A Flight Attendant reported that jump seat restraints on the CRJ900 aircraft have a design flaw that makes their use hazardous to the occupant.

Narrative

The flight attendant jumpseat seatbelt harness assembly on the Bombardier CRJ900 series aircraft has a serious design flaw. Whenever a flight attendant occupies the seat we all have the same complaint. With the slightest movement on the part of the occupant the lapbelt on the seatbelt assembly rides up the flight attendant's breast bone (sternum); thus creating a serious hazard in the event of a hard landing or worse; an accident. This has been noted by each and every flight attendant I have spoken to and many now are opting to not wear the shoulder harness part of the assembly at all during critical phases such as landing and takeoff. I myself have reported this safety problem to both management and union alike; no one seems willing to address the issue. Their attitude seems to be: 'well; it was already approved by the FAA; they're not going to change it now.' I believe this is a very serious issue and I know I am taking a great risk by coming forward with this complaint. But our inflight management has done nothing to even investigate the concerns of myself and others. It is my dread fear that in the event of an emergency where significant g-forces are present; the flight attendants will be rendered useless to assist flight deck crew or passengers and will need immediate medical assistance themselves just to evacuate the aircraft.