the same time, the Performance data doesn't kick in until right after this big bump. Is that by design? 

  • I'm convinced that its the HR sensor being tricked by arm movements/cadence. I've got several runs where my heart rate will jump to a value suspiciously similar to my cadence at the time, and then either self correct or continue to the end of the run. Tightening the strap seems to help - stopping the watch moving in my wrist. It's is annoying because it has impacted my reported VO2 max - because the watch has recorded a HR 170-180 when it was actually 130-140 for an easy run.

  • Happened here at 2.5km in - I did increase pace but no way was my HR north of 160. You can see it dropped back at about 4k.

  • Super interesting -  thank you for sharing this. I thought at first it was to do with the wristband/watch itself being loose as well. This is happening both when she's just using the watch and when she is wearing the chest strap. It's just so bizarre that there is always this noticeable bump... And her HR at >200 when it's not a tempo run and she self-reports an effort of less than 6/10. 

    Do you have a perspective on this "performance condition" graph? That's the other odd thing that kind of corresponds to the HR bump, but I'm not sure how it's supposed to work (does the performance condition calculation always only 'kick in' about 10 minutes in?)

  • Well, at first I thought it's due to reading of WHR. But when I read about it happens with chest strap too I was a bit concerned. What's her real heart rate at these situations measured at carotid? Does it drop when she stops? Maybe check with a cardiologist! Just because nothing serious is know doesn't mean it exists.

    Concerning performance data: this is normal. It needs a certain HR level to become active. You'll find something more in detail here in forum and/or on Forstbeat web site.

  • I just discovered this forum.  I have experienced similar problems with HR ramping up around the time I get warmed up.  Sometimes it goes really high and stays that way even though I'm trundling along at 2-4RPE.  It's annoying as VO2 max gets busted down and I'm told to take several days off training.  I have wondered if something like light, sweat, strap tightness or arm movement affected this but have not found any obvious reason or reliable method to seemingly correct this.  Depending on length of run I sometimes see HR drop down to what I would expect a way into the run.  has anyone heard from Garmin on this?

  • What you describe matches our observations... no real breakthrough insight so far. 

  • Thanks for commenting and also confirming regarding the performance data part. 

  • Interim update here: 

    I'm closer to figuring out what's going on. For all those cases of the heart rate suddenly spiking and saying up (see my original screenshots with the green circles) I'm now also convinced this is due to the watch getting tricked to pick up the cadence. I even found this phenomenon described on an official Garmin webpage. 

    Now I'm still investigating why this is also happening when she wears the chest strap (possibly the watch is still picking up HR from wrist band, even though it's connected and is getting running dynamics from the chest strap). But I'm encouraged....

  • Have you tried checking heart rate with a finger and stopwatch to validate whether the reading is correct?

  • Yeah, so we just did that this weekend during a track interval workout. Garmin said 185 HR and manual pulse check had her closer to 140... This was very encouraging and consistent with her self-reported PE, her ability to speak in full sentences without difficulty when the Garmin has her at 95% ... going to keep investigating. Would sure love to use the watch for real to monitor HR but this hasn't been helpful :(