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Annual International Conference of the... Nov 2021The isometric contraction is the most investigated muscle contraction, however most tasks in daily life involve anisometric contractions. Most hand prostheses studies...
The isometric contraction is the most investigated muscle contraction, however most tasks in daily life involve anisometric contractions. Most hand prostheses studies [1] use sEMG features to directly relate the exerted force as a means of intuitive control. It may thus be expected that similar sEMG-velocity relationships characterizing anisometric contractions may also contribute towards intuitive prosthetic hand control. While different contraction type relationships have been studied separately, in this work anisometric and isometric contraction experiments on the biceps brachii muscle were carried out using the same sEMG electrode system and the motor unit activity was then related to limb velocities and limb forces, to respectively characterize the isometric and anisometric contractions. This muscle was chosen as a simpler alternative to the synergistic hand muscles as an initial test of the general concept.Clinical Relevance- These contraction characterizations with sEMG may be used to afford prosthetic intuitive control and to assist in motor impairment diagnosis and rehabilitation.
Topics: Arm; Electromyography; Isometric Contraction; Muscle Contraction; Muscle, Skeletal
PubMed: 34892569
DOI: 10.1109/EMBC46164.2021.9630490 -
Journal of Theoretical Biology Dec 1989
Topics: Actins; Isometric Contraction; Models, Biological; Muscle Contraction; Myosins
PubMed: 2630799
DOI: 10.1016/s0022-5193(89)80124-9 -
Muscle & Nerve Oct 1994When magnetically stimulating peripheral nerves, a local cocontraction of muscle under the coil is observed. We assessed whether this contraction results from: (1)... (Clinical Trial)
Clinical Trial
When magnetically stimulating peripheral nerves, a local cocontraction of muscle under the coil is observed. We assessed whether this contraction results from: (1) magnetic stimulation of motor nerves, or (2) direct depolarization of the muscle membrane. Wrist extensor muscles of normal subjects were magnetically stimulated with the coil placed directly above the muscle. Neuromuscular transmission was then blocked by atracurium using a technique of local curarization. As a reference, the radial nerve was stimulated electrically. Magnetic and electrical stimuli were applied alternatingly every 10 s. Twitch force of wrist extension was measured isometrically over a period of about 70 min including the phase of complete neuromuscular block. Twitch amplitudes elicited by magnetic and electrical stimuli were equivalent during the whole experiment. These results suggest that muscle cocontraction following magnetic stimulation results from depolarization of terminal motor nerve branches.
Topics: Action Potentials; Atracurium; Electric Stimulation; Humans; Ischemia; Magnetics; Motor Neurons; Muscle Contraction; Muscles; Reference Values; Time Factors
PubMed: 7935524
DOI: 10.1002/mus.880171007 -
Biological Cybernetics Dec 2000In recent years, it has been recognised that improvements to classic models of muscle mechanical behaviour are often necessary for properly modelling coordinated... (Comparative Study)
Comparative Study
In recent years, it has been recognised that improvements to classic models of muscle mechanical behaviour are often necessary for properly modelling coordinated multi-joint actions. In this respect, the purpose of the present study was to improve on modelling stretch-induced force enhancement and shortening-induced force depression of muscle contraction. For this purpose, two models were used: a modified Hill model and a model based loosely on mechano-chemistry of the cross-bridge cycle (exponential decay model). The models were compared with a classic Hill modeland experimental data. Parameter values were based, as much as possible, on experimental findings in the literature, and tested with new experiments on the gastrocnemius of the rat. Both models describe many features of slow-ramp movements well during short contractions (300-500 ms), but long-duration behaviour is described only partly. The exponential decay model does not incorporate a force-velocity curve. Therefore, its good performance indicates that the status ofthe classic force-velocity characteristic may have to be reconsidered. Like movement-induced force depression and enhancement, it seems a particular manifestation of time-dependent force behaviour of muscle, rather than a fundamental property of muscle (like the length-tension curve). It is argued that a combination of the exponential decay model (or other models based on the mechano-chemistry of contraction) and structurally based models may be fruitful in explaining this time-dependent contraction behaviour. Furthermore, not in the least because of its relative simplicity, the exponential decay model may prove more suitable for modelling multi-joint movements than the Hill model.
Topics: Animals; Biomechanical Phenomena; Computer Simulation; Elasticity; Isometric Contraction; Models, Neurological; Muscle Contraction; Muscle, Skeletal; Rats; Tendons
PubMed: 11130582
DOI: 10.1007/s004220000190 -
Acta Neurologica Scandinavica Sep 1991The aim of this study was to examine contraction characteristics in striated muscles from Parkinson patients and to measure any changes in characteristics based on...
The aim of this study was to examine contraction characteristics in striated muscles from Parkinson patients and to measure any changes in characteristics based on changes in medication. Fifteen patients, 9 men and 6 women, mean age 61.6 (range 43-70) with mild to moderate parkinsonism, (Hoehn and Yahr I-III) were investigated, and the results were compared with a group of 8 normal controls (mean age 59.6, range 50-70). Twelve of the patients (7 men and 5 women) were also tested after a 24-h period without medication. Using supramaximal electrical stimulation of the ulnary nerve at the wrist contraction, characteristics in the m. adductor pollicis muscle can be recorded. Stimulation results were printed on a fast paper writer. The following characteristics were recorded: 1) electromechanical delay of contraction EMDc; 2) contraction time to half tetanus CTT1/2; 3) electromechanical delay of relaxation EMDr; 4) relaxation rate RR for 10 ms RR-10; 5) the force produced in the tetanic contraction at stimulus frequencies 5, 10, 20, 50 Hz. The results showed that the in initiation of contraction (EMDc) was normal compared with controls. CTT1/2 was shorter (p less than 0.001) in the group of Parkinson patients compared with normals. EMDr was not changed when compared with normals, but RR-10 was increased, p less than 0.05. Force levels at the different stimulation rates were not significantly changed. After withdrawal of medication all parameters were unchanged. Muscle contraction characteristics in tetanic contraction were found to be abnormal indicating either a possible preactivation in the muscle contraction or a secondary change in the muscles of patients with Parkinson's disease.
Topics: Adult; Aged; Antiparkinson Agents; Electric Stimulation; Electromyography; Female; Humans; Male; Middle Aged; Muscle Contraction; Observer Variation; Parkinson Disease
PubMed: 1950469
DOI: 10.1111/j.1600-0404.1991.tb04946.x -
Advances in Experimental Medicine and... 1984In order to measure muscle stiffness changes with a high time resolution and with minimal disturbance to the contractile mechanism per se, we constructed an apparatus...
In order to measure muscle stiffness changes with a high time resolution and with minimal disturbance to the contractile mechanism per se, we constructed an apparatus with which the propagation velocity of ultrasonic waves (MHz region) in the longitudinal or transverse direction was measured to serve as a measure of muscle stiffness. The longitudinal muscle stiffness started to increase on stimulation before the onset of isometric force, and reached a maximum before the peak twitch force. Analysis of experimental data indicated that, during an isometric tetanus, the increment of muscle longitudinal stiffness was about 6 X 10(7)N/m2, a value similar to those obtained by Truong (1974) and Ford et al. (1981) with sinusoidal vibrations (3 kHz) and length steps respectively. This suggests that the increment of muscle longitudinal stiffness during the activation of the contractile system results from the recruitment of an almost non-dispersive elastic component. In the case of transverse muscle stiffness, on the other hand, it started to decrease on stimulation before the onset of isometric force, and reached a minimum before the peak twitch force. Possible causes of this unexpected result is discussed in relation to the molecular mechanism of muscle contraction.
Topics: Animals; Elasticity; In Vitro Techniques; Isometric Contraction; Muscle Contraction; Muscle Relaxation; Muscles; Rana catesbeiana; Stress, Mechanical; Ultrasonography; Vibration
PubMed: 6611039
DOI: 10.1007/978-1-4684-4703-3_62 -
Annual Review of Physiology 1996This is a personal account of some of the successive steps in our understanding of the structural mechanism of muscle contraction during the last 45 years. It describes... (Review)
Review
This is a personal account of some of the successive steps in our understanding of the structural mechanism of muscle contraction during the last 45 years. It describes how I, as an ex-physicist, came to be studying muscle by X-ray diffraction in 1949; how the concepts of the double array of actin and myosin filaments and, later, the overlapping filament model and the sliding filament mechanism were developed; and how further electron microscope findings of the structural polarity of muscle filaments led to the suggestion that analogous structures and mechanisms might be involved in cellular motility. The article describes briefly how synchrotron radiation has made it possible to obtain detailed structural information about contracting muscle with millisecond time resolution and discusses some of the recent major advances in the field and the prospects of reaching a full understanding of the contraction mechanism.
Topics: Animals; Humans; Muscle Contraction; Muscles
PubMed: 8815787
DOI: 10.1146/annurev.ph.58.030196.000245 -
Motor Control Oct 2003Using transcranial magnetic stimulation (TMS), differences in the excitability changes of motor evoked potentials (MEPs) between isometric (force task) and isotonic...
Using transcranial magnetic stimulation (TMS), differences in the excitability changes of motor evoked potentials (MEPs) between isometric (force task) and isotonic (movement task) muscle contractions in a distal (first dorsal interosseous; FDI) and a proximal (middle deltoid; MD) muscle were studied. In the FDI muscle, the active threshold of MEP recruitment was significantly lower in the isotonic than that in the isometric muscle contraction in spite of identical background EMG activity levels. Additionally, the dependence of the MEP amplitude on background EMG activity was significantly greater in the isotonic than in the isometric muscle contraction at low EMG activity levels, but the difference disappeared beyond middle EMG activity levels. In the MD muscle, the dependence of the MEP amplitude on background EMG activity was significantly greater in the isotonic than in the isometric muscle contraction, and further this dependence was kept at all muscle contraction levels. These results indicate that the dependence of the MEP amplitude on background EMG activity is modulated not only by the different muscle contraction modes (isotonic and isometric), but also by muscle properties (distal and proximal). Thus, the present findings suggest that the task-specific extra excitation in the proximal muscle is definitely produced corresponding to task differences (task-dependent subliminal fringe), which might be explained by the predominant frequency principle if applied to the proximal muscle. On the other hand, the lack of task-dependent extra excitation in the distal muscle is explained by the predominant recruitment principle for force grading in small hand muscles.
Topics: Adult; Central Nervous System; Electromyography; Evoked Potentials, Motor; Humans; Isometric Contraction; Isotonic Contraction; Magnetics; Middle Aged; Muscle Contraction; Muscle, Skeletal; Skull
PubMed: 14999132
DOI: No ID Found -
Biophysical Journal Jul 1986A dynamic model of smooth muscle contraction is presented and is compared with the mechanical properties of vascular smooth muscle in the rat portal vein. The model is...
A dynamic model of smooth muscle contraction is presented and is compared with the mechanical properties of vascular smooth muscle in the rat portal vein. The model is based on the sliding filament theory and the assumption that force is produced by cross-bridges extending from the myosin to the actin filaments. Thus, the fundamental aspects of the model are also potentially applicable to skeletal muscle. The main concept of the model is that the transfer of energy via the cross-bridges can be described as a 'friction clutch' mechanism. It is shown that a mathematical formulation of this concept gives rise to a model that agrees well with experimental observations on smooth muscle mechanics under isotonic as well as isometric conditions. It is noted that the model, without any ad hoc assumptions, displays a nonhyperbolic force-velocity relationship in its high-force portion and that it is able to maintain isometric force in conditions of reduced maximum contraction velocity. Both these findings are consistent with new experimental observations on smooth muscle mechanics cannot be accounted for by the classical Hill model.
Topics: Animals; Elasticity; Isometric Contraction; Mathematics; Models, Biological; Muscle Contraction; Muscle, Smooth
PubMed: 3730500
DOI: 10.1016/S0006-3495(86)83448-8 -
Artificial Organs Jan 2001We developed a tactile sensor system that measures the stiffness of objects (tactile stiffness) and used it to describe the time course of muscle contraction and...
We developed a tactile sensor system that measures the stiffness of objects (tactile stiffness) and used it to describe the time course of muscle contraction and relaxation. We examined fatigue resistance of the latissimus dorsi muscle (LDM), which is preconditioned for cardiomyoplasty. Time to peak, ripple of LDM, and time constant were calculated from the time course of LDM contraction and relaxation as described by tactile stiffness. We compared conditioned and unconditioned LDMs using these 3 parameters. The time course can be described by tactile stiffness. Tactile stiffness fell exponentially during LDM relaxation. In mean values, time to peak increased 230%, ripple decreased 20%, and time constants increased 424%. Significant differences were shown in 3 parameters between conditioned and unconditioned LDMs (p < 0.05). Our tactile sensor system can describe the time course of LDM contraction and relaxation. Examining the difference in time courses, we might detect the level of LDM preconditioning for cardiomyoplasty.
Topics: Animals; Back; Cardiomyoplasty; Dogs; Elasticity; Electric Stimulation; Muscle Contraction; Muscle Relaxation; Muscle, Skeletal; Time Factors
PubMed: 11167558
DOI: 10.1046/j.1525-1594.2001.025001042.x