DarkSpeedWorks wrote:
Why do you think that common sense seems to run counter to the research regarding crank length? What do you think is flawed, the common sense? The research? A little of both?
The research (much of which comes from my lab) is solid. The common sense is also solid but incomplete. Muscles have force-velocity characteristics as well as activation and deactivation dynamics. That is, muscles must become activated, produce force while shortening, relax, and undergo lengthening each cycle. Once all those factors interact, crank length simply doesn't matter for maximal power or for submaximal efficiency. At least not within a really large range.
DarkSpeedWorks wrote:
Another related question, is
any part of bike fit (anything at all--for example any of the typical anecdotally-accepted tri bike fit guidelines and accepted wisdom from various tri bike schools of thought) actually supported by decent peer-reviewed reseach?
I don't follow any of the fitting protocols so I simply can't comment. Here's my simplistic approach to fitting for aerodynamics and crank length together.
1. Decide how close to horizontal you want your torso. Closer to horizontal is generally more aero but requires really holding your head up to look ahead. You could do this part of the fit with cranks stationary and horizontal, its just to find out how low you're really willing to go.
2. Once you have dialed in the seat-relative-to-elbow pad position for how low you want to go, you can determine crank length. Proper crank length would be the one that gives you a reasonable hip angle as you come over the top. This is also influenced by fore-aft saddle position which serves to rotate your body about the bottom bracket. Of course you must adjust seat and elbow pad height to accommodate each crank length. If you're tall and thin, regular sized cranks will probably work just fine. If you're under about 5'10" or thickly built, you'll likely need shorter cranks (unless you want to sit up pretty high).
3. Done.
I went through this process to set up a UCI legal position (nose of saddle 5cm behind bb) for myself for track cycling. I wanted absolutely horizontal torso. At 5'8" 160lb, I needed 145mm cranks to make that rideable. For triathlon I wouldn't need to go that short because the rules allow a much more forward saddle position. Probably a good place to start any fitting procedure is with the saddle as far forward as the rules allow.
Cheers,
Jim
PS I am not a bike fitter except for myself. I have, however, published several papers on cycling crank length and cycling aerodynamics, and spent untold hours in wind tunnels.