My memory of this is that shorter cranks are harder to push, and due to the reduced distance reguired to make a reverlution act like a harder gear.But they will still spin out at maxium rpm more or less the same. So its not baloany as reguards effort, but it does not result in a difference to gearing in inches. So not a substute for a larger chainring ,but some powerfull riders find shorter cranks better for their sytle.