The Effects of Walking Speed on Three-Dimensional Foot Rigidity and Multisegment Coordination.

The foot's role in movement varies dramatically across stance, absorbing shock upon heel strike, storing strain energy during midstance, and generating power during push-off. These functions are made possible by the coordinated interaction between passive and active neuromuscular structures spanning the foot and ankle. However, how coordination patterns of multisegment foot kinematics fluctuate with changes in walking speed remains unknown. Therefore, the purpose of this study was to quantify three-dimensional foot joint rigidity and multisegment coordination and variability at two walking speeds. We hypothesized that faster walking speeds would elicit decreased rigidity and more tightly regulated coordination. Sixteen adults (six males, ten females; age: 26.9±5.2 yr) completed 2 min barefoot walking trials on an instrumented treadmill at two speeds (1.0 m/s and 1.4 m/s). We used a multisegment foot model to define the ankle, arch, and toe joints to assess multisegment foot rigidity (i.e., range of motion (RoM)) and segmental coordination and variability between the rearfoot, midfoot, and forefoot across early, middle, and late stance phases. Supporting our hypothesis, faster walking reduced joint rigidity and resulted in more tightly regulated coordination, characterized by more synchronized (i.e., greater in-phase or lesser antiphase) movement and decreased variability across most planes. As a notable departure, only the midfoot-forefoot showed greater antiphase movement during late stance, indicating less tightly regulated coordination, which may allow for greater extension at faster walking to facilitate mechanical energy return. These findings provide a foundation for understanding changes in foot and ankle function due to age and/or injury, surgical intervention, or disease.