An adjustable seat assembly for a vehicle includes a frame and a covering. The covering has a first portion and a second portion. A flexure region, having an arched shape, is disposed between the first portion and the second portion. The covering at least partially extends over the frame to the first portion. An adjustment mechanism is operatively connected to the covering, at the first portion. The first portion and the second portion define a linear distance therebetween. The adjustment mechanism is configured to move the first portion relative to the second portion such that the flexure region moves to change the linear distance between the first portion and the second portion.