-
The Journal of General Physiology Sep 2022
Topics: Calcium; Excitation Contraction Coupling; Heart; Muscle Contraction; Muscle, Skeletal; Muscle, Smooth
PubMed: 35984377
DOI: 10.1085/jgp.202213244 -
International Journal of Molecular... Feb 2023The "motor unit" or the "muscle" has long been considered the quantal element in the control of movement. However, in recent years new research has proved the strong... (Review)
Review
The "motor unit" or the "muscle" has long been considered the quantal element in the control of movement. However, in recent years new research has proved the strong interaction between muscle fibers and intramuscular connective tissue, and between muscles and fasciae, suggesting that the muscles can no longer be considered the only elements that organize movement. In addition, innervation and vascularization of muscle is strongly connected with intramuscular connective tissue. This awareness induced Luigi Stecco, in 2002, to create a new term, the "myofascial unit", to describe the bilateral dependent relationship, both anatomical and functional, that occurs between fascia, muscle and accessory elements. The aim of this narrative review is to understand the scientific support for this new term, and whether it is actually correct to consider the myofascial unit the physiological basic element for peripheral motor control.
Topics: Muscle, Skeletal; Fascia; Connective Tissue; Muscle Fibers, Skeletal; Muscle Contraction
PubMed: 36901958
DOI: 10.3390/ijms24054527 -
Physiology (Bethesda, Md.) Nov 2019Muscle contraction is a three-dimensional process, as anyone who has observed a bulging muscle knows. Recent studies suggest that the three-dimensional nature of muscle... (Review)
Review
Muscle contraction is a three-dimensional process, as anyone who has observed a bulging muscle knows. Recent studies suggest that the three-dimensional nature of muscle contraction influences its mechanical output. Shape changes and radial forces appear to be important across scales of organization. Muscle architectural gearing is an emerging example of this process.
Topics: Animals; Biomechanical Phenomena; Humans; Muscle Contraction; Muscle, Skeletal
PubMed: 31577172
DOI: 10.1152/physiol.00023.2019 -
Nitric Oxide : Biology and Chemistry May 2022Nitric oxide (NO) is complex modulator of skeletal muscle contractile function, capable of increasing or decreasing force and power output depending on multiple factors.... (Review)
Review
Nitric oxide (NO) is complex modulator of skeletal muscle contractile function, capable of increasing or decreasing force and power output depending on multiple factors. This review explores the effects and potential mechanisms for modulation of skeletal muscle contractile function by NO, from pharmacological agents in isolated muscle preparations to dietary nitrate supplementation in humans and animals. Pharmacological manipulation in vitro suggests that NO signaling diminishes submaximal isometric force, whereas dietary manipulation in vivo suggest that NO enhances submaximal force. The bases for these different responses are unknown but could reflect dose-dependent effects. Maximal isometric force is unaffected by physiologically relevant levels of NO, which do not induce overt protein oxidation. Pharmacological and dietary manipulation of NO signaling enhances the maximal rate of isometric force development, unloaded shortening velocity, and peak power. We hypothesize that these effects are mediated by post-translational modifications of myofibrillar proteins that modulate thick filament regulation of contraction (e.g., mechanosensing and strain-dependence of cross-bridge kinetics). NO effects on contractile function appear to have some level of fiber type and sex-specificity. The mechanisms behind NO-mediated changes in skeletal muscle function need to be explored through proteomics analysis and advanced biophysical assays to advance the development of small molecules and open intriguing therapeutic and ergogenic possibilities for aging, disease, and athletic performance.
Topics: Animals; Muscle Contraction; Muscle, Skeletal; Nitrates; Nitric Oxide; Sarcomeres
PubMed: 35405336
DOI: 10.1016/j.niox.2022.04.001 -
The Journal of General Physiology Feb 2022Myofilaments and their associated proteins, which together constitute the sarcomeres, provide the molecular-level basis for contractile function in all muscle types. In... (Review)
Review
Myofilaments and their associated proteins, which together constitute the sarcomeres, provide the molecular-level basis for contractile function in all muscle types. In intact muscle, sarcomere-level contraction is strongly coupled to other cellular subsystems, in particular the sarcolemmal membrane. Skinned muscle preparations (where the sarcolemma has been removed or permeabilized) are an experimental system designed to probe contractile mechanisms independently of the sarcolemma. Over the last few decades, experiments performed using permeabilized preparations have been invaluable for clarifying the understanding of contractile mechanisms in both skeletal and cardiac muscle. Today, the technique is increasingly harnessed for preclinical and/or pharmacological studies that seek to understand how interventions will impact intact muscle contraction. In this context, intrinsic functional and structural differences between skinned and intact muscle pose a major interpretational challenge. This review first surveys measurements that highlight these differences in terms of the sarcomere structure, passive and active tension generation, and calcium dependence. We then highlight the main practical challenges and caveats faced by experimentalists seeking to emulate the physiological conditions of intact muscle. Gaining an awareness of these complexities is essential for putting experiments in due perspective.
Topics: Calcium; Muscle Contraction; Myocardial Contraction; Myocardium; Myofibrils; Sarcomeres
PubMed: 35045156
DOI: 10.1085/jgp.202112990 -
Pflugers Archiv : European Journal of... Mar 202214-3-3 proteins (14-3-3 s) are a family of highly conserved proteins that regulate many cellular processes in eukaryotes by interacting with a diverse array of client... (Review)
Review
14-3-3 proteins (14-3-3 s) are a family of highly conserved proteins that regulate many cellular processes in eukaryotes by interacting with a diverse array of client proteins. The 14-3-3 proteins have been implicated in several disease states and previous reviews have condensed the literature with respect to their structure, function, and the regulation of different cellular processes. This review focuses on the growing body of literature exploring the important role 14-3-3 proteins appear to play in regulating the biochemical and biophysical events associated with excitation-contraction coupling (ECC) in muscle. It presents both a timely and unique analysis that seeks to unite studies emphasizing the identification and diversity of 14-3-3 protein function and client protein interactions, as modulators of muscle contraction. It also highlights ideas within these two well-established but intersecting fields that support further investigation with respect to the mechanistic actions of 14-3-3 proteins in the modulation of force generation in muscle.
Topics: 14-3-3 Proteins; Calcium; Excitation Contraction Coupling; Humans; Muscle Contraction; Muscle, Skeletal
PubMed: 34820713
DOI: 10.1007/s00424-021-02635-x -
Journal of Applied Physiology... Mar 2022Ventilatory response to sustained isocapnic hypoxia in adult humans and other mammals is characterized by a biphasic pattern, with attenuation of neuromotor output to...
Ventilatory response to sustained isocapnic hypoxia in adult humans and other mammals is characterized by a biphasic pattern, with attenuation of neuromotor output to the diaphragm. However, there is no a priori reason that hypoxia-mediated attenuation of respiratory drive would be a common event among other respiratory muscles. At present, little is known about the function of the chest wall muscles during sustained hypoxia. As an obligatory inspiratory muscle with potential to act as a surrogate for neural drive to the relatively inaccessible costal diaphragm, parasternal intercostal has gained interest clinically: its function during a sustained hypoxic insult, as may occur in respiratory failure, warrants investigation. Therefore, in 11 chronically instrumented awake canines, we simultaneously recorded muscle length and shortening and electromyogram (EMG) activity of the parasternal chest wall inspiratory muscle, along with breathing pattern, during moderate levels of sustained isocapnic hypoxia lasting 20-25 min (mean 80 ± 2% oximeter oxygen saturation). Phasic inspiratory shortening and EMG activity of the parasternal intercostal were observed throughout room air and hypoxic ventilation in all animals. Temporal changes in parasternal intercostal shortening tracked the biphasic changes in ventilation during sustained hypoxia. Mean shortening and EMG activity of parasternal intercostal muscle increased significantly with initial hypoxia ( < 0.01) and then markedly declined with constant hypoxia ( < 0.05). We conclude that attenuation of central neural respiratory drive extends to the primary chest wall inspiratory muscle, the parasternal intercostal, during sustained hypoxia, thus directly contributing to biphasic changes in ventilation. With the potential to act as a surrogate for the generally inaccessible costal diaphragm, parasternal intercostal has gained great interest clinically as a muscle to monitor neural drive and function in respiratory disease. This study demonstrates for the first time the impact of sustained hypoxia on neural activation and mechanical contraction of the parasternal intercostals. Parasternal intercostals reveal a biphasic action during the time-dependent hypoxic response, with a transient increase in shortening and EMG activity with acute hypoxia followed by a progressive decline when hypoxia is sustained.
Topics: Animals; Diaphragm; Dogs; Electromyography; Humans; Hypoxia; Intercostal Muscles; Muscle Contraction; Respiration
PubMed: 35112930
DOI: 10.1152/japplphysiol.00771.2020 -
Proceedings of the National Academy of... Mar 2022Stable precision grips using the fingertips are a cornerstone of human hand dexterity. However, our fingers become unstable sometimes and snap into a hyperextended...
Stable precision grips using the fingertips are a cornerstone of human hand dexterity. However, our fingers become unstable sometimes and snap into a hyperextended posture. This is because multilink mechanisms like our fingers can buckle under tip forces. Suppressing this instability is crucial for hand dexterity, but how the neuromuscular system does so is unknown. Here we show that people rely on the stiffness from muscle contraction for finger stability. We measured buckling time constants of 50 ms or less during maximal force application with the index finger—quicker than feedback latencies—which suggests that muscle-induced stiffness may underlie stability. However, a biomechanical model of the finger predicts that muscle-induced stiffness cannot stabilize at maximal force unless we add springs to stiffen the joints or people reduce their force to enable cocontraction. We tested this prediction in 38 volunteers. Upon adding stiffness, maximal force increased by 34 ± 3%, and muscle electromyography readings were 21 ± 3% higher for the finger flexors (mean ± SE). Muscle recordings and mathematical modeling show that adding stiffness offloads the demand for muscle cocontraction, thus freeing up muscle capacity for fingertip force. Hence, people refrain from applying truly maximal force unless an external stabilizing stiffness allows their muscles to apply higher force without losing stability. But more stiffness is not always better. Stiff fingers would affect the ability to adapt passively to complex object geometries and precisely regulate force. Thus, our results show how hand function arises from neurally tuned muscle stiffness that balances finger stability with compliance.
Topics: Biomechanical Phenomena; Electromyography; Fingers; Hand Strength; Humans; Muscle Contraction; Muscle, Skeletal; Posture
PubMed: 35294291
DOI: 10.1073/pnas.2122903119 -
Biomechanics and Modeling in... Feb 2023A FLIP device gives cross-sectional area along the length of the esophagus and one pressure measurement, both as a function of time. Deducing mechanical properties of...
A FLIP device gives cross-sectional area along the length of the esophagus and one pressure measurement, both as a function of time. Deducing mechanical properties of the esophagus including wall material properties, contraction strength, and wall relaxation from these data are a challenging inverse problem. Knowing mechanical properties can change how clinical decisions are made because of its potential for in-vivo mechanistic insights. To obtain such information, we conducted a parametric study to identify peristaltic regimes by using a 1D model of peristaltic flow through an elastic tube closed on both ends and also applied it to interpret clinical data. The results gave insightful information about the effect of tube stiffness, fluid/bolus density and contraction strength on the resulting esophagus shape through quantitive representations of the peristaltic regimes. Our analysis also revealed the mechanics of the opening of the contraction area as a function of bolus flow resistance. Lastly, we concluded that peristaltic driven flow displays three modes of peristaltic geometries, but all physiologically relevant flows fall into two peristaltic regimes characterized by a tight contraction.
Topics: Deglutition; Muscle Contraction; Esophagus; Peristalsis; Body Fluids
PubMed: 36352039
DOI: 10.1007/s10237-022-01625-x -
Sensors (Basel, Switzerland) Mar 2022Complications related to neuromuscular blockade (NMB) could occur during anesthesia induction, maintenance, and emergency. It is recommended that neuromuscular... (Review)
Review
Complications related to neuromuscular blockade (NMB) could occur during anesthesia induction, maintenance, and emergency. It is recommended that neuromuscular monitoring techniques be utilized perioperatively to avoid adverse outcomes. However, current neuromuscular monitoring methods possess different shortcomings. They are cumbersome to use, susceptible to disturbances, and have limited alternative monitoring sites. Phonomyography (PMG) monitoring based on the acoustic signals yielded by skeletal muscle contraction is emerging as an interesting and innovative method. This technique is characterized by its convenience, stable signal quality, and multimuscle recording ability and shows great potential in the application field. This review summarizes the progression of PMG on perioperative neuromuscular monitoring chronologically and presents the merits, demerits, and challenges of PMG-based equipment, aiming at underscoring the potential of PMG-based apparatuses for neuromuscular monitoring.
Topics: Electric Stimulation; Muscle Contraction; Myography; Neuromuscular Blockade; Neuromuscular Monitoring
PubMed: 35408063
DOI: 10.3390/s22072448