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PubMed1995

Effect of intensive training on the isokinetic strength and structure of lumbar muscles in patients with chronic low back pain.

STUDY DESIGN: This study investigated the effects of the intensive physical rehabilitation program on the trunk and knee extensor muscles in patients with chronic low back pain. At baseline and after 3 months, strength was measured and muscle biopsies were taken. OBJECTIVES: To evaluate the effects of strength exercises on the structure of back muscles. SUMMARY OF BACKGROUND DATA: Rehabilitation designed for chronic low back pain patients improves trunk muscle strength, mobility of the spine, and the patients' functional capacity. The effects of such programs on the structure of back muscles have not been reported previously. METHODS: Thirty patients with chronic low back pain volunteered to participate in the study. Biopsies were taken from the multifidus and vastus lateralis muscles. The sizes of Types 1 and 2 muscle fibers were measured. The peak-torques of isokinetic trunk and knee extension were determined at two different angular velocities. RESULTS: Strength increased by 19-22% (P < 0.05) in trunk extension and by 7-11% (P < 0.05) in knee extension. Type 1 fibers maintained their pre-exercise size. The size of Type 2 muscle fibers in men increased by 11% (P < 0.05) in the multifidus and by 8% (P < 0.05) in the vastus lateralis. In women, the corresponding increases were 11% (P = 0.16) and 11% (P < 0.05). The correlation between the size of Type 2 muscle fibers in the multifidus and the strength of trunk extension improved, especially in men at follow-up. CONCLUSIONS: The results of the present study suggest that training with maximal or submaximal effort may reverse the selective atrophy of Type 2 fibers in the multifidus muscles in men. Intensive training also can significantly increase the trunk extension strength in women, but women may need a longer training period than men to achieve significant structural changes in their back muscles.

Adult↗
PubMed1999

Biomechanics of increased exposure to lumbar injury caused by cyclic loading. Part 2. Recovery of reflexive muscular stability with rest.

STUDY DESIGN: Electromyographic responses from the lumbar multifidus muscle of the cat were recorded in vivo during 50 minutes of cyclic loading followed by 2 hours of rest. OBJECTIVE: To determine the rate of recovery of reflexive muscular stabilizing activity resulting from rest after viscoelastic laxity induced by 50 minutes of cyclic loading. SUMMARY OF BACKGROUND DATA: Muscular forces from agonists and antagonists were repeatedly shown to be the most significant stabilizing structures of the lumbar spine. Reflexive muscular coactivation force from the multifidus muscle elicited by mechanoreceptors in the spinal viscoelastic structures were, however, shown to diminish drastically with the onset of laxity in the viscoelastic structures. Data describing the rate of recovery of reflexive muscular coactivation forces resulting from rest after cyclic loading were not found. METHODS: Cyclic loading of the lumbar spine at 0.25 Hz was applied to L4-L5 for 50 minutes while electromyograms from the multifidus muscles of L1-L2 to L6-L7 were recorded. A rest period of up to 2 hours was given, during which electromyographic responses and load were measured every 10 minutes to sample recovery of laxity and reflexive muscular activity. RESULTS: Load and electromyographic response demonstrated an exponential decrease during the 50 minutes of cyclic loading. The first 10 minutes of rest allowed a significant recovery in laxity and muscle activity, with additional slow recovery over the next 20 to 30 minutes. The electromyographic response and load were increasing at an extremely slow rate thereafter. Overall, 2 hours of rest yielded only a 20% to 30% recovery in electromyographic response. Full recovery was never observed. A biexponential model was developed to predict loss and recovery of reflexive muscular activity and viscoelastic tension with laxity. CONCLUSIONS: Laxity in the viscoelastic structures of the lumbar spine desensitizes the mechanoreceptors within and causes loss of reflexive stabilizing forces from the multifidus muscles. The first 10 minutes of rest after cyclic loading results in fast partial recovery of muscular activity. However, full recovery is not possible even with rest periods twice as long as the loading period, placing the spine at an increased risk of instability, injury, and pain.

Animals↗
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↗
PubMed2006

Fat content of lumbar paraspinal muscles in patients with chronic low back pain and in asymptomatic volunteers: quantification with MR spectroscopy.

PURPOSE: To prospectively evaluate the fat content of paraspinal muscles by using proton magnetic resonance (MR) spectroscopy in patients with chronic low back pain (LBP) and in asymptomatic volunteers matched with regard to age, sex, and body mass index. MATERIALS AND METHODS: The study was approved by the responsible institutional review board. Informed consent was obtained from each patient and each volunteer. Single-voxel proton MR spectroscopy was used to measure the fat content of the lumbar multifidus and longissimus muscles in 25 patients (13 women, 12 men; mean age, 40.5 years) with chronic LBP and in 25 matched asymptomatic volunteers (13 women, 12 men; mean age, 39.8 years). The fat content was also graded semiquantitatively (grades 0-4). The relationship between fat content and LBP duration, LBP intensity, and self-rated disability was assessed (Pearson correlation). RESULTS: The mean percentage fat content of the multifidus muscle was 23.6% (95% confidence interval [CI]: 17.5%, 29.7%) in patients with chronic LBP and 14.5% (95% CI: 10.8%, 18.3%) in the volunteers (P = .014). The corresponding values for the longissimus muscle were 29.3% (95% CI: 23.4%, 35.3%) in patients with LBP and 26.0% (95% CI: 21.9%, 30.0%) in the volunteers (P = .66). The semiquantitative grading of the fat content of the multifidus muscle was 0 in 12 (48%) of 25 patients and in 14 (56%) of 25 volunteers, 1 in 11 (44%) patients and in eight (32%) volunteers, and 2 in two (8%) patients and three (12%) volunteers. The semiquantitative grading of the fat content of the longissimus muscle was 0 in nine (36%) of 25 patients and 15 (60%) of 25 volunteers, 1 in 13 (52%) patients and nine (36%) volunteers, and 2 in three (12%) patients and one (4%) volunteer. Neither grade 3 nor grade 4 was assigned to any muscle. The grading differences were not significant between patients and volunteers. No significant correlation was found between fat content and pain intensity, pain duration, or self-rated disability. CONCLUSION: Proton MR spectroscopy demonstrates a significantly higher fat content in the multifidus muscle in patients with chronic LBP than in asymptomatic volunteers. No difference was detected with a semiquantitative grading system.

Adipose Tissue↗
PubMed1976

Muscle imbalance in the aetiology of scoliosis.

At the apex of an idiopathic scoliotic curve there is a greater proportion of "slow twitch" muscle fibres in multifidus on the convex as compared to the concave side. To determine whether this represents a primary muscular imbalance relevant to the aetiology of idiopathic scoliosis or merely a secondary change, the lengths of multifidus on opposite sides of the curve were measured. Multifidus is shorter on the convex side. This is consistent with the theory of primary muscular imbalance, in which the more tonically acting muscle with its higher proportion of "slow twitch" fibres contracts and shortens as the deformity is produced. The paradox of multifidus being shorter on the convex rather than on the concave side is explained by consideration of its action.

Adolescent↗
PubMedDate not supplied

Molecular evidence for local denervation of paraspinal muscles in failed-back surgery/postdiscotomy syndrome.

A study was performed to analyze whether local denervation of the medial branch of the dorsal ramus of the lumbar spinal nerve occurs in a patient with postoperative failed-back surgery syndrome/postdiscotomy syndrome (FBSS/PDS). We investigated the effect of the loss of innervation of the multifidus muscle on neuronal nitrite oxide synthetase (n-NOS) and endothelial nitrite oxide synthetase (e-NOS) applying realtime RT-PCR and immunohistochemistry. Our study demonstrates a substantial reduction of n-NOS expression, supporting the view that local denervation of the multifidus is involved in the pathology of FBSS. No regulation of e-NOS was detectable. Interestingly, this change is region-specific and does not occur throughout the entire multifidus segment. This result supports the hypothesis that local denervation of the multifidus muscle is involved in the pathology of FBSS/ PDS.

Aged↗
PubMed2026

Multi-Omics Landscape of Paraspinal Muscles in Spinal Muscular Atrophy With Scoliosis.

Most spinal muscular atrophy (SMA) patients develop severe scoliosis by late adolescence. Given that the paraspinal muscles-particularly the multifidus-are indispensable for maintaining spinal stability, their site-specific multi-omics characteristics in SMA remain insufficiently defined. Herein, integrated multi-omics sequencing was performed on bilateral multifidus samples from SMA patients and surgical controls. We identified 5219 differentially expressed genes, 1063 differentially expressed proteins and 370 differential metabolites between the control and SMA, showing significant enrichment in glucose and amino acid metabolism pathways, specifically key steps of glycolysis/gluconeogenesis. Key enzymes in the glycolytic process such as PFKM, ENO3 and PKM1 were markedly downregulated. Notably, a comparative analysis of the bilateral paraspinal muscles in SMA revealed asymmetrical metabolic signatures in carbohydrate and amino acid processing between the concave and convex sides. Key regulatory enzymes exhibited significant differential expression: PYGL, a central driver of starch and sucrose metabolism; creatine kinase, involved in arginine and proline metabolism; and PGAM2, a key mediator of glycine, serine, and threonine metabolism. These metabolic signatures indicate a complex metabolic reprogramming in the multifidus, where asymmetric disparities point to the influence of mechanical loading, while systemic dysregulation aligns with the effects of SMN depletion.

Humans↗
PubMed1988

Back muscle function during bipedal walking in chimpanzee and gibbon: implications for the evolution of human locomotion.

The evolution of erect posture and locomotion continues to be a major focus of interest among paleoanthropologists and functional morphologists. To date, virtually all of our knowledge about the functional role of the back muscles in the evolution of bipedalism is based on human experimental data. In order to broaden our evolutionary perspective on the vertebral region, we have undertaken an electromyographic (EMG) analysis of three deep back muscles (multifidus, longissimus thoracis, iliocostalis lumborum) in the chimpanzee (Pan troglodytes) and gibbon (Hylobates lar) during bipedal walking. The recruitment patterns of these three muscles seen in the chimpanzee closely parallel those observed in the gibbon. The activity patterns of multifidus and longissimus are more similar to each other than either is to iliocostalis. Iliocostalis recruitment is clearly related to contact by the contralateral limb during bipedal walking in both species. It is suggested that in both the chimpanzee and gibbon, multifidus controls trunk movement primarily in the sagittal plane, iliocostalis responds to and adjusts movement in the frontal plane, while longissimus contributes to both of these functions. In many respects, the activity patterns shared by the chimpanzee and gibbon are quite consistent with recent human experimental data. This suggests a basic similarity in the mechanical constraints placed on the back during bipedalism among these three hominoids. Thus, the acquisition of habitual bipedalism in humans probably involved not so much a major change in back muscle action or function, but rather an improvement in the mechanical advantages and architecture of these muscles.

Animals↗
PubMed1994

Running training alters fiber type composition in spinal muscles.

The issue of whether exercise can induce changes in muscle fiber types has been long debated. Knowledge about the alterations in spinal muscle fiber types is scarce. In this study, the alterations initiated by long-distance running on spinal muscle fiber type distribution was studied. Ten young dogs were run on a treadmill for 55 weeks, 5 days a week, and ten dogs from the same litters served as controls. The daily running distance was gradually increased to 40 km and maintained at that level for the final 15 weeks. Histological sections were prepared from the cervical, thoracic, and lumbar multifidus muscles and the medial and lateral heads of triceps brachii and analyzed for the fiber type composition and cross-sectional area of fibers. In the lumbar multifidus, the numerical percentage of the muscle fibers with low oxidative capacity (type II) increased significantly in the running group. However, in the thoracic and cervical spine multifidus, the response to running resembled more of the significant shift from type II to type I fibers (with high oxidative capacity), which was also observed in the triceps brachii muscle. In these muscles, the quantitative image analysis of nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR) reaction also demonstrated a shift towards a higher oxidative capacity within the type II fibers. The results show that training can induce changes in fiber type composition not only in limb muscles but also in the stabilizing spinal muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Back extensor and psoas muscle cross-sectional area, prior physical training, and trunk muscle strength--a longitudinal study in adolescent girls.

The association between physical training, low back extensor (erector spinae plus multifidus muscles) and psoas muscle cross-sectional areas (CSA) and strength characteristics of trunk extension and flexion were studied in adolescent girls. A group of athletes (n = 49) (age range 13.7-16.3 years) consisting of gymnasts, figure skaters and ballet dancers was age-matched with non-athletes (n = 17) who acted as a sedentary control group. The CSA of psoas muscles and multifidus plus erector spinae muscles were measured from lumbar axial images by magnetic resonance imaging. Maximal trunk extension and flexion forces were measured in a standing position using a dynamometer and trunk musculature endurance was evaluated using static holding tests. When CSA were adjusted with body mass, the athletes showed significantly greater CSA in both muscles studied (psoas P < 0.001; erector spinae plus multifidus P < 0.05) than the non-athletes. The athletes also had a greater absolute psoas muscle CSA (P < 0.01) and trunk flexion force (P < 0.01) compared to the controls. When the forces were expressed relative to body mass, the athletes were superior both in trunk flexion (P < 0.001) and extension (P < 0.001). There was a significant correlation between muscle CSA and strength parameters, but the force per muscle CSA did not differ significantly between the athletes and the non-athletes. In addition, the athletes showed a better body mass adjusted muscle endurance in trunk flexion (P < 0.05) than the non-athletes. Our study indicated that regular physical training enhances trunk musculature hypertrophy, force and endurance in adolescent girls, and that there is an association between muscle CSA and strength parameters.

Adolescent↗
PubMed2004

Correlation between inter-vertebral disc morphology and the results in patients undergoing Graf ligament stabilisation.

BACKGROUND: Previous studies have shown Graf ligament stabilisation procedure to give mixed results in the short to medium term. The aim of this study was to correlate the pre-operative state of the disc, multifidus muscles, age of the patient, levels operated and the clinical outcome after a mean follow-up of 47 months. METHODS: Graf ligament stabilisation procedure was carried out in 38 patients between 1996 and 1999. Their post-operative status was assessed using MacNab criteria. The post-operative follow-up was by postal questionnaires and review of the clinical notes. Disc morphology and multifidus muscle wasting was graded blindly and independently. The intra- and interobserver reliability was measured with kappa score and classified using the kappa classification of Landis and Koch. Correlation was measured with the help of Spearman correlation coefficient. RESULTS: Thirty-eight patients (100%) returned the questionnaires. Mean follow-up time was 47.55 months. Fifty-nine levels were operated on. Mean age was 39.68 years. The overall re-operation rate was 15.8%. The intra- and interobserver reliability was graded as good to substantial. Twenty-two patients (57.89%) were satisfied with the procedure. There was no statistically significant correlation between disc morphology, multifidus muscle wasting, sex, age, number of levels operated, the levels operated, and the satisfaction rate. CONCLUSIONS: The indications of Graf ligament stabilisation procedure are not clear. Further work is necessary to clearly identify the indication for the procedure.

Adolescent↗
PubMed2004

Anatomical study of the paraspinal approach to the lumbar spine.

The original description of the paraspinal posterior approach to the lumbar spine was for spinal fusion, especially regarding lumbosacral spondylolisthesis treatment. In spite of the technical details described by Wiltse, exact location of the area where the sacrospinalis muscle has to be split remains somewhat unclear. The goal of this study was to provide topographic landmarks to facilitate this surgical approach. Thirty cadavers were dissected in order to precisely describe the anatomy of the trans-muscular paraspinal approach. The level of the natural cleavage plane between the multifidus and the longissimus part of the sacrospinalis muscle was noted and measurements were done between this level and the midline at the level of the spinous process of L4. A natural cleavage plane between the multifidus and the longissimus part of the sacrospinalis muscle was present in all cases. There was a fibrous separation between the two muscular parts in 55 out of 60 cases. The mean distance between the level of the cleavage plane and the midline was 4 cm (2.4-5.5 cm). In all cases, small arteries and veins were present, precisely at the level of the cleavage plane. We found it possible to easily localize the anatomical cleavage plane between the multifidus part and the longissimus part of the sacrospinalis muscle. First the superficial muscular fascia is opened near the midline, exposing the posterior aspect of the sacrospinalis muscle. Then, the location of the muscular cleft can be found by identifying the perforating vessels leaving the anatomical inter-muscular space.

Female↗
PubMed2007

Paraspinal muscle control in people with osteoporotic vertebral fracture.

The high risk of sustaining subsequent vertebral fractures after an initial fracture cannot be explained solely by low bone mass. Extra-osseous factors, such as neuromuscular characteristics may help to explain this clinical dilemma. Elderly women with (n = 11) and without (n = 14) osteoporotic vertebral fractures performed rapid shoulder flexion to perturb the trunk while standing on a flat and short base. Neuromuscular postural responses of the paraspinal muscles at T6 and T12, and deep lumbar multifidus at L4 were recorded using intramuscular electromyography (EMG). Both groups demonstrated bursts of EMG that were initiated either before or shortly after the onset of shoulder flexion (P < 0.05). Paraspinal and multifidus onset occurred earlier in the non-fracture group (50-0 ms before deltoid onset) compared to the fracture group (25 ms before and 25 ms after deltoid onset) in the flat base condition. In the short base condition, EMG amplitude increased significantly above baseline earlier in the non-fracture group (75-25 ms before deltoid onset) compared to the fracture group (25-0 ms before deltoid onset) at T6 and T12; yet multifidus EMG increased above baseline earlier in the fracture group (50-25 ms before deltoid) compared to the non-fracture group (25-0 ms before deltoid). Time to reach maximum amplitude was shorter in the fracture group. Hypothetically, the longer time to initiate a postural response and shorter time to reach maximum amplitude in the fracture group may indicate a neuromuscular contribution towards subsequent fracture aetiology. This response could also be an adaptive characteristic of the central nervous system to minimise vertebral loading time.

Aged↗
PubMed2005

Device-assisted muscle strengthening in the rehabilitation of patients after surgically stabilized vertebral fractures.

OBJECTIVES: To investigate the effects of a device-assisted muscle strengthening exercise program on the surgically traumatized multifidus musculature and on the intact longissimus and iliocostal muscles and to assess the possible relationship between patients' reported pain symptoms and changes in muscle strength or changes in cross-sectional area (CSA) of the musculature. DESIGN: Open, prospective noncontrolled prepost intervention study. SETTING: University-affiliated center for ambulant physiotherapy. PARTICIPANTS: Fifteen patients who had undergone dorsal osteosynthesis for treatment of thoracolumbar vertebral fracture and who complained of persistent back pain. INTERVENTION: Twelve-week device-assisted training exercise program. MAIN OUTCOME MEASURES: Patients' pain score, muscle strength, and the CSA of the paravertebral musculature determined by magnetic resonance imaging (MRI) were assessed before and after the exercise program. RESULTS: MRI findings revealed no increase in the CSA of the multifidus muscle in any patient (median change, -.27 cm 2 ). All patients, however, exhibited hypertrophy of both the longissimus and iliocostal muscles (median change, 1.39 cm 2 ). Significant increase in muscle strength was observed in 14 of 16 patients (median increase, 56%; range, 0.7%-126.4%). The median overall pain score improved from 19 (range, 7-24) to 16 (range, 5-27). The change in muscle strength and muscle CSA, however, showed no correlation. There was also no correlation between increase in muscle strength and changes in pain scores. CONCLUSIONS: The device-assisted training program resulted in hypertrophy of the iliocostal and longissimus muscles and an increase in muscle strength in patients with surgically stabilized vertebral fractures. About half of the patients reported relief of pain. No correlation was found between hypertrophy, increase in muscle strength, and relief of pain. The surgically damaged multifidus musculature, however, did not show any change in CSA and was not accessible to rehabilitative measures.

Adult↗
PubMed2001

Neuromuscular neutral zones sensitivity to lumbar displacement rate.

OBJECTIVES: To determine the displacement and tension thresholds (developed during anterior lumbar flexion) which trigger reflexive muscular activity in the multifidus muscles; their variability with the velocity of flexion; and the pattern of threshold variability across the lumbar spine.Design. An in-vivo study of the feline during passive lumbar flexion applied via the L-4/5 supraspinous ligament. METHOD: EMG from six pairs of intramuscular electrodes inserted in the L-1/2 to L-6/7 multifidus muscles was recorded while the lumbar spine was passively flexed to 75% of the physiological strain of the supraspinous ligament at rates of 17-100%/s. Three-dimensional models of tension threshold, flexion rate and lumbar levels were developed from the experimental data. RESULTS: Displacement and tension thresholds were the lowest at the fastest flexion rate and gradually increased as flexion rates decreased. Electromyographic activity was detected at low thresholds at the center of the flexion and at gradually increasing thresholds at higher and lower lumbar segments. CONCLUSION: Multifidus reflexive muscular activity, which stabilize the spine, is triggered at a displacement and tension thresholds of 5-15% of the physiological range. Earlier activation of muscular activity occurs as the velocity of flexion increases. Earlier activation also occurs near the center of flexion. RELEVANCE: Sensory-motor neurological feedback maintains spine stability and is responsive to the velocity of lumbar motion. A neuromuscular silence exists in small lumbar movements in which spine stability is not protected by the musculature. Spine models constructed to predict risk factors could benefit from incorporating this new information.

Animals↗
PubMed2002

EMG activity of trunk muscles and torque output during isometric axial rotation exertion: a comparison between back pain patients and matched controls.

Abnormal patterns of trunk muscle activity could affect the biomechanics of spinal movements and result in back pain. The present study aimed to examine electromyographic (EMG) activity of abdominal and back muscles as well as triaxial torque output during isometric axial rotation at different exertion levels in back pain patients and matched controls. Twelve back pain patients and 12 matched controls performed isometric right and left axial rotation at 100%, 70%, 50% and 30% maximum voluntary contractions in a standing position. Surface EMG activity of rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum and multifidus were recorded bilaterally. The primary torque in the transverse plane and the coupling torques in sagittal and coronal planes were measured. Results showed that there was a trend (P = 0.08) of higher flexion coupling torque during left axial rotation exertion in back pain patients. Higher activity for external oblique and lower activity for multifidus was shown during left axial rotation exertion in back pain group when compared to the control group. In right axial rotation, back pain patients exhibited lesser activity of rectus abdominis at higher levels of exertion when compared with matched controls. These findings demonstrated that decreased activation of one muscle may be compensated by overactivity in other muscles. The reduced levels of activity of the multifidus muscle during axial rotation exertion in back pain patients may indicate that spinal stability could be compromised. Future studies should consider these alternations in recruitment patterns in terms of spinal stability and internal loading. The findings also indicate the importance of training for coordination besides the strengthening of trunk muscles during rehabilitation process.

Abdominal Muscles↗
PubMed2003

Muscular dysfunction elicited by creep of lumbar viscoelastic tissue.

The biomechanics, histology and electromyography of the lumbar viscoelastic tissues and multifidus muscles of the in vivo feline were investigated during 20 min of static as well as cyclic flexion under load control and during 7 h of rest following the flexion. It was shown that the creep developed in the viscoelastic tissues during the 20 min of static or cyclic flexion did not fully recover over the 7 h of following rest. It was further seen that a neuromuscular disorder with five distinct components developed during and after the static and cyclic flexion. The neuromuscular disorder consisted of a decreasing magnitude of reflexive EMG from the multifidus upon flexion as well as of superimposed spasms. The recovery period was characterized by an initial muscle hyperexcitability, a slowly increasing reflexive EMG and a delayed hyperexcitability. Histological data from the supraspinous ligament demonstrate significant increase (x 10) in neutrophil density in the ligament 2 h into the recovery and even larger increase (x 100) 6 h into the recovery from the 20 min flexion, indicating an acute soft tissue inflammation. It was concluded that sustained static or cyclic loading of lumbar viscoelastic tissues may cause micro-damage in the collagen structure, which in turn reflexively elicit spasms in the multifidus as well as hyperexcitability early in the recovery when the majority of the creep recovers. The micro-damage, however, results in the time dependent development of inflammation. In all cases, the spasms, initial and delayed hyperexcitabilities represent increased muscular forces applied across the intervertebral joints in an attempt to limit the range of motion and unload the viscoelastic tissues in order to prevent further damage and to promote healing. It is suggested that a significant insight is gained as to the development and implications of a common idiopathic low back disorder as well as to the development of cumulative trauma disorders.

Animals↗
PubMed1997

Contraction of the abdominal muscles associated with movement of the lower limb.

BACKGROUND AND PURPOSE: Activity of the trunk muscles is essential for maintaining stability of the lumbar spine because of the unstable structure of that portion of the spine. A model involving evaluation of the response of the lumbar multifidus and abdominal muscles to leg movement was developed to evaluate this function. SUBJECTS: To examine this function in healthy persons, 9 male and 6 female subjects (mean age = 20.6 years, SD = 2.3) with no history of low back pain were studied. METHODS: Fine-wire and surface electromyography electrodes were used to record the activity of selected trunk muscles and the prime movers for hip flexion, abduction, and extension during hip movements in each of those directions. RESULTS: Trunk muscle activity occurring prior to activity of the prime mover of the limb was associated with hip movement in each direction. The transversus abdominis (TrA) muscle was invariably the first muscle that was active. Although reaction time for the TrA and oblique abdominal muscles was consistent across movement directions, reaction time for the rectus abdominis and multifidus muscles varied with the direction of limb movement. CONCLUSION AND DISCUSSION: Results suggest that the central nervous system deals with stabilization of the spine by contraction of the abdominal and multifidus muscles in anticipation of reactive forces produced by limb movement. The TrA and oblique abdominal muscles appear to contribute to a function not related to the direction of these forces.

Abdominal Muscles↗