Ya know, one thing that's always amused me is that "the rules" say that we've gotta pedal around 90rpm when we're going faster on the flats, yet it's ok to pedal with lower revs on a tough climb, even though our output and HR are pretty much the same. So, the "rule" is: the faster we're going, the faster we must spin.

The only thing I can think of which may explain this is that it feels easier to maintain speeds on flats with higher revs when you suddenly find yourself on a slight incline If someone likes to TT at 70rpm; if they suddenly find themselves doing 55rpm on an inlcine, their speed might drop off more than if they were doing 90 to 78revs. Perfectly flat roads are one thing, but not many roads are perfectly flat, and the slightest rise can drop you're tempo ~5km/h, especially if you're not on top of your gear changes and suddenly find yourself riding at too-low revs.

I'll try to explain it again ..... if someone is grinding a TT at relatively low revs and suddenly finds themselves on a slight incline, the next thing they know they could be doing only 55rpm, and have slowed more than they may have had they been doing 90 revs and 'accidentally' dropped to 80revs. This might sound silly, but it's not always easy to concentrate on undulations and gear changes when you're dying and your HR is 190bpm!