Top panel: radius evolution for various heat injection efficiencies, ξ = 0.5 (solid line), 0.1 (dashed), 0.05 (dotted), 0.01 (dot-dashed), and 0 (double dot-dashed). The classical PMS evolution, which is indicated by the thin solid line and starts at the asterisks, has a substantial overlap with the lines of ξ = 0.5. Bottom panel: evolutionary tracks with different ξ ranging 0.5 (red line), 0.1 (green), 0.05 (blue), 0.01 (magenta) and 0 (cyan). The solid, dotted, and dashed lines represent the cases with uniform heat injection, m_ke = 1, and m_ke = 0.1, respectively. In both panels, we adopt X_D = 20 ppm and R_ini = 1.5 R_⊙.