Pro cycling has moved toward shorter cranks (165-170mm) in recent years for three reasons: reduced hip closure at top of pedal stroke (better for aero TT positions), smaller range of motion at the knee (easier on ageing joints), and higher effective cadence. Shorter cranks may cost a small amount of low-cadence leverage but rarely affect FTP once adapted. Worth experimenting with for riders who ride aggressive aero positions or have hip/knee issues.