Category Archives: SOME CHAIRS.

An account of some chairs in relation to their 2T attributes.

VR and sitting

Global blue chip companies are throwing their weight into VR development (hardware and software),  Mark Zuckerberg believes “this kind of immersive, augmented reality will become a part of daily life for billions of people”.

Roto VR chair

Andrew Lockley (→ https://www.exponentialinvestor.com/author/andrew-lockley/   ) discussed this (3/o3/2017) with Eliott Myers from Roto VR, which is a small, innovative firm with designs on the related accessories market.  He claims that “Roto enhances the seated experience with haptic feedback so dramatically you feel like you’re really there, in another world. Once you’ve tried Roto, VR feels empty without it.  With Roto, you can add our Table accessory, so you can drive around 360 degrees with a steering wheel (and pedals). Roto also has “rumble shakers” which can be affixed to the underside and back of the chair for added sensations. It’s like 4D on steroids. Actually we should call it 360D!”

Sounds exciting!

But not if the chair is liable to induce backache (LBP) on prolonged use. Their picture ( http://www.rotovr.com  ) shows an upright chair with their concomitant disadvantages and with it’s extra, probably excellent, VR additions.

A huge opportunity

VR and sitting, if prolonged, will be relevant to chair design. It would not be difficult to redesign this chair to take advantages of the 2T or 4M concepts and so correct it’s seemingly obvious, from the pictures,  ergonomic deficiencies  This would have the additional advantage that the firm would have the basis for an ergonomic optimised office work chair that would jump ahead of the field.

If you are in the mood have a look at ☛ →

Comment

Screen Shot 2017-03-07 at 17.59.30From Gorman JD. MA (Cantab.) (Mechanical Sciences) MI.Mech.E (Member of Institution of Mechanical Engineers). MMCA (Member of the McTimoney Chiropractic Association) on 7/March 2017.

Yes I agree that a typical office chair and the typical office chair slump is wrong. Certainly semi reclined  position is one solution. I have rather given up trying to predict how the sitting world (the world of Homo Sedens) will evolve. It is certainly slow in recognising the problem which would be the first step.   This chair looks to me like a cheap after-market car seat. The computer people probably have no interest in the chair/seat so gave it no thought so long as it looked fairly high tech.     john g.

Screen Shot 2017-03-07 at 17.59.30Reply from Dr HA Sanford MA MB BChir (Cantab) D Phys Med (Lond).

You are probably right.   Then, I am not an expert on car seating like yourself.   Henry

Screen Shot 2017-03-07 at 17.59.30Comment from Dr HA Sanford

Virtual Reality (VR) is taking me back to ‘The Brave New World’ of Aldous Huxley (1932) which I read at school.   He described a dystopic utopian hierarchical society that kept control with consumerism, drugs (Soma) and VR (Feelies).  Work was done by robots and everyone was free to relax and enjoy promiscuous sex. Sounds similar to what may happen now.

This work was superceded by ‘1984′ by George Orwell, who was at my Prep school some 20 years before me, and hated it.  We all did but did not go into print so viciously.  ’1984’ faced the more immediate threat of Marxism which has now intellectually collapsed due to it’s internal contradictions and misunderstanding of the human condition.   So we are now back with ‘Brave New World’.   It does not sound too bad but actually is a form of slavery.  Those who objected, wanting to think, were regarded as barbarians and exiled.    To Iceland (as far as I can remember).  I used to run an annual course there (See the photographs in HOW WE SIT NOW→.)  The people are wonderful and it is very pleasant (in summer).

So, VR, here we come!    HAS

Art, Elegance and Objects of Desire

Aesthetics are hardly the subject matter of bio-mechanics and is left to the individual designer and Altmarkthe company image.   However there is relevance to chair design and furniture seen as art.   My apologies for this effusion which was occasioned by seeing,  in 2015, a new chair proposed by Altwork (http://altwork.com). that has at least an upright Screen Shot 2015-11-06 at 18.21.33and reclined work position as I first proposed back in 1998.  It also has a ‘stand’ facility so in this respect is approaching the 2T derivative, the 4M OFFICE WORK-STATION. I have not seen this chair and so cannot assess the extent to which it is 2T compliant.    From the photographs there seem to be problems.  It looks over engineered, awkward  and clunky.   See the Cambridge student model which does the same thing and is simpler and cheap

2T Deskless office chair SS prototypeThe model shown was an upgrade of my P1 prototype.   It was of this that a CEO said “This is too comfortable.   My work-force will go to sleep” although he was lying on wood Screen Shot 2016-06-06 at 17.45.21with no upholstery’  (Early 2Tilt chair CONCEPT and criticism→).     It looks surprisingly similar to the Kragel’s Nap Chair which i.e. regarded as an art object and was shown by Jessi Reeves  in her first solo exhibition at the Bridget Donahue Gallery. nvc. in 2015.

Having been married to a highly innovative abstract artist,  http://www.vancaillieartist.co.uk→  I have views!   Back in the 1960’s some regarded me as one of the few in England who could asses the aesthetics of the avant garde at that time.  Abstract Expressionism. Matter Painting,Tubism (Mathieu), Tachism, Pop etc.   Alas! Now I am totally dated!  But reactions do not fade.  True art has an effect that distinguishes it and is always itself true.   “Truth is beauty.  Beauty is truth” said Keats.

The untruthfull in art such as propaganda was demanded of artists in Nazi Germany and Soviet Russia and their derivatives such as ‘Social Realism’.    A reasonably good English artist, Richard Hamilton, was persuaded by his ‘Ban the Bomb’ CND wife to depict Hugh Gaitskill as a Hitleresque monster.  Obviously untrue.  To my mind, it destroyed  his artistic integrity.  Artists, although maybe dissatisfied with a work, never produce a bad picture, even with scribbles on a napkin.  I have a Calder drawn around a wine stains on a catalogue of his work.  We can be moved by nostalgia.  This is something else.   Alfred Munnings was anti modern art but his portraits of beautiful women, beautifully turned out and mounted on beautiful horses are nostalgic of an age recently past.

True art can evoke excitement and a ‘prickling’ & tingling physiological effect now known as Autonomous Sensory Meridian Response (ASMR) in the presence of certain work.  This can occur with sophisticated connoisseurs, and equally the naive.     Robert Graves in his ‘White Goddess’ (1948 – The White Goddess : a Historical Grammar of Poetic Myth -London: Faber & Faber) describes this effect and attributed it to the true  measure of a poet to faithfulness in depicting the White Goddess, of ancient tradition who was worshipped under many titles and forms, whether nymph, mother or crone, of the early matriarchal societies, thus proving the truth and source of his or her mystical inspiration.   Matriarchy, to be overthrown by invading patriarchal Indo-europeans, may have never existed but these emotional and physiological effects can be observed in poetic, musical and visual art forms.  “All true art is sacred” replied my wife (vancaillieartist.)  when asked why one of her works , an abstract relief, could be regarded as religious, and was requested for the exhibition of sacred art at the Musée d’Art Modeme, Paris, “Art Sacrée”, 1965.

Screen Shot 2015-09-29 at 18.53.20For me, the most interesting exhibit at Olympia, 100% Design exhibition, 2015, was this incredibly engineered and simple construct by Danial Chow  →.  Of solid walnut “Brackets or bracings that conventionally structure the architecture are substituted by hidden beaming inserts, invisible from outside”. He also wrote to me “Thanks for all the input you inspired me.  I will begin paying attention such a new measure – pelvic support or pelvic stimulator in my future designs.  I speculate that the said may also help stimulate the central nerve of the user while sitting.   It could then be the “real” solution and a new era also revolutionary to long time siting/working.     I may consider adopting this to working chairs and lounge chairs.”       I do not know about “stimulate the central nerve of the user”.  Sounds exciting!    He later wrote  “I did more thinking.  I realised it is possible to incorporate pelvic supports at the two sides of the lower-back-rest.  Perhaps I can design and make a new lower-back-rest to test the effect.  By the way, did I explain about how I came up with the configuration – dimensions and angles?   I did a mockup with a range of different configurations.  I picked the set which comforts the user most.”

Danial Chow, not an expert on biomechanics, has certainly ‘got an eye’.  As does any true artist.   I hope I have not misled him on iliac support.  Designed for upright sitting  it is less important for a reclined mode.  It would still help somewhat and some contouring would look good.  (see,BACKRESTS. Pelvic support→)

Screen Shot 2018-06-09 at 12.04.05Similar, also aesthetically pleasing, in 2018, is a work in carbon fibre by ‘Essence of Strength’ .   It does not have any ‘Pelvic support’ .  Pads are supplied to correct this deficiency which should have been unnecessary with better design.   <https://www.essenceofstrength.co.uk/>.    Although not intended as a work chair, the ideal ergonomic shape should approximate to that of the 2T (3M) reclined mode.    The 2Tilt RECLINED MODE for fully safe sitting.

This may be relevant to Furniture as Art (FaA) where so much are just amusing nonsense which some may find desirable.  To be ‘true’ and excite ‘desire’ for the object it must have relevance to the human body that is going to use it.   This means bio-mechanics.   Preferably an understanding is the Wolfsonbest but  may also be achieved on a sub-concious level by an artist.   “It’s all in the eye” said my wife, explaining composition and the golden section.

Wolfson seems to me to be have serious intent and to be the classic in this genre.  Of course he does not read work on bio-mechanics and so was unaware that desks in offices are becoming to look Dickensian (4M OFFICE WORK-STATION)  But desks which are objects of desire will still be Wolfson deskused in private offices.

Screen Shot 2016-06-14 at 19.31.45

The observer or user decides whether the object is pleasurable, relevant and desirable.  The designer takes this into account. an ‘eye’ is a help even if the ergonomics are correct.

Without a nod towards biomechanics, some schools may be seen – dada, surrealism.

Screen Shot 2016-06-21 at 14.27.46 Screen Shot 2016-06-21 at 14.29.14 Screen Shot 2016-06-21 at 14.33.04 Screen Shot 2016-06-21 at 14.34.37 Screen Shot 2016-06-21 at 14.35.44

Recliners

Recliners are not intended for office use.  However, using a reclined mode and a tilting mechanism, they have certain similarities to a 2Tilt chair.  The boundaries between contract and home furniture  are decreasing and the division may be disappearing entirely. 

See http://www.onofficemagazine

Recliner chairs are only suitable for home use.   The full stringent requirements for prolonged sitting are not necessary.  The tilting mechanism is not required to be unstable and can stop in mid range without an adjustment.  Until an efficient system for this appears on the market even an electric mechanism is used which is surely the last refuge of inadequate design!

A  chair using the 2T (or 3M) concept, which has bio-mechanic optimisation, is different only because it can be used as a work chair.   Will people buy recliners when a cheaper and better designed dual purpose chair comes on the market?  This may also be particularly relevant to the growing ‘gamer’ market.

BERG Unik recliner

Not designed as an office or work chair, nevertheless has features similar to the 2T concept.  It is helpful to note the differences.

Screen Shot 2014-08-29 at 15.58.38

  • The mid ranges between full reclined and upright do not have the instability that is basic to the 2T concept.  This  adjustment, although potentially adverse, is mentioned as a selling point.
  • Adopting the fully reclined position is a slight struggle. This may be due to a failure to understand the adjustments and a reason to scrap them..
  • In the fully upright position, equivalent to the upright mode, the seat is parallel to the floor mitigated by a degree of pelvic support.  This is allowed by the 2T concept although the FTS is preferred.
  • There is unnecessary, even adverse, adjustment of the height of the pelvic support.   For the 2T this is the ‘Iliac’ version and fixed at 20 cms.
  • The leg rest extension works well.  That it only supports and compresses the calf is worrying.  The 2T requires a foot-rest which is adjustable to the users leg length.   This and the head-rest are the only 2 components that require adjustment.  The torso should be fully supported by correct design.
  • Upholstery is usual with recliners but allows build up of heat and moisture.  Arguably it adds comfort and conceals design mistakes but also can reduce correctly designed support.
  • Have a look  at Berg→

Jessie Reaves (b. 1986)
Screen Shot 2016-06-06 at 17.45.21“The symbiosis of art and design culminates in Jessie Reave’s work which hovers between furniture and art object. Reaves’ creates conventional (and functioning) items you would find in any furniture shop: chairs, a couch, lamps, several shelving units. However, the artist assembles materials unconventionally to create an entirely unique aesthetic.; what is normally kept hidden inside furniture is turned out.”     Reaves recently had a solo show at New York’s Bridget Donahue gallery.  

This looks very like my P1 2T prototype of 1998.  The back support looks excessive and is adverse lumbar rather than a pelvilc support.  It looks adjustable which might account for this.  Shown as an art object it shows the basic simplicity of the 2T concept.

METRONAPS

Another interesting product.   Again, this is not a work chair and looks like a recliner.  It is intended for short naps in an office environment to which a user can retire if desired.  It now recognised to have benefits ☛sleep→ at 2T, early concept.

  • metronap009It costs $1300.
  • Reclined seems to be the only mode and this precludes it from being a 3M chair or 4M workstation.
  • The hood allows it to become a semi Pod.  It is of interest as it could be incorporated into a 2T chair and contain the monitor etc.
  • It should be noted that a 2T, whether 3M or 4M, can easily be slept in.    Indeed this was an early criticism by a CEO “This is much too comfortable.  My workforce will go to sleep!” He failed to notice that he was lying on correctly shaped plywood with no upholstery whatever.

Return to    ←Various chairs.

Okamura reclined work chair

OKAMURA,   ATLAS chair & Cruise concept.

Okamura is a major Japanese company and produced a reclined work-chair that was ahead of the field in addressing the biomechanical factors that are necessary to avoid or limit  LBP.

okamura1“Looks familiar, Henry?” was the message from John Jukes about this chair.  Sure enough it showed the semi  reclined work position that I had been advocating since 1998 on the web.  In my reply to Jukes I made the following points :-

  • The upright mode is in an adverse mid-upright position in its worst form, and the less adverse intermediate positions are allowed.
  • Improvements could be made, particularly to the positioning of the headrest which requires manual adjustment to provide the necessary support in the reclined mode.  As can be seen in the brochure photographs this is not done.
  • The method of changing from reclined to upright mode involves raising or lowering the seat.
  • There is a plethora of unnecessary controls.

As the 2T concept was considered ‘outlandish’ back then, this chair was a considerable leap forward by Okamura.  It has been suggested that Okamura designers had seen my web page.  I doubt this as they had failed to apply the essential requirements need to make this a more user friendly (and cheaper) work-chair.

However, congratulations to Okamura.  Also their Atlas model allows some insights into where their design went wrong in relation to the 2Tilt (2T) concept.

  • It has a reasonably good reclined position.  But then things become complicated as it differs from a chair designed along 2T principles.
  • Problems occur with the further design and is unintentionally shown in the photograph, above, as the users head is not being supported although there is a possible 40° forward adjustment.   This illustrates the point that adjustments are usually maladjusted and have confusing controls.
  • Screen Shot 2014-02-13 at 19.22.28
  • 1. Good.  Easily adjusted for users of differing height.  Integral and essential for the 2Tilt concept
  • 2. Pelvic support should  be at 200 mm. and not adjustable.  Usually adjusted to an adverse lumbar height.
  • There is no need for adjustment of the depth of the seat with a 2T design.
  • 3. Also no need for this adjustment.  If the FTS upright system is used, the headrest  remains well behind the users head,  no adjustment being required.  This becomes more complicated if a pelvic support system is used for the upright mode.  See note below.
  • 4. In the reclined mode the head-rest needs to be at about 6″ forward from the back-rest.    This depends on the degree (up to 40°) of thoraco/upper lumbar kyphosis designed into the back-rest.
  • 5.  Good.  The reclined back-rest angle is 45°.   Better at 40°.
  • 6.  Good.  The backward extended legs give greater stability in the reclined mode.
  • From the diagram it can be seen that there are some controlled adjustments which are sub-optimal and would be avoided in the 2T concept.
  • The upright mode is in the usual mid-upright position which may incurs a 40% axial compression penalty (Nachemson, Sato34 but not Wilke1) over standing and 500% over lying supine.   The less adverse intermediate positions are allowed.  The 2T concept allows intermediate positions but these are unstable and can allow rocking exercise.
  • The mid upright mode could be partially mitigated by correctly placed iliac support.  The emphasis here must be on ‘correctly placed’ and this can be easily adjusted into an adverse position which is not allowed in the 2T concept.  (Pelvic support →).
  • The seat is convex and can allow the user to sit back and take advantage of the pelvic (or better, ‘iliac’) support. In this case the headrest has to be adjusted back from it’s position that is required when reclined.  (See‘Ischial Off Load system’).  (see •3 above)
  • The user can also sit on the front edge where the seat is tilting downward as a FTS and where the head rest becomes irrelevant.  Feet would have to be braced against the floor to prevent slipping (See below).
  • Fixed at a low level,  the seat 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 work-table may be required (no bad thing).
  • I found the shift from the reclined mode to be awkward and difficult but can probably be eased by adjustment and familiarity.  Ideally, for the ‘2 Tilt concept’ this should be easy and without adjustment with the intermediate positions being unstable and can allow rocking exercise.
  • Ways may be found for this to be acceptable in a 2T solution, where there is a specified requirement for support from head to feet.  One solution is a leg/footrest that is retracted in the upright mode.
  • The 2T prototypes are monocoque and the leg-rest is straddled when in the upright mode which is probably impractical for an office model
  • It has plenty of room for improvement but the Atlas was the only chair designed for work in a reclined mode.   As combined with the specific desk it is awkward but a formidable (but expensive)  buy, and especially for those working in a trading environment.
  • Failure to take account of the necessary requirements for a reclined work mode (the 2T concept) has resulted in a clunky model resulting in, I think, a poor user uptake.  A pity! (See Requirements →).
  • See their website

Screen Shot 2015-06-04 at 14.25.32Screen Shot 2013-10-23 at 14.05.33

With the system shown below Okamura demonstrates the problem when the floor is used as the footrest in the reclined work position.  The work top would have to be very low and would be too low when in the upright mode.  The solution involves either automatically raising the work-top when entering the upright mode with a related variable height desk.  The problem is avoided with a desk-less work station.

Screen Shot 2016-03-11 at 13.45.45The Okamura website describes this “Ankle tilt reclining is a mechanism by which the chair seat sinks backward in sync with the reclining of the chair back. When reclining, the gradual opening of the ankle, knee, and hip joints without moving the ankle itself serves to create a relaxed state and promote better blood circulation. In addition, the fact that the chair seat does not push the body upward makes this a body-friendly reclining mechanism which reduces the likelihood of leg swelling and numbness. Since the chair moves in unison with the body, even if reclining is repeatedly done, your concentration will not be broken by feelings of discomfort”

A similar account of kinematic reclination in the Aeron chair can be seen on the HM website→

Okamura work chairs are good of their sort but have failed to produce a 2Tilt model. but nearly there ….Contessa

Okamura

The Contessa has pelvic support and a domed seat (ischial off-load) and the Leopard has FTS which might have a problem with slippage.

To see Okamura web→

 

The Luxos is sort of reclined with a stool for a leg-rest.   Good pelvic support and a forward tilt which are alternatives and not complementary but equivalent to Ischial offload system.   In this photograph the headrest is well out of the way in the upright mode.

Screen Shot 2016-06-12 at 13.25.48Okmaura Sabrina Chair has a “Synchro-Reclining” function enabling the chair backrest and seat to be synchronized by operating the lever located at the bottom of the seat.  The functions include a forward-tilting seat and adjustable armrests.    Okamura have seen the 2T details but fail to respond.   From the text thay may be   begining to accept my views   HAS

Luxos

Sit Stand & stools

A Partial solution.

The Sit Stand concept  has slowed following work showing less difference in sitting and standing intra-discal pressures than was first thought.  A comeback is occurring as the  importance of keeping staff exercised is recognised.   

Effect of axial loading  on IVD intra-discal pressure

Originally Nachemson and others showed that the standing position had a lower intradiscal pressure than upright sitting.  This suggested that incorporating sitting and standing, with a sit/stand desk, could be beneficial if designed into an office environment.
This concept  has slowed following later work (Wilke 1999) showing less difference in sitting and standing intra-discal pressures and the general recent ergonomic improvement of office chairs.

Effect of movement on the IV disc

The negative consequences of constrained sitting has been described by a number of authorities.  See ☛ Exercise & movement→.  It has been shown that disc nutrition depends on the pumping action of pressure changes due to changes of position and is probably important in avoiding later degenerative changes.  In the context of chair design, movement is comforting and avoids the adverse effects of a prolonged constrained static upright mode on general health (See (Lueder R 2002).


Variable standing may be ergonomically superior to the prolonged use of existing upright chairs.    See 
BIOMECHANICS that determine safe sitting→).    But, on the other hand, prolonged standing is tiring and affects venous return and can adversely affect body and cognitive abilities.   Most people prefer sitting, because it is energy efficient with less action by the Erector Spinae muscles than when standing.   However there may be situations where the concept is Screen Shot 2018-06-16 at 13.25.30applicable and as the  importance of keeping staff exercised is increasingly recognised.

Office-based’ studies

The first known ‘office-based’ study in the Department of Clinical Sciences and Nutrition, at the University of Chester, Chester, UK, 2016,  compared two days of continuous monitored capillary blood glucose responses to sitting and standing in normally desk-based workers.  The results provided encouraging signs of attenuating post-prandial glycaemic excursion  and why avoiding continuous sitting at work could benefit cardio-metabolic health.  The following articles are referenced:-

  1. Prologed standing is tiring and affects venous return and can adversely affect body and cognitive abilities. – Are Standing Desks The Biggest Sham Ever?→    Wilmot EG, Edwardson CL, Achana FA, et al. Sedentary time in adults and the association with diabetes, cardiovascular disease and death: systematic review and meta-analysis. Diabetologia 2012;55:2895–905.
  2. Saunders TJ, Larouche R, Colley RC, et al. Acute sedentary behaviour and markers of cardiometabolic risk: a systematic review of intervention studies. J Nutr Metab 2012;2012:712435.
  3. Gennuso KP, Gangnon RE, Matthews CE, et al. Sedentary behavior, physical activity, and markers of health in older adults. Med Sci Sports Exerc 2013;45:1493–500.
  4. Leon-Munoz LM, Martinez-Gomez D, Balboa-Castillo T, et al. Continued sedentariness, change in sitting time, and mortality in older adults. Med Sci Sports Exerc 2013;45:1501–7.
  5.  Levine JA, Schleusner SJ, Jensen MD. Energy expenditure of nonexercise activity. Am J Clin Nutr 2000;72:1451–4.
  6.  Koepp GA, Manohar CU, McCrady-Spitzer SK, et al. Treadmill desks: a 1-year prospective trial. Obesity 2013;21:705–11.
  7.  Peddie MC, Bone JL, Rehrer NJ, et al. Breaking prolonged sitting reduces postprandial glycemia in healthy, normal-weight adults: a randomized crossover trial. Am J Clin Nutr 2013;98:358–66.
  8.  Pescatello LS, Arena R, Riebe D, et al. (Eds). ACSM’s Guidelines for exercise testing and prescription. Baltimore: Lippincott, Williams and Wilkins, 2013.
  9.  Speck RM, Schmitz KH. Energy expenditure comparison: a pilot study of standing instead of sitting at work for obesity prevention. Prev Med 2011;52:283–4.
  10.  Blaak EE, Antoine JM, Benton D, et al. Impact of postprandial glycaemia on health and prevention of disease. Obesity Rev 2012;13:923–84.
  11. Ben Schiller Service FJ. Glucose variability. Diabetes 2013;62:1398–404.
  12.  Satya Krishna SV, Kota SK, Modi KD. Glycemic variability: clinical implications. Indian J Endocrinol Metab 2013;17:611–19.   A number of bio-mechanically efficient stools have been produced which usually incorporate a FTS, contouring and sometimes iliac support.

A ‘stand’ mode can  be incorporated into the a 3M ‘desk-less’ workstation which then becomes a 4M concept (and a ‘full’ solution ).  This extra mode results in the  first change since the inception of the 2T concept in 1998.   (See ☛workstations→).

Stools

Screen Shot 2015-09-30 at 15.05.52

Screen Shot 2015-09-30 at 15.15.20☜ The Pesko ERGO FLEX M 1_1 also incorporates a ‘wobble”.

A recent, more complex example is the Freedman chair in which the 2 halves of the seat can move independently, intending to accommodate spinal irregularity (scoliosis) and pelvic side tilting.  The emphasis is on the FTS concept and movement.☟

freedman-chair

Screen Shot 2017-02-20 at 18.22.18The HiLo
by Box Clever 2016, an innovation agency led by industrial designers Bret Recor and Seth Murray for Knoll  Knoll produce a number of high end task chairs with semi-remediation such as pelvic support but have not yet made the jump into a fully remediated chair.

It seems to be an indoor version of the old ‘Shooting sticks’ that I used to use.  Very sensible. (→ https://www.knoll.com/search-results?searchtext=HiLo&parent=1347382605724 )

 The exact converse system

is designed to get the user off the stool to make way for another user.   A good example is an expensive designer stool with 4 legs and painted black as used in Mac shops.  Photo on 06-01-2015 at 12.49Being an enthusiastic  Mac user myself, I am only too familiar with these.  They have a round, horizontal seat without conturing which allows point pressure between the ischial tuberosities (ITs) and the hard surface.   They have a newer model which is ergonomically no better.

Problems may arise for staff & users who have to sit on them for longer periods. The view is of myself but It can be seen repeated in some random shots of staff users.   In the unavoidable, high loaded, upright position, the pelvis tilts backwards due to  the horizontal surface of the stool seat.  This is augmented by leaning forward, but some slight positive effect may occur by taking weight on the arms.

Screen Shot 2015-01-20 at 12.27.40

A light hearted account of 19c office conditions is relevant here.

Next ☛ A FULL SOLUTION

Various chairs. How do they measure up?

My remarks are intended only to illustrate points in relation to the 2T concept.

They are not intended to imply either a recommendation or that any of these chairs may be in any way unsafe.  The points made are related to the evaluation of bio-mechanical factors, some knowledge of which is helpful.   Links provide access to manufacturers website so that their range and hype can be compared.

Screen Shot 2013-10-23 at 14.04.26Much work has been done in the design of chairs as a result of the general perception that ’correct ergonomics’ is required for the avoidance of LBP.   On talking to designers I find that they aim for comfort, that treacherous guide  which only turns up truthfully when the bio-mechanics (ergonomics) are fully correct”. See  ☛Comfort→.     Also a hindrance is Familiarity bias→.  (cognitive dissonance).

 Simply, prolonged sitting still results in backache.


Memo to a general reader.

Superb engineering and visual design are fine but are not understood or appreciated by the actual spine.  The spine is only affected by the bio-mechanics presented to it.    An uprigh work mode can only be a partial solution  and can only go some way to meet the spinal bio-mechanical challenge.    Hype and selling points, bells & whistles and apparent comfort are irrelevant.
At present real, but partial, safeguards are only :-

  •  a Forward tilted Seat
  • or pelvic (Iliac) support.   These  have to be designed with precision to be effective.  This is often not fully understood.

A knowledge of the 2T concept, a full solution, is helpful with the understanding of the following comments.

 

A garden recliner.  It has only two positions.  Both are shown.  Simple but very comfortable.

recliner1    recliner2 There is no shaped back support, having been designed before the importance of this had been appreciated.     It 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 with this possibility and heard no more. The  leg-rest retraction is interesting, simple and has points for a 2Tilt concept.

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

 

Screen Shot 2013-09-19 at 17.07.27This young lady looks very happy!

But perhaps she would be happier with leg and neck support?

 

Screen Shot 2013-09-19 at 17.02.39Another excellent, 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 2013-09-19 at 17.08.56A 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.

Screen Shot 2014-02-13 at 13.06.54

Nice view!

 

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

 

HM2The late John Jukes, who was investigating the incidence level of musculo-skeletal symptoms in offices, told me that he suggested to a leading manufacturer that ‘pelvic support’ should be incorporated in their models but said this was ignored.  Perhaps annoyed by his rebuff by the firm, Jukes 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”.   Screen Shot 2013-09-29 at 18.33.37The Gorman design,  suggested to them by John Jukes in the first place might have saved them and their clients, a decade  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→.

The Hermann Miller Aeron

HM1Aeron chair has been chosen for consideration as an example of a top-range, highly engineered and carefully designed upright 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.   It is essentially used as a mid-upright chair and shares the same biomechanic problems as any other upright chair. Again, 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.  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.  This has been subsequently added but could still benefit from further remediation.

Although the chair can be tilted back to about 45°,  reducing axial loading, it does not have the necessary head and leg-supports to make this a true working position.  The seat has a variable tilt which is related cybernetically to the backrest (Kinemat tilt) to avoid the necessity for fiddly controls (although many fiddly controls are still present). This may be good but is complicated and allows the adverse intermediate positions.   These are not allowed in the 2T solution, and also provide a ‘dynamic seating’ element.. The seat is convex and there is a backward slope of the rear half of the seat (evident in the photograph, above) which  brings the pelvis back into contact with the ‘pelvic support’ for this to function effectively.     The convex front half goes a little way to being a forward tilted seat (FTS) but seems barely adequate to be effective although some users admitted that they usually perched on the front edge and so achieved the advantage of a forward tilt mode. This seat
shape is an example of the ‘Off Load’ system’ which the Makshous study showed to have biomechanic advantages which allows this chair to be upgraded from a simple upright chair.
Screen Shot 2018-06-08 at 19.53.52The 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.”  The sounds as if they have read this work.  A step in the right direction, at last.  The photograph is of one of the co-designers, Sam Hecht of Industrial Facility, photographed by Gerhardt Kellerman.

Mirra 2 HMThe ‘MIRRA Chair. The pelvic support 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 OKAMURA ATLAS chair & Cruise concept.

Okamura Atlas“Looks familiar, Henry?” was the message from John Jukes about this 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’.

okamura1The designers had probably not seen the principles that I had formulated 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.

OKAMURA CONTESSADesigned and engineered to a high standard of sophistication but, again, there is a plethora of unnecessary controls which are so loved by contemporary designers.  Most  should be scrapped or disconnected by a user who is aware of the adverse positions on spinal pathology.

The brochure states, ”The lumbar support gives you comfortable support.  You can adjust the lumbar support backward and forward up to 15 mm , and up and down to 60 mm.”   The upright work position shown is acceptable as the ‘lumbar’ is actually  ‘pelvic support provided it cannot be adjusted upwards above 20 cm.’.  Gorman  showed true ‘lumbar support‘,above 20 cm, to have the opposite effect to that desired and later confirmed by pMRI scans.

The reclined mode is about 50° from the floor, a little short of the ideal 45° but acceptable. The figure given above is 26° from the illustrated upright mode.  It relies on the ‘off-load’ domed seat.   I prefer the forward tilted seat but know of no evidence that shows one system to be better than the other.

The OKAMURA LEOPARD chair       

Okamura LeopardNot intended as a work-chair, it is aesthetically superb and looks right, however the fixed head-rest is only excellent for contemplating the ceiling.     Essentially a waiting room chair. 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).

Pledge BT3 20/20 (Task) Gorman, an engineer turned chiropractor, worked with PLEDGE to produce models incorporating pelvic support.

Screen Shot 2013-09-29 at 18.34.21Controlled 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 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 Screen Shot 2013-09-27 at 22.34.23have 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 is another good upright chair that incorporates ‘Pelvic Support’, here called  PAL™.  This allows it to be considered as a semi-partial solution for full Safe Sitting.

  • Haworth ZodyAs 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.

Screen Shot 2017-05-08 at 15.03.35Ferrari 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”      

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

The Modern Zure Office Chair

Screen Shot 2018-06-22 at 19.17.18“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.

A selection from ‘Posturite’.

Screen Shot 2016-06-12 at 14.02.18

 Dynamic seating & motionWobble ball

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.

Swing seatThe 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
Screen Shot 2013-10-19 at 17.40.18This ‘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 a chair 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, with no need for adjustment.

The KOEHL AIR-SEAT, from Holland.

screen-shot-2016-09-21-at-20-44-26“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 the chair without the system.  A full account is given in  ☛ EXERCISE & movement→

the BackStrong ChairBackStrong Chair

The 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 a bio-mechanic (ergonomic) fully remediated chair 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.
  •  In the present form it should probably not be used for longer than 6 hours.
  • “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?

 

AN EXISTENTIAL THREAT – A new breed 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 models 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.

AltmarkNow, in 2015, a chair 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.

WHY? Mandal’s Homo sedens.

    The recommended ‘correct’ position was fundamentally wrong.  He  suggested  that   “Mankind has progressed from Homo sapiens to Homo sedens”.   AC Mandal was a leading Danish surgeon.  Becoming disillusioned in the conventional wisdom of the Screen Shot 2018-06-12 at 21.12.51principles of correct chair design, he transferred his scientific and critical training to that of the biomechanics of sitting.   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.    ‘The Seated Man’119
Screen Shot 2015-11-27 at 13.36.05

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.

Screen Shot 2016-03-16 at 20.12.45The recommended ‘correct’ position was fundamentally wrong.   He wondered how such a poor position could have been accepted as correct.     He suggests that this posture was developed by taking a standing skeleton and sitting it on a chair.

 (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 is 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.
  • 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 2015-11-28 at 15.44.41
  • 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→
  • Screen Shot 2017-02-11 at 17.18.18
  • This mistaken view of correct seating is still accepted and widely promulgated by authorities who advise on such matters.
  • His proposed solution was a combination of height adjustable desking and forward tilted seat similar to the equestrian seat.FTS
  • And belew a typical example of an authoritative diagram, (one that we all, in the UK, know and love) that illustrates ‘correct’ seating posture.
  1. The head and neck are in a terrible position.     A ‘dowager’s hump’ is already appearing in the upper thoracic joints!  The artist is right, the concept is wrong!Badsit 2014-04-03 at 14.12.49
  2. And the small amount of back adjustment is irrelevant and is nearly always adjusted in the wrong direction.
  3. The back rest seems to be providing unsatisfactory lumbar support. A mid-upright chair of this sort requires iliac support.
  4. The upright position = high axial spinal loading.
  5. The hip joint is flexed to a right angle. This has the effect of tilting the pelvis backward.    A forward tilted seat would help.
  6. The conventionally recommended knee position is also a right angle. This is wrong as the knees should be moved for physiological well-being.
  7. In general, a foot rest is not desirabl as it limits leg movement.  However a ‘sprung’ footrest which exercises the calf muscles can be helpful and comforting.

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

badsit5The 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 21.04.14This 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.      Screen Shot 2016-02-14 at 18.18.00Most 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).Chairs2014-04-03 at 14.10.35

 

Ergonomics-standard-diagramThe 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?

Screen Shot 2013-10-13 at 14.47.34

 

 

How other people sit

Better!   But not for office work.

Japan.

Screen Shot 2013-09-26 at 22.51.16The 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.Screen Shot 2013-09-24 at 19.24.16

 

Screen Shot 2013-09-26 at 22.51.43The 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.

 

JapSit2

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⟶

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

HOW WE SIT NOW

How we sit now is badly!  The recommended ‘correct’ posture  being almost impossible to maintain, most of us sit in a posture that can be shown to invite spinal breakdown.

The photographs show a group of doctors and physiotherapists who are attending a course on orthopaedics.    Most are sitting slumped with rounded back. This allows the pelvis to tilt backwards and  stretches the posterior ligaments but is not as adverse as sitting bolt upright as currently advised and is nearly impossible to maintain.

WWSN1

 

WWSN.2

The chair seats are parallel to the floor so that an upright posture must entail flexion of the hips at a right angle.  Crossing of the legs accentuates this.    The lumbar lordosis is lost and a flexed position of the lumbar joints occurs which can be clearly seen.  Note that none is using the backrest except for the doctor in the white shirt  who is in a semi-reclined slouched position.  In this mode the lower lumbar joints may be unsupported and flexed (but see below) and the posterior ligaments are stretched but the intradiscal pressure is reduced from 0.44 MPa to 0.27 MP as shown in a study in Ulm by Wilke (Wilke 2001).  If fully supported this is moving towards the 2T (3M) concept of  a reclined work position and John Jukes commentated was commonly seen in offices (See Managing the Ergonomics in the office→).  WWSN.4

 The physiotherapist in the check shirt is sitting forward on his seat in order to extend his hips slightly.    The table is too low for him and so he loses this advantage as he has to  bend down towards the table top.  In Wilke’s study bending forward about 20° with straight back and without arm support increased the pressure to 0.63 MPa up to 0.83 MPa, which was reduced  to 0.43 MPa when the elbows were supported.   The physiotherapist in the striped shirt has adopted  an extended position as he is able to brace himself with his arms.  This has the added advantage of forward rotation of the pelvis and so protection of the disc wedge angle. A work position, of this sort, was found to be the commonest (52%) in the quick study (below).

WWSN.5

In the next picture I am seen using a stool shaped like a saddle.   My hips are extended but this advantage is lost as the table is too low.  A saddle seat becomes uncomfortable due to localised IT pressure. This happens less with the equestrian saddle due to movement.

 

A pilot study, in 2013, of how we sit now by students, at Cambridge, working on a project for a 2Tilt chair in relation to desk interface  and office space indicates results, from a nearby office, that might surprise some people.   This was occasioned by the somewhat confused results of intradiscal pressure studies where there is a variation in sitting positions and units used and is also relevant to the single pMRI study (Smith 2006).  A more complete study is required.Screen Shot 2013-09-24 at 19.25.36

In the absence of reclined work chairs only15% + 3% were sitting upright.

The slouch.

Another reprehensible posture –  or is it?

Screen Shot 2013-10-23 at 14.22.53The popular slouched or slumped posture when sitting in an upright chair looks very wrong if  the misconceived ‘correct’ sitting posture, as excoriated by Mandal, and confirmed by the correct ‘preserve the lumbar lordosis’ dictum is accepted,   It is assumed that this posture will cause LBP. This may be true for Western societies where children have been universally accustomed to sit in ergonomically unsuitable upright chairs. This is an oversimplification when non-western sitting is taken into account.

slouchThe diagram shows that the flexion occurs at the upper lumbar joints with normal, or increased up to 40°, kyphosis of the thoracic spine. The pelvis lies fully on the surface of the seat and cannot tilt backwards.  The two lower lumbar joints, where IV Disc derangement typically occurs,  are safe with the wedge angles preserved.   The position is not very different from that in a semi-reclined chair.   In the 2Tilt (3M) version emphasis is placed on correct support from head to feet, with a slight degree of iliac support to prevent sagging at the lumbo sacral junction.  Wilke  found the L4/5 intradiscal pressure to be 0.27 MPa against  0.45 to 0.50 MPa when sitting upright (Wilke 2001).

The modern epidemic of backache is associated with lack of exercise and, In spite of uncertain epidemiological  evidence, prolonged upright sitting in chairs.    This is a relatively modern habit.    High backed chairs were an article of state and dignity.    Even monarchs used their thrones for limited and specific events.  Most people sat or squatted on the floor in various ways, which were culturally determined, and  benches and stools were the ordinary seats of everyday life.   It was in the 16th c. that the chair ceased to be a privilege, and became a standard item of furniture for anyone who could afford to buy one and the chair speedily came into general use and that is how we sit now.

Joint stoolJoint stool. These were made in large quantities in the 16th and 17th centuries. They were the most common form of seating before chairs became universal.  Users tend to perch with hips extended as recommended by Mandal.  People did not seem to be bothered much by backache. They were erroneously called ‘coffin stools’ in the 19th century.    Shown are two late 17th c. models.

Next see ☛ How other people sit

And   ☛ Various chairs.  How do they measure up? →  

See also a lighthearted account of the Victorian office. which also includes an account and treatment of RSI (WRULD).