Why did I bother?
As a consultant in Orthopaedic (Musculo-skeletal) Medicine, patients with backache kept asking me to recommend a work chair. A difficult question to answer as there seemed to be no work chair on the market, in 1998, that would do anything other than make prolonged sitting a recipe for making their backache worse. Most users, with even minor degrees of low lumbar backache, the clinicians who treat them and chair designers who aim to help are aware that prolonged sitting is a major factor in aggravating and perpetuating their symptoms.
A renewed look at the pathology and biomechanics related to mechanical Low Back Pain (LBP, Backache) suggested a logical alternative complete solution which is proposed here. (The 2Tilt concept→). At first sight, it may seem odd that the office worker of the near future will be lying in work chairs in a reclined position for some, or most, of the time while using a computer. This is likely to become universal if vindicated by field trials.
Evolution of the 2Tilt concept for sitting safely.
This work, I hope, shows the evolution of thinking from early to later work in relation to sitting and chair design, commonly designated ‘ergonomics’. 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 as it is the start of the scientific process which proceeds to systematic analysis, experimentation and efforts towards falsification.
So after 50 years, I decided to look afresh at the basic scientific facts of spinal pathology and bio-mechanics and see what emerged. What emerged confirmed the view of the adverse effect of mid-upright sitting described by AC Mandal (☛Mandal→ ) and suggested a logical alternative complete solution which is proposed here. ☛ (The 2Tilt concept→), This was a new approach to chair design aimed to address the adverse bio-mechanic problems of the upright sitting mode used in most modern office and work chairs. This was my view advanced in 1998 ☛ Early 2T concept→.
It was met with derision and blank incomprehension and deemed to be somewhat weird. In the next 17 years I have noticed a softening of this attitude and an adoption of at least some new ideas. Now (2016), some chairs with a reclined work mode are begining to appear in the market. An example is the Altmark,(☛Some chairs→ ) that has at least an upright and reclined work position. Unfortunately it does not seem entirely 2T compliant. See ☛WORKCHAIRS, a new breed with a reclined mode→.
The 2Tilt concept has remained unaltered except for recognition that the unstable transition mode carried a number of physiological advantages and could be considered as a mode in it’s own right, making the concept Trimodal (3M). The desk-less workstation version, allowing a ‘standing’ mode became a 4 mode concept (4M). ☛work station→ .
A quick overview
For the adverse effects that need to be avoided……Consider the effects of mid-upright sitting compared to standing:-
For a more detailed explanation see in BIOMECHANICS that determine safe sitting→
Effects also include permanent stretching of the posterior spinal elements and retropulsion of the disc contents. The latter has been confirmed by pMRI scans (Smith F, 2007→)
The 2 Tilt concept (Also the 3M & 4M concepts)
The bio-mechanical imperatives show that a correctly supported reclined posture addresses the recognised adverse effects and should reduce the incidence of Low Back Pain (LBP) experienced on prolonged sitting. It also ensures maximisation of ‘comfort’. This technical ‘fix’ is required if the increase in personal morbidity, loss of earnings and the huge cost to industry and insurance due to absenteeism and stress due to LBP, is to be halted. The suitability of any chair can be judged (for sitting safely against it (The ☛ complete solution→) . Final scientific evaluation can only be fully validated when models are assessed by controlled field trials against top end existing chairs.
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 →
Systems in use at present, See ☛ Remediation→
- Pelvic support →
- Forward tilted seat →
- Ischial off-load →
- Reclined work mode (Okamura) →
- Dynamic seating→
A full remediation, the 2Tilt Concept, is suggested. See ☛ 2T concept→
Combining these requirements can be difficult to achieve but is possible in a suitably supported reclined mode at 40-45° which conforms to spinal morphology (configuration). This alone is impractical as a work position unless a number of secondary requirements are incorporated to make this simple concept suitable and practical for a work chair.