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Exercise and Sport Sciences Reviews Jan 2021Understanding the physiological/mechanical mechanisms leading to skeletal muscle damage remains one of the challenges in muscle physiology. This review presents the... (Review)
Review
Understanding the physiological/mechanical mechanisms leading to skeletal muscle damage remains one of the challenges in muscle physiology. This review presents the functional, structural, and cellular consequences of electrically evoked submaximal isometric contractions that can elicit severe and localized skeletal muscle damage. Hypotheses related to underlying physiological and mechanical processes involved in severe and localized muscle damage also are discussed.
Topics: Electric Stimulation; Humans; Isometric Contraction; Muscle Contraction; Muscle, Skeletal
PubMed: 33122596
DOI: 10.1249/JES.0000000000000239 -
Langmuir : the ACS Journal of Surfaces... Dec 2022Biological motors function at the interface of biology, physics, and chemistry, and it remains unsettled what rules from which disciplines account for how these motors...
Biological motors function at the interface of biology, physics, and chemistry, and it remains unsettled what rules from which disciplines account for how these motors work. Myosin motors are enzymes that catalyze the hydrolysis of ATP through a mechanism involving a switch-like myosin structural change (a lever arm rotation) induced by actin binding that generates a small displacement of an actin filament. In muscle, individual myosin motors are widely assumed to function as molecular machines having mechanical properties that resemble those of muscle. In a fundamental departure from this perspective, here, I show that muscle more closely resembles a heat engine with mechanical properties that emerge from the thermodynamics of a myosin motor ensemble. The transformative impact of thermodynamics on our understanding of how a heat engine works guides a parallel transformation in our understanding of how muscle works. I consider the simplest possible model of force generation: a binary mechanical system. I develop the mechanics, energetics, and kinetics of this system and show that a single binding reaction generates force when muscle is held at a fixed length and performs work when muscle is allowed to shorten. This creates a network of thermodynamic binding pathways that resembles many of the characteristic mechanical and energetic behaviors of muscle including the muscle force-velocity relationship, heat output by shortening muscle, four phases of a muscle tension transient, spontaneous oscillatory contractions, and force redevelopment. Analogous to the thermodynamic (Carnot) cycle for a heat engine, isothermal and adiabatic binding and detachment reactions create a thermodynamic cycle for muscle that resembles cardiac pressure-volume loops (i.e., how the heart works). This paper provides an outline for how to re-interpret muscle mechanic data using thermodynamics - an ongoing effort that will continue providing novel insights into how muscle and molecular motors work.
Topics: Kinetics; Muscle Contraction; Myosins; Actins; Thermodynamics; Physics
PubMed: 36520019
DOI: 10.1021/acs.langmuir.2c01622 -
International Journal of Environmental... Aug 2022This paper aimed to compare the involuntary stimulated neuromuscular response of thigh muscles in top-level karate athletes and recreational groups.
BACKGROUND
This paper aimed to compare the involuntary stimulated neuromuscular response of thigh muscles in top-level karate athletes and recreational groups.
METHODS
The study included 13 male karate athletes (KAs) and 14 non-athlete male individuals (NAs). Tensiomyographic (TMG) measurements were obtained from the rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF) and semitendinosus (ST).
RESULTS
Statistically significant differences were observed between KAs and NAs in knee extensor/flexor delay time (Td), contraction time (Tc), total contraction time (Tct), maximal radial displacement of the muscle belly (Dm) and rate of muscle tension development (RMTD). On a group level, KA dominant-leg extensors and flexors and also non-dominant-leg knee flexors had significant differences when compared to NA. Tct is a TMG parameter in which the KAs and NAs differ the most in the case of the knee extensors, while flexor muscles differ the most in the RMTD parameter.
CONCLUSIONS
The lower Tct values indicate an improved ability of top-level karateka to make fast contractions of the agonist muscles. KAs' higher RMTD values suggest on strength characteristics needed in breaking actions of the antagonist muscles. Existence of contraction-relaxation-contraction neuromuscular pattern in the RF muscle suggests on implementation of training strategies that involves both rapid muscle contractions and relaxations.
Topics: Electromyography; Hamstring Muscles; Humans; Male; Martial Arts; Muscle Contraction; Muscle, Skeletal; Quadriceps Muscle
PubMed: 36011944
DOI: 10.3390/ijerph191610309 -
Journal of Bodywork and Movement... Jan 2020
Topics: Adaptation, Physiological; Biomechanical Phenomena; Biomedical Research; Elasticity; Humans; Muscle Contraction; Muscle Fibers, Skeletal; Muscle Relaxation; Osteopathic Medicine; Range of Motion, Articular
PubMed: 31987532
DOI: 10.1016/j.jbmt.2019.12.001 -
Physiological Reports May 2022Muscle co-contraction between the agonist and antagonist muscles often causes low energy efficiency or movement disturbances. Surface electromyography biofeedback...
Muscle co-contraction between the agonist and antagonist muscles often causes low energy efficiency or movement disturbances. Surface electromyography biofeedback (sEMG-BF) has been used to train muscle activation or relaxation but it is unknown whether sEMG-BF reduces muscle co-contraction. We hypothesized that auditory sEMG-BF improves muscle co-contraction. Our purpose was to investigate whether auditory sEMG-BF is effective in improving muscle co-contraction. Thirteen participants pedaled on a road bike using four different auditory sEMG-BF conditions. We measured the surface electromyography at the lower limb muscles. The vastus lateralis (VL) and the semitendinosus (ST) activities were individually transformed into different beep sounds. Four feedback conditions were no-feedback, VL feedback, ST feedback, and both VL and ST feedback. We compared the co-contraction index (COI) of the knee extensor-flexor muscles and the hip flexor-extensor muscles among the conditions. There were no significant differences in COIs among the conditions (p = 0.83 for the COI of the knee extensor-flexor; p = 0.32 for the COI of the hip flexor-extensor). To improve the muscle co-contraction by sEMG-BF, it may be necessary to convert muscle activation into a muscle co-contraction. We concluded that individual sEMG-BF does not immediately improve muscle co-contraction during pedaling.
Topics: Biofeedback, Psychology; Electromyography; Humans; Knee Joint; Muscle Contraction; Muscle, Skeletal
PubMed: 35611763
DOI: 10.14814/phy2.15288 -
Clinical Neurophysiology : Official... Jul 2023To understand the pathophysiology of myopathies by using muscle velocity recovery cycles (MVRC) and frequency ramp (RAMP) methodologies.
OBJECTIVE
To understand the pathophysiology of myopathies by using muscle velocity recovery cycles (MVRC) and frequency ramp (RAMP) methodologies.
METHODS
42 patients with quantitative electromyography (qEMG) and biopsy or genetic verified myopathy and 42 healthy controls were examined with qEMG, MVRC and RAMP, all recorded from the anterior tibial muscle.
RESULTS
There were significant differences in the motor unit potential (MUP) duration, the early and late supernormalities of the MVRC and the RAMP latencies in myopathy patients compared to controls (p < 0.05 apart from muscle relatively refractory period (MRRP)). When dividing into subgroups, the above-mentioned changes in MVRC and RAMP parameters were increased for the patients with non-inflammatory myopathy, while there were no significant changes in the group of patients with inflammatory myopathy.
CONCLUSIONS
The MVRC and RAMP parameters can discriminate between healthy controls and myopathy patients, more significantly for non-inflammatory myopathy. MVRC differences with normal MRRP in myopathy differs from other conditions with membrane depolarisation.
SIGNIFICANCE
MVCR and RAMP may have a potential in understanding disease pathophysiology in myopathies. The pathogenesis in non-inflammatory myopathy does not seem to be caused by a depolarisation of the resting membrane potential but rather by the change in sodium channels of the muscle membrane.
Topics: Humans; Muscle, Skeletal; Electromyography; Membrane Potentials; Muscular Diseases; Muscle Contraction
PubMed: 37148747
DOI: 10.1016/j.clinph.2023.04.001 -
Journal of Orthopaedic Research :... Sep 2022Mechanical stress is involved in the onset of sports-related enthesopathy. Although the amount of exercise undertaken is a recognized problem during disease onset,...
Mechanical stress is involved in the onset of sports-related enthesopathy. Although the amount of exercise undertaken is a recognized problem during disease onset, changes in muscle contraction type are also involved in the increase in mechanical stress during exercise. This study aimed to clarify the effects of increased mechanical stress associated with muscle contraction type and amount of exercise on enthesis. Twenty mice underwent treadmill exercise, and the muscle contraction type and overall load during exercise were adjusted by varying the angle and speed conditions. Histological analysis was used to the cross-sectional area of the muscle; area of the enthesis fibrocartilage (FC), and expression of inflammation-, degeneration-, and calcification-related factors in the FC area. In addition, the volume and structure of the bone and FC area were examined using microcomputer imaging. Molecular biological analysis was conducted to compare relative expression levels of inflammation and cytokine-related factors in tendons. The Overuse group, which increased the amount of exercise, showed no significant differences in parameters compared to the sedentary mice (Control group). The mice subjected to slow-speed downhill running (Misuse group) showed pathological changes compared to the Control and Overuse groups, despite the small amount of exercise. Thus, the enthesis FC area may be altered by local mechanical stress that would be increased by eccentric muscle contraction rather than by mechanical stress that increases with the overall amount of exercise. Clinical Significance: The muscle contraction type might be more involved in the onset of sports-related enthesopathy rather than the amount of exercise.
Topics: Animals; Enthesopathy; Inflammation; Mice; Muscle Contraction; Muscle, Skeletal; Running; Tendons
PubMed: 34862672
DOI: 10.1002/jor.25233 -
Aesthetic Surgery Journal Feb 2024Addressing neck contouring with surgical and nonsurgical aesthetic procedures includes understanding the origin of platysmal banding. A theory was postulated to explain...
BACKGROUND
Addressing neck contouring with surgical and nonsurgical aesthetic procedures includes understanding the origin of platysmal banding. A theory was postulated to explain this phenomenon by isometric vs isotonic muscular contraction patterns. However, no scientific proof had been provided to date for its correctness.
OBJECTIVES
The aim of this study was to confirm the correctness of the platysmal banding theory based on isometric vs isotonic muscular contractions.
METHODS
Eighty platysma muscles from 40 volunteers (15 males and 25 females) were investigated (mean age 41.8; SD 15.2 years; mean BMI of 22.2; SD 2.3 kg/m2). Real-time ultrasound imaging was utilized to measure the increase in local muscle thickness inside and outside of a platysmal band as well as platysma mobility.
RESULTS
Within a platysmal band, the local thickness of the muscle increases during muscular contractions by 0.33 mm (37.9%; P < .001). Outside of a platysmal band the thickness of the platysma muscle decreased by 0.13 mm (20.3%; P < .001). It was identified that within a platysmal band no gliding was detectable, whereas outside of a band an average muscle gliding of 2.76 mm was observed.
CONCLUSIONS
The results confirm the correctness of the isometric vs isotonic platysma muscle contraction pattern theory: isotonic muscle contraction (gliding without increase in tension and therefore in muscle thickness) vs isometric muscle contraction (no gliding but increase in tension and therefore in muscle thickness). These 2 types of contraction patterns occur within the platysma simultaneously and are an indicator for zones of adhesion in the neck to guide surgical and nonsurgical aesthetic procedures.
Topics: Male; Female; Humans; Adult; Superficial Musculoaponeurotic System; Muscle Contraction; Neck; Ultrasonography
PubMed: 37418617
DOI: 10.1093/asj/sjad216 -
Neuroscience Letters Apr 2020Endocannabinoids play important roles in regulating CNS synaptic function and peripheral metabolism, but cannabinoids can also act acutely to modulate contraction... (Review)
Review
Endocannabinoids play important roles in regulating CNS synaptic function and peripheral metabolism, but cannabinoids can also act acutely to modulate contraction strength in skeletal muscle. Nerve terminals and the skeletal muscle sarcolemma express components of the cannabinoid signaling system. Endocannabinoids, N-arachidonylethanolamine (anandamide, AEA) and 2-arachidonoyl-glycerol (2-AG), are produced by skeletal muscle. They may be involved in the acute regulation of neuromuscular transmission, by adjusting the parameters for quantal acetylcholine release from the motor nerve terminal. Downstream of neuromuscular transmission, cannabinoids may also act to limit the efficiency of excitation-contraction coupling. Improved understanding of the distinct signaling actions of particular cannabinoid compounds and their receptor/transduction systems will help advance our understanding of the role of endocannabinoids in skeletal muscle physiology. Cannabinoids might also offer the potential to develop new pharmacotherapeutics to treat neuromuscular disorders that affect muscle strength.
Topics: Animals; Cannabinoids; Humans; Motor Neurons; Muscle Contraction; Muscle, Skeletal; Signal Transduction; Synaptic Transmission
PubMed: 32156612
DOI: 10.1016/j.neulet.2020.134900 -
Journal of Muscle Research and Cell... Mar 2020The heart is an extraordinarily versatile pump, finely tuned to respond to a multitude of demands. Given the heart pumps without rest for decades its efficiency is... (Review)
Review
The heart is an extraordinarily versatile pump, finely tuned to respond to a multitude of demands. Given the heart pumps without rest for decades its efficiency is particularly relevant. Although many proteins in the heart are essential for viability, the non-essential components can attract numerous mutations which can cause disease, possibly through alterations in pumping efficiency. Of these, myosin binding protein C is strongly over-represented with ~ 40% of all known mutations in hypertrophic cardiomyopathy. Therefore, a complete understanding of its molecular function in the cardiac sarcomere is warranted. In this review, we revisit contemporary and classical literature to clarify both the current standing of this fast-moving field and frame future unresolved questions. To date, much effort has been directed at understanding MyBP-C function on either thick or thin filaments. Here we aim to focus questions on how MyBP-C functions at a molecular level in the context of both the thick and thin filaments together. A concept that emerges is MyBP-C acts to govern interactions on two levels; controlling myosin access to the thin filament by sequestration on the thick filament, and controlling the activation state and access of myosin to its binding sites on the thin filament. Such affects are achieved through directed interactions mediated by phosphorylation (of MyBP-C and other sarcomeric components) and calcium.
Topics: Carrier Proteins; Humans; Muscle Contraction
PubMed: 31960266
DOI: 10.1007/s10974-019-09567-1