Posture
Dr Mandal, balanced sitting posture on
forward sloping seat #1
Dr. A.C. Mandal from Copenhagen has commended on "Balanced sitting posture on forward sloping seat" : Our industrialized society is transforming into an information processing society in which more employees are transacting business while sitting 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 (long-standing) back pain. The most likely explanation is that we are sitting in 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. (fig. 1)
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. 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 sitting posture cannot be maintained for more than one or two minutes, and usually results in fatigue, discomfort and poor posture. In 1962, the German orthopedic surgeon, Hanns Schoberth, demonstrated by x-ray photos that in a seated work position, one 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, back S-curve) to an upright sitting position, you bend the hip-joints about 60 degrees and rotate the pelvis axis backwards, flattening the lumbar-curve (kyphosis, reduced back S-curve) 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 (low back) discs. Even the best lumbar 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 (fig.3). 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". (To be continued…)
Luck LI
Musculoskeletal Physiotherapist