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Aging Aug 2023The loss of skeletal muscle strength mid-life in females is associated with the decline of estrogen. Here, we questioned how estrogen deficiency might impact the overall...
The loss of skeletal muscle strength mid-life in females is associated with the decline of estrogen. Here, we questioned how estrogen deficiency might impact the overall skeletal muscle phosphoproteome after contraction, as force production induces phosphorylation of several muscle proteins. Phosphoproteomic analyses of the tibialis anterior muscle after contraction in two mouse models of estrogen deficiency, ovariectomy (Ovariectomized (Ovx) vs. Sham) and natural aging-induced ovarian senescence (Older Adult (OA) vs. Young Adult (YA)), identified a total of 2,593 and 3,507 phosphopeptides in Ovx/Sham and OA/YA datasets, respectively. Further analysis of estrogen deficiency-associated proteins and phosphosites identified 66 proteins and 21 phosphosites from both datasets. Of these, 4 estrogen deficiency-associated proteins and 4 estrogen deficiency-associated phosphosites were significant and differentially phosphorylated or regulated, respectively. Comparative analyses between Ovx/Sham and OA/YA using Ingenuity Pathway Analysis (IPA) found parallel patterns of inhibition and activation across IPA-defined canonical signaling pathways and physiological functional analysis, which were similarly observed in downstream GO, KEGG, and Reactome pathway overrepresentation analysis pertaining to muscle structural integrity and contraction, including AMPK and calcium signaling. IPA Upstream regulator analysis identified MAPK1 and PRKACA as candidate kinases and calcineurin as a candidate phosphatase sensitive to estrogen. Our findings highlight key molecular signatures and pathways in contracted muscle suggesting that the similarities identified across both datasets could elucidate molecular mechanisms that may contribute to skeletal muscle strength loss due to estrogen deficiency.
Topics: Mice; Female; Animals; Humans; Muscle, Skeletal; Estrogens; Muscle Contraction; Aging; Proteins; Ovariectomy
PubMed: 37580837
DOI: 10.18632/aging.204959 -
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 -
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 Animal Science Aug 2022Skeletal muscle hypertrophy is a culmination of catabolic and anabolic processes that are interwoven into major metabolic pathways, and as such modulation of skeletal...
Skeletal muscle hypertrophy is a culmination of catabolic and anabolic processes that are interwoven into major metabolic pathways, and as such modulation of skeletal muscle metabolism may have implications on animal growth efficiency. Muscle is composed of a heterogeneous population of muscle fibers that can be classified by metabolism (oxidative or glycolytic) and contractile speed (slow or fast). Although slow fibers (type I) rely heavily on oxidative metabolism, presumably to fuel long or continuous bouts of work, fast fibers (type IIa, IIx, and IIb) vary in their metabolic capability and can range from having a high oxidative capacity to a high glycolytic capacity. The plasticity of muscle permits continuous adaptations to changing intrinsic and extrinsic stimuli that can shift the classification of muscle fibers, which has implications on fiber size, nutrient utilization, and protein turnover rate. The purpose of this paper is to summarize the major metabolic pathways in skeletal muscle and the associated regulatory pathways.
Topics: Adaptation, Physiological; Animals; Muscle Contraction; Muscle Fibers, Skeletal; Muscle, Skeletal; Oxidation-Reduction
PubMed: 35908794
DOI: 10.1093/jas/skac035 -
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 -
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 -
Faster triceps surae muscle cyclic contractions alter muscle activity and whole body metabolic rate.Journal of Applied Physiology... Feb 2023Hundred years ago, Fenn demonstrated that when a muscle shortens faster, its energy liberation increases. Fenn's results were the first of many that led to the general...
Hundred years ago, Fenn demonstrated that when a muscle shortens faster, its energy liberation increases. Fenn's results were the first of many that led to the general understanding that isometric muscle contractions are energetically cheaper than concentric contractions. However, this evidence is still primarily based on single fiber or isolated (ex vivo) muscle studies and it remains unknown whether this translates to whole body metabolic rate. In this study, we specifically changed the contraction velocity of the ankle plantar flexors and quantified the effects on triceps surae muscle activity and whole body metabolic rate during cyclic plantar flexion (PF) contractions. Fifteen participants performed submaximal ankle plantar flexions (∼1/3 s activation and ∼2/3 s relaxation) on a dynamometer at three different ankle angular velocities: isometric (10° PF), isokinetic at 30°/s (5-15° PF), and isokinetic at 60°/s (0-20° PF) while target torque (25% MVC) and cycle frequency were kept constant. In addition, to directly determine the effect of ankle angular velocity on muscle kinematics we collected gastrocnemius medialis muscle fascicle ultrasound data. As expected, increasing ankle angular velocity increased gastrocnemius medialis muscle fascicle contraction velocity and positive mechanical work ( < 0.01), increased mean and peak triceps surae muscle activity ( < 0.01), and considerably increased net whole body metabolic rate ( < 0.01). Interestingly, the increase in triceps surae muscle activity with fast ankle angular velocities was most pronounced in the gastrocnemius lateralis ( < 0.05). Overall, our results support the original findings from Fenn in 1923 and we demonstrated that greater triceps surae muscle contraction velocities translate to increased whole body metabolic rate. Single muscle fiber studies or research on isolated (ex vivo) muscles demonstrated that faster concentric muscle contractions yield increased energy consumption. Here we translated this knowledge to muscle activation and whole body metabolic rate. Increasing ankle angular velocity increased triceps surae contraction velocity and mechanical work, increasing triceps surae muscle activity and substantially elevating whole body metabolic rate. Additionally, we demonstrated that triceps surae muscle activation strategy depends on the mechanical demands of the task.
Topics: Humans; Muscle, Skeletal; Muscle Contraction; Isometric Contraction; Leg; Ankle Joint
PubMed: 36603047
DOI: 10.1152/japplphysiol.00575.2022 -
The Journal of Physiology Apr 2023Skeletal muscle is the most abundant component of the mature mammalian phenotype. Designed to generate contractile force and movement, skeletal muscle is crucial for... (Review)
Review
Skeletal muscle is the most abundant component of the mature mammalian phenotype. Designed to generate contractile force and movement, skeletal muscle is crucial for organism health, function and development. One of the great interests for muscle biologists is in understanding how skeletal muscle adapts during periods of stress and stimuli, such as disease, disuse and ageing. To this end, genomic-based experimental and analytical approaches offer one of the most powerful approaches for comprehensively mapping the molecular paradigms that regulate skeletal muscle. With the power, applicability, and robustness of 'omic' technologies continually being developed, we are now in a position to investigate these molecular mechanisms in skeletal muscle to an unprecedented level of accuracy and precision, heralding the dawn of a new era of functional genomics in the field of muscle physiology.
Topics: Animals; Genomics; Muscle, Skeletal; Muscle Contraction; Aging; Phenotype; Mammals
PubMed: 36829294
DOI: 10.1113/JP284206 -
International Urogynecology Journal Jun 2022The aim of this study is to develop and validate a new integral parameter, the Biomechanical Integrity score (BI-score), for the characterization of the female pelvic... (Observational Study)
Observational Study
INTRODUCTION AND HYPOTHESIS
The aim of this study is to develop and validate a new integral parameter, the Biomechanical Integrity score (BI-score), for the characterization of the female pelvic floor.
METHODS
A total of 253 subjects with normal and pelvic organ prolapse (POP) conditions were included in the multi-site observational, case-control study; 125 subjects had normal pelvic floor conditions, and 128 subjects had POP stage II or higher. A Vaginal Tactile Imager (VTI) was used to acquire and automatically calculate 52 biomechanical parameters for eight VTI test procedures (probe insertion, elevation, rotation, Valsalva maneuver, voluntary muscle contractions in two planes, relaxation, and reflex contraction). Statistical methods were applied (t-test, correlation) to identify the VTI parameters sensitive to the pelvic conditions.
RESULTS
Twenty-six parameters were identified as statistically sensitive to POP development. They were subdivided into five groups to characterize (1) tissue elasticity, (2) pelvic support, (3) pelvic muscle contraction, (4) involuntary muscle relaxation, and (5) pelvic muscle mobility. Every parameter was transformed to its standard deviation units against the patient age similar to T-score for bone density. Linear combinations with specified weights led to the composition of five component parameters for groups (1)-(5) and the BI-score in standard deviation units. The p-value for the BI-score has p = 4.3 × 10 for POP versus normal conditions. A reference BI-score curve against age for normal pelvic floor conditions was defined.
CONCLUSIONS
Quantitative transformations of the pelvic tissues, support structures, and functions under diseased conditions may be studied with the BI-score in future research and practical applications.
Topics: Case-Control Studies; Female; Humans; Muscle Contraction; Pelvic Floor; Pelvic Floor Disorders; Pelvic Organ Prolapse
PubMed: 35230483
DOI: 10.1007/s00192-022-05120-w