PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Back Muscles”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1993

The axial torque of the lumbar back muscles: torsion strength of the back muscles.

The maximal, axial torque generated by the lumbar back muscles was determined by modelling the action of the 49 fascicles of longissimus thoracis, iliocostalis lumborum and the lumbar multifidus on radiographs of the lumbar spine of nine young male subjects in upright standing and in full lumbar flexion. No single fascicle exerted more than 2 Nm of axial torque in the upright posture, and the collective torque of all muscles acting a segment did not exceed 5 Nm. All torques were considerably less in full flexion. The lumbar back muscles exert very little torque on the lumbar spine, and contribute only about 5% of the total torque involved in trunk rotation. None of the lumbar back muscles can be considered a rotator. The oblique abdominal muscles are the principal rotators of the trunk. Preventative and rehabilitation programmes concerned with torsion injuries should focus on the abdominal muscles rather than the back muscles for stability in axial rotation.

Back↗
PubMed1996

Back muscle injury after posterior lumbar spine surgery. Topographic evaluation of intramuscular pressure and blood flow in the porcine back muscle during surgery.

STUDY DESIGN: Intramuscular pressure and blood flow of the back muscles were evaluated topographically during posterior lumbar spine surgery. The topographic damage of the back muscle after surgery was studied. OBJECTIVE: To investigate the relationship between intramuscular pressure or blood flow during posterior lumbar surgery and the back muscle injury after surgery. SUMMARY OF BACKGROUND DATA: Latrogenic back muscle injury in an animal and human model has been reported previously. Changes of intramuscular pressure and blood flow during surgery might be related to the muscle injury. No previous study on this issue has been published. METHODS: The contact pressure between the retractor blade and muscle tissue was monitored in 10 pigs during posterior surgery of the lumbar spine. On one side, intramuscular pressure at 5, 10, and 20 mm lateral to the retractor and on the other side blood flow of the back muscle at 5 and 20 mm during surgery were measured. Histologic changes of the back muscle at 5, 10, and 20 mm to the midline were evaluated 3 hours after surgery. RESULTS: The contact pressure decreased exponentially with time. Intramuscular pressure 5 mm lateral to the retractor was 114 +/- 31 mm Hg and was significantly higher than at 10 mm and 20 mm. Blood flow markedly decreased during surgery and recovered incompletely after releasing the retractor at 5 mm and 20 mm lateral to the retractor. Blood flow at 5 mm was significantly lower than at 20 mm throughout surgery. The muscle damage 3 hours after surgery was more severe near the retractor blade. CONCLUSIONS: The back muscles were exposed to pathophysiologic condition by a retractor during posterior lumbar spine surgery. External compression by a retractor increases intramuscular pressure to levels that impede local muscle blood flow. The muscle degeneration after surgery could be explained by direct mechanical damage and by the increased intramuscular pressure of muscle tissue by the retractor.

Animals↗
PubMed2001

Evaluation of the EMG activity of the long back muscle during induced back movements at stance.

In this study we investigated the activity of the main back muscle (Musculus longissimus) by surface electromyography (EMG) during induced extension and lateral flexion at stance. Measurements were taken of 15 horses (age 5-20 years, 450-700 kg bwt) without signs of back pain. Reflecting markers were placed on the head, spinous processes of T5, T12, T16, L3 and on 2 of the sacral bones. The surface EMG electrodes were situated on the Musculus longissimus on both sides of the dorsal spinous processes of T12, T16 and L3. In all horses and all movements (extension, lateral flexion to the left and right), the EMG on both sides of the dorsal spinous process of T12 had the highest, and the EMG on both sides of the spinous process of L3, the lowest amplitude (30% of T12). At T16 the amplitude of the EMG signal was 60% of that at T12. There was no time shift between the EMG signals at the different locations (T12, T16, L3). There was a very high correlation between motion and amplitude of the EMG signal of extension, with correlation coefficients of 0.78 at L3, 0.80 at T16 and 0.75 at T12. The correlation of the lateral flexion between amplitude of the EMG and motion was lower, with 0.38 at L3, 0.43 at T16 and 0.39 at T12. This investigation showed that the EMG of the Musculus longissimus during spinal reflexes should be derived on both sides of T12, because this is important for the clinical use of surface EMG.

Animals↗
PubMed1992

Trunk muscle strength and back muscle endurance in construction workers with and without low back disorders.

The aim of this study was to test the hypothesis that male workers exposed to heavy work and with no lifetime history of a low back disorder (group A) have better trunk muscle strength and back muscle endurance compared to male workers with the same work exposure but with a probable (group B) or definite low back disorder (group C). Group A (n = 42) was clinically negative on physical examination. Group B (n = 75) was clinically negative or uncertain and group C (n = 86) was clinically positive, with current or previous low back disorders occurring in both groups. Group A had a significantly higher mean intraindividual extension/flexion ratio, namely 1.29 versus 1.19, in group C. The mean values for maximum isometric trunk extension and flexion strength did not differ between the groups. The isometric trunk extensor endurance was significantly lower in group C than in both group A and group B.

Adult↗
PubMed1998

Relationship between muscle fiber composition and functional capacity of back muscles in healthy subjects and patients with back pain.

Back muscles are important to the stability of the lumbar spine. Muscle fiber composition may give some indication of the functional capacity of these muscles. This review explores the relationship between muscle fiber composition and functional capacity of back muscles. The reference values for the type and size of the muscle fibers found in the back musculature of healthy subjects and patients with back pain are also presented. A high percentage of type I fibers, which are larger in size than type II fibers, has been found in back muscles at the thoracic and lumbar levels. This is in accordance with the postural function of these muscles. The diameter of type II fibers is smaller in females than males, which may partly explain the lesser strength and greater endurance capacity of back muscles in females. Due to the limited amount of pertinent data, no conclusive evidence is available regarding age-related changes in muscle fiber composition in the musculature of the back. In patients with lumbar disorders, pathological changes and selective atrophy of type II fibers are seen, and these can be changed with adequate exercises. Further research is suggested to address issues related to gender, age, back pain, and exercise and their effects on the apparent back muscle fiber composition.

Aging↗
PubMed1995

Spectral electromyographic assessment of back muscles in patients with low back pain undergoing rehabilitation.

STUDY DESIGN: A surface electromyographic procedure for evaluating back muscle impairment was studied in patients undergoing rehabilitation for low back pain. OBJECTIVES: The results were analyzed to determine whether the electromyographic procedure was able to: 1) distinguish muscle impairment between patients with low back pain and normal subjects, and 2) monitor changes in muscle function after low back pain rehabilitation. METHODS: Patients with chronic low back pain (n = 85) were tested to measure the median frequency of the electromyographic signals from six lumbar electrode sites during sustained trunk extensions. A subset (n = 28) of these patients was re-tested after low back pain rehabilitation. A discriminant function for classifying subjects into "low back pain" and "normal" groups was formulated using the electromyographic data from a subset of the patients with low back pain (n = 28) and a normative sample (n = 42). Results for this "learning" sample were compared with results using the same function on the remaining "holdout" sample of patients (n = 57) and an additional normative sample (n = 6). Differences in electromyographic parameters before and after rehabilitation also were analyzed. RESULTS: The discriminant function classified subjects into low back pain and normal groups, with 86% and 89% correct classification for the "learning" and "holdout" samples, respectively. These classification results were independent of trunk extensor strength. Changes in median frequency after the rehabilitation program were consistent with improvements in back muscle fatigability. CONCLUSION: These findings demonstrate how electromyographic spectral measurements may be used to identify and monitor back muscle impairment in patients undergoing rehabilitation for low back pain.

Adult↗
PubMed2000

Influence of age and duration of symptoms on fibre type distribution and size of the back muscles in chronic low back pain patients.

Many studies have documented an association between chronic low back pain (LBP) and deficits in back muscle strength and endurance. The sub-optimal performance is believed to be the result of alterations in the size and structure of the muscle, although the long-standing issue of whether the observed changes precede or are a consequence of the pain remains unresolved. If consequent to the problem, and predominantly related to disuse of the muscles, then it may be expected that a relationship between muscle structure and symptom duration would exist. Lumbar paraspinal muscle samples were obtained from 59 chronic LBP patients using the percutaneous biopsy technique. The samples were subject to routine histochemical analysis for the examination of muscle fibre type characteristics and cytochemical architectural changes. In 55 of the patients, the gross cross-sectional areas of magnetic resonance images of the trunk muscles were also measured. Multivariate analysis showed that symptom duration was the strongest predictor of the individual proportions of the fast-fatigable type IIX fibres; with age and gender included in the model, nearly 30% of the variance in fibre type distribution could be accounted for. Duration of pain had no influence on fibre size. Gross muscle cross-sectional area correlated directly with lean body mass and inversely with age, but showed no relationship with symptom duration. Pathological changes in the internal fibre structure were more frequently encountered in older patients, and were independent of symptom duration. The results suggest that, over the long term, fibre type transformations rather than alterations in fibre size are the predominant changes to be found in the muscles of chronic LBP patients. The direction of change supports the results of many previous studies that have demonstrated corresponding differences in the fatigability of the muscles. There is a strong case for the early implementation of active measures to attempt to offset the development of these changes in back pain patients.

Adult↗
PubMed1998

Functional changes in back muscle activity correlate with pain intensity and prediction of low back pain during pregnancy.

OBJECTIVE: To assess low back pain (LBP) intensity and subjective disability during pregnancy and compare the pain scores with lumbar motion patterns. DESIGN: A prospective study of pregnant back pain sufferers and healthy controls. SETTING: Kuopio University Hospital, Kuopio, Finland. PARTICIPANTS: Study group consisted of 32 pregnant women with LBP; control group consisted of 21 healthy pregnant women. MAIN OUTCOME MEASURES: Back pain intensity was assessed by visual analog scale (VAS), and subjective disability index was measured by Oswestry Low Back Disability Questionnaire, at 20 and 36 weeks of pregnancy. Back muscle activities were recorded by surface electromyography, and movement sensors were used to detect lumbar motion. RESULTS: In the study group current pain scores (VAS) at first and last trimester correlated strongly (r = .82, p < .00). Pain scores correlated with body weight at the first trimester (r = .54, p = .003) and at the last trimester (r = .67, p < .00). Significant correlation was noted between current pain intensity and back muscle activity level during forward body flexion at first trimester (r = .704, p < .00). Back muscle activity during bending measured at first trimester significantly correlated with pain intensity at last trimester (r = .703, p < .00). Back muscle activity during the first trimester of pregnancy had a negative correlation with current (r = -.57, p = .002) and later subjective disability index (r = -.42, p = .02). It correlated inversely (r = -.54, p = .003) with pain score at last trimester of pregnancy, ie, the lower the back muscle activity at the beginning of pregnancy, the more pain and disability throughout pregnancy. In the control group, three women developed LBP and disability feelings during pregnancy. They had increased muscle activity during flexion at delivery, ie, disturbed flexion relaxation. CONCLUSIONS: Prepregnancy LBP predicts renewed pain during pregnancy, and dysfunction of back muscles has been established in LBP. In this study, disturbance in the relaxation of the back muscles was linearly related to current, and also to later, pain scores. In addition, back muscle activity level was inversely related to the disability index. For the first time, it has been shown prospectively that the function pattern of back extensors seems to predict, and is related to, future back pain. Simple function testing is promising and might be valuable in identifying mothers with a high risk of pregnancy-related back pain and in directing preventive intervention to high risk women by making them aware of self-treatment methods.

Activities of Daily Living↗
PubMed1999

Predictors of isokinetic back muscle strength in patients with low back pain.

STUDY DESIGN: Testing for trunk muscle strength was performed on 105 patients with chronic low back pain. OBJECTIVES: To investigate prediction of isokinetic back muscle strength in patients with low back pain. SUMMARY OF BACKGROUND DATA: The clinical evaluation of patients with chronic low back pain often in difficult because of discrepancy between disability and impairment. The isokinetic trunk device was developed as a tool for objective assessment of back muscle strength. However, the performance of patients depends on radiologic abnormalities of the spine, conditions of the back muscles, and various psychosocial factors. Studies are warranted that address how these variables influence back muscle strength. METHODS: The patients with chronic low back pain were tested by an isokinetic trunk muscle strength test (Cybex TEF, Ronkonkoma, NY). In addition, the following variables were recorded: gender, age, body mass index, emotional distress, pain on exertion, self-efficacy for pain, degenerative changes of the lumbar spine, cross-sectional area, and density of the erector spinae muscles. The three latter variables were estimated by computed tomography scans. The sum of the total work performed during isokinetic extension strength test was the dependent variable in a multiple regression analysis, and anthropometric, demographic, psychological, and radiologic factors were independent variables. RESULTS: Gender, cross-sectional muscle area, and pain on exertion were the most powerful predictors of isokinetic back muscle strength. The final regression model, which included these variables, could account for approximately 40% of the variability in back muscle strength. CONCLUSION: For assessing the results of an isokinetic trunk muscle strength test, cross-sectional muscle area, gender, and pain on exertion should be taken into account.

Adult↗
PubMedDate not supplied

Back muscle strength and weight limits in lifting burdens.

When lifting loads, the muscles of the back, rather than the ligaments and the bony structures of the spine, should overcome the gravitational forces. Formulas, based on measurements of the back muscle strength for prediction of maximum loads to be lifted, have been worked out and tested in practical situations. From tests with 50 male and female subjects, the simplest prediction formulas for maximum loads were as follows: for men, maximum load = 1.10 X isometric back muscles strength; for women, maximum load = 0.95 x isometric back muscle strength minus 8 kg.

Adult↗
PubMed1997

Movement disturbances of the lumbar spine and abnormal back muscle electromyographic findings in recurrent low back pain.

STUDY DESIGN: A cross-sectional analysis was done of patients with recurrent low back pain referring to the lower limbs. OBJECTIVES: To analyze dynamic radiographs of forward and backward bending of the lumbar back and to determine, using routine neurophysiologic measurements, the functional state of the lower nerve roots in patients with recurrent low back pain radiating to the lower limbs. METHODS: Clinical and neurophysiologic studies showed eight of the 108 patients with low back pain to have ventral root impingement at either L5 or S1 level. The remaining 100 patients, 56 women and 44 men (mean age, 37.6 years; range, 17-62 years), made up the study group for continuing investigation. History of low back pain ranged from 4 months to 20 years. RESULTS: Disturbed intervertebral movement was found in 51 of 100 patients. Twenty-seven percent had L5 or L4 anterolisthetic hypermobility, and 35% had L4 or L3 vertebral retrolisthesis. Vaguely delineated radiating sensations in the lower limbs were common (62%). Back muscle electromyographs were mostly (86%) normal in patients whose low back pain was localized. Conversely, almost three-fourths of those experiencing radiating or referred pain had abnormal electromyographs, consistent with a mild degree of axonal damage in the posterior branch of the lumbar nerve root innervating the medial paraspinal muscles. This finding was most common among patients with retrolisthesis and simultaneous degenerative changes. CONCLUSIONS: Evaluation of low back pain should include tests for degenerative retrolisthesis, especially in patients experiencing radiating sensations with no evidence of root impingement, because abnormal electromyographic findings showing denervation of the paraspinal muscles was most common in patients with degenerative retrolisthesis. To improve the functional support of the lumbar region, rehabilitation should be directed to the medial back muscles because they provide the most effective support for intervertebral motion and because mild disturbances appear to be associated with their innervation in recurrent low back pain.

Adolescent↗
PubMed1991

Electric behavior of low back muscles during lumbar pelvic rhythm in low back pain patients and healthy controls.

UNLABELLED: The functioning of low back muscles of back pain patients during flexion and reextension has not been properly investigated. In this study, we analyzed rectified, averaged electric activity (RMS EMG) and corresponding raw intramuscular (IM) EMG from lumbar paraspinal muscles to quantify the activity level during simple bending cycles in 87 back pain patients compared to 25 able-bodied controls. THE RESULTS: All functional phases seen in raw IM EMG were also shown in surface RMS EMG. Surface RMS EMG pattern seems to yield more information from activity level than IM EMG pattern. The RMS EMG patterns of back pain patients differed from those of controls as follows: (1) There was clearly noticeable activity during standing in back pain patients. (2) There was only a partial decrease of EMG activity after flexion in back pain patients with current pain. (3) The ratio of mean reached at maximal activity level during extension and flexion was less in patients (1.8, SD = 0.5, p less than .001) than able-bodied controls (3.2, SD = 0.8). (4) Segmental differences were observed in IM EMG activities in patients having hypermobility in bending x-ray. (5) Large peak potentials occurred during movements in patients having segmental hypermobility. THE RESULTS indicate that averaged surface recording is a valuable tool in the investigation of dynamic spine functions in back pain patients.

Adult↗
PubMed2000

Magnetic resonance imaging and histologic evidence of postoperative back muscle injury in rats.

STUDY DESIGN: Postoperative back muscle injury was evaluated in rats by magnetic resonance imaging and histologic analyses. OBJECTIVE: To compare the magnetic resonance imaging manifestation of back muscle injury with the histologic findings in rats and to subsequently clarify the histopathologic appearance of the high intensity regions on T2-weighted images in human postoperative back muscles. SUMMARY OF BACKGROUND DATA: In a previous study, it was found that the signal intensity on T2-weighted images of the postoperative back muscles was increased in patients who had postsurgical lumbar muscle impairment, especially in those with a prolonged surgery duration. However, the specific histopathologic changes that cause the high signal intensity on T2-weighted images remain unclear. METHODS: Rats were divided into three groups: sham operation group, 1-hour retraction group, and 2-hour retraction group. Magnetic resonance imaging and histology of the multifidus muscles were examined before surgery and at 2, 7, and 21 days after surgery. RESULTS: T2-weighted imaging was more useful than T1-weighted imaging to estimate back muscle injury. The high signal intensity of the multifidus muscles on T2-weighted images remained 21 days after surgery only in the 2-hour retraction group. Histologically, the regeneration of the multifidus muscles was complete at 21 days after surgery in the 1-hour retraction group, but the regenerated muscle fibers in the 2-hour retraction group had a small diameter, and the extracellular fluid space remained large. CONCLUSION: The high signal intensity on T2-weighted images of the postoperative multifidus muscles in the regenerative phase may be due to an increased extracellular space and incomplete muscle fiber regeneration.

Animals↗
PubMed1990

Hypothalamic effects on medullary reticular activation of deep back muscle EMG.

Medullary reticular stimulation can activate deep back muscle EMG in urethane-anesthetized female rats. Midbrain central gray stimulation can facilitate brainstem reticular control over deep back muscles. Since these deep back muscles lateral longissimus (LL) and medial longissimus (ML) execute the vertebral dorsiflexion of lordosis behavior, and since the motor control hierarchy sketched above parallels lordosis behavior circuitry, we tested the hypothesis that medial hypothalamic lesions (which, in behavioral experiments, decrease lordosis) can also reduce medullary reticular activation of deep back muscle EMG. Urethane-anesthetized rats were tested systematically for amplitude of lateral longissimus (LL) and medial longissimus (ML) EMG responses to electrical stimulus trains applied to the nucleus gigantocellularis (NGC) of the medullary reticular formation, before and after electrolytic lesions of the ventromedial hypothalamus (n = 18) or control sites (n = 30). Bilateral ventromedial hypothalamic lesions were able to greatly reduce EMG responses in LL and ML, often with a time course similar to previous lordosis behavioral results. Surprisingly, lesions at the anterior ventromedial nucleus pole were particularly effective, and may reflect importance of intraventromedial local neurons. Although, on the average, various control lesions were less effective, the ventromedial hypothalamic effect was not unique. For example, it was possible to see an EMG decrease following lesions of the dorsomedial thalamus. Nevertheless, EMG loss was not well correlated with changes in the cortical EEG, and thus does not appear to be a simple consequence of changes in "arousal." In conclusion, it appears that ventromedial hypothalamic neurons can affect medullary reticular control of back muscle EMG, but must share this role with other forebrain elements.

Animals↗
PubMed1998

Preventive measures of back muscle injury after posterior lumbar spine surgery in rats.

STUDY DESIGN: Postoperative back muscle injury was studied in rats. Postoperative findings were compared among three groups: 2-hour continuous back muscle retraction, 5-minute retraction release after 1 hour of retraction, and 5-minute release at every 40 minutes of retraction. OBJECTIVE: To determine whether intermittent release of the retractor during surgery is effective to prevent severe muscle injury. SUMMARY OF BACKGROUND DATA: In surgery performed on the extremities using a tourniquet, intermittent reperfusion intervals can permit extended tourniquet application when the operation is prolonged. However, there have been no specific studies on the effects of intermittent retraction release for postoperative back muscle injury. METHODS: The back muscle of rats was retracted using a self-retaining retractor for 2 hours. The 36 rats were divided equally into the following three groups: Group 1, 2 hours of continuous retraction; Group 2, two 1-hour retractions interposed with a 5-minute retraction release; and Group 3, three 40-minute retractions interposed with a 5-minute retraction release. In each group, the multifidus muscle was histologically analyzed at 48 hours, 1 week, and 6 weeks after surgery. The muscles were stained by a variety of histochemical methods. The level of serum CPK-MM isoenzyme was measured 48 hours after surgery. RESULTS: Postoperative back muscle degeneration was the most severe in Group 1. The concentration of CPK-MM in Group 1 was significantly higher than that in Groups 2 and 3. One week after surgery, the lesser diameter of regenerated fibers in Group 1 was smaller than that in Groups 2 and 3. The incidence of neurogenic muscle damage was the highest in Group 1. CONCLUSIONS: During posterior lumbar spine surgery, 5-minute retraction release after 1 hour or after 40 minutes of retraction was effective in preventing severe back muscle injury after surgery.

Animals↗
PubMed1994

Electromyography of back muscles during quadrupedal and bipedal walking in primates.

Despite the extensive electromyographic research that has addressed limb muscle function during primate quadrupedalism, the role of the back muscles in this locomotor behavior has remained undocumented. We report here the results of an electromyographic (EMG) analysis of three intrinsic back muscles (multifidus, longissimus, and iliocostalis) in the baboon (Papio anubis), chimpanzee (Pan troglodytes), and orangutan (Pongo pygmaeus) during quadrupedal walking. The recruitment patterns of these three back muscles are compared to those reported for the same muscles during nonprimate quadrupedalism. In addition, the function of the back muscles during quadrupedalism and bipedalism in the two hominoids is compared. Results indicate that the back muscles restrict trunk movements during quadrupedalism by contracting with the touchdown of one or both feet, with more consistent activity associated with touchdown of the contralateral foot. Moreover, despite reported differences in their gait preferences and forelimb muscle EMG patterns, primates and nonprimate mammals recruit their back muscles in an essentially similar fashion during quadrupedal walking. These quadrupedal EMG patterns also resemble those reported for chimpanzees, gibbons and humans (but not orangutans) walking bipedally. The fundamental similarity in back muscle function across species and locomotor behaviors is consistent with other data pointing to conservatism in the evolution of the neural control of tetrapod limb movement, but does not preclude the suggestion (based on forelimb muscle EMG and spinal lesion studies) that some aspects of primate neural circuitry are unique.

Animals↗
PubMed1997

Isokinetic and psychophysical lifting strength, static back muscle endurance, and magnetic resonance imaging of the paraspinal muscles as predictors of low back pain in men.

Magnetic resonance imaging was used to determine the cross-sectional areas and the T2-weighted and proton density-weighted signal intensities of the paraspinal muscles in a group of 128 men, aged 35-63, who had varied histories of occupational and leisure-time physical activities. These measures, and the isokinetic lifting, psychophysical lifting, and static back muscle endurance tests were examined as predictors of low back pain over 12 months of follow-up, in the 43 men who reported no low back pain in the year preceding testing. None of the imaging measures or the muscle function tests was useful as a predictor of future low back pain. Associations with the frequency of low back pain before testing were investigated in the larger group. Smaller total cross-sectional area of the paraspinal muscles and greater signal intensities had weak but significant correlations with more frequent low back pain in the previous year, possibly due to muscle atrophy.

Humans↗