Backache? It does not matter how you sit or on what you sit. What does matter to your spine is how long you sit.
Potential breakdown of spinal components start after 6 hours unless your chair is bio-mechanically friendly to them. This work is intended to explore the bio-mechanical (ergonomic) factors that may determine spinal pathology and lead to backache (Low Back Pain. LBP). And derive some answers.
Sitting on a a log, a tree stump, an old dining room chair or a conventional office chair does not have a great effect on your back. It is on prolonged sitting that the bio-mechanics (ergonomics) affect spinal components. How long? Research suggests six hours or more which is common in the present work environment.
NAVIGATION through the website
For some readers this study was too large and diffuse. It is now divided into subdivisions. NAVIGATION. To use this work → Or see the top menu↑
Specialists will prefer to jump directly to their page of interest using the Right menu→.
Specifically, for general users :-
The effects of sitting
The evidence identifies the adverse factors which occur with conventional prolonged mid-upright sitting. Described under ☛ Biomechanics→. A brief overview is shown here→
Upright sitting resulting in flexion of the lower lumbar joints, results in spinal pathology. These include permanent stretching of the posterior spinal elements and a shift backwards of the IV disc contents towards pain sensitive structures that can account
for common mechanical backache (LBP) and can also lead to serious spinal pathology. The latter has been confirmed by pMRI scans (Smith F, 2007→).
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. Shown here is the Okamura ‘Atlas’ chair. ☛ Atlas→
Other, commonly used partial solutions include ☛ Pelvic support→,
The only full solution is :-
This is the big story derived from examining the bio-mechanical evidence, identifying the factors which can result in spinal breakdown on upright sitting and finally devising a concept for office work-chair design that avoids these adverse factors. The conclusion was theoretical but was later validated and confirmed by a new technology ‘positional MRI’ (pMRI). A fully compliant 2T chair is ergonomically optimised (and optimally comfortable). Anything less should be unacceptable for prolonged use.
The 2T concept addresses all the ergonomic factors that ensure a sitting position that is the least likely to perpetuate, or result in, backache and other spinal conditions. It also includes the necessary requirements to make this a user-friendly practical work-chair. Comfort is also thereby maximised. ☛A Full solution→
- A Reclined mode is the best for prolonged work. ☛The 2T reclined mode→
- A full body support that is configured to the correct spinal shape.
- Reclined mode requires head support that allows for a forward vision field.
- Variability at head and feet only. Avoided elsewhere. Adjustments→.
- Leg/foot support, which can be provided by the floor if the knees can remain extended.
- A 2Tilt Upright Mode (eg. forward tilted seat,) is subsidiary but required for certain short activities and quitting the chair and is the default mode when the chair is unoccupied. ☛2T Upright modes→
The mid ranges should be unstable and easily negotiated ☛Unstable intermediate mode →. This is to avoid the conventional adverse mid-upright sitting posture. It can be used for short periods as a form of exercise ( ☛ dynamic seating→), particularly for rehabilitation following an acute attack of Backache.
This leads on to the 4Modal, 4M work-station.
- Reduced office footprint.
- 2T requirements easier to achieve.
- Easy to move about & around.
- Allows short periods of sleep ( ☛MetroNaps→) 2T in the office and ☛4M work-station→
Concept Evolution of the 2Tilt concept for sitting safely.
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 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. 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 of 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, 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. In the next 17 years I have noticed a softening of this incomprehension and an adoption of at least some new ideas. Now (2016), some 16 years later, 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 ntirely 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→ .
This work, I hope, shows the evolution of thinking from early to later work in relation to sitting and chair design, commonly designated ‘ergonomics’. As it started with the experience of patients 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 as it is the start of the scientific process which proceeds to systematic analysis, experimentation and efforts towards falsification. HAS
Perception & Reality.
Western people have sat in an upright chair since childhood resulting in ‘familiarity bias’. They have been indoctrinated that mid upright sitting is ergonomically ‘correct’. Chair designers have ensured comfort. Therefore it is not surprising that most people perceive this as correct and desirable. It will take time to change this misconceived perception. First chairs designed on bio-mechanically correct lines must be manufactured. Their advantages need to be explained. I have noticed that people who are liable to backache immediately recognise the advantages and are likely to be the first to create a demand. The newer generation is already more open to fresh ideas and also take quickly to a 2T design.. Insurance is already begining to take an interest (personal communication). HAS
- OFFICE STRESS & Backache→
- ☛ Jukes. Managing the Ergonomics →
- ☛ PRODUCTIVITY AND WORKPLACE STRESSORS→ (Article published in EurOhs, European Occupational Health and Safety Journal, Dec 2002.by Dr HA Sanford)
- ☛ The OFFICE 2 Tilt chair →
- ☛ 4M OFFICE WORK-STATION→
- ☛ HAS, on ☛ Office health (& RSI)→ Only a lighthearted account.
- ☛ SLEEP & productivity