Abstract

INTRODUCTION: Coupling in the distal foot may be due, at least in part, to the foot's windlass mechanism. This mechanism has been demonstrated passively, but its role in dynamic movement is still unclear. A systematic manipulation of metatarsophalangeal (MTP) mechanics may help determine to what extent distal foot coupling during dynamic and active movement is due to the windlass mechanism versus active muscle contractions or springlike ligaments. Furthermore, exploring the windlass mechanism in feet with varying foot structure may aid our understanding of the relationship between foot structure and foot function. PURPOSE: The overall purpose of this study is to investigate the kinematic and kinetic coupling between the MTP and midtarsal joints through a systematic manipulation of the windlass mechanism (achieved through methodical changes to MTP motion). Additionally, we aimed to explore the relationship between foot structure and the efficacy of the windlass mechanism during passive, active, and dynamic movement. METHODS: First, arch height and flexibility were measured using the Arch Height Index Measurement System. Next, participants performed four order-randomized conditions where MTP extension was isolated: 1) Seated Passive MTP Extension, 2) Seated Active MTP Extension, 3) Standing Passive MTP Extension, and 4) Standing Active MTP Extension. Lastly, participants performed three heel raise conditions that manipulated the starting position of the MTP joint: 1) Neutral: normal heel raise, 2) ToeExt: heel raise with the toes placed on an inclined surface of 30 degrees to put the MTP joint into extension, and 3) ToeFlex: heel raise with the toes placed on a declined surface of 30 degrees to put the MTP joint into flexion. All conditions were performed to a metronome of 40 beats per minute to control angular velocity. A kinetic multisegment foot model was created in Visual 3D software and used to calculate ankle, midtarsal, and MTP joint angles, moments, powers, and work. RESULTS: Kinematic coupling was approximately six times greater in the heel raise conditions compared to the isolated MTP extension conditions and suggests that the windlass mechanism only plays a small role in dynamic tasks. This is likely due to the greater involvement of active muscle contractions during heel raises. As the starting position of the MTP joint became increasingly extended, the amount of negative work at the MTP joint increased concomitantly with increased positive work done at the midtarsal joint, while net distal-to-hindfoot work remained unchanged. Our combined results suggest that there is substantial coupling within the distal foot, but this coupling is likely attributed to more than simple passive energy transfer from the windlass mechanism. Future investigations into the intrinsic foot muscle activation and biarticular muscle effects are likely needed to determine the source of this coupling. Lastly, the relationship between foot structure and function is still unclear and our results suggest that arch height or arch flexibility alone may not be adequate predictors of dynamic foot function.

Degree

MS

College and Department

Life Sciences

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2021-06-01

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd11843

Keywords

windlass mechanism, multisegment foot, foot energetics, heel raise

Language

english

Included in

Life Sciences Commons

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