Novel proprioceptive action in stepping down.

A hypothesis is offered which extends the concept of proprioception to use information necessarily obtained during the first part of a complex motion (stepping down) to facilitate the second part. It is suggested that, when the leading foot of a normal person stepping down arrives at its destination, relevant proprioceptive information is used by the following foot in its descent, to render its movement more efficient. Analogy to another effort-minimizing proprioceptive mechanism and a possible mechanical manifestation of the hypothesis are given.