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Fig. 7. (A) The phase angle (rad) between the peak in the forward push of the back
leg (peak Ff,back) and the beginning of the double contact
phase is presented as a function of the walking speed expressed as a Froude
number. Each age group is presented with a different symbol (filled circles,
3-4 years; squares, 5-6 years; diamonds, 7-8 years; triangles, 9-10 years;
inverted triangles, 11-12 years). (B) The mass-specific work per distance done
by one leg against the other (Wint,dc; J kg-1
m-1) is presented as a function of the Froude number for all age
groups. The broken lines show the adult trends.