lots of this here:



1. pros do not always spin faster in TT efforts: see Bert Grabsch, Jan Ullrich. not to mention that the same fast cadence people might be spinning just as fast in a peloton anyway.
2. faster cadence does not mean "aerobic". all cadences would be aerobic, unless you are doing a kilo on the track or something. Even then it's still a good percentage aerobic.
3. efficiency (more power per level of perceived effort), as pcad pointed out, can happen at lower cadences. I remember the case study in question, and they established that 80rpm was the most efficient cadence on average for the test subjects (well-trained athletes)
4. whether the low cadence produces more power is not the reason why people tell you to spin faster. The reason is to get you used to making power at higher spins so that your legs don't wear out too soon in a race.
5. one of the best TT guys in the state pushes a ridiculous gear. He did the entire ESG time trial in the 54/11 or something. Real grinder. But he only does TTs. You can imagine why.

this is not the study, but it makes references to several of them:


http://pezcyclingnews.com/?pg=fullstory&id=4011

a check of google scholar would likely reveal some of the source materials, provided you have access to the full text.