Category Archives: THE 2 TILT CONCEPT

A paradigm change for prolonged sitting

Ergonomics for DESIGNERS of work chairs

May I be so bold as to suggest that….

  •  Ergonomic chair design seems to have come to the end of the road without huge success in avoiding LBP.
  • A new fix is in order and can be effected by the 2T concept.   A ‘paradigm change’?
  • This can only be achieved by an understanding of the  biomechanics. It is hoped that this work may provide you with this, a resource describing the requirements for safe design.
  • By incorporating the points made in this work,  comfort and ergonomics of both the simplest and most advanced ‘ergonomic’ chairs  should be improved .
  • You must not be  misled by ‘comfort’, that treacherous guide  which only turns up truthfully when the bio-mechanics (ergonomics) are fully correct.  See ☛ Comfort→
  •  Remediating the ergonomics is more important. Comfort is improved the nearer a full remediation  is approached.  Full remediation = maximum comfort.
  • The correct search should be for the Hippocratic “Do no harm”.
  • Bio-mechanic adverse designs can be avoided.  Why? Mandal’s Homo sedensScreen Shot 2016-01-14 at 18.19.39
  • There is now no excuse for poorly designed chairs and the conventional mis-advice that is perpetuated.   ☛ Various chairs→
  • Some selling points to manufacturers and architects are added if required.
  • The comment of Kenichi Ohmae (below) is apposite.

SLEEP & productivity

Anecdotally the first criticism of the 2T concept, back in 1998, was from a CEO “This is too comfortable. My staff will go to sleep”. Although he was lying on the P1 prototype with no upholstery whatever, just correctly shaped ply-wood. I responded that a nap might benefit productivity and it was unreasonable to keep staff awake with uncomfortable chairs.   I was unaware of the later research.    (see ☛ Sleep→ in the early 2T concept under ‘criticism’.)

Vincent Walsh, professor of human brain research at University College, London, suggested that a sleep of between 30 and 90 minutes in the afternoon could help companies improve productivity. A poll of 2000 UK office workers by the energy drink manufacturer, ‘Lucozade’ (2013), 22% reported having fallen asleep at their desks, usually in mid afternoon, due to an energy slump, usually lasting about 47 mins and associated with large lunches, sleep deprivation, alcohol and ‘unhealthy’ snacks. Research at the University of Michigan found that the subjects who had taken a nap felt less impulsive, and weathered frustration more easily, than those who watched a nature video (No ref). (See ☛Uptake?/Implications?→)


metronap009The MetroNaps EnergyPod is intended as a sleep module for users who wish to take a nap.  The hood allows it to become a semi Pod. It is of interest as it could be incorporated into a 2T chair (3M or 4M) and contain the monitor etc.

On their website they say “In recent years, countless studies have extolled the virtues of napping.  A quick power nap can sharpen your focus , boost creativity, and mitigate the effects of sleep deprivation. But if you work a 9 to 5 at an office, how can you fulfill your nap quota without being called out for sleeping on the job?If you work at the posh offices of Google, The Huffington Post or Cisco Systems Inc., you take a break from your desk and slip into your own private “sleeping pod.” The $13,000 pods are the brainchild of Christopher Lindholst and Arshad Chowdhury, who have been preaching the benefits of napping at work since they opened their company MetroNaps in 2004. Starting out as a retail operation, MetroNaps now manufactures a line of sleep pods and acts as a kind of “sleep consultant” for companies, offering guidance on how to work napping into a work culture that they say is becoming increasingly accepting of the idea.”

Arianna Huffington, Editor in Chief, Huffington Post Media Group“When we first started the nap rooms, a year and a half ago, people were reluctant to use them. Now, we need to open a third one; they are so overbooked. People blog even about the impact it has on them to just get 20 minutes in the middle of the afternoon.” – As quoted in CBS This Morning, June 12, 2012→


With the advent of AI and robotics offices 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.  A sleep hood can be incorporated into the design and avoid the neccesity for a dedicated ‘nap-room’.         Next see ☛Early 2Tilt chair CONCEPT and criticism

For ARCHITECTS. ‘Coolness’ is the word.

 For New offices ‘Coolness’ is the word to  excite media interest for both the company and the Architect/Designer.   Most firms aspire to project this cutting edge image.    A 2T chair answers this exactly and in addition reduces LBP and increased productivity by lessening stress and morbidity.

Many distinguished architects have tried their hand at chair design.   A few examples are shown.

Screen Shot 2018-12-13 at 16.04.05

Brilliant as their designs may be, as can be seen, their efforts have been sorely lacking in knowledge of ergonomics  when it is only ergonomics that determines comfort and avoids harm to the spine.

Recently I have realised that they play an important part in development as they are able to dictate requirements for projects.   Ergonomic knowledge  becomes vital to avoid stipulating work chairs with potentially harmful outcomes.

Bright young  architects already see the point.   This early example by Aaron Chetwynd was much admired.

Deliberately looks traditional so as not to excite Familiarity Bias, and frighten the horses.  With only a few minor design alterations it is ready & suitable for a 3 or 4M model.

THE RELEVANCE OF THE 2t  (3M, 4M) concept

All the relevant factors are ticked :-

Screen Shot 2018-06-16 at 16.05.47 A CONCEPT only allowing INDEPENDENT DESIGN. Based on the bio-medical evidence, provides a template for optimising the ergonomics of chair design.

Screen Shot 2018-06-16 at 16.05.47Based on the scientific bio-medical research it identifies & remediates each & every adverse effect of the upright work position responsible for musculo-skeletal discomfort which include backache, LBP, and more serious spinal breakdown. The only solution to do this ☛ 2T CONCEPT a full solution

Screen Shot 2018-06-16 at 16.05.47Maximises comfort.  This depends on the ergonomics and NOT on short term opinion.  Fully correct ergonomics = maximum comfort. →

Screen Shot 2018-06-16 at 16.05.47Provides dynamic MOVEMENT under the control of the user.  Affects health & comfort and also has a rehabilitation use   ☛EXERCISE & movement→. ☛ The unstable TRANSITIONAL MODE. It’s importance. →

Screen Shot 2018-06-16 at 16.05.47Reduces manufacturing costs.  Correct design avoids expansive confusing adjustments →

Screen Shot 2018-06-16 at 16.05.47Subsidiary factors include relevance to the modern and future office environment, cost, brand image and user targeting.


Screen Shot 2018-06-16 at 16.05.47Evolves easily into deskless   ☛OFFICE WORK-STATIONS →    particularly relevant to the coming AI, VR & MR developments.  

Screen Shot 2018-06-16 at 16.05.47A PARADIGM shift.  The way ahead?    It is already happening!    The boundaries between contract and home furniture  are decreasing and the division may be disappearing entirely.   The only problem is that no such chair exists yet in the market.   An opportunity for someone?

Office ergonomics

Poor seating is a major stressor resulting in reduced performance and absenteeism. (☛OFFICE HEALTH, Stress & Ergonomics )  At present I know of no chair in the market that fully remediates this.     New seating concepts are coming forward which will not only revolutionise seating but also impact on office design. In a few decades a chair set before a desk, and arranged in straight lines will be perceived as not only dated but hopelessly inefficient. There is an increasing interest in this direction (☛WORK-CHAIRS, a new breed with a reclined mode. )     Also see Mindjet which with much hype describes GlaxoSmithKline’s purposed “deskless office” below.   ‘Great it ain’t’ but shows the way things are going.Screen Shot 2016-01-15 at 20.22.14

The designers of this layout obviously did not have the benefit of having seen the work of John Jukes described in  ☛OFFICE HEALTH, Stress & Ergonomics⇒ which were tested in the field but has not been universally adopted.  His recommendations for Office Environment Optimisation  achieve lower staff stress levels and higher productivity.    For a discursive account See Office environment stressors→

 Peter Bessey wrote to me  “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., then there is once more a blank page to draw on.”


Screen Shot 2018-11-28 at 15.32.37The 2T (3M or 4M) derivatives) are the systems of choice for office and longterm home activities such as Gaming, and potential for sleep.   Ergonomics that avoid harmful effects are paramount and secondarily ensure maximum comfort..

In the home sitting is less prolonged and less stringent ergonomic requirements can be allowed. ☛  EASY CHAIRS  .  It is still advisable for ergonomic adverse chairs be avoided.

Screen Shot 2018-12-09 at 20.33.22For a discursive account→


2T and optimal seating.

An overview forScreen Shot 2016-03-15 at 16.43.33


I had rather forgotten about ‘comfort’ as it had been shot down by the scientific community as far back as 2003 (again see .   It should be, as in the Hippocratic oath –  Do no harm.   After last week (2015)  I have added “This is important ……with ‘comfort’ which misleads, being that treacherous guide  which only turns up truthfully when the bio-mechanics (ergonomics) are fully correct.   At present there is no chair on the market that does not have this potential.  Simply, prolonged sitting results in backache. Stop.  At least potentially for about 70% of users and health problems for 100%.

The search for comfort may have misled chair designers resulting in no ergonomic optimum chair on the market.  ☛ Comfort→


A plethora of adjustments is confusing and can be adverse if adjusted wrongly.  Ideally they should be avoided as far as is possible.  This should benefit both design and cost  ☛ Adjustments→



Seep of between 30 and 90 minutes in the afternoon could help companies improve productivity.  ☛ Sleep→


Chair designers say  “I agree but this concept is ahead of it’s time.  Familiarity bias will strike in and uptake will be poor.”    PR people say the opposite.  “This is a ‘paradigm change’.    Once people understand that it is safe and possibly even safer than any existing chairs, they will embrace them. There will be large media interest.  This will ensure automatic PR,”  Big uptake will occur rapidly and firms without a 2T product in their range will miss out, possibly terminally (to use medical jargon).   They may experience ’ Normalcy Bias’    as did the good people of New Orleans as hurricane ‘Katrina’ approached.  See  ☛ Familiarity bias→


People with ‘special needs’ are universal and these needs require to be addressed,  particularly in a reclined mode.  The 2T concept is particularly suited for this.  See ☛ special needs→

←Return to  ☛ 2T CONCEPT a full solution

Screen Shot 2016-03-17 at 13.34.20

The unstable TRANSITIONAL MODE. It’s importance.

This is not just a quick transition from the reclined to the upright modes (2T) but provides physiological benefits and is itself a mode.  The concept is renamed the Tr-Modal (3M).  2T = 3M.

Screen Shot 2018-10-22 at 13.43.40

Screen Shot 2015-10-07 at 13.43.222Tilt Principle 3  Requirement 9.. The adverse intermediate upright positions should be unstable.  This allows an easy and rapid transition from one mode to the other and no adjustment is allowed to maintain an intermediate position.

This may seem counter-intuitive.  Why shouldn’t the user be able to sit easily in any position that seems comfortable?   It worries chair designers dreadfully although they may not be bothered by the ‘dynamic seating’ concept..

  •   It is, equivalent to the mid upright position of most office chairs, carrying an ergonomic penalty.    A user, used to a mid-upright chair,  could use an adjustment to maintain this position for long periods which would add an unnecessary adverse effect to an otherwise optimal system.
  • The intermediate positions being unstable require muscular effort to be sustained.   On moving back a few degrees from the stable forward upright mode the occupant enters this upright unstable position which provides proprioceptive feedback and frequent small amplitude pressure changes.
  • A user has a choice and may find a short episode of this low amplitude exercise pleasant.  Longer periods are liable to be tiring.
  • There is also an added advantage  in providing therapeutic exercise following an acute LBP episode with it’s resultant muscle and reflex atrophy. (See ☛Anatomy/muscles).
  • Addition of a sit/stand mode in the 3M version allows the user to walk around.  ☛ SIT/STAND (& stools)
  • Why add to extra cost?
  • Spinal movement & change of position are important for a number of reasons including IV disc nutrition. ☛  Movement & exercise→
  • Dynamic Seating’.Recently there has been interest in continuous small amplitude movement for upright chairs, the chair re-aligning with the users centre of gravity.  ☛  Movement & exercise→
  • 2T exercise and movement systems   ☛  Movement & exercise→
  • Sit/Stand. Bio-mechanically superior to the use of existing upright chairs and can be an adjunct to the 2T system which then becomes a ☛ 4M work-station→ concept (and a ‘full’ solution).☛ SIT/STAND (& stools)

A specific illustration

AltmarkThe ALTMARK Chair has both a reclined and upright mode which makes it interesting and ahead of the market.   The webpage shows a fixed intermediate  position in both the reclined and semi upright modes.    At best it gives no biomechanic advantage and was probably intended to add comfort → .   Misled by ” that treacherous guide  which only turns up truthfully when the ergonomics are fully correct”.   If this mode becomes a part of the unstable intermediate mode it allows a faster transition and also gives the user the choice for dynamic motion and rehabilitation.  A win-win.   Scrapping a fixed intermediate mode reduces manufacturing costs. A win-win-win!

Return to  ☛ 2T CONCEPT a full solution     or


The 2Tilt RECLINED MODE for fully safe sitting.

sitting safely reclined modeOnly a 2Tilt reclined mode addresses all the described adverse effects of prolonged sitting.   This has to be correctly configured and begs further prerequisites for a truly practical work chair.

The adverse  factors to be remediated by the 2T reclined mode.

(These have already been mentioned in the post The 2TILT [2T} CONCEPT‘.)    Screen Shot 2016-03-13 at 15.11.47Screen Shot 2018-12-04 at 18.26.57These adverse biomechanical factors  have to be addressed to ensure a sitting position that is the least likely to perpetuate, or result in, LBP and other symptoms.   The obvious, and perhaps only, solution was for prolonged work to be performed in a chair that has a stable reclined mode in a correctly supported supine reclined position.Screen Shot 2015-12-22 at 15.18.35

Reclined mode

Shell1 A semi reclined chair, suitable for office work, can be designed.  However the basic, reclined, solution concept begged further prerequisites which have to be addressed for a truly practical work chair.

  •  The diagram below (Okamura research,) shows how force between torso and seat isredistributed to the backrest on moving to the semi-reclined (45°) mode.Okamura research 2014-04-03 at 13.58.16
  • The force acting on the  ischial tuberosities and the seat pan, shown in the ‘upright’ picture, gives axial compression.  This is reduced in the 45° reclined mode and be less at 40° or if approximates closer to that of supine lying.  This is not made clear in these sorts of diagram.   It also shows, unintentionally, the proposed  position for a ‘Butt Pocket’ in the FTS mode.
  • Intra-discal pressure studies show a fourfold increase of pressure in the upright sitting mode over that when lying supine (Nachemson, 1964) and largely confirmed with more technically advanced work (Sato, 1999).   A study by  Wilke, (2001) with a single subject, showed a closer approximation of the standing & mid-upright sitting modes.
  • Screen Shot 2016-03-19 at 13.15.20These assumptions derived from bio-mechanical studies and clinical observation have been validated by pMRI scans (Smith FW,2007) which show that this mode ensures migration  of nuclear material away from dangerous position near the back of the inter-vertebral joint which occurs with upright (90°) sitting . See ☛effects of sitting
  • It is difficult to refute this evidence.
  • Reclined mode configuration

Screen Shot 2016-03-14 at 14.37.02It is important that this should be correct.  If not it can engender discomfort (as can be experienced in a certain dentists chairs) and more important is potentially dangerous.

    • Support is given to the whole length of the body, from head to feet.    Even with the reduced axial loading the lumbar lordosis should be maintained and is best effected by some degree of pelvic (not lumbar) support. This avoids any tendency to backward tilt of the pelvis with stretching of the posterior components.   The support should only be sufficient to avoid lumbar flattening when supine, and should preferably not be adjustable so as to avoid excessive lordosis and wrong positioning.
    • Pressure is distributed widely, mainly for the seat to the Backrest
    • The kyphotic curve  of the thoracic spine is allowed to be exaggerated being  a stable area and fully supported. Included with the upper lumbar joints, it extends,over 14 segments and the slight extra flexion at the upper lumbar joints is allowable.
    • A correctly placed head/neck-rest is required so that the occupant has no need to move the neck to establish a comfortable task-related visual field.  With the pronounced fully supported thoracic curve (kyphosis) the headrest needs to be  forward from the backrest. This involves some neck flexion, over several joints, which is supported and and the weight of the head can be off-loaded to the head-rest if the force of the head-rest is directed to the base of the skull and not the back if the head.  Freedom of easy movement away from the headrest is easy, if so required.
    • In the reclined work position the key board and mouse should rest on or near the lap.  This is an ergonomically correct position for the arms and wrists.
    • Arm-rests are not an essential requirement of the 2T concept but depend on design and usage.
    • The head and leg-lengths are the most variable parts of the human body,  so vertical, axial, adjustment of these is essential in the reclined mode. BACKRESTS. Pelvic support v. Lumbar.
    • For a fully supported position a leg & foot-rest are essential.   In the Okamura solution the chair is lowered so that the heels can rest on the floor or a bar under the desk.  In the early 2Tilt ‘prototype1’→ the leg-rest/ seat / backrest/ headrest configuration remains constant (monocoque) and in the upright mode the legs are astride the leg-rest with the feet on the floor.  This is probably not practical for an office desk and the leg-rest may have to be retracted or folded down.  As far as possible, adjustments should be avoided but the foot-rest position must adjust to leg-length.  A spring foot exercise system is an advantage for exercise of the calf muscles.
    • The calf length leg rest, seen in recliners, should be avoided in a 2T chair as compression of the calf can result in Deep Vein Thrombosis (DVT).  This may be obviated with recliners which have upholstery and when the legs  are in a position at or above the level of the heart.
    • In a reclined mode heat and moisture build-up can be a problem.  Solutions include a mesh construction  or padded slats.


reclined modeA prototype (p5) was constructed, in the MfI Dept of Engineering in Cambridge, to show the practicality of the 2T concept.  This was the simplest form, based on the original monocoque configuration to illustrate angles and construction.The essential requirements were determined and additional requirements were mentioned.  It is possible, and likely, that complications and variations can, and will, be made Photo on 10-08-2012 at 13.16and it is hoped that this study will be a reminder of the essential principles. Students working on this (P5) model found it very comfortable and used it whenever possible. I was amazed to see how they bounced about on what was only a somewhat flimsy prototype.

Screen Shot 2018-11-17 at 17.57.31

About an earlier (P4) prototype, I wrote  ‘I found this reclined position very 2T reclined modecomfortable and  adopted it whenever possible.  There is no tendency to go to sleep!  When viewing the screen I used the head rest but sometimes brought my head slightly forward when typing. Ideally the footrest should be sprung. The thoraco-upper lumber curve could be exaggerated further to allow less flexion at the neck.  The 2T chair in the reclined mode is relevant to users who have unusual spinal configuration.    HAS.  See      ☛ ‘Special needs’→

The ‘Tilt in Space’ v ‘reclined systems’ debate

This largely relates to wheel chair patients with major conditions such as spinal cord injuries,  muscle diseases, cerebral palsy  and head injuries and is hardly relevant to office workstations.  The difference is that the TiS has a fixed seat-to-back angle being monocoque as in my p1-5 prototype versions. Cambridge studies showed this to be easily feasible although I prefer the leg-rest retracted in the upright mode unless used in a desk-less system.  The reclined systems mode is achieved by opening up the seat-to-back angle and is claimed to increase shear, discussed by Lange, M. L. 2000.



Next ☛2Tilt concept, the UPRIGHT MODE. →


Screen Shot 2018-10-20 at 15.25.04Office work-stations are easily derived from the 2Tilt chair concept. Now renamed the ‘Quadri-Modal’  (4M)  concept as a sit/stand component is incorporated.   In a few decades a chair set before a desk, arranged in straight lines will be perceived as not only dated but hopelessly inefficient. There is an increasing interest in this direction.
 See Mindjet

“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., then there is once more a blank page to draw on.”                             P.Bessey

The 2T concept is particularly relevant to the development of a desk-less office chair, described here as the ‘Quadri-Modal’  (4M)  concept.  So called as the concept has 4 modes with the addition of an easy ‘stand’ option.   The AVANTAGES are :-

  • IfM 2013Freed from the constraints of a desk, the reclamation can be greater, even bringing the feet up to the level of the heart resulting in maximum physiologic and bio-mechanic benefits.
  • The addition of a Sit/Stand function provides additional movement and social benefits.
  • The footprint is smaller than a chair/desk combination.
  • Units can be easily moved about & around.
  • It can provide a ‘break-out’ or nap function.
  • A 4M workstation will be particularly relevant to gaming and the coming AI & MR developments.
  • It excited comments “Gee!    That’s cool.  I want it.”
  • (Yes! That’s John Gorman glowering in the background of the Cambridge picture.)

The 4 modes

  1. Reclined for prolonged use→
  2. Upright for some short tasks→
  3. Unstable intermediate mode→
  4. A standing mode→

See   ☛ https://www.magiclege

For another idea for a deskless office see ☛  Co.Exist→

AltmarkThe Altmark station.  Considered further under ☛ WORKCHAIRS, a new breed with a reclined mode.    Seems to be approaching the 4M concept with reservations.

Screen Shot 2014-02-14 at 17.42.47A reclined chair from America.   With some added work facilities.  Hardly an Office chair.



Screen Shot 2016-06-24 at 12.34.17Ergoquest.   A good idea that I have been advocating since 1998, but a terrible design!   Electrically operated.  With all possible bells and whistles It represents an almost opposite view to the 2T principle and it’s 4M workstation derivative.   This  with an emphasis on anatomy and spinal biomechanics leads to lack of adjustments and simplicity.  Obviously a huge misplaced engineering enterprise without awareness of what was possible and desirable.  Price: $5995

Steelcase Cyps036SteelcaseThe Brody Worklounge.  The illustrations suggest a system that approaches the 4M concept.     It lacks the simplicity of the 4M and does not offer a Sit/Stand capability.   The accompanying diagram shows good design, as far as it goes. It looks familiar!  It differs from the 2T/4M concept which provide some learning points which are more relevant to the 3M concept..

Screen Shot 2016-06-13 at 17.47.21

  • The footprint is larger than an integrated 4M workstation.
  • It looks very constrainiing for the user.  A big No! No!
  • position of the arms and wrist on the tilted keyboard which is well placed.
  • ‘The technology is placed at eye level’.   Of course!  But the keyboard is not.
  • Certainly a step towards the 4M workstation.  So welcome!

Screen Shot 2018-09-06 at 17.24.30A similar recent contribution is useful for illustrating faults

  • It looks very constrained
  • The back-rest is incorrect   See ☛ BACKRESTS. Pelvic support v. Lumbar.
  • There is no in-built movement  See ☛ EXERCISE & movement
  • The chair is not designed to be easily moved
  • A certain amount of pushing and shoving may be needed to quit the chair.

Perhaps I am being unfair as I have not seen an actual model.  I think it is being offered as a ‘break-out’ chair.


Stand mode

Freed from the constraint of a worktop desk, a stand mode can be easily designed.  This may help staff to move about and relate to others.

Ergo sit:standFor a 4M the display and small worktop has to be adjusted for height and swung out for the user standing beside the chair or with a colleague.

Shown is an Ergotron 97-581-019 Worksurface.



‘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.


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, becoming an office work-station.  A sleep hood can be incorporated into the design and avoid the neccesity for a dedicated ‘nap-room’.

Healthy officePoor ergonomics are only a part, albeit an important part, in accounting for the high stress levels in the modern office environment which results in absenteeism and morbidity.   The identified physiological stressors can be identified and easily corrected with increased productivity.  See Ergonomics and office stress.


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”.

Eliott Myers from Roto VR, which is a small, innovative firm with designs on the related accessories market 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! and should be relevant to 2T or 4M design.  Another ‘blank page to draw on’.



←Return to  ☛ 2T CONCEPT a full solution



Recapitulation. The bio-mechanics.

  • IV discs prolapse occurred more frequently when the vertebral segments were wedged to simulate extreme forward bending of the spine (Adams and Hutton, 1982) in addition to when loading is repetitive or when exposed to compressive forces while in a flexed posture.   See ☛ IV Dscs
  • Lordosis occurs at two levels of the human spine, cervical and lumbar.  The spinal joints subject to internal derangement are the 4th, 6th  & 7th cervical and the 4th & 5th lumbar” (Cyriax JH. 1946).
  • Both these spinal levels are where mobile segments meet a solid mass, the skull and the pelvis, and where mechanical spinal pathology mostly occurs (Harrison DD 1998)and differences are found when comparing LBP patients with healthy patients (Jackson RP, 1994).
  • Approximately two-thirds of total lumbar lordosis occurs at the inferior two segments (L4-L5-S1) (Kamali, 2003).
  • This configuration occurred as a result of hominins adopting an upright (orthograde) stance for efficient bipedalism (see pages on  Paleo-anthropology).
  • The lordotic configuration involves a large wedge angle (16-24° at L5/S1) at the lower lumbar joints.  The point of the wedge lies posterior. (See ‘Angles & Lordosis)
  • The wedge angle reduces any tendency for retropulsion of the disc contents.
  • Retropulsion can lead to impingement on pain sensitive structures ( ) and protrusion and extrusion of disc contents.
  • Retropulsion occurs on axial loading with joint flexion (See ‘Effects on sitting posture).
  • The wedge angle is reduced when the pelvis is tilted backwards which occurs with upright sitting.
  • This adverse effect is augmented by reduction of the hip flexion angle (occurs with a seat parallel to the floor) and pelvic support set too high.
  • A large wedge angle is protective and occurs in people with a low incidence of LBP and where there is no tendency for reversal of the angle (ie. to go to 0° or below).
  • Retropulsion is corrected (reduced) in a reclined position or with hip extension (Smith 2006).
  • Excessive extension (lordosis) transfers pressure to the posterior pain sensitive structures.  In moderation this is not evident clinically in the lumbar joints (but is in the cervical region).
  • Movement to ensure intra-discal pressure changes is essential to provide dis nutrition (See Disc nutrition’).


  • Ligaments limit joint movement in a specific direction and provide stabilisation (See Anatomy/ligaments ).
  • Ligaments are visco-elastic and can be lengthened by excessive, prolonged stretching.
  • Excessive joint range and instability can lead to CTD (Solomonow 2003).
  • Excessive joint range can disable the normal protective action of muscles (See Anatomy/muscles).
  • Adams et al. (1980) showed that the supraspinous-interspinous ligaments segments are the first ligamentous tissues to become stressed with forward bending of the lumbar spine.     Ligaments appear to require long periods of time to regain structural integrity, and compensatory muscle activities are recruited (Solomonow et al., 1998; Stubbs et al., 1998; Gedalia et al., 1999; Solomonow et al., 2000; Wang et al., 2000). The time needed for recovery can easily exceed the typical work-rest cycles observed in industry.   See ☛Ligaments


  • Muscle cocontraction, can substantially increase the mechanical loads (compression, shear, or torsion) or change the nature of the loads placed on the body’s articulations during an exertion or motion.   See ☛ Muscles→
  • Neurological pathways.   Pain pathways have been identified for joint pain, pain of disc origin, longitudinal ligaments, and mechanisms for sciatica.   See ☛ neurology→


Requirements for optimising the bio-mechanics of prolonged sitting.

Reduction of axial loading→

Preserve the lumbar lordosis→

avoid backward tilting of the pelvis→

Ensure disc nutrition by pressure changes with movement→


Requirements for optimising the bio-mechanics of prolonged sitting.

Combined these can be difficult to achieve, for office and home, but can be done using the 2 Tilt concept→.

Systems in use at present, partial remediation

See Origins of lumbar vulnerability (Paleoanthropology)→




Special Needs

 People with ‘special needs’ are universal and these needs require to be addressed,  particularly in a reclined mode.


The 2T concept (2T CONCEPT a full solution→) is intended for office use or in the home for those who spend much time working or gaming or just browsing.  The concept also has a number of medical /hospital uses.  I was advised in Cambridge to keep these under wraps as they might subtract from the perception of it’s more general use.   However people with ‘special needs’ are universal and their needs require to be addressed  particularly in a reclined mode.

This occurred to me after talking to an academic ex-orthopaedic surgeon.  I wrote

“Dear Chris

I have been thinking about your comment on patients and realised that it referred to potential surgical cases and those with deformity of whatever cause.  I think this adds a new dimension to the 2T concept under the heading ‘Special Needs’.

I would propose that a patient would have a shell moulded for the torso that would then be mounted on a suitable version of a 2T chair instead of the standard shell.  This addresses the axial compression and pelvic tilt in the reclined mode.  In the upright mode the backrest stand away from the torso with a Forward Tilted seat and so becomes irrelevant.  But support might be needed and then we would have to think about Gorman’s Iliac version.  This is already built into the standard backrest shell, in a reduced form.

The ‘CC Chair’ perhaps?”

Plaster-of-Paris’ (POP) casts are commonly made in orthopaedic and physio departments and can be used to form a shell for the individual from fibreglass or other material at no great expense.   3D printing could be relevant.

In relation to the 2T concept,  see ‘Execise & movement→

Early 2Tilt chair CONCEPT and criticism

A continuation of the comments in the PROLOGUE.

2T early 2014-04-03 at 14.23.15  For a copy of the above, that is easier to read,

Screen Shot 2018-06-09 at 20.43.16

To postulate a hypothesis for limiting LBP on prolonged sitting existing background scientific knowledge of spinal pathology and bio-mechanics, in combination with clinical experience, arguing from cause to effect,  was easily achieved and resulted in the 2T concept which is shown above.  Conventionally this would need to be confirmed or falsified by experiment, in this case by field trials.   With no commercial chair models available this was not possible, to date.  Subsequently a different approach has emerged, closer to ‘inverse probability’ of ‘Bayes Theorem’.  The process is reversed, watching the effects to determine the cause.  In this instance later research has confirmed the original assumptions with a complete theoretical confirmation by pMRI sudies.

Screen Shot 2017-05-22 at 17.22.25The original 2T model has remained intact except that the transition from reclined to upright conferring physiological advantages and has becomr recognised as a mode in its own right,    The bi-modal, 2T concept  becoming a tri-modal (3M) concept.    The desk-less workstation version, allowing a ‘standing’ mode became a 4 mode concept (4M).  ☛work station→ .

Screen Shot 2016-03-14 at 16.24.17Interestingly the prototype1 shown was a desk-less version.  In time this has become recognised as a ‘Workstation’, with no help from me.    At that time IT components were clunky.   The advances in IT hardware now make a desklessworkstation an obvious solution and has added advantages.    I am now (2015) returning to this as a Tri-Modal (3M) concept with an additional Sit/Stand mode, transforming the 2T to 4M. WORKCHAIRS, a new breed with a reclined mode.

An upright chair at a desk may become to look decidedly retro-.   

The concept has not changed since then. Additional evidence has accrued along the way and perceptions have progressed to become more supportive.

Screen Shot 2015-12-10 at 14.52.29Concept Evolution.

Orginally it was met with blank incomprehension!  At first sight, it seemed odd that the office
worker of the near future would be lying in work chairs in a reclined position for some, or most, of the time while using a computer and was regarded as a ‘paradigm shift’.  In the next 17 years I have noticed a softening of this incomprehension and an adoption of at least some new ideas.  Now, in 2015, a chair is proposed, the Altmark,(☛Some chairs→ )that has at least an upright and reclined work position.    This work, I hope, shows the evolution of thinking from early to later work in relation to sitting and chair design, commonly designated ‘ergonomics’. Although intended as a medico-scientific study it started with the experience of patients and I have included their interests.   Patient input and clinical observation is dismissed by scientists as ‘merely’ anecdotal’.   However, with several decades of seeing patients with backache, I make no excuse for including some insights as the start of the scientific process which proceeds to systematic analysis, experimentation and efforts towards falsification.   HAS  

Screen Shot 2013-10-26 at 22.39.09 Examples oh ‘high-end’ office chairs with partial remediation.   For a full remediation see ↓

Screen Shot 2018-10-28 at 12.18.01


  • The only full solution,  The obvious, and perhaps only, solution was for prolonged work to be performed in a chair that has a stable, correctly supported, supine  Reclined mode→

The criticism

I have heard only three precise criticisms of the 2Tilt chair concept.

  • “This is too comfortable. My staff will go to sleep”.
     Although on the P1 prototype (above) with no upholstery, just ply-wood. (Sleep & productivity→)
  • “Female staff will not like lying in their office with legs in the air”.

These are good examples of ‘familiarity bias’ resulting in denial and prejudice for such an unfamiliar concept.

  • “Office managers and CEOs will find the footprint bigger than ordinary office chairs”    The third has substance in that in the reclined mode any reclined chair inevitably has a larger footprint than an upright chair. When not in use the default upright mode of the 2T chair is probably less than most chairs.
  • This becomes irrelevant with the 4M chair.  A workstation has a smaller foot print than a desk/chair combination.
  • A further difficulty has been suggested, arising from CAD studies, relating to the relationship between a 2T chair and a simple, non height adjustable, desk. This is being addressed.  Ditto the above.
  • From leading chair designers  (2015).  “I agree but this concept is ahead of its time.  Familiarity bias will strike in and uptake will be poor.” (see Implications & uptake→ and A new breed of reclined work-chairs→)
  • From an Orthopaedic surgeon“Without clear unarguable scientific evidence that the current models of chair on the market are truly bad and can be proven to produce the backache of which the majority of the population sooner or later develop, current models will continue to be used without supportable criticism of their use. Anecdotes regarding theories of back pain produced by chairs already on the market will not be sufficient to topple the plethora of current chair models recommended for the comfortable ‘ergonomic’ (a term I dislike) seating position.“ . A valid point but ignores the pMRI evidence. This type of global response is often an example of ‘familiarity bias’ (see Implications & uptake)  It may be based on lack of knowledge of recent biomechanical research or occurs in experts who see innovation as a threat and seize on any ambiguities. It is almost impossible to argue effectively with ignorance if it is entrenched with prejudice, as was explained to me in a diplomatic context by an ambassador. However arguments, likely to be put forward by the powerful chair manufacturing lobby, will be cut short if it can be shown by field trials that a 2T work chair fares better in reducing symptoms than any existing chairs.


The argument for limiting footprint is that offices are priced by the area of floorspace. The overall cost (2011, rent, tax, maintenance) of a 11sq ft workstation in the London ‘West End’ is £14,1530 pa. It is less in the City ‘Square Mile, £8,720 and less still out of London being £4,250 in Birmingham. Costs in the City have reduced by 7.3% but risen by 12.5% in the West End (Times, London14/2/20). Obviously managements will have to rethink their strategies to reduce these costs. Limiting workstation footprint is a shortsighted option. It is a false economy to cram work stations into a given space, especially as better layouts become usual and when well designed desk/chair workstations become more universal. Jukes showed that productivity is reduced, by as much as 30%, in a stressful working environment. Costs are increased by low level morbidity, absenteeism and staff turnover. The improved ergonomics removes at least one cause of stress in the office environment and this translates into increased individual productivity leading to reduction in staff numbers and with better layout, increase usable office space. The slightly greater cost of the footprint is more than offset by increased productivity and this is what eventually improves the ‘Bottom Line’.  (See ‘2T & office design’).

This consideration becomes largely obsolete as The 4M concept, with a smaller footprint than a desk/chair workstation becomes mainstream.


 I responded that a nap might benefit productivity and it was unreasonable to keep staff awake with uncomfortable chairs.   I was unaware of the later research.    (see ☛ SLEEP→)

Market and uptake

The 2t concept is a ‘paradigm change’ and will create PR with the large insurance & media interest,   Normalcy biasWith this, uptake is likely to be large and quick.   It could be said that a paradigm change could be equivalent to a potential disaster to a firm if there is a failure to recognise it’s implications .  Chair manufacturers which do not have a 2T model in their range   may react with normalcy bias..”(See Uptake?/Implications?).

Next See the details of the 2T concept  ☛ 2T CONCEPT a full solution


Screen Shot 2016-06-02 at 11.48.52