The present results suggest that the kinetic factors of ankle
power and workload were lower during backward walking
than in forward walking. Since there were no significant
differences in walking times in this study, it is likely
that plantar flexion plays only a small role in propulsion.
Ankle power during forward walking included both plantar
flexion caused by muscles and plantar flexion caused by the
non-contractile extensibility (utilizing elastic energy) of the
Achilles tendon acting as a spring5)
. However, the plantar
flexion power of the ankle during backward walking was
low even when the angle of dorsal flexion prior to plantar
flexion was large. This indicates that the influence of noncontractile
elastic energy on plantar flexion is small. Thus,
the propulsive force in backward walking must come from
some factor other than the ankle. Possible sources of the
propulsive force are compensation through hip power and
the center of gravity.