Office Workers: The Science of Sitting - When Sit Happens (Part 2 of 3)
In our previous post on 'Office Workers: EOFY Office Workers Under Siege', (8 June) we touched on some of the evidence regarding the perils that prolonged sitting can cause.
We also outlined the effectiveness of 3 strategies:
Getting up and out of your chair to have a small break,
Having an ergonomically designed workstation, and
The impact of stretching and exercising to relieve muscular aches and pains related to sitting.
In this post we will investigate the Science of Sitting, looking into what is required in an ergonomic desk set-up and why this can benefit you.
The main goal when implementing ergonomic changes to a workstation is to keep the body at its most neutral alignment, and thereby its most efficient position. This is in keeping with the very definition of ergonomics: to maximise the efficiency of human interactions with objects and environments.
When it comes to computer work, we've all been guilty of this; starting the task eager, fresh and sitting upright. Then we get into the 'zone' where we become so absorbed in our typing, and without realising it, our bottoms have slid from the back of the seat and our heads drift forward, closer and closer to the computer screen. As we get into this position we begin to lose the natural curve of our lumbar spine (lordosis). Researchers have identified that this is associated with increased low back muscle activity and increased lumbar disc pressures, which can be a cause of low back pain.
Taking pressure off your backside
There is recent evidence to support reducing angle of the back part of the seat to at least 20 degrees compared to the front. This shifts the pressure off our our sit-bones (ischial tuberosity) and more towards the thighs. In doing this our pelvis rotates forward creating a more neutral lumbar spine curve. This then redistributes sitting loads passing through the pelvis and low back, thus reducing muscle activity in the lower back and increasing lumbar spine disc height.
Back to back-rest!
Researchers have identified an interaction between low back pain and a reduced lumbar lordosis. This loss of lordosis has been associated with disc degeneration in the absence of pain. It can also have an adverse effect on spinal ligaments, muscles and joints which may eventuate in a loss of spinal stability.
The next time you sit in your office chair, have a look at the back-rest. They all should have a rounded section which needs to match up to the height of your lumbar spine when you sit with your back against it.
In fact it has been found that sitting without a back support can significantly increase the activity of your back muscles even after an hour!
Give your shoulders some space
A study conducted by Goosens et al 2003 identified that sitting with your shoulders against the back of the seat actually elicits higher back muscle activity. They found that by providing a distance of 6-8cm from the backrest to the shoulder blades allowed for better lumbar support, and a more natural spinal curve which reduces the amount of required lower back muscle activity when sitting.
Resting your forearms
Having your arms by your side, elbows bent to at least 90 degrees and forearms supported has been shown to reduce the amount of muscle activity in the deltoid and upper trapezius muscles compared to unsupported for any given angle of shoulder flexion.
Key Points For an Ergonomic Desk Setup:
Important: These changes are suggestions based on the available literature. If you feel discomfort/pain while attempting any changes to your sitting position, make sure you revert back to your previous setup and book in to see a physiotherapist.
Have your lumbar support match up with your lumbar spine
Where possible (dependent on your chair) reduce the angle of the back part of the seat
Keep hip and knee angles at 90 degrees (use a foot rest if necessary)
Angle back of seat to 10-15 degrees off vertical
Where possible, make sure the top of the backrest is approx 6cm from your shoulder blades
Make sure arms are by your side with 90-100 degrees of elbow flexion
Ensure forearms are supported
Keep screen at arms-length away and 1/3 of the top of the monitor to eye level.
At OccFit Physiotherapy we have extensive knowliedge in the management and prevention of workplace injuries. We travel direct to your workplace to conduct Ergonomic Workplace Assessments as part of our Workplace Physiotherapy services. If you are currently experiencing muscular pain and discomfort, if you have any questions/concerns or if you could benefit from an Ergonomic Workstation Assessment, contact us here.
To find out more about our other physiotherapy services, click here
Stay tuned for our final post on Office Workers where we look into some practical exercises you can do at your desk!
References
Akkarakittichoke N, Janwantanakul P. (2017) Seat Pressure Distribution Characteristics During 1 Hour Sitting in Office Workers With and Without Chronic Low Back Pain. Jum;8 (2):212-219
De Carvalho D, Grondin D, Callaghan J. (2016) The impact of office chair features on lumbar lordosis, intervetebral joint and sacral tilt angles: a radiographic assessment. Ergo Dec23:1-12
Goncalves JS, Moriguchi CS, Takekawa KS, Coury HJ, de Oliveira Sato T. (2017) The effects of forearm support and shoulder posture on upper trapezius and anterior deltoid activity. J Phys Ther Sci. May; 29(5): 793-798.
Goossens RH, Snijders CJ, Roelofs GY, van Buchem F. (2003) Free shoulder space requirements in the design of high backrests. Ergo Apr15;46(5): 518-30
Makhsous M, Lin F, Hendrix RW, Hepler M, Zhang LQ. (2003). Sitting with adjustable ischial and back supports: biomechanical changes. Spine Jun1;28(11):1113-21
Makhsous M, Lin F, Bankard J, Hendrix RW, Hepler M, Press J. (2009) Biomechanical effects of sitting with adjustable ischial and lumbar support on occupational low back pain: evaluation of sitting load and back muscle activity. BMC Musculoskelet Disord. Feb 5:10:17
Pynt J, Mackey MG, Higgs J (2008) Kyphosed seated postures: extending concepts of postural health beyond the office. J Occup Rehabil. Mar;18(1): 35-45
