Did I experience a Heart Palpitation?

Note that I’m scheduled for a health test soon so I don’t assume TR users to diagnose me in place of a professional but was just wondering if anyone experienced the same issue as I did when training a few days ago:

The workout was Kosciuszko (VO2 Max 8.4 Progressive) and I added an extra 5 mins warm-up time.
The first interval was 295W for 5 mins - my FTP is 274. It felt a lot harder than 295W and later I did a diagnostic & battery check on my Stages SB20 and it appeared my batteries were low (2.7v vs 3.3v for a fresh battery) even though I had only changed them a month beforehand.
So my assumption is that I was putting out more wattage (felt like > 400W) than was actually being displayed.
About two-thirds of the way thru the interval my power started to drop and I simply could not hold the required power.
I suddenly got dizzy at the end of the interval and had to dismount and lie down.
My heart felt like it was really pounding in my chest - it didn’t feel like a really high rate (my max is 173), moreso a very intense/strong beat.
I had to lay there a few mins to recover, wondering whether what I experienced was a heart palpitation or something similar…

I only had my breakfast approx 15 mins before the workout (I’d usually have it several hours beforehand) so I this was probably not long enough possibly to absorb breakfast to get the energy availability.
I decided to get back on the bike and try finish the workout.
The second interval felt pretty tough so I horsed an energy gel into me.
I started to feel better pretty quickly.
I was able to complete the full workout and also to hit a 5 min power PR on the last interval (hit 350W vs previous season best of 311W), not sure why I tried for a PR - maybe as a “stress-test” to see if the initial issue reoccurred.

As a result of being able to complete the full workout, I was less concerned about the initial issue I experienced, and believe it was more related to an energy deficit vs a cardiac issue.

Anyway - just wondering if TR users have experienced something similar beforehand to see if this is a more common occurrence than I’m aware of - thanks!

I’m no medical expert (and I’m glad you are seeing one). From my untrained eye it looks like having only ate 15mins before you simply ran out of energy in that first interval. When I do a high cadence gravel ride I’ll sometimes feel my heart pounding at the top of a hill yet I’ve got nowhere near my max HR. Yet on the trainer or road bikes my heart goes up to a much higher level before I find it pounding my chest when I stop. I doubt you’ve got anything to worry about but you are seeing the right person to put your mind to rest. Well done btw on completing the workout and setting a power pb :muscle:

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Could also be hypoglycemia because of the timing of your breakfast. Eat earlier if possible or start eating when active (as soon as the workout starts).


thanks for the opinions @HLaB & @PhydomiR :+1: I do think it was more an energy deficiency than anything else