Kinematic adaptations of the hindfoot, forefoot, and hallux during cross-slope walking

Despite cross-slope surfaces being a regular feature of our environment, little is known about segmental adaptations required to maintain both balance and forward locomotion. The purpose of this study was to determine kinematic adaptations of the foot segments in relation to transverse (cross-sloped) walking surfaces. Ten young adult males walked barefoot along an inclinable walkway (level, 0° and cross-slope, 10°). Kinematic adaptations of hindfoot with respect to tibia (HF/TB), forefoot with respect to hindfoot (FF/HF), and hallux with respect to forefoot (HX/FF) in level walking (LW), inclined walking up-slope (IWU), i.e., the foot at the higher elevation, and inclined walking down-slope (IWD), i.e., the foot at the lower elevation, were measured. Multivariate analysis of variance (MANOVA) for repeated measures was used to analyze the data. In the sagittal plane, the relative FF/HF and HX/FF plantar/dorsiflexion angles differed across conditions (p = 0.024 and p = 0.026, respectively). More importantly, numerous frontal plane alterations occurred. For the HF/TB angle, inversion of IWU and eversion of IWD was seen at heel-strike (p < 0.001). This pattern reversed with IWU showing eversion and IWD inversion in early stance (p = 0.024). For the FF/HF angle, significant differences were observed in mid-stance with IWD revealing inversion while IWU was everted (p < 0.004). At toe-off, the pattern switched to eversion of IWD and inversion of IWU (p = 0.032). The information obtained from this study enhances our understanding of the kinematics of the human foot in stance during level and cross-slope walking.