During human walking the ankle-foot complex executes seemingly contradictory functions: (1) stabilization of the human body at initial contact, (2) shock absorption during early stance [1-3], (3) Storing elastic energy during midstance and (4) providing a strong lever for push of during final stance . This quadrupled function inevitably demands a transfer from a flexible and compliant foot towards a rigid lever . Despite the viable role of the forefoot in this transfer, knowledge concerning the deformation of the forefoot is limited. The aim of this study is to provide a more detailed description of deformation occurring at the level of the forefoot during the stance phase of normal human walking.
Materials and methods
Using a seven-camera motion capture system (250Hz), a pressure platform (500Hz) and a forceplate (1250Hz), we measured forefoot deformation through kinematic and pressure related outcome measures in 60 healthy subjects.
Small but significant changes in intermetatarsal distance are established during stance phase, with the largest change occurring between metatarsal head II/III and V (Table 1). The changes in intermetatarsal distance and metatarsal arch height show slightly different patterns. Both patterns are characterized by a rapid increase in distance during initial stance, reaching a stable platform throughout midstance. At the end of stance phase the intermetatarsal distances rapidly decrease to baseline, whereas the metatarsal arch height increases till a maximum at heel off (Figure 1-5).
Table 1. Parameters characterizing the changes in medio-lateral arch height and mutual distances between metatarsal head I, II/III and V and metatarsal base I and V during stance phase and for the different subphases
Figure 1. Changes in distance between metatarsal head I - V, I - II/III and II/III – V and in metatarsal arch height: Changes in distance between metatarsal head I and metatarsal head V throughout stance phase for the left foot,
Figure 2. Changes in distance between the base of metatarsal I and the base of metatarsal V throughout stance phase for the left foot,
Figure 3. Changes in distance between metatarsal head I and metatarsal head II/III throughout stance phase for the left foot,
Figure 4. Changes in distance between metatarsal head II/III and metatarsal head V throughout stance phase for the left foot
Figure 5. Changes in medio-lateral arch height throughout stance phase for the left foot
High correlation values (>0.7 or <-0.7) are found between temporal pressure and temporal kinematic parameters.
Through stance the forefoot deforms according to a specific pattern, which is predominantly determined through forefoot-ground interaction. In addition, the changes in forefoot kinematics in combination with temporal contact data argue the existence of a mediolateral metatarsal arch and suggest the existence of an inverse arch during metatarsal forming and final propulsion phase.
The preparation of this abstract was funded by the Vrije Universiteit Brussel (i.e., GOA 59)
J Bionic Eng 2008, 5:175-180. Publisher Full Text