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310xt HR spikes/errors at start of bike

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  • 310xt HR spikes/errors at start of bike

    I've been having an issue at the start of every bike with my 310XT (but not run or other sports). As I start, my heart rate reads normal, but as soon as I speed up the HR goes crazy, jumping up to between 180 and 230. It seems to be directly related to my speed and is clearly NOT my actual HR (I highly doubt i'm hitting over 200 bpms 2 min after starting a ride while coasting down a hill). If I slow down the HR lowers, but generally not below 180 or so. Eventually, I pull the strap off my chest and adjust a lot, stop, and adjust some more, and then magically, the HR jumps back down to an actual reading (I can't find any rhyme or reason to when/why it corrects itself).

    A couple examples:

    It has not happened every ride, but maybe 3 out of 4. Anyone have similar issues or a fix? I always wet the electrodes and do the same procedure for putting it on as other sports (e.g. running) and have never had a problem like this outside of biking. I have the Speed/Cadence sensor for my bike if that matters.

  • #2
    Do you wear a loose synthetic shirt? If so, the flapping of the shirt could be creating static electricity that confuses the HRM. Try using a cotton shirt or a tighter shirt and see if that helps. You could also try rubbing your shirt down with a fabric softener sheet before riding.



    • #3
      I wear skin tight cycling/triathlon jerseys while riding. Today it was a little cool and I wore an Under Armour all weather tight shirt under the jersey. THis was the data:

      As you can see, when I stop, the HR stops freaking out. As I go faster, the HR goes faster, when I slow down, the HR slows down (independent of what my real HR is). It seems obvious it has nothing to do with the jersey material. I've worn this same shirt while running, and never had this issue. Due to the apparent correlation to speed, I think there must be interference or some signals being crossed with the cadence/speed sensor.


      • #4
        It looks to me like the first 20 minutes was bad and after that the HR was okay, even though you were going faster than you were in the previous 20 minutes. Is a heart rate of 157 reasonable for you, when you're going about 20 mph? It's a very individual thing and so only you know whether your exertion level was there or not, but based on the relative smoothness of the HR trace after about the 20 minute mark, it looks fairly legit to me.

        The heart rate monitor and the GSC-10 don't interfere with each other in a way that's visible at the display or in the datalogs. A problem with the 705 could exist that caused data from one to corrupt the other but I would be surprised to see only one report of that kind of issue at this point.


        • #5
          As I said, it only happens at the start of rides, and then magically corrects itself. The length of time it happens is variable. After 20 min, yes it was fine in that one case. Thats still 20 mins of this being a pain in my butt and it not giving me data I need to do my workout (which I need the HR to do).

          It also happened again today:


          • #6
            This may be a obvious suggestion, but there isnt by any chance overhead electrical wires in the area you commence your ride from?

            I have the 310xt (no speed/cadence sensor fitted) and on one of my favourite climbs there are some big-as5 overheads that sent my HR spiking (200+) as my speed increased downhill. I havent bothered to look at the file more closely but did notice it in realtime and has also occured on the same ride when I have worn Polar devices.

            Just a suggestion.


            • #7
              If it's only happening at the begining, this sounds a lot like an issue with not having enough moisture to get a good connection.

              1) Give it a good ole lick and see if that solves it (the two sensor pieces on the strap).

              2) Pick up some HRM gel from your local running store, it's like $5 and lasts forever

              I see this on cool days as fall and winter sets in, and my sweating doesn't start for a while. This would only happen for the first 5-15 minutes until there's enough moisture.
              Tri Blog:


              • #8
                I've had exactly the same problem. I've a feeling it has onlyhappened since the firmware upgrade. Any news on a fix or solution yet?


                • #9
                  Agree on it only happening since the firmware update. I don't think its moisture, or lack there-of, since it only happens on the bike, I wet the electrodes already, and it only happens at high speeds (the HR is normal when I stop).


                  • #10
                    I got the premium HR strap last week and up until tonight have been happy with results.

                    Today I set an alarm for hitting Zone 3 (150) and all was well until I was hill climbing and was getting all manner of dumb HR readouts that were 30-40 bpm higher than what I was actually generating. It seemed that once the alarm had been triggered no matter what I did the HR flicked up and down passed the trigger point setting the alarm off every 5 seconds.

                    I ran the exact same route two nights running (they are visible on Connect) at the same broad slow pace, last night no alarm, tonight with an alarm. Madness, came close to throwing the watch into a field.

                    Could the alarm setting be the problem?


                    • #11
                      Make sure the strap is on tight. For some reason today I was having issues where I have never had them before. My HR shot up to 200+ and remained there for about 15 minutes until I stopped and adjusted everything. The alarms can certainly get annoying... I even thought of turning the 310 off since I was also riding with my trusty 705.
                      - Steve

                      my GC digest


                      • #12
                        It took me a few adjustments of the soft strap before I was satisfied with it. But once adjusted properly, I really like it. I did have to make it a bit smaller just the other day. I think the elastic might have stretched just enough to require an adjustment.



                        • #13
                          Heart Rate jumps crazy above 170 BPM

                          I've been having some of the same issues when running. I only use my 310 for running. I've been wearing the same types of shirts it seems like forever.

                          I used to run with a 305 which I LOVED. I was lost on a business trip so I upgraded to the 310. I'm been running with it for 6 months now and whenever I get to about 165 or 170 bpm the heart rate really starts to spike. It jumps to 190 then 225 and sometimes higher. When I slow down and time my heart myself the HRM is accurate anytime below 165 bpm but there isn't a chance that my heart rate is 225 (in the second mile of my run).

                          Some friends have suggested I update the firmware (which I've never done). I wet the pads and deep into my run the HRM is still off above 166 bmp.

                          Let me know what I should do - The only thing I'm thinking is to get a 305 again.


                          • #14
                            I have had several friends with pretty much the same problem, the problem almost completely disappears if you upgrade the firmware.
                            PB's: 1500m = 4:33.7, 3000m = 9:43, 5000m = 16:39, 10Mile = 59:39, HM = 1:22:22