Foot Flexibility and Alignment Are Weakly Correlated with Multisegment Foot Kinematics During the Landing Task.

Background: Flat feet show increased foot motion during dynamic tasks. Although the increased motion is one of the risk factors for sports-related injuries, few studies have investigated how foot flexibility affects foot kinematics during landing. This study aimed to investigate the relationship between foot alignment, foot flexibility, and multisegment foot kinematics during a double-leg landing task in healthy participants.

Methods: Thirty-eight healthy volunteers (50% female) participated in this study. Their mean ± SD age was 22.0 ± 1.3 years; height, 166.1 ± 8.9 cm; and mass, 57.5 ± 8.8 kg. Foot alignment and flexibility were assessed using normalized navicular height truncated (NNHt) and the navicular drop (ND) test, respectively. A multisegment foot model was used to record shank, rearfoot, midfoot, and forefoot motion during drop landing from a height of 30 cm. Peak angle and range of motion were measured for each segment from the initial contact to 200 msec after landing. The relationships between NNHt, ND, and foot kinematics were explored.

Results: The NNHt was significantly correlated with peak rearfoot eversion angle (r = -0.353). The ND test values were significantly correlated with midfoot dorsiflexion and forefoot inversion excursion (r = 0.364 and 0.356, respectively). No significant correlation was found for the other kinematic outcomes.

Conclusions: Foot alignment and flexibility should be evaluated separately because these foot measurements were correlated with different foot motions. However, it may be difficult to predict foot motion during the landing task by evaluating foot alignment and flexibility.