Pohl J.1, Eichelberger P.1, Jaspers T.1, Ferraro M.1, Baur H.1
1Bern University of Applied Sciences, Health, Physiotherapy, Bern, Switzerland
Background: The navicular drop (ND) is widely used as a measure of dynamic foot deformation. Variation of gait style (walking/running) and speed may have an effect on dynamic foot deformation. The influence of gait style and speed on the navicular drop has not yet been investigated.
Purpose: The study aimed to gain insight into speed dependency of foot deformation that could lead to overuse syndromes of recreational and professional runners.
Methods: The ND was evaluated bilaterally in 20 asymptomatic subjects (male=15, female=5, mean age = 30, mean BMI = 22.59). Static (NDST) and dynamic (NDD) conditions were evaluated by a 4-marker foot model using a 3D-motion capture system. NDD was evaluated based on one minute recordings on a treadmill at three different walking (0.83 m s-1, self-selected velocity, 1.67 ms-1) and running speeds (1.67 m s-1, 2.5 m s-1, 3.33 m s-1). NDST was determined by five repetitive sit-to-stand test before and after the treadmill program. A repeated measures ANOVA and post hoc pairwise t-tests were conducted to evaluate the differences of the NDD, the corresponding unloaded navicular height pre stance (NHPS) and loaded navicular height during stance (NHS) of the different gait conditions.
Results: Ranges of NDD varied within walking speeds (4.19 - 5.99 mm), for running speeds (7.7 - 9.51 mm), and for NDST (1.56-1.1 mm), respectively. An increase in walking speed led to a significant decrease in NHPS (0.8 - 1.9 mm) and a subsequent decrease of NDD (0.5 - 1.8 mm; p .001). During increasing running velocity, NHS was significantly decreased by 0.8-1.6 mm leading to an increased NDD (1.2 - 1.8 mm,
p .001). Regarding walking and running at the same velocity, a large effect of gait style on NDD was shown, resulting in a larger NDD (3.52 ±1.88 mm) in 83% (p .001) when running. Compared to NDST, NDD was increased by 274% within walking 1.67 m s-1 and by 504% for running at 1.67 m s-1.
Conclusion(s): This study contributes to the understanding of the influence of gait velocity on the NDD. The change of gait style from walking to running at the same velocity had a large effect on the augmentation of the NDD. The magnitude of static ND differs greatly from the magnitude of the dynamic ND.
Implications: Because ND was affected by both, the dynamic condition and the gait style, the quasi-static ND from a sit-to-stand test is a poor predictor of dynamic foot function. Foot function should be evaluated task-specific and the dynamic ND could serve as a practical clinical tool. Nevetheless, values of unloaded NH and minimal NH during stance should be taken into account for the interpretation of dynamic ND measures.
Funding acknowledgements: The research was part of a project funded by the Swiss National Science Foundation (SNSF, project-No 140928).
Topic: Human movement analysis
Ethics approval: Ethics approval was graded as a low risk study and was given by the Cantonal Ethics Committee Berne (KEK-No. 052/15).
All authors, affiliations and abstracts have been published as submitted.
