Fig. 7. The average rate at which negative work is performed on the COM (, see shaded areas in Fig. 6) fell with increasing arc foot radius . The Simplest Model Fit of Eqn 10 predicted the trend well (r²=0.95). The magnitude of work rate was greater for small arcs than for normal walking (broken line), and lower for arcs of approximately >0.2. Less work is needed to redirect the COM velocity with larger arcs, due to a smaller directional change during the step-to-step transition. The work rate observed with the smallest arcs was 2.37 times that for the largest arcs. Different coloured symbols indicate different subjects.