Fig. 4. Representative ground reaction force (GRF) components from typical trials for one subject sprinting at each radius of curvature normally (A) and with a tether supplying external centripetal forces (B). Straight path sprinting is shown for comparison (thick gray lines, symmetry assumed for straight path) and correspondingly smaller radii are indicated by progressively thinner black lines (6, 4, 3, 2, 1 m). The inside leg (left) and outside leg (right) are indicated for each GRF component. (Ai,Bi) Vertical GRF. Fore–aft GRFs (Aii,Bii) indicate negative, braking forces followed by positive, propulsive forces in each case. Positive lateral GRFs (Aiii,Biii) indicate centripetal forces acting at the feet. Corresponding tether forces are shown with indicated curve radius (Biii, inset).