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At least 1,351 records · Page 75Linked to original sources
PubMed2001

Response of trunk muscle coactivation to changes in spinal stability.

The goal of this effort was to assess the neuromuscular response to changes in spinal stability. Biomechanical models suggest that antagonistic co-contraction may be related to stability constraints during lifting exertions. A two-dimensional biomechanical model of spinal equilibrium and stability was developed to predict trunk muscle co-contraction as a function of lifting height and external load. The model predicted antagonistic co-contraction must increase with potential energy of the system even when the external moment was maintained at a constant value. Predicted trends were compared with measured electromyographic (EMG) data recorded during static trunk extension exertions wherein subjects held weighted barbells at specific horizontal and vertical locations relative to the lumbo-sacral spine junction. The task was designed to assure the applied moment was identical during each height condition, thereby changing potential energy without influencing moment. Measured EMG activity in the trunk flexors increased with height of the external load as predicted by the model. Gender difference in spinal stability were also noted. Results empirically demonstrate that the neuromuscular system responds to changes in spinal stability and provide insight into the recruitment of trunk muscle activity.

Abdominal Muscles↗
PubMed1996

Protein metabolism in critical illness.

In summary, protein metabolism of critically ill patients is a field open to new investigations that will help us to understand better the mechanism behind 'autocannibalism', which is still today associated with mortality. Although the underlying disease is the major determinant of mortality, nutritional depletion will add morbidity, an addition that grows over time in the ICU. With conventional treatment the velocity of the catabolic process can at best be slowed down and the patient be bought time for other types of treatment to work. New forms of specific nutrition and adjuvant therapies may give us tools to prevent muscle depletion, without endangering the supply of essential substrates to the tissues in the splanchnic area. Muscle is at present a limiting organ for the ICU patient in two respects. A depleted muscle can no longer provide enough substrates for the splanchnic organs to maintain intestinal integrity and to maintain a high immunocompetence. In addition, a depleted muscle will be restored back to normal only very slowly; in elderly patients restoration may not even occur at all. The effects of an attenuation of muscle depletion on rehabilitation time have yet to be evaluated. An understanding of protein metabolism may be the key to better patient care in the ICU in the future.

Critical Illness↗
PubMed1985

Influence of the globus pallidus on arm movements in monkeys. III. Timing of movement-related information.

Monkeys were trained to make a visually triggered arm-reaching movement to a lighted button in a simple reaction-time paradigm, during which the reaction time (RT) and movement time (MT) were measured. Stimulus trains of varying duration were applied at various times before and during the movement at locations in the globus pallidus where application of long stimulus trains caused increased MTs. A critical stimulus period was identified during which stimulus application effectively prolonged MTs. The activity of pallidal neurons was examined during performance of the same behavioral task. More than 60% of the neurons examined showed task-related changes in activity that began before or during the reaching movement. For 45% of these cells, the initial change in firing occurred during the critical stimulus period, 50-150 ms before mechanically detected movement. Comparison of the critical stimulus period, the time of task-related changes in the discharge of pallidal neurons, and the time of EMG activity in muscles acting at the back, shoulder, elbow, and wrist revealed that both the critical stimulus period and changes in neuronal discharge occurred at or after initial muscle activation and during the buildup of EMG activity. These data are consistent with a model in which the globus pallidus plays a role in scaling the magnitude of muscle activity that determines movement velocity without affecting the initiation or sequential organization of the programmed motor output.

Animals↗
PubMed1997

Linking symptom-specific physiological reactivity to pain severity in chronic low back pain patients: a test of mediation and moderation models.

Symptom-specific reactivity to stress (lower paraspinal muscle reactivity) among chronic low back pain (CLBP) patients may exacerbate chronic pain. It was hypothesized that among CLBP patients (N = 107) only stress-induced lower paraspinal reactivity, and not reactivity in other indexes, would predict pain severity (PS), and that lower paraspinal reactivity would mediate or moderate links between depression and PS. Electromyogram readings from lower paraspinal and trapezius muscles, systolic and diastolic blood pressures, and heart rate were collected during mental arithmetic (MA) and an anger recall interview. The moderator hypothesis was supported: Only lower paraspinal reactivity during MA was related significantly to PS, but only among patients with high levels of depression. Thus, a profile of lower paraspinal hyperreactivity plus depressed affect may aggravate CLBP.

Adult↗
PubMed2006

Calf-head sign in Miyoshi myopathy.

OBJECTIVE: To observe whether patients with Miyoshi-type dysferlinopathy demonstrate any distinct appearance in the back of the shoulders and upper back in a specific posture. DESIGN: Case series. SETTING: Neurology outpatient clinic of a north Indian tertiary care medical institute. PATIENTS: Fifteen patients from 9 families (10 males and 5 females; age range, 16-42 years) who had Miyoshi myopathy with onset of calf and shin muscle wasting between the ages of 9 and 28 years and a myopathic pattern at electromyography, moderately high serum creatine kinase levels, and absence of dysferlin at immunohistochemical staining. INTERVENTIONS: Patients were asked to raise their arms with shoulders abducted and elbows flexed to 90 degrees . All were observed from behind for the morphological change in the bulk of different muscles of the upper back and shoulders. T1-weighted magnetic resonance imaging of the upper thorax and shoulder was performed in an oblique sagittal plane to confirm the clinical findings. MAIN OUTCOME MEASURE: Consistent pattern of muscle enlargement or wasting seen clinically and at magnetic resonance imaging that produces a particular diagnostic appearance. RESULTS: A characteristic appearance was observed on the upper back and shoulders that could be described as calf heads on a trophy sign. The sign was clearly visible in 6 patients, whereas it was present in a subtle manner in another 4. Some but not all components of the sign were visible in the rest of the patients. CONCLUSION: The calf heads on a trophy sign may be useful in identifying most patients with Miyoshi-type dysferlinopathy.

Adolescent↗
PubMed1997

Lumbar muscle rhabdomyolysis after abdominal aortic surgery.

Lumbar muscle rhabdomyolysis has been very rarely reported after surgery. The aim of this study was to determine its incidence and main characteristics in a large population undergoing abdominal aortic surgery. Over a 21-mo period, 224 consecutive patients, 209 male and 15 female, mean age 65 +/- 10 yr, underwent abdominal aortic surgery (aortic aneurysm in 142 patients and occlusive aortic degenerative disease in 82 patients). Surgical incision was a midline incision with exaggerated hyperlordosis in 173 patients and a flank incision with a retroperitoneal approach in 51 patients. Postoperative rhabdomyolysis was diagnosed in 20 patients. In these patients, 9 (4%) experienced severe low back pain, and lumbar muscle rhabdomyolysis was confirmed by tomodensitometry (n = 6) or muscle biopsy (n = 3). The remaining 11 patients had lower limb muscle rhabdomyolysis. Rhabdomyolysis occurred after surgery of longer duration, which involved more frequent visceral artery reimplantation, with longer duration of aortic clamping and greater intraoperative bleeding. Lumbar rhabdomyolysis occurred in younger patients who were more frequently obese. On first postoperative day, the mean creatine kinase (CK) value was greater in lumbar rhabdomyolysis than in lower limb rhabdomyolysis (17,082 +/- 15,003 vs 3,313 +/- 3,120 IU/L, P < 0.05). Acute renal failure and postoperative death did not occur in patients with lumbar muscle rhabdomyolysis. Lumbar rhabdomyolysis was not a rare event after abdominal aortic surgery (4%). This syndrome was characterized by postoperative low back pain of unusual severity, which required analgesic therapy, and induced a very high increase in CK with typical findings at tomodensitometry or muscle biopsy but was not associated with postoperative renal failure.

Acute Kidney Injury↗
PubMed1995

Correlations of isokinetic and psychophysical back lift and static back extensor endurance tests in men.

Isokinetic lift, psychophysical lift, and static back endurance tests are among the most widely used measurements of muscle function for determining risk for, and recovery from, back problems. After determining test repeatability we examined the degree of association between these test measures in 100 men selected to represent a variety of occupations and lifestyles. Isokinetic lifting had low correlations with test results for psychophysical lifting (r = 0.28) and static back endurance (r = 0.24). Static back endurance and psychophysical lift test results were not at all correlated (r = 0.03). RELEVANCE--:Muscle function measurements for back problems are sometimes arbitrarily selected due to health practioners' beliefs and preferences or practical reasons such as the availability of equipment. Yet little is known about the associations of these tests with one another or with anthropometric factors. The data presented in this study document that isokinetic lift, psychophysical lift, and static back endurance tests appear to measure very different aspects of muscle function, and comparing studies using these different test methods should be approached with these low inter-test correlations in mind.

Journal Article↗
PubMed2006

The effects of prior exposure, warning, and initial standing posture on muscular and kinematic responses to sudden loading of a hand-held box.

BACKGROUND: Twelve percent of work-related low back injuries have been attributed to sudden loading events. When a sudden load is applied to an object that is held in front of the body, postural responses are rapid, yet it is not clear whether these responses differ with respect to initial posture at the time of loading, or by providing prior exposure to, or warning of a sudden loading event. METHODS: Thirty male subjects in either an upright or stooped standing posture held a pre-weighted box that was suddenly pulled downwards. Surface electromyography techniques were used to detect onset latencies of seven muscles of the right lower limb and trunk, and two-dimensional motion data in the sagittal plane were simultaneously collected. The first trial involved sudden unexpected loading in the upright standing posture, without any prior experience or warning of the loading event. This was followed by a series of randomised loading trials in the upright and stooped standing posture, with and without prior warning of the loading event. FINDINGS: Prior exposure and warning was found to influence postural responses in the upright standing posture, decreasing muscle and joint onset latencies, and resultant maximal angular displacement of the trunk and lower limb. Perturbation in the stooped posture was less reliant on abdominal muscle activation and produced an overall different joint movement initiation pattern, with less joint displacement than in the upright standing position. INTERPRETATION: These findings indicate that prior exposure to, and warning of a sudden loading event lead to changes in postural responses and decreased joint excursion. These changes may contribute to increased stability and decreased risk of musculoskeletal injury.

Abdominal Muscles↗
PubMed1997

A neural network model for simulation of torso muscle coordination.

An artificial neural network (ANN) was created to simulate lumbar muscle response to static moment loads. The network model was based on an abstract representation of a motor control system in which muscle activity is driven primarily to maintain moment equilibrium. The network model parameters were obtained by an iterative method (trained), using a modification of the standard backpropagation algorithm and moment equilibrium constraints. In contrast to previous ANN models of muscle activity, patterns of muscle activity are not target (training) values, but rather emerge as a result of moment equilibrium constraints. Assumptions regarding the moment generating capacity muscles and competitive interactions between muscles were employed and enabled the prediction of realistic patterns of muscle activity upon comparison with experimental electromyographic (EMG) data sets (r2: 0.4-0.9). The success of the simulation model suggests that a motor recruitment plan can be mimicked with relatively simple systems and that 'competition' between responsive units (muscles) may be intrinsic to the learning process. Prediction of alternative recruitment patterns and differing magnitudes of co-contractile activity were achieved by varying competition parameters within and between units.

Abdominal Muscles↗
PubMed1977

Functional transformation of fast posterior latissimus dorsi muscle by "slow" nerve implanted in newly hatched chickens.

1. Contraction properties and the activity of Ca2+ - ATPase were investigated 2 and 5 to 6 1/2 months after transposition of the fast posterior latissimus dorsi muscle (PLD) to the other side in newly hatched chickens. At the same time the muscle was cross-innervated by the nerve originally supplying the slow anterior latissimus dorsi muscle (ALD). 2. The mean isometric twitch contraction time of these transposed, cross-innervated PLD muscles in the 2-month-old and 5 to 6 1/2-month-old groups was 61.6 +/- 4.2 msec and 72.5 +/- 10.8 msec respectively. When compared with values obtained in control PLD and ALD muscles (21.9 +/- 0.6 msec and 107.7 +/- 5.6 msec), contraction time was significantly prolonged by this procedure. 3. Ca2+ - ATPase activity was also found to change towards the slow muscle (activity in control PLD was 0.600 micronmoles Pi/mg myosin/min, in the transposed, cross-innervated PLD 0.462 and in control ALD muscle 0.156 respectively). 4. Foreign innervation may thus induce changes in functional and biochemical properties even in muscles considerably different in structure and function, if transformation is allowed to take place at a sufficiently early stage of development. The muscle transposition itself, by introducing the element of muscle dedifferentiation and regeneration, probably assists the transformation process by making the muscle more plastic to the neural influences.

Adenosine Triphosphatases↗
PubMedDate not supplied

[Inguinal hernia. The Shouldice parietal repair].

Parietal repair according to the Shouldice technique consists of a double line of sutures on each of three musculo-aponeurotic layers of the groin, i.e. successively: plicature of the transverse muscle and attachments; aponeuroplasty by back-to-back suture of the internal and external oblique muscles, and plicature of the aponeurosis of the external oblique muscle. Parietal repair of this kind is only possible after wide dissection of the inguinal region. It can be performed under local anaesthesia during a short hospitalization period. Normal activity is rapidly resumed, and in the experience of those who favour this technique, the recurrence rate is a mere 1%.

Abdominal Muscles↗
PubMed1994

[The author's principles for treating small angle scoliosis in view of current concepts about scoliosis etiology and pathogenesis].

Hypothetical assumption, based on phylogenetic, anatomical and epidemiological studies as well as on clinical findings led the author to the conclusion, that regardless of an etiologic factor and the duration of its action the chief determinant for preserving the curve is the contracture of the short muscles and ligaments of the spine backed by scoliosis action of the long spinal muscles. Taking this into consideration the author has developed a method for small angle scolioses treatment by means of gravitational counteraction and removal of mainly ligamentous contracture of the spine. That can be accomplished by flexion-rotation exercises supplemented by "segmental gymnastics". The principles are validated by 30 years of clinical experience and advantageous results.

Braces↗
PubMedDate not supplied

[The loss of a right muscle in the orbit intra- or postoperatively].

One child four and half years old remains with a divergent deviation by forty-five degree with absence of adduction, after an operation of convergent strabismus at the left eye. Considering that is about by one postoperatorial paralytic strabismus, computer tomography praises the right intern muscle retracted at the back of orbit, but it doesn't adheres at the eyeball. It considers that the divergent strabismus was caused by the slide of postoperatorial muscle. Looking middle line of the muscle, parallel with the middle wall of the orbit, it praises the right intern muscle retracted and after the excision of the granulation tissue all round, displays the muscle with its normal lenght. It cuts 3.5 milimeters from this muscle and it practices the retroposition of the extern right muscle with 7 milimeters. It obtains postoperatorial orthophoria. It talks about possibility of lossen of a right muscle in orbit intra- and post-operatorial and the measures that are imposed in these situations.

Child, Preschool↗
PubMed1980

Lumbar dorsal ramus syndrome.

Low back pain, referred pain in the lower limbs, and spasm of the back, gluteal, and hamstring muscles are clinical features which can be induced in normal volunteers by stimulating structures which are innervated by the lumbar dorsal rami. Conversely, they can be relieved in certain patients by selective interruption of conduction along dorsal rami. These facts permit the definition of a lumbar dorsal ramus syndrome, which can be distinguished from the intervertebral disc syndrome and other forms of low back pain. The distinguishing feature is that, in lumbar dorsal ramus syndrome, all the clinical features are exclusively mediated by dorsal rami and do not arise from nerve-root compression. The pathophysiology, pathology, and treatment of this syndrome are described. Recognition of this syndrome, and its treatment with relatively minor procedures, can obviate the need for major surgery which might otherwise be undertaken.

Animals↗
PubMed1999

Muscle fatigue caused by repeated aerial combat maneuvering exercises.

BACKGROUND: Little is known about the development of in-flight muscular fatigue during repeated flights. HYPOTHESIS: This study was conducted to evaluate muscular fatigue in different upper body and neck muscles during repeated aerial combat maneuvering exercises. METHODS: Six pilots volunteered as test subjects. They performed one-to-one dog fight exercise three times (1 pilot, four times) in one day. During the flights, the pilots' electromyographic activity (EMG) was measured from the abdomen, back, neck and lateral neck. The mean muscular strain for each muscle was calculated. Before the first flight and after each flight, the maximal isometric strength of each muscle was measured. RESULTS: The results showed that maximal isometric strength between the first and last measurement decreased in the back, neck (p < 0.05) and lateral neck muscles. While the G-stress remained the same, the muscular strain during exercises increased in every muscle, but was significant only in neck and lateral neck (p < 0.05-0.01). Due to these changes, the fatigue index in the neck and lateral neck muscles was 2.0-2.1, and 1.3-1.4 (1.0 = no fatigue) in the abdomen and back muscles. CONCLUSIONS: Repeated aerial combat maneuvering exercises caused fatigue in every muscle studied. The fatigue was greater in the neck area, which may increase the risk for neck injuries, and may reduce mission effectiveness. The fighter pilots' muscular strength and endurance in the neck area are subjected to very high demands, especially if exercises are repeated several times. The recovery of the neck muscles from fatigue after repetitive exercises should receive special attention.

Abdominal Muscles↗