Peak HR >70bpm above threshold HR - possible?

[wltz]

Hi all, apologies for starting a new topic, I scrolled down several pages but didn’t use the search function. I’m a fit dude, 41, 50% road cyclist 100% gym rat, more of a track sprinter physique, but I climb pretty well for my 80kg weight and have a very decent VO2max (55-60 according to Garmin estimates). My FTP is miserable though at under 3.5W/kg.

I don’t race, ride 6 months a year when it’s nice outside, and I’m only training for and doing long solo rides at tempo, aiming for 30+ kph / 19+ mph in old money. I ride with PM, but what I really watch for is HR as it’s the most relevant metrics for my pacing and feeding strategy. When I’m fit I’d hold 270W+ NP for 6+ hours on fewer than 1500 kcal in gels and cake, as most of my energy will come from fat oxidation. My threshold HR is 155, ride average is usually ~132, and I’ve based my zones on max HR of 178 I once clocked on very hard intervals on turbo; outside I rarely get above 165 even on smash fest group rides. Sorry if most of this info is not relevant to my question.

The question is, over the years, I’ve had Tickr, Polar H10 and Garmin clock HR in the 220-230 range, over 30+ seconds, and every time it was on very steep climbs (they are short where I live) and all are memorable performances where I would kind of get into a supercharged gear and just fly up them. I’ve always dismissed these readings, and after the previous one last year I even binned my H10 and went to see a cardiologist (nothing abnormal was found). The latest instance was yesterday with Garmin HRM-Dual, on a 370m climb at 12% where I found 7 secs on my previous PB from 2021 when I was much fitter and 12kg lighter after a year of closed gyms and doing just cycling. I could feel my heart racing, but only noticed the reading after cresting. HR then quickly went back to 150.

Is such discrepancy between threshold and max HR even possible, or should I look for another cardiologist and/or HR strap? And if these readings are credible, are there any real life implications for setting HR zones, as my lactate threshold HR is still 155.

[wltz]

Screenshots of representative efforts if at all relevant.

[Aeo]

You need to find a reliable way to measure your heart rate

Wittgenstein's Ruler

[TobinHatesYou]

Talk to your doctor. In the meantime wear two HRMs and see if they both catch the same pattern. It could be any number of non-sinus tachycardia. Some are largely benign like SVT, and some are higher risk like Afib.

[wltz]

Talk to your doctor. In the meantime wear two HRMs and see if they both catch the same pattern. It could be any number of non-sinus tachycardia. Some are largely benign like SVT, and some are higher risk like Afib.

Thanks Tobin! You are always so generous with your time fielding all sorts of questions!

SVT triggered by exercise was what we discussed with the doc after 2 episodes in 2022 (gosh time flies, I thought it was last year). Then there was nothing for 2 years on the dot, and I might have to wait another couple years for the next one. I mean, a rare cardiac irregularity was my understanding as well, but the fact that I get a performance boost mid-climb where I would normally gas out, and the symptoms are benign as far as I can feel and tell made me wonder whether it's a kind of untapped superhuman reserve I guess I should get real based on your answer, and anyways HR zones set on 179 max are consistent with PRE.

Apple Watch 9 clocked 196, but I don't use it as HRM for cycling workouts, so the resolution is once every 2 mins. An older gen watch clocked 185 in the event back in 2022.

[Requiem84]

Optical HR is notoriously unreliable. HR straps are 99% accurate (when new).

[wltz]

Ditto, and that’s why it’s on my wrist as a watch when cycling. But better than nothing for day-to-day, and I use it for heavy gym sessions as HRM to gauge rest time between sets.

Accuracy is a separate topic though. I just wanted an opinion from the sports physiology perspective. I won’t get a good answer from general medicine unless and until these episodes become more frequent, so at least I wanted to rule out the possibility of my HR zones being off by a huge number.

[Aeo]

Your spleen can contract and release a quantity of oxygen-rich blood as part of the mammalian diving reflex. Don't think that's happening.

Depending on your persuasiveness, you can ask your doc for a long-term ECG device like SmartCardia or S-Patch. Even if you don't catch an episode, you can check your sports sensors against something FDA-approved

[wltz]

Oh I’m in the UK, healthcare is free but rationed. Generally you have to have a stroke or cardiac arrest to get them interested, and I am not scared enough to invest time and patience into going through my workplace private health insurer as they generally prefer to bounce you onto the public healthcare system for cardiac stuff. Not a good country to be a hypochondriac, and thankfully I’m not!

[wheelbuilder]

Keep a close eye on it with a known reliable Chest strap. It could be afib as mine started very similarly, and became more frequent over time. Afib is completely curable in most cases with cardiac ablation. I've had 3. They thought I was a candidate for the less invasive freezing method but it didn't work, so 2 months later I had the traditional heat based procedure. It worked perfectly for 8 years until I developed a single episode of a-flutter last year and immediately went in for my third. Flutter usually never comes back if ablated so I had no second thoughts about getting it done. The research is mounting regarding endurance sports and fib/flutter. Take it seriously, and I wish you well.

[wltz]

Damn, I definitely wasn’t serious enough about it. Thanks for sharing your experience, I’m glad you got patched up and it’s working, touch wood. I’ll look into getting a second strap I could wear in bed. Thanks all for your replies and reality check!

[InSeyne]

You could possibly try the Fourth frontier x2 HRM if you are serious/concerned about your heart?

[wltz]

Thanks for the suggestion! It doesn’t look like it offers anything hardware-wise that a Polar couldn’t do, but comes in a bulkier form-factor and without Ant+ - all at 7 times the street price.