What is the background to this ergonomic sitting study?
(pic courtesy of http://www.information-age.com)
In recent years, tablets have become increasingly popular and it has been projected that there will be over 300 million tablets worldwide by 2015. Unlike most laptops, notebooks allow the user to interface directly with the screen which leads to a number of differences in the user’s posture. Several common positions that have been identified include: positioning of the tablet on the lap, holding the tablet and putting the tablet on a desk. The tablets can also be purchased with cases that allow the tablet to be tilted at different angles. Currently, there is very little in the way of guidelines to help ensure people have the right tablet setup to optimise posture and minimise the risk of injury. Therefore, the aim of this research was to better understand how several commonly adopted tablet user positions influence head and neck posture
What did they do?
The ergonomic study took place on 15 healthy subjects whilst they simulated typical tablet tasks on a tablet in a laboratory setting. Two different types of tablets were used, both of which had a case that allowed the user to tilt the tablet. The four different positions used included:
- tablet in the hand on the lap
- tablet on the knee with a case tilt
- tablet on the table with a case tilt
- tablet on a table with a high case tilt ( a position normally used for watching video)
All the outcomes were measured using 3-D motion analysis. Using this system several head and neck angles were measured as well as gaze angle and gaze distance.
What did they find?
Whilst head and neck posture varied across the configurations, it was clear that head and neck flexion angles were greater than those angles previously reported for desktop and notebook use.
Is there any clinical relevance for ergonomic physiotherapists?
Whilst clearly more research is needed within this field, the most obvious take home message is that users may achieve a better head and neck posture if the tablet is positioned higher to avoid low gaze angles (ie positioned on a table than on a lap). Using cases that provide more acute elevation angles is likely to reduce head and neck flexion for tablet viewing, but severe elevations are likely to put the wrist and forearms into abnormal postures for during typing or interaction with the screen.
Where did you find the article?
Source: Young JG, Trudeau M, Odell D, Marinelli K, Dennerlein JT. Touch-screen tablet user configurations and case-supported tilt affect head and neck flexion angles. Work. 2012;41(1):81-91.
This study set out to investigate muscle activity during prolonged sitting in people suffering from low back pain.
What is the background to this study?
In recent years, there has been some ergonomic chair research indicating that some individuals with low back pain tend to exhibit altered muscle activation patterns during prolonged sitting compared to healthy individuals without back pain. Muscles rarely work in isolation and so the authors in the current study compared changes in muscle activation patterns of muscle pairs in the trunk and abdomen during prolonged sitting, in individuals with and without low back pain.
What did they do?
10 healthy subjects were recruited to the study. Each subject was asked to sit for 2 hours. Specifically, participants sat in a chair without backrests and armrests and completed a basic computer task that involved reading text and moving a cursor with a mouse. In order to measure muscle activity, EMG electrodes were attached to the skin overlying the following muscles including: Rectus abdominis, Internal obliques, upper thoracic erector spinae, lumbar erector spinae, latissimus dorsi and the superficial lumbar multifidus. To help understand if any of the subjects were developing pain, the subjects completed a self reported pain scale every 15 minutes.
What did they find?
The results showed that the individuals who developed pain exhibited greater levels of co- contraction in the muscle pairs that increased over the sitting period. Whilst association does not prove causation, it will be interesting to see if this relationship between pain development and muscle co-contraction in certain pairs of muscles is indeed circular (ie one influences the other and vice versa) and whether interventions such as dynamic sitting can alter these patterns.
Where did you get this article from?
Schinkel-Ivy A, Nairn BC, Drake JD. (2013) Investigation of trunk muscle co-contraction and its association with low back pain development during prolonged sitting. J Electromyogr Kinesiol, 2013
Name: The Annual Conference of the Association of Chartered Physiotherapists in Occupational Health and Ergonomics (ACPOHE)
Experience: There are a variety of talks on some of the latest advances in ergonomic research. There is also going to be some Master classes on offer and a poster presentation. Overall, it is a great event and provides an excellent opportunity to learn and network with like minded ergonomic professionals.
Date: 17th-18th May 2013
The first ergonomic Harley Davidson (pic. courtesy Salli Systems)
In 2012 Salli Systems’s announced that they have incorporated an ergonomically designed Saddle Seat into a Harley Davidson motorcycle.
The story began when one of the Salli executives Tiina Roos decided that she wanted to sit in a more upright position whilst on her motorbike.
After incorporating the saddle seat Tiina reported sitting more upright position and feeling less tired after longer drives. The newly configured Harley Davidson looked so impressive that is was displayed at the Hot Rod & Rock show in Finland last year.
Ergonomically designed height adjustable desks have been used in offices for a number of years. Whilst electric desks enable users to get into a more ergonomic working positions, some users don’t always know the best way to adjust their desk. The Salli Autosmart has been designed to overcome these problems.
The Salli Autosmart includes an ergonomic height adjustment system whereby the table can recognise your position and automatically adjust its height according to what you are doing. The height will also automatically change slightly during the day, to accommodate small diurnal changes in spine length. The automated adjustment system is ideal for hot desking and can be used with Salli Saddle stools.
Can ergonomic equipment help?
Work-related upper limb musculoskeletal disorders (WRULDs) are one of the most common occupational disorders reported by workers around the world.
These disorders can affect a number of joints including: the neck, shoulders, elbows forearms, wrists, and hands. The prevalence of these disorders varies a great deal across different professions and can range from anywhere between 12% and 41%. The cost associated with work related upper limb disorders is huge and represents a significant proportion of healthcare costs. It is not surprising therefore that there is a great deal of interest in developing and evaluating interventions designed to treat and prevent these disorders.
The aim of the literature review was to investigate the effects of ergonomic equipment interventions and/or training in the workplace on work related upper limb disorders. Two reviewers searched over 900 potentially relevant references, out of which 13 randomised controlled trials were selected for the study. In total these 13 studies included 2397 participants. The key outcome measurements were the number of people diagnosed with WRULDs, reports of pain or discomfort in the neck or upper limb and the number of days off work due to WRULDs. Some of the studies only had a short follow up (3-8 weeks) however, 7 did have follow up of 6-12 months.
There was moderate evidence to suggest that an upper limb support with an alternative mouse reduced the incidence of neck/shoulder disorders but not the incidence of right upper limb MSDs. There was also some evidence to suggest that compared to normal mice, alternative mice alone did not significantly reduce the incidence of upper limb musculoskeletal disorders. Because of the limited quality of evidence, it is still difficult to make definitive statements about the benefits of ergonomic equipment for work related upper limb disorders. An important next step will be the development of high quality RCTs to further evaluate the effectiveness of these interventions.
Source: Hoe VC, Urquhart DM, Kelsall HL, Sim MR.(2012) Ergonomic design and training for preventing work-related musculoskeletal disorders of the upper limb and neck in adults (Review) Cochrane Database Syst Rev. 2012 Aug 15.
(image courtesy http://www.signwarehouse.com)
As the health problems associated with extended periods of sitting continue to emerge there has been a growing interest in developing interventions to reduce total sitting time. One idea is to hold some meetings in a standing position. So the aim of today`s blog is to outline some top tips for maximising the success of standing meetings.
- Spread the message – for standing meetings to be successful staff members need to understand why they are important and what you are trying to achieve.
- Keep the meeting short – To keep the meetings short you need to have a very clear itinery and ensure you stick to it. We often find appointing someone as a time keeper can keep meetings running to time. It can also be beneficial to use the timekeeper to ensure no single person is dominating the meeting and everyone gets their views heard within the time frame allocated.
- Choose your time wisely: Generally we have found that people respond more favourably to standing meetings in the morning
- Use the right furniture: If your standing meeting requires writing you may need to use a room with standing desks. If you don`t have standing desks you will need to supply clipboards.
What did they find?
Not surprisingly, there was a difference in sitting pressure for males and females. This may be explained by the fact that males and females have differences in the shape of the pelvis and ishial tuberosities.
Interestingly, the use of armrests did not seem to affect female pressure distributions, whilst changing the backrest to the 120 degrees (thigh-angle) did make a small difference to pressure distributions. In the male group there was a significant reduction in pressure distributions when the subjects had use of the armrests. Males also demonstrated a linear reduction in pressure factor values with the increased backrest angle (ie more reclination led to a reduction in interface pressure).
The biggest contributor to changes in seating pressure was the type of chair. Three of the chairs had strikingly lower mean pressure values compared to the other chairs. As you might expect the researchers attempted to identify the key features of these chairs that may have resulted in the reduction in interface pressure. They reported that all three of these chairs included:
- high backrests with shoulder support
- knitted fabrics (as opposed to woven fabrics or tensile mesh)
- adjustable armrests
What were the limitations of the study?
- Individuals were not sitting on the chairs for long and so it is not clear how the interface pressure changes on individual chairs over time
- It is not clear how the chairs were fitted to each user and whether this process was fully standardised
- There was limited information about the chairs to help identify the key features that may have influenced the seating interface pressure
What is the take home message?
This study supports the idea that there are ways of influencing sitting pressure using small changes in posture. Moreover, there is emerging evidence that it may be possible to drastically modify interface pressure through chair design. More research is now needed to carefully manipulate different aspects of chair design to identify the relative contributions of the different features to modifying seat interface pressure.
Ergonomic Chair article reference: Gordon A. Vosa,_, Jerome J. Congletona, J. Steven Moorea, Alfred A. Amendolab, Larry Ringer (2006) Postural versus chair design impacts upon interface pressure. Applied Ergonomics 37 (2006) 619–628