Crank Length Swindle (and rant) (Video)

A lot has been made about crank length in recent years, and I've even done a few videos about them in the past.https://youtu.be/59y7ybQoN8g

• recently a rider came in needing help with their bike fit
• he'd been working with a triathlon coach who also considered himself a bike fitter
  • in the course of  of the fitting he decided the rider would benefit from shorter cranks and a couple other changes
  • he ordered the new cranks, put them on and hooked the rider up to a glorified power meter and declared that his power looked much better and eventually sent him on his way
  • Problem: previously the rider had 172.5 mm cranks on his bike -- the new cranks were 170 mm
    • 2.5 mm difference which in this context is basically a worthless change.
      • not that it doesn't have "some" effect, just that the effect is in no way worth the $350 price tag of the new cranks
  • analogy: in car racing if you wanted to make your car lighter in order to make it ru the quarter mile faster, you'd be doing well to lose 200 pounds
    • this crank change would be like paying a bunch of money to lighten your car by 20 pounds -- not a good deal
• I bring this up for a couple reasons
  • partially this is a rant - I'm angry that someone was taken like this; this just shouldn't happen; it doesn't help out anyone, least of all the client and other bike fitters who are trying to be careful and ethical
  • also a caution to riders out there:
    • a 2.5mm or even a 5mm change in crank length is not going to make a tremendous difference especially considering the cost. If you would benefit from a shorter crank and you were getting one crank for free that was 5mm shorter this of course could be a worthwhile test. -- this was a complete waste of time and money
    • changes i power can only reliably be interpreted over a long period of time. If you have a bike change done for instance raising the saddle and then you immediately do a "power test" (whatever that might entail) this test will tell you very little as far as concrete facts
      • if you notice research articles on cycling you'll know that they never include this type of immediate testing of direct power; there are too many contributing variables to this power to draw any meaningful conclusions
      • most clients in a bike fit, if you test their power after changes are made they will have higher power outputs merely because they're excited about having changes made and they "want" the bike fit to be working
        • even intricate measurements of pedal vectors, joint moment angles, angular velocities etc need to be taken with a grain of salt with the understanding that these are the changes we're seeing now, but the body still has to adapt more fully to the position and so further changes will occur
• this begs the question, how short of a crank should I get if I need a shorter one?
  • I'm doing a second video which you can click here to see that goes into the research and the nuts and bolts of where to start and how short you might go