For most power using 145s* see--e.g.,

"...a study** done by Jim Martin at the University of Utah (Determinants of maximal cycling power: crank length, pedaling rate and pedal speed). What did this study show?"


Ref: https://www.powercranks.com/cld.html


**Jim Martin's study (University of Utah) is used by manufaturers to justify making fewer options available, but the research showed that going as low as 145mm may actually help put you closer to your peak efficiency.


* http://www.ncbi.nlm.nih.gov/pubmed/11417428





Personally, my experience on training equipment has seen steady improvements in both pace and cadence going to 106 mm cranks.