Extremely comfortable

Introduction - Mary Gale

Mary Gale is a graduate in Occupational Therapy ­ Sydney, N.S.W.

On graduation Mary spent one year in T.B. Hospital in Perth, Western Australia before returning to N.S.W. where she worked in an industrial rehabilitation unit in a
general teaching hospital. Then she worked in large psychiatric institutions setting up the first therapeutic industrial workshop in N.S.W. taking in assembly contracts. This led to a tour to the U.S.A. to study similar institutions.

After six years working in rehabilitation units in N.S.W. country hospitals, Mary then returned to Sydney to work in rehabilitation in a North Shore Teaching Hospital. Here
Riding for the Disabled was used as part of the treatment. She then worked in the community teaching groups of young disabled adults to ride.

All this led to the recognition that the horse riding position held so much advantage for independence and functional improvement. She designed the Bambach
Saddle Seat using her Occupational Therapist background and her position as Manager in the family's Cable Manufacturing Company.

Mary is now chairwoman of the group of companies her father founded. One of these is The Bambach Saddle Seat.

Expert Opinion

Acknowledged expert opinion on what correct spinal alignment is,
the key to how this is changed within the body and how sitting affects the spinal position.

REINECKER, COLMAN & POPE
"Measurement of Lumbar and Pelvic Motion During
Sitting" in
R. LUEDER & K. NORO
"Hard Facts about Soft Machines ­ The Ergonomics of
Seating" Taylor and Francis Ltd. 1994 U.K

"Pelvic orientation is integral to seated postures and lumbar spine position. Zacharkow (l988) maintains that the key to proper seat support is proper sacral and
pelvic support, which prevents the posterior rotation of the pelvis and lumbar kyphosis by controlling the position of the pelvis through seat pan tilt (Bendix, l987).
Seat design should encourage proper posture, but optimising seating support and seat design requires an understanding of both lumbar and pelvic motion. The
ability to measure such motion can improve our understanding of both seating kinematics and good seating." (p.195)

C.NORKIN & P. LEVANGIE
"Joint Structure & Function" F.A. Davis Co. U.S.A. 1992

Optimal alignment of spine

"Any asymmetry of body segments caused either by movement of a body segment or by a unilateral postural deviation will disturb optimal muscular and ligamentous
balance ­ symmetric postural deviations, such as bilateral genu vacuum*, that disturb the optimal vertical alignment of body segments, cause an abnormal
distribution of weight-bearing or compressive forces on one side of a joint and increased tensile forces on the other side. The increased gravitational torques that may occur require increased muscular activity and cause ligamentous stress." (p.436)

"Structural changes may progress to produce a severe deformity unless intervention occurs at the appropriate time. Deformities can interfere with breathing and other
internal organs as well as being cosmetically unacceptable.

If a curvature is recognised early in its development, then measures may be instituted either to correct the curve or to prevent its increase." (p.441)

Verterbral column scoliosis

"Normally when viewed from the posterior aspect, the vertebral column is vertically aligned and bisected by the line of gravity (L.O.G.) The gravity line falls through the
midline of the occiput, through the spinous processes of all vertebrae, and directly through the gluteal cleft. In an optimal posture the vertebral structures, ligaments and muscles are able to maintain the column in vertical alignment. If one or more of the supporting structures fails to provide adequate support, the column will bend
to the side. The lateral bending will be accompanied by rotation of the vertebrae because lateral flexion without rotation does not occur below the level of the second
cervical vertebrae.

Consistent lateral deviations of vertebrae from the L.O.G. in one or more regions of the spine may indicate the presence of lateral spinal curvature called scoliosis.

The static and dynamic postures at work and during recreational activities may have adverse effects on joint structure and function." (p.440)

"The joints of the lower limbs and the pelvis function as a closed kinematic chain when a person is in the erect weight bearing position because the ends of the
limbs are fixed on the ground and the upper ends of the limbs are virtually fixed to the pelvis." (p.69)

"The curves (of the spinal column) are interdependent, and if the head is to remain balanced over the sacrum, the region between the head and the pelvis behaves as
if it were part of a closed kinematic chain. Changes in the position of any one segment will result in changes in position of adjacent superior or inferior segments."
(p.127)

"The lumbosacral articulation is formed by the 5th lumbar vertebra and first sacral segment. The first sacral segment which is inclined slightly anteriorly and
inferiorly, forms an angle with the horizontal called the lumbosacral angle. The size of the angle varies with the position of the pelvis and affects lumbar curvature. An
increase in this angle will result in an increase in the anterior convexity of the lumbar curve and will increase the amount of shearing stress at the lumbosacral joint."
(p.152)

RENE CAILLIET M.D.
"Low Back Pain Syndrome" F.A. Davis Co. 1995 U.S.A.

"Abnormal dynamic control of the lumbar para spinal musculature, causing erratic lumbar-pelvic rhythm has been postulated as the cause of much low back pain."

"During sitting, the spine normally assumes a kyphoticposture." (p,29)

"Prolonged sitting posture. The kyphotic lumbar posture replaces strain on the erector muscles (M), the supraspinatus ligaments (L) and the posterior annular
fibers. The nucleus (N) of the intervertebral disc (IVD) protrudes posteriorly to compress the posterior longitudinal ligament (not marked) against the nerve
root" (PP.108)

Fig.3-13 (Cailliet)

Fig.3-14 (Cailliet)

"Prolonged sitting causing posterior disk bulge. The kyphotic lumbar posture flexes the spine causing the nucleus (N) of the intervertebral disk to protrude posteriorly to press against the posterior longitudinal ligament (PLL) against the nerve root (NR)" (p.109)

Mary Gale comment.... Dr. Cailliet has written many texts on musculoskeletal pain in scientific detail and accessible explanation of the biomechanics in such easily understood language that the information offers a commonsense guide for doctors and health professionals worldwide and is an acknowledged expert in this field.

STEPHEN PHEASANT
"Anthropometry, Ergonomics and the Design of Work"
Taylor and Francis U.K. 1986

STEPHEN PHEASANT
"Ergonomics Work and Health" McMillan Press U.K. 1991

(Fig.5.2) Pheasant

"The shape of the lumbar curve is mainly determined by the angulation of the sacrum and pelvis. In the standing position, the anterior superior iliac spines and the pubic symphysis are typically in the vertical and the top of the sacrum is inclined forward at an angle of about 30 degrees to the horizontal" (pp.101)

Fig.5.3 (Pheasant)

"The action of sitting down (on a seat of average height but without a back rest) involves a flexion of the knees and a flexion of the trunk on the thighs (of about 90 degrees in both cases) In most people the comfortable limit of hip joint flexion is only
about 60 degrees ­ beyond which the passive tension in the hamstring muscles increases quite rapidly. So the sitting action is completed by a backward rotation of the pelvis of 30 degrees or more, as shown in Fig.5.3.

The weight is taken on the ischial tuberosities, and the top of the sacrum (which in the standing position is inclined forward by about 30 degrees) comes to lie more or less
horizontally. If the overall line of the trunk is to remain vertical, there must be a compensatory flexion or flattening of the lumbar spine (by an amount equal to the
backward rotation of the pelvis). According to Akerblom (1948), the lumbar spine is flexed to its limit in the relaxed or "slumped" sitting position ­ so the weight of the trunk is probably supported by the ligaments rather than the muscles".

"The flexion of the lumbar spine which occurs during relaxed sitting includes a deformation of the intervertebral discs, which increases both the tension on the posterior part of the annulus and the pressure within the nucleus." (pp.105)

"People with back problems are often advised to `sit up straight' ­ in order to maintain the lordosis and reduce the loading on the disc. This seems to be bad advice if it requires static tension of the muscles of the back in order to do so." (pp.105)

"To `sit up straight' requires a muscular effort to overcome the tension in the hamstrings. The pelvis rocks forward on the ischial tuberosities and the lordosis
is restored. The principal muscle involved in this movement (of resisted hip flexion) is the iliopsoas." (pp.104)

"Sedentary work is known or suspected to have an adverse effect on a number of bodily functions. A number of epidemiological studies have shown a significantly increased risk of cancer of the large bowel in sedentary workers." (pp.107)

"Prolonged sitting in a cramped position has been known to cause deep vein thrombosis (the formation of blood clots in the legs) which may result in pulmonary embolism.

Prolonged sitting (e.g. over an eight hour working day) leads to an average increase in the volume of the leg and foot of between 2% and 5% (depending on the amount of leg movement allowed) and up to 7% in some individuals compared with about 2% for standing and walking" (Winkec. 1985)

"It is generally recognised that lung function vital capacity, forced expiratory volume etc, is diminished in the sitting position." (p.108)

Mary Gale comment.... STEPHEN PHEASANT Ph.D FERGS, was a Consulting Ergonomist who lived and worked in London. He won the 1987 Techmart Technology Trophy for explaining science in plain English In 1986 Dr. Pheasant was awarded the Sir Frederic
Bartlett medal by the Ergonomics Society for his research into posture and strength.
Stephen Pheasant is internationally recognised as a great researcher and scientific writer. His origin as a Physiotherapist gives a special clarity of application to serious science to the real world for his readers and followers.

Publications:

• "Ergonomics work and health"
• "Body Space"
• "Anthropometry; ergonomics and design ergonomics"
• "Standards and guidelines for designers and anthropometrics ­ an introduction."

Conventional seating can undoubtedly be described as "cramped" due to the deformation of the spine resulting from pelvic backwards rotation necessary to sit with hips and knees at 90 degrees flexion ­ worst of all is the wheelchair, the stroller, the
easy chair, the car seat etc. etc.

The Design of the Saddle Seat is specially contoured to hold the pelvis in its neutral position (as in standing) and stabilise it there so that trunk flexion now takes place at the hips not the lumbar spine, maintaining natural spinal curves, avoiding deformation of the discs as well as abnormal dynamic control which causes postural stress.

The Bambach Saddle Seat provides for an upright spine, opening the abdomen and chest for freeing the organs within for maximum function which means better digestion, better oxygenation of blood, better blood flow to the brain and other organs. In the Bambach Saddle Seat there is freedom for the legs to take some weight bearing with full plantar contact for the feet. Legs are making small but constant movements resulting in improved blood flow, improved lymphatic return, healthy joints which are within mid range rather than in static flexion (avoiding contractures).

Fig.5.4(Pheasant)


Fig.5.3(Pheasant)

DENNIS ZACHARKOW, P.T.
"Posture, Sitting, Standing, Chair Design and Exercise"
C. Thomas U.S.A. 1988

"Nearly all of modern man's activities encourage the forward position of the arms and head, with the tendency of gravity to pull the body forward and
downward." Preface vii

The most universal physical occupation of civilised human beings is sitting" (Bennett 1928)

" of all the machines which civilisation has invented for the torture of mankind ... there are few which perform their work more pertinaciously, widely or cruelly than the chair. It is difficult to account for the almost universal adoption, at least in this country, of such an unscientific article of furniture (Aveling 1879) (The chair is) "The most
atrocious institution hygienically of civilised life" (Coghill 1941)

" We have agreed to adjust our bodies to the dictates of chairs; only rarely do we find a chair that in its design has contracted to fulfil the requirements of the human body .... We have accustomed ourselves to habitual modes of use that are literally disfiguring". Preface vii

"We cannot afford to ignore posture, primarily because to do so creates such widespread misery, and secondly because the costs, both the social costs of unnecessary disease and the direct costs in lost productivity are more than any modern industrial nation should be prepared to pay (Corlett l981) Preface vii ­ viii.

"When an individual goes from standing to a relaxed, unsupported sitting position, the pelvis rotates backwards and there is a subsequent change of the lumbar lordosis to a kyphosis."(p.52)

Zacharkow says that Schoberth 1969 stressed that the shape of the spine in sitting "depends directly on the position of the pelvis"(p.53)

As Zacharkow says "seating and posture authorities from over one hundred years ago, stressed the importance of proper seating and postural habits for both school children and adults" (he cites Bennet 1928).

"Civilization has imposed upon the child one of the most distinctly sedentary occupations yet devised and says it is in the artificial environment of the school where the child's postural habits will be formed for life" Preface viii

"Unfortunately sitting is probably the unhealthiest of all the prolonged postures of the human body (Helbig 1978). Whether due to poorly designed chairs or workstations, musculoskeletal factors or improper movement patterns, a slouched kyphotic sitting posture predominates among observed sitting postures. However, compared to poor standing postures, poor sitting postures will usually always be accompanied by a
greater degree of spinal flexion. As a result, a prolonged, slouched sitting posture with a kyphotic lumbar spine has been frequently implicated as a major cause of low
back pain (Keegan, l953; Kottke, 1961; Cyriax, 1975;McKenzie, 1981).

This prolonged, slouched sitting posture has also been implicated as impairing both respiratory and digestive functioning. (Goldthwait, 1909; 1915;Schurmeier, 1927; Bunch and Keagy, 1976; Goldthwait et al, 1952). This posture can constrict the abdominal and thoracic cavities and increase the pressure on the abdominal viscera. (pp.51)

Mary Gale comment.... Dennis Zacharkow's outstanding review and analysis of seating and its history outlines the detrimental effect of seating and the fact that this bad effect has been noted and recorded at least since 1892 (Bobrick) so in spite of this knowledge nothing has seriously challenged traditional design concepts until the Saddle
Seat.

E. GRANDJEAN
"Fitting the Task to the Man an Ergonomic Approach"
Taylor and Francis U.K.1981

"Effects of bodily posture on the pressure inside the disc between the third and fourth lumbar vertebrae, expressed as a percentage of the pressure when standing erect.

The previous chart shows that disc pressure is greater when sitting than when standing.

The explanation lies in the mechanism of the pelvis and sacrum.

During the change over from standing to sitting down:

(a) the thigh is used as a lever;
(b) the upper edge of the pelvis is rotated backwards;
the sacrum turns upright;
(c) the vertebral column changes from a lordosis* to either a straight or kyphotic curve." (p.53) Illustrated in Fig.41

Fig.41 (Grandjean)

"lordosis" means that the spine is curved forwards as it normally is in the lumbar region
when standing ­ see FIG.41

R.A. MCKENZIE M.N.Z.S.P. M.N.Z.M.T.A.
The Lumbar Spine ­ Spinal Publications N.Z. 1981

"A poor sitting posture may produce back pain in itself without any additional other trains of living. We have all seen patients who entered an airliner, a car, or even a common lounge chair in a perfectly healthy and pain free state only to emerge hours later crippled with pain and unable to walk upright" "Once a person has been sitting in a chair for more than a few minutes the lumbar spine assumes the fully flexed position. In this position the musculature is relaxed and the weight bearing strains are absorbed by
the ligamentous structures .... relaxed sitting for any length of time places the lumbar spine in a fully stretched position. This will become painful, if maintained for a prolonged period." "From my own clinical observations I conclude that the lumbar disc is most commonly damaged in flexed positions especially where flexion is sustained"

Mary Gale comment.... Robin McKenzie from New Zealand is one of the most revolutionary minds to change attitudes to back and neck pain. He was probably the first to point out that sitting was as a serious cause of back injury which is still in real terms being ignored ­ why?

TOM BENDIX
"Low Back Pain and Seating" in R. LUEDER & K. NORO
"Hard Facts about soft Machines ­ The Ergonomics of Seating" Taylor & Francis U.K. 1994

`The incidence of low back pain (LBP) increases with seating duration. The distribution of LBP in relation to workload (in Fig.10.1 p.148) Magora (1972) divided people into three groups in accordance to the amount of time they sat at their workplace. One group sat there for more than four hours a day (fig.10.l right) another group sat infrequently (left) and many of them adopted physically heavy work. The third group sat 2-4 hours in effect, they alternated between sitting, standing, walking and even lifting. Although the group to the left suffered the most from LBP, apparently, the incidence of the predominantly seated group had almost as much LBP, and LBP
reduces as postural variation is increased. As a result, the primary principle of seating is: avoid sitting for extended durations. The incidence of LBP in seated tasks can best be addressed by promoting movement rather than optimising the design of chair and table."

Mary Gale comment.... Bendix obviously agrees with McKenzie and all the others who
say sitting will injure your back. However, Bendix simplistically offers an unrealistic solution ­ don't sit so much! This cannot work for obvious reasons and Bendix generally has always held a rather depressed view of the solutions ­ however, he has made good contributions to the debate and did experiment with a saddle type sitting position. The Bambach Saddle Seat answers the problem by correctly positioning the spine via the pelvis.

DR. A.C. MANDAL
"The Seated Man" (L'homme assis)

"All our knowledge of human anatomy is based on dissections carried out at the beginning of the 16th century ...

... the bones, ligaments and muscles of the prone body where depicted and these drawings have later been turned 90 degrees and used to demonstrate what is called
the `normal' ­ anatomical position.

No body seems to have shown much interest in the position most of us adopt for most of the day ­ the sitting position.

Many people believe that the hip joint bends at a right angle when one sits upright in an ordinary chair. Actually the situation is rather more complicated ­ the bend occurs in two places ­ 60 degrees in the hip joint and the remaining 30 degrees by straightening out the curve in the lumbar region.

Schoberth (1962) showed the rotation of the pelvis when moving from the standing to the sitting position: the hip joint bends slightly less than 60 degrees... when he examined 25 people, Schoberth found an average flattening of the lumbar curve of 30.4 degrees took place on sitting down.

In our modern industrial society most people spend a good deal of their lives sitting down. This is the case in education, administration, transportation and in industry but even when not at work, the community spends
much of its spare time in a chair.

... The seated working position mainly involves bending the back, and this leads to training bones, discs, joints and ligaments. More and more people are afflicted with some sort of back ailment ... straining the back for many hours a day by sitting in a stooped position is probably a significant cause of backache.

Already at the age of 5 or 6, school children have begun to sit for long stretches with a completely bent back as they work over their school desks. American Primary Schools take in about two million new pupils each year; the majority of them arrive with an almost perfect posture, many of these children will leave school some eight or ten years later with a ruined posture. Especially in the taller students, the gradual deformation suffered has become so pronounced that they retain the bent back and hunched shoulders even when standing."

"The position of the back when we are relaxed ­ for instance, when lying on our sides the hip joints are bent 45 degrees (or 135 degrees if the upright position is 180 degrees). This is the resting position of the hip joints where the muscles at the front and the back of the thigh are in relaxed balance, and where the back has a concave backward curve. When the thighs are bent upwards at the hip joints, as in D and E, the muscles at the back of the thigh (hamstring and gluteal muscles) tighten. These muscles are attached to the back of the hip and seat bones and thereby produce a rotation of the pelvis around a transverse axis. The lumbar curve is therefore altered in
D to a slight convex shape which in E is even more pronounced. The muscles at the front of the thighs are completely relaxed.

Fig.20 (Mandal)

Theoretically, a sitting position where the angle at the hip joints was about 45 degrees would be ideal, since in this position the muscles at the front and the back of the body are in balance. In practice there is an obvious similarity between Keegan's `normal' position and the way a horse rider sits.

Fig 21 (Mandal)

Fig.22 (Mandal)

When riding a horse, the hip joints are in the resting position at an angle of about 50-60
degrees and the lumbar curve is maintained. The rider is in balance. One of the reasons why a horse rider can sit up and still maintain a lumbar curve is that the thighs are at an angle of 30 -40 degrees below the horizontal (fig 22) with a maximal bend of 60 degrees at the hip joints, the axis of the pelvis can remain vertical so that the body's centre of gravity remains vertically above the point of support (the seat bone). The centre of gravity lies at the front edge of the 9th thoracic vertebra. This means that the twist (turning movement) which comes when one sits on an ordinary chair with thighs horizontal is avoided."

Mary Gale comment.... Dr. Mandal is a Doctor, Surgeon and pioneer of reality based ergonomics who had the insight and imagination to illuminate the fact that conventional seating fails to provide good spinal posture.

Dr. Mandal is the person I most relied on for the evidence to make sense out of my observation that disabled people who could not sit without quite a lot of support on a conventional seat or wheelchair, could sit unsupported and stable on horseback.

His work led to many others who had not only observed but documented the damage done to backs and the whole body of humans using conventional seating.

Dr. Mandal had the energy and courage to challenge the daunting complacency and closed minds of the entrenched ergonomic experts and the health care professional generally.

Dr. Mandal pointed out how people, especially children will tilt their seats on its front edge to achieve the effect of tilting the pelvis forward which opens the hip joints to 45 degrees thus restoring the lumbar curve.

He also noted that ­

"Lumbar support has for the last 30-40 years been the magic formula for a good sitting position. It has been accepted by all ­ but the effect has never been controlled by anyone. .... Many of the scientific experiments which have been carried out have concentrated on small, minor details of the problems of the sitting position.

..... Experts have tried far too hard to force people to use special sitting positions on standard furniture with standard heights, even though it is obvious that very few people actually use the furniture properly.

.... As the furniture hardly can be much worse than today I can only encourage everyone to start experimenting"

Dr. Mandal has successfully defied the entrenched, comfortable, anthropometric dark age thinking and has been the best thing that has happened to improve the health
outcomes for seating.