Workstation assessments: the risks of sitting too much

Health and safety | July 2018

image showing legs of people sitting in rowWhy is sitting too much a problem?

In the last of 4 articles on taking a biopsychosocial approach, Ergonomics Consultant and experienced physiotherapist, Emma Crumpton, provides the bigger picture on the risks of sitting too much at work.

We have a long-established understanding that sitting is bad for us. As far back as the 1950s, researchers found that London bus drivers were twice as likely to have a heart attack as their more active bus conductor colleagues.

Investigations have continued and sitting too much has been linked with a range of health issues, including increased risk of heart attack, obesity, increased blood pressure, high blood sugar, excess body fat around the waist, abnormal cholesterol levels, and cancer.

Is sitting the new smoking?

You may have read Forbes’ article addressing this very question. This interest was prompted by the finding that sitting for more than six hours a day greatly increases your risk of an early death. They alluded to the concept that some workers have a ‘butts in chairs equals productivity’ mindset.

The World Health Organisation has already identified physical inactivity as the fourth biggest killer on the planet. Sitting too much has been blamed for the epidemic of back pain and musculoskeletal disorders (MSDs) in industrialised countries.

So there is no question: inactivity is dangerous. And yet jobs and work patterns seem to demand that people spend more and more time sitting.

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What happens to our musculoskeletal system when we sit?

woman sitting on swivel chairSitting puts more pressure on your spine than standing. When you sit, the spinal discs are subject to compression forces. Spinal discs are designed to cushion and protect the vertebral joints during movement, and over time the compression force can lead them to degenerate and lose height and flexibilty.

The lack of muscle activity associated with sitting too much can lead to muscle weakness and atrophy. And the toll of sitting too much on your musculoskeletal health is even worse if you’re sitting in a poor posture hunched in front of a computer.

Good posture

Good posture refers to the alignment of your spine with all its adjoining structures. The three natural curves of your spine are supposed to balance along an imaginary vertical line that runs down your body from your head to your feet. This ensures that your spine is neither curved to either side of your body nor altered from its correct curvature.

A person with good posture maintains neutral or correct alignment through all sitting, standing and lying positions. Bad posture in the form of slouching, hunching or slumping creates misalignment along the spine that disrupts the musculoskeletal system.

Examples of bad posture include holding your neck and head forward while working at a computer, or cradling a phone to your ear. These positions can strain the vertebrae in your neck, leading to permanent imbalances, sore shoulders and back. Failing to correct bad posture has significant implications for the skeletal system, causing short term pain and longer term structural damage.

Static muscle activity

Working at a screen, particularly in a bad posture, can be a static activity. This means that the muscles are working, but they are not lengthening and shortening dynamically, and blood is not flowing to bring nutrients and take away waste products. The long term effects of static activity lead to aches and pains and MSK disorders.

During keying tasks, a dynamic load is placed on the muscles in the hands and fingers due to the movement of typing or using the mouse. At the same time, the muscles of the arms, shoulders and neck must remain constantly tense to provide an anchor for the work of the hands.

Static muscle activity and constricted blood flow: a vicious cycle

room full of seated employeesWorking statically in this way over a period of time, particularly if the worker is in a non-neutral / poor posture, they compress the blood vessels that feed the muscles. This restricts the flow of blood in the muscles of the arms, shoulders, neck, hands and fingers. The constricted blood flow reduces the supply of nutrients to the muscles and the removal of acids and other waste products away from the tissues. Reduced blood flow also slows down delivery of oxygen to the muscles. This vicious cycle can only be broken by removing the static load on the muscles, and restoring blood flow.

All this means that tasks requiring employees to maintain the same position for an extended period increase the static loads/forces on muscles and other tissues. The longer postures are maintained, the greater the loading of muscles and other tissues. This increased force contributes to fatigue and muscle-tendon strain. These include using a computer monitor that is above or too far below eye level, and holding a mouse that is located too far away.

What can we do to tackle sitting too much?

The Mayo Clinic suggests that the solution is to sit less and move more – have a look at our 10 tips for building physical activity into your working day. You might start by simply standing rather than sitting whenever you have the chance, and by thinking about ways to walk while you work.

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Contact our ergonomics consultants for expert help

The Department of Health’s 2011 Start Active, Stay Active report recommends breaking up long periods of sitting with “shorter bouts of activity for just one or two minutes”. Whilst it is acknowledged that the evidence base does not provide enough information to set a time limit on sitting, a leading panel of experts who reviewed all the available evidence suggest taking an active break from sitting every 30 minutes.

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