Adjustment should not be made during car movement.
To reduce risk of a proskalzyvaniye under a zone belt at collision, do not reject a seat back back, more than it is necessary. Seat belts provide the maximum protection if passengers sit directly and having moved on a seat as it is possible further back. If you rejected a back back, the zone belt can slide off and strongly press at collision on a stomach. Therefore at collision the risk of a trauma increases together with increase in a deviation of a back from a vertical.
For completion of adjustment of an inclination of a back of a seat press on it a back to be convinced of its reliable fixing.