scholarly journals Mechanics, modulation and modelling: how muscles actuate and control movement

2011 ◽  
Vol 366 (1570) ◽  
pp. 1463-1465 ◽  
Author(s):  
Timothy E. Higham ◽  
Andrew A. Biewener ◽  
Scott L. Delp
Keyword(s):  
Muscle Function ◽  
Animal Movement ◽  
Critical Role ◽  
Muscle Length ◽  
Neuromuscular Control ◽  
Clinical Aspects ◽  
Theme Issue ◽  
Recent Advances ◽  
Length Changes

Animal movement is often complex, unsteady and variable. The critical role of muscles in animal movement has captivated scientists for over 300 years. Despite this, emerging techniques and ideas are still shaping and advancing the field. For example, sonomicrometry and ultrasound techniques have enhanced our ability to quantify muscle length changes under in vivo conditions. Robotics and musculoskeletal models have benefited from improved computational tools and have enhanced our ability to understand muscle function in relation to movement by allowing one to simulate muscle–tendon dynamics under realistic conditions. The past decade, in particular, has seen a rapid advancement in technology and shifts in paradigms related to muscle function. In addition, there has been an increased focus on muscle function in relation to the complex locomotor behaviours, rather than relatively simple (and steady) behaviours. Thus, this Theme Issue will explore integrative aspects of muscle function in relation to diverse locomotor behaviours such as swimming, jumping, hopping, running, flying, moving over obstacles and transitioning between environments. Studies of walking and running have particular relevance to clinical aspects of human movement and sport. This Theme Issue includes contributions from scientists working on diverse taxa, ranging from humans to insects. In addition to contributions addressing locomotion in various taxa, several manuscripts will focus on recent advances in neuromuscular control and modulation during complex behaviours. Finally, some of the contributions address recent advances in biomechanical modelling and powered prostheses. We hope that our comprehensive and integrative Theme Issue will form the foundation for future work in the fields of neuromuscular mechanics and locomotion.

Tracheal smooth muscle mechanics in vivo

1990 ◽  
Vol 68 (1) ◽  
pp. 209-219 ◽  
Author(s):  
M. Okazawa ◽  
P. Pare ◽  
J. Road
Keyword(s):  
Smooth Muscle ◽  
Muscle Mechanics ◽  
Muscle Length ◽  
Base Line ◽  
Maximal Velocity ◽  
Velocity Of Shortening ◽  
Length Changes ◽  
Trachealis Muscle

We applied the technique of sonomicrometry to directly measure length changes of the trachealis muscle in vivo. Pairs of small 1-mm piezoelectric transducers were placed in parallel with the muscle fibers in the posterior tracheal wall in seven anesthetized dogs. Length changes were recorded during mechanical ventilation and during complete pressure-volume curves of the lung. The trachealis muscle showed spontaneous fluctuations in base-line length that disappeared after vagotomy. Before vagotomy passive pressure-length curves showed marked hysteresis and length changed by 18.5 +/- 13.2% (SD) resting length at functional residual capacity (LFRC) from FRC to total lung capacity (TLC) and by 28.2 +/- 16.2% LFRC from FRC to residual volume (RV). After vagotomy hysteresis decreased considerably and length now changed by 10.4 +/- 3.7% LFRC from FRC to TLC and by 32.5 +/- 14.6% LFRC from FRC to RV. Bilateral supramaximal vagal stimulation produced a mean maximal active shortening of 28.8 +/- 14.2% resting length at any lung volume (LR) and shortening decreased at lengths above FRC. The mean maximal velocity of shortening was 4.2 +/- 3.9% LR.S-1. We conclude that sonomicrometry may be used to record smooth muscle length in vivo. Vagal tone strongly influences passive length change. In vivo active shortening and velocity of shortening are less than in vitro, implying that there are significant loads impeding shortening in vivo.

scholarly journals Series elasticity facilitates safe plantar flexor muscle–tendon shock absorption during perturbed human hopping

2021 ◽  
Vol 288 (1947) ◽  
Author(s):  
Taylor J. M. Dick ◽  
Christofer J. Clemente ◽  
Laksh K. Punith ◽  
Gregory S. Sawicki
Keyword(s):  
Steady State ◽  
Neuromuscular Control ◽  
Ground Contact ◽  
Plantar Flexor ◽  
Plantar Flexors ◽  
Flexor Muscle ◽  
Unpredictable Environments ◽  
Co Activation ◽  
Length Changes

In our everyday lives, we negotiate complex and unpredictable environments. Yet, much of our knowledge regarding locomotion has come from studies conducted under steady-state conditions. We have previously shown that humans rely on the ankle joint to absorb energy and recover from perturbations; however, the muscle–tendon unit (MTU) behaviour and motor control strategies that accompany these joint-level responses are not yet understood. In this study, we determined how neuromuscular control and plantar flexor MTU dynamics are modulated to maintain stability during unexpected vertical perturbations. Participants performed steady-state hopping and, at an unknown time, we elicited an unexpected perturbation via rapid removal of a platform. In addition to kinematics and kinetics, we measured gastrocnemius and soleus muscle activations using electromyography and in vivo fascicle dynamics using B-mode ultrasound. Here, we show that an unexpected drop in ground height introduces an automatic phase shift in the timing of plantar flexor muscle activity relative to MTU length changes. This altered timing initiates a cascade of responses including increased MTU and fascicle length changes and increased muscle forces which, when taken together, enables the plantar flexors to effectively dissipate energy. Our results also show another mechanism, whereby increased co-activation of the plantar- and dorsiflexors enables shortening of the plantar flexor fascicles prior to ground contact. This co-activation improves the capacity of the plantar flexors to rapidly absorb energy upon ground contact, and may also aid in the avoidance of potentially damaging muscle strains. Our study provides novel insight into how humans alter their neural control to modulate in vivo muscle–tendon interaction dynamics in response to unexpected perturbations. These data provide essential insight to help guide design of lower-limb assistive devices that can perform within varied and unpredictable environments.

scholarly journals Magnetomicrometry

2021 ◽  
Vol 6 (57) ◽  
pp. eabg0656
Author(s):  
C. R. Taylor ◽  
S. S. Srinivasan ◽  
S. H. Yeon ◽  
M. K. O’Donnell ◽  
T. J. Roberts ◽  
...  
Keyword(s):  
Real Time ◽  
Magnetic Beads ◽  
Control Strategies ◽  
Muscle Length ◽  
Human Movement ◽  
Biological Tissues ◽  
Wearable Robots ◽  
Length Changes ◽  
Portable Sensor

We live in an era of wearable sensing, where our movement through the world can be continuously monitored by devices. Yet, we lack a portable sensor that can continuously monitor muscle, tendon, and bone motion, allowing us to monitor performance, deliver targeted rehabilitation, and provide intuitive, reflexive control over prostheses and exoskeletons. Here, we introduce a sensing modality, magnetomicrometry, that uses the relative positions of implanted magnetic beads to enable wireless tracking of tissue length changes. We demonstrate real-time muscle length tracking in an in vivo turkey model via chronically implanted magnetic beads while investigating accuracy, biocompatibility, and long-term implant stability. We anticipate that this tool will lay the groundwork for volitional control over wearable robots via real-time tracking of muscle lengths and speeds. Further, to inform future biomimetic control strategies, magnetomicrometry may also be used in the in vivo tracking of biological tissues to elucidate biomechanical principles of animal and human movement.

Muscle length changes during swimming in scup: sonomicrometry verifies the anatomical high-speed cine technique.

1996 ◽  
Vol 199 (2) ◽  
pp. 459-463 ◽  
Author(s):  
D J Coughlin ◽  
L Valdes ◽  
L C Rome
Keyword(s):  
High Speed ◽  
Muscle Length ◽  
Fish Muscles ◽  
Muscle Shortening ◽  
Red Muscle ◽  
Independent Technique ◽  
Loop Technique ◽  
Length Changes ◽  
Work Loop

Recent attempts to determine how fish muscles are used to power swimming have employed the work loop technique (driving isolated muscles using their in vivo strain and stimulation pattern). These muscle strains have in turn been determined from the anatomical high-speed cine technique. In this study, we used an independent technique, sonomicrometry, to attempt to verify these strain measurements and the conclusions based on them. We found that the strain records measured from sonomicrometry and the anatomical-cine techniques were very similar. The ratio of the strain measured from sonomicrometry to that from the anatomical-cine technique was remarkably close to unity (1.046 +/- 0.013, mean +/- S.E.M., N = 15, for transducers placed on the muscle surface and corrected for muscle depth, and 0.921 +/- 0.028, N = 8, in cases where the transducers were inserted to the average depth of the red muscle). These measurements also showed that red muscle shortening occurs simultaneously with local backbone curvature, unlike previous results which suggested that white muscle shortening during the escape response occurs prior to the change in local backbone curvature.

IN VIVO MUSCLE LENGTH CHANGES IN BUMBLEBEES AND THE IN VITRO EFFECTS ON WORK AND POWER

1993 ◽  
Vol 183 (1) ◽  
pp. 101-113 ◽  
Author(s):  
K. M. Gilmour ◽  
C. P. Ellington
Keyword(s):  
High Speed ◽  
Time Course ◽  
Second Harmonic ◽  
Muscle Length ◽  
Muscle Fibres ◽  
Bombus Lucorum ◽  
Length Changes ◽  
In Vitro Effects

The amplitude and time course of muscle length changes were examined in vivo in tethered, flying bumblebees Bombus lucorum. A ‘window’ was cut in the dorsal cuticle and aluminium particles were placed on the exposed dorsal longitudinal muscle fibres. Muscle oscillations were recorded using high-speed video and a high-magnification lens. The amplitude of muscle length changes was 1.9 % (s.d.=0.5 %, N=7), corresponding to the commonly quoted strain of 1–3 % for asynchronous muscle. Higher harmonics, particularly the second, were found in the muscle oscillations and in the wing movements. The second harmonic for wing movements was damped in comparison to that for muscle length changes, probably as a result of compliance in the thoracic linkage. Inclusion of the second harmonic in the driving signal for in vitro experiments on glycerinated fibres generally resulted in a decrease in the work and power, but a substantial increase was found for some fibres.

scholarly journals Computational modelling of muscle fibre operating ranges in the hindlimb of a small ground bird (Eudromia elegans), with implications for modelling locomotion in extinct species

2021 ◽  
Vol 17 (4) ◽  
pp. e1008843
Author(s):  
Peter J. Bishop ◽  
Krijn B. Michel ◽  
Antoine Falisse ◽  
Andrew R. Cuff ◽  
Vivian R. Allen ◽  
...  
Keyword(s):  
Muscle Function ◽  
Computational Models ◽  
Fibre Length ◽  
Computational Modelling ◽  
Length Change ◽  
Muscle Fibres ◽  
Extinct Species ◽  
Length Changes ◽  
Experimental Findings

The arrangement and physiology of muscle fibres can strongly influence musculoskeletal function and whole-organismal performance. However, experimental investigation of muscle function during in vivo activity is typically limited to relatively few muscles in a given system. Computational models and simulations of the musculoskeletal system can partly overcome these limitations, by exploring the dynamics of muscles, tendons and other tissues in a robust and quantitative fashion. Here, a high-fidelity, 26-degree-of-freedom musculoskeletal model was developed of the hindlimb of a small ground bird, the elegant-crested tinamou (Eudromia elegans, ~550 g), including all the major muscles of the limb (36 actuators per leg). The model was integrated with biplanar fluoroscopy (XROMM) and forceplate data for walking and running, where dynamic optimization was used to estimate muscle excitations and fibre length changes throughout both gaits. Following this, a series of static simulations over the total range of physiological limb postures were performed, to circumscribe the bounds of possible variation in fibre length. During gait, fibre lengths for all muscles remained between 0.5 to 1.21 times optimal fibre length, but operated mostly on the ascending limb and plateau of the active force-length curve, a result that parallels previous experimental findings for birds, humans and other species. However, the ranges of fibre length varied considerably among individual muscles, especially when considered across the total possible range of joint excursion. Net length change of muscle–tendon units was mostly less than optimal fibre length, sometimes markedly so, suggesting that approaches that use muscle–tendon length change to estimate optimal fibre length in extinct species are likely underestimating this important parameter for many muscles. The results of this study clarify and broaden understanding of muscle function in extant animals, and can help refine approaches used to study extinct species.

scholarly journals A blood–brain barrier overview on structure, function, impairment, and biomarkers of integrity

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
Hossam Kadry ◽  
Behnam Noorani ◽  
Luca Cucullo
Keyword(s):  
Blood Brain Barrier ◽  
Structural Integrity ◽  
Critical Role ◽  
Brain Barrier ◽  
Clinical Aspects ◽  
Advantages And Disadvantages ◽  
Blood Brain ◽  
The Brain

AbstractThe blood–brain barrier is playing a critical role in controlling the influx and efflux of biological substances essential for the brain’s metabolic activity as well as neuronal function. Thus, the functional and structural integrity of the BBB is pivotal to maintain the homeostasis of the brain microenvironment. The different cells and structures contributing to developing this barrier are summarized along with the different functions that BBB plays at the brain–blood interface. We also explained the role of shear stress in maintaining BBB integrity. Furthermore, we elaborated on the clinical aspects that correlate between BBB disruption and different neurological and pathological conditions. Finally, we discussed several biomarkers that can help to assess the BBB permeability and integrity in-vitro or in-vivo and briefly explain their advantages and disadvantages.

scholarly journals Leg muscles that mediate stability: mechanics and control of two distal extensor muscles during obstacle negotiation in the guinea fowl

2011 ◽  
Vol 366 (1570) ◽  
pp. 1580-1591 ◽  
Author(s):  
Monica A. Daley ◽  
Andrew A. Biewener
Keyword(s):  
Muscle Activation ◽  
Critical Role ◽  
Body Height ◽  
Neuromuscular Control ◽  
Guinea Fowl ◽  
Fascicle Length ◽  
Uneven Terrain ◽  
Leg Muscles ◽  
And Control

Here, we used an obstacle treadmill experiment to investigate the neuromuscular control of locomotion in uneven terrain. We measured in vivo function of two distal muscles of the guinea fowl, lateral gastrocnemius (LG) and digital flexor-IV (DF), during level running, and two uneven terrains, with 5 and 7 cm obstacles. Uneven terrain required one step onto an obstacle every four to five strides. We compared both perturbed and unperturbed strides in uneven terrain to level terrain. When the bird stepped onto an obstacle, the leg became crouched, both muscles acted at longer lengths and produced greater work, and body height increased. Muscle activation increased on obstacle strides in the LG, but not the DF, suggesting a greater reflex contribution to LG. In unperturbed strides in uneven terrain, swing pre-activation of DF increased by 5 per cent compared with level terrain, suggesting feed-forward tuning of leg impedance. Across conditions, the neuromechanical factors in work output differed between the two muscles, probably due to differences in muscle–tendon architecture. LG work depended primarily on fascicle length, whereas DF work depended on both length and velocity during loading. These distal muscles appear to play a critical role in stability by rapidly sensing and responding to altered leg–ground interaction.

scholarly journals Muscle spindles in human tibialis anterior encode muscle fascicle length changes

2017 ◽  
Vol 117 (4) ◽  
pp. 1489-1498 ◽  
Author(s):  
James Day ◽  
Leah R. Bent ◽  
Ingvars Birznieks ◽  
Vaughan G. Macefield ◽  
Andrew G. Cresswell
Keyword(s):  
Muscle Spindle ◽  
Tibialis Anterior ◽  
Tibialis Anterior Muscle ◽  
Muscle Length ◽  
Muscle Spindles ◽  
Muscle Spindle Afferents ◽  
Fascicle Length ◽  
Muscle Fascicle ◽  
Length Changes

Muscle spindles provide exquisitely sensitive proprioceptive information regarding joint position and movement. Through passively driven length changes in the muscle-tendon unit (MTU), muscle spindles detect joint rotations because of their in-parallel mechanical linkage to muscle fascicles. In human microneurography studies, muscle fascicles are assumed to follow the MTU and, as such, fascicle length is not measured in such studies. However, under certain mechanical conditions, compliant structures can act to decouple the fascicles, and, therefore, the spindles, from the MTU. Such decoupling may reduce the fidelity by which muscle spindles encode joint position and movement. The aim of the present study was to measure, for the first time, both the changes in firing of single muscle spindle afferents and changes in muscle fascicle length in vivo from the tibialis anterior muscle (TA) during passive rotations about the ankle. Unitary recordings were made from 15 muscle spindle afferents supplying TA via a microelectrode inserted into the common peroneal nerve. Ultrasonography was used to measure the length of an individual fascicle of TA. We saw a strong correlation between fascicle length and firing rate during passive ankle rotations of varying rates (0.1–0.5 Hz) and amplitudes (1–9°). In particular, we saw responses observed at relatively small changes in muscle length that highlight the sensitivity of the TA muscle to small length changes. This study is the first to measure spindle firing and fascicle dynamics in vivo and provides an experimental basis for further understanding the link between fascicle length, MTU length, and spindle firing patterns. NEW & NOTEWORTHY Muscle spindles are exquisitely sensitive to changes in muscle length, but recordings from human muscle spindle afferents are usually correlated with joint angle rather than muscle fascicle length. In this study, we monitored both muscle fascicle length and spindle firing from the human tibialis anterior muscle in vivo. Our findings are the first to measure these signals in vivo and provide an experimental basis for exploring this link further.

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