Density contour plot of the action changes with respect to the initial state for all sampled particles. The left and right panels show the case of the constant bar models and the decelerating bar models, respectively. In both panels, the orange contours represent models with spiral arms, and the blue contours show models without spiral arms. Spiral arms only have a small impact on the orbital properties of the particles. The sampled stars under the decelerating bar have a much wider distribution in ΔJ_ϕ and ΔJ_z compared to those with the constant bar. The majority of the particles lose rotation (ΔJ_ϕ < 0) and only a small fraction of them (19%) have gained rotation from the bar during the last 6 Gyr.