Unusual Heart Rate Spikes While Running

lporter229

I have recently had an unusual phenomenon occurring with my heart rate while running that has me a bit concerned. It has happened several times (not every time I run) over the past few weeks and usually on easy paced runs. I will be cruising along at a comfortable pace, even chatting with friends, and I look down to see that my heart rate is spiked at 180-200+ BPM. Here is an example (HR is the pink line on the graph):

The thing is, it doesn't feel that high and if I wasn't wearing a HRM, I would never even notice. At first I was just blaming inaccuracy in my HRM, but it has happened enough times now that I am starting to feel a bit concerned. Normal heart rate for me at a comfortable pace is in the 130s, maybe up to 140s if the weather is hot. Prior to this, I have NEVER seen my HR get above the low 180s, even when sprinting hills or doing speed work. As a comparison, my last half marathon was in August and I had a 7:47 average pace and my average HR was 154 with a max of 164. My last 5K was in July and it was super hot and humid, I ran at max effort and average HR was 157, with max at 173 on a hill.

Has anyone else experienced anything like this? Could it be my HRM or could this be real data? I am using a Garmin 735XT with optical heart rate monitor.

ariceroni

I also have the FR 735 and observe similar "jumps" in my HR data from time to time. When it happens, it looks very similar to the picture you posted, typically jumping from ~150 to 180+. For me though, a HR of 180-190+ is not unusual during very hard efforts (race, 800 repeats, hill sprint, etc). When I see the spike on easy runs, I've always assumed it is something with the HRM and not actually occurring. I recently bought the swim HRM strap, so I might try running with that sometime to get a better idea of how accurate the wrist HRM is. I'd suggest next time this happens, try measuring your HR manually (counting) to see if it is a real spike or if the issue is the HRM. You could also try using a chest strap instead, though that's a more expensive (and uncomfortable) option.

lporter229

I am relieved to hear that you have seen something similar with the same model. i have tried to wear my chest strap, but I have not been able to get it to duplicate when I was wearing it. I never thought about trying to take it manually, but I will try. the biggest problem I see with that is that it will drop dramatically when I stop. I am not sure that I could do it on the run.

The_Enginerd

I've had the same thing happen with my optical armband HRM depending on the weather and the placement. Adjusting it and continuing at the same pace resulted in it settling back to an accurate HR. I've seen this happen to several people I know with the wrist based HRM in their Garmin watches as well. Keeping it tight seems to help, as due to the way it works, it mistakes the signal from the watch moving around for the signal due to your heartbeat. The algorithms and sensor designs seems to have improved over the years to minimize and filter out this effect, but it's still not perfect.

ariceroni

@lporter229 just to follow up, I recently learned that many of the Garmin models are prone to experiencing "cadence lock". Looking back, I think this is definitely what happens in my runs, and could likely be the problem you're experiencing too. Sadly there doesn't seem to be any good advice on how to avoid/prevent it though

lporter229

ariceroni wrote: »

@lporter229 just to follow up, I recently learned that many of the Garmin models are prone to experiencing "cadence lock". Looking back, I think this is definitely what happens in my runs, and could likely be the problem you're experiencing too. Sadly there doesn't seem to be any good advice on how to avoid/prevent it though

Yes, I believe this is what was happening. At the advice on @The_Enginerd, I am now using a tighter notch on my wrist strap and I have not experienced this since.