An insert for repositioning at least one of the harness straps of a child safety seat in order to accommodate an occupant smaller than the harness is configured to accommodate, wherein the insert is adapted to locate between the child safety seat and the occupant and includes a pair of waist strap guides, each waist strap guide configured to allow a waist strap of the harness to extend through and exit the waist strap guide at a position narrower than where the waist strap exits the child safety seat.

The invention relates to a child safety seat (100) comprising an integral harness belt (102) for restraining a child in the child safety seat (100), a belt tension monitor (106) adapted for monitoring a belt tension acting on the harness belt (102), a motorized harness belt tensioner (104) comprising a tensioning element (114) driven by an electromechanical actuator (122) and adapted for adjusting the belt tension acting on the harness belt (102), and a controller adapted for controlling the motorized harness belt tensioner (104) to adjust the belt tension to match a first predefined belt tension and for monitoring the resulting belt tension using the belt tension monitor (106).

A child safety seat for fitting on a vehicle seat of a vehicle, having: a seat element, a backrest element, in particular with an upper backrest part and a lower backrest part, wherein the backrest element is pivotable between a use position and a transport position, two side elements which are connected to the longitudinal edges of the backrest element, wherein the side elements each have a viscoelastic foam plate and a substantially air-tight outer casing around the viscoelastic foam plate, wherein the viscoelastic foam plates are held on the backrest element with fastening elements, wherein the fastening elements penetrate the viscoelastic foam plates and the outer casings in such a manner that air suction openings for sucking up air into the viscoelastic foam plates are formed.