Originally Posted by cydewaze
Not sure if I buy the bit about the BB flex being returned and reused. At the bottom of the pedal stroke, there's a "flat" spot during the transition from one pedal to the other. I think probably the BB just unflexes when the load is removed, and that energy is lost.
If people were machines and the pedal stroke was a perfect circle, then yeah, maybe I could see some of that energy being returned, but I don't think it's very realistic to assume that we're getting any forward assistance out of that on a typical pedal stroke.
The bottom bracket sways out on the down stroke and then returns to center by itself when the load is removed; net result is no energy loss. The only way energy could be lost is if it's converted to another form of energy such as heat. Simple physics.