scholarly journals Intrinsic foot muscles contribute to elastic energy storage and return in the human foot

2019 ◽  
Vol 126 (1) ◽  
pp. 231-238 ◽  
Author(s):  
Luke A. Kelly ◽  
Dominic J. Farris ◽  
Andrew G. Cresswell ◽  
Glen A. Lichtwark
Keyword(s):  
Central Nervous System ◽  
Energy Storage ◽  
Elastic Energy ◽  
Mechanical Energy ◽  
Plantar Aponeurosis ◽  
Human Foot ◽  
Intrinsic Foot Muscles ◽  
Flexor Digitorum Brevis ◽  
The Central Nervous System ◽  
Flexor Digitorum

The human foot is uniquely stiff to enable forward propulsion, yet also possesses sufficient elasticity to act as an energy store, recycling mechanical energy during locomotion. Historically, this dichotomous function has been attributed to the passive contribution of the plantar aponeurosis. However, recent evidence highlights the potential for muscles to modulate the energetic function of the foot actively. Here, we test the hypothesis that the central nervous system can actively control the foot’s energetic function, via activation of the muscles within the foot’s longitudinal arch. We used a custom-built loading apparatus to deliver cyclical loads to human feet in vivo, to deform the arch in a manner similar to that observed in locomotion. We recorded foot motion and forces, alongside muscle activation and ultrasound images from flexor digitorum brevis (FDB), an intrinsic foot muscle that spans the arch. When active, the FDB muscle fascicles contracted in an isometric manner, facilitating elastic energy storage in the tendon, in addition to the energy stored within the plantar aponeurosis. We propose that the human foot is akin to an active suspension system for the human body, with mechanical and energetic properties that can be actively controlled by the central nervous system. NEW & NOTEWORTHY The human foot is renowned for its ability to recycle mechanical energy during locomotion, contributing up to 17% of the energy required to power a stride. This mechanism has long been considered passive in nature, facilitated by the elastic ligaments within the arch of the foot. In this paper, we present the first direct evidence that the intrinsic foot muscles also contribute to elastic energy storage and return within the human foot. Isometric contraction of the flexor digitorum brevis muscle tissue facilitates tendon stretch and recoil during controlled loading of the foot. The significance of these muscles has been greatly debated by evolutionary biologists seeking to understand the origins of upright posture and gait, as well as applied and clinical scientists. The data we present here show a potential function for these muscles in contributing to the energetic function of the human foot.

scholarly journals The foot is more than a spring: human foot muscles perform work to adapt to the energetic requirements of locomotion

2019 ◽  
Vol 16 (150) ◽  
pp. 20180680 ◽  
Author(s):  
Ryan Riddick ◽  
Dominic J. Farris ◽  
Luke A. Kelly
Keyword(s):  
Net Energy ◽  
Centre Of Mass ◽  
Abductor Hallucis ◽  
Human Foot ◽  
Plantar Muscle ◽  
Elastic Mechanism ◽  
Intrinsic Foot Muscles ◽  
Flexor Digitorum Brevis ◽  
Energy Sink ◽  
Flexor Digitorum

The foot has been considered both as an elastic mechanism that increases the efficiency of locomotion by recycling energy, as well as an energy sink that helps stabilize movement by dissipating energy through contact with the ground. We measured the activity of two intrinsic foot muscles, flexor digitorum brevis (FDB) and abductor hallucis (AH), as well as the mechanical work performed by the foot as a whole and at a modelled plantar muscle–tendon unit (MTU) to test whether these passive mechanics are actively controlled during stepping. We found that the underlying passive visco-elasticity of the foot is modulated by the muscles of the foot, facilitating both dissipation and generation of energy depending on the mechanical requirements at the centre of mass (COM). Compared to level ground stepping, the foot dissipated and generated an additional –0.2 J kg −1 and 0.10 J kg −1 (both p < 0.001) when stepping down and up a 26 cm step respectively, corresponding to 21% and 10% of the additional net work performed by the leg on the COM. Of this compensation at the foot, the plantar MTU performed 30% and 89% of the work for step-downs and step-ups, respectively. This work occurred early in stance and late in stance for stepping down respectively, when the activation levels of FDB and AH were increased between 69 and 410% compared to level steps (all p < 0.001). These findings suggest that the energetic function of the foot is actively modulated by the intrinsic foot muscles and may play a significant role in movements requiring large changes in net energy such as stepping on stairs or inclines, accelerating, decelerating and jumping.

scholarly journals Shoes alter the spring-like function of the human foot during running

2016 ◽  
Vol 13 (119) ◽  
pp. 20160174 ◽  
Author(s):  
Luke A. Kelly ◽  
Glen A. Lichtwark ◽  
Dominic J. Farris ◽  
Andrew Cresswell
Keyword(s):  
Muscle Activation ◽  
Running Economy ◽  
Abductor Hallucis ◽  
Foot Kinematics ◽  
Human Foot ◽  
Running Shoes ◽  
Intrinsic Foot Muscles ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum ◽  
Intramuscular Electromyography

The capacity to store and return energy in legs and feet that behave like springs is crucial to human running economy. Recent comparisons of shod and barefoot running have led to suggestions that modern running shoes may actually impede leg and foot-spring function by reducing the contributions from the leg and foot musculature. Here we examined the effect of running shoes on foot longitudinal arch (LA) motion and activation of the intrinsic foot muscles. Participants ran on a force-instrumented treadmill with and without running shoes. We recorded foot kinematics and muscle activation of the intrinsic foot muscles using intramuscular electromyography. In contrast to previous assertions, we observed an increase in both the peak (flexor digitorum brevis +60%) and total stance muscle activation (flexor digitorum brevis +70% and abductor hallucis +53%) of the intrinsic foot muscles when running with shoes. Increased intrinsic muscle activation corresponded with a reduction in LA compression (−25%). We confirm that running shoes do indeed influence the mechanical function of the foot. However, our findings suggest that these mechanical adjustments are likely to have occurred as a result of increased neuromuscular output, rather than impaired control as previously speculated. We propose a theoretical model for foot–shoe interaction to explain these novel findings.

scholarly journals The Cross-Bridge Spring: Can Cool Muscles Store Elastic Energy?

Science ◽  
2013 ◽  
Vol 340 (6137) ◽  
pp. 1217-1220 ◽  
Author(s):  
N. T. George ◽  
T. C. Irving ◽  
C. D. Williams ◽  
T. L. Daniel
Keyword(s):  
Energy Storage ◽  
Elastic Energy ◽  
Molecular Motors ◽  
High Speed ◽  
Mechanical Energy ◽  
Elastic Strain Energy ◽  
Time Resolved ◽  
X Ray ◽  
Cross Bridge ◽  
Cross Bridges

Muscles not only generate force. They may act as springs, providing energy storage to drive locomotion. Although extensible myofilaments are implicated as sites of energy storage, we show that intramuscular temperature gradients may enable molecular motors (cross-bridges) to store elastic strain energy. By using time-resolved small-angle x-ray diffraction paired with in situ measurements of mechanical energy exchange in flight muscles of Manduca sexta, we produced high-speed movies of x-ray equatorial reflections, indicating cross-bridge association with myofilaments. A temperature gradient within the flight muscle leads to lower cross-bridge cycling in the cooler regions. Those cross-bridges could elastically return energy at the extrema of muscle lengthening and shortening, helping drive cyclic wing motions. These results suggest that cross-bridges can perform functions other than contraction, acting as molecular links for elastic energy storage.

Electromyographic Studies of the Human Foot: Experimental Approaches to Hominid Evolution

Foot & Ankle ◽  
1983 ◽  
Vol 3 (6) ◽  
pp. 391-407 ◽  
Author(s):  
Lori A. Reeser ◽  
Randall L. Susman ◽  
Jack T. Stern
Keyword(s):  
Hominid Evolution ◽  
Abductor Hallucis ◽  
Early Hominid ◽  
Human Foot ◽  
Flexor Digitorum Brevis ◽  
Experimental Approaches ◽  
Arch Support ◽  
Flexor Digitorum ◽  
Hominid Fossils ◽  
Electromyographic Investigation

Theories about the functions of the foot muscles have centered on their role in arch support. Previous anatomical and electromyographic studies (reviewed herein) have demonstrated that the arches are normally maintained by bones and ligaments. This study reports an electromyographic investigation of five foot muscles (flexor digito-rum longus, flexor digitorum brevis, flexor accessorius, abductor hallucis, and abductor digiti quinti) conducted on four humans. The three toe flexors act together to resist extension of the toes during the stance phase of locomotion. Despite the large flexor accessorius in humans, neither this muscle nor the flexor digitorum brevis are preferentially recruited over the flexor digitorum lon-gus for any normal posture or locomotion. The abductors affect the mediolateral distribution of pressure by positioning the forefoot. We suggest that the foot muscles play an important role in positioning of the forces on the foot in both posture and locomotion. Future electromyographic experiments on human and ape foot muscles in conjunction with detailed studies of early hominid fossils promise to elucidate the pathways of human locomotor evolution.

scholarly journals Active regulation of longitudinal arch compression and recoil during walking and running

2015 ◽  
Vol 12 (102) ◽  
pp. 20141076 ◽  
Author(s):  
Luke A. Kelly ◽  
Glen Lichtwark ◽  
Andrew G. Cresswell
Keyword(s):  
Stance Phase ◽  
Phase Changes ◽  
Gait Velocity ◽  
Force Transmission ◽  
Abductor Hallucis ◽  
Plantar Aponeurosis ◽  
Human Foot ◽  
Longitudinal Arch ◽  
Intrinsic Foot Muscles

The longitudinal arch (LA) of the human foot compresses and recoils in response to being cyclically loaded. This has typically been considered a passive process, however, it has recently been shown that the plantar intrinsic foot muscles have the capacity to actively assist in controlling LA motion. Here we tested the hypothesis that intrinsic foot muscles, abductor hallucis (AH), flexor digitorum brevis (FDB) and quadratus plantae (QP), actively lengthen and shorten during the stance phase of gait in response to loading of the foot. Nine participants walked at 1.25 m s −1 and ran at 2.78 and 3.89 m s −1 on a force-instrumented treadmill while foot and ankle kinematics were recorded according to a multisegment foot model. Muscle–tendon unit (MTU) lengths, determined from the foot kinematics, and intramuscular electromyography (EMG) signals were recorded from AH, FDB and QP. Peak EMG amplitude was determined during the stance phase for each participant at each gait velocity. All muscles underwent a process of slow active lengthening during LA compression, followed by a rapid shortening as the arch recoiled during the propulsive phase. Changes in MTU length and peak EMG increased significantly with increasing gait velocity for all muscles. This is the first in vivo evidence that the plantar intrinsic foot muscles function in parallel to the plantar aponeurosis, actively regulating the stiffness of the foot in response to the magnitude of forces encountered during locomotion. These muscles may therefore contribute to power absorption and generation at the foot, limit strain on the plantar aponeurosis and facilitate efficient foot ground force transmission.

The role of elastic energy storage mechanisms in swimming: an analysis of mantle elasticity in escape jetting in the squid, Loligo opalescens

1983 ◽  
Vol 61 (6) ◽  
pp. 1421-1431 ◽  
Author(s):  
John M. Gosline ◽  
Robert E. Shadwick
Keyword(s):  
Energy Storage ◽  
Elastic Energy ◽  
Mechanical Energy ◽  
Storage System ◽  
Collagen Fibre ◽  
Energy Storage System ◽  
Mantle Cavity ◽  
Loligo Opalescens ◽  
Locomotory Performance

Elastic energy storage mechanisms have been shown to improve locomotory performance and efficiency in many animals. In this paper we consider the role of elastic energy storage in jet locomotion of the squid, Loligo opalescens. The jet is powered by the contraction of circular muscles in the mantle. In addition, the mantle contains a collagen fibre based energy storage system (the mantle "spring") which captures some of the mechanical energy produced by the circular muscles and then releases this energy to power the refilling of the mantle cavity. The mantle spring is constructed so that it stores energy from the circular muscles only at a time in the jet cycle when, by virtue of the cylindrical geometry of the mantle, the circular muscles are unable, to apply their full mechanical output to the generation of hydrodynamic thrust. Thus the mantle spring increases the utilization of the circular muscles, and our analysis indicates that these muscles are used at virtually 100% of their potential through the entire jet. Presumably this increase in muscle utilization improves the locomotory performance of the squid. Other swimming animals, such as fish, may obtain similar benefits if elastic energy storage systems are constructed to capture energy at a time in the swimming cycle when muscles can not apply their full output to the generation of useful hydrodynamic forces.

Quantifying the Contributions of the Flexor Digitorum Brevis Muscle on Postural Stability

Motor Control ◽  
2015 ◽  
Vol 19 (3) ◽  
pp. 161-172 ◽  
Author(s):  
Liria Akie Okai ◽  
André Fabio Kohn
Keyword(s):  
Postural Control ◽  
Postural Stability ◽  
Center Of Pressure ◽  
Human Foot ◽  
Sustained Activity ◽  
Torque Generation ◽  
Flexor Digitorum Brevis ◽  
The Subject ◽  
Flexor Digitorum ◽  
Intrinsic Muscles

Surprisingly little attention has been devoted to the role played by the intrinsic muscles of the human foot. The aim of this study was to quantify the capabilities of the flexor digitorum brevis (FDB) muscle to contribute to upright postural control. The approaches consisted of analysis of the effects of FDB contraction elicited by external electrical stimulation and quantification of the magnitude of FDB torque generation. The results showed the FDB can produce significant changes in static posture by itself as shown by changes in the center of pressure. Moreover, the FDB contribution to counterbalance the gravity’s toppling force was estimated at around 14.5% of the total required active torque at the ankle to keep the subject from falling. A posteriori functional analysis during horizontal perturbations showed high and self-sustained activity of FDB. These results demonstrated that the FDB has a significant capability of contributing to postural control.

Plantar Fascial Spaces of the Foot and a Proposed Surgical Approach

Foot & Ankle ◽  
1980 ◽  
Vol 1 (1) ◽  
pp. 11-14 ◽  
Author(s):  
Robert D. Loeffler ◽  
Anthony Ballard
Keyword(s):  
Surgical Approach ◽  
Foot Injuries ◽  
Plantar Aponeurosis ◽  
The Third ◽  
Flexor Digitorum Brevis ◽  
Plantar Incision ◽  
Fascial Spaces ◽  
Flexor Digitorum ◽  
Adductor Hallucis ◽  
Neurovascular Bundles

This study identified five plantar fascial spaces of the foot. The first space lies superficial to the calcaneus, the second lies between the plantar aponeurosis and the flexor digitorum brevis, the third lies between the flexor digitorum brevis and the quadratus plantae, the fourth lies above the quadratus, and the fifth lies above the adductor hallucis. A plantar incision is proposed for exploration and drainage of foot injuries and infections. With this incision, the plantar neurovascular bundles, along with the five plantar spaces through which infection spreads, are visualized clearly. In our experience, the incision heals without a sensitive scar.

scholarly journals Morphological and mechanical properties of plantar fascia and intrinsic foot muscles in individuals with and without flat foot

2018 ◽  
Vol 26 (3) ◽  
pp. 230949901880248 ◽  
Author(s):  
Serkan Taş ◽  
Nezehat Özgül Ünlüer ◽  
Feza Korkusuz
Keyword(s):  
Mechanical Properties ◽  
Morphological Characteristics ◽  
Plantar Fascia ◽  
Abductor Hallucis ◽  
Flat Foot ◽  
Foot Posture ◽  
Intrinsic Foot Muscles ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum ◽  
Intrinsic Muscles

Purpose: Many musculoskeletal disorders are associated with over-pronated foot and decreased medial longitudinal arch (MLA) height. Foot intrinsic muscles and plantar fascia (PF) are the primary structures that support MLA. An important reason for the over-pronated foot and the reduction in the MLA height may be the morphological characteristics of the foot intrinsic muscles and PF as well as changes in their mechanical properties. The aim of the present study is to investigate the morphologic structure and mechanical properties of PF, flexor hallucis brevis (FHB), flexor digitorum brevis (FDB), and abductor hallucis (AbH) muscles in individuals with flat foot and to compare the results with those of healthy individuals. Methods: The study included 80 participants, 40 with flat foot and 40 with normal foot posture. The foot posture of the participants was assessed using the Foot Posture Index. PF, FHB, FDB, and AbH thickness and stiffness were measured with an ultrasonography device using a linear ultrasonography probe. Results: Individuals with flat foot had higher AbH thickness compared to individuals with normal foot posture ( p < 0.001), whereas both groups were similar in terms of PF ( p = 0.188), FHB ( p = 0.627), and FDB ( p = 0.212) thickness. Stiffness values of the assessed tissues were similar in both groups ( p > 0.05). Conclusion: AbH thickness was higher in individuals with flat foot; however, PF, FHB, and FDB thickness were similar in both groups. In addition, our results suggest that foot posture is not related to the stiffness of the assessed tissues.

scholarly journals Shorter heels are linked with greater elastic energy storage in the Achilles tendon

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. D. Foster ◽  
B. Block ◽  
F. Capobianco ◽  
J. T. Peabody ◽  
N. A. Puleo ◽  
...  
Keyword(s):  
Energy Storage ◽  
Achilles Tendon ◽  
Elastic Energy ◽  
Mechanical Energy ◽  
Running Economy ◽  
Triceps Surae ◽  
Morphological Data ◽  
Energetic Cost ◽  
Moment Arm ◽  
Moment Arms

AbstractPrevious research suggests that the moment arm of the m. triceps surae tendon (i.e., Achilles tendon), is positively correlated with the energetic cost of running. This relationship is derived from a model which predicts that shorter ankle moment arms place larger loads on the Achilles tendon, which should result in a greater amount of elastic energy storage and return. However, previous research has not empirically tested this assumed relationship. We test this hypothesis using an inverse dynamics approach in human subjects (n = 24) at speeds ranging from walking to sprinting. The spring function of the Achilles tendon was evaluated using specific net work, a metric of mechanical energy production versus absorption at a limb joint. We also combined kinematic and morphological data to directly estimate tendon stress and elastic energy storage. We find that moment arm length significantly determines the spring-like behavior of the Achilles tendon, as well as estimates of mass-specific tendon stress and elastic energy storage at running and sprinting speeds. Our results provide support for the relationship between short Achilles tendon moment arms and increased elastic energy storage, providing an empirical mechanical rationale for previous studies demonstrating a relationship between calcaneal length and running economy. We also demonstrate that speed and kinematics moderate tendon performance, suggesting a complex relationship between lower limb geometry and foot strike pattern.

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