Unweighing the pedals is not the same is lifting. Lifting means you're actually contributing force to the pedals during the upwards part of the rotation. On the rare occasion I borrow someone else's bike with flat pedals, my feet will fly off the top of the pedals until I get used to it. That's real lifting force. I've never had a problem with excessive lifting. If you have a link to that study I'd be curious to read it.
Yes, but studies where participants thought they were "lifting" the pedals showed, they weren't actually contributing significant force on the upstroke either. But they were contributing a tiny amount of force on the upstroke which means they are using foot retention in the studies. Participants are a mix of competitive and recreational cyclists.
I have posted a chart a few posts up (re-posting below). Those are actually multiple charts I stacked on top of each other to show how the invested muscular effort looks like throughout the pedal circle against actual returns.
Sources for the charts:
https://www.researchgate.net/publica...during_cycling
I used these charts below and stacked them together:
The stacked charts + the chart in the linked study (the shaded lines are leg muscular activity, the one in red is at the upstroke quadrant, considerable muscular investment for little return that's why I colored it red):
Note these charts isn't meant to prove clipless is worse but rather pulling hard is a bad technique. Like I've said clipless is still best for efficiency but only with the right technique!
Segment from GCN showing Simon was slightly more efficient on flat pedals even though he rode on clipless most of his life!! Clipless isn't to blame here but the due to the fact Simon is probably pulling too hard on the upstroke.