Back Pain Vs The Office Desk 

COVID has meant office workers are spending even more time in a seated position as reduced hours in the office has reduced commuting time. The combination of lockdowns and prolonged sitting has taken a toll on individuals to get motivated to get back in the gym or follow their weekly routined physical activity program and it's our job to get you motivated to stay active.

Here's Why...

It has been estimated that the modern day adult generally spends up to as much as 6 to 8 waking hours or 45-50% of our living day in a seated position (gasp!) (18).

Questions regularly asked questions from us therapists is 'how can our daily habit of staying seated at a desk for long periods affect our body posture and its function in the short and the long term?'

A short answer is; there is a growing causal relationship between prolonged sitting and lower back pain (LBP).

The Science...

A seated posture increases intra-discal pressure and stiffness within the lumbar spine (lower back), reduced strength of our lower back muscles along with a reduced metabolic exchange which can lead to excessive body weight (i.e. we put on weight) (16).

Prolonged Sitting and Lower Back Pain...

More studies are showing that occupations that involve prolonged sitting have a high incidence of LBP and it is not surprising that back and pelvic pain are the most common complaint among office workers.

Because musculoskeletal (MSK) pains related to occupations are common in society, they are also referred to as work related musculoskeletal disorders (WMSDs) . Sedentary work is defined as occasionally lifting no more than ten pounds, and sitting with occasional walking and standing. In occupational science, a static body posture is defined as a posture held for more than four seconds (15).

Various studies have investigated the effect of prolonged sitting, awkward posture and the repetitive motions that we put our bodies on a daily basis related to WMSDs(4). But, there remains various gaps unfilled when it comes to finding a universal solution of how to lessen our joint aches and pains after a day's work sitting in the office.

The link between back pain and prolonged sitting has been attributed to the required adoption of a flexed curvature of the lumbar (lower back) and thoracic (mid back) spines (6).

Body postural demands for seated tasks generally require an upright torso and a moderately flexed lumbosacral (LS) region. Whilst sitting performing deskwork, we tend to adopt a flexed lumbar posture which increases on average by approximately 5 degrees over the course of a working day (figure 1). This may result to ligament laxity via the discs narrowing from a loss of fluid content (2).

McGill and Brown (1992) found that residual creep-stretch within muscles and ligaments remains for a period of time after prolonged lumbar flexion whilst sitting or being in a slumped posture. This study’s main finding was that individuals who spend long periods of time sitting, especially in a slumped posture, and then suddenly go on to perform demanding heavy lifting activities within a short period of time after are at a greater risk of a hyperflexion injury to the disc and ligaments (21).

For example, if a lorry driver, gardener, courier or warehouse shipper/receiver should sit for long hours and all of a sudden requires the activity of unloading a truck full of cargo or heavy boxes, it is strongly recommended to stand, walk, stretch and warm up the lower back muscles first for a few minutes prior to performing demanding manual exertions to avoid unnecessary injury.

Creep is the progressive deformation of a structure within the vertebral column which has been under a constant load over time (26).Creep response in the vertebral column is thought to be caused by the gradual arrangement and increased stress placed on viscoelastic tissues which places a negative effect on collagen fibres, proteoglycans and the water content in the intervertebral discs, spinal ligaments and zygapophyseal joint capsules (26).

The load placing stress on an area within the vertebral column is usually below the level required to cause complete tissue failure. During creep, the segments are usually at their maximum limited range of movement and the spinal column (or segment) will continue to deform in the direction of load (26). Sitting for long periods with a poor posture over several years has its repercussions. A head protruded forward with a kyphotic upper back with rounded shoulders whilst typing or mousing at a desk will encourage both the neck and back to gradually be inclined to reside in this position during a standing posture.

If individuals sustain a flexed lumbar spine posture whilst performing deskwork, the passive flexion stiffness (PFS) of the lumbar spine can reduce over time because of viscoelastic creep or stress-relaxation in the posterior lumbar tissues (3). Increased intervertebral joint laxity with sustained flexion loading can attribute to fluid loss in the intervertebral discs. Reduced PFS can increase the risk of a hyperflexion injury during instances whereby prolonged sitting is followed by tasks that involve full lumbar flexion (3). Beach et al., (2004) concluded that it can only take up to one hour of sitting for PSF to occur and increase the risk of injury if full flexion movements are attempted after.

The amount of axial compression and flexion creep increases with age, but the amount of creep depends upon the magnitude and direction of load application. The vertebral column does and can recover when the load is removed but at different rates. It is no surprise that as we grow older, the rate of recovery is slower and tissues take more time to heal (25). The difference in the loading and unloading of segments in the vertebral column is known as ‘hysteresis” (25).

A small scale study conducted by Oliver and Twomey (1995) suggests that brief periods of sustained extension loading within the lumbar spine during occupational activities, such as painting ceilings or undesired standing postures can cause significant creep to the viscoelastic tissues.

In disc height loss, associated creep in severe cases can lead to altered morphology of the neural foramina where the nerves pass through the holes within vertebrae which can result to nerve impingement. This has been shown in an animal model to initiate pain with nerve root compression. More moderate cases of creep can still create strains in the passive tissues in the intervertebral joint such as the disc or articular capsule sufficient to generate pain from compressive loading.

The term 'if you don't use it, you lose it' applies here, as when we sit for long hours various muscle groups essentially weaken over time and this is clinically very evident during a physical examination.

The study by Snijeders et al., (1995) found that individuals use a small level of oblique abdominal muscle activity when subjects are seated or stood during a stooped posture, but had strong activity when sitting in extreme flexion. They found limited or no activity in the erector spinae, gluteus maximus (buttock) and biceps femoris (hamstring) muscles during erect postural sitting. The activity of the internal obliques was high whilst the external obliques showed moderate activity. In passive sitting on an office chair with a hard seat and a back rest all records showed little or no activity within these muscles, except the internal and external obliques. Reduced oblique abdominal muscle activity tends to occur whilst sitting on a soft car seat compared to sitting on a hard seat of an office chair (28).

Mid Back Mobility

Reduced thoracic mobility has been observed in individuals who spend more than 7 hours a day sitting and performing less than 150 minutes (2 ½ hours) of physical activity each week (17). This study found that there was a reduction of thoracic spine mobility by as much as 10% for individuals who sat for more than 7 hours per day and perform less than the recommended level of physical activity per week (2 ½ hours) (18).

Arm Rests

It is also interesting to note that studies have found arm rests on chairs to reduce the level of actitvity of upper trapezius and neck muscles. A study on dentists found significantly reduced right sided anterior deltoid activity (by 68%) with the use of fixed arm supports whilst they were compared to working without arm supports (4).

Visser et al. (2000) studied the effect of using arm supports in visual display unit work on physical workload. They reported significantly lower levels of upper trapezius muscle activation when typing with the use of arm supports compared to typing with no arm supports.

Good Sitting Posture

Upright sitting (i.e. neutral posture) is associated with high muscle activity, which during prolonged sitting has been associated with muscle fatigue and pain (18). Conversely, slumped kyphotic sitting has been associated with increased spinal load from the body tending to posteriorly tilt the pelvis which is then counterbalanced by excessive contractions of the dorsal spinal muscles (17). Slumped sitting has also been associated with greater head/neck flexion, anterior translation of the head and increased cervical erector spinae muscle activity in comparison with upright sitting (8).

Studies have shown that our bodies respond differently when we are sitting relaxed e.g. at home watching television to sitting at a desk at work and concluded that spinal loading whilst working in a sitting position is higher than spinal loading in a relaxed sitting posture (18, 19).

Patients with chronic lower back pain have been found to demonstrate poorer postural control of the lumbar spine than healthy individuals along with a pelvic asymmetry which creates further changes to soft tissue tightness (1).

During standing, research has shown that compressive loads on the lower back is minimal, however, prolonged static standing has been associated to the reporting of lower back pain and disc height loss (15).

Certain jobs such as cashiers, bank tellers and casino dealers spend a majority of their workday standing. These roles tend to lead the worker adopting awkward postures, reduced trunk motion and increased repetitive upper extremity tasks (15).

Springer (2010) has a rather modern approach with how seating should be with relation to spinal biomechanics by fundamentally asking future ergonomic seating arrangements to consider ‘what should a chair do?’

1.) Support a person’s body as an individual - As explained above, accepting that we all have different body types, shapes and sizes, the design of a chair needs to accommodate the range of individuals who will be using it.

2.) Support activity – When considering task seating, what people do, how they do it and for how long are essential pieces of information. Chairs should support all the activities in which people engage, not just one primary activity.

3.) Promote movement – A chair should promote movement and encourage the natural movements of the body as it provides support. Movement should not require conscious effort. Chairs should move with the user, and make it easy to move (13).

4.) Enable performance – An ergonomic office chair should facilitate, support and enable effective performance.

5.) Be easy to use – adjustments made must be simple and easy to use. Experience shows that the majority of people do not want to have to think about their chair when they are trying to work or activate a control to change its positioning and these controls are seldom used (24).

6.) Do no harm – A chair should not allow for discomfort, stress, pain or injury and should not constrain postures or force positions.

Posture in the field of dentistry has been greatly explored as they are more prone to musculoskeletal (MSK) diseases especially within the cervical and lumbar spines (15). Dental nurses and dentists are a type of health care profession that require a high skill job in awkward sitting positions during clinical activity such as bending their head anteriorly and laterally repetitively over long periods (28).

Various seats have been compared and analysed to find out which is the optimum chair to sit on for long periods whilst we work. There is evidence that the “ideal” ergonomic 90˚ sitting posture (knee angle and hip angle) actually increases the passive tension of hamstring muscles, causing a posterior pelvic rotation and resulting in a kyphotic sitting posture of the lumbar spine.

However, ergonomic recommendations, radiographic studies, and analyses from physical therapist and laypersons indicate that a sitting posture with a slight anterior tilt of the pelvis and lumbar lordosis may reduce the incidence of low back pain most efficiently.

The saddle stool (Figure 2) has been studied amongst the field of dentistry and has conflicting conclusions drawn for its effects on the spine. A study by Gadge and Innes (2007) found that the saddle seat was associated with significantly less lumbar discomfort but associated with more hip/buttock discomfort.

Da Silva et al. (2017) found that a saddle seat seems to promote a healthy posture, regarding maintenance of lumbar lordosis which is otherwise associated with lower disc pressure and suggested that it instead provided less physical workload to the arms and trunk during dental work. The literature does not yet provide a consensus on whether the saddle seat is a superior alternative to the conventional seat for maintaining optimal posture. In the context of the activities undertaken within this study, the standard stool has the least preferable combination of posture and muscle activity. It could be predicted that this type of seating will result in greater risk of lower back symptom reporting amongst dentists.

De Bruyne et al., (2016) compared the effect of using three different stool types on muscle activity and lumbar posture among dentists during certain dental screening tasks and discovered that individuals tended to sit with less lumbar flexion (-6°) than on a standard A-DEC DOCTOR’S STOOL (4°) or Ghopec (1°) stool.Findings also included the Ghopec stool tending to facilitate a less flexed lumbar position compared to the saddle stool which seemed to result in a hyperlordotic posture (9). Another interesting observation was that the presence of a backrest helped reduce the activation of the abdominal muscles and the study concluded that to recommend neutral posture, the Ghopec stool was considered the most suitable of the 3 stools that they investigated.

Another study by Grooten et al., (2013) found that the pelvis tends to be held in a posteriorly tilted position whilst seated on an office chair. They also concluded that the pelvis is in more of an anterior tilted position whilst standing and sitting compared to stable and unstable sitting on a Back App Stool or whilst seated on a saddle stool (16).

Annetts et al., (2012) investigated the effect of four different office chairs (saddle, vari-kneeler, swopper and standard) on the postural angles of the neck and lumbar-pelvic regions. They discovered that no chair seemed to consistently produce an ideal posture across all regions of the spine and they concluded that individuals' needs should be made priority when it comes to chair selection.

As a conclusion, the biomechanics of sitting mainly focuses on measuring the position of the spine, pelvis, muscle contractions, pressure distributions and boney contact on the seat currently being used. In general, there is no universal, ‘correct’ posture or no one “right way” to sit as each individual is different with individual heights, body type and shapes (26). Modern ergonomic research should take different body types into consideration and the nature of working behaviours that people adopt whilst sitting (whilst at work) (29).

Primary focus when patients arrive are placed on posture and overall spinal health, particularly within the neck and upper mid back. Treatment may involve soft tissue and gentle osteopathic joint mobility techniques applied to the sternum, chest, mid back and neck. Breathing techniques and realistic home exercise programs are commonly prescribed with the idea of helping circulation within tired postural muscles.

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29.) Springer, T. (2010) The Future of Ergonomic Office Seating, Knoll, Knoll Workplace Research, pp. 1-10.

30.) Vink, P., Porcar –Seder, R. Page de Pozo, A, Krause, F. (2007) “Office chairs are often not adjusted by end users” Proceedings of The Human factors And Ergonomics Society 51st Annual Meeting. Santa Monica, California: HFES. pg 1015 –1019.