Originally Posted by
nycphotography
True.
When the HR shoots up, it's time to dial it back.
My question has always been (and nobody has ever really given clarity)... if I can do the same effort at 200 watts (z3) and 75 cadence at a HR 140 (z3), OR I can do it at 200 watts (z3) at 95 cadence at a HR 155 (z4), which is the anaerobic and which is the aerobic? Which is burning more (transient) glycogen and which is using more (sustainable) fat?
On the one hand, the HR is higher when spinning.... but on the other hand, that's the aerobic capacity being tapped. Nobody has ever really explained the impact on glycogen use from one to the other.
I think your example is probably exaggerated but they're both aerobic exercise. The lower cadence is a little more efficient.
The heavier you are the bigger the difference in HR between low and high cadence. At higher cadence if you've got excess weight on your legs there is a lot of wasted effort moving them up and down.
I've done 5 min intervals a little above threshold and compared HR for different cadences. I saw some differences but it wasn't more than about 5 beats as I recall. A little hard to tell as HR was changing with each successive interval but certainly never saw as dramatic a change as you mentioned above.