Heart rate, Watts, and Cadence

Today I did Monitor +2 (I redid my plan recently and what it had put in made no sense), and I was playing around with cadence. I also am someone with a really low initial FTP (118) and this was seeming a bit easy, so I had it cranked up to 105%

I’m a 50 year old male and haven’t tried to find my actual max heart rate for years. I’m running in ERG mode, so same watts no matter what.

During intervals, my heart rate ramps from about 133 to 135 and then recovers nicely, at my usual cadence of 85 RPM.

If I crank that up to 95-100 RPM, I get a lot more sweaty, and I breathe harder, and my heart rate? Exactly the same. If anything, it recovers a bit faster than usual.

If I dial it down to a mashing 70 RPM, my legs burn like crazy. And my heart rate? Exactly the same. Recovery is a little slower than usual.

I guess I’m surprised that perceived effort doesn’t have hardly any impact, so I guess the rate is just a reflection of watts and nothing else. So the next question is, how much harder should I be pushing to see if I can make it go higher (if at all at this point)?

I have found for lower watt efforts sweetspot that require below FTP range, that with a lower cadence will correlate with decrease in HR. Very short anaerobic efforts up to a minute, my observation that HR will not change much with different cadences. Longer efforts 2 minutes and above, I find a lower cadence 76-84 will result in a lower HR, than 90 and above. At 66, I have found every heart beat saved is valuable, keeping cardiovascular stress loads down. I hope this is helpful.

The accepted wisdom seems to be that slow cadence taxes your muscles more and fast cadence taxes your respiratory system more. I find that if I spin fast my legs feel less tired but my HR goes up a little - not massively though. Also my cadence tends to be higher on the turbo (100rpm ish) compared with the road (95rpm). That said I find that SS/endurance and threshold stuff is best done at a moderate cadence to tax muscular endurance. But VO2 max sessions I really ramp up the cadence to a/ tax my cardio system to try and up the oxygen intake - which is what they are about and b/ The power is so high the high cadence keeps me away from the possibility of the “death spiral” in ERG mode.

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