Lumbar Trunk Research Articles

Use of lumbar trunk muscles in isometric performance of mechanically complex standing tasks.

Ten subjects performed 25 tasks isometrically while standing. Those tasks imposed substantial extension, lateral bending, and twisting moments on the lumbar spine. Mechanically complex trunk muscle actions were called for to resist those moments. Biomechanical model analyses were used to predict the trunk muscle contraction forces needed to perform those tasks, and surface myoelectric activities were measured to validate those predictions. Predictions and measurements were linearly well correlated.

Analysis and quantitative myoelectric measurements of loads on the lumbar spine when holding weights in standing postures.

Ten subjects executed a number of weight-holding and force-resisting work tasks while standing either upright or with their trunks in 30 degrees of forward flexion. All tasks involved sagitally symmetric body configurations and were performed isometrically. A simple calculation scheme was devised to predict the lumbar trunk muscle contraction forces and the lumbar spine compression forces required for execution of each task. The myoelectric activity was recorded quantitatively at eight sites over the lumbar trunk muscles and at four sites over the abdominal muscles. Good correlation was found between the predicted muscle contraction forces and the myoelectric activities.

Loads on the lumbar spine. Validation of a biomechanical analysis by measurements of intradiscal pressures and myoelectric signals.

We studied the validity of predictions of compressive loads on the lumbar spine and contraction forces in lumbar trunk muscles based on a biomechanical model. The predictions were validated by quantitative measurements of myoelectric activities at twelve locations on the trunk and of the pressure in the third lumbar disc. Twenty-five tasks were performed isometrically by four healthy volunteers. The model predicted that the tasks imposed mean compressive loads on the spine of as much as 2400 newtons and required contraction forces of the posterior muscles of the back of as much as 1800 newtons. Intradiscal pressures of as much as 1600 kilopascals were measured. The predicted and measured quantities were well correlated. It appears that the model adequately predicted the compressive loads on the lumbar spine and the tensions in the back muscles. Patients with low-back disorders limit their physical activities, which indicates that loading on the spine must be a factor in those disorders. This study shows that the loads imposed on the spine by physical activities need not be measured. They can easily be calculated. This will significantly accelerate biomechanics research on low-back disorders. The calculation techniques that we validated for predicting loads on the spine can be used to calculate the loads on any skeletal structure. Those loads are largely determined not by the externally applied loads, but by the moments of those applied loads and by the moments of the weights of the body segments that the structure must support.

Analysis and measurement of lumbar trunk loads in tasks involving bends and twists

Ten subjects performed isometric weight-holding and force-resisting work tasks while standing upright, both with and without a twist of the trunk; with the trunk bent laterally; and in postures involving combinations of bending and twisting. The lumbar trunk muscle contraction forces and the lumbar spine compression and shear forces imposed by these tasks were predicted using a biomechanical model. Myoelectric activity was recorded quantitatively at eight locations over the back muscles and at four locations over the abdominal wall muscles. Correlation coefficients from 0.67 to 0.88 were found between the predicted muscle contraction forces and the measured myoelectric activities when the predictions were made so as to minimize muscle contraction force per unit area. Trunk twisting and lateral bending were found to load the spine and trunk muscles less than trunk flexion or holding of weights in front of the body.

Contraction recruitment patterns in lumbar trunk muscles

Contraction recruitment patterns in lumbar trunk muscles

Analysis and measurement of the loads on the lumbar spine during work at a table

A study has been made in which the loads on the lumbar spine and trunk muscles were calculated in static submaximal armlifts, and the method validated in part by measurements of myoelectric back muscle activity. Ten subjects performed thirty work tasks while seated at a table. The lumbar spine loads and lumbar trunk muscle contraction forces required for task execution were predicted using mechanical analysis. The myoelectric activity was recorded at eight sites in the low back region. A good correlation was obtained between the contraction force predictions and the myoelectric signal levels.

Localization of lumbar epaxial motoneurons in the rat

In the rat, lateral longissimus and the lumbar transverso-spinalis muscles are lumbar trunk muscles, and participate in the lordosis reflex (female sexual posturing). Medial longissimus, the remaining major lumbar epaxial muscle, is a muscle of the proximal tail-tailbase. To allow an analysis of the motor control of lordosis, motoneurons for these muscles must be localized. Horseradish peroxidase (HRP) was injected into lumbar epaxial muscles of female rats. Following injection into medial longissimus, labeled cells were found posterior to the lumbar enlargement, ventrolaterally in the ventral horn. Following injections into lateral longissimus or into lumbar transverso-spinalis muscles, most labeled cells were found on the medial side of the ventral horn, extending through and anterior to the lumbar enlargement. Injections into lumbar transverso-spinalis muscles at more posterior levels led to more posterior locations of labeled cells. The distributions of the labeled cells agree with previous observations on innervation of the muscles. Additionally, the spinal cord was scanned for sites at which microstimulation produced visible twitches of medial longissimus or transverso-spinalis muscles. Locations of low threshold twitch sites were consistent with conclusions based on the HRP findings.

Intrinsic contractility of lymphatics in sheep and in dogs.

Intralymphatic pressures were monitored from plastic cannulas implanted in the thoracic, lumbar trunk and mesenteric lymphatics of conscious and anesthetized sheep, and in the thoracic duct of anaesthetized dogs. Extrinsic factors appeared to be important in the propulsion of lymph only in the thoracic duct of the dog. Intrinsic pulsatile pressure patterns were recorded from all lymphatics studied in sheep, and from the thoracic duct in one out of three dogs. The pulses ranged from about 1–15 mm Hg in amplitude and from about 2–20 pulses/min in frequency. A parameter of contractility was defined and used to establish the existence in sheep of a linear relationship between contractility and flow rate. This relationship was demonstrated when flow was increased by infusion into the lymphatic or into a vein, or, in the case of mesenteric lymphatics, by feeding fat. It was concluded that the intrinsic contractility is myogenic in origin and is the major factor responsible for lymph propulsion at least in sheep; the relationship between contractility and flow enables the rate of lymph flow to keep pace with the rate of lymph production.

Integrated effects of sympathetic lumbar trunk stimulation on myotatic reflex activity of the ankle muscles of the cat

Integrated effects of sympathetic lumbar trunk stimulation on myotatic reflex activity of the ankle muscles of the cat

Techniques for the long-term collection of lymph from the unanaesthetized foetal lamb in utero.

SummarySurgical techniques are described for establishing chronic fistulae in the thoracic, intestinal, lumbar and popliteal lymph ducts of foetal lambs in utero. These fistulae have remained patent and enabled lymph to be collected for periods of up to 5 days. The Iambs have been born spontaneously or delivered by Caesarean section with their fistulae intact and still flowing.Lymph flow rates were 9–18 ml./hour from the thoracic duct, 2.8–8.6 ml. /hour from the intestinal duct, 2.8–9.2 ml./hour from the lumbar trunk and 0.6 ml./hour from the popliteal duct.The protein concentration of foetal thoracic duct lymph was 2.30 g./100 ml. immediately after cannulation, the intestinal lymph 2.37 g./100 ml. and the lumbar lymph 2.12 g./100 ml.The cells of foetal lymph were almost all small and medium lymphocytes and only an occasional cell was found in mitosis. Drainage of the thoracic duct lymph for 36 hours drastically reduced the number of lymphocytes in the lymph, suggesting that, as in the adult sheep, most of the lymphocytes in foetal lymph are recirculating cells.

Sympathetic Vasoconstrictive Responses during Exercise- or Drug-Induced Vasodilatation

The effect of exercise on the vasoconstrictive response to sympathetic stimulation was studied by observing the changes in perfusion pressure in dogs' hindlimbs perfused at constant flow. During steady-state simulated exercise, a time-dependent increase occurred between 10 and 30 minutes in the magnitude of response to lumbar trunk stimulation or carotid sinus hypotension. This was present (although to a reduced Degrees) in drug-induced vasodilatation and in exercising limbs perfused at constant pressure. The time-dependent change was not due to (1) repetition of stimulus, (2) artifact from muscle electrodes, (3) circulating vasoactive substances, (4) skin circulation, or (5) pH, P CO 2 , or temperature of the perfusing blood. When norepinephrine was used as the vasoconstrictive stimulus, no time-dependent change was noted. After stabilization, the frequency-response curve of exercising muscle exceeded that at rest at all blood concentrations of norepinephrine and at all save the lowest frequencies of stimulation. It was concluded that vascular smooth muscle can develop greater tension from greater initial length. However, during exercise some factor which operates between the sympathetic nerve ending and the receptor site on vascular smooth muscle initially tends to depress this enhanced ability to develop tension.

Functional analysis of the vasomotor innervation of the dog's hind footpad.

Vascular responses in the large central pad of the dog's foot were recorded during stimulation of the lumbosacral sympathetic trunk and correlated with the site of stimulation and the subsequent histologic analysis of the excised trunk. The resulting description of the preganglionic inflow and postganglionic outflow from the trunk demonstrated marked variations in the anatomic patterns of the vasomotor innervation of the footpad in various animals. Complete preganglionic denervation of this vascular bed required extirpation of the entire lumbar trunk caudalward as far as L-7 in addition to the interruption of those preganglionic pathways through the spinal nerves which do not pass through the sympathetic trunk.