Fig. 7. Simulation results of peak spring force (F_spring) and maximum spring compression (l) for a 15 cm step in the second contact dependent on a variation of spring stiffness () and angle of attack (_TD). All simulations started before the first contact on ground level with identical initial conditions (_x,0=4.5 m s^-1, y₀=0.95 m) and system parameters (=35.7, _TD=68 deg., m=80 kg, l₀=1 m). (A,C) By using a fixed angle of attack and decreasing spring stiffness we found that spring force decreased while spring compression increased. Dash-dotted line, =25.5, _TD=61 deg.; dotted line =19.1, _TD=61 deg.; dashed line, =12.7, _TD=61 deg. (B,D) In the case of varying (steepening) the angle of attack and using a fixed spring stiffness, spring force and spring compression decreased. Dash-dotted line, _TD=59 deg., =19.1; dotted line, _TD=61 deg., =19.1; dashed line, _TD=63 deg., =19.1.