Fig. 2. The effects of passive tools in augmenting human locomotion on land. World
records in terms of average speed and performance duration are represented.
Vertical curves show the iso-duration relationship between the abscissa and
the ordinate. From bottom to top the different locomotions (as indicated in
the key) become more and more specialised, starting from running (open
circles) to bipedal-like gaits (cross country ski – CCS – and ice
speed skating), from hybrid legged-wheeled progressions (roller skating) to
just-wheeled ones [cycling; the unicycle records shown at the bottom of the
graph represent a simultaneously inefficient and uneconomic locomotion because
of the lack of gears (2) and the additional balancing burden
(4)]. Superimposed on the graph, are iso-metabolic cost (in J
m–1) curves (blue, t<10 min; red,
t
10 min). For a mathematical discussion of estimation of their
speed values, see Appendix.