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Muscle co contraction

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https://www.readbyqxmd.com/read/28821927/control-of-wrist-movement-in-deafferented-man-evidence-for-a-mixed-strategy-of-position-and-amplitude-control
#1
R Chris Miall, P Haggard, J D Cole
There is a continuing debate about control of voluntary movement, with conflicted evidence about the balance between control of movement vectors (amplitude control) that implies knowledge of the starting position for accuracy, and equilibrium point or final position control, that is independent of the starting conditions. We tested wrist flexion and extension movements in a man with a chronic peripheral neuronopathy that deprived him of proprioceptive knowledge of his wrist angles. In a series of experiments, we demonstrate that he could scale the amplitude of his wrist movements in flexion/extension, even without visual feedback, and appeared to adopt a strategy of moving via a central wrist position when asked to reach target angles from unknown start locations...
August 18, 2017: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
https://www.readbyqxmd.com/read/28817976/an-open-source-model-and-solution-method-to-predict-co-contraction-in-the-finger
#2
Alexander R MacIntosh, Peter J Keir
A novel open-source biomechanical model of the index finger with an electromyography (EMG)-constrained static optimization solution method are developed with the goal of improving co-contraction estimates and providing means to assess tendon tension distribution through the finger. The Intrinsic model has four degrees of freedom and seven muscles (with a 14 component extensor mechanism). A novel plugin developed for the OpenSim modelling software applied the EMG-constrained static optimization solution method...
August 17, 2017: Computer Methods in Biomechanics and Biomedical Engineering
https://www.readbyqxmd.com/read/28813799/toward-emg-controlled-force-field-generation-for-training-and-rehabilitation-from-movement-data-to-muscle-geometry
#3
Nicola Lotti, Vittorio Sanguinati
EMG signals are often used to control prostheses or assistive devices, but have been rarely used in rehabilitation. We propose a novel approach to personalised rehabilitation, based on EMG-driven force field adaptation. As a step toward this direction, here we show how EMG activity and movement data during a robot-assisted motor task can be used to estimate muscle geometry. We compare three different models of muscle geometry, characterised by (i) constant moment arms (CM); (ii) a normative model, based on polynomial functions of joint angles with fixed coefficients (normative polynomial, NP); and (iii) a person-adaptive model, in which the same polynomial model is fitted to individual subjects data (fitted polynomial, FP)...
July 2017: IEEE ... International Conference on Rehabilitation Robotics: [proceedings]
https://www.readbyqxmd.com/read/28803741/the-cardiovascular-toxicity-of-triadimefon-in-early-life-stage-of-zebrafish-and-potential-implications-to-human-health
#4
Hong-Cui Liu, Tian-Yi Chu, Li-Li Chen, Wen-Jun Gui, Guo-Nian Zhu
The health risk of triadimefon (TF) to cardiovascular system of human is still unclear, especially to pesticide suicides population, occupational population (farmers, retailers and pharmaceutical workers), and special population (young children and infants, pregnant women, older people, and those with compromised immune systems) who are at a greater risk. Therefore, firstly we explored the toxic effects and possible mechanism of cardiovascular toxicity induced by TF using zebrafish model. Zebrafish at stage of 48 h post fertilization (hpf) exposed to TF for 24 h exhibited morphological malformations which were further confirmed by histopathologic examination, including pericardial edema, circulation abnormalities, serious venous thrombosis and increased distance between the sinus venosus (SV) and bulbus arteriosus (BA) regions of the heart...
August 10, 2017: Environmental Pollution
https://www.readbyqxmd.com/read/28764814/differences-of-muscle-co-contraction-of-the-ankle-joint-between-young-and-elderly-adults-during-dynamic-postural-control-at-different-speeds
#5
Yoshitaka Iwamoto, Makoto Takahashi, Koichi Shinkoda
BACKGROUND: Agonist and antagonist muscle co-contractions during motor tasks are greater in the elderly than in young adults. During normal walking, muscle co-contraction increases with gait speed in young adults, but not in elderly adults. However, no study has compared the effects of speed on muscle co-contraction of the ankle joint during dynamic postural control in young and elderly adults. We compared muscle co-contractions of the ankle joint between young and elderly subjects during a functional stability boundary test at different speeds...
August 2, 2017: Journal of Physiological Anthropology
https://www.readbyqxmd.com/read/28754132/interactions-between-glycopyrronium-and-indacaterol-on-cholinergic-neurotransmission-and-contractile-response-in-bovine-trachealis
#6
Michele Baroffio, Giovanni Barisione, Vito Brusasco
BACKGROUND: Muscarinic-receptor antagonists and β-adrenoceptor agonists are used, alone or in combination, as first-line treatment for chronic obstructive pulmonary disease. Both drugs decrease airway smooth muscle tone by post-junctional mechanisms but they may have opposing effects on pre-junctional acetylcholine (ACh)-release. METHODS: We studied the effects of the muscarinic-receptor antagonist glycopyrronium (GLY), the β-adrenoceptor agonist indacaterol (IND) and their combination on electrically-induced ACh-release and contractile response in isolated bovine trachealis...
July 28, 2017: Respiratory Research
https://www.readbyqxmd.com/read/28744897/furosemide-suppresses-ileal-and-colonic-contractility-via-interactions-with-gaba-a-receptor-in-mice
#7
Kannaree Kaewsaro, Suphap Nuanplub, Sara Bumrungsri, Pissared Khuituan
The loop diuretic furosemide has an action to inhibit Na(+) -K(+) -2Cl(-) co-transporter at the thick ascending limb of Henle's loop resulting in diuresis. Furosemide also has the non-diuretic effects by binding to GABA-A receptor which may involve the gastrointestinal tract. The aim of this study was to investigate the effects of furosemide on smooth muscle contractions in mice ileum and proximal colon. Each intestinal segment suspended in an organ bath was connected to a force transducer. Signal output of mechanical activity was amplified and recorded for analysis using PowerLab(®) System...
July 26, 2017: Clinical and Experimental Pharmacology & Physiology
https://www.readbyqxmd.com/read/28735649/dystonia-as-a-patterned-motor-malflow
#8
Takahiro Mezaki
The definition of dystonia has been renewed repeatedly but always within the context of overactive muscle contractions. In dystonia the muscles unnecessary for a motion fail to be adequately suppressed because of the loss of central motor control, resulting in inappropriate movements or abnormal postures ("overflow phenomenon"). This represents, however, only one side of the disrupted motor control. Some patients complain of the inability to activate muscles necessary for the intended task despite the lack of motor paresis, as best exemplified by the apraxia of eyelid opening...
August 2017: Medical Hypotheses
https://www.readbyqxmd.com/read/28735103/voluntary-activation-of-the-trapezius-muscle-in-cases-with-neck-shoulder-pain-compared-to-healthy-controls
#9
Katrine Tholstrup Bech, Camilla Marie Larsen, Gisela Sjøgaard, Andreas Holtermann, Janet L Taylor, Karen Søgaard
Subjects reporting neck/shoulder pain have been shown to generate less force during maximal voluntary isometric contractions (MVC) of the shoulder muscles compared to healthy controls. This has been suggested to be caused by a pain-related decrease in voluntary activation (VA) rather than lack of muscle mass. The aim of the present study was to investigate VA of the trapezius muscle during MVCs in subjects with and without neck/shoulder pain by use of the twitch interpolation technique. Ten cases suffering from pain and ten age and gender matched, healthy controls were included in the study...
July 14, 2017: Journal of Electromyography and Kinesiology
https://www.readbyqxmd.com/read/28734171/muscle-synergies-reveal-impaired-trunk-muscle-coordination-strategies-in-individuals-with-thoracic-spinal-cord-injury
#10
Matija Milosevic, Hikaru Yokoyama, Murielle Grangeon, Kei Masani, Milos R Popovic, Kimitaka Nakazawa, Dany H Gagnon
Spinal cord injury (SCI) can result in paralysis of trunk muscles, which can affect sitting balance. The objective of this study was to analyze trunk muscle coordination of individuals with thoracic SCI and compare it to able-body individuals. A total of 27 individuals were recruited and subdivided into: (a) high thoracic SCI; (b) low thoracic SCI; and (c) able-body groups. Participants were seated and asked to lean their trunk in eight directions while trunk muscle activity was recorded. Muscle coordination was assessed using the non-negative matrix factorization (NMF) method to extract muscle modules, which are the synergistic trunk muscle activations, and their directional activation patterns...
July 1, 2017: Journal of Electromyography and Kinesiology
https://www.readbyqxmd.com/read/28733534/low-dose-of-dexmedetomidine-as-an-adjuvant-to-bupivacaine-in-cesarean-surgery-provides-better-intraoperative-somato-visceral-sensory-block-characteristcs-and-postoperative-analgesia
#11
Yong-Hong Bi, Xiao-Guang Cui, Rui-Qin Zhang, Chun-Yu Song, Yan-Zhuo Zhang
OBJECT: In this study, we aimed to investigate the beneficial effects of dexmedetomidine on somato-visceral sensory block characteristcs, postoperative analgesia and stress response of intrathecal bupivacaine administration in women undergoing cesarean section, and to find out which dose is better. METHODS: Sixty parturients with the American Society of Anesthesiologists (ASA) physical status I or II were anesthetized with intrathecal bupivacaine(10mg) alone or in combination with dexmedetomidine (3 μg and 5 μg) to undergo cesarean section...
June 29, 2017: Oncotarget
https://www.readbyqxmd.com/read/28732494/the-effects-of-therapeutic-hip-exercise-with-abdominal-core-activation-on-recruitment-of-the-hip-muscles
#12
Mandy Ky Chan, Ka Wai Chow, Alfred Ys Lai, Noble Kc Mak, Jason Ch Sze, Sharon Mh Tsang
BACKGROUND: Core stabilization has been utilized for rehabilitation and prevention of lower limb musculoskeletal injuries. Previous studies showed that activation of the abdominal core muscles enhanced the hip muscle activity in hip extension and abduction exercises. However, the lack of the direct measurement and quantification of the activation level of the abdominal core muscles during the execution of the hip exercises affect the level of evidence to substantiate the proposed application of core exercises to promote training and rehabilitation outcome of the hip region...
July 21, 2017: BMC Musculoskeletal Disorders
https://www.readbyqxmd.com/read/28730946/contribution-of-upper-limb-muscles-to-two-different-gripping-styles-in-elite-indoor-tug-of-war-athletes
#13
Wen-Tzu Tang, Wei-Chih Liao, Hsin-Min Lee
To investigate characteristic upper limb muscle use between two common tug of war (TOW) gripping styles, 20 elite athletes from two high school TOW teams were recruited. Under conditioned attack pulling (with 90% maximal force) on a tug machine, participants used their own habitual gripping style to pull for five 15-s trials. Force and kinematic measurements showed a significantly better force performance and higher centre-of-gravity tilting angle with the gripping style one than with the gripping style two (GS2) (both p < 0...
July 21, 2017: Sports Biomechanics
https://www.readbyqxmd.com/read/28728959/mechanisms-contributing-to-gait-speed-and-metabolic-cost-in-children-with-unilateral-cerebral-palsy
#14
Tatiana Pessoa Silva Pinto, Sérgio Teixeira Fonseca, Rejane Vale Gonçalves, Thales Rezende Souza, Daniela Virgínia Vaz, Paula Lanna Pereira Silva, Marisa Cotta Mancini
BACKGROUND: Gait speed and metabolic cost are indicators of functional capacity in children with cerebral palsy. Uncovering their mechanisms helps guide therapeutic actions. OBJECTIVES: To investigate the contributions of energy-generating and energy-conserving mechanisms to gait speed and metabolic cost of children with unilateral cerebral palsy. METHODS: Data on eccentric and concentric muscle work, co-contraction, elastic torque and vertical stiffness of the affected-limb, forcing torque of the non-affected limb, gait speed and metabolic cost were collected from 14 children with unilateral cerebral palsy, aged 6-12 years...
July 5, 2017: Brazilian Journal of Physical Therapy
https://www.readbyqxmd.com/read/28725924/effect-of-training-status-on-beta-range-corticomuscular-coherence-in-agonist-vs-antagonist-muscles-during-isometric-knee-contractions
#15
Fabien Dal Maso, Marieke Longcamp, Sylvain Cremoux, David Amarantini
Antagonist muscle co-activation is thought to be partially regulated by cortical influences, but direct motor cortex involvement is not fully understood. Corticomuscular coherence (CMC) measures direct functional coupling of the motor cortex and muscles. As antagonist co-activation differs according to training status, comparison of CMC in agonist and antagonist muscles and in strength-trained and endurance-trained individuals may provide in-depth knowledge of cortical implication in antagonist muscle co-activation...
July 19, 2017: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
https://www.readbyqxmd.com/read/28725191/bilateral-reflex-fluctuations-during-rhythmic-movement-of-remote-limb-pairs
#16
Rinaldo A Mezzarane, Tsuyoshi Nakajima, E Paul Zehr
The modulation of spinal cord excitability during rhythmic limb movement reflects the neuronal coordination underlying actions of the arms and legs. Integration of network activity in the spinal cord can be assessed by reflex variability between the limbs, an approach so far very little studied. The present work addresses this question by eliciting Hoffmann (H-) reflexes in both limbs to assess if common drive onto bilateral pools of motoneurons influence spinal cord excitability simultaneously or with a delay between sides...
2017: Frontiers in Human Neuroscience
https://www.readbyqxmd.com/read/28720715/ischemic-preconditioning-does-not-alter-muscle-sympathetic-responses-to-static-handgrip-and-metaboreflex-activation-in-young-healthy-men
#17
Anthony V Incognito, Connor J Doherty, Jordan B Lee, Matthew J Burns, Philip J Millar
Ischemic preconditioning (IPC) has been hypothesized to elicit ergogenic effects by reducing feedback from metabolically sensitive group III/IV muscle afferents during exercise. If so, reflex efferent neural outflow should be attenuated. We investigated the effects of IPC on muscle sympathetic nerve activity (MSNA) during static handgrip (SHG) and used post-exercise circulatory occlusion (PECO) to isolate for the muscle metaboreflex. Thirty-seven healthy men (age: 24 ± 5 years [mean ± SD]) were randomized to receive sham (n = 16) or IPC (n = 21) interventions...
July 2017: Physiological Reports
https://www.readbyqxmd.com/read/28719636/the-non-diuretic-hypotensive-effects-of-thiazides-are-enhanced-during-volume-depletion-states
#18
Saeed Alshahrani, Robert M Rapoport, Kamyar Zahedi, Min Jiang, Michelle Nieman, Sharon Barone, Andrea L Meredith, John N Lorenz, Jack Rubinstein, Manoocher Soleimani
Thiazide derivatives including Hydrochlorothiazide (HCTZ) represent the most common treatment of mild to moderate hypertension. Thiazides initially enhance diuresis via inhibition of the kidney Na+-Cl- Cotransporter (NCC). However, chronic volume depletion and diuresis are minimal while lowered blood pressure (BP) is maintained on thiazides. Thus, a vasodilator action of thiazides is proposed, likely via Ca2+-activated K+ (BK) channels in vascular smooth muscles. This study ascertains the role of volume depletion induced by salt restriction or salt wasting in NCC KO mice on the non-diuretic hypotensive action of HCTZ...
2017: PloS One
https://www.readbyqxmd.com/read/28715333/wheelchair-neuroprosthesis-for-improving-dynamic-trunk-stability
#19
Kramay Patel, Matija Milosevic, Kimitaka Nakazawa, Milos R Popovic, Kei Masani
Trunk instability is a major problem for individuals with thoracic and cervical spinal cord injury. Functional electrical stimulation (FES) neuroprosthesis, a technology that uses small electrical currents to artificially contract muscles, has previously been utilized to improve trunk stability during quasistatic and dynamic sitting. The aim of this study was to develop the first powered wheelchair-based neuroprosthesis and to test its feasibility for improving trunk stability. Eleven male, able-bodied individuals participated in the feasibility study...
July 14, 2017: IEEE Transactions on Neural Systems and Rehabilitation Engineering
https://www.readbyqxmd.com/read/28714838/lower-extremity-muscle-activity-kinematics-and-dynamic-postural-control-in-individuals-with-patellofemoral-pain
#20
Shiho Goto, Naoko Aminaka, Phillip A Gribble
CONTEXT: Altered lower extremity muscle activity has been suggested to be associated with lower extremity kinematics in individuals with patellofemoral pain (PFP). However, few studies examined these relationships and the results are inconsistent. OBJECTIVES: To compare the lower extremity muscle activity, kinematics, pain level, and reach distance during the anterior reach of the Star Excursion Balance Test (SEBT) between participants with PFP and healthy individuals (CON)...
July 17, 2017: Journal of Sport Rehabilitation
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