Stride length and speed for adults, children, and fossil hominids

Research workers studying the relationship between stride length (L) and speed (u) in human walking have often expressed their results as multiples of stature (h): they have given values of L/h and u/h. They have claimed or implied that this takes account of differences of body size and that L/h should be the same function of u/h for people of all sizes. It is shown that this is not true for comparisons of children with adults. Further, it is argued by dimensional analysis that \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm u/}\sqrt {{\rm gh}} $\end{document} is a more appropriate speed parameter that u/h (g is the acceleration of free fall). It is shown that L/h is approximately the same function of \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm u/}\sqrt {{\rm gh}} $\end{document} for children aged 4 or more years as for adults. The empirical relationship between L/h and \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm u/}\sqrt {{\rm gh}} $\end{document} is used to make new estimates of walking speed for the early hominid footprints found at Laetoli, Tanzania. The speeds obtained are equivalent to mean speeds of human walking observed in small towns (i.e., they give approximately equal values of \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm u/}\sqrt {{\rm gh}} $\end{document} ).