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IEEE Transactions on Bio-medical... Mar 2022This study develops a biomedical ultrasound imaging method to infer microstructural information (i.e., tissue level) from imaging mechanical behavior of skeletal muscle...
OBJECTIVE
This study develops a biomedical ultrasound imaging method to infer microstructural information (i.e., tissue level) from imaging mechanical behavior of skeletal muscle (i.e., organ level).
METHODS
We first reviewed the constitutive model of skeletal muscle by regarding it as a transversely isotropic (TI) hyperelastic composite material, for which a theoretical formula was established among shear wave speed, deformation, and material parameters (MPs) using the acoustoelasticity theory. The formula was evaluated by finite element (FE) simulations and experimentally examined using ultrasound shear wave imaging (SWI) and strain imaging (SI) on in vivo passive biceps brachii muscles of two healthy volunteers. The imaging sequence included 1) generation of SW in multiple propagation directions while resting the muscle at an elbow angle of 90°; 2) generation of SW propagating along the myofiber direction during continuous uniaxial muscle extension by passively changing the elbow angle from 90° to 120°. Ultrasound-quantified SW speeds and muscle deformations were fitted by the theoretical formula to estimate MPs of in vivo passive muscle.
RESULTS
Estimated myofiber stiffness, stiffness ratio of myofiber to extracellular matrix (ECM), and ECM volume ratio all agreed with literature findings.
CONCLUSION
The proposed mathematical formula together with our in-house ultrasound imaging method enabled assessment of microstructural material properties of in vivo passive skeletal muscle from organ-level mechanical behavior in an entirely noninvasive way.
SIGNIFICANCE
Noninvasive assessment of both micro and macro properties of in vivo skeletal muscle will advance our understanding of complex muscle dynamics and facilitate treatment and rehabilitation planning.
Topics: Arm; Elasticity Imaging Techniques; Humans; Muscle, Skeletal; Rest; Ultrasonography
PubMed: 34559632
DOI: 10.1109/TBME.2021.3115144 -
Journal of Strength and Conditioning... Jun 2020Pinto, BL and McGill, SM. Voluntary muscle relaxation can mitigate fatigue and improve countermovement jump performance. J Strength Cond Res 34(6): 1525-1529, 2020-When... (Clinical Trial)
Clinical Trial
Pinto, BL and McGill, SM. Voluntary muscle relaxation can mitigate fatigue and improve countermovement jump performance. J Strength Cond Res 34(6): 1525-1529, 2020-When muscles contract, they create force and stiffness. Thus, muscle activation and relaxation must be strategically sequenced to coordinate and control movement, to enhance athletic variables such as speed and strength. However, research has favored investigation of muscle activation over relaxation. Athletes such as runners, swimmers, and boxers often shake their limbs to allow the muscle to oscillate freely, immediately before a bout. The purpose was to investigate whether shaking the lower limbs with the intention to voluntarily relax the muscles of the limb has an effect on countermovement jump (CMJ) performance. Subjects performed 10 maximal effort CMJs with 30 seconds of rest between each jump. During the rest period, they either performed the relaxation technique or control condition (standing still). Statistical significance was considered at p < 0.05. Subjects significantly improved jump height, compared with their first jump of the day, when performing the relaxation technique. To further investigate the mechanism of enhancement, subjects were grouped into responders and nonresponders. The responder group significantly decreased their jump height and concentric phase impulse (relative to the first jump) during the control condition compared with the nonresponder group, indicating fatigue. When performing the relaxation technique, the responder group improved their jump height and mitigated fatigue by significantly increasing their unweighting impulse and unweighting force. The relaxation technique improved CMJ performance, specifically in those that fatigue with consecutive bouts, by enhancing unweighting, that requires muscle relaxation, rather than propulsion that requires activation. This technique can be useful for training or competition.
Topics: Adult; Athletes; Athletic Performance; Humans; Male; Muscle Fatigue; Muscle Relaxation; Muscle Strength; Muscle, Skeletal; Rest; Running; Young Adult
PubMed: 31714458
DOI: 10.1519/JSC.0000000000003326 -
Pediatric Physical Therapy : the... Jan 2022The study aimed to understand the effects of a set of simple gross motor exercises on pelvic floor muscle (PFM) resting tone (RT) in children with dysfunctional voiding...
PURPOSE
The study aimed to understand the effects of a set of simple gross motor exercises on pelvic floor muscle (PFM) resting tone (RT) in children with dysfunctional voiding symptomology.
METHODS
The study compared PFM RT for a single-sample before and after 2 protocols: exercise versus relaxation (metric standard).
RESULTS
Participants included 27 children ages 5.00 to 10.92 years. Preintervention PFM RT was similar between the interventions: 63% (exercise) and 78% (relaxation) of children decreased PFM RT following intervention. Between-intervention post-minus-prechanges in PFM RT were compared. Between-intervention differences were similar.
CONCLUSIONS
Exercise and relaxation protocols were comparable in lowering PFM RT in children with voiding dysfunction. Findings are clinically worthy in that either exercises or relaxation prior to toileting may assist with more complete emptying in children with symptoms.
Topics: Child; Child, Preschool; Exercise Therapy; Humans; Muscle Contraction; Pelvic Floor; Rest
PubMed: 34873121
DOI: 10.1097/PEP.0000000000000842 -
The European Respiratory Journal.... Jul 1989The respiratory muscles have great reserves, and under normal circumstances, in a fit person, it is probably impossible to fatigue them by activity. However, respiratory...
The respiratory muscles have great reserves, and under normal circumstances, in a fit person, it is probably impossible to fatigue them by activity. However, respiratory muscle fatigue can be induced experimentally, and with the stress of pulmonary disability, or with impairment of muscle function due to neuromuscular disease or skeletal deformity. Respiratory muscle fatigue contributes to respiratory failure and clinical deterioration. Resting the respiratory muscles can allow time for recovery but requires complete or partial artificial ventilation. Whilst positive pressure ventilation has been carried out for many years in Intensive Care Units, this technique is difficult in the long-term. Recently there has been renewed interest in non-invasive ventilatory support. Nocturnal ventilation in an iron lung can cause long-term improvement in acute and chronic respiratory failure of patients with neuromuscular or skeletal abnormalities. Such patients may be maintained with devices at home, such as a pneumosuit, a cuirass, or positive pressure ventilation via the nose. In patients with chronic pulmonary disease respiratory muscle rest may be helpful during acute exacerbations. However, the value of rest in chronic respiratory failure of end-stage pulmonary patients is as yet unproven.
Topics: Humans; Muscles; Respiratory Insufficiency; Respiratory System; Rest; Ventilation
PubMed: 2803412
DOI: No ID Found -
International Journal of Molecular... Sep 2018Transgenic mouse models have been important tools for studying the relationship of genotype to phenotype for human diseases, including those of skeletal muscle. We show...
Transgenic mouse models have been important tools for studying the relationship of genotype to phenotype for human diseases, including those of skeletal muscle. We show that mouse skeletal muscle can produce high quality X-ray diffraction patterns establishing the mouse intact skeletal muscle X-ray preparation as a potentially powerful tool to test structural hypotheses in health and disease. A notable feature of the mouse model system is the presence of residual myosin layer line intensities in contracting mouse muscle patterns. This provides an additional tool, along with the I/I intensity ratio, for estimating the proportions of active versus relaxed myosin heads under a given set of conditions that can be used to characterize a given physiological condition or mutant muscle type. We also show that analysis of the myosin layer line intensity distribution, including derivation of the myosin head radius, R, may be used to study the role of the super-relaxed state in myosin regulation. When the myosin inhibitor blebbistatin is used to inhibit force production, there is a shift towards a highly quasi-helically ordered configuration that is distinct from the normal resting state, indicating there are more than one helically ordered configuration for resting crossbridges.
Topics: Animals; Heterocyclic Compounds, 4 or More Rings; Mice; Mice, Transgenic; Models, Molecular; Muscle Contraction; Muscle, Skeletal; Mutation; Myosins; Protein Structure, Secondary; Rest; X-Ray Diffraction
PubMed: 30200618
DOI: 10.3390/ijms19092643 -
Journal of Applied Physiology Sep 1971
Topics: Adult; Biopsy; Body Temperature; Exercise Test; Glycogen; Heart Rate; Humans; Lactates; Leg; Male; Muscles; Oxygen Consumption; Physical Exertion; Respiration; Rest; Sports Medicine; Time Factors
PubMed: 5111852
DOI: 10.1152/jappl.1971.31.3.353 -
The Journal of Physiology Aug 1949
Topics: Humans; Muscles; Rest
PubMed: 15395031
DOI: No ID Found -
The Journal of Pharmacology and... Oct 1987The present study examines the relaxant selectivity of endothelium-derived relaxing factor (EDRF) released from cultured endothelial cells. Endothelial cells from bovine...
The present study examines the relaxant selectivity of endothelium-derived relaxing factor (EDRF) released from cultured endothelial cells. Endothelial cells from bovine pulmonary artery (CCL-209) in culture were grown on Cytodex-3 microcarrier beads, packed into a column and superfused to release EDRF. EDRF response was estimated by its ability to relax phenylephrine-contracted rings of rabbit aorta. Bradykinin and A23187 (10(-10) to 10(-6) M) caused dose-dependent release of EDRF from cultured bovine pulmonary artery endothelial cells. The release was dependent on endothelial cell number. A23187 caused a larger and longer-lasting release of EDRF than bradykinin. EDRF relaxation was selective for blood vessels. EDRF relaxed rabbit aortic rings, but it did not relax histamine-contracted guinea pig tracheal, rabbit taenia coli strips or oxytocin-contracted guinea pig uterine rings. These nonvascular smooth muscles were, however, relaxed by isoproterenol (10(-4) M) and sodium nitroprusside (SNP, 10(-5) M). The sensitivity of guinea pig aortic rings and tracheal strips to SNP were compared. The IC50 values for SNP (10(-9) to 10(-5) M) were 0.07 and 0.3 microM for aortic rings and tracheal strips, respectively. Although the tracheal strips were about 4-fold less sensitive than the aorta toward SNP, a complete relaxation was achieved. These results suggest that EDRF relaxes vascular smooth muscles but not respiratory, Gl or reproductive smooth muscles. Thus, EDRF may be a selective relaxant of vascular smooth muscle.
Topics: Animals; Aorta; Biological Products; Cattle; Cells, Cultured; Endothelium, Vascular; Guinea Pigs; Indomethacin; Kinetics; Muscle Contraction; Muscle Relaxation; Muscle, Smooth; Muscle, Smooth, Vascular; Nitric Oxide; Pulmonary Artery; Rabbits; Trachea
PubMed: 3499504
DOI: No ID Found -
California Medicine Sep 1955The first writings of curare appeared about 1500. Two hundred and fifty years later the first real experimentation took place with the drug and an additional two hundred...
The first writings of curare appeared about 1500. Two hundred and fifty years later the first real experimentation took place with the drug and an additional two hundred years elapsed before the drug found its true place in medicine. During the past decade it has become a valuable drug in anesthesia. The muscle relaxants have been divided into two groups according to their action - the curare-like or competitive inhibition blocking group, and the C-10-like or depolarizing blocking group. They act at the myoneural junction to produce relaxation with very little effect on the remainder of the body. In recent years the synthetic curare-like drugs have overshadowed purified curare.
Topics: Anesthesia; Cardiovascular Agents; Curare; Muscle Relaxants, Central; Relaxation
PubMed: 13250425
DOI: No ID Found -
The Journal of Neuroscience : the... Jul 2020Control of the body requires inhibiting complex actions, involving contracting and relaxing muscles. However, little is known of how voluntary commands to relax a muscle...
Control of the body requires inhibiting complex actions, involving contracting and relaxing muscles. However, little is known of how voluntary commands to relax a muscle are cancelled. Action inhibition causes both suppression of muscle activity and the transient excitation of antagonist muscles, the latter being termed active breaking. We hypothesized that active breaking is present when stopping muscle relaxations. Stop signal experiments were used to compare the mechanisms of active breaking for muscle relaxations and contractions in male and female human participants. In experiments 1 and 2, go signals were presented that required participants to contract or relax their biceps or triceps muscle. Infrequent Stop signals occurred after fixed delays (0-500 ms), requiring that participants cancelled go commands. In experiment 3, participants increased (contract) or decreased (relax) an existing isometric finger abduction depending on the go signal, and cancelled these force changes whenever Stop signals occurred (dynamically adjusted delay). We found that muscle relaxations were stopped rapidly, met predictions of existing race models, and had Stop signal reaction times that correlated with those observed during the stopping of muscle contractions, suggesting shared control mechanisms. However, stopped relaxations were preceded by transient increases in electromyography (EMG), while stopped contractions were preceded by decreases in EMG, suggesting a later divergence of control. Muscle state-specific active breaking occurred simultaneously across muscles, consistent with a central origin. Our results indicate that the later stages of action inhibition involve separate excitatory and inhibitory pathways, which act automatically to cancel complex body movements. The mechanisms of how muscle relaxations are cancelled are poorly understood. We showed in three experiments involving multiple effectors that stopping muscle relaxations involves transient bursts of EMG activity, which resemble cocontraction and have onsets that correlate with Stop signal reaction time. Comparison with the stopping of matched muscle contractions showed that active breaking was muscle state specific, being positive for relaxations and negative for contractions. The two processes were also observed to co-occur in agonist-antagonist pairs, suggesting separate pathways. The rapid, automatic activation of both pathways may explain how complex actions can be stopped at any stage of their execution.
Topics: Adult; Electromyography; Female; Fingers; Hamstring Muscles; Humans; Isometric Contraction; Male; Movement; Muscle Contraction; Muscle Relaxation; Muscle, Skeletal; Reaction Time
PubMed: 32611708
DOI: 10.1523/JNEUROSCI.0002-20.2020