G5 Doctoral dissertation (article)
Neural and mechanical function of flexor hallucis longus at different walking speeds and in different footwear (2019)

Péter, A. (2019). Neural and mechanical function of flexor hallucis longus at different walking speeds and in different footwear [Doctoral dissertation]. Jyväskylän yliopisto. JYU dissertations, 178. http://urn.fi/URN:ISBN:978-951-39-8013-9

JYU authors or editors

Publication details

All authors or editors: Péter, Annamária

eISBN: 978-951-39-8013-9

Journal or series: JYU dissertations

eISSN: 2489-9003

Publication year: 2019

Number in series: 178

Number of pages in the book: 1 verkkoaineisto (71 sivua, 19 sivua useina numerointijaksoina, 21 numeroimatonta sivua)

Publisher: Jyväskylän yliopisto

Place of Publication: Jyväskylä

Publication country: Finland

Publication language: English

Persistent website address: http://urn.fi/URN:ISBN:978-951-39-8013-9

Publication open access: Openly available

Publication channel open access: Open Access channel

Abstract

Ankle plantar flexor muscles make a major contribution to body propulsion in walking. Besides the triceps surae, deep ankle plantar flexors such as flexor hallucis longus (FHL) may also contribute to this. However, FHL function has not been extensively examined in vivo. Therefore, the aim of this thesis was to examine the effects of walking speed on FHL electromyography (EMG) activity, fascicle behaviour, and forces measured under the hallux in shod walking. Agreement between surface and intramuscular EMG was also tested in shod walking at different speeds for FHL, soleus, gastrocnemii, and tibialis anterior. Furthermore, intramuscular EMG activity of FHL and triceps surae was examined in different footwear at self-selected walking speed. As expected, FHL was highly active in the push-off phase of walking, similar to other plantar flexors. Increased walking speed was associated with higher FHL EMG activity and higher forces under the hallux, indicating an increase in the relative importance of FHL at faster walking speeds. FHL muscle fascicles operated at a near-constant length throughout the stance phase of slow walking, and shortened at faster speeds. This is similar to the fascicle mechanics of medial gastrocnemius in walking, with which FHL also shares similar architectural properties. When surface and intramuscular EMG methods were compared, there was often (~60% of all cases) poor agreement between methods for FHL, likely due to the challenge of minimising cross-talk in this muscle. Walking in shoes at preferred speed required higher plantar flexor muscle activity for body propulsion than walking in flip-flops or barefoot in most individuals, however individual variability was substantial. In shod walking, peak muscle activity occurred at the same relative time in the contact phase between participants. This may be due to the fact that shoes limit individual-specific natural foot and ankle function, imposing a restrictive motion pattern. This thesis provides in vivo evidence for the important role of FHL in walking. Using intramuscular EMG and ultrasonography, future studies should examine FHL function in individuals with Achilles tendinopathy or flatfoot, which are associated with altered FHL morphology, and perhaps also altered muscle function.

Keywords: muscles; walking (motion); footwear; force; ankles; muscle cells; muscle activity; toes

Free keywords: plantar flexors; flexor hallucis longus; electromyography; fascicle bahaviour

Contributing organizations

Ministry reporting: Yes

Reporting Year: 2019