Fig. 5. (A) Recoveries R are plotted as a function of walking speed for both adults (triangles) and toddlers (circles). (Adult data were reproduced from Willems et al., 1995.) In both age groups R shows an inverted U-shape relationship with walking speed. R reaches a maximum at lower speeds in toddlers. (B) Adult (triangles) and toddler (circles) R-values are plotted as a function of the dimensionless froude number. In both age groups R is maximal around froude number 0.4. In toddlers, however, R is smaller than in adults. (C) % Congruity expresses the % of the gait cycle during which E_k and E_p are oscillating in-phase. % Congruity shows a U-shaped relationship with speed, reaching a minimum at the speed when R was maximal. (D) % Congruity shows a U-shaped relationship with froude number and is minimal at froude number 0.4. (E,F) Relative amplitude RA. The amplitude of E_k is much larger than the amplitude of E_p. With increasing walking speed (or froude number) the E_k oscillations increase. However, they never exceed the fluctuations in E_p (cf. RA always >1). r² values apply to toddlers only.