Ankle-hip joint trade-off in normal gait: Exploring the kinematic influence of the medial longitudinal arch of the foot.

Background: In human gait, leg progression into the swing phase involves two primary strategies: ankle plantar flexion and hip flexion. These strategies are believed to exhibit a trade-off relationship; however, it is unclear whether this relationship holds for normal gait and the role of the medial longitudinal arch (MLA) in shaping these strategies.

Research Questions: Does a trade-off relationship exist between ankle plantar flexion and hip flexion strategies during normal gait in young healthy adults? Do the kinematics of MLA during gait influence the strategies during leg progression into the swing phase?

Methods: Data from 36 young healthy adults were analyzed. Gait speed and peak moment, angular impulse, peak power and joint work at ankle plantar flexion and hip flexion were assessed within the context of the normal gait task. The parameters were also assessed using ankle-to-hip joint ratios (ankle/hip indices). Kinematics of MLA, including peak MLA angle, amount of descent, and amount of elevation during gait, were also measured. To exclude the effect of gait speed, partial correlation coefficients were employed to explore the relationship between ankle and hip variables as well as the ratio of ankle/hip indices and MLA kinematics.

Results: A significant negative correlation between ankle plantar flexion work and hip flexion work was detected. Moreover, a positive correlation between the ankle plantar flexion work to hip flexion work ratio and MLA elevation was detected.

Significance: A trade-off relationship between ankle plantar flexion and hip flexion strategies during normal gait in young healthy adults was confirmed, suggesting that these parameters are fundamental to normal gait. Additionally, the MLA elevation during late stance may influence the establishment of ankle plantar flexion and hip flexion strategies. These findings enhance our understanding of gait mechanisms and highlight the role of MLA kinematics in shaping gait strategies.