scholarly journals Stiffening the human foot with a biomimetic exotendon

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ryan C. Riddick ◽  
Dominic J. Farris ◽  
Nicholas A. T. Brown ◽  
Luke A. Kelly
Keyword(s):  
Energy Savings ◽  
Metabolic Energy ◽  
Medial Gastrocnemius ◽  
The Novel ◽  
Abductor Hallucis ◽  
Human Foot ◽  
Alternative Approach ◽  
In Series ◽  
Series Compliance ◽  
Footwear Design

AbstractShoes are generally designed protect the feet against repetitive collisions with the ground, often using thick viscoelastic midsoles to add in-series compliance under the human. Recent footwear design developments have shown that this approach may also produce metabolic energy savings. Here we test an alternative approach to modify the foot–ground interface by adding additional stiffness in parallel to the plantar aponeurosis, targeting the windlass mechanism. Stiffening the windlass mechanism by about 9% led to decreases in peak activation of the ankle plantarflexors soleus (~ 5%, p < 0.001) and medial gastrocnemius (~ 4%, p < 0.001), as well as a ~ 6% decrease in positive ankle work (p < 0.001) during fixed-frequency bilateral hopping (2.33 Hz). These results suggest that stiffening the foot may reduce cost in dynamic tasks primarily by reducing the effort required to plantarflex the ankle, since peak activation of the intrinsic foot muscle abductor hallucis was unchanged (p = 0.31). Because the novel exotendon design does not operate via the compression or bending of a bulky midsole, the device is light (55 g) and its profile is low enough that it can be worn within an existing shoe.

scholarly journals Intrinsic foot muscles have the capacity to control deformation of the longitudinal arch

2014 ◽  
Vol 11 (93) ◽  
pp. 20131188 ◽  
Author(s):  
Luke A. Kelly ◽  
Andrew G. Cresswell ◽  
Sebastien Racinais ◽  
Rodney Whiteley ◽  
Glen Lichtwark
Keyword(s):  
Electrical Stimulation ◽  
External Load ◽  
Energy Savings ◽  
Maximum Load ◽  
Metabolic Energy ◽  
Abductor Hallucis ◽  
Muscle Stretch ◽  
Human Foot ◽  
Longitudinal Arch ◽  
Intrinsic Foot Muscles

The human foot is characterized by a pronounced longitudinal arch (LA) that compresses and recoils in response to external load during locomotion, allowing for storage and return of elastic energy within the passive structures of the arch and contributing to metabolic energy savings. Here, we examine the potential for active muscular contribution to the biomechanics of arch deformation and recoil. We test the hypotheses that activation of the three largest plantar intrinsic foot muscles, abductor hallucis, flexor digitorum and quadratus plantae is associated with muscle stretch in response to external load on the foot and that activation of these muscles (via electrical stimulation) will generate sufficient force to counter the deformation of LA caused by the external load. We found that recruitment of the intrinsic foot muscles increased with increasing load, beyond specific load thresholds. Interestingly, LA deformation and muscle stretch plateaued towards the maximum load of 150% body weight, when muscle activity was greatest. Electrical stimulation of the plantar intrinsic muscles countered the deformation that occurred owing to the application of external load by reducing the length and increasing the height of the LA. These findings demonstrate that these muscles have the capacity to control foot posture and LA stiffness and may provide a buttressing effect during foot loading. This active arch stiffening mechanism may have important implications for how forces are transmitted during locomotion and postural activities as well as consequences for metabolic energy saving.

scholarly journals Additional in‐series compliance does not affect the length dependence of activation in rat medial gastrocnemius

2020 ◽  
Vol 105 (11) ◽  
pp. 1907-1917 ◽  
Author(s):  
Keenan B. MacDougall ◽  
Anders M. Kristensen ◽  
Brian R. MacIntosh
Keyword(s):  
Medial Gastrocnemius ◽  
Length Dependence ◽  
In Series ◽  
Series Compliance

scholarly journals Reports of the length dependence of fatigue are greatly exaggerated

2006 ◽  
Vol 101 (1) ◽  
pp. 23-29 ◽  
Author(s):  
M. B. MacNaughton ◽  
B. R. MacIntosh
Keyword(s):  
Muscle Length ◽  
Repetitive Stimulation ◽  
Double Pulse ◽  
Medial Gastrocnemius ◽  
Passive Force ◽  
Active Force ◽  
Rightward Shift ◽  
Length Dependence ◽  
Force Depression ◽  
In Series

Relative force depression associated with muscle fatigue is reported to be greater when assessed at short vs. long muscle lengths. This appears to be due to a rightward shift in the force-length relationship. This rightward shift may be caused by stretch of in-series structures, making sarcomere lengths shorter at any given muscle length. Submaximal force-length relationships (twitch, double pulse, 50 Hz) were evaluated before and after repetitive contractions (50 Hz, 300 ms, 1/s) in an in situ preparation of the rat medial gastrocnemius muscle. In some experiments, fascicle lengths were measured with sonomicrometry. Before repetitive stimulation, fascicle lengths were 11.3 ± 0.8, 12.8 ± 0.9, and 14.4 ± 1.2 mm at lengths corresponding to −3.6, 0, and 3.6 mm where 0 is a reference length that corresponds with maximal active force for double-pulse stimulation. After repetitive stimulation, there was no change in fascicle lengths; these lengths were 11.4 ± 0.8, 12.6 ± 0.9, and 14.2 ± 1.2 mm. The length dependence of fatigue was, therefore, not due to a stretch of in-series structures. Interestingly, the rightward shift that was evident when active force was calculated in the traditional way (subtraction of the passive force measured before contraction) was not seen when active force was calculated by subtracting the passive force that was associated with the fascicle length reached at the peak of the contraction. This calculation is based on the assumption that passive force decreases as the fascicles shorten during a fixed-end contraction. This alternative calculation revealed similar postfatigue absolute active force depression at all lengths. In relative terms, a length dependence of fatigue was still evident, but this was greatly diminished compared with that observed when active force was calculated with the traditional method.

scholarly journals Elastic energy savings and active energy cost in a simple model of running

2021 ◽  
Vol 17 (11) ◽  
pp. e1009608
Author(s):  
Ryan T. Schroeder ◽  
Arthur D. Kuo
Keyword(s):  
Elastic Energy ◽  
Energy Cost ◽  
Energy Savings ◽  
Mechanical Energy ◽  
Metabolic Cost ◽  
The Body ◽  
Metabolic Energy ◽  
Energetic Cost ◽  
Mass Model ◽  
Human Running

The energetic economy of running benefits from tendon and other tissues that store and return elastic energy, thus saving muscles from costly mechanical work. The classic “Spring-mass” computational model successfully explains the forces, displacements and mechanical power of running, as the outcome of dynamical interactions between the body center of mass and a purely elastic spring for the leg. However, the Spring-mass model does not include active muscles and cannot explain the metabolic energy cost of running, whether on level ground or on a slope. Here we add explicit actuation and dissipation to the Spring-mass model, and show how they explain substantial active (and thus costly) work during human running, and much of the associated energetic cost. Dissipation is modeled as modest energy losses (5% of total mechanical energy for running at 3 m s-1) from hysteresis and foot-ground collisions, that must be restored by active work each step. Even with substantial elastic energy return (59% of positive work, comparable to empirical observations), the active work could account for most of the metabolic cost of human running (about 68%, assuming human-like muscle efficiency). We also introduce a previously unappreciated energetic cost for rapid production of force, that helps explain the relatively smooth ground reaction forces of running, and why muscles might also actively perform negative work. With both work and rapid force costs, the model reproduces the energetics of human running at a range of speeds on level ground and on slopes. Although elastic return is key to energy savings, there are still losses that require restorative muscle work, which can cost substantial energy during running.

Developing a Cost-Effective and Functional Prosthetic Foot for Below Knee Amputees Using Topology Optimization and 3D Printing

2019 ◽  
Author(s):  
Hisham Kamel ◽  
Omar Harraz ◽  
Tamer Attia
Keyword(s):  
Topology Optimization ◽  
3D Printing ◽  
Experimental Tests ◽  
Cost Effective ◽  
Metabolic Energy ◽  
Release Mechanism ◽  
Normal Person ◽  
Fe Model ◽  
Prosthetic Foot ◽  
Human Foot

Abstract This paper presents the results of an investigative study on the development of an affordable and functional prosthetic foot for below knee amputees. A prototype was successfully manufactured using 3D printing technology. This continuously evolving technology enables the rapid production of prosthetics that are individually customized for each patient. Our prototype was developed after conducting a topology optimization study that interestingly converged to the shape of the biological human foot. Afterwards, a design was envisioned where a simple energy storage and release mechanism was implemented to replace the Achilles tendon, which minimizes the metabolic energy cost of walking. Our mechanism can successfully manage 70% of the energy compared to a normal person during each walking step. A finite element (FE) model of the prosthetic was developed and validated using experimental tests. Then, this FE model was used to confirm the safe operation of the prosthetic through simulating different loading scenarios according to the ISO standard. Our study clearly showed that customizable prosthetics could be produced at a fraction 1/60 of the cost of the commercially sold ones.

scholarly journals Drug Repositioning: New Approaches and Future Prospects for Life-Debilitating Diseases and the COVID-19 Pandemic Outbreak

Viruses ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1058
Author(s):  
Zheng Yao Low ◽  
Isra Ahmad Farouk ◽  
Sunil Kumar Lal
Keyword(s):  
Drug Development ◽  
De Novo ◽  
Drug Repositioning ◽  
Personalised Medicine ◽  
Technological Advancement ◽  
The Novel ◽  
Ongoing Research ◽  
Alternative Approach ◽  
Good Potential ◽  
Novel Drug

Traditionally, drug discovery utilises a de novo design approach, which requires high cost and many years of drug development before it reaches the market. Novel drug development does not always account for orphan diseases, which have low demand and hence low-profit margins for drug developers. Recently, drug repositioning has gained recognition as an alternative approach that explores new avenues for pre-existing commercially approved or rejected drugs to treat diseases aside from the intended ones. Drug repositioning results in lower overall developmental expenses and risk assessments, as the efficacy and safety of the original drug have already been well accessed and approved by regulatory authorities. The greatest advantage of drug repositioning is that it breathes new life into the novel, rare, orphan, and resistant diseases, such as Cushing’s syndrome, HIV infection, and pandemic outbreaks such as COVID-19. Repositioning existing drugs such as Hydroxychloroquine, Remdesivir, Ivermectin and Baricitinib shows good potential for COVID-19 treatment. This can crucially aid in resolving outbreaks in urgent times of need. This review discusses the past success in drug repositioning, the current technological advancement in the field, drug repositioning for personalised medicine and the ongoing research on newly emerging drugs under consideration for the COVID-19 treatment.

Rises in whole muscle passive tension of mammalian muscle after eccentric contractions at different lengths

2003 ◽  
Vol 95 (3) ◽  
pp. 1224-1234 ◽  
Author(s):  
N. P. Whitehead ◽  
D. L. Morgan ◽  
J. E. Gregory ◽  
U. Proske
Keyword(s):  
Isometric Tension ◽  
The Other ◽  
Medial Gastrocnemius ◽  
Eccentric Contractions ◽  
Passive Tension ◽  
Active Length ◽  
Before And After ◽  
Two Factors ◽  
In Series ◽  
Whole Muscle

This is a report of experiments carried out on the medial gastrocnemius muscle of the anesthetized cat, investigating the effects of eccentric contractions carried out at different muscle lengths on the passive and active length-tension relationships. In one series of experiments, the motor supply to the muscle was divided into three approximately equal parts; in the other, whole muscles were used. Fifty eccentric contractions were carried out over different regions of the active length-tension curve for each partial or whole muscle. Active and passive length-tension curves were measured before and after the eccentric contractions. When eccentric contractions were carried out at longer lengths, there was a larger shift of the optimum length for active tension in the direction of longer muscle lengths and a larger fall in peak isometric tension. Passive tension was higher immediately after the eccentric contractions, and if the muscle was left undisturbed for 40 min, it increased further to higher values, particularly after contractions at longer lengths. A series of 20 passive stretches of the same speed and amplitude and covering the same length range as the active stretches, reduced the passive tension which redeveloped over a subsequent 40-min period. It is hypothesized that there are two factors influencing the level of passive tension in a muscle after a series of eccentric contractions. One is injury contractures in damaged muscle fibers tending to raise passive tension; the other is the presence of disrupted sarcomeres in series with still-functioning sarcomeres tending to reduce it.

scholarly journals Modeling age-related changes in muscle-tendon dynamics during cyclical contractions in the rat gastrocnemius

2016 ◽  
Vol 121 (4) ◽  
pp. 1004-1012 ◽  
Author(s):  
Nicole Danos ◽  
Natalie C. Holt ◽  
Gregory S. Sawicki ◽  
Emanuel Azizi
Keyword(s):  
Elastic Energy ◽  
Metabolic Cost ◽  
Medial Gastrocnemius ◽  
Tissue Properties ◽  
Age Related ◽  
In Series ◽  
Force Velocity ◽  
Length Changes ◽  
Metabolic Performance ◽  
Age Related Changes

Efficient muscle-tendon performance during cyclical tasks is dependent on both active and passive mechanical tissue properties. Here we examine whether age-related changes in the properties of muscle-tendon units (MTUs) compromise their ability to do work and utilize elastic energy storage. We empirically quantified passive and active properties of the medial gastrocnemius muscle and material properties of the Achilles tendon in young (∼6 mo) and old (∼32 mo) rats. We then used these properties in computer simulations of a Hill-type muscle model operating in series with a Hookean spring. The modeled MTU was driven through sinusoidal length changes and activated at a phase that optimized muscle-tendon tuning to assess the relative contributions of active and passive elements to the force and work in each cycle. In physiologically realistic simulations where young and old MTUs started at similar passive forces and developed similar active forces, the capacity of old MTUs to store elastic energy and produce positive work was compromised. These results suggest that the observed increase in the metabolic cost of locomotion with aging may be in part due to the recruitment of additional muscles to compensate for the reduced work at the primary MTU. Furthermore, the age-related increases in passive stiffness coupled with a reduced active force capacity in the muscle can lead to shifts in the force-length and force-velocity operating range that may significantly impact mechanical and metabolic performance. Our study emphasizes the importance of the interplay between muscle and tendon mechanical properties in shaping MTU performance during cyclical contractions.

COVID-19 Illness: Mother–Baby Separation, Viruses, and Breastfeeding

2020 ◽  
pp. CLINLACT-D-20-00008
Author(s):  
Dena Duran ◽  
Jarold T. Johnston
Keyword(s):  
Case Reports ◽  
Economic Cost ◽  
Population Based ◽  
Early Summer ◽  
Direct Care ◽  
The Novel ◽  
Single Family ◽  
Alternative Approach ◽  
Novel Virus ◽  
Novel Coronavirus

ObjectivesSome hospitals have instituted separation of mothers and their newborn(s) when SARS-CoV-2 is suspected or confirmed in the mother. Limited data are available for SARS-CoV-2 vertical transmission, including studies on breast milk. This article looks at SARS CoV-2 case studies and data to date as well as prior pertinent research.MethodsInformal searches of PUBMED, CINAHL and Ovid Emcare were used to identify early reports of vertical transmissions of the novel Coronavirus, case reports, and population based reports of early evolving protocols and their outcomes. As this is a novel virus the authors used previously identified anti-infectivity and antiviral mechanisms of human milk on other similar viruses to guide analysis. Further this article reviewed the well established literature regarding the risks of undue infant separation which negatively affect nearly every aspect of infant and maternal health.ResultsInformal searches conducted in the spring and early summer of 2020 identified 14 early reports attempting to analyze the initial and evolving global response to SARS-CoV-2 and the effects of the virus on the maternal-infant dyad.ConclusionThe feasibility of single-family rooms and support for breastfeeding as an alternative approach that addresses many of the risks favorably and reduces economic cost, both in lifetime disease burden and direct care are discussed. Initial reports seem to indicate that immediate separation of the mother from her newborn is likely to increase the risk to both mother and infant.

scholarly journals Robust indexing for automatic data collection

2004 ◽  
Vol 37 (3) ◽  
pp. 399-409 ◽  
Author(s):  
Nicholas K. Sauter ◽  
Ralf W. Grosse-Kunstleve ◽  
Paul D. Adams
Keyword(s):  
Data Collection ◽  
High Throughput ◽  
Visual Inspection ◽  
The Novel ◽  
Automatic Data ◽  
X Ray ◽  
Alternative Approach ◽  
Automatic Data Collection ◽  
Diffraction Patterns ◽  
Improved Methods

Improved methods for indexing diffraction patterns from macromolecular crystals are presented. The novel procedures include a more robust way to verify the position of the incident X-ray beam on the detector, an algorithm to verify that the deduced lattice basis is consistent with the observations, and an alternative approach to identify the metric symmetry of the lattice. These methods help to correct failures commonly experienced during indexing, and increase the overall success rate of the process. Rapid indexing, without the need for visual inspection, will play an important role as beamlines at synchrotron sources prepare for high-throughput automation.

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