Garmin 305 HRM

I have not been out running for about 6 months due to some personal issues. Over this time, I started smoking again and have now managed to kick the habit (I hope) and start running again.

 Because of this, I am eager to use my Heart Rate Monitor to see how my HR improves over time as I use this as a guide to my increasing fitness.

The first time I went out for a run, when looking back over my stats, I noticed that the HRM readings werevery strange. Basically, it would appear that it is only taking a reading at intervals. Rather than a nice graph that jumps about everywhere, this is very blocky, with me having the same reading for a period of time and the instantly dropping by about 30 bps. 

My initial thought was that there was a problem with the battery so I have now removed this and replaced it. Unfortunately this hasn't seemed to help.

When I went out for my last run, I was watching the read out a little more closely and it seemed to have a constant connection.

I tried to rescan the HRM but this didn't seem to help. I then removed it and readded it rescanning, but again, this made no difference.

Is there anything else I can try?

You can see what I mean from this run -
My Run

Many thanks,


  • looking at the data the drops in HR coincide with a drop in pace and a downhill section, which means you're easing off quite quickly. now I don't know if that is sufficient for the HR pickup to show strange effects but I would suggest you try a different route, at as constant a pace as you can (flat would obviously be best), and then see what the Garmin shows.

    the other issue that I know can effect HR readings is electrical interference - as an example my Polar HR will sometimes stop if I run across a level crossing where the trains use a track power rail. perhaps you're passing something at that spot that's producing similar interference such as a sub-station?? just a thought
  • I am running around a park that doesn't have anything nearby (that I am aware of) that would cause any interference - it certainly hasn't in the past.

    While the drop in HR does coincide with a drop in pace, there is no way that my HR was exactly 180 for about a minute and a half and then instantly dropped to 150, this would be a gradual process.

    Part of me is thinking that it may be the contacts, but I sweat enough to ensure that this shouldn't be the case. I will be trying some gel tonight to make sure, but I'm not convinced this is the issue...

    Last resort will be to do a hard reset on the watch, but I'd like to avoid this if necessarry!

  • try a different route as I suggested and see what data it records - if you're still seeing the same results then you can probably discount a contact issue. if you do see the same then I suggest either a hard reset despite you not wanting to, and/or getting Garmin to look at it as it would then appear to be a wrist unit issue
  • Thanks,

     I have a different route which has similar results. I'll try a hard reset tonight. At a push, I might be able to borrow a friends HRM and see if I can pair with that.

  • Fido2DogsFido2Dogs ✭✭✭

    Gob on the chest contacts (or stick them under the tap BEFORE you snap on the transmitter obviously).

    Also how old is the hrm belt? Mine was acting up (no, of course I hadn't kept it as clean as I should have!) and I replaced it with a Polar Wearlink+ strap for 10-15 quid. Better now.

  • I'd say the belt is about 18 months old. It still has plenty of eleacticity in it and I can still tighten it up a little before it becomes too loose.

    I've got some water based gel which I am going to try tonight after giving it a wash. If that fails, then the hard reset of the watch will be the next step (I am assuming that this will force me to re-pair the device)

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