Through the years I've done several similar breathing sessions.
Reichian breathing and transformational breathing mostly. I guess 7 sessions in total. The first 3 in group sessions the last 4 in 1 on 1 sessions. They all ended in my body cramping up, My hands turn into claws, my face tightened so much the last few sessions they put a tube in my mouth so I could still breathe. All in all very unpleasant. Decided after the last one that this kind of breathwork is just not for me. No release or katharsis what so ever.