Low Back Muscle Activity Research Articles

Sitting with adjustable ischial and back supports: biomechanical changes.

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

Ergonomic Analysis of Pallets and Drum Handling

This study investigates the effects of heavy pallet and drum handling on spinal loading at the L5/S1 region and surface electromyographic activity of the erector spinae muscles, and the associated risk of low back disorder (LBD). Ten field technicians at the Lawrence Livermore National Laboratory (LLNL) were asked to unstack plastic and metallic pallets and manipulate 55 gallon waste drums. Lifting the metallic and plastic pallets and lowering a 34 Kg drum induced the highest disc compression at the L5/S1 level, while manipulating the pallets and breaking up a 203 Kg drum induced the highest low back muscle activity. The major results showed that posture has a significant influence on disc compression force; however, the lowest muscle load may not be correlated with the lowest disc compression. The computed disc compression forces and EMG activities are most likely responsible for the elevated risk of back injury in waste management workers.

Electromyographic comparison of two lumbar support mechanisms intended for automotive seating applications

The purpose of this study was to compare and contrast the effect of two lumbar support mechanisms on low back muscle activity. These mechanisms were designed to provide either microadjustment or massage. In the control condition, the lumbar support mechanism was set to the full-off position (0 mm of mechanism prominence). In this position, the foam contour supplied only a minimal amount of support. This condition, which is representative of traditional lumbar support design, was used to obtain an indication of the typical amount of low back muscle activity expected from automotive sitting. The data were collected using surface electrodes located at the L3 and L5 levels. Both lumbar support mechanisms provided a small reduction in low back muscle activity during a 1 h session. This can be contrasted with the control condition, which resulted in a small increase. In this respect, the mechanisms were considered an improvement on traditional lumbar support designs.

Low Back Muscle Activity in an Automobile Seat with a Lumbar Massage System

This investigation was conducted to determine the effects of a massaging lumbar support system on low back muscle activity. The apparatus included a luxury-level automobile seat, six 10-mm diameter bipolar surface electrodes, an amplifier, an analog-to-digital conversion board, data acquisition software, and a personal computer. Six experimental conditions, each involving a variation of massage time, were considered. The dependent variable was the change in the root mean square variation of the EMG signal. One minute of lumbar massage every 5 min was found to have a beneficial effect on low back muscle activity (as compared to no massage). This may prove to be an extremely important result in the quest to combat low back pain attributable to automobile seating.

Impact of a Chest Support on Lower Back Muscles Activity During Forward Bending

The present study is based on previous research on the poor body posture of surgeons and their experienced discomfort during surgical procedures. Since surgeons have head‐bent and back‐bent posture during open surgical procedures, a chest support is a viable supporting principle. This support is meant to reduce lower back pain by minimising lower back muscle activity. The aim of this study is to investigate the impact of a chest support on lower back muscle activity during forward bending and to establish a possible relation between supporting force and the kind of balancing strategy a person adopts. Use of the chest support shows a significant reduction of muscle activity in the lower back and leg muscles. Within the participants three user groups are identified as “sceptical users”, “non‐trusters” and “fully trusters”, each following a different balancing strategy. Since there are different kinds of users, the designed body support should offer the possibility for altering the posture and should not constrain the user to take a certain body posture.

Effect of a Lumbar Support Device on Muscle Activity During Abdominal Exercise

The purpose of this study was to investigate abdominal, hip flexor, and low back muscle activation during six abdominal exercises performed both with and without a lumbar support device. Myoelectric activity was monitored with surface electrodes over the upper and lower rectus abdominis, rectus femoris, and the L3 level of erector spinae as 32 male subjects performed the six exercises recommended in the product instruction manual both with and without the product. Significant (p < 0.0125) differences in myoelectric activity were found across some but not all levels of exercise difficulty, but no difference was found at any of the four muscle sites between exercises performed with as compared to without the lumbar support device. These findings contradict the notion that a lumbar support device isolates the abdominal muscles during abdominal exercise performance.

The effect of surgical floor mats in prolonged standing: an EMG study of the lumbar paraspinal and anterior tibialis muscles

The purpose of this study was to determine whether or not surgical floor mats affect low back and leg muscle activity during prolonged standing. The EMG activity was measured continuously using surface electrodes on the paraspinal muscles of the low back and on the anterior tibialis muscles; the subjects were normal and stood on two different surfaces. Six male subjects were each instructed to stand for two hours on a specially designed surgical floor mat and then, on a separate day, to stand for two hours on a linoleum-covered concrete surface. Six other subjects carried out the same procedure, but stood on the linoleum first. There was no difference in EMG activity obtained from the anterior tibialis muscles and paraspinal muscles of the low back when the subjects stood on the surgical mat, as compared with the linoleum-covered concrete.

Low back muscle activity and pelvic rotation during walking.

Gait variables, pelvic rotations in the frontal and sagittal plane and RA-EMG (rectified and averaged EMG) of the three columns of the intrinsic lumbar back muscles (= ILBM) were recorded simultaneously during 48 succeeding strides of 11 subjects on a treadmill. Bilateral activity is found in all parts of the ILBM during the double support phase. After right heel strike the right ILBM (and after left heel strike the left) show in most cases more activity than the contralateral ILBM. This is especially so in the intermediate and lateral columns, which consist mainly of the longissimus thoracis and the iliocostalis lumborum muscle and less so in the medial column, made up mainly by the multifidus and spinalis muscle. This difference is probably due to the difference in moment arm for the two directions. Pelvic rotations are described, but no evident relationships between pelvic rotations in the different planes and ILBM-activity could be seen, probably because the changes in the position of the torso are of more importance.

Electromyographic Evaluation of Arm and Torso Muscles for Different Postures in Windsurfing

This study evaluates the action of 20 selected arm and torso muscles. The subjects were 19 windsurfers of different skill levels. Muscular activity was recorded electromyographically, using surface electrodes. The subjects were standing on a specially devised windsurf simulator in order to keep the different surf postures as standardized as possible. Through two-way ANOVA techniques, the electromyographic activity relative to its maximal isometric value was compared for different muscles, surf postures, and skill levels. Also, differences between the left and right sides of the body were investigated. From the results, the following may be concluded: (a) As all muscles display rather low activity (an average of less than 20% of their maximal isometric values), windsurfing does not seem very demanding of muscular force. (b) The M. flexor carpi radialis, together with the M. erector spinae, tend to exhibit higher levels of activity for beginners, which suggests, respectively, a more rigid grip on the wishbone and stronger low back muscle activation in order to keep a correct posture, (c) Left–right asymmetries mainly occur for symmetrical body postures, especially for the M. flexor carpi radialis and the M. erector spinae. As for the M. trapezius (pars superior), experienced surfers tend to display a dominant right asymmetry, (d) Muscle activity does not exhibit significantly different values for various surf postures. However, typical deviating postures, as observed in beginners, may induce higher levels of muscle activation.