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PubMed1991

Continuous model of the human scoliotic spine.

The human scoliotic spine is mathematically modelled by employing the classical non-linear theory of curved beam-columns. A realistically representative muscle force system is included in the model. Scoliosis due to asymmetrical bi-lateral muscular contractions has been studied and arbitrary large displacements and curvatures are allowed. The two-dimensional model allowing curvature in the frontal plane can show the progression of a scoliotic curve from an initially straight configuration. For various parameter values, particularly muscle asymmetry, the model attempts to simulate the progression of actual scoliotic curves. Once these curves have been simulated, forces corresponding to corrective surgical systems are applied to the scoliotic spine. The corresponding corrected curves are then compared with those produced by a finite element model and also to the actual clinical curve. The comparisons were very favourable, considering the simplicity of the continuous model. The commonly observed phenomenon of the scoliotic curve lying to the weaker side of the back in terms of muscle strength is reproduced and explained by the model. The possible usefulness of continuous spinal models to analyse the overall deformation of the spine under various loading conditions can then be deduced.

Abdominal Muscles↗
PubMed1977

Body weight: its relation to tissue composition, segment distribution, and motor function. II. Development of Macaca mulatta.

The relative composition of skin, muscle, and bone and their distribution patterns throughout the body are given for a series of Macaca mulatta from 171 days conceptual age through adulthood. In terms of percent of total body weight, the musculature of these animals doubles during the firs postnatal year whereas bone and skin decrease. Regionally, the muscles of the thighs, back extensors, truncal-forelimb and upper arms increase most markedly. The thighs double and the upper arms increase whereas the trunk, hands, feet, and tail decrease. The biomechanical implications of these changes for motor development are discussed.

Age Factors↗
PubMed2004

Shape and thickness of cushion in a standing aid to support a forward bending posture: effects on posture, muscle activities and subjective discomfort.

In order to prevent low back pain (LBP) during dishwashing, we developed three types of aid with a thick cushion for supporting the shins and evaluated the effects of the standing aid on the subjective discomfort and muscle activities. Nine female volunteers were asked to wash plates in each of four working postures: (a) without the standing aid, (b) with the round type of aid, (c) with the small rectangular type of aid, and (d) with the large rectangular type of aid. With the three types of aid, the subjects were instructed to support the shins with the standing aid and to support the abdomen with the edge of a kitchen counter. In the three postures with the standing aid, 21.5 +/- 10.0% of the weight was supported with the standing aid and the kitchen counter. The subjective discomfort was milder and the muscle activity level in the low back was lower in the three postures with the standing aid than in the posture without the aid. It was thought that the round type of aid would be more effective in decreasing the discomfort in many of body regions and the muscle load on the low back than either of the rectangular types of aid. Therefore, it was suggested that the standing aid had the desired effect in decreasing discomfort and muscle load on the low back during dishwashing.

Adult↗
PubMed1993

Pontine-induced generalized suppression of postural muscle tone in a reflexively standing acute decerebrate cat.

In a reflexively standing acute decerebrate cat, the pontine tegmentum was electrically stimulated and the effects on postural muscle tone and locomotor movements evoked by stimulation of the mesencephalic locomotor region (MLR) were studied. A stimulating microelectrode was placed systematically at 1-mm increments throughout the pons (H - 2 to H - 10) at levels ranging from P0.0 to P6.5 dorsoventrally and mediolaterally from LR0 to L4 or R4. Another stimulating microelectrode was placed in the physiologically identified MLR. Stimuli delivered to the dorsomedial regions of the pontine tegmentum (P3 to P4, LR1.5 to 2.5, H - 4 to H - 6) resulted in simultaneous and bilateral suppression of tonic activities in the neck, lumbar back, forelimb and hindlimb muscles. The pontine inhibitory sites corresponded to the medial area of the central tegmental field (FTC) and the central area of the gigantocellular tegmental field (FTG), bilaterally. Effects of pontine induced suppression on those muscles were stimulus frequency and stimulus intensity-dependent and the effects persisted even after termination of the stimulation. With concomitant pontine stimulation, MLR-evoked locomotor movements were suppressed along with prolongation of the forelimb and hindlimb step cycles.

Animals↗
PubMed1982

Intra-articular synovial protrusions in the lower lumbar apophyseal joints.

Two types of joint inclusions are demonstrated in the lumbosacral facetal joints--a large, fat-filled, vascular intra-articular synovial protrusion projecting into the medial part of the joint from below, and a dense, fibrous, intra-articular synovial protrusion projecting from the joint capsule into the upper medial part of the joint. Although nerve fibers have not yet been demonstrated in the intra-articular synovial protrusions, it is reasonable to assume their presence in such a rich vascular network. These intra-articular synovial protrusions are vulnerable to being nipped between moving parts of the joints, in this way possibly transmitting traction forces to the related parts of the fibrous joint capsule. This could constitute a likely source of low back pain with resultant reflex muscle spasm.

Adolescent↗
PubMed1996

The piriformis syndrome.

Piriformis syndrome is an often misdiagnosed cause of sciatica, leg, or buttock pain, and disability. The sciatic nerve may be compressed within the buttock by the piriformis muscle, with pain increased by muscular contraction, palpation, or prolonged sitting. A thorough medical history and physical examination are essential to proper diagnosis. Diagnostic testing may be used to differentiate piriformis syndrome from other causes of sciatica, lower extremity weakness, and pain. This article reviews the pathophysiology and management of piriformis syndrome.

Buttocks↗
PubMed2005

Effects of pelvic stabilization on lumbar muscle activity during dynamic exercise.

Many commonly utilized low-back exercise devices offer mechanisms to stabilize the pelvis and to isolate the lumbar spine, but the value of these mechanisms remains unclear. The purpose of this study was to examine the effect of pelvic stabilization on the activity of the lumbar and hip extensor muscles during dynamic back extension exercise. Fifteen volunteers in good general health performed dynamic extension exercise in a seated upright position on a lumbar extension machine with and without pelvic stabilization. During exercise, surface electromyographic activity of the lumbar multifidus and biceps femoris was recorded. The activity of the multifidus was 51% greater during the stabilized condition, whereas there was no difference in the activity of the biceps femoris between conditions. This study demonstrates that pelvic stabilization enhances lumbar muscle recruitment during dynamic exercise on machines. Exercise specialists can use these data when designing exercise programs to develop low back strength.

Adult↗
PubMed1976

Studies on muscular strength-myogram (MSMG). Part 1. A new device of apparatus for measuring muscular strength-myogram.

1. A new apparatus, consisting of a strain gauge and a carrier amplifier, was devised for measuring back muscular and shoulder arms strength by the author. This apparatus was applied for analysing myogenic disorder related to muscular fatigue or pain. 2. Muscular strength with load and its myogram were recorded simultaneously, and their changes during the exertion were analysed. 3. Muscular strength-myograms of sternocleidomastoid muscle, upper trapezius muscle, deltoid muscle, rhomboid muscle and lumbodorsal muscle were observed from the back muscular strength-myogram, and those of teres minor muscle and major pectoral muscle from the shoulder arm strength-myogram. 4. It seemed paradoxically that the amplitude of action myogram increased in proportion to the grade of lowering of muscular strength caused by muscular fatigue or pain.

Adult↗
PubMed1995

Electromyographic analysis of the hip and knee during the golf swing.

As golf increases in popularity, more golfers seek the proper mechanics necessary for the perfect golf swing. Surprisingly little scientific work has been published on the contribution of the hip and knee muscles during the golf swing even though most professionals have recognized their vital contribution. Recent studies have described the electromyographic (EMG) muscle activity of the shoulder, back, and trunk during the golf swing. The purpose of this study was to describe the electrical muscle activity in seven hip and knee muscles of both the left (lead) and right (trail) leg in competitive golfers while performing the golf swing. Sixteen golfers were studied with indwelling electrodes and high-speed cinematography. The EMG was synchronized with the film to discern five phases of the golf swing. Means, SDs, and t-tests were done. The results revealed that the trail hip extensors and abductors in conjunction with the lead adductor magus initiated pelvic rotation during forward swing. The lead hamstrings maintained a flexed knee and provided a stable base on which pelvic rotation took place. The peak EMG muscle activity recorded in the hips and knees occurred in an earlier phase than that measured previously in the trunk and shoulder. This confirmed the sequential firing pattern of the hip and knee muscles that takes place during the competitive golf swing. Information gained from this study can be used by players and coaches to optimize performance and to minimize injury.

Adult↗
PubMedDate not supplied

[The effect of space flight factors on the intact and regenerating skeletal muscles of the extremities in newts].

The influence of space flight factors on the structure of two skeletal muscles of the hindlimbs was studied in newts. Degenerative-atrophic changes took place in the both muscles of the flight group animals. Comparative-quantitative analysis of ultrastructural changes of the muscle tissue has shown that after space flight, the rate of structural defects of the muscle was twice that in animals of the synchronous and laboratory control groups. But these changes were reversible: within 10 days, the structure of the muscle fibers was practically normalized. The influence of space flight on repair regeneration of the hindlimb skeletal muscle was also studied: the muscle was minced and placed back in its bed 14 days before the flight. Under these conditions, the repair regeneration of the muscle was not suppressed, but a trend towards its delay was found.

Animals↗
PubMed2004

Impaired trunk muscle function in sub-acute neck pain: etiologic in the subsequent development of low back pain?

Low back pain (LBP) and neck pain are associated with dysfunction of the trunk and neck muscles, respectively, and may involve common or similar mechanisms. In both cases, dysfunction may compromise spinal control. Anecdotally, neck pain patients commonly develop LBP. This study investigated the possibility that trunk muscle function is compromised in neck pain patients and that compromised trunk muscle function is associated with increased risk of LBP. Fifty-four neck pain patients and 52 controls were assessed on an abdominal drawing-in task (ADIT) and on self-report tests. Performance on the ADIT was able to detect neck pain patients with 85% sensitivity and 73% specificity. Catastrophizing and McGill pain questionnaire (affective) scores were higher in patients with an abnormal task response than in patients with an uncertain or normal response, although the self-report data did not predict task performance. Fifty subjects from each group were contactable by telephone at 2 years. They were asked whether they had experienced persistent or recurrent LBP since the assessment. Subjects (patients and controls) who obtained an abnormal response on the ADIT were 3 to 6 times more likely to develop persistent or recurrent LBP than those who obtained an uncertain or normal response. ADIT performance was the main predictor of development of LBP in patients. The results suggest that reduced voluntary trunk muscle control in neck pain patients is associated with an increased risk of developing LBP.

Abdominal Muscles↗
PubMed1993

Mandibular elevator muscles: physiology, action, and effect of dental occlusion.

In spite of differences in embryologic origin, central nervous organization, and muscle fiber distribution, the physiology and action of mandibular elevator muscles are comparable to those of skeletal muscles of the limbs, back, and shoulder. They also share the same age-, sex-, and activity-related variations of muscular strength. With respect to pathogenesis, the type of muscular performance associated with the development of fatigue, discomfort, and pain in mandibular elevators seems to be influenced by the dental occlusion. Clinical research comparing the extent of occlusal contact in patients and controls as well as epidemiologic studies have shown reduced occlusal support to be a risk factor in the development of craniomandibular disorders. In healthy subjects with full natural dentition, occlusal support in the intercuspal position generally amounts to 12-14 pairs of contacting teeth, with predominance of contact on first and second molars. The extent of occlusal contact clearly affects electric muscle activity, bite force, jaw movements, and masticatory efficiency. Neurophysiologic evidence of receptor activity and reflex interaction with the basic motor programs of craniomandibular muscles tends to indicate that the peripheral occlusal control of the elevator muscles is provided by feedback from periodontal pressoreceptors. With stable intercuspal support, especially from posterior teeth, elevator muscles are activated strongly during biting and chewing with a high degree of force and masticatory efficiency, and with relatively short contractions, allowing for pauses. These variables of muscle contraction seem, in general, to strengthen the muscles and prevent discomfort. Therefore, occlusal stability keeps the muscles fit, and enables the masticatory system to meet its functional demands.

Dental Occlusion↗
PubMed1992

Long-term survival of autologous muscle grafts in rat brain.

The ability of muscle to persist in the brain was explored. Pieces of rat quadriceps muscles were removed, minced and transplanted back into the same animal's cortex. Brains implanted with minced muscle consistently contained substantial grafts for at least 6 months. Histological, immunohistochemical, and electron microscopic examination indicated that the muscle grafts after 6 months contained healthy and well-differentiated myofibers. The long-term survival of muscle cells suggested that this technique will be useful for studies of brain and muscle and for the development of new therapeutic modalities.

Animals↗
PubMed2001

Effect of soft lumbar support belt on abdominal oblique muscle activity in nonimpaired adults during squat lifting.

STUDY DESIGN: A counterbalanced repeated measures design. OBJECTIVE: To determine the effect of a soft lumbar support on abdominal oblique muscle electromyography (EMG) during lifting. BACKGROUND: Use of a soft lumbar back support is a common preventive measure to reduce the incidence of back injuries. Because the abdominal oblique muscles stabilize the spine during lifting, wearing this support may alter the activity level of these muscles. METHODS AND MEASURES: Twenty nonimpaired subjects (14 women and 6 men, mean age 28.9 +/- 8.1 years) were tested using surface electrodes to record the EMG of the right abdominal oblique muscles during lifting with and without the support. RESULTS: A paired t test revealed a significant decrease in activity of the abdominal oblique muscles during lifting with the support (29.7 +/- 3.13 mV) compared to without it (33.3 +/- 3.05 mV). Of the 20 subjects, the 14 women showed decreased EMG amplitude during the lift with the lumbar support compared to without the support, while 5 of the men showed increased EMG amplitude with the support and 1 man showed no change. CONCLUSION: This finding suggests that the soft lumbar support may play some role in the stabilization of the lumbar region during lifting.

Abdominal Muscles↗
PubMed1996

Structural recovery of small arteries following clamp injury: a light and electron microscopic investigation in the rat.

Endothelial injuries were induced in the left common iliac arteries (1 mm in diameter) of rats, by the placement of 1 mm Scovell-Lewis microvascular clamps for 5 minutes, to create a lesion in which to quantitate the rate and degree of cellular regeneration. The left (clamp-injured) and right (control) iliac arteries from the 15 rats used in this study were viewed with the electron microscope at 2, 7, and 14 days after clamping, and the clamp sites were analysed morphometrically. At 2 days there was only minimal denudation of the endothelium; most cells were disoriented and showed some signs of traumatic injury. By 7 days there was a completely continuous endothelial lining, but there was also evidence of increased cytoplasmic activity in these cells, as well as a statistically significant simplification in their intercellular junctional morphology. These changes persisted at 14 days after injury, but they were less pronounced. Smooth muscle cells in the media were relatively unaffected by the trauma in the first 2 days after clamping. However, they exhibited a change of phenotype from contractile to synthetic by 7 days after injury. By 14 days most smooth muscle cells had reverted back to the contractile phenotype, with little evidence of residual damage. These studies reveal that the reconstitution and regeneration of the endothelium is very rapid following clamp injury, but that significant residual ultrastructural changes in the interendothelial junctions persist for at least 14 days after injury. These findings indicate that there is potential for subsequent pathological changes in sites of vascular clamp injury.

Animals↗
PubMedDate not supplied

Long-term results of hang-back lateral rectus recession.

PURPOSE: To report long-term results of the hang-back technique for lateral rectus muscle recession. PATIENTS AND METHODS: The medical records of 79 consecutive patients who underwent unilateral or bilateral hang-back lateral rectus recession were reviewed. The amount of surgery performed was based on the distance exotropic deviation. Surgical outcomes were analyzed for all patients included in the study. RESULTS: Forty-two patients met the inclusion criteria. Four of the patients were not orthophoric: three had recurrent exotropia and one had a consecutive esotropia. The average interval prior to the second procedure was 9 months. CONCLUSION: The hang-back technique is a safe and effective alternative to conventional lateral rectus recession.

Adolescent↗
PubMed2005

Health related quality of life after lumbar disc surgery: a prospective study of 145 patients.

PURPOSE: This study compared health related quality of life (HRQOL) among lumber disc surgery patients to general population, and assessed the relationships between HRQOL and other outcome measures 2 and 14 months after surgery. METHODS: The 15D instrument was use to measure HRQOL in 145 lumber disk surgery patients. Subjective outcome was also assessed by the Oswestry index, Short Depression Inventory (SDI) and pain, and objective outcome by trunk muscle strength and mobility of the spine. RESULTS: The mean (SD) 15D score among the patients 2 months after surgery was 0.880 (0.104) compared to 0.941 (0.076) among general population (p = 0.016). The 15D, Oswestry and SDI scores remained unchanged during the follow-up, while the improvements in the spine mobility and trunk muscle strength were significant. Back pain decreased by 68% and leg pain by 74% from preoperative level to 2 months check-up. Leg pain further decreased during the following 12 months, while back pain remained unchanged. HRQOL was associated with age, pain, Oswestry and SDI indices, but not with physical function. CONCLUSION: HRQOL measured by 15D was lower in lumber disc surgery patients compared to general population. 15D was associated with the subjective outcome measures of pain, Oswestry and SDI indices, but not with the objective measures of physical function. Thus, a combination of "disease specific" and "generic" measures is recommended to be used to obtain more accurate information about the overall welfare of individual.

Abdominal Muscles↗
PubMed1988

Long-latency stretch reflexes as co-ordinated functional responses in man.

1. Reflex activity in human arm muscles has been measured in response to torque perturbations around the elbow joint in the flexion-extension direction and/or the supination-pronation direction. Intramuscular fine-wire electrodes were used to record electromyographic (EMG) activity in the muscles. A pre-load was applied in the same direction as or in a different direction to the perturbation. The subjects were instructed to 'hold on', which means that they had to actively resist the perturbation without unduly co-activating their muscles. 2. The EMG activity showed segmented reflex responses with short-latency (25-50 ms) and long-latency (50-75 ms) components, followed by other bursts of activity which probably originated from the subject's voluntary or triggered reactions. 3. Motor units in m. triceps gave short-latency and long-latency responses to imposed elbow extension but only long-latency responses were seen to imposed pronation, which does not stretch m. triceps. Motor units in m. brachialis gave short-latency and long-latency excitatory (inhibitory) responses to imposed extension (flexion) torques. However, only long-latency inhibitory responses were observed to imposed pronation torques. Motor units in m. biceps gave short-latency and long-latency excitatory responses to imposed pronation torques. 4. These results show that the long-latency reflex cannot be the result of a simple feed-back mechanism that controls muscle length only. We argue that the long-latency reflex activity reflects the co-ordinated activation of muscles which is necessary for an adequate response. This hypothesis is supported by the fact that the distribution of long-latency reflex activity over muscles was found to be similar to the distribution of activation found during a voluntary exerted torque in the direction opposite to the applied perturbation.

Action Potentials↗