Today i rode a hard 18 miles at 17.6 mph and not long after i started my Garmin was giving a heart rate read out of 230 bpm.
I am 55 years old so i must get in the Guiness World records because that has got to be impossable
I wear my security pass around my neck on my commute. For some reason, if it is front of the Garmin heart rate strap, it affects the reading. So, I now just tuck it into my bibs and the reading is fine.
I hit 230bpm on some rides, but I discovered when I checked the location where it happens, that it always coincides with passing a telephone mast a few hundred yards from my home. As I approach it, you can see the HR increase, max out at 230 as I pass, and then it drops back down again as I leave it behind.
Its a right pain in the arse as it screws up all the averages, so it then means I have to do an estimate from past rides and edit the file.