This is clearly 'shintaisou'/Princess 69/Rhythmic Gymnastics reference. But I'm not sure if tag should be added for this.

Shintaisou was a huge let down for me.

The very first art and screencaps I saw for it got my attention with the promise of cute girls in lewd gymnast poses wearing sexy leotards and also some yuri.

Then I dug a little deeper and found it is in fact full of rape and torture and then my interest in the series suddenly vanishes.

There was a nice scene at the beginning of one episode with one of the girls getting off on a hula hoop during solo practice. I really wanted to see more like that.