Sitting up straight is not the best position for office workers, a study has suggested. Scottish and Canadian researchers used a new form of magnetic resonance imaging (MRI) to show it places an unnecessary strain on your back. They told the Radiological Society of North America that the best position in which to sit at your desk is leaning back, at about 135 degrees. Experts said sitting was known to contribute to lower back pain. Data from the British Chiropractic Association says 32% of the population spends more than 10 hours a day seated. Half do not leave their desks, even to have lunch. Two thirds of people also sit down at home when they get home from work. The research was carried out at Woodend Hospital in Aberdeen. Twenty two volunteers with healthy backs were scanned using a positional MRI machine, which allows patients the freedom to move - so they can sit or stand - during the test. Our bodies are not designed to be so sedentary Traditional scanners mean patients have to lie flat, which may mask causes of pain that stem from different movements or postures.

In this study, the patients assumed three different sitting positions: a slouching position, in which the body is hunched forward as if they were leaning over a desk or a video game console, an upright 90-degree sitting position; and a "relaxed" position where they leaned back at 135 degrees while their feet remained on the floor. The researchers then took measurements of spinal angles and spinal disk height and movement across the different positions. Spinal disk movement occurs when weight-bearing strain is placed on the spine, causing the disk to move out of place. Disk movement was found to be most pronounced with a 90-degree upright sitting posture. It was least pronounced with the 135-degree posture, suggesting less strain is placed on the spinal disks and associated muscles and tendons in a more relaxed sitting position. The "slouch" position revealed a reduction in spinal disk height, signifying a high rate of wear and tear on the lowest two spinal levels.

When they looked at all test results, the researchers said the 135-degree position was the best for backs, and say this is how people should sit. Dr Waseem Bashir of the Department of Radiology and Diagnostic Imaging at the University of Alberta Hospital, Canada, who led the study, said: "Sitting in a sound anatomic position is essential, since the strain put on the spine and its associated ligaments over time can lead to pain, deformity and chronic illness." Rishi Loatey of the British Chiropractic Association said: "One in three people suffer from lower back pain and to sit for long periods of time certainly contributes to this, as our bodies are not designed to be so sedentary." Levent Caglar from the charity BackCare, added: "In general, opening up the angle between the trunk and the thighs in a seated posture is a good idea and it will improve the shape of the spine, making it more like the natural S-shape in a standing posture. "As to what is the best angle between thigh and torso when seated, reclining at 135 degrees can make sitting more difficult as there is a tendency to slide off the seat: 120 degrees or less may be better."

E-mail this to a friendCornell University Ergonomics Web DEA 3250/6510 CLASS NOTES Sitting and Chair Designpurchase used wheelchair 1. Introduction - Antub chairs uk only estimated 50% of people in the industrialized world suffer some form ofmesh office chair original back complaint and many of these are related to poor seat design. used wheelchair lift parts sit and what we sit on affects the health of the spine. table chair rental madison wi is the most frequently damaged (L4 and L5). used rocking chair uk

The vertebrae in the lumbar region are the largest in the spine. 2. Posture - the relative orientation of parts of the body in space.buy backrest for office chair online india 3. Biomechanics of Sitting - depending on chair and posture, somecheap barber chairs used proportion of total body weight is transferred to the floor via the seatikea dining chair diy pan and feet, armrests, and backrests. 4. Sitting Postures - Sitting with the knees and hips flexed, pelvis rotated backward leads to minimize lordosis, flat, or even kyphotic lumbarThree types of sitting postures normally distinguished: 5. Factors Influencing Posture - 6. Preferred Sitting Angle - Sitting leads to 40 - 90% more stress

on the back (disc pressure) than standing posture. 7. Seat Design Criteria Back to DEA 3250/6510 menuOur industrialized society has transformed into an information processing society in which more employees are transacting business while proper sitting posture suffers for long periods of time. With the advent of the information processing age, it is becoming increasingly clear that there is a significant mismatch between people and the furniture in their working environments, as is evident from the increasing numbers of employees suffering from chronic back pain. The most likely explanation is sitting posture. We are not aware of best sitting positions, and sit the wrong way, thereby abusing our backs, necks and arms. Experts from all over the world have formerly been of the opinion that the proper sitting position is the right angle or erect position, illustrated by this selection of drawings that form the basis for international standardization, anthropometrics and the training of furniture designers.

For the last century, work chairs in schools, factories and offices have been designed for sitting upright, with the hip, knees and ankles all at right angles. Until recently, it was widely believed that people sat with a 90-degree bending of the hip joint while preserving lordosis (concavity) of the back and that this equated to the best posture while sitting. The erect posture looks very nice, but it is impossible to sit this way for long and there is no scientific basis for it. It is entirely based on wishful thinking, morals and discipline from the days of Queen Victoria. This erect “proper sitting posture” cannot be maintained for more than one or two minutes, and usually results in fatigue, discomfort and poor posture. Why your sitting posture doesn’t resemble the popular diagrams. In 1962, the German orthopedic surgeon, Hanns Schoberth, demonstrated by x-ray photos that in a seated work position, you can only bend about 60 degrees in the hip-joints, not 90 degrees as shown in the drawings in fig.1.

This means that when moving from a standing (lordosis) to an upright sitting position, you bend the hip-joints about 60 degrees and rotate the pelvis axis backwards, flattening the lumbar-curve (kyphosis) of the back 30 degrees and straining the muscles of the back. (fig.2) When leaning forward over the desk, you have to bend another 40-50 degrees, and this bending mainly takes place in the 4th and 5th lumbar discs. Even the best lumbar support or built in posture seat or back support will hardly have any influence on the posture when leaning over the desk. J.J.Keegan, an American Orthopedic surgeon, made in 1953 a series of x-rays of people lying on their sides which documented the large movements that took place in the lumbar section of the spinal column as the position changed from standing (a) to right angle sitting (c) and bent-over positions (d).(b) is the natural resting position, as when you lie on your side while sleeping. The lumbar curve is retained and the muscles are relaxed and well-balanced.

A sitting posture that approaches the natural resting position (b), is a more suitable position and allows the spine to carry the body weight in a more comfortable way. This is “Balanced Seating” and the best sitting position to ward off back pain and stiffness. A posture seat that tilts the body forward encourages this natural posture. Opposing muscle groups are balanced and the lumbar curve is preserved producing balanced seating in which the back is straight, the joint angles are open and the muscles are relaxed. This position provides greater mobility and relieves pressure on the lungs and stomach. Children will often tilt forward on the legs of their chair to relieve back pressure. By tilting their chairs forward they avoid bending their backs, allowing the front and back muscles to relax, and thereby sitting in a more comfortable position with a straight back. The fidgeting they may be admonished for is in fact the key to finding the proper sitting position. While riding a horse, the rider sits upright, yet maintains a lumbar lordosis because the thighs are sloping downwards.

This is exactly the same seated posture as the neutral resting position, or sitting on a chair seat that tilts forward. This means the rider is in the perfect position for “Balanced Seating”. To further evaluate the effect a forward tilting seat has on the flexion, forward bending, of the back, I conducted an experiment to document the results. To record the changes in the flexion of the various parts of the body, the anatomical points were marked at the knee-joints, hip-joints, 4th lumbar disc and shoulder joints. The participant was seated at a fixed height for the seat and work surface, but the feet were placed incrementally in three different positions in order to simulate different work heights, and the seat and work surface were tilted. To begin with, the girl was positioned at the conventional right angle (Fig.6), whereupon the chair seat and work surface were tilted incrementally and the position of the feet lowered to simulate an increase in the chair and work surface heights (Fig.7 & 8).

Fifty photographs of each of 3 positions were taken during a period of 10 days to record the changes in the flexion. The findings were significant. Flexion, forward bending, in the hip-joint and back was greatly reduced, preserving lordosis in the lumbar region. The final position (Fig. 8) with feet lowered simulating even higher seat and work surface, is exactly the same as the natural resting position where the muscles are relaxed and the body is in a perfect posture for “Balanced Seating”, the most suitable position for long periods of sitting. Front seat tilt, a posture seat that tilts the pelvis forward, and higher work surfaces are valuable alternatives that can eliminate lower back strain and ultimately prevent chronic back pain. In this half standing position the disc pressure will of course be very low (Lelong 1986). Furniture should be designed to accommodate the natural resting position, in which opposing muscles are well balanced. The resulting posture will enhance the performance, efficiency and well-being of employees.

The recommended chair height is one-third of the person’s height, and the desk height one half. Most people with back pain will find this very comfortable, but for the first weeks you will only be able to sit like this for 5-10 minutes, because your back muscles need training. You may also reduce the tension of painful tendons and muscles of the back by moving to the front of the seat of a traditional chair or by using forward-sloping foam wedge. Most desks are far to low, and this may be improved by placing wooden blocks under the legs. Stand Taller Live Longer: An Anti-Aging Strategy By A.C.Mandal, MD (Copenhagen) Resource: The Seated Man (Homo Sedens) Dafnia Publications, Taarbæk Strandvej 49, Klampenborg, Denmark. Mandal, A.C.: Work chair with tilting seat, Ergonomics, Vol. 19, No 3, p. 157. Mandal, A.C.: The Seated Man (Homo Sedens), Applied Ergonomics, 12.1, p. 19. Mandal, A.C.: Correct Height of School Furniture, Human Factors (USA), 24 (3), 257.