BB, I consider knees that are under extension tension to be extending, whether or not they are visibly observed as closing . I consider intentionally closing the knees with flexion tension as retraction or flexing the knees.
I don't consider the knees closing/flexing under compression forces that are experienced while skiing, when the skier's knees are actually under extension tension, as flexion or retraction or have anything to do with intentionally "backpedaling". U used to pedal my trike backwards and always had to intentionally pull my feet back by flexing my knees closed, or I stopped.
If I understand the concept of pedaling backwards, I so sometimes spin my bikes chain ring backwards just for kicks, in order to "pedal backwards" the knees must be consciously closed or flexed with flexion tension. I am assuming this is true for your use of the term "backpedaling", or you wouldn't relate the series of skiing movements to, well, pedaling backwards, or backpedaling.
Am I correct that in order to backpedal, the knees must be intentionally flexed with flexion tension or do consider any time the body is traveling faster than the skis, as the feet are returning under the body and knees are closing, to be "backpedaling"? Is it backpedaling, even though the skier may be consciously exerting extension tension and is attempting to actually extend/open the knees, but the knees are being closed/flexed due to compression forces of some kind? Compression doesn't have to be caused by a sudden change in terrain pitch, it can be experienced at the bottom of a QCT as the skis are coming back across the fall line, yet the skier's body is still maintaining speed down the fall line.
It would really help me to understand what tensions the knees are exerting in relationship to the backpedaling animation you provide. 3:00 o'clock for instance, 1/2 way up the mogul face, or 1/2 the way through a turn.
When I ski, I exert knee extension tension until the moment I breach the crest of the mogul, I then use flexion tension to close my knees in order to retract and release the turn and maintain/regain shovel edge contact to initiate the next turn down the backside of a mogul or on the edge of the groomed, it does not matter.
You animation has the skier use all of his flexion range before and maximized at the mogul crest and has none left to retract to release and keep the skis on the snow to immediately initiate the next turn.
In relationship to my skiing, you animation is "out of phase", regardless is you consider the skier to be backpedaling, when in reality, they are not pedaling backwards at all, but are experiencing compression forces that are flexing the knees against the resistance of extension tension.
I think backpedaling is actually an illusion, or maybe a myth, due to the fact that this skier is actually not doing anything related to actually pedaling backwards when turning into a mogul face.