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Fig. 1. Adult Ep and Ek oscillations are
plotted as a function of gait cycle duration. The shaded area indicates the
periods of double support. The IP mechanism, as observed in adult gait, shows
an out-of-phase oscillation of kinetic and potential energy, allowing energy
exchange to occur from Ep to Ek and
partially from Ek to Ep. Though 70% of
the required mechanical energy can be recovered due to this energy saving
mechanism, 30% of energy is lost and must be re-supplied by the muscles. It is
primarily used to redirect the centre of mass from one pendular arc to the
next. HC, heel contact; OTO, opposite toe-off; OHC, opposite heel contact; TO,
toe-off.