For some reason I'm doing this exercise wearing my lower leg splints and shoes. Normally, I don't do this these days. I think I will try to get another more instructive clip to post, as it doesn't really show this exercise or what I am doing currently very well.
The purpose of the treadmill is different to the walking frame and crutches. This allows my legs to run and helps open up the muscle memory and instinct. Sometimes when I concentrate hard on what I am doing it becomes disordered, and when I think about something completely unrelated, my breathing calms and the legs return to doing what they've always done.
What you can see is the lower limb kicking strongly. This would not be possible to do from the hips, but must come from in the legs.
In the earlier clips you can see my toes dragging along the treadmill, whereas these days there is enough tension in the ankle and lift from the thighs that they don't do that.
The ankle weight makes the thigh work harder to lift and is all part of control and muscle building. And by making it go faster, I have to hold the tension in my legs for longer, as there can be a delay in the command to tense and relax so I wouldn't be able to get the legs forward in time if I did relax them as the treadmill takes them back. This is good as I can be too quick to let go of muscles once I've tightened them - Hratch likes to remind me about the perils of falling over at inappropriate times after I'm walking!