probably...

they did plenty of body mechanics experiments during WWII and the cold war

(it's also how they were able to come up with the Systema martial arts discipline)

but based on these documents, I think it would be strictly CNS experiments and the pictures don't seem to indicate any prolonged use without oxygen supply from the environment

I'm a bit skeptical though with the way they made the hydraulics compared to actual aerospace projects(which are the state of the art of USSR at that time)