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Annual International Conference of the... Jul 2020Models of muscle contraction are typically based on a measured force-velocity relation embodied as Hill's contractile element [1]. Adopting a particular force-velocity...
Models of muscle contraction are typically based on a measured force-velocity relation embodied as Hill's contractile element [1]. Adopting a particular force-velocity relation dictates the muscle's mechanical properties. Dynamic crossbridge based models, such as Huxley's [2], typically focus on ultrastructural mechanics. This study adapts a dynamic lumped model of cardiac muscle contraction [3] for description of mouse soleus skeletal muscle. This compact, dynamic model exhibits the main features of skeletal muscle contraction with few assumptions. The main differences between cardiac and skeletal muscle dynamics are described. This approach gives one equation and set of parameters capable of modeling isometric and isotonic contractions, skeletal muscle's force-length relation, variations in contractility, and the force-velocity relation. This new constitutive equation may be useful for modeling striated muscle as part of larger biomechanical models.
Topics: Animals; Heart; Isotonic Contraction; Mice; Muscle, Skeletal; Myocardial Contraction
PubMed: 33018470
DOI: 10.1109/EMBC44109.2020.9176436 -
Journal of Electromyography and... Feb 2022The mechanomyogram (MMG) is a signal measured by various vibration sensors for slight vibrations induced by muscle contraction, and it reflects the muscle force during...
The mechanomyogram (MMG) is a signal measured by various vibration sensors for slight vibrations induced by muscle contraction, and it reflects the muscle force during electrically induced-contraction or until 60%-70% maximum voluntary contraction, so the MMG is considered an alternative and novel measurement tool for muscle strength. We simultaneously measured the MMG and muscle force in the gastrocnemius (GC), vastus intermedius (VI), and soleus (SOL) muscles of rats. The muscle force was measured by attaching a hook to the tendon using a load cell, and the MMG was measured using a charged-coupled device-type displacement sensor at the middle of the target muscle. The MMG-twitch waveform was very similar to that of the muscle force; however, the half relaxation time and relaxation time (10%), which are relaxation parameters, were prolonged compared to those of the muscle force. The MMG amplitude correlated with the muscle force. Since stimulation frequencies that are necessary to evoke tetanic progression have a significant correlation with the twitch parameter, there is a close relationship between twitch and tetanus in the MMG signal. Therefore, we suggest that the MMG, which is electrically induced and detected by a laser displacement sensor, may be an alternative tool for measuring muscle strength.
Topics: Animals; Isometric Contraction; Muscle Contraction; Muscle, Skeletal; Rats; Vibration
PubMed: 34999536
DOI: 10.1016/j.jelekin.2021.102627 -
European Journal of Applied Physiology Nov 2023
Topics: Humans; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Potassium
PubMed: 37728786
DOI: 10.1007/s00421-023-05313-1 -
Critical Reviews in Biomedical... 2022This paper presents a review of studies on the effects of local vibration training (LVT) on muscle strength along with the associated changes in neuromuscular and cell... (Review)
Review
This paper presents a review of studies on the effects of local vibration training (LVT) on muscle strength along with the associated changes in neuromuscular and cell dynamic responses. Application of local/direct vibration can significantly change the structural properties of muscle cell and can improve muscle strength. The improvement is largely dependent on vibration parameters such as amplitude and frequency. The results of 20 clinical studies reveal that electromyography (EMG) and maximal voluntary contraction (MVC) vary depending on vibration frequency, and studies using frequencies of 28-30 Hz reported greater increases in muscle activity in terms of EMG (rms) value and MVC data than the studies using higher frequencies. A greater muscle activity can be related to the recruitment of large motor units due to the application of local vibration. A greater increase in EMG (rms) values for biceps and triceps during extension than flexion under LVT suggests that types of muscles and their functions play an important role. Although a number of clinical trials and animal studies have demonstrated positive effects of vibration on muscle, an optimum training protocol has not been established. An attempt is made in this study to investigate the optimal LVT conditions on different muscles through review and analysis of published results in the literature pertaining to the changes in the neuromuscular activity. Directions for future research are discussed with regard to identifying optimal conditions for LVT and better understanding of the mechanisms associated with effects of vibration on muscles.
Topics: Electromyography; Muscle Cells; Muscle Contraction; Muscle Strength; Muscle, Skeletal; Vibration
PubMed: 35997107
DOI: 10.1615/CritRevBiomedEng.2022041625 -
Clinical and Experimental Pharmacology... Apr 2021Digestive inflammatory processes induce motility alterations associated with an increase in reactive oxygen species production, including monochloramine (NH Cl). The aim...
Digestive inflammatory processes induce motility alterations associated with an increase in reactive oxygen species production, including monochloramine (NH Cl). The aim of the study was to characterize the effects of the naturally occurring oxidant monochloramine in the guinea pig gallbladder. We used standard in vitro contractility technique to record guinea pig gallbladder strips contractions. NH Cl caused a concentration-dependent contraction which was reduced by inhibition of extracellular Ca influx and tyrosine kinase pathways. The PKC antagonist GF109203X also reduced the response but not after previous tyrosine kinase inhibition, suggesting that PKC is activated by tyrosine kinase activity. The NH Cl contractile effect was also reduced by inhibitors of mitogen-activated protein kinase (MAPK), nitric oxide synthase, phospholipase A2 and cyclooxygenase. In addition, NH Cl impaired the responses to CCK, tissue depolarization and electrical field stimulation. In conclusion, we present new evidence that monochloramine impairs not only the gallbladder response to CCK but also to membrane depolarization and nervous plexus stimulation, and that tyrosine kinase, PKC, MAPK and NO pathways are involved in the contractile direct effect of monochloramine.
Topics: Animals; Chloramines; Gallbladder; Guinea Pigs; Muscle Contraction
PubMed: 33352621
DOI: 10.1111/1440-1681.13453 -
Journal of Muscle Research and Cell... Mar 2020Tropomyosin is a dimer coiled-coil actin-binding protein. Adjacent tropomyosin molecules connect each other 'head-to-tail' via an overlap junction and form a continuous... (Review)
Review
Tropomyosin is a dimer coiled-coil actin-binding protein. Adjacent tropomyosin molecules connect each other 'head-to-tail' via an overlap junction and form a continuous strand that winds around an actin filament and controls the actin-myosin interaction. High cooperativity of muscle contraction largely depends on tropomyosin characteristics. Here we summarise experimental evidence that local peculiarities of tropomyosin structure have long-range effects and determine functional properties of the strand, including changes in its bending stiffness and interaction with actin and myosin. Point mutations and posttranslational modifications help to probe the roles of the conserved 'non-canonical' residues, clusters of stabilising and destabilising core residues, and core gap in tropomyosin function. The data suggest that tropomyosin structural lability including a diversity of homo- and heterodimers of different isoforms provide a balance of stiffness, flexibility, and strength of interaction with partner sarcomere proteins necessary for fine-tuning of Ca regulation in various types of striated muscles.
Topics: Humans; Muscle Contraction; Muscle, Striated; Tropomyosin
PubMed: 31535252
DOI: 10.1007/s10974-019-09552-8 -
Journal of Applied Physiology... Jun 2023Skeletal muscles bulge when they contract. These three-dimensional shape changes, coupled with fiber rotation, influence a muscle's mechanical performance by uncoupling...
Skeletal muscles bulge when they contract. These three-dimensional shape changes, coupled with fiber rotation, influence a muscle's mechanical performance by uncoupling fiber velocity from muscle belly velocity (i.e., gearing). Muscle shape change and gearing are likely mediated by the interaction between internal muscle properties and contractile forces. Muscles with greater stiffness and intermuscular fat, due to aging or disuse, may limit a muscle's ability to bulge in width, subsequently causing higher gearing. The aim of this study was to determine the influence of internal muscle properties on shape change, fiber rotation, and gearing in the medial (MG) and lateral gastrocnemii (LG) during isometric plantar flexion contractions. Multimodal imaging techniques were used to measure muscle shear modulus, intramuscular fat, and fat-corrected physiological cross-sectional area (PCSA) at rest, as well as synchronous muscle architecture changes during submaximal and maximal contractions in the MG and LG of 20 young (24 ± 3 yr) and 13 older (70 ± 4 yr) participants. Fat-corrected PCSA was positively associated with fiber rotation, gearing, and changes in thickness during submaximal contractions, but it was negatively associated with changes in thickness at maximal contractions. Muscle stiffness and intramuscular fat were related to muscle bulging and reduced fiber rotation, respectively, but only at high forces. Furthermore, the MG and LG had varied internal muscle properties, which may relate to the differing shape changes, fiber rotations, and gearing behaviors observed at each contraction level. These results indicate that internal muscle properties may play an important role in mediating in vivo muscle shape change and gearing, especially during high-force contractions. Here, we measured internal muscle properties in vivo to determine their influence on the varying shape change and gearing behaviors in the synergistic gastrocnemii muscles. These relationships have previously only been hypothesized or examined within isolated muscles during supramaximal contractions. Our results contribute to a more comprehensive understanding of the factors that influence a muscle's mechanical response to force with implications for preventing or treating muscle deficits associated with aging, disease, and disuse.
Topics: Humans; Muscle, Skeletal; Muscle Contraction; Mechanical Phenomena; Isometric Contraction; Aging
PubMed: 37167262
DOI: 10.1152/japplphysiol.00080.2023 -
Journal of Biomechanics Jul 2023Muscle energetics has expanded into the study of contractions that resemble in vivo muscle activity. A summary is provided of experiments of this type and what they have... (Review)
Review
Muscle energetics has expanded into the study of contractions that resemble in vivo muscle activity. A summary is provided of experiments of this type and what they have added to our understanding of muscle function and effects of compliant tendons, as well as the new questions raised about the efficiency of energy transduction in muscle.
Topics: Muscle Contraction; Tendons; Muscles; Muscle, Skeletal; Energy Metabolism
PubMed: 37327644
DOI: 10.1016/j.jbiomech.2023.111665 -
The Journal of Experimental Biology Apr 2023Skeletal muscle powers animal movement, making it an important determinant of fitness. The classic excitation-contraction coupling, sliding-filament and crossbridge... (Review)
Review
Skeletal muscle powers animal movement, making it an important determinant of fitness. The classic excitation-contraction coupling, sliding-filament and crossbridge theories are thought to describe the processes of muscle activation and the generation of force, work and power. Here, we review how the comparative, realistic muscle physiology typified by Journal of Experimental Biology over the last 100 years has supported and refuted these theories. We examine variation in the contraction rates and force-length and force-velocity relationships predicted by these theories across diverse muscles, and explore what has been learnt from the use of workloop and force-controlled techniques that attempt to replicate aspects of in vivo muscle function. We suggest inclusion of features of muscle contraction not explained by classic theories in our routine characterization of muscles, and the use of phylogenetic comparative methods to allow exploration of the effects of factors such as evolutionary history, ecology, behavior and size on muscle physiology and mechanics. We hope that these future directions will improve our understanding of the mechanisms of muscle contraction, allow us to better characterize the variation in muscle performance possible, and enable us to infer adaptation.
Topics: Animals; Physiology, Comparative; Phylogeny; Muscle, Skeletal; Muscle Contraction; Movement
PubMed: 36960844
DOI: 10.1242/jeb.245158 -
Applied Physiology, Nutrition, and... Apr 2020The transient increase in torque of an electrically evoked twitch following a voluntary contraction is called postactivation potentiation (PAP). Phosphorylation of... (Review)
Review
The transient increase in torque of an electrically evoked twitch following a voluntary contraction is called postactivation potentiation (PAP). Phosphorylation of myosin regulatory light chains is the most accepted mechanism explaining the enhanced electrically evoked twitch torque. While many authors attribute voluntary postactivation performance enhancement (PAPE) to the positive effects of PAP, few actually confirmed that contraction was indeed potentiated using electrical stimulation (twitch response) at the time that PAPE was measured. Thus, this review aims to investigate if increases in voluntary performance after a conditioning contraction (CC) are related to the PAP phenomenon. For this, studies that confirmed the presence of PAP through an evoked response after a voluntary CC and concurrently evaluated PAPE were reviewed. Some studies reported increases in PAPE when PAP reaches extremely high values. However, PAPE has also been reported when PAP was not present, and unchanged/diminished performance has been identified when PAP was present. This range of observations demonstrates that mechanisms of PAPE are different from mechanisms of PAP. These mechanisms of PAPE still need to be understood and those studying PAPE should not assume that regulatory light chain phosphorylation is the mechanism for such enhanced voluntary performance. The occurrence of PAP does not necessarily mean that the voluntary performance will be improved. Improvement in voluntary performance is sometimes observed when the PAP level reaches extremely high values. Other mechanisms may be more relevant than that for PAP in the manifestation of acute increases in performance following a conditioning contraction.
Topics: Athletic Performance; Electric Stimulation; Exercise; Humans; Muscle Contraction; Muscle, Skeletal
PubMed: 31557447
DOI: 10.1139/apnm-2019-0406