It’s useful to bear in mind that it takes internal work to spin your legs and feet at a particular speed. This is on top of the work that is externally applied through the pedals to move you and your bike forward against the various external forces.
Though we may not bother to think about it, it’s simple and obvious physics, and Formenti’s group at Kings’s College have published data to quantify that work in terms of watts/kg (of rider). We’ve had some good discussions about this in the SS/FG Forum.
This internal work is strongly dependent on cadence. For me as an example, I need about 75 watts just to spin my legs at 110 rpm, about 55 watts to spin at 90 rpm, 25 watts at 70 rpm and 8 watts at 50 rpm.
I think this explains in part why casual cyclists usually pedal slowly: they don’t have the cardiovascular capacity to push themselves forward at the speed they want to go while also spinning a fast cadence.
It also explains why pedaling fast and easy makes a great warmup, because there isn’t a lot of pedal force required, but you increase the CV load and get your pulse rate higher.
As the article above points out, there are many occasions to use a high cadence, but there are also many occasions to use a lower cadence, including maintaining a speed once you’ve accelerated. You will use lower total energy maintaining a particular speed at a lower cadence, but obviously that is counterbalanced by the need to maintain a cadence high enough to keep pedal force reasonable.
Otto