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PubMed2003

Differential modulation of tremor and pulsatile control of human jaw and finger by experimental muscle pain.

Resting tremor is seen in both the limbs and in the trigeminal motor system. These rhythmical perturbations are the result of alternating activation of antagonistic muscles, and these increase in amplitude during slow, voluntary movements. In the present study, we examined the effect of experimental muscle pain on finger and jaw tremor. The tremor in the mandible and in the middle finger was measured on separate occasions, at rest and during two constant-velocity movements. Pain was then induced by the infusion of hypertonic saline into a jaw-closing muscle (masseter) or into a finger extensor muscle (extensor digitorum longus, EDL). During masseter pain, the power at the peak tremor frequency of the mandible decreased significantly both when the jaw was at rest and during voluntary jaw movements at two velocities. In contrast, pain in EDL resulted in a significant increase in the power of finger tremor only during the two speeds of voluntary movement. No change in the peak tremor frequency was seen in either the finger or the jaw during pain. The most likely explanation for these data is that muscle pain tonically modulates the amplitude of the outputs from the central "pulsatile control" generators that drive the alternating activation of antagonistic muscles which produce tremor at rest and during movements. This modulation is in the opposite direction for systems controlling jaw and hand, suggesting a specific interaction of the nociceptive afferents with separate central oscillators.

Adult↗
PubMed1997

The role of the lateral pterygoid muscles in TMJ disorders during static conditions.

Intramuscular EMG of the lateral pterygoid muscles (LPM), surface EMG of the temporalis and masseter muscles and force measurements of the temporomandibular joint (TMJ) were synchronously used to investigate the biomechanical role of the two heads of the LPM in relation to internal derangement (ID) of the TMJ. EMG and kinetic analysis of five static conditions (resting, protraction, opening, molar and incisor clenching) and three maximum isometric masticatory forces (opening, molar and incisor clenching) were done to compare forces and muscular activity between TMJ ID and control subjects. The analysis of variance results of the integrated linear envelope (LE) EMG showed no significant differences between the two groups for the masseter and temporalis muscles. Therefore, there is no apparent reason to believe that these muscles are hyperactive in TMJ ID. The integrated LE EMG of the SLP was significantly lower in the TMJ group during molar clenching (104 microV + 60.0 over 159 microV + 68.8 for a p = .020). The superior head of the lateral pterygoid muscle (SLP) seemed to have lost its diskal stabilizing function. The integrated LE EMG signals of the ILP were significantly higher in the TMJ ID group during rest, resisted protraction and incisor clenching (p = .029, p = .046, p = .031 respectively). The ILP muscle has probably adapted to control the inner joint instability while continuing its own actions. The ILP muscle seemed to have lost its functional specificity. The results of the isometric forces showed that TMJ ID subjects exhibited significantly lower molar bite forces (297.1N over 419N, p = .042) confirming that they have less muscle strength and tissue tolerance than subjects with healthy masticatory muscle systems. A neuromuscular adaptation could be occurring in the TMJ ID masticatory system affecting muscular actions and forces.

Adaptation, Physiological↗
PubMed2004

Parafunctional clenching, pain, and effort in temporomandibular disorders.

This study tested the hypotheses that (1) parafunctional clenching increases pain and can lead to a diagnosis of temporomandibular disorder (TMD) pain and (2) electromyographic (EMG) activity during parafunctional clenching is significantly and positively correlated with reports of pain. Fourteen individuals without TMD participated in 5 consecutive days of 20-min long EMG biofeedback training sessions of the left and right temporalis and masseter muscles. Subjects were randomly assigned to either a Decrease or Increase group and were instructed to maintain EMG activity below 2 microV or above 10 microV during training, respectively. Two Increase subjects and no Decrease subjects were diagnosed, by a blinded examiner, with TMD pain following training. Self-reported pain posttraining was significantly higher for the Increase group. Masseter EMG activity was strongly correlated with pain. Parafunctional clenching increases pain and can lead to a diagnosis of TMD in otherwise pain-free individuals. Pain reports are positively correlated with the activity of the masseter muscle.

Adult↗
PubMed1993

Modulation of the jaw jerk reflex by the sympathetic nervous system.

The effect of sympathetic stimulation on the jaw jerk reflex has been studied in precollicular decerebrate rabbits. This reflex was elicited by a downward mandibular movement applied to the lower jaw through a servo controlled puller. Unilateral stimulation of the cervical sympathetic nerve at 10/s consistently induced a decrease in the JJR, i.e. a marked reduction of the EMG activity in the ipsilateral masseter muscle, accompanied by a 30-40% decrease in the reflexly developed force. In these trials EMG of the contralateral muscle, recorded as control, was not significantly affected. Bilateral stimulation of cervical sympathetic nerve strongly reduced or suppressed the EMG activity in both sides and produced a parallel decrease in the developed force which reached values ranging from 12.5% to 37.0% of controls (with an average of 28.9% +/- 8.9, S.D.). The effect of sympathetic stimulation was also tested on the contraction of the masseter muscle elicited by direct electrical stimulation. Sympathetic activation induced a modest increase in both amplitude and duration of muscle twitch, thus showing that the reduction in the reflex response can not be attributed to an action exerted by the adrenergic mediator on the muscular contraction. All these effects were almost completely abolished by the blockade of alpha-adrenergic receptors. They were proved not to be secondary to the sympathetically-induced vasomotor changes. Therefore the marked JJR reduction produced by activation of the sympathetic nervous system is suggested to be due to the sympathetically-induced decrease in neuromuscular spindle sensitivity to muscle length changes, previously reported.

Adrenergic alpha-Antagonists↗
PubMed1996

d-Sulpiride inhibits oral behaviour elicited from the nucleus accumbens of freely moving rats.

The present study analyzed the effect of intra-accumbens administration of the stereoisomers of sulpiride upon (3,4-dihydroxyphenylimino)-2-imidazoline (DPI)-induced changes in oral behaviours and electromyographic patterns of jaw muscles. In line with earlier findings, DPI (5 micrograms) administered into the nucleus accumbens increased chewing and tremor. l-Sulpiride (2-50 ng) had no effect on DPI-induced oro-facial behaviours. d-Sulpiride (10-50 ng) significantly antagonized the DPI-induced increase in chewing and had a biphasic effect on tremor with potentiation (10 ng) followed by attenuation (50 ng). When administered alone, l- or d-sulpiride did not affect oro-facial behaviours. The electromyographic signals, which were analyzed according to a previously described method, were described with the help of three classes: A (the seconds marked by frequency 3 Hz), B (the seconds marked by the frequencies 4-6 Hz); C (the seconds marked by the frequencies 7-15 Hz). DPI enhanced Class B and C of the masseter muscle but did not significantly affect any frequency class of the digastric muscle. l-Sulpiride (2-50 ng) had no effect on DPI-induced (5 micrograms) changes in electromyographic signals. d-Sulpiride (50 ng) antagonized the effects of DPI on Class B of the masseter muscle. Furthermore, d-sulpiride had a biphasic effect on Class C with potentiation (10 ng) followed by attenuation (50 ng). When administered alone, l- or d-sulpiride did not affect the frequency classes of the jaw muscles. It is concluded that d-sulpiride inhibits DPI-induced changes in oral behaviour and electromyographic patterns. It is suggested that d-sulpiride may be effective in the pharmacotherapy of oro-facial dyskinesias in man.

Animals↗
PubMed1996

Immunohistochemical studies on the transneuronal spread of virulent herpes simplex virus type 2 and its US3 protein kinase-deficient mutant after ocular inoculation.

The transneuronal spread of a virulent wild-type herpes simplex virus type 2 (HSV-2) and its US3 protein kinase-deficient (US3 PK-) mutant was immunohistochemically studied in mice after inoculations into the cornea, anterior chamber, tongue, and masseter muscle. After corneal inoculation, the wild-type virus was demonstrated in various brain stem areas including the trigeminal tract and nucleus, the reticular formation, and cerebellar nucleus group. Viral antigen-positive neurons were strictly confined to the ipsilateral spinal trigeminal nucleus in mice corneally infected with the US3 PK- mutant. No viral antigens were detected in the central nervous system (CNS) after inoculation with the mutant into the tongue and masseter muscle. However, when mice were immunosuppressed by treatment with cyclophosphamide, both the corneally infected mutant and wild-type virus could invade the CNS. The results suggest that the US3 PK- mutant principally retains the capacity to spread in the CNS.

Animals↗
PubMed1996

In vivo and in vitro bone strain in the owl monkey circumorbital region and the function of the postorbital septum.

Anthropoids and tarsiers are the only vertebrates possessing a postorbital septum. This septum, formed by the frontal, alisphenoid, and zygomatic bones, separates the orbital contents from the temporal muscles. Three hypotheses suggest that the postorbital septum evolved to resist stresses acting on the skull during mastication or incision. The facial-torsion hypothesis posits that the septum resists twisting of the face about a rostrocaudal axis during unilateral mastication; the transverse-bending hypothesis argues that the septum resists caudally directed forces acting at the lateral orbital margin during mastication or incision; and the tension hypothesis suggests that the septum resists ventrally directed components of masseter muscle force during mastication and incision. This study evaluates these hypotheses using in vitro and in vivo bone strain data recorded from the circumorbital region of owl monkeys. Incisor loading of an owl monkey skull in vitro bends the face upward in the sagittal plane, compressing the interorbital region rostrocaudally and "buckling" the lateral orbital walls. Unilateral loading of the toothrow in vitro also bends the face in the sagittal plane, compressing the interorbital region rostrocaudally and buckling the working side lateral orbital wall. When the lateral orbital wall is partially cut, so as to reduce the width of its attachment to the braincase, the following changes in circumorbital bone strain patterns occur. During loading of the incisors, lower bone strain magnitudes are recorded in the interorbital region and lateral orbital walls. In contrast, during unilateral loading of the P3, higher bone strain magnitudes are observed in the interorbital region, and generally lower bone strain magnitudes are observed in the lateral orbital walls. During unilateral loading of the M2, higher bone strain magnitudes are observed in both the interorbital region and in the lateral orbital wall ipsilateral to the loaded molar. Comparisons of the in vitro results with data gathered in vivo suggest that, during incision and unilateral mastication, the face is subjected to upward bending in the sagittal plane resulting in rostrocaudal compression of the interorbital region. Modeling the lateral orbital walls as curved plates suggests that during mastication the working side wall is buckled due to the dorsally directed component of the maxillary bite force which causes upward bending of the face in the sagittal plane. The balancing side lateral orbital wall may also be buckled due to upward bending of the face in the sagittal plane as well as being twisted by the caudoventrally directed components of the superficial masseter muscle force. The in vivo data do not exclude the possibility that the postorbital septum functions to improve the structural integrity of the postorbital bar during mastication. However, there is no reason to believe that a more robust postorbital bar could not also perform this function. Hypotheses stating that the postorbital septum originally evolved to reinforce the skull against routine masticatory loads must explain why, rather than evolving a postorbital septum, the stem anthropoids did not simply enlarge their postorbital bars.

Animals↗
PubMedDate not supplied

Etomidate as a sole agent for endotracheal intubation in the prehospital air medical setting.

INTRODUCTION: Etomidate is an anesthetic agent with rapid onset, short duration of action, a generally stable hemodynamic profile, and cerebroprotective effects. It is used in the hospital setting to facilitate emergency endotracheal intubation. This helicopter EMS used etomidate as an intubating agent without paralytics for 2 years. METHODS: Intubations performed by the helicopter crew using etomidate alone were reviewed. Intubation was classified as successful or unsuccessful. Successful intubations requiring three or more attempts or repeated doses of etomidate were interpreted as difficult. RESULTS: Fifty patients received etomidate to facilitate orotracheal intubation. Etomidate was the sole agent in 44 of these cases. Mean age was 31 years (range 4-79); 35 patients (80%) were men. Most patients (79%) were victims of blunt trauma. The mean dose of etomidate was 0.5 mg/kg (range 0.3-1.1). Hemodynamic parameters remained stable. Intubation was successful in 39 patients (89%). Intubation was difficult in seven patients (16%) and unsuccessful in five (11%). Masseter muscle spasm was noted in three of the five patients for whom intubation was unsuccessful. Other complications included emesis in eight patients and seizure-like activity in one patient. CONCLUSION: Etomidate can be used to facilitate emergency endotracheal intubation in the prehospital air medical setting, with a success rate of 89%. At the doses used in the study, hemodynamic parameters remained stable, but intubation was difficult or unsuccessful in 27% of patients. Masseter muscle spasm, which may represent orofacial myoclonus or inadequate relaxation, is common in patients who cannot be intubated with etomidate. Etomidate is recommended as a sole agent for facilitating intubation only when rapid sequence intubation with paralysis is contraindicated or otherwise undesirable.

Adolescent↗
PubMed1994

[Short-latency responses of jaw-movements to loading and unloading in complete denture wearers].

The reaction of the masseter muscles was studied by giving various loads to the mandible. Five dentulous volunteers and five edentulous patients participated in this study. They were asked to bite two bars in which the upper was immovable and the lower was connected with the torquemotor and to maintain the mandibular position although their mandibles were given the load changes. The load changes corresponded to the food consistency and were performed by the torquemotor rapidly. When the load force increased rapidly, the full-rectified electromyographic activity of the masseter muscle was facilitated 7.5-9.4 ms in the dentulous and 9.3-11.7 ms in the edentulous. Similarly, when the load force decrease rapidly, it was depressed to 11.1-12.9 ms and 10.6-16.4 ms, respectively. The number of synapses in the neuronal mechanism of loading and unloading reflexes showed no difference between the edentulous and the dentulous. Therefore, it is clear that the periodontal mechano-receptor does not cause the loading and unloading reflexes. As a result, the author suggests that the main receptor for the rapid masticatory movement should be the jaw-closer muscle spindle, which implicates that the complete denture wearers can masticate various kinds of foods smoothly.

Adult↗
PubMed1980

Further studies on the blood-brain barrier to low molecular weight substances. An ultrastructural cytochemical study.

A high resolution cytochemical study was performed in cats to investigate the cerebral blood vessel permeability to low molecular weight non-liposoluble substances. Sodium ferrocyanide was injected to four adult cats through an intraventricular canula and a copper solution was perfused intravascularly. Electroencephalographic recording throughout the experiments showed no detectable alterations induced by the administered solutions. Brain fragments fixed by intravascular perfusion were processed for electron microscopy. Pineal gland from the same animals and masseter muscle fragments in which ferrocyanide had been directly injected in those animals were studied as controls. A copper ferrocyanide suspension was directly injected into the lateral ventricle to two cats and 15 min later the brains were fixed by perfusion and processed for electron microscopy. An electrondense precipitate was seen in the interstitial and perivascular space, but not into the vessel lumen in these animals. No reaction product was observed in the brain parenchyma of cats injected intraventricularly with sodium ferrocyanide, whereas electron-dense deposits were clearly depicted in the pineal gland and masseter muscle in the same animals. The results further support the thesis that the junctions between the endothelial cells in brain capillaries represent a physical barrier to non-liposoluble substances.

Animals↗
PubMed2002

[The apoptosis in the course of experimental infection with T. pseudospiralis in mice].

The apoptosis in the course of experimental infection with T. pseudospiralis in mice. The level of apoptic cells in the lamina propria of the mucosa of the jejunum and in the masseter muscle in the mice infected with 200 larvae T. pseudospiralis was observed. Cryostat preparations made from jejunum and muscle samples on 7, 14, 21, 28, 60, 180 and 360 day post infection (dpi), were examined employing the TUNNEL method with the use of "In situ Cell Death Detection KIT Fluorescein" of Roche. The number of apoptic cells in the lamina propria of jejunum started to increase as early as on 7 dpi. The highest number of the apoptic cells, on an average - 56,4 in the crypta-villus unit, was recorded on 28 dpi, whereas the return to the standard level took place only 360 dpi. The level of the apoptic cells in the masseter muscle was the highest on 28 and 60 dpi, which constituted some 30% of all the cells of infiltration.

Animals↗
PubMed1993

Pictorial review: benign and malignant enlargement of the pterygo-masseteric muscle complex.

Seven cases of unilateral enlargement of the pterygoid and/or masseter muscles due to haemangioma (1), benign masseteric hypertrophy (2), rhabdomyosarcoma (2), leukaemic infiltration (1) and non-Hodgkin's lymphoma (1) are presented. The differential diagnosis of pterygo-masseteric muscle enlargement is outlined and the usefulness of computed tomography (CT) discussed.

Adolescent↗
PubMed2003

Treatment of squamous cell carcinoma of the anterior faucial pillar-retromolar trigone.

Cancer of the anterior faucial pillar-retromolar trigone is an uncommon head and neck tumor, which has historically been shown to be associated with poor prognosis. In this retrospective study, we reviewed our experience with primary surgery followed by postoperative radiation therapy in order to determine the impact of our treatment protocols on patients' outcome. Between January 1994 and December 1998, 31 patients with histologically proven squamous cell carcinoma (SCC) of the anterior faucial pillar-retromolar trigone were treated in our department. Surgical excision of the primary lesion and ipsilateral neck dissection were performed in all patients. Reconstruction was accomplished using masseter muscle flap or tongue flap. Postoperatively, most patients (90%) received radiation therapy (51-58 Gy) to the primary side and neck. Adjuvant chemotherapy was offered if histologic signs of aggressive behavior were identified. Four out of 31 patients were initially seen at stage I or II and 27 patients at stage III or IV of the disease. Metastatic disease was demonstrated in 78% of ipsilateral neck nodes. Occult metastases were found in 64% of clinically N0 necks. The 3-year loco-regional recurrence rates were 44.8%. SCC of retromolar trigone is considered as an aggressive and insidious tumor. The reconstruction of the deficit of the anterior faucial pillar-retromolar area with masseter muscle flap is a reliable, safe and absolutely functional method.

Adult↗
PubMed2005

Percutaneous balloon compression for the treatment of trigeminal neuralgia: results in 56 patients based on balloon compression pressure monitoring.

OBJECT: Percutaneous balloon compression is an effective and technically simple method for treating trigeminal neuralgia (TN). Nevertheless, dysesthesias (10-20%) and masseter muscle weakness (66%) following the procedure have been noted. The purpose of this study was to evaluate the results of testing TN with percutaneous balloon compression aided by intraluminal pressure monitoring. METHODS: In this study the authors review the results and complications associated with percutaneous balloon compression by using intraluminal pressure monitoring data obtained in 65 procedures performed in 56 consecutive patients over 4 years. The mean patient age was 71 years (range 37-92 years), and the mean follow-up duration was 17 months (range 3-38 months). The mean intraluminal compression pressure was (1160 +/- 62 mm Hg), and the mean duration of compression was 1.15 +/- 0.27 minutes. The trigeminal depressor response was observed in 60 (92%) of 65 procedures, and initial pain relief occurred in 92% of patients. The recurrence rate in patients who had initial relief was 16% (nine of 56). The mean time until recurrence in patients who experienced pain relief after surgery was 13 months (range 3-23 months). Mild numbness immediately after surgery was observed in 83% of patients. At the most recent evaluation, 17% of patients reported persistent, nontroublesome numbness and none had moderate or severe numbness. Minor dysesthesia was present in two patients (4%). Mild masseter muscle weakness occurred in 24% of patients and resolved within a maximum period of 1 year. No patient experienced anesthesia dolorosa, corneal keratitis, or other cranial nerve deficits. These morbidity rates are lower than the incidence reported in the literature when pressure monitoring is not used. CONCLUSIONS: These data show that by monitoring compression pressure and limiting the duration of compression, it is possible to reduce the incidence of dysesthesias, severe numbness, and masseter weakness after surgery without increasing the rate of recurrent pain in patients with classic TN.

Adult↗
PubMed1995

The effects of attentional factors on an inhibitory jaw reflex in man.

Electromyographic recordings (EMGs) were made from the active masseter muscle, of the inhibitory reflex evoked by application of electrical stimuli to the skin of the upper lip in fifteen human subjects. In control sequences, the reflex had a mean latency of 42 +/- 1.1 ms and a mean duration of 45 +/- 2.1 ms. The magnitude of the reflex (measured by integration of the EMG) was reduced (by 18 +/- 7.0%, n = 11; P < 0.05, Student's t test) while the subjects concentrated on a visual feedback signal in order to maintain a steady level of EMG activity. It was further reduced (by 25 +/- 3.6%, n = 10; P < 0.001, Student's t test) when the subjects additionally undertook mental calculations (the 17-times table). These effects were predominantly in the later parts of the responses. They occurred regardless of whether the baseline activity in the masseter muscle was inadvertently raised or lowered during the conditioning procedures. It is concluded that attentional factors can modulate jaw reflexes in man by exerting an influence on the reflex pathway at a point prior to the motoneurones. The underlying mechanism may involve the activation of descending inhibitory pathways and/or a facilitation of mechanisms underlying excitatory responses in jaw closing muscles.

Adult↗
PubMed1989

[Experimental study of the influence of removal of the zygomatic arch on craniofacial growth and development].

To observe effects of the procedure on craniofacial growth and development, the author removed 10mm of the right zygomatic arch from rats. The subjects (128 rats) were divided into 3 groups: operation group, sham-operation group, and control group. Surgical removal of the right side of the zygomatic arch was performed on 51 rats; sham operations were performed on 42 rats, and 35 rats served as controls. Operations were performed 30 days after the animals' births. The rats were sacrificed 60 to 120 days after birth. Lateral and parietal cephalograms of the crania were projected by means of a profile projector, model V-16, and enlarged 5 times. Because they reveal craniofacial-facial morphology most clearly, 15 lateral and 7 parietal points were selected. Coordinates of these points were plotted by means of an X--Y plotter system Tracings were composed as follows: For lateral cephalograms, the intersphenoid synchondrosis(S)was the zero point, and the line between S and the basion (Ba) was the abscissa. For parietal cephalograms, the occipital bone was the zero point; and the line between (0) and the upper central (Ui) was the abscissa. The masseter muscles were microsectioned for observation of changes in muscle fibers. Results 1. There were no significant differences among the body weights of the 3 groups (control, operation, and sham operation). 2. There were no significant differences in ulnar length among the 3 groups 3. Facial asymmetry and changes in occlusion were noted in the group observed 120 days after surgery. 4. Lateral cephalographic examination showed that the zygomatic arch has almost no influence on craniofacial growth and development in terms of relations among the points examined. 5. Parietal cephalographic examination showed that removal of the zygomatic arch promoted depth development and suppressed width development in the zygomatic-arch region of the side on which surgery was performed. This may indicate that the zygomatic arch acts to suppress anterior and posterior craniofacial growth and development while promoting growth and development in the lateral dimension. 6. Horizontal cytology of the masseter muscle showed atrophied masseteric tissue at the resected site of the zygomatic arch. But, because this was a partial resection, influence of muscular function is slight. And data obtained from this experiment must be considered the outcome of the removal of the zygomatic arch itself.

Animals↗
PubMed2000

Jaw-closing muscles of kangaroos express alpha-cardiac myosin heavy chain.

The masseter muscle of eutherian grazing mammals typically express beta or slow myosin heavy chain (MyHC). Myosins in the masseter of 4 species of kangaroos and a slow limb muscle of one of them were compared with their cardiac myosin by pyrophosphate and sodium dodecyl sulphate (SDS) gel electrophoresis, immunoblotting and immunohistochemistry. It was found that ventricular muscle contains three isoforms homologous to V1 (alpha-MyHC homodimer), V2 (heterodimer) and V3 (beta-MyHC homodimer) of eutherian cardiac muscle, and that the masseter contained V1, with traces of V2 and V3, in great contrast to eutherian ruminants, which express only V3. A polyclonal antibody (anti-KJM) was raised in rabbits against red kangaroo masseter myosin. After cross-absorption against limb muscle myofibrils, anti-KJM specifically reacted in Westerns with MyHCs from masseter but not limb muscles, and immunohistochemically with masseter, but not limb muscle fibers. In pyrophosphate Western blots, anti-KJM reacted with V1 but not with V3. However, a monoclonal antibody specific for eutherian slow myosin stained all kangaroo slow muscle fibers but only weakly stained scattered fibers in the masseter. The SDS-PAGE revealed that light chain composition of masseter and ventricular myosins is identical, but isoforms of both light chains of kangaroo limb slow myosin were observed. These results confirm that kangaroo jaw muscle express alpha-MyHC rather than beta-MyHC. The difference in MyHC gene expression between marsupial and eutherian grazers may be related to the fact that kangaroos are not ruminants, and have only a single chance to comminute food into fine particles, hence the need for the greater speed and power of muscle contraction associated with V1 containing muscle fibers.

Animals↗
PubMed1992

Methodological observations on positive and negative work (teeth grinding) by human jaw muscles.

Through electrognathography and surface electromyography of the right and left masseter muscle (MM), this methodologic study examined the excentric (lengthening) and concentric (shortening) contractions of brief (2000 ms) voluntary teeth grinding performed through canine as well as group function of the opposing teeth. We inferred that the most anterior and superior portions of the right and left MM were lengthened and shortened by at least 4.23 mm (right MM) and 4.82 mm (left MM). For the negative work efforts (excentric contractions) of canine function, the tensions of the ipsilateral MM ranged from 10 to 20% MVC and those of the contralateral MM from 4 to 14% MVC. For the positive work efforts (concentric contractions) of canine function, the tensions of the ipsilateral MM ranged from 11 to 44% MVC and those of the contralateral MM from 20 to 41% MVC. A comparison between canine and group function showed that the negative as well as positive work efforts of group function exceeded those of canine function.

Adult↗