I think another useful way of looking at it is most of the energy stored in the frame is returned along the peak force vector. If that peak force vector is tangential to the pedal arc (as it is when the peak force is applied at the 3 o'clock pedal position), then that work can be returned into the drivetrain. If that force vector is perpendicular to the pedal arc (6 o'clock pedal position), it is not returned in a useful way.
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Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --
the tiniest sprinter