the invention relates to a vehicle seat for equipment with shoulder belts connected to the seat backrest , comprising an energy absorbing device acting on the seat backrest , wherein said energy absorbing device comprises deformable energy absorbing means , with at least one arcuate area of plastically fragmentable material , opposing the rotation of said seat backrest with respect to a lower seat structure in a first direction , corresponding to a forward - leaning movement of said seat backrest . the invention also relates to energy absorbing devices opposing the rotation of a first part with respect to a second part via deformable energy absorbing means with an arcuate area of plastically fragmentable material , wherein the energy absorbing device comprises releasable retention means subjecting every rotation of said first part with respect to said second part into a first direction to the reaction of said energy absorbing means and allowing the rotation of said first part with respect to said second part , into the direction opposite to said first direction , without acting on said energy absorbing means .