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At least 361 records · Page 20Linked to original sources
PubMed2001

Ultrastructural changes in paravertebral muscles associated with degenerative spondylolisthesis.

STUDY DESIGN: The paravertebral muscle of 30 patients with spondylolisthesis and 30 control patients were investigated histologically. OBJECTIVE: To propose myopathologic paravertebral muscle changes in cases of degenerative lumbar spondylolisthesis. SUMMARY OF BACKGROUND DATA: The stability of the vertebral column is based on both active and passive systems. The passive system is composed of the vertebrae, the intervertebral discs, and the ligaments. Surrounding muscles and tendons constitute the active system. The autochthonous back muscles take over support functions if the passive system is ineffective. In some cases, muscles are overstrained for a long period, ultimately leading to muscular changes. This study was performed to determine the histopathologic correlates of this permanent strain. METHODS: Between July 1998 and July 1999, paravertebral muscle biopsies were performed for 30 patients with monosegmental degenerative spondylolisthesis undergoing posterior lumbar interbody fusion. The tissue samples were submitted to histologic analysis including immune and enzyme histochemistry and electron microscopy. In addition, the muscle fibers were submitted to morphometry. RESULTS: Severe pathologic alterations were found. The findings showed that 22 patients (73.3%) had ragged red fibers with evident ultrastructural mitochondrial anomalies. The cristae appeared irregular in 12 patients (40%) Type 1 paracrystalline inclusions were detected in five samples (16.6%) and dense bodies in eight (26.6%). Fibers with ubiquitin-positive inclusions were detected by immunohistochemistry in 13 patients (43.3%). As shown by the electron microscope, these corresponded to granulofilamentous inclusions and polyglucosan bodies. The samples were submitted to genetical analysis because biochemical studies showed reduced activity of the respiratory chain enzymes. Normal mitochondrial deoxyribonucleic acids of unchanged length were detected. CONCLUSIONS: Apart from nonspecific myopathic changes such as those observed in rimmed vacuoles and rods, increased numbers of polyglucosan bodies were detected. This increase in polyglucosan bodies currently has not been described in patients with otherwise normal muscles.

Adult↗
PubMed2005

The impact of seatback angle on electromyographical activity of the lower back and quadriceps muscles during bilateral knee extension.

This study investigated variations in electromyographic (EMG) responses of the erector spinae (ES), vastus medialis (VM), rectus femoris (RF), and vastus lateralis (VL) to different seatback angles during leg extension. Twenty men and women (10 men, 10 women; age 27.49 +/- 6.16 years) performed 8 repetitions at 70% of 8 repetition maximum at seatback angles of 1.57, 1.75, and 1.92 radius (rad). Analyses using repeated-measures analysis of variance indicated the greatest root square mean of the EMG (rmsEMG) and integrated EMG (intEMG) for the ES were at 1.92 rad, and the greatest for the VM (concentric) and VL (eccentric) were at 1.57 rad. No differences were observed among seat angles for the RF except for a higher normalized intEMG at 1.92 than 1.75 rad (concentric). Throughout all sets for all conditions and muscles, rmsEMG and intEMG significantly increased and median power frequency significantly decreased. These data indicate that a seatback angle of 1.57 rad is best for a leg extension machine, because this angle maximizes quadriceps activity while minimizing stress on the lower back muscles.

Adult↗
PubMed2006

An on-body personal lift augmentation device (PLAD) reduces EMG amplitude of erector spinae during lifting tasks.

BACKGROUND: A new on-body personal lift augmentation device was developed to support the back muscles during the repetitive lifting task. METHODS: Nine male subjects participated in the study. Three Fastrak units were used to record positions and rotations of the segments. Trunk muscle normalized and integrated electromyography of the left and right thoracic erector spinae, lumbar erector spinae, external obliques, and rectus abdominis, as well as the kinematic variables of peak lumbar angle, peak pelvis angle, peak trunk acceleration, peak load acceleration were compared in symmetrical lifting for three different loads (5 kg, 15 kg, 25 kg) with three different styles (stooped, squat, free) under two conditions of with and without personal lift assist device. FINDINGS: The lift assist device significantly reduced the required muscular effort of the lumbar (p = 0.001) and thoracic erector spinae with no significant differences in the level of abdominal muscle activity. The amount of integrated electromyography reduction ranged from 14.4% to 27.6% for the lumbar and thoracic erector spinae respectively. Simple measures of trunk posture and accelerations confirmed that there were no differences in lifting technique that would cause the integrated electromyography activity to be reduced. No major kinematic differences were found when the lift assist device was worn indicating that it did not alter these specific technique variables. INTERPRETATION: The lift assist device did reduce the required muscular effort of the lumbar and thoracic erector spinae without adversely affecting the level of abdominal muscle activity. This reduction may help reduce the risk of recurring back injuries or assist in the return to work phase, especially in repetitive tasks.

Adult↗
PubMed1984

Steroid hormone receptors, protein, and DNA in erector spinae muscle from scoliotic patients.

To investigate the possible influence of steroid hormones on the back muscles of scoliotic patients, steroid receptors, protein, and DNA were analyzed in muscle from 20 patients of both sexes, at different ages, and with different clinical diagnoses. Androgen and glucocorticoid receptors, but no estrogen receptors, were found. The androgen and glucocorticoid receptors had binding characteristics similar to those of corresponding receptors in other mammalian skeletal muscle, including that of humans. Whereas the concentration of androgen receptors was similar on both sides of the curve, the concentration of glucocorticoid receptors per gram of tissue (wet weight) was higher on the convex side. There were no side differences in steroid receptor content when measured per milligram of protein or per milligram of DNA. The concentrations of protein and DNA were higher on the convex than on the concave side and resulted in lower protein/DNA ratios on the former side indicating smaller "cell units" in muscle on the convex side. These data suggest that the side differences in scoliotic erector spinae muscle for these growth parameters can be secondary to the reported different distribution of fiber types on both sides, but they can also be due to a difference in growth of the muscle cells on the two sides.

Adolescent↗
PubMed1994

Some differences of the electromyographic erector spinae activity between normal subjects and low back pain patients during the generation of isometric trunk torque.

A method of evaluation of the isometric trunk extension effort and integrated electromyographic activity of the low back muscles during straight position under goniometric control was used. In order to evaluate the paravertebral muscle activity, two pairs of bipolar surface EMG electrodes have been attached bilaterally over the erector spinae muscles at a lateral distance of 3 cm at the level of L3 spinal processus. 40 patients with low back pain and 40 normals were involved to participate in this study. EMG activity and strength was higher in normals than in patients. However, this distinction was statistical significant in strength, and nonsignificant in EMG activity. Patients showed relatively higher, asymmetric and more expressive in the painful side integrated electromyographic activity under maximal and submaximal contraction. Strength/EMS relationship was close to linear in normals, whereas in patients this proportionality was nonlinear. Therefore in patients a smaller tension correlated with relatively higher muscle activity.

Adult↗
PubMedDate not supplied

Mechanical back pain and the facet joint syndrome.

Mechanical back pain is a common disability often associated with the facet joint syndrome. Treatment is based on early, adequate pain relief with simple techniques of regional analgesia. In a few cases this is not enough and more sophisticated methods, such as radiofrequency denervation, cryo-analgesia and possibly intrathecal midazolam, are necessary. However, the main thrust of our approach is to treat the underlying structural disorder with strengthening of the back muscles and correction of postural abnormalities responsible for the mechanical back pain. Our report is based on an analysis of 83 patients who failed to respond to long periods of rest, suitable analgesic and allied drugs and other non-invasive measures. There had been no overriding indication for major surgery. A large number of these patients have been improved by our methods, but further work is in progress to extend the proportion of satisfactory results.

Analgesia↗
PubMedDate not supplied

Neurophysiology of orthostatic tremor. Influence of transcranial magnetic stimulation.

A 74-year-old patient suffers from painful muscle cramps when he stands since 30 years. He has no visible tremor but 16 Hz burst activity on EMG, indicating orthostatic tremor. Previous diagnosis was hysteria, stiff person syndrome or dystonia. This shows that EMG during standing should be part of the examination of patients with stiff muscles or muscle cramps. Tremor was not strictly orthostatic. It appeared in back muscles while sitting, when the patient supported a weight with outstretched arms. Phase between muscles differed between normal standing and standing on heels. Subthreshold transcranial magnetic stimulation modulated timing of the tremor bursts and inhibited them at higher intensity stimulation.

Aged↗
PubMed1999

Kinematics of the equine back: flexion-extension movements in sound trotting horses.

This study was undertaken to evaluate the flexion-extension movements of the back in a group of sound trotting horses. Using a 3-D kinematic analysis system, 13 clinically sound horses fitted with 5 skin markers placed on the dorsal midline of their trunk were recorded while trotting on a track in the conditions of the routine lameness examination. These markers were used to calculate 3 back angles (thoracic, thoracolumbar and lumbosacral angle). These back angles were then filtered using Fourier series. To evaluate the repeatability of flexion-extension movements, the intra- and inter-individual variabilities were studied. The angle-time diagrams showed that the equine back extended during the first part of each diagonal stance phase and flexed during the second part of each diagonal stance phase. The ranges of motion were less than 4 degrees for the 3 back angles. The intra- and inter-individual variability values of maximal extension and maximal flexion time points were similar and extremely low. This demonstrates the high repeatability of the temporal pattern of flexion-extension movements of the back. Intra- and inter-individual variabilities of the range of motion showed that the back mobility varies more in-between horses than between trials of the same horse. Compared with electromyographic activities of back muscles reported in the literature, flexion-extension movements described in this study tend to show that, at a slow trot, trunk muscles act mainly to limit flexion-extension movements of the back rather than to induce movements.

Animals↗
PubMed1998

Influence of muscle forces on loads in internal spinal fixation devices.

STUDY DESIGN: The loads acting on an internal spinal fixation device were measured in vivo. OBJECTIVES: To determine the influence of muscle forces on implant loads. SUMMARY OF BACKGROUND DATA: Only limited information exists regarding the loads acting on spinal implants in vivo. Though the muscles greatly influence spinal load, they have been neglected in most studies. METHODS: Telemeterized internal spinal fixation devices were used to study the influence of muscle forces on the implant loads in three patients before and after anterior interbody fusion. RESULTS: Contracting abdominal or back muscles in a lying position was found to significantly increase implant loads. Hanging by the hands from wall bars as well as balancing with the hands on parallel bars reduced the implant loads compared with standing; however, hanging by the feet with the head upside down did not reduce implant loads compared with lying in a supine position. When lying on an operating table with only the foot end lowered so that the hips were bent, the patient had different load measurements in the conscious and anesthetized state before anterior interbody fusion. The anesthetized patient evidenced predominately extension moments in both fixators, whereas flexion moments were observed in the right fixator of the conscious patient. After anterior interbody fusion had occurred, the differences in implant loads resulting from anesthesia were small. CONCLUSIONS: The muscles greatly influence implant loads. They prevent an axial tensile load on the spine when part of the body weight is pulling, e.g., when the patient is hanging by his hands or feet. The implant loads may be strongly altered when the patient is under anesthesia.

Abdominal Muscles↗
PubMed1998

The effects of video display terminal height on the operator: a comparison of the 15 degree and 40 degree recommendations.

Prolonged use of video display terminals (VDTs) has been shown to be a risk factor for musculoskeletal and visual discomfort. A standard workplace design recommendation is to position the centre of the VDT 15 degrees below horizontal eye level. Recently a viewing angle of 40 degrees below horizontal has been suggested based on studies that have indicated that this is the preferred viewing angle for visually intensive tasks. The goal of this study was to investigate the effects of these two VDT positions on muscular activity, muscular fatigue, head/neck posture, visual acuity, operator performance (productivity and quality), heart rate and operator subjective assessment. The experimental task consisted of reading text from a computer screen and answering reading comprehension questions using a mouse and a keyboard. Each experimental session lasted 2 h. The 40 degree VDT position showed significantly greater head tilt angles and higher muscle activity levels for six of the 10 neck, shoulder and back muscles sampled. No significant differences in visual acuity, operator performance or heart rate were detected as a result of monitor location. Seven of the 12 subjects preferred the 15 degree monitor position.

Adult↗
PubMed1997

Electrokinesiologic measurement of trunk sagittal mobility and lumbar erector spinae muscle activity.

Additional studies to determine intratester reliability of electrokinesiologic (EK) measures related to trunk movement and low back muscle activity are needed. EMG activity and EK records of repetitive movements at both natural and maximal speeds were computer sampled and quantified among 22 nonimpaired subjects. Significant differences were observed between group means at different speeds and trials for both kinematic and EMG measures. Predictably, maximal speed testing resulted in higher levels of EMG activity when compared to natural speed testing. Intratester reliability of measures was high at both speeds. Range of motion data correlated well between two trials for both natural and maximal speed movements, ranging from 0.81 to 0.97. Correlation of speed of movement measures ranged from 0.41 to 0.76. These data suggest that computer-analyzed EMG activity and EK signals are reliable assessment tools for trunk mobility. The application of this procedure to persons with low back pain to acquire EMG activity and mobility data appears justified.

Adolescent↗
PubMed1981

Distribution of acetylcholinesterase molecular forms in brain, nerve and muscle tissue of Torpedo marmorata.

The distribution of multiple molecular esterase forms in brain, electromotor nerve, back muscle and a subcellular synaptosomal fraction from the electric organ of Torpedo marmorata was investigated. Each tissue was characterized by a specific pattern of distribution of esterase forms. Electric lobe exhibited a marked difference to the other brain tissues and electric organ, in that it contained predominantly fast sedimenting 17 S acetylcholinesterase. The solubilization properties indicated that the 17 S form is not exclusively associated with basal lamina. The results support the view that location and function of the various molecular esterase forms can vary from tissue and depend on the physiological demands of each system.

Acetylcholinesterase↗
PubMed1994

[A case of painful involuntary contraction of the left latissimus dorsi muscle, successfully treated with left thoracodorsal nerve resection].

A 66-year-old Japanese man underwent the resection of the upper lobe of the left lung for primary lung cancer. One year later, his back muscles neighboring the operation scar gradually began to twitch upwards intermittently. The involuntary muscle twitch was accompanied with severe local pain, and intensity of the pain and contraction slowly increased. The abnormal muscle contractions were confined to the left latissimus dorsi muscle on needle EMG. The pain and movement ceased by blocking of either thoracodorsal nerve or brachial plexus, and disappeared finally by resection of the nerve. The impulses causing involuntary, painful contractions were thought to originate in the damaged thoracodorsal nerve, transmitted to CNS and re-transmitted to the thoracodorsal nerve.

Aged↗
PubMed1997

Lumbar paraspinal muscle fatigability in repetitive isoinertial loading: EMG spectral indices, Borg scale and endurance time.

The purpose of this study was to develop a submaximal repetitive isoinertial back muscle endurance test by defining the relationships between the power spectral indices of paraspinal muscle electromyographic (EMG) activities, endurance time and a subjective estimate of fatigue (Borg scale). Bilateral surface EMG recordings were obtained over the lumbar paraspinal muscles in ten individuals who were currently free from back pain. All subjects performed repetitive upper trunk extensions (25 degrees flexion and 5 degrees extension, 30 repetitions per min), while movement below the third lumbar vertebral body was mechanically restricted. The load level depended upon upper body mass, sex, and age. The tests continued for as long as the subjects were able to maintain the required repetition rate (endurance time). Median (MF) and mean power frequency (MPF) slopes were calculated by performing a fast Fourier transformation after confirmation of EMG stationarity by recurrence quantification analysis. MF and MPF correlations with endurance time/Borg scale were measured for the first 60 s (0.60-0.88/0.42-0.86), the first 90 s (0.62-0.89/0.52-0.90), the first 120 s (0.50-0.76/0.41-0.73), and the entire repetitive run (0.63-0.88/0.54-0.90). To test for the reproducibility of the spectral indices EMGs were recorded for 2 min during repetitive loading from the same subjects on two consecutive days. Corresponding spectral slopes of MF and MPF were correlated at 60 s (0.36-0.93), 90 s (0.58-0.92), and 120 s (0.70-0.94) at the L3-L4 and L5-S1 levels, indicating good reproducibility of results from alternate recording sessions at the L5-S1 level. It is concluded that paraspinal muscle spectral indices (MF and MPF) measured before the onset of total muscle fatigue are good predictors of endurance time and are closely related to the subjective perception of fatigue.

Adult↗
PubMed2003

Sitting with adjustable ischial and back supports: biomechanical changes.

STUDY DESIGN: The seat and back contact force, pressure distribution, lumbar lordosis, and low back muscle activities associated with a new seat design with adjustable ischial support and backrest were investigated using kinematic, kinetic, electromyographic, and radiographic measurements. OBJECTIVES: To investigate the biomechanical effects of adjusting ischial and backrest supports during sitting. SUMMARY OF THE BACKGROUND DATA: Sitting may induce posterior rotation of the pelvis, reduction of lumbar lordosis, and increases in muscle tension, disc pressure, and pressure on the ischium and coccyx, which may be associated with low back pain. A device that reduces the ischial load and maintains lumbar lordosis may help increase seating comfort and reduce low back pain. METHODS: Fifteen office workers with no known low back pain history were tested. Contact pressure distributions, reaction forces between the buttock-thighs and seat and between the back and backrest, load carried by the seat pan and backrest, sacral inclination, lumbar lordosis, intervertebral space of lumbar spine, and muscular activity in stabilizing the trunk were measured for sitting with and without ischial support and with adjustable back support. RESULTS: When the ischial support was relieved, the center of the force on the seat and on the legs of the chair, and the peak center of pressure on the seat, were significantly (P < 0.002) shifted forward toward the thighs. The total contact area on the seat pan and on the backrest was significantly decreased and increased, respectively (P < 0.001). The sacral inclination, total and segmental lumbar lordosis, and lumbar spine disc height were significantly increased for sitting upright with backrest, with the lumbar curve close to that during standing. CONCLUSIONS: Sitting with reduced ischial support and fitted backrest to the lower spine altered the contact area, reduced peak pressure under the ischia, reduced muscular activity, maintained total and segmental lumbar lordosis, rotated the sacrum forward, and increased lumbar intervertebral disc heights, which could potentially reduce low back pain.

Adult↗
PubMedDate not supplied

Differences in low back load between kneeling and seated working at ground level.

The effects of the load on the low back when working in a kneeling posture were compared to those when working on a chair designed to alleviate work load in harvesting radish. In 10 male subjects data regarding back muscle fatigue and length changes of the spine, and estimates of experienced discomfort were collected. The results show that for all three effects of back load working on the chair leads to lower levels as compared to working kneeling. However, back load and discomfort were lower when working on the chair, back discomfort still increased substantially during the work on the chair. It is thus a sub-optimal solution from an ergonomic point of view, but at present it could be recommended to allow for variation with the conventional working method.

Adult↗