Heart rate not responding to intensity

Get a new heartrate strap. I was having very similar issues with a Wahoo Tickr; the data was really odd and kind of freaked me out. I got a new heart rate monitor and all of a sudden my data was looking like my expectations.

Not saying that's definitely your issue, but for $50(ish) well worth exploring.

Manually check heart rate on neck or wrist and count and see if if matches your monitor reading.

High heart rate at the beginning of a workout is usually the strap is not wet enough to get a good reading.

Suppressed max heart rate can be a sign of being overly tired. If you don’t think that is the case the strap may need to be replaced.

When I’m deep in a training block where I’m always pretty fatigued I can’t get my HR over 175 or so despite having a max around 205, so it could just be a fatigue issue. Strange that you’ve been able to PR like that though. When I’m in that state I usually can’t run within a minute of my 5k pr without taking a few good recovery days.

Thanks for all the replies.

I wanted to experiment a bit last few days. So I ran with the HRM on easy and had rated up 180-totally wrong. I actually turned off the strap mid run and used the wrist watch. Had far more sensible 140 type results. So it does seem to be the strap and I thought issue sorted. But for a moment during the easy run with the wrist my rate went up to 184 going easy. It was just a brief spike and I'm putting that down to the wrist inaccuracy.

Manual check (not that's very accurate) showed more like 130.

I'll get a new strap and try that. Thanks for all the help. There's a lesson here that even straps don't always work well.

I have got and used the new HRM. That was clearly the issue. Lovely smooth curve this morning from 120 up to 181 at end at fast finish Half Marathon progress run. Thanks. My Garmin "Training Effect" and VO2 max estimates are also more sensible now too.