Silent period produced by unloading of muscle during voluntary contraction.

Angel, Ronald W.; Eppler, W.; Iannone, Anthony M.

doi:10.1113/jphysiol.1965.sp007736

Cited by 108 publications

(46 citation statements)

References 8 publications

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“…activity were seen in relation to sudden unloading of the jaw closing muscles during biscuit breaking . This seemed paradoxical because 'load compensation' of this sort has been taken to indicate removal of a tonic drive from muscle spindles during steady contraction in, for example, the elbow flexors, shoulder adductors (Angel, Eppler & Iannone, 1965) or intercostal muscles (Newsom Davis & Sears, 1970). We confirmed by our methods for recording chewing that animal A showed obvious e.m.g.…”

Section: Resultsmentioning

confidence: 99%

The strength of the reflex response to sinusoidal stretch of monkey jaw closing muscles during voluntary contraction.

Goodwin¹,

Hoffman²,

Luschei³

1978

The Journal of Physiology

108

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SUMMARY1. Rhesus monkeys were trained to exert steady biting forces of 3-60 N for 1-2 sec. This behaviour was well maintained while sinusoidal or step opening and closing movements were imposed on the jaw.2. The amplitude of the force modulation during sinusoidal stretching was divided by the amplitude of movement to obtain the magnitude of stiffness. This estimate was made at frequencies from 2 to 50 Hz at amplitudes of 100 and 500 #um (half the peak-to-peak movement at the incisors).3. Peak magnitudes of stiffness were seen with frequencies of 8-15 Hz when the amplitude of movement was small; there was a great deal of variation between individual animals. This variation was most striking with mean forces of 25-35 N. The stiffness was greatest in animals that showed considerable spontaneous tremor, and the highest levels of stiffness were often recorded with frequencies near which tremor amplitude was large. A marked phase lag in the force response was often seen during small amplitude stretching at 8-30 Hz. 6. Such reflex responses as persisted after the lesions were small and inhibitory. E.m.g. silences followed both step stretch and release; the response to release was a 'load compensation' that could not be attributed to spindle afferents.

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Section: Resultsmentioning

confidence: 99%

The strength of the reflex response to sinusoidal stretch of monkey jaw closing muscles during voluntary contraction.

Goodwin¹,

Hoffman²,

Luschei³

1978

The Journal of Physiology

108

View full text Add to dashboard Cite

show abstract

“…Therefore, it was concluded that PMRs were of minimal importance. Instead, it was put forward that muscle spindles are the principal contributors to the unloading reflex, primarily because the latency of the onset of SEMG reduction is consistent with a monosynaptic pathway, but also because muscle spindles are thought to be responsible for the unloading reflex in the limbs (Angel et al ., 1965(Angel et al ., , 1973Lamarre and Lund, 1975;Miles and Wilkinson, 1982;Poliakov and Miles, 1994;Miles et al ., 1995).…”

Section: Unloading Of the Jawmentioning

confidence: 99%

Reflex Control of Human Jaw Muscles

Türker

2002

Critical Reviews in Oral Biology & Medicine

139

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Introduction The main function of the masticatory muscles is to break food down into pieces small enough to be swallowed. These are strong muscles that generate very large forces across very short distances and apply themvia rigid teeth. Such large forces can easily damage the teeth and their supporting tissues, tongue, cheeks, and the joints unless they are controlled precisely and effectively. There is evidence that the masticatory forces are controlled very precisely and that these forces change from bite to bite, depending on the consistency of the bolus. However, we do not fully understand this control mechanism. Unless the details of the mechanism that controls the masticatory forces in health and disease are thoroughly understood, the diagnosis and treatment of masticatory-related dysfunctions (such as temporomandibular dysfunction) will remain at the present "symptomatic" state.The aim of this review is to discuss what is known about the control of the human masticatory system and to propose a method for standardized investigation. This review is divided into six parts. The first part discusses the activation of human jaw muscle motoneurons by the central and peripheral sources. The second part discusses the receptors that are thought to contribute to the control of human mastication. In part 3, the reflexes elicited in human subjects are discussed. In part 4, simulated chewing experiments are discussed. In part 5, recording and analyzing methods are discussed, and a new method for estimating synaptic potential in human motoneurons is introduced. Finally, in part 6, three frequently asked questions are used to discuss the issues put forward in this review.Presently, our knowledge of mastication and its control by various receptors is patchy. Most of the work in this area comes from animal species with which investigators have used widely varying reduction techniques (anesthetization, decerebration, curarization, etc.). In these preparations, when nerve pathways are the subject of the study, the nerve to be stimulated is dissected free and teased so that one or a few identified nerve fibers are stimulated. The synaptic potential that is induced by this stimulation is recorded by means of microelectrodes that are placed within the central nervous system (reviewed in Lund, 1991;Linden, 1990). It is also possible for investigators to initiate "chewing" in animal preparations, and to study the effects of various receptor systems on the development of force (Lavigne et al ., 1987;.In humans, one must establish the connections of various afferents to the motoneurons that innervate the masticatory muscles under static or dynamic conditions to begin to understand the mechanism and control of mastication. The human work is challenging, since direct recording from motoneurons is not yet possible and precise stimulation of nerves is not easily controlled. Therefore, various indirect measurements have been used for the study of synaptic potential in human subjects. In most of these studies, afferent nerves are stimul...

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“…In fact, the stiffness measurement is performed during the SEC recoil, which is very brief in isolated muscle (1-5 ms) but longer in the case of in situ human experiments (40-50 ms): this is due to inertia opposed to the movement (limb and experimental device), which does not permit an instantaneous shortening of elastic elements. However, it was necessary to perform measurements before the appearance of an unloading reflex (Angel et al 1965), which is known to occur about 30 ms after the release. For the low levels of torque when the SEC stiffness is low, the passive resistance of the antagonistic muscles and passive structures can interfere with the SEC recoil.…”

Section: Series Elastic Stiffness: S Qr and Si Qrmentioning

confidence: 99%

Muscle and joint elastic properties during elbow flexion in Duchenne muscular dystrophy

Cornu

Goubel

Fardeau

2001

The Journal of Physiology

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Duchenne muscular dystrophy (DMD) is characterized by a direct effect on muscle fibres leading to muscle atrophy and weakness due to a lack of muscle dystrophin. Dystrophin is a sarcolemma cytoskeletal protein whose deficit leads to segmental necrosis of the muscle fibre. DMD is thus characterized by a decrease in the number of muscle fibres, which are progressively replaced by fibroadipose tissue. The first observed clinical signs relate to difficulties in running or climbing stairs and calf hypertrophy. Gait then becomes lordotic and waddling. Between 6 and 11 years of age, limb and torso muscles progressively and steadily decrease in strength. Loss of ambulation occurs (average 10.5 years of age) and all torso and limb muscles decrease in size.The assessment of muscle mechanical properties in DMD patients is mostly limited to a more or less sensitive evaluation of strength production, generally in static conditions and occasionally during a locomotor act. Two kinds of non-invasive technique are generally used to characterize muscle functional properties in DMD patients. (i) Semi-quantitative measurements (manual testing, timed scores during motor acts) are performed in routine clinical practice and afford a functional evaluation (Edwards & Hide, 1977;Brooke et al. 1981;Aitkens et al. 1989). For instance, manual testing (scored from 0 to 5) is based on an international graduated scale of muscle ability: MRC scale (Medical Research Council, 1943) reorganized from 0 to 10 (Brooke et al. 1981).(ii) Quantitative measurements (manual dynamometry) can be performed in some muscle groups and give a maximal voluntary contraction (MVC) measurement (Munsat, 1989).Understanding of the mechanisms responsible for muscle adaptation to altered functional demand (pathology or training) requires quantification of muscle mechanical properties. For instance, muscle contractility and muscle elasticity were experimentally found to be sensitive to periods of hyperactivity as well as hypoactivity (Goubel & Marini, 1987; Almeida Silveira et al. 1994;Canon & Goubel, 1995 1. Maximal voluntary contraction (MVC), series elastic stiffness and total joint stiffness during elbow flexion were investigated in healthy boys and in boys with Duchenne muscular dystrophy (DMD) in order to assess changes in mechanical properties induced by the disease.2. Two methods were used to perform stiffness measurements: (i) the application of sinusoidal perturbations to the joint during flexion efforts, allowing the calculation of total joint stiffness; (ii) the use of quick-release movements of the elbow, which had previously been maintained in isometric contraction, allowing the calculation of series elastic stiffness. In each case, stiffness was linearly related to torque, leading to the calculation of a normalized stiffness index as the slope of this stiffness-torque relationship.3. As expected, mean MVC was found to be much higher for healthy boys (20.02 ± 5.20 N m) than for DMD patients (3.09 ± 2.44 N m). Furthermore, the results showed that it was poss...

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Silent period produced by unloading of muscle during voluntary contraction.

Cited by 108 publications

References 8 publications

The strength of the reflex response to sinusoidal stretch of monkey jaw closing muscles during voluntary contraction.

The strength of the reflex response to sinusoidal stretch of monkey jaw closing muscles during voluntary contraction.

Reflex Control of Human Jaw Muscles

Muscle and joint elastic properties during elbow flexion in Duchenne muscular dystrophy

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