Sitting Ergonomics And The Impact on Low Back Pain

Introduction

We all, at some point in our lives, will sit for a long period of time. Whether that is at a desk at work, eating dinner at the table, or sitting to watch a film. Many theories have been produced about how our posture should be during this time. From sitting up straight with no support to using specialised equipment to keep our backs in a correct and safe position. Below will discuss what the evidence says to keep our backs healthy. This page will also aim to cover ergonomics and the basic anatomy of the lower back. The prevalence of low back pain within the work environment (based on UK stats). Discuss different preventive strategies and interventions to reduce low back pain caused by sitting.

Ergonomics

Often referred to as "human factors", ergonomics is the science pf applying physical and psychological principles within an environment to increase both one's productivity and well-being. The study of ergonomics can be divided into three main areas of research:

1. 1. Physical ergonomics
2. 2. Cognitive ergonomics
3. 3. Organisational ergonomics

Physical ergonomics places a greater emphasis on human anatomy, physiology and biomechanical factors influencing one's movements patterns and posture. This area of ergonomics is therefore of significant interest to physiotherapists and one in which they regularly address due to having a rich, in depth understanding and knowledge of these factors.

Statistics in Britain

Research by Dul and Neuman, (2009) stated that ergonomics are important because they improve workplace performance. Ergonomics are an important consideration both when working from home and it the workplace.

Health and Safety Executive, (2019) complete a Health and safety at work Summary statistics for Great Britain 2019. Within this report the MSK disorders (2018/2019) are displayed and 40% of all MSK disorders are related to the back, while this does not break down in to specifics of the lower back it is clear there is an issue around work related ergonomics and the back. it suggests that the high occurance is due to awkward or tiring positions, keyboard work (desk sitting), repetitive actions and poor manual handling.

The Lower Back

A little introduction to the back - what we use/ how we use our backs every day - important to keep healthy... again quite simple

Clinically relevant anatomy

The lumbar spine, where most back pains occur (REFERENCE), has 5 vertebrae (numbered L1-L5). In between each vertebra, there is an intervertebral disc. This is known as the intervertebral disc joint. There are also two (left and right) facet joints between each vertebra (REFERENCE).

The vertebra

There are several distinct features of the typical lumbar vertebra. These include:

• Large vertebral body
• Short and thick spinous process
• Relatively vertical facet joint
• A mammillary process on the posterior aspect of the superior articular process
• L5 has the largest body and transverse process of all vertebra.

Structural function

The main function of the lumbar spine if to bear the weight of the body. It absorbs the stress of lifting and carrying objects as well as general movement.

https://mayfieldclinic.com/pe-anatspine.htm

• The spine holds an increasing amount of weight as you move down into the lumbar region, for this reason, the lumbar vertebra has the larger bodies in the spine.
• Due to the relative size of the spinous process and body, the lumbar spine has the largest degree of extension.
• The lumbar spine allows flexion, extension, and lateral flexion but not rotation and this is due to the orientation of the facet joints
• The mammillary processes provide an attachment point for many lower back muscles.

The intervertebral Disc

Between each vertebra, there is an intervertebral disc. The intervertebral disc is made out of the nucleus pulposus, annulus fibrosis, and the cartilage endplates.

Nucleus pulposus - This is a highly hydrophilic substance that is located in the centre of the intervertebral disc. It acts as a shock absorber as it allows for the distribution of pressure in all directions.

Annulus fibrosis - This contains multiple fibrocartilaginous bands. It surrounds the nucleus pulposus and its main function is to protect the nucleus pulposus.

Cartilage endplates - This is found on the superior and inferior ends of the disc and represents the anatomic limit of the disc. Its main functions include protecting the contents of the disc and providing a source of nutrition to the disc. - https://www.sciencedirect.com/science/article/pii/S0004951414606206

Ligaments

The main ligaments of the lumbar spine include:

Anterior longitudinal ligament - This is a thick band of tissue that runs along the anterior surfaces of the vertebral bodies. It protects against hyperextension of the spine.

Posterior longitudinal ligament - This is thinner than its anterior counterpart and runs along the anterior wall of the vertebral canal. It is involved in preventing disc prolapse.

Ligamentum flavum - This runs between each consecutive laminae and is extremely elastic. Its function is to help maintain an upright posture and to resume this position after flexion. It also prevents buckling of the ligament during extension.

Interspinous ligaments - This connects consecutive spinous processes together within the spine. It mainly limits the flexion of the spine.

Supraspinous ligament - Connects the ends of each spinous process together. Helps to prevent hyperflexion

Iliolumbar ligaments - This consists of two parts, an anterior and posterior part. It plays a huge role in the stability and restricts both side flexion and rotational movement at the lumbosacral junction

Muscles of the trunk - is this right?

Flexors - external oblique, internal oblique, psoas major, psoas minor and rectus abdominis

Extensors - erector spinae, Latissimus dorsi

Lateral rotators - internal obliques, external obliques, and quadratus lumborum

Rotators - external obliques and internal obliques

Low Back Pain

Low back pain can be defined as pain originating in the low back region that may or may not radiate down into the legs. This pain can further be categorised by sensation such as dull or sharp pain as well as duration:

• Acute ( <6 weeks )
• Sub-acute ( 6-12 weeks )
• Chronic ( >12 weeks )

Low back pain is an extremely common disorder with a mean point prevalence rate of 18.1%. Furthermore, 38.1% of these individual's will suffer from low back pain for up to a year. This presents a vast array of knock on effects with the most notable being that on the UK economy. It is estimated that low back pain costs £1623 million annually via direct healthcare related costs and indirectly £10668 million through avenues such informal care and loss of productivity. This is partly due to 15.5% of all employed low back pain suffers requiring absence from work at some point and for varying sustained periods.

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Throughout the literature, there is conflict addressing whether or not sitting is casual of low back pain and if so, whether it amplifies already existing symptoms. Roffey et al. (2010) carried out a systematic review exploring the casual relationship between occupational sitting and low back pain and found there was low quality, inconsistent evidence to suggest that low back pain was bought about as a direct result of sitting. Furthermore, Tissot, Messing and Stock (2009) found that those who had a more sitting based occupation had no increased likelihood of developing low back pain over those who were stood up at work. Instead, the authors noted that low back pain was strongly associated with lack of freedom from constrained, prolonged positions either stood or sitting. This is further supported by Womersley and May (2006) who discovered that those who maintained longer uninterrupted sitting periods in greater degrees of spinal flexion were more likely to suffer backache.

Aside from this, is simply sitting, for any duration detrimental for low back pain. Callaghan and McGill (2001) began to explore this and found that during sitting, lumbar extensor muscle activity increased more than standing whilst in an attempt to maintain an upright position. The authors then proceeded to note this increase in muscle activity could be influencing low back related symptoms. On the other hand, Huang et al. (2016) examined increased compression forces on L3-L4 and L4-L5 intervertebral joints in sitting in comparison to standing with these compression forces increasing when the individual was in a more slumped position or cross-legged.

What is a good sitting posture?

government guidelines?

pictures of different sitting postures...

studies to back up what is a good posture or is it changing your posture so you're not sitting for long period of time - like what should we be doing originally to keep good posture - does this reduce low back pain?

now more than ever this is important?

Prevention of low back pain due to sitting posture

Movement for prevention and rehabilitation of sitting related low back pain

Various interventions are used across the spectrum of occupational settings in an attempt to both minimise the risk of low back pain arising but also reduce the impact of sitting on those with already existent low back pain. However, the utility and effectiveness of these interventions is somewhat mixed within the literature. The main source of evidence regarding these interventions comes in the form of a Cochrane systematic review by Parry et al. (2019) who, after exploring research surrounding the use of such interventions as sit-stand workstations, treadmill workstations and activity trackers, found the effectiveness of these interventions in reducing both the intensity and presence of low back pain for sitting based individuals at work was poor. Another movement based intervention not included within the Cochrane systematic review involves the use of "dynamic sitting" which involves the used of both active and passive implements to encourage regular movement of the trunk and lower extremities in a seated position. O'Sullivan et al. (2012) investigated the effectiveness of dynamic sitting via a systematic review. They concluded that although the evidence regarding this topic was of high quality, there was inconsistent results to support and recommend the use of said intervention.

The primary movement-based intervention that the literature appears to moderately support is the implementation of movement breaks throughout the day for those individuals who are in a seated position for prolonged periods of time such as office workers. Waongenngarm, Areerak and Janwantanakul (2018) carried out a systematic review evaluating "movement schedules" with work durations ranging from 5 minutes to 2 hours and breaks lasting 20 seconds to 30 minutes. They found low-quality evidence supporting both a reduction in pain and discomfort for those carrying out movement breaks which also included simple changes in postural position with detriment on productivity. This is further supported by a later study by Sheahan, Diesbourg and Fischer (2016) who also found that even short, regular breaks of standing from a seated position reduced both the regularly and intensity of acute low back pain within a office worker population.

Use of equipment for prevention and management

With back pain being such a common issue the market has been flooded with equipment to try and alleviate back pain or relieve the symptoms. The equipment ranges from exercise balls and back braces to standing desks which are appearing in offices more and more. Research has been carried out on all the equipment to varing degrees, for example there is minimal research on exercise balls, however, they are used frequently due to them being cheep and easily accessible.

Exercise Ball

There has been a considerable increase in the use of exercise balls as a rehabilitation and exercise tool. Because of the increase in popularity the public eye more people have tried the alternative not only to combat back pain but also to aid concentration while working. However research on how effective exercise balls on back pain is limited and draws mixed conclusions.

Early research by Kingma and Dieën, (2008) investigated static and dynamic posture in females while working at an office computer on a office chair compared to an exercise ball. They measured the effect of sitting on a ball by measuring muscle activity in the spinal muscles. They found that when sitting on the ball compared to the office chair with armrests that there was 33% more trunk motion and in 66% more variation in lumbar muscle activation. However, when sitting on the ball more spinal shrinkage occurred. The research concluded that the advantages may outway the disadvantages and there for there is no real benefit to sitting on a ball as opposed to a supportive office chair.

Elliot et al., 2016 conducted a randomized experimental crossover trial to investigate whether sitting on a ball for 90 minutes/day instead of a chair has an effect on low back pain and core muscle endurance. They found no statistically significant results. They concluded  Ball-sitting had no significant effects on LBP, but did improve core endurance in the sagittal plane.

Back Support Seat Attachment

There is lots of mixed literature on back supports for low back pain. Backrest and seat pan inclination provided no increased trunk activation/reduction in low back pain and actually increased low back pain in specific subgroup - individual’s with extensor related back pain (Curran et al., 2014) this was supported by Ortiz et al., 2020 who investigated back supports for prolonged sitting in cars. Furthermore in relation to back support ergonomic chairs often have them built in for lumbar support and Van Neikerk, Louw and Hillier, (2012) Systematic review shows Inconsistent evidence (moderate quality) to support the effectiveness of ergonomic chairs.

Back Braces

There is little evidence for back braces to be worn when sitting to prevent low back pain and more research needs to be done in to this area.

Standing Desks

It is common belief that standing and moving around are good for your back if you suffer from back pain. Standing desks have grown in popularity for workplaces as an alternative way for their staff to work. There is a complete range in quality with desks for under 500 USD to desks over 1100 USD. however they all have the same fundamental idea which is to be adjustable and allow you to work in a standing posture, but they also can be adjusted back to normal desk height which allows for complete working posture flexibility (sitting or standing)

Standing desks compared to sitting reduced the severity and risk of low back pain (Pillastrini et al., 2010). The study conducted was a longitudinal study which went on for 30 months, following up with the participants at 5, 12 and 30 (months). They had 100 video display terminal workers. However it was only done on 100 workers which limits the generalizability, furthermore it was not only investigating standing desks they also investigated other inventions for back pain therefore we can not say that it was solely standing desks which improved back pain.

Literature which contradicts Pillastrini et al., 2010 was a systematic review that pre dates it by Claus et al., (2008) which found that current studies investigating inter vertebral disk pressure. Sitting unlikely poses a threat to disks that have not degenerated and that sitting is no worse than standing for the incidence of low back pain. They concluded that if sitting is a greater threat for developing low back pain then standing. Therefore it is not because of the inter vertebral disk pressure but rather another mechanism and more research needs to be conducted

Rehabilitation of low back pain caused by sitting

Exercises for low back pain caused by sitting and the rehabilitation of this