Author Archives: Dr. Henry Sanford

About Dr. Henry Sanford

As a retired consultant in Orthopaedic (Musculo-skeletal) medicine, I was first trained in Orthopaedic Surgery and changed when working with JH Cyriax at St Thomas' Hospital, London, my old teaching hospital. He is regarded as the 'Father' of the subject. I worked as an Associate Consultant in the Rheumatology department, STH, in private practice in Harley St. and the Cromwell Hospital. I have run courses and lectured in in the UK, USA, Belgium, Germany, Scandinavia.

Disc Nutrition & Spinal Movement.

Spinal movement & change of position are important for a number of reasons including IV disc nutrition.

Intervertebral Disc Nutrition starvation plays a part in nuclear degeneration. Nutrients are only barely supplied to the central part of the Intervertebral disc by diffusion from surrounding blood vessels in the circumference and the endplates . Fluid flow also plays a part, especially for the transport of the larger molecular metabolites, and is dependent on the pumping action of pressure changes of the compression/decompression that occur with movement, such as changing from a supine to upright posture (Wilke H-J, 1999.). Some disc narrowing occurs rapidly but is then followed further, as water is forced out over a longer timescale, and is near maximal in about 6 hours. This is evident in diurnal variation when the torso is 15-25 mm longer (and stiffer) in the morning when intra-discal fluid pressure is at its highest. Fluid is expelled during the day, while standing, when the compressive force exceeds the osmotic pressure force (Adams MA, Hutton WC.). During recumbency the disc regains 71% of it’s height in the initial 3.75 hrs but with 3 hrs of upright posture 80% of height loss has occurred. This accounts for some of the early morning stiffness experienced by those with minor degenerative disc changes and also for the change in height of astronauts on their return from a weightless environment.

A prolonged static position is uncomfortable. This should be distinguished from supported static ‘comfort’ which is much sought after by chair manufacturers but may not necessarily be biomechanically sound. On the other hand, what is biomechanically sound is always comfortable.

Spinal movement has a ‘comforting’ effect so that movement is enjoyed . This is due to physiological effects and is slightly different from the rhythmic rocking chair movement which was recommended to President Kennedy for his back pain which has a slightly different method of action depending on pain relief by afferent sensory bombardment of the central nervous system.

Although difficult to quantify in terms of sitting and the design of chairs, it is important to arrange for changes in posture, from reclining to upright, to occur frequently during the day to allow changes in axial loading to benefit disc nutrition. It also allows the user the comfort of movement and helps to avoid the discomfort of point pressure in badly designed systems. Respiration is also said to be helped by avoiding a prolonged cramped posture. General wellbeing, for example, in aiding blood flow and venous return, with other health risks avoided (Aaras, 2000⁴⁵). Rani Lueder, a respected American ergonomist and researcher, reviews the subject of spinal movement and comes down firmly in support of movement based chairs(2002⁴⁵}. Gorman (2010⁵¹), on the other hand, remarked “However the history of chairs with lots of movement is that people don’t like them and they die out pretty quickly…… Also if, as I suggest, pumping and movement is not the central point of low back pain then lots of the justification for such a chair is gone. I have always argued that it is the flexion of the lowest two discs beyond the natural limit that is the central problem. (^”^{48 & see his URL → )}

Sensors integrated into the surface of the seat can alert users who have not changed their position in a long time (.Dr. Thomas Hermann with the Ambient Intelligence research group).

For an account of remediation see ☛ EXERCISE & movement→

In the context of the 2Tilt concept movement is at the users command by entering the stable end-range modes. See ☛The unstable TRANSITIONAL MODE. It’s importance.

How did it all begin? A good start is with the pelvis of A afarensis, an individual known as ‘Lucy’.

Australopethecine bipedalism has resulted in considerable morphological changes to the pelvis when compared to that of other apes. An australopithecine pelvis. Similar to that of a human.

Ilium
SI Joint
Sacrum
hip joint
pubic symphysis
Ischial tuberosity

The pelvis of A. afarensis required rotation of the sacrum to increase the Lumbo-sacral wedge angle. Lucy’s ilium (Togue, Lovejoy 1986⁶⁴⁾ is similar to that of humans, being short and having widely flared iliac blades.

This morphological change is due to the shortening of the pelvic ilium. The iliac blades are rounder and the outer surface face postero-laterally to give an attachment for the origins of the gluteal muscles. These therefore have changed their function from hip extensors to become abductors and lateral rotators of the hip. and are important for stabilising the pelvis on the hip and act to support the weight of the torso at the phase of walking when the contralateral, other leg is off the ground. A failure of this mechanism results in the pelvis tilting downwards away from the affected side and is the basis of the clinical Trendelenberg test. Non-hominid primates, with glutei only acting as hip extensors, therefore have an ambling gait or what doctors would describe as a Trendelenberg gait in a human.

The early hominids, such as Homo erectus, had a brain of 900 cc. and its primitive variant, of 1.8 MYA, found at the Dmanisi (Georgia) site was only 650-780cc. These were probably the earliest hominids outside of Africa. H. sapiens, with a volume of about 1300 cc appeared about 130,000 years ago according to the previous ‘out of Africa’ theory’.

The obstetric pelvis

Lovejoy (Tague, Lovejoy 1986, 2005) pointed out, that the enlarging human brain (cerebralisation) in the foetal head required morphological changes of the pelvis to allow an adequate birth passage and changes of the lower half of the pelvis, composed of the ischium and pubis.
The shortening of the ilium, an effect of bipedalism, results in the consequent unwanted effect of reducing the antero-posterior (AP) diameter of the pelvis and the size of the birth canal. Although this was no great problem for early hominins, such as ‘Lucy’, as they had ape sized heads, it presents a problem in parturition for the larger brained hominids. With the shortening of the ilium, the distance between the hip joint and the sacro-iliac (SI) joints is reduced and the sacrum lies at a lower position in relation to the pubic symphysis. The human cranium is x4 larger than Australopithecine ape, and needs a larger pelvic AP diameter and an increase in width (coronal dimension) and lordotic curvature of the sacrum. In the diagram :- X. True’ pelvic inlet of H.sap . Y. Outlet Z. The mid-plane conjugate diamete, the limiting dimension for childbirth was between “… the pubic symphysis and the centre of the sacrum”

In traversing the pelvic birth canal the human cranium has to engage at the inlet in the transverse plane. In the mid-plane it rotates and change direction during it passage which is allowed by the sacrum becoming curved, with the radius of its arc centred at the pubis. The head finally emerges in an AP plane at the outlet.

The pelvis of A. afarensis requires rotation of the sacrum which increases the wedge angle of each lower lumbar IV discs.

An obstetric dilemma, due to the increasing foetal encaphalisation, was increased by the changes to the pelvis and the lumbo-sacral junction due to the development of bipedalism. Even in the best arranged modern facilities disproportion can occur between the maternal pelvis and the foetal head. Jay Stock, at Cambridge (2011), has pointed out that a variety of other variable factors can also be involved, both for the size of the maternal pelvis and the foetal head resulting in disproportion, including ecological stresses such as the thermal environment and nutrition. Maternal stature, obesity and increasing neonatal growth can be related to dietary shifts such as occurred with the development of agriculture.

next see ☛BIOMECHANICS→

Indoor environment.

The future lies with desk-less stations described under the 4M version and in the Sit/Stand environment. The 2T concept is particularly relevant to this. See The 4M office deskless workstation→

reclined mode In an office with cheap, ordinary desks a 2T chair may seem inappropriate with problems at the desk/chair interface. These are easily overcome with a number of design options (not described here).

However, chairs set before desks, even in serried rows, just see the introduction to the BBC news every evening, still persist. Familiarity bias is strong. So, as in the early days, it is worth returning to considering the desk/ chair interface.

The 2T chair cantilevered from a ‘Delta’ desk. A solution.

This desk has variable height adjustment and its shape allows greater surface area and occupies
30% less floor space than conventional desks. The transparent shielding enables an environment friendly space to be contained. This can evolve into a pod design concept. This concept was suggested to me by the late John Jukes. This design concept has a number of very considerable advantages.

The chair can rotate to face through 270 ̇ Cabling can be led straight to the chair(telephone, computer, adjustments).
The chair occupies no floor space. (zero footprint)
Chair height adjustment becomes irrelevant.
Improves Office design and social interaction.
Adapts to any style of office layout whether formal or informal.
Allows the user a personal space and also view of colleagues.
Can be arranged in a reverse rosette to give immediate interaction with close colleagues.
Can be easily developed into a hub.

The Delta shaped desk that Jukes advocated easily accommodates an office 2 Tilt chair and has a number of advantages. He showed that it occupied 30% less floor space than conventional desk and provides a greater surface area..This desk has variable height adjustment. The transparent shielding enables an environment friendly space to be contained.and can evolve into a pod design concept. An 8 desk rosette can be arranged as shown below :-

Office space.

Analysis by the Cambridge student group working on the 2T project.

They suggested that six chair and desk units can be fitted around a single hub. The arrangement is segmented by 60^o and the users share flat desk space, located on either sides of chair (for storage, paper reference, or telephones).

Each hub occupies a total area of 13.5m². In comparison to Delta workspace layouts, suggested by Jukes, this offers an area saving of 12% compared to the traditional workspace. The individual chair and desk unit offers a similar space usage to the Delta hub, however, it offers a more inclusive design between adjacent units so that open

A layout plan for a small office has been suggested. This included 8 hubs, allowing for 48 staff. The total area occupied is 57.35m² and the area occupied per a worker is 1.19m².

Effects on work space environment
Workers are located in hubs with clear visibility, desirable in the growth of open plan offices. Individuals have clearly defined individual space, however shared side desks help to create group unit.

The layout should feel fairly spacious due to the lack of defined, rigid boundaries. Potential consideration should be given to storage space for bags, mugs etc.
( Hub=Rossette.)

The ‘pod’ design concept.

The Jukes Δ Desk + 2T chair, as described above, can become a pod.

Okamura have produced a pod design that has similarities to the earlier Jukes concept. The chair is reclined with the body supported from head to feet. There is a transparent surround. The chairs are messy and complicated without the ease of the requirements built in to a 2Tilt solution.

Further requirements, essentially the same as those for optimising an office space, suggested by Stephen Bankler-Jukes (Late CEO of OptEnCo – The Optimum Environment Company Ltd). For an overview – See Ergonomics and office stress.

Lighting. The individual lighting unit is an illuminated polarising panel that is lit by high frequency dimmable daylight full spectrum lamps
Ergonomics. The height of each desk can be independently adjusted to sit or stand levels to provide the variety in working posture recommended in ISO 9241 part 5.
Acoustics. Acoustic management means the possibility of using speakers instead of headsets. The front part of the desk is effectively an acoustic box, which contains most of the sound within itself. This is enough to reduce acoustic stress but not enough to make the environment too quiet.
Space & visibility. Users have clear all round visibility so there is no sense of isolation. Each individual has his or her own clearly identified space, which is close enough to provide a sense of group space. The plant filled space in the centre provides enough open space to reduce any sense of overcrowding. The compactness of the desk design may raise issues of staff acceptability. If needs be it can be made larger at a cost of lower revenue per square metre. The layout design should feel more spacious than the existing layout due to the large amount of unoccupied space and the elimination of battery hen regimented straight lines. Details such as space for cups and mugs, operator instructions, handbags etc are to be decided, also, how the desk would work with trainers and coaches.
IAQ. Users will breathe fresh air that has been fed into the plant zone at a cool temperature of 18C where it is picked up by each workstation then filtered and ionised. The speed of the airflow is adjustable by the user as is the temperature of the low temperature radiant heating panel. The object is to provide a thermal comfort with a cool head and warm legs and feet. The air intake will not include recycled air.
Plants. These are primarily for function not decoration. They absorb CO2, generate oxygen, absorb volatile organic compounds and generate humidity.
Footprint. The increase in population density both requires and enables the cost justification for upgrading of the support facilities i.e. rest room, canteen etc.
Costing. Preliminary indications indicate that increased space and personal productivity will generate an additional £5- £10 p.a. in net revenue for each £1 of cost (2006). These proposals will create reductions in:-
1. Space, power and heating costs
2. Wastage, recruitment, training, sickness and absenteeism costs. c

Call handling time and non-productive time costs.

Office ENVIRONMENT

Healthy office

1 Reply

2T Chair Desk interface

The 2T Chair Desk interface becomes largely redundant as desks become a thing of the past with new office workstations. The future lies with desk-less stations described under the 4M version. ☛ The deskless office chair→

The 2T chair cantilevered from a ‘Delta’ desk. A solution.

The chair can rotate to face through 270 ̇ Cabling can be led straight to the chair(telephone, computer, adjustments).
The chair occupies no floor space. (zero footprint)
Chair height adjustment becomes irrelevant.
Improves Office design and social interaction.
Adapts to any style of office layout whether formal or informal.
Allows the user a personal space and also view of colleagues.
Can be arranged in a reverse rosette to give immediate interaction with close colleagues.
Can be easily developed into a hub

•This desk has variable height adjustment. The transparent shielding enables an environment friendly space to be contained.and can evolve into a pod design concept.

An 8 desk rosette can be arranged as shown Screen Shot 2015-04-14 at 13.02.45

⟶ For hubs, D-desks and layout see 2T IN THE OFFICE.

Next see ☛ The deskless office chair→

School chairs & desks

A quick look through retailers of school chairs and desks failed to find any models that had the slightest regard for ergonomics. Astonishing! Especially as this may be where adult LBP begins.

School chairs

This post is not intended to be authorative on children’s and school seating. In view of the importance of the subject a few points arise from the spinal biomechanics .

It would seem that non-western populations that do not habitually sit in upright chairs have a low, or no, incidence of LBP and are able to squat and sit slumped. It has been shown that they have a larger sacral-horizontal angle and a larger lumbo-sacral (L5/S1) angle which, safely, does not reduce below 0° on flexion (see. ‘Angles & lordosis). This may partially represent a racial genetic advantage but cannot be the whole story as the same people incur the same incidence levels of LBP when the upright sitting posture is adopted in childhood. This suggests that adverse mid- upright sitting postures in childhood modifies the spinal bio-mechanics and so may determine future liability to LBP. Early stretching of the posterior elements of the motion segment which, in turn allows spinal joint instability and early disc degeneration (see CTD ) is likely. It may even be the fundamental cause. More research is required.

On this assumption, school chairs or chair/desk combinations should be properly designed to ensure, as far as is possible, bio-mechanical optimisation. This can be done at no great cost using a FTS tilting seat and a back rest with Iliac support in a height adjustable desk/chair unit. In theory, at least, this would avoid the stretching of the posterior stabilising ligaments. Some positional instability allows movement which aids the pumping action of position changes for the nutrition of the IV disc, also a factor helping to avoid later degenerative changes.

There are some general childhood requirements:-

Sturdiness so as to withstand a childs natural curiosity to test to destruction.
Allow freedom of movement for small children with short attention spans.
Absence of any holes and crannies into which fingers or other objects can be stuck.

School and schoolroom requirements

Cost considerations
Stackability.

The essential bio-mechanical requirements for school chairs are the same as for an adult:-

A forward tilted seat
or/and Iliac support.
Height adjustability of desk & chair.
Avoidance of, commonly advised, incorrect systems.
A 2T chair is hardly practical in a school environment, but not at home.
The requirements for a school chair/desk may be different from those of a small child. Small children seem to enjoy and do well on a large ball. This ensures a FTS, freedom of movement and seems to be safe.

My ‘off the cuff’ idea of a design for a school chair and desk combination. →

Note that these measurements are considerably greater than the ISO recommendations – it is difficult to understand on what the latter measurements were based.

←I was amazed to see something almost identical on eBay although possibly intended for adults and not much ‘Adjustment’. I tend to decry adjustment for adult seating See → Adjustments .

Knoll Another chair by Knoll for adults seems relevant.

An existing good start, for consideration, is a model from the German firm MOLL. The design suggests that it still subscribes to the outworn ‘correct’ upright sitting concept. This may be a necessary constraint.

⟵ The ‘Scooter’ is the simplest and, possibly, best.
Adjusts easily to the growing size of the child.
Allows movement. Absence of arm-rests may help here.
A FTS to allow the hip angle to be “slightly open (more than 90°)”. Ideally should be greater, to 130°.
Some degree of pelvic support. Could be improved.

A quick look through retailers of school chairs and desks failed to find any models that had the slightest regard for ergonomics. Astonishing!

The FIRA publication is worth looking at in this respect “We as a nation are embarking upon a major investment in our schools and teaching methods – but our school furniture design has changed little from the post-war era. It’s not just about aesthetics ….This call to action comes from FIRA (Furniture Industry Research Association) in response to requests from government, purchasers, parents, teachers and children to make a change”.

http://www.fira.co.uk/document/safe-seats-of-learning.pdf

They adhere to British Standards BSEN 9241 Pt 5.

The bio-mechanics of the charming looking chair pictured on the front page seems to be as adverse as it gets. It is not clear if this is being recommended or dis-recommended. Can you spot the faults?

See chair remediation→

Comment

From Rani Lueder
There is a large amount of evidence that children – particularly as they approach puberty – are prone to back pain, that these symptoms can be medically established, and that their rate of pain compare with those of adults. Not that their symptoms mean the same thing as they do in adults, mind you, but they’re comparable. And children and adolescents who have symptoms are particularly prone to exhibit evidence of back symptoms later in life – that is, a decade or so later. My book is beginning to look dated at this point (there’s so much research) but unfortunately I can’t point you to a more up to date resource, it’s still the most thorough review.

Submitted on 2013/11/04 at 8:42 am | In reply to Rani Lueder.

Thank you, Rani
Very helpful. I must admit to being shocked when I looked at the children’s chairs being retailed, at least in the UK.
Henry
Dr Henry Sanford

Next ☛ A FULL SOLUTION→

Various chairs. How do they measure up?

Ergonomics of sitting safely. My remarks are intended only to illustrate points in relation to the 2T (3M) concept. Much work has been done in the design of office chairs as a result of the general perception that ’correct Ergonomics of sitting safely’ is required for the avoidance of LBP. In spite of the efforts of chair designers prolonged sitting still results in backache.

The spine is only affected by the bio-mechanics presented to it. An upright work mode can only be a partial solution and can only go some way to meet the spinal Screen Shot 2018-11-28 at 15.32.37 bio-mechanical challenge. A knowledge of the 2T concept, a full solution, is helpful for the understanding of the following comments. Hype and selling points, bells & whistles and apparent comfort are irrelevant. I have yet to see any office chairs on the market that I could recommend for prolonged sitting although the information has been available since 1989.

A garden recliner. It has only two positions. Both are shown. Simple but very comfortable with an easy, adjustment free transition. It is a 2T system and provides a clue to the development of an office chair and is a forerunner of many of the principles expressed.

Screen Shot 2013-09-19 at 17.01.57 Another garden chair, from France, which now claims to be a recliner and make zero gravity a selling point. I approached them originally with this suggestion and heard no more. The leg-rest retraction is interesting, simple and has points for a 2Tilt construct.

I do not know if their move was post hoc or propter hoc.

Screen Shot 2013-09-19 at 17.07.27
This young lady looks very happy! But perhaps she would be happier with leg and neck support? →

Screen Shot 2013-09-19 at 17.08.56 A common sight. If he had correct neck support he could get on with some work. Admittedly he would need a better computer screen, correctly placed. Nice view!

An example of a zero-gravity, reclining chair. It has variable tilt and in the fully recline position the legs are above the level of the head. The headrest is adjustable and pelvic support is possible. The upholstery might give rise to heat build up. See ☛Recliners→.

Screen Shot 2014-02-13 at 13.06.54

← Good in theory, but I have never actually dared to sit on one.

The Hermann Miller Aeron

The Aeron chair has been chosen for consideration as an example of a top-range, highly engineered and carefully designed upright office chair. Originally launched in 1994 and developed from an earlier study into furniture for the elderly, with a recliner chair as the inspiration, it incorporated a mesh construction in place of, the then, more common foam-filled upholstery. I was impressed on first seeing this chair and wrote to the effect that it could be seen in most design offices. I liked it’s ability to recline to 45°, as a step towards a 2T Chair, and the mesh construction and remarked that it dissipated heat build-up but also support, of which,at that time, there was none. It shares the same biomechanic problems as any other mid-upright chair. Like them it seems to have reached the limits for remediation with only limited success.

The late John Jukes, who was investigating the incidence level of office musculo-skeletal symptoms, wrote to me “The ergonomic stress symptom pattern is no different to the average office chair”. He also told me that he suggested to them that Gorman’s ‘pelvic support’ should be incorporated in their office chairs but said this was ignored at that time. Perhaps annoyed by his rebuff, having at last achieved a form of pelvic support, he later wrote “Henry. A large percentage of staff throw out the lumbar support bar because it is too hard and uncomfortable. They do have a pelvic support now. However it has the same problem in that the support is concentrated at the base of the spine and not the iliac crest.” He later wrote “It now incorporates pelvic support and so can be regarded, with reservations, as offering a semi-partial solution to the problem of LBP”. The Gorman design, suggested to them by John Jukes in the first place might have saved them and their clients, 2 decades of trouble. Gorman’s “Pelvic Posture Principle” is not generally understood and pressure is still directed above the pelvic brim and to the midline and not to the iliac crests. ☛Pelvic support→

Evident in the photograph, above, the seat is convex, an example of the ‘Off Load’ system’ which the Makshous study showed to have biomechanic advantages. The convex front half goes a little way to being a FTS accounting for some users admitting that they usually perched on the front edge. This seat shape allows this chair to be upgraded from a simple upright chair.

Mirra 2 HM The pelvic support, included with the ‘Off Load’ system, is the only component of the Hermann Miller, and other, ranges that can lift these otherwise well designed chairs from at least one of the seriously adverse effects of the common upright chair (‘machines for making backache’). The back support only becomes ‘iliac’ at it’s lowest adjustment, A more user friendly plastic band whose depth can be adjusted replaces the uncomfortable adjustable (usually wrongly) rod. The back view shows that it is still slightly too high and likely to act as an adverse lumbar support.

The new Lino chair by Herman Millar mentions sacral support, which ‘nudges you into better posture’. “…the cleverest way is a design feature that subtly corrects your posture so that the chair doesn’t need to be adjusted so much—and thus doesn’t need all the moving parts that make other task chairs expensive.” (This sounds as if they have read this work.) A step in the right direction, at last, some 20 years after the recommendation of Jukes. The photograph is of one of the co-designers, Sam Hecht of Industrial Facility, photographed by Gerhardt Kellerman.

The OKAMURA ATLAS chair & Cruise concept.

“Looks familiar, Henry?” was the message from John Jukes about this office chair. Sure enough it showed the semi-reclined work position that I had been advocating since 1998. Ten years after my original suggestion, Okamura has recognised the importance of a reclined mode in their Cruise concept. However, the 2T concept has additional requirements for it’s implementation to be effective for an office or work chair and not to be simply a recliner or a ’zero gravity chair’.

The designers had probably not seen the principles that I had formulated and tested at Cambridge, to make this mode optimally functional. In my opinion, the reclined mode made this chair the best on the market at that tme. It has plenty of room for improvement. For further consideration see ☛ Okamura Atlas→

The OKAMURA CONTESSA chair

It includes some of my 2T points. Okamura had, by now, seen my ‘Sitting Safely’ (protected by an nda) and it is possible that the designer, Giugiaro, had also seen it too.

The OKAMURA LEOPARD chair

Not intended as a work-chair, it is aesthetically superb and looks right, however the fixed head-rest is only excellent for contemplating the ceiling. A forward tilt is possible but there is no contouring to prevent slipping and it seems to be used for rising from the chair. The intermediate range is stiff which makes it difficult to fully recline. The seat is fixed at a low level. This allows the feet to rest on the floor in the reclined mode, as shown. I am told that this causes problems for tall people who have tried it and an adjustable table may be required (no bad thing). Essentially a waiting room chair, jt would ne unsuitable for office work.

Pledge BT3 20/20 (Task)

Gorman, an engineer turned chiropractor, worked with PLEDGE to produce office chairs incorporating pelvic support. Controlled trials by John Jukes of VESTRA showed them to be significantly more effective in reducing back shoulder and neck pain, compared with similar chairs. and advocated the Pledge BT3 20/20 (Task) pelvic support chair to reduce LBP problems in the optimised office environment. These office chairs, incorporating Gorman’s ‘pelvic (actually ‘iliac’) support have been in use over the last 10 years and some 40,000 are in use. It has been estimated that considerable savings have resulted due to reduced absenteeism and increased staff performance due to the improved ergonomics (Jukes J). Initial outlay of cost is also considerably less than the two chairs considered previously.☛ Pelvic Posture→

The Howarth Zody

This is another good upright office chair that incorporates ‘Pelvic Support’, here called PAL™. This allows it to be considered as a semi-partial solution for full Safe Sitting.

As with any upright chair it has the inherent disadvantage of the increased axial loading.
It has the advantage of a forward tilt mode and a possibly adequate pelvic support in the upright mode.
It boasts high engineering, ergonomic research based on maximising comfort and many adjustments, bells and whistles. ‘200 test persons have adjusted the support in the lower back region again and again until they felt comfortable. The sensors provided the scientists with data which they evaluated using pressure mapping technology. The procedure was repeated several times and the results were clearly confirmed.’ All probably excellent but totally irrelevant for full biomechanical requirements. See ☛ Comfort?→
To some extent this has been addressed by incorporating a pelvic support system. This fails as it is adjustable and does not have the comfortable V-shaped iliac support of the original Gorman ‘Pelvic Posture’ concept.
Questionably it also incorporates lumbar support. If adjusted to produce effective lumbar lordosis this would counteract the important pelvic support. Adjustment to reduce this effect is counter intuitive. In my experience adjustments are usually made in the wrong direction. People have preconceived ideas as to what ‘should’ be correct and can be misleading in efforts to determine what best addresses the bio-mechanical imperatives.
Adjustment of the seat surface up to 7 cm to the front and back is irrelevant. Only the ischial tuberosity must be supported. Limitation of the backrest’s opening angle to six steps is also irrelevant. Ideally this should adapt to the full reclined mode and intermediate steps avoided.
When shifting the weight to the front, the seat surface follows with a slight inclination downwards. This is good. If this was the only mode, then many of the other supports and adjustments would become irrelevant….
Memory foam seat. Excellent. A strong + point when tilted forward.
Only really suitable for short term sitting.

The Albion range

Screen Shot 2018-12-06 at 11.41.44 There is a wide range of reasonably ergonomic office chairs. Their Spynamic range claim extra ergonomic advantages. The chair shown on the left has a somewhat over long seat-pad but is is bettered in the example on the right. It looks as if there may be messy unneccesary adjustment controls. http://albionchairs.com/office-chairs-by-application.htm

Ferrari gets into seating

Peter Bessey sent me this ref. with the comment “Guess they missed an opportunity to work with your specs, Henry. Would have been interesting to see them come up with a properly engineered solution, alongside the carbon fibre composites. All the best, Peter”

Yes. Only really suitable for short term sitting. HAS

<http://www.solidsmack.com/design/ferrari-unveils-two-sports-car-inspired-desk-chairs-milan-design-week/>

The Modern Zure Office Chair

“Boldly going where no chair has gone before. The Zure takes you to a new comfort destination. Our unique range of this distinctive, uber stylish posture perfect seating solution has it all. There is fine mesh, fully upholstered, partly upholstered and stunning flexible elastomer options. The seat and backrest are carefully contoured to provide maximum comfort. The high-quality outer skeleton wraps the user in touch point technology. Padded armrests on the fabric and leather options provide pleasing eye-appeal whilst the elastomer versions have colour coded armrests.” “Orthopaedic designed frame”. Having bought the hype and the chair for $736, the user would be well advised to study BACKACHE? For users and patients (only) if prolonged use is intended. Only really suitable for short term sitting.

A selection from ‘Posturite’.

A good selection but only really suitable for short term sitting.

Dynamic seating & motion

The basic model in this category is the ‘Wobbly Ball’. A good idea but who wants to sit on this in an office? So let’s call it a ‘Balance’ chair.

The SwingSeat from SmartMotion Technology

Basically an upright chair. With the seat forward tilted, lumbar lordosis is ensured. It’s self adjusting controls allow a range from about 40° of reclination from the upright to a 10° of forward tilt which is performed effortlessly, avoiding the usual confusing plethora of adjustment controls. Manual controls are present for backrest height, angle, depth, resistance and seat height and armrest control. The concept behind this design is to enable constant small amplitude spinal movement which helps ensure the pressure gradients required for adequate nutrition of the disc. The ergonomic evidence for the importance of enabling movement which is comforting and ensures health of the disc constituents is summarised by Rani Leuder in Ergonomics Review of The Swing Seat See Lueder R. Anatomical, physiological and health Considerations relevant to the SwingSeat. 2002; Ergonomics Review. She is President of Humanics ErgoSystems, ☛ www.humanics-es.com→

The PESKA chair
This ‘dynamic’ chair has the option to fix the balance mechanism. It recommends sitting on a balance chair only for a limited time, say 3 times a day for 30 minutes. Sitting on office chairs with active balance mechanism throughout the day would be the same as if you exercised continuously for 8 hours. The same effect occurs with the unstable intermediate mode in the 2T concept, but with stable positions at the end of ranges there is no need for adjustment.

The KOEHL AIR-SEAT, from Holland.

“Stimulates multidimensional micro-movements and trains by frequent changes the low-lying back muscles. Balancing on the KOEHL AIR-SEAT by gentle lateral pelvic movements, by a pair of air cushions. Emphasises the rehabilitation function. Comforting and aids IV disc nutrition which helps avoid early disc degeneration. http://www.koehl.com/fileadmin/user_upload/Dokumente/AIR_SEAT/koehl_Brosch_AIR-SEAT_29092014_EN.pdf

WAGNER chair

The Dondola hinge system allows a controlled all-round instability and a trial when incorporated in a Wagner chair showed reduction of morbidity when compared to office chairs without the system. A full account is given in ☛ EXERCISE & movement→

BackStrong Chair

An awful example of OTT hype tells us that “this chair is’ the best in the world’ and ‘This means disrupting the seating industry -‘. It was helped designed by ‘Dennis Colonello (D.C.), the top Chiropractor on Earth:. See this at → BackStrong Chair

It appears to be an upright chair, needing a desk for work, This is likely to prove retrograd, even Dickensian (See Bessey in OFFICE WORK-STATIONS), in a few years when deskless chairs, as part of a sit/stand workstations, come on line. As an upright chair it remains only a partial solution to the bio-mechanic ill effects of proloned sitting. It’s remedial points are :-

dynamic seating. Called here ‘ Sit-In-Motion’.
A forward tilted seat (The FORWARD TILTED SEAT (FTS). )
This is helped by an independant moving seat pan.This reminds me of my 2013 Cambridge student model (See OFFICE WORK-STATIONS ) which is actually a full work station incorporating the 2T concept.
- This seat has the components to progress it to bio-mechanic (ergonomic) fully remediated office chairs for prolonged work.
- I would urge the manufacturers to take advantage of this option which would result in a truly disruptive system that would sweep the chair industry. Who wants to use a work-chair that is not ergonomically optimised?
Worrying is that the back support appears to extend above the pelvic brim. In the verbal blurb it is described as ‘lower thoracic’ which would be bio-mechanically adverse (See BACKRESTS. Pelvic support v. Lumbar.).. Perhaps it would be as well if ‘the top Chiropractor on Earth’ had a word with John Gorman who is also a chiropractor with the advantage of a prior top engineering degree from Cambridge University. Chiropractors are deeply suspicious, perhaps with reason, of us physicians. I was trained by James Cyriax the ‘Father of Orthopaedic Medicine’ who wrote a book fiercely attacking Osteopaths and Chiropractors. However Gorman overcame his suspicians as I discovered that he knew his spinal anatomy and bio-mechanics and we were speaking the same language.
Yet another “radically new” development which isn’t new except to those who came into the business recently (ie less than 30 years ago)”. Unattributed, but guess who?
In the present form it should probably not be used for longer than 6 hours.

‘ChairSix’ by Si Freeman

The design is sophisticated and simple – good. The backrest is adjustable and can be adjusted to the adverse ‘lumbar’ position. – Bad. Height location is critical. ☛ BACKRESTS. Pelvic support v. Lumbar. The width of the back rest could be a problem for work-related activities. If at a desk or table, its width impedes the elbow for keyboard and mouse activities. This issue was well-proven many years ago, by the design of chairs stretching back to Fred Scott’s Hille Supporto chair, where the narrowed spinal backrest was a deliberate feature and seems particularly popular in Scandinavian furniture designs still. The seat(s) seem to be forward tilting – good. The somewhat flexible, rubber foam pads which sit proud of the pan, on raised platforms, act as small pivots that adjust the pads to the body form and seemed to work well and gave a sense of flexibility and comfort to the seat pan. – good. The 6 knobbles on the back-rest,may represent some type of ‘massage’ feature, as seen on some Asian add-in seat pads for vehicles and office seating and that the slight wobble from the pivoting pads, also provides the movement needed to move the back against them. They are not in the mid-line – good.

It seems to me that ‘Pelvic Support’ and a FTS are not complementary but ‘either or’. The ISCHIAL OFF LOAD system gets round this with a convex seat-pan providing a FTS in front and slope towards pelvic support at the back. In spite of these improvemrnts this remains an upright chair with their considerable ergonomic disadvantage. Only OK for shortish sits as in a sit/stand office. ☛ Sit Stand & stools

Cobhamly High Back Mesh Office Chair

I have not seen this chair. It seems to have ‘pelvic support’, although possibly above the 20cm allowed height. The price seems OK. Their Boston High Back Executive leather effect operator chair. Features a heavy duty gas seat height adjustment and fully synchronised tilt to seat and back rest with adjustable tension control. I do not know how this works out, But could probably be adjusted to comply with the 2T concept with optimised comfort. It has features that suggest that the designer may have seen this blog.

AN EXISTENTIAL THREAT – A new breed of office chairs with a reclined work mode.

WORKCHAIRS, a new breed with a reclined mode.→

As predicted this is begining to emerge. A number of ‘workstation’ type office chairs are appearing which include a reclined work mode and so are superior to the present (2016) upright conventional upright models. Appearing to ignore the science and based on engineering they do not invite a great uptake inspite of extensive PR.

Altmark Now, in 2015, an office chairs is proposed, the Altwork that has at least an upright and reclined work position as I had been advocating since 1998. However, it fails the functionality of the 2t optimisation. These faults could easily be corrected and so with reservations, it is potentially the best work-chair in the market. See a more detailed account in WORKCHAIRS, a new breed with a reclined mode.→ . . also (http://altwork.com).

The Cambridge trials showed the elegance, simplicity, cost effectiveness and greatly enhanced ergonomics of the 2T concept. This provides an opportunity for the existing manufacturers and any entering the field. Top manufacturers are already recognising that they have come to the end of the line for ergonomics. Backache (LBP) and other spinal & muscle-skeletal conditions still persist resulting in stress and lowered productivity.

BACKACHE? For users and patients (only)

OK. So you use a chair and are liable to backache. All this is very confusing and so what do you do? I am no longer in the business of giving advice to patients and organisations. However my interest in optimising chair design might allow me to offer some tips for users and patients (only).

Possible remediation.

If you have an expensive, top range chair or a cheap one, examine the section on how some of these relate to the 2T concept. A good chair can be modified to approach the advantages of the 2T CONCEPT (see 2T CONCEPT a full solution →’). This may help you modify your own chair.

Disable the adjustment that allows the pelvic support to be above 20 cm above the seat (?Chewing gum) (see ‘Lumbar, pelvic/iliac support’)
Arrange for the adjustment control to allow easy back & forward movement. Make the chair a 2T system – either reclined or forward but not intermediate. (Unstable intermediate mode→).
- Intermediate ranges should be unstable. They can be used as a rocking chair or as therapeutic exercise following an acute episode of backache/lumbago.
In the upright mode the seat can be either tilted forward (see ‘The forward tilted seat), or arranged to take advantage of the pelvic support providing this is correctly modelled or a combination of both.
Apart from chair height and head/foot-rest, adjustments should be set accordingly and then ignored or fixed.
If you are buying, a back shop can show a number of models and advise but be aware that they are trying to sell you something and tend to feed you the manufacturers hype.

If your chair is really basic you may need some widgets. Possibilities are

A wedged cushion on the seat which helps approximate to a ‘Forward Tilted Seat’ (FTS). See .Why? Mandal’s Homo sedens. The concept has been fully confirmed by research using pMRI scans. See short account below.
- One I assessed, from America ªSITTS Posture Cushions.) and wrote ” The seat pan is parallel to the floor (checked) but with some contouring that might add 2° . The hip angle is shown to be 132° which is close to the optimum angle (130°) determined by pMRI studies to avoid adverse movement of the Intervertebral disc contents (Smith FW et al. The Response of the Nucleus Pulposus of the Lumbar Intervertebral Discs to Functionally Loaded Positions. 2007;SPINE Volume 32, Number 14, pp 1508 –1512). See → Positional MRI
- The above confirms the views of AC Mandal which he advocated in his book (Mandal. AC., The Seated Man (Homo sedens). 1985. Dafnia Publications,) are confirmed. He advocated a seat that was tilted forward and down by 20-30° from the horizontal, allowing the hips to extend to 120-130˚ and the pelvis to tilt forward with the lower spinal joints adopting the correct, safe, lordotic posture.
- With the seat tilted forward, note that the user is not constrained by a backrest and is free to move, the lumbar lordosis is maintained by the pelvis being tilted forward. The versions with a steeper angle may have a problem with slippage. Now in 2018 since writing the above on an early version, new improved ones have been developed by SITTS. They look good and can be seen at https://www.kickstarter.com/projects/sittsperfect/sitts-cushions-a-natural-way-to-perfect-posture?ref=nav_search&result=project&term=sitts Or→ (http://www.sittsperfect.com)

A backrest cushion that gives iliac support. Have a good look at the section here on iliac support that must not be higher than 20 cm above the seat and approximates as near as possible to the original Gorman model.
- My patients loved the ‘PostureRight’ cushion which was designed by my old St Thomas’ colleague, Dr Bernard Watkins.
- Various lumbar ‘Rolls’ are OK if correctly placed.
- I have a cheap (£1) and cheerful wire & net model which works moderately well.

Remember the importance of exercise & movement. Good Luck!

There is plenty of well intentioned advice on backache to be found on the web. But please read this first (Sorry, hard work, I know) so that you can distinguish the rarely well informed from misinformation and hype, some that is frankly laughable. Just have a look at Google→.

The Hermann Miller account from being almost laughable is now good, probably as a result of being advised by Andersson, the Swedish scientist. I find the latest (2015) account too diffuse to be easily comprehensible and illustrates some retro models.

JD Gorman’s holistic/ chiropractic account can be seen at ‘Natural Joint mobility’.

Some is linked in Backache and GENERAL USERS→

WHY? Mandal’s Homo sedens.

Screen Shot 2013-10-13 at 17.16.44 AC Mandal was a leading Danish surgeon who wrote the ‘The Seated Man’¹¹⁹. Becoming disillusioned in the conventional wisdom of the principles of correct chair design, he transferred his scientific and critical training to that of the biomechanics of sitting. ☞ Mandal

He observed that young children naturally sit with the chair tilted forwards onto the front legs. They then support their elbows on the table, which for a small child is the right height, and the protective lumbar lordosis is effortlessly and correctly maintained. As the child grows the height of the table becomes relatively lowered and the child then sits in the usual semi slumped position. This results in short episodes of backache, which are ignored, and possibly to permanent stretching of the posterior spinal elements which can predispose to instability and a lifetime of adult spinal pathology.

Drawing on the work of Keegan¹²⁰ in the USA, Schorbath¹²¹ in Germany and Akerblom¹²² in Sweden he concluded that children are instinctively right to modify their seats to tilt forward with a slope of 10 to 20°. This allows the hip angle to open from 90° to 120° and the pelvis to rotate forwards, on it’s fulcrum at the ischial tuberosities, so that the lowest two lumbar joints are in the extended (safe, lordotic) position, ensuring the correct lordotic posture. No back rest was necessary and the torso was free to move. His proposed solution was a combination of height adjustable desking and forward tilted seat similar to the equestrian seat.

The recommended ‘correct’ position was fundamentally wrong.

Mandal He suggests that this posture was developed by taking a standing skeleton and sitting it on a chair.

A skeleton has advantages over a live human.
It can sit motionless all day.
It has no constraining muscles ligaments or IV Discs.
It is steaded with an iron bar down the vertebral canal.

(The 4 (+2) main adverse effects apply :-

There is a x2.5 increase in spinal loading over full reclination on the discs and 40% over that of standing upright (Nachemson, Sato but not Wilke).
The pelvis tends to tilt backwards reducing the important and protective wedge (lordotic) angle at the lower 2 lumbar joints.
The position may be prolonged in an office or work environment.
Lumbar (not pelvic) support accentuates this effect.
And the hip flexion also tilts the pelvis backwards.
the vulnerable lower lumbar joints are forced into a flexed position so that the protective high wedge angle is reduced to a point that the disc contents are liable to move backwards and protrude.
See BIOMECHANICS that determine safe sitting

Screen Shot 2018-12-20 at 14.46.36 He wondered how such a poor position could have been accepted as correct.

A chapter in his book is titled ‘Functionalism’s instruments of torture’ and he dates the decline to the 1930 Exhibition in Stockholm which had the slogan “Beauty in everyday furniture”. Later he met the authority who created this concept who admitted that the image of the back of a standing person was simply cut and pasted to a drawing of a sitting person (personal communication). It has no scientific basis. This basic false premise is still regarded as ‘correct’, regardless of more recent scientific knowledge of spinal pathology and bio-mechanics and is still universally advised with an air of authority. Mandal claimed that 90% of lower back pain was related to loss of this lumbar lordosis.
With the increasing liability to backache, an ergonomically ‘correct’ chair was sought.
Wrongly! ☛The upright seated posture.→

Screen Shot 2016-01-14 at 18.19.39 Google→ shows an amazing collection of diagrams and pictures of ‘correct’ seating with a few that are actually correct. For a similar account see bodyzone shops→

This mistaken view of correct seating is still accepted and widely promulgated by authorities who advise on such matters. Some detailed examples :-

Another diagram for correct seating actually spells out the arguably adverse ergonomic recommendations! (outlined in red)

The lady is sitting bolt upright, to attention, like a guardsman. The body position shown is cramped and movement, which is necessary for comfort and disc nutrition, is hardly possible.

There is no armrest. Some authorities maintain that this allows greater movement of the upper torso. However support under the elbows prevents dropping of the shoulder girdle which can be tiring and uncomfortable. Support at the wrists helps to prevent RSI.

The diagram shows the neck in the correct neutral position. Unsupported cervical flexion results in much greater axial compression. (This is equivalent to looking downwards when standing, see Hansraj KK. 2014)

A greater viewing distance allows the intrinsic eye muscles to relax. The rule should be to be as far from the screen as vision allows comfortably. If necessary get glasses, tinted against glare, adjusted to 36 inches.

Screen Shot 2018-06-11 at 21.04.14 This diagram might be acceptable, a semi-partial remediation, if the point was made that it incorporated the alternative ‘Pelvic (iliac) support’ instead of ‘lumbar support’ as is shown. This alternative solution of applying the support directly to the pelvic (iliac) crest, ensures that it was unable to rotate backwards. This support should be a particular shape and size to spread the pressure loading. (See later under ☛ Pelvic & Lumbar support→).

There are now many well engineered and comfortable office chairs in the market. Most have a fundamental bio-mechanical fault. They rely on the mid- upright mode of sitting for prolonged work. As has been shown this combines the two most adverse effects although the backward pelvic tilt can be modified by a FTS or lumbar support. My own opinion on a number of top range chairs, as shown, is of admiration of the design and engineering mixed with awareness that the most essential bio-mechanical points have yet to be fully appreciated. The following are better than most as efforts have been made to incorporate pelvic support (with reservations).

Ergonomics-standard-diagram The latest version of BS EN 527-1: 2011,(the European standard specified dimensions for office desks and tables.) state that fixed height desks should be 740mm ± 20 mm and desks should adjust between 650mm and 850mm for sitting modes and between 650mm and 1250mm for sit/stand desks.

The suggestion of a FTS would have been helpful.

Next, see ☛ Various chairs. How do they measure up?→

REMEDIATION of the Upright Seated mode.

Already described are the adverse effects of mid-upright sitting →

Derived from these findings are the ergonomic requirements to help remediate the adverse effect of the Upright seated mode. Essentially there are two.

Derived from these findings are the ergonomic requirements to help remediate the adverse effect of the Upright seated mode. Essentially these are two.

☛forward tilted seat→,
☛Pelvic support→,
The Ischial off-load system. A third, now often used for Upright seated mode remediation in a number of chairs is derived from a combination of the 2 above. The seat-pan is convex so that the front half acts as a forward tilted seat and the back half allows the user to sink back into the back support. Hopefully this is correct iliac support.

These remediations, aimed to give improved ergonomics for any chair should be examined carefully as they are commonly misapplied due to failure to understand the underlying scientific basis. Some insight can be gleaned from ☛Various chairs. How do they measure up?→

The above diagram (but not my comments) was derived from https://www.chairoffice.co.uk/blog/the-ergonomics-of-a-chair-explained/ with the following advice …

A seat height that ranges from 16 to 21 inches off the floor should work for most people.
A proper seat depth should leave between 2 and 4 inches between the edge of the seat and the back of your knees. If the seat is too far forward, it may put undue pressure at the back of the knees.
Seat tilt. Good ergonomic chairs will allow the seat to tilt, which allows for correct positioning of the pelvis. Anterior pelvic tilt is a posture problem that affects almost everyone who sits a lot, which is why it’s important to keep the pelvis in a neutral position when sitting, with 80 degree angles at the hips, knees and ankles. (Anterior pelvic tilt is used in the anatomical sense. In the popular use is a Backward tilt.)
Backrest Lumbar support. This refers to the support given to your lower back, and is an essential feature of an ergonomic chair. Ergonomic chairs support the natural ‘S’ shape of the spine, which prevents slumping and reduces stress on the spine and the pelvis. An adjustable backrest allows users to align the curve in the chair with the curve in their spine, for optimal support. (Misleading as no distinction is made beweem Lumbar (Bad) and pelvic (Good).
Backrest recline An adjustable backrest allows for greater tailored positioning for the user, as they can move the backrest to more specifically support their natural spine position. Using this feature throughout the day allows the backrest to take some of the weight from your upper body, reducing the pressure on your spinal disks and muscles. (2T Requirement 6. Variability at head and feet only. These are the most variable parts of the human body, in the reclined mode. Adjustments avoided elsewhere. ☛Adjustments→. )
The swivel in an ergonomic chair helps users with their manoeuvrability, making it easier to reach different points of their desks without having to strain excessively. (and to escape from the chair).
Armrests help to reduce tension in the upper body and allow the shoulders to relax. However, armrests should not be used when typing as this reduces overall arm movement, which in turn increases wrist movement leading to strain on the forearm muscles. (Contradictory. Do we or don’t we use armrests? One that tilts back out of the way is an answer.)
Headrests supports the back of the head and the upper neck, reducing tension in the shoulders and upper torso. ( Of use for contemplating the ceiling in an upright work mode. Important for the 2T reclined mode, Requirement 4. A correctly placed head/neck-rest is required so that the occupant has no need to move the neck to establish the task-related visual field.)
The material should not cause the user’s back to sweat. However, the materials used will depend on the budget; high-end ergonomic chairs will use leather or velvet.

This not unreasonable account shows that remediations of the upright seated mode has come to the end of the road. They are not a solution to fully reduce the incidence of backache (LBP). This would require a new technical fix that addresses all identified adverse bio-mechanics effects of prolonged upright sitting. Next ☛ A FULL SOLUTION→

Helpful pages include

Familiarity bias
Art, Elegance and Objects of Desire
EASY CHAIRS
And an associated concept ☛SIT/STAND (& stools) →.

The effects that all need to be avoided for an ergonomic solution to spinal dysfunction.

How other people sit

Better! But not for office work.

Japan.

The Japanese kneeling posture, like most things Japanese, is highly sophisticated. It is elegant particularly when a Kimono is worn and for women the firm Obi also provides support. The body weight rests on the heels of the extended feet so that the hips are extended at a slightly greater than a right angle. This allows the pelvis to rotate forwards, as with a forward tilted seat, resulting in a lordosis at the lower lumbar joints. The torso can remain comfortably upright as in the modern, forward tilted Scandinavian Balans chair.

The Japanese, like most people of the Far East, have hyper-mobile joints but the more hypo-mobile Europeans find this position uncomfortable to maintain as it requires extreme forced flexion of the knees and extension of the ankles. Frequent and prolonged use of this position results in callus formation on the dorsum of the feet.

When I asked this Icelandic girl to sit to have her neck examined, she adopted the Japanese sitting posture on a chair. When asked “Why?” she answered “Because this is the way that I have been taught by my Physiotherapist.” Note that her hips are extended to a near FTS extent.

The traditional Japanese sitting posture was shown in a study (Schlemper 1983) to cause less back problems than sitting in a chair but increased as upright Western seating was introduced.

Various sitting and standing postures were measured for degree of lordosis and electrical muscle activate (Dolan, Adams 1988). The results confirmed that of the sitting postures, the Japanese involved the least flexion but the most muscle activity to maintain, whereas slumped sitting on the floor involved much greater lumbar flexion but very little more muscle activity than standing.

The slumped and squatting positions are used by most non-Western peoples and who tend to have a low incidence of LBP (Fahrni 1965, Jonck 1961) , the wedge shape of the vulnerable lower two lumbar joints (L4/5 & L5/S1) is preserved although there is flexion throughout the lumbar spine (Bruggeman 2000). Intra-abdominal pressure maintained by the abdominal and spinal muscles acting through their flat tendons and fascia and the upper body weight is brought forward to lie over or in front of the abdominal cavity which can be regarded as a balloon or football, This has a pressure relieving effect on the spine and transmits a proportion of the upper body-weight directly to the pelvis. Gorman has also pointed out, this position exerts traction on the lower two lumbar joints, so that although the joints are flexed the compressive force has been reduced.

To review the bio-mechanic problems that occur with sitting and their ☛Remediation⟶

About Dr. Henry Sanford

next see ☛BIOMECHANICS→

The future lies with desk-less stations described under the 4M version and in the Sit/Stand environment. The 2T concept is particularly relevant to this. See The 4M office deskless workstation→

The 2T chair cantilevered from a ‘Delta’ desk. A solution.

Office space.

The ‘pod’ design concept.

Office ENVIRONMENT

The 2T chair cantilevered from a ‘Delta’ desk. A solution.

School chairs

Comment

Next ☛ A FULL SOLUTION→

The Hermann Miller Aeron

Pledge BT3 20/20 (Task)

The Howarth Zody

The Albion range

Ferrari gets into seating

The Modern Zure Office Chair

A selection from ‘Posturite’.

Dynamic seating & motion

The SwingSeat from SmartMotion Technology

WAGNER chair

BackStrong Chair

‘ChairSix’ by Si Freeman

Cobhamly High Back Mesh Office Chair

OK. So you use a chair and are liable to backache. All this is very confusing and so what do you do? I am no longer in the business of giving advice to patients and organisations. However my interest in optimising chair design might allow me to offer some tips for users and patients (only).

Possible remediation.

Next, see ☛ Various chairs. How do they measure up?→

Already described are the adverse effects of mid-upright sitting →

Japan.

Next, some side issues, ☛ Why? Mandal explains⟶