This is a very interesting clip - certainly a hot one!
And it gives a very good view (in all senses!) of the
'dance of the cross' - but with a sadistic twist!
It's not very easy to understand the workings of all the bondage, but this is how I see it:
The bonds at the tops of her calves are secured to some shackles behind her, apparently on straps or chains suspended from the cross-bar, so she can move her legs fairly freely.
But the 'crucial' point is, there's a rope looped round her neck, and when she's hanging limp with her knees flexed, her weight is supported by the ropes round her wrists and those bonds on her legs - but the rope on her neck is pulled tight.
She has no support for her feet, so kicks about trying to get them into a position where they can press against the upright, one over the other, while she strives to lift her body, using the strength of her thigh muscles, her arms are racked agonisingly by the strain, and she's struggling all the time to keep her feet on the wood. When she briefly achieves a 'standing' position, she glances at her wrists that are braced against the ropes binding them to the crossbar - and I think they are being tugged by the ropes linked to her legs.
100 seconds of exquisite torture, extreme (and, frankly, dangerous) BDSM, but it demonstrates how the constant struggle to escape from one kind of unbearable torment only to suffer another forces a crucified female to 'dance' in an abandoned mockery of erotic self-display!