A million years ago (truly, ask my daughter if I’m that old!) I completed several papers in postgraduate ergonomics, primarily physical and organisational ergonomics rather than cognitive, and for a while there I could recall the NIOSH lifting equation and even discuss biomechanics with some confidence. Sad to say, over the years, my familiarity with those mathematical concepts has rather fallen away, but with an ongoing interest in work and workplaces, I’m still trying to keep up-to-date with the literature on the effectiveness of these interventions.
My frustration with ergonomics grew as I started to realise how limited biomechanical modelling that I used was by comparison with the real work of real people in a real workplace. All of those ‘reals’ add up to messy variables that don’t conform to the assumptions that are needed to avoid hugely complex mathematics. Suffice to say, even with computing power as good as we get today, something’s missing! I think now, of course, that what’s missing is recognition of the variables that are implicated in problems with errors and injury and pain, those messy psychosocial factors.
Anyway, Driessen, Proper, van Tulder and colleagues undertook a comprehensive review of the ergonomic literature – note, not all the ergonomic literature, only physical and organisational ones – and after whittling down the list to include only those that met quite rigorous criteria, wrote a review that was published in Occupational and Environmental Medicine journal very recently. To give some indication of the scale of the job, the initial list of references two reviewers had to wade through had over 3000 papers! And after using the methodological criteria they had chosen, this enormous list shrank to … erm… 10.
Inclusion criteria were as follows:
< The study was an RCT.
< The cohort studied was a non-sick listed working population.
< The intervention met the definition of a physical or organisational ergonomic intervention, that is, the intervention is targeted at changing biomechanical exposure at the workplace or at changing the organisation of work.
< The outcome measure included non-specific LBP or neck pain, incidence/prevalence or intensity of pain.Studies on neck/ shoulder pain were considered as neck pain studies
The exclusion criterion was as follows:
< Individual worker interventions.
The reviewers used the GRADE approach to classify the overall quality of the evidence, and this is briefly described in the article.
Cutting to the chase – what did they find?
“there is low to moderate evidence that ergonomic interventions were no more effective than control interventions on short and long term LBP and neck pain incidence/prevalence, LBP intensity and short term neck pain intensity.”
So, despite the huge investment in time, energy, funding and (often) gadgetry, ergonomic interventions at an organisational level do not have good support.
Does this mean a biomechanical approach is unhelpful? Well, if it’s applied to individuals, possibly not – there is some evidence from return to work literature that modifying work tasks to enable a person with pain to return to work can be helpful.
Most of the time, modifications in this context mean changing the number of movements, reducing the physical demands somewhat by lightening loads in manual handling, or reducing the length of time the person is exposed to the demands. So I think there is some support for biomechanical or physical ergonomic approach for individuals. I also think that if the outcome intended by an ergonomic approach is to reduce or minimise errors, and maximise biomechanical efficiency, then some of the interventions are useful.
But there is a difference between those outcomes, which are useful in industry, don’t forget! and the pain reduction, ‘injury prevention’ outcomes that so often the ‘ergonomic salesperson’ touts (usually accompanied by a special ‘ergonomic’ gadget or piece of equipment).
Critics of this review suggest that some study designs such as quasi-experimental and qualitative designs should have been included. The authors of this paper indicate that previous reviews did include study designs that were suspicious for bias (ie, pre–post trials, prospective cohort studies, controlled trials and quasi-experimental trials) and that the purpose of the RCT is to control for most unforeseen factors. However, interventions conducted in complex environments may be affected by organisational changes, financial problems, lack of management support or other issues and, as a result, study results may be influenced.
They state “In our opinion these factors could hamper evaluation of the potential effects of ergonomic interventions in all types of studies except for those carried out in laboratory settings. These unforeseen factors are in fact an inevitable part of applying ergonomic interventions in real (working) life.”
The authors (and me!) think that a process evaluation should be carried out alongside all ergonomic studies to demonstrate the modifications and fidelity of any real world intervention to the original design. This would help reviewers and readers of such papers to identify how well biasing factors have been managed, and how much the ‘end-users’ of ergonomic interventions have adopted the strategies. In the real world, the make or break of any input is how much the people who are meant to use a new approach actually do so.
Where does this leave me? Well, after a temporary career trying to introduce ‘safe handling’ processes in two busy hospital environments, where I couldn’t put my hand on my heart to say a ‘no lift’ policy would reduce back pain, I am so glad I was both honest enough to say what the outcomes might be (much to the consternation of the management teams in both hospitals!), and sensible enough to ensure that any person returning to work with low back pain had a discussion with me about how to manage their return to work. While the biomechanical approach did not and could not reduce back pain, the individual advice and reassurance that it’s OK to help patients to move using efficient strategies I think helped increase confidence to return to work.
Note to self: don’t bother trying to recall the NIOSH equations, they don’t look like the real thing!
Driessen, M., Proper, K., van Tulder, M., Anema, J., Bongers, P., & van der Beek, A. (2010). The effectiveness of physical and organisational ergonomic interventions on low back pain and neck pain: a systematic review Occupational and Environmental Medicine, 67 (4), 277-285 DOI: 10.1136/oem.2009.047548