Oh oh! I'm going to get flamed again. My personal experience doesn't match the consensus.

First of all, forget about the bike for a minute. If you were going on a journey by foot you could choose to walk, to jog, or to run. Running will get you there faster but you'll have to breath harder. I'm thinking that most people, if they don't care how long it tqkes to get there, will prefer to walk.

Why should riding a bike be different? Years ago I heard a lady bike shop owner say: "If your legs are tired, shift to an easier gear. If you're breathing too hard, shift to a harder gear." I think that's good advice. That's pretty much the way that I ride my bike.

Through spinning classes in the gum I have learned that high cadence, low resistance "sprints" kick my butt. I start panting and my heartrate redlines in no time. On the other hand, I thrive on high resistance, low cadence "hill climb simulations".

Now lets put these three data points together. If I choose to simulate a walk on my bike, I generally hold my cadence in the 70's. I do a lot of that and, honestly, many other experienced riders do too. If I choose to maintain a little "sportier" tempo, I'll generally keep my cadence in the 80's. I can hold that pace for a pretty long time. To me, any cadence above 90 is running. I have to consciously think about holding it there and I'm not able to keep that pace for any extended period.

A lot of the experimental data regarding bicycling is based on Olympic caliber riders. That's fine if you want to race, but it's not the majority of riders. Not even close. I think that most non-racers would be better advised: "If you're breathing too hard, shift to a harder gear and slow down your cadence."