I read somewhere that 80-100 rpm is the most "efficient" way to cycle. At 100 I feel as if I'm about to throw myself off the bike, so I aim for 80ish. The link below is interesting but, as usual for me, overcomplicated!
http://www.bikeradar.com/fitness/art...-matters-16394
Interestingly, a Japanese group [3] studying ‘college-aged cyclists’ found that the cadence with the lowest oxygen cost (VO2) was not the same as that producing the lowest muscular fatigue. Measuring the electrical activity of cycling specific muscles, called an electromyogram (EMG), they found 80-90 rpm had significantly lower EMG activity than any other cadence (70rpm, 100rpm) [3].
However, the lowest amount of oxygen was used when pedalling at 60-70rpm, significantly less than 80-100rpm [3]. So, muscles have better neural efficiency when spinning, but this increases oxygen cost. To what extent these can be further trained is not clear, but the fact that professionals can ride at high cadences for hours and that club-level riders tend to ride in ever lower cadences as they tire, suggests cadence is a vital parameter for training.