This is the Rolls Royce of passive back bends. Kit is applying traction to Olivia's shoulders by leaning back from where she is gripping his thigh, and he is gripping the fascia “sleeves” of her arms, and Dave** is applying traction to all the superficial fascia over her ribs in the opposite direction to Kit's force. Her whole spine is being lengthened and all the fascia on the front line of the trunk is too, as a result. Dave's hands also provide tactile cues for Olivia to direct her breathing into those parts of the chest and ribs.
** Dave Wardman – long-time collaborator and colleague of ours. Find him at Physical Alchemy.