There isn't really conclusive data for a couple of reasons, One, there is a big individual variance. (see e.g. Jan Uhlrich v. Lance Armstrong), Two, it depends on your definition of efficient.


For example, higher cadence may well not be as "efficient" from an aerobic point of view. However, if the higher cadence leads to less muscle fatigue, and allows you to produce power longer, it may be "better" even though it is not as "efficient" in turning oxygen uptake into power output.

It's also situational. Best cadence for climbing may not be the best cadence for racing in a crit, with lots of accelerations, nor the best cadence for a TT.


All that said, you got to find what works for you.