when you ride with higher cadence, you put more pressure on your heart rather than muscle, so your body will need more oxygen. Just like driving a car at 50mph, using 3000 rpm will cost more fuel than 2000.
everyone should have his/her most efficient cadence range, to find it, do some one hour 95-100% ftp workout, at some different cadence range(Use your most favorite cadence, for instance 90+-2, that would be 86-88-90-92-94) find at what exact cadence you have the max power output and a relatively low HR. :)
everyone should have his/her most efficient cadence range, to find it, do some one hour 95-100% ftp workout, at some different cadence range(Use your most favorite cadence, for instance 90+-2, that would be 86-88-90-92-94) find at what exact cadence you have the max power output and a relatively low HR. :)