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PubMed1991

Composition of myofiber types in the pectoral girdle musculature of sheep.

The muscles of the pectoral girdle in domestic animals attach the forelimbs to the trunk and function as the suspensory apparatus. In the present study the composition of the pectoral girdle musculature of sheep by myofiber types was examined. Myofibers showing a strong reaction for alkali-stable myosin ATPase were classified into fast-twitch/glycolytic (FG) myofibers with a weak activity for NADH tetrazolium reductase (NADH-TR) and fast-twitch/oxidative/glycolytic (FOG) myofibers with a moderate and strong NADH-TR activity. Myofibers showing a weak reaction for alkali-stable myosin ATPase and a strong activity for NADH-TR were classified as slow-twitch/oxidative (SO) myofibers. The SO myofibers that showed a granular and striped pattern of diformazan deposits in NADH-TR activity were classified as SO-1 myofibers, whereas the SO myofibers characterized by a reticular pattern of diformazan deposits were classified as SO-2 myofibers. The trapezius, rhomboideus cervicis, and pectoralis descendens muscles situated superficially in the cranial regions of the back and chest had about 50% SO (SO-1 plus SO-2) myofibers. The deeply situated serratus ventralis cervicis and thoracis muscles had 37.5% SO myofibers. These five muscles included more SO-2 myofibers with large diameters than did all other muscles, and had about 50% and more cross-sectional area of SO myofibers. The other muscles had less than 32% SO myofibers and fewer SO-2 myofibers. The FOG and FG myofibers accounted for 50% or less in the muscles examined. Many muscles of the pectoral girdle had many fast-twitch (FOG plus FG) myofibers; they seem to meet locomotory requirements. In the pectoral girdle musculature, the SO myofibers were not necessarily distributed more in the deep regions than in the superficial regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

A cineradiographic and electromyographic study of mastication in Tenrec ecaudatus.

Regular chewing was studied in the specialized Malagasy insectivore Tenrec ecaudatus with the aid of precisely correlated electromyography of the main adductors, digastrics, and two hyoid muscles and cineradiography for which metallic markers were placed in the mandibles, tongue, and hyoid bone. During the power stroke the body of the mandible moves dorsally and medially. The medially directed component of movement at this time is greatly increased by simultaneous rotation of the mandible about its longitudinal axis. The highly mobile symphysis, spherical dentary condyle, loss of superficial masseter muscle and zygoma, and the simplified zalamnodont molars all appear to be related to the large amount of mandibular rotation that occurs during occlusion. The balancing side lateral pterygoid muscle (inferior head) apparently shifts the working side mandible laterally during the last part of opening and the first part of closing. The working side temporalis and the superficial masseter muscle are both responsible for the shift back to the midline. The temporalis is usually active to the same extent on the working and balancing sides during the power stroke. The level of activity (amplitude) of the temporalis and duration of the power stroke increase with harder foods. Whenever soft foods are chewed, the superficial masseter is only active on the working side; whenever foods of increasing hardness are chewed, its level of activity on the balancing side increases to approach that of the working side. Mandibular rotation is greatly reduced when hard foods are chewed.

Animals↗
PubMed2003

Pain differs from non-painful attention-demanding or stressful tasks in its effect on postural control patterns of trunk muscles.

Pain changes postural activation of the trunk muscles. The cause of these changes is not known but one possibility relates to the information processing requirements and the stressful nature of pain. This study investigated this possibility by evaluating electromyographic activity (EMG) of the deep and superficial trunk muscles associated with voluntary rapid arm movement. Data were collected from control trials, trials during low back pain (LBP) elicited by injection of hypertonic saline into the back muscles, trials during a non-painful attention-demanding task, and during the same task that was also stressful. Pain did not change the reaction time (RT) of the movement, had variable effects on RT of the superficial trunk muscles, but consistently increased RT of the deepest abdominal muscle. The effect of the attention-demanding task was opposite: increased RT of the movement and the superficial trunk muscles but no effect on RT of the deep trunk muscles. Thus, activation of the deep trunk muscles occurred earlier relative to the movement. When the attention-demanding task was made stressful, the RT of the movement and superficial trunk muscles was unchanged but the RT of the deep trunk muscles was increased. Thus, the temporal relationship between deep trunk muscle activation and arm movement was restored. This means that although postural activation of the deep trunk muscles is not affected when central nervous system resources are limited, it is delayed when the individual is also under stress. However, a non-painful attention-demanding task does not replicate the effect of pain on postural control of the trunk muscles even when the task is stressful.

Abdominal Muscles↗
PubMed1977

The panniculus carnosus in the domestic pig.

The panniculus carnosus arises from the superficial fascia of the midlateral back, inserts into the medial skin of the forelimb, and fuses ventrally with the contralateral cutaneous muscle. In the midback, forelimb, thigh, and groin the panniculus carnosus is lacking; there, superficial fascia alone is present. Both the panniculus carnosus and the superficial fascia divide the panniculus adiposus into a superficial compact layer and a less compact deep layer. The firm attachment of the dermis to the panniculus carnosus, and of the panniculus carnosus to the deep fascia, makes pigskin a more suitable model for comparison with human integument than the usual laboratory animals with loosely draped skin. When using the pigskin model, however, care must be exercised to define the level of incisions and the location of flaps or grafts, with respect to the panniculus carnosus.

Animals↗
PubMed2005

Musculoskeletal support of lumbar spine stability.

Using a biomechanical model and experimental data the self-stabilising behaviour of antagonistic trunk muscles was analyzed. The biomechanical model is constituted of a pair of antagonistic Hill-type muscles, their geometric arrangement with respect to the spine, and the instantaneous centre of rotation in frontal plane. Using Ljapunov's theory, the stability of certain motion and loading situations was analyzed. Applying a sensitivity analysis, the influence of different muscle properties and the geometric arrangement on stability was investigated. The simulations revealed that the stability of spinal movements depended primarily on the geometrical arrangement of muscles and the position of the centre of rotation of the spine, the latter was affected in turn by the activities of the profound muscles. To stabilize the situations simulated oblique muscle arrangements were necessary. In order to define an instantaneous centre of rotation in the lower region of the spine negative attachment angles (medio-lateral decline) of muscles were necessary, corresponding to the real anatomy of obliquus externus muscles. More cranially located instantaneous centres of rotation required positive attachment angles for stability, corresponding to obliquus internus or multifidus muscles. Furthermore, the fibre-type distribution of muscles influenced the stability of the system, i.e. a high percentage of fast-twitch-fibres supported the stabilisation. Conclusions drawn from the simulations were supported by experimental data. Sudden loads and quick-release perturbations with two different amplitudes were applied to the upper body of ten male subjects. In comparison to sudden load situations preactivation of muscles due to an external load, i.e. quick-release perturbation, led to significantly less dependency of the amplitude of deflection on the amplitude of the perturbation. This observation relates to the self-stabilising properties of the musculoskeletal system. In conclusion, training seems to be advantageous if directed towards not only enhancing the endurance capacity of the muscles, but also increasing the cross-sectional area of oblique fast-twitch-fibres. Training should also improve the co-ordination of deep and superficial trunk muscles. These findings may influence physiotherapy and training programs for low back pain patients.

Journal Article↗
PubMed2000

Modulation of human cutaneous reflexes during rhythmic cyclical arm movement.

The organization and pattern of cutaneous reflex modulation is unknown during rhythmic cyclical movements of the human upper limbs. On the assumption that these cyclic arm movements are central pattern generator (CPG) driven as has been suggested for leg movements such as walking, we hypothesized that cutaneous reflex amplitude would be independent of electromyographic (EMG) muscle activation level during rhythmic arm movement (phase-dependent modulation, as is often the case in the lower limb during locomotion). EMG was recorded from eight muscles crossing the human shoulder, elbow, and wrist joints while whole arm rhythmic cyclical movements were performed. Cutaneous reflexes were evoked with trains of electrical stimulation delivered at non-noxious intensities (approximately 2 x threshold for radiating paresthesia) to the superficial radial nerve innervating the lateral portion of the back of the hand. Phasic bursts of rhythmic muscle activity occurred throughout the movement cycle. Rhythmic EMG and kinematic patterns were similar to what has been seen in the human lower limb during locomotor activities such as cycling or walking: there were extensive periods of reciprocal activation of antagonist muscles. For most muscles, cutaneous reflexes were modulated with the movement cycle and were strongly correlated with the movement-related background EMG amplitude. It is concluded that cutaneous reflexes are primarily modulated by the background muscle activity during rhythmic human upper limb movements, with only some muscles showing phase-dependent modulation.

Adult↗
PubMed2003

Pain and motor control of the lumbopelvic region: effect and possible mechanisms.

Many authors report changes in the control of the trunk muscles in people with low back pain (LBP). Although there is considerable disagreement regarding the nature of these changes, we have consistently found differential effects on the deep intrinsic and superficial muscles of the lumbopelvic region. Two issues require consideration; first, the potential mechanisms for these changes in control, and secondly, the effect or outcome of changes in control for lumbopelvic function. Recent data indicate that experimentally induced pain may replicate some of the changes identified in people with LBP. While this does not exclude the possibility that changes in control of the trunk muscles may lead to pain, it does argue that, at least in some cases, pain may cause the changes in control. There are many possible mechanisms, including changes in excitability in the motor pathway, changes in the sensory system, and factors associated with the attention demanding, stressful and fearful aspects of pain. A new hypothesis is presented regarding the outcome from differential effects of pain on the elements of the motor system. Taken together these data argue for strategies of prevention and rehabilitation of LBP.

Humans↗
PubMedDate not supplied

Face lift, part 5: suspending sutures for platysma cording.

We describe the technical details used in applying nonabsorbable sutures running from the anterior platysma muscles and/or adjacent fascia back to the fascia just in front of or covering the sternocleidomastoid muscles. These sutures usually pass 1.5-2 cm below the angle of the mandible. Anteriorly, they cover or are attached to the platysma muscles at the level of the cervical concavity or angle. The sutures suspend or draw back the superficial musculoaponeurotic system (SMAS) at this level, preventing some of the anterior displacement of the platysma when it is contracted in normal use. We believe that the sutures have relatively long-lasting effects and that they delay the early return of "platysma cording" after cheek-neck lifting. Their application using Reverdin and Keith needles is demonstrated. Differences in technique when submental lipectomy is and is not performed with the lift are shown.

Face↗
PubMedDate not supplied

[Evaluation of risks of biomechanical overload of the upper limb in physical kinesis therapists].

Physical therapists are at risk for work-related musculoskeletal disorders (WMSDs). Contributing risk factors are job-task, mental stress and biomechanical overload, due to fixed and incorrect postures of neck, upper limbs and back. The purpose of this study was to investigate, by questionnaire and the use of muscle superficial EMG recording and analysis, the workload in the physical therapist activity, in order to provide suitable preventive measures.

Arm↗
PubMedDate not supplied

[Determination of pain severity in patients with low back pain using kinesiologic electromyography of the sacrospinal muscles].

The values of kinesiological electromyogram (EMG) of the sacrospinal muscles in the lumboscral region during trunk motion in the sagittal plane have been compared between a group of 51 healthy controls and 101 patients suffering from low back pain and/or ischialgia of degenerative etiology. Kinesiological EMG of the sacrospinal muscles refers to the scanning of superficial (EMG) activity of both sacrospinal muscles in the lumbar region by the use of MS6 EMG device and a PC. The patients were classified into five groups on the basis of their subjective reports on the severity of their painful condition evaluated on the visual analogous scale (VAS). The link was found between subjective assessment of pain and EMG activity during flexion and at peak flexion (p < 0.001) and during extension (p < 0.05); a more severe pain is accompanied by an increase in EMG activity.

Adolescent↗
PubMedDate not supplied

Are the changes in postural control associated with low back pain caused by pain interference?

BACKGROUND: Voluntary limb movements are associated with involuntary and automatic postural adjustments of the trunk muscles. These postural adjustments occur prior to movement and prevent unwanted perturbation of the trunk. In low back pain, postural adjustments of the trunk muscles are altered such that the deep trunk muscles are consistently delayed and the superficial trunk muscles are sometimes augmented. This alteration of postural adjustments may reflect disruption of normal postural control imparted by reduced central nervous system resources available during pain, so-called "pain interference," or reflect adoption of an alternate postural adjustment strategy. METHODS: We aimed to clarify this by recording electromyographic activity of the upper (obliquus externus) and lower (transversus abdominis/obliquus internus) abdominal muscles during voluntary arm movements that were coupled with painful cutaneous stimulation at the low back. If the effect of pain on postural adjustments is caused by pain interference, it should be greatest at the onset of the stimulus, should habituate with repeated exposure, and be absent immediately when the threat of pain is removed. Sixteen patients performed 30 forward movements of the right arm in response to a visual cue (control). Seventy trials were then conducted in which arm movement was coupled with pain ("pain trials") and then a further 70 trials were conducted without the pain stimulus ("no pain trials"). RESULTS: There was a gradual and increasing delay of transversus abdominis/obliquus internus electromyograph and augmentation of obliquus externus during the pain trials, both of which gradually returned to control values during the no pain trials. CONCLUSION: The results suggest that altered postural adjustments of the trunk muscles during pain are not caused by pain interference but are likely to reflect development and adoption of an alternate postural adjustment strategy, which may serve to limit the amplitude and velocity of trunk excursion caused by arm movement.

Abdominal Muscles↗
PubMed2002

External perturbation of the trunk in standing humans differentially activates components of the medial back muscles.

During voluntary arm movements, the medial back muscles are differentially active. It is not known whether differential activity also occurs when the trunk is perturbed unpredictably, when the earliest responses are initiated by short-latency spinal mechanisms rather than voluntary commands. To assess this, in unpredictable and self-initiated conditions, a weight was dropped into a bucket that was held by the standing subject (n = 7). EMG activity was recorded from the deep (Deep MF), superficial (Sup MF) and lateral (Lat MF) lumbar multifidus, the thoracic erector spinae (ES) and the biceps brachii. With unpredictable perturbations, EMG activity was first noted in the biceps brachii, then the thoracic ES, followed synchronously in the components of the multifidus. During self-initiated perturbations, background EMG in the Deep MF increased two- to threefold, and the latency of the loading response decreased in six out of the seven subjects. In Sup MF and Lat MF, this increase in background EMG was not observed, and the latency of the loading response was increased. Short-latency reflex mechanisms do not cause differential action of the medial back muscles when the trunk is loaded. However, during voluntary tasks the central nervous system exerts a 'tuned response', which involves discrete activity in the deep and superficial components of the medial lumbar muscles in a way that varies according to the biomechanical action of the muscle component.

Adult↗
PubMed2000

Endoscopic plastic surgery.

This article discusses three of the most popular endoscopic procedures in plastic surgery. Brow lift, transaxillary breast augmentation, and abdominoplasty are all cosmetic procedures with a high demand on inconspicuous scars; however, many investigators are working on reconstructive endoscopically assisted procedures. The treatment of many facial fractures involving the upper third of the facial skeleton usually requires long bicoronal incisions similar to the incisions used in the traditional brow lift. Attempts are under way to use endoscopically assisted minimal-access techniques to reduce and fixate these fractures. Many flaps used in plastic surgery require long scars for harvest, as in the case of the latissimus dorsi muscle flap. A relatively long incision on the back is needed to gain access to the muscle so that it can be elevated from structures superficial and deep to it. Although it is unpopular, investigators have reported harvesting latissimus dorsi muscle flaps through fairly small incisions with the assistance of balloon dissectors and endoscopes. In the field of hand surgery, carpal tunnel release surgery has had more than one method proposed to transect the carpal ligament using endoscopes and special instrumentation. Although some reported series claim excellent results, many hand surgeons are reluctant to use endoscopes because of associated complications and a high recurrence rate of carpal tunnel syndrome. Plastic surgery has special demands that emphasize aesthetics in cosmetic and reconstructive procedures. Although the lack of natural optical cavities has slowed the incorporation of endoscopic surgery in the specialty, surgically created cavities are used to allow for minimal access incisions. The future of plastic surgery will include an ever-increasing number of endoscopically assisted procedures. Cosmetic and reconstructive procedures will benefit from this new technology.

Abdomen↗
PubMed2001

Intramuscular myoelectric activity and selective coactivation of trunk muscles during lateral flexion with and without load.

STUDY DESIGN: Myoelectric activity of trunk muscles was measured intramuscularly in six healthy subjects as they maintained static trunk postures at 0 degrees, 15 degrees, and 30 degrees of lateral bending, unloaded or holding a 20-kg load in one hand alongside the body. OBJECTIVE: To determine the position and load dependency of the agonistic and antagonistic myoelectric responses of deep and superficial trunk lateral flexor muscles. SUMMARY OF BACKGROUND DATA: Loading of the trunk in lateral bending is associated with incidences of low back pain. The neuromotor control of muscles surrounding the spine may be decisive for its vulnerability. Earlier documentation of the activation pattern of trunk muscles, particularly those situated deeply, is incomplete. METHODS: Trunk angle was measured between S1-C7 and the vertical with a protractor. Electromyographic activity was recorded unilaterally from eight trunk muscles using intramuscular fine-wire electrodes inserted under the guidance of ultrasound. RESULTS: The electromyographic data showed that all muscles on the side contralateral to the load, except rectus abdominis, had their highest activity while loaded in the position most laterally flexed to the loaded side. The degree of bilateral coactivation was greater for the ventral than for the dorsal muscles. CONCLUSIONS: The myoelectric responses of most lumbar trunk muscles to static lateral flexion were dependent on trunk position and loading. The abdominal muscles demonstrated more coactivation than the other trunk muscles, and thus appeared to contribute more to trunk stabilization in laterally bent and loaded trunk positions.

Abdomen↗