Chair DESIGN & Backache

Screen Shot 2017-05-23 at 06.52.48LLB related to sitting.  Some essential reading  for designers of ergonomic chairs and retail office chairs if they wish to improve the ‘ergonomics’ of their models with overwhelming
health selling points.    
Chair designers still lose out, often having familiarity bias in recognising the underlying bio-mechanical essentials for a chair that will supersede the existing ‘cool’ models.   See  for the losers Various chairs. How do they measure up?.


In general

  • Low Lumbar Backache (LBP) results in personal morbidity, loss of earnings and huge cost to industry. ☛ Prevalence and economic cost of LBP.
  • A technical ‘fix’ is required if the increase  is to be halted.
  • At present most work chairs can be unkindly designated as ‘Machines for making Backache’.   ☛HOW WE SIT NOW
  • Pressure studies show that upright sitting itself is seriously adverse ☛→  Loading
  • The mid-upright mode also carries other marked defects which are accentuated if the 90° hip angle (seat parallel to floor) or lumbar (as opposed to iliac) support is incorporated.  ☛Pelvic v. lumbar support→.
  • Recent scientific work on spinal pathology and biomechanics show that these ‘correct’ details are Mandal2seriously adverse to spinal well being.  See adverse effects of ☛mid-upright seating→.
  • The mid-upright position details, accepted as ‘correct’, seem to have been codified in the 1920s as a result of a false premise (see Mandal. AC., The Seated Man (Homo sedens).1985. Dafnia Publications,  ☛ Homo sedens→)
  • Ergonomic chair design seems to have come to the end of the road with some, but not great, success in avoiding Low Lumbar Backache (LBP).  A new fix is in order.
  • Bio-mechanics (ergonomics) show that a reclined work mode is essential for prolonged work.    reclined work mode→
  • A fully practical solution can be  effected by the 2T concept.   A ‘paradigm change’?
  • How ‘ergonomic’ are your designs?  How many boxes do they tick?

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May I be so bold as to suggest that….

  • You must not be  misled by ‘comfort’, that treacherous guide  which only turns up truthfully when Screen Shot 2018-06-11 at 21.01.07the bio-mechanics (ergonomics) are fully correct. Comfort is improved the nearer a full remediation  is approached.  Full remediation = maximum comfort. See ☛ Comfort→
  • The first concern should be the Hippocratic Primum non nocere “Do no harm”.   Remediating the ergonomics is therefore essential. ☛ Remediation→
  • It is most important to avoid →Familiarity bias.
  • It is hoped that this work may provide you with the resource for the requirements for safe that
    • Bio-mechanic adverse designs can be avoided.
    • And →Normalcy Bias for your manufacturer

Correct?   No!

Screen Shot 2016-02-14 at 18.18.00See ☛Effects on the upright seated posture→
Examples of ‘CORRECT’ .

Screen Shot 2016-01-14 at 18.19.39There is now no excuse for poorly designed chairs and the conventional mis-advice that is perpetuated.    It has to be said that these references, below, are to the back-rests of upright chairs and many of the tips are good,

Low Lumbar Backache  (LBP).  Some views.

All designers researched at a trade show expressed that their main object was based on a search for maximising ‘comfort’.    Instead it should be  ‘Do no harm’  based on correct medico-scientific research, as described here.   See Comfort→.  Forgive me for harping on this.  It has occurred to me that, in spite of much good work, this misconception and familiarity bias may have held the chair industry back from a much needed sitting artefact.  I hope that this will gradually come to be recognised.

cantabThe advantages of the unstable 2T (3M) transition mode are still not understood.      The unstable TRANSITIONAL MODE. It’s importance.

  • The biomechanical imperatives show that a safe chair can easily be achieved with the  ☛ ‘2 Tilt principle’→.
  • You can try embarking on the more adventurous 2T or 4M desk-less work stations.
  • The 4M workstation will be particularly relevant to the coming AI, VR & MR developments.
  • Please do not hesitate to get in touch for queries, comments or more design details.  Contact→
  • At present (2015) designers have expressed worries that an innovative and supposedly  ‘paradigm change’ expressed in the 2T concept excites negative familiarity bias.   This is becoming less. and the concept is especially welcome with
    • The ‘millenial’ post-graduate age group. It was noticeable how students at Cambridge loved the prototype and used it whenever possible.
    • People who have Low Lumbar Backache.  This large cohort, about 70% of the UK population,  immediately see the advantages and ask “Where can I get this’.  (Of course, they can’t!).
  •  Insurance is already begining to take an interest (personal communication).     HAS
  • Once people understand that it has health benefits, and possibly even more than any existing chairs, they will demand them. 
  • The offices of companies such as Google, Skype and Facebook, are like a playground with innovative furniture which would have looked outrageous ten years ago.  This could include the 2T concept that I introduced in 1998.  which is now no longer looking extraordinary.
  • Screen Shot 2016-03-18 at 19.28.20The TriModal (3M) or 2T CONCEPT is just that – a concept.  It provides a designer with a practical basis for development of an ergonomically optimised office chair which can be achieved in a number of ways and styles.
  • Design details have emerged from work on prototypes and are available on request.  The 2 TILT CONCEPT.→

pMRI.  Confirms assumptions derived from these bio-mechanical studies and clinical observation have been validated by pMRI scans (Smith FW,2007) which show that the reclined mode ensures migration  of IVD nuclear material away from dangerous position near the back of the inter-vertebral joint which occurs with upright (90°) sitting.  Screen Shot 2016-03-19 at 13.15.20 It is difficult to refute this evidence.

“Desks are rather a thing of the past – Dickensian even. They evolved as tables with storage developed, alongside chairs. The whole combination seems a way of reducing/avoiding the need for floor sitting or squatting and a means to provide a convenient standing/sitting presentation of objects for working with at an ergonomically higher level.  They were there to support and present paper documents and the like. Hardware, since then, was largely developed to be used with/on them and has evolved through typewriters and similar devices to today’s electronics. Once that demand for physical documents has been reduced and even eliminated by ‘paperless’ office tech.”‘  (P. Bessey).

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  • Screen Shot 2016-05-17 at 15.38.25Office managers should consult this blog as a resource.  It allows an alternative view to the usual hype from manufacturers, often laughably misguided.   For further advice, see Office managers in MANUFACTURE of ergonomic chairs→


With the advent of AI and robotics affices will be geared to the emotional and physiological requirements of the highly paid staff.   2 Tilt chairs and their 4M derivatives will be exactly relevant.   But also see ☛ The end of sitting? →


A digression…   Screen Shot 2016-06-05 at 15.25.14

Healthy officeSee Ergonomics and office stress.

and further reading from this post →


Sitting disease’

Compared to people who sit the least, those who spend most time in a chair have a 112 % higher risk of developing diabetes, a 147% higher risk of suffering “cardiovascular events” such as strokes and a 49%t increased risk of death from any cause.  (   Alarming but not entirely an effect of the bio-mechanics and not examined here.  However some posts are relevant.    But also see ☛ The end of sitting? →

A digression on

OFFICE STRESS & Backache→Office env




Screen Shot 2017-05-22 at 17.22.25The early concept depended on 2 positions, or modes, hence 2Tilt or ‘bimodal’  (2M).  When I came to realise that the transition stage also carried benefits, if unstable, it became a mode in it’s own right.  Hence the 2t became tri-modal (3M).    If it can be adjusted to stop in mid-range it becomes effectively useless and is no longer a mode.  Bias makes this concept difficult for most designers who have been taught to aim for infinite adjustability for comfort.  A midrange position is, or is nearly,  maximally ergonomically adverse and some users might mistakenly adopt it for prolonged work.  Might they do this in the upright mode?   Perhaps not as they have a more comfortable option with the reclined mode.   Only time & experience will tell but that is why I have, pro tem, stipulated that this should have remediation built in, preferably a Forward Tilted Seat (Mandal) or pelvic support (Gorman).    With a ‘deskless chair’ or workstation a 4th standing mode is incorporated and the concept becomes 4M.

I am merely providing a concept for designers, to use to help produce an actual chair that can be used for sitting.