Lumbar Extensor Research Articles

Effect of extensor muscle activation on the response to lumbar posteroanterior forces

The purpose of this study was to examine the responses of normal subjects to the application of cyclical lumbar posteroanterior forces which simulated a manipulative therapy technique known as mobilization. The specific aim was to determine whether increases in spinal extensor muscle activity could modify the stiffness of lumbar posteroanterior movements. The lumbar posteroanterior stiffness was measured in eleven asymptomatic subjects in the prone position, both in the relaxed condition and during maximal voluntary isometric muscle contractions. The electromyographic activity of lumbar extensor muscles was measured in the relaxed and maximal contraction conditions during the application of mobilization. The posteroanterior stiffness was found to be significantly greater during maximum activation of the extensor muscles. The results indicate that muscle activity can significantly alter lumbar posteroanterior stiffness. Clinicians often apply posteroanterior forces over a spinous process of a vertebra to assess the resistance to movement. Information about the degree and nature of perceived resistance to posteroanterior movement is used to help make a diagnosis and select treatment techniques. This study has shown that increased activity of the spinal extensor muscles can increase the stiffness of lumbar posteroanterior movements, compared with the case where the subject is relaxed. When interpreting the posteroanterior responses of patients, clinicians should be aware that spinal extensor mucle activity can influence resistance to posteroanterior movement.

Lumbar Strengthening in Chronic Low Back Pain Patients|Physiologic and Psychological Benefits

The effects of exercise for isolated lumbar extensor muscles were examined in 54 chronic low-back pain patients. Subjects were randomly assigned to a 10-week exercise program (N = 31) or a wait-list control group (N = 23). Results indicated a significant increase in isometric lumbar extension strength for the treatment group and a significant reduction in reported pain compared with the control group (P 0.05). Treated subjects reported less physical and psychosocial dysfunction whereas the control group increased in pain, and physical and psychosocial dysfunction. There were no concomitant changes in reported daily activity levels. These results show that lumbar extension exercise is beneficial for strengthening the lumbar extensors and results in decreased pain and improved perceptions of physical and psychosocial functioning in chronic back pain patients. However, these improvements were not related to changes in activities or psychological distress.

A Preliminary Investigation of the Relationship Between Lumbar Postero-anterior Mobility and Low Back Pain

AbstractIt is widely assumed that there is a relationship between pain, stiffness and muscle activity in patients with low back pain. This preliminary study was designed to begin an investigation of the existence of this relationship. Two subjects with low back pain and six normal subjects participated. The postero-anterior mobility of L3 and L4 was measured together with lumbar extensor muscle EMG. All normal subjects showed negligible muscle activity whereas both low back pain subjects demonstrated elevated EMG levels. In addition, both low back pain subjects were found to have relatively low mobility of L3 and L4 as compared to the normal subjects. Further research to investigate the relationship between these variables is indicated.

Effect of instructions to simulate a back injury on torque reproducibility in an isometric lumbar extension task

The purpose of this study was to investigate the differences in test-retest reliability between maximal and "simulated back injury" efforts in an isometric lumbar extension task and to test the hypothesis that voluntary attempts to "simulate" a back injury would yield less consistent torque production than maximal efforts. Twenty subjects were asked to undergo lumbar extensor testing at seven different positions in a lumbar extension machine. Each subject was tested twice in a maximal effort condition and twice with instructions to "simulate" a back injury. The order of the conditions was counterbalanced across subjects so that half of the subjects performed the maximal effort tests first and half performed the "simulated" effort first. Results indicated high test-retest correlations at all angles in both conditions. There were no differences in test-retest reliability between effort conditions. Therapist ratings of consistency did not differ between conditions and therapists could not discriminate between conditions on the basis of effort consistency. In the "simulated" condition subjects produced reliable, submaximal torque plots consistent with previous data indicating similar reliability at submaximal levels. It was concluded that use of test-retest torque consistency as a measure of sincerity of effort is premature and may be misleading.

Comparison of Two Restraint Systems for Pelvic Stabilization during Isometric Lumbar Extension Strength Testing

This study was supported in part by a grant from MedX Inc., Ocala, FL. Among strength testing methods, varying degrees of stabilization are used. The purpose of this study was to compare isometric lumbar extension strength values obtained from two different restraint systems designed to isolate the lumbar extensors through pelvic stabilization. Both restraint systems stabilized the pelvis by preventing movement of the lower extremities during testing with the subject in a seated position. One restraint system (KNEE) applied pressure just below the knees while the lower leg was positioned at 120 degrees of knee flexion. The other (FOOT) applied pressure to the bottom of the feet while the lower leg was positioned at 60 degrees of knee flexion. Fifteen men (age = 37 +/- 10 yr; height = 177.7 +/- 5.3 cm; weight = 61.4 +/- 10.9 kg) and six women (age = 43 +/- 7 yr; height = 170.9 +/- 7.9 cm; weight = 61.4 +/- 10.9 kg) were tested at seven positions through 72 degrees range of motion with each restraint system. Analysis of variance for repeated measures indicated a significant difference (p </= 0.05) between restraint systems and a significant restraint system by joint angle interaction. Subjects were able to generate 9.4 to 10.9 percent more torque at 72, 60, 48, and 36 degrees of lumbar flexion with the KNEE restraint system compared to the FOOT restraint system. No differences (p > 0.05) between restraints were noted at 24, 12, or 0 degrees flexion. Thus, the restraint system employed can influence lumbar extension strength values and affect the shape of the isometric lumbar extension strength curve. J Orthop Sports Phys Ther 1992;15(1):37-42.

Back Pain and the Exercise Prescription

Rationale for the use of exercise in the treatment and prevention of LBP and injury has been discussed. Current knowledge supports the use of individualized exercise programs that emphasize the restoration and maintenance of adequate lumbar-spinal function. When indicated, aerobic exercises to develop overall fitness and prevent deconditioning should be included in the exercise prescription. Several commonly used exercises for strengthening the lumbar extensor muscles have been reviewed. Lumbar extension exercises that stabilize the pelvis, provide a means for progressively increasing the resistance, and allow the exerciser to move through a full range of lumbar movement appear to offer the greatest benefit to the patient with LBP.

Body composition and the evolution of the Macropodidae (Potorous, Dendrolagus, and Macropus)

The segmental distribution of body weight and the proportions of skin, muscle, and bone are compared for three genera of the Macropodidae (Potorous, Dendrolagus, and Macropus) and one genus of the Petauridae (Pseudocheirus). Potorous and Macropus possess high proportions of muscle mass to total body weight, high concentrations of musculature in the lumbar extensors, thigh, and tail, and disproportionate ratios of forelimb: hindlimb bone and forelimb: hindlimb muscle which correspond to disproportions of intermembral length. These species converge with high-speed terrestrial runners in some traits and remain distinctive in others. Macropus, larger, more muscular, and faster than Potorous, appears to store and return energy to the hopping cycle more efficiently. Dendrolagus has less than three-fourths the musculature of the other macropod genera, low proportions of the back extensor muscles compared to the other macropods, and relatively more equal ratios of forelimb:hindlimb bone and forelimb:hindlimb muscle. This species converges with slow-moving arboreal climbers such as Pseudocheirus. These data on body mass and tissue proportions translate directly into center of gravity, strength-to-weight ratio, and muscular (kinetic) chains, key elements of macropod evolution. The geometric similarity of muscle between smaller potoroids and larger macropodids, and assumption critical to allometric comparison, is not confirmed.

Effect of resistance training on lumbar extension strength

Development of a new testing machine, which stabilizes the pelvis, allowed us to evaluate the lumbar extensor muscles before and after training. Fifteen healthy subjects (29.1 +/- 8 years of age) trained 1 day per week for 10 weeks and 10 healthy subjects (33.7 +/- 16 years of age) acted as controls. Training consisted of 6 to 15 repetitions of full range of motion variable resistance lumbar extension exercise to volitional fatigue and periodic maximal isometric contractions taken at seven angles through a full range of motion. Before and after the 10 week training period, subjects completed a maximum isometric strength test at seven angles through a 72 degrees range of motion (0 degrees, 12 degrees, 24 degrees, 36 degrees, 48 degrees, 60 degrees, and 72 degrees of lumbar flexion). The training group significantly improved in lumbar extension strength at all angles (P less than or equal to 0.01). The result at 0 degrees (full extension) showed an increase from 180.0 +/- 25 Nm to 364.1 +/- 43 Nm (+102%) and at 72 degrees (full flexion) from 427.4 +/- 44.1 to 607.4 +/- 68 (+42%) Nm. Results from the control group showed no change (P greater than or equal to 0.05). The magnitude of gain shown by the training group reflects the low initial trained state of the lumbar extensor muscles. These data indicate that when the lumbar area is isolated through pelvic stabilization, the isolated lumbar extensor muscles show an abnormally large potential for strength increase.

Application of nonlinear filtering to the decomposition of surface EMG signals

Objective. The purpose of this study was to correlate objective measurements of muscle fatigue in the lower back to the subject's own assessment of fatigue.Design. Muscle fatigue in the lower back was assessed in healthy subjects using electromyography (EMG), endurance time and the Borg scale.Background. Muscle fatigue, measured with EMG and endurance time, in the lower back, is significant for patients with pain in the lower back.Methods. Fifty healthy subjects participated. EMG was detected from the lumbar extensor muscles during a modified Sørensen's test, an isometric contraction for the back extensors until exhaustion. During the test, subjects rated their subjective fatigue on a Borg CR-10 scale.Results. Borg scale ratings correlated with endurance time (0.68) and EMG median- and mean power frequency slopes (0.41–0.50). At a Borg rating of 3, median- and mean power frequency and endurance time were reduced by 30%. At a Borg rating of 5, median- and mean power frequency and endurance time were reduced by 50%. At a Borg rating of 7, median- and mean power frequency and endurance time were reduced by 60–70%.Conclusions. Significant correlation between the Borg scale, EMG and endurance time suggests a close relationship between subjective and objective assessment of muscle fatigue.

Lumbar Degenerative Kyphosis

We suggest that lumbar degenerative kyphosis be included as one of the abnormal sagittal curvatures in which a kyphosis or a marked loss of lordosis is seen in the lumbar spine, caused by degenerative changes in middle-aged and elderly. One hundred and five consecutive patients were investigated, most of whom complained of low-back pain, often with a long history. They all walked in a forward bending posture, either all the time or only when exhausted. In roentgenograms, most cases showed a marked loss of the sacral inclination, as well as multiple disc narrowing and/or vertebral wedging in the lumbar region. These subjects showed a definite weakness of the lumbar extensors compared to the flexors, and therefore a reversed ratio of extensors/flexors muscle power compared with normal controls and other types of spinal curvatures. Weakness of the lumbar extensors was clearly shown by isokinetic measurement and a marked atrophy of these muscles with fatty infiltration was demonstrated by CT scanning.

Body Weight: its Relationship to Tissue Composition, Segmental Distribution of Mass, and Motor Function III.* The Didelphidae of French Guyana

Two sets of anatomical data are presented for six marsupial genera from French Guyana: tissue (skin, muscle, bone) and organ (alimentary tract, brain, eyes) proportions, and segmental distribution of mass (head, tail, thighs, etc.). As a percentage of total weight, skin is about equal in all genera, but the percentage of muscle is low in Caluromys and Didelphis (32%) and exceptionally high in Metachirus (45%); the percentage of viscera is low in Marmosa (6%) and high in Caluromys (10%). Philander, Caluromys, and Marmosa are similar in the segmental distribution of weight: large head, moderately sized thighs, and heavy, prehensile tail. Caluromys and Philander differ in the percentage of total muscle, size of the eyes, and weight of the alimentary tract. Only Monodelphis and Metachirus strongly diverge from the group, and Metachirus possesses many characteristics of high-speed terrestrial cursors such as Dolichotis and Lepus: high percentage of muscle in the body; muscular arms and thighs; elongated and lightened feet; and heavy lumbar extensor muscles. Basically, however, the Didelphidae remain small, prehensile-tailed, scampering and climbing omnivores with only moderate hindlimb dominance. They have not differentiated structurally as much as the prosimians in comparable niches in West Africa or Madagascar. Certain forces have acted conservatively upon body size and locomotor tissues.

Relatiomship Between Kyphosis and Lordsis of the Spines in the Aged

More than two hundred fifty cases of the aged of more than 60 year old were studied about relationship between degree of spinal curvature of thoracic kyphosis and lumbar as well as cervical lordosis and tilting of the sacrum.Significant co-efficient of co-relations were demonstrated in balanced type of the spinal posture between degree of tilting of superior surface of the sacrum and lumbar lordosis, thoracic kyphosis and lumbar lordosis, as well as thoracic kyphosis and cervical lordosis.It would be admitted that the curvatures of every part of the spinal column have an influence to each other in balanced type of the posture. In many of severe kyphosis, there have been observed an extension contracture of the cervical and lumbar spine, which showed a limitation of flexion.Electromyography by surface electrode revealed high action potential from lumbar and/or cervical extensors during standing in case of imbalanced, especially in lumbar and dorsolumbar kyphosis, and gives better informations for treatment.

Convertible respiratory and fusimotor reactions to peripheral somatic stimuli in different functional states of the reticular formation in the cat.

1. In cats either decerebrated and/or anesthetized by various doses of pentobarbital, the action of pinna stimulation (PS) and other natural somatic or electrical nerve stimuli upon respiration was investigated. For an indication of the state of excitability of the reticular formation the lumbar extensor fusimotor PS-responses were obseve simultaneously. 2. The results showed a wide congruence between the responses of respiratory rate and extensor fusimotor activity to PS. Both were enhanced in decerebrated or very lightly anesthetized nondecerebrated cats, but were converted to diminution by administration of pentobarbital. 3. In acceleratory respiratory responses to PS both inspiration and expiration where shortened; in deceleratory ones, mainly expiration was prolonged, while inspiration often was shortened. 4. Other natural somatic stimuli (face skin stimulation, pressure to cubital region, compression of forepaws) also produced respiratory and fusimotor excitation in decerebrated or lightly anesthetized cats. However, after administration of pentobarbital the effects were less consistent. 5. Electrical stimulation of skin-, muscle-, or mixed hind limb nerves caused almost in variantly an augmentation of respiratory rate and fusimotor activity, which was only reduced but not converted to diminution by administration of pentobarbital. 6. The alterations of the responses to PS are attributed to an anesthetic-induced shift of predominant activity from excitatory to inhibitory reticular structures. Consequently their influences on the respiratory centers and on reticulospinal neurons descending to the fusimotoneurons are changed.

The Effect of Brain Stem Irradiation on Descending Systems to the Spinal Cord

Brain stem and cerebellar irradiation was found to affect brain stem conditioned lumbar cord flexor and extensor monosynaptic reflexes. The preconditioning extensor and flexor monosynaptic reflexes were either both inhibited or both facilitated. The conditioned reflex was affected conversely; i.e., the flexor tended to be facilitated while the extensor was inhibited. Radiation appeared to affect a balance of brain stem level interaction on the descending systems to the spinal cord. The cerebellum seems to take part in the mediation of this balance since decrebellates did not show an effect of radiation.

EFFECTS OF STRYCHNINE UPON SUPRASPINAL INHIBITION.

1. Effects of strychnine upon the pontine reticular inhibition to lumbar extensor motoneurons were examined by using the monosynaptic reflex test as well as the intracellular potential recording from motoneurons of the cat.2. The inhibition elicited by single pulse stimulation of the pontine reticular formation was eliminated by strychnization in the same dosis with that for blocking the direct inhibition. The elimination of inhibition usually made the facilitatory component, having been hidden by the inhibition, predominant.3. Under heavy strychnization which evoked strychnine tetanus, it was observed on ventral root and intracellular potentials that, when repetitive stimulation of the pontine reticular formation was applied with appropriate strength and frequency, the strychnine tetanus could be completely stopped during the stimulation. The appropriate parameters of stimulation were those for eliciting the sufficient and continuous smooth depolarization in motoneurons.4. The mechanism of stopping the strychnine tetanus was discussed in concern with the accommodation of motoneurons to the elicited sustained depolarization.