Researchers in the Netherlands conducted a literature review of the ergonomics scientific base (from 1988 through 2008) looking for studies investigating the effectiveness of physical and organizational interventions. In simple terms, their findings are:
- they were only able to identify 10 studies that met their stringent inclusion criteria;
- from those 10 studies,
- there is low to moderate quality evidence that ergonomic interventions are not effective at reducing neck and low back pain incidence/prevalence and short and long term LBP intensity;
- there is low quality evidence that a physical ergonomic intervention was significantly more effective at reducing neck pain intensity in the short and long term;
- the limited number of included studies makes it difficult to reach broad conclusions, and the results should be interpreted with care.
In other words, based on only 10 studies from the past 20+ years, the authors conclude that, in terms of neck and LBP, the evidence that physical and organizational ergonomic interventions do not work is stronger than the evidence that such interventions do work.
The review, authored by Driessen et al, appears in Occupational and Environmental Medicine, and critics have already come forth. In the same issue, Westgaard provides a commentary in response to the review, and Driessen et al respond in turn to Westgaard’s commentary.
Westgaard takes issue with Driessen et al for only including studies that use RCTs. Specifically,
While the aim of attaining the best study design for ergonomic intervention studies is applauded, the above trend raises (at least) two queries: (1) is the RCT design the best attainable to the exclusion of other study designs and (2) is a review process with exclusion of studies that in the limiting case do not approach the RCT standard reasonable (ignoring for the moment that this is a valid specific objective of a review)? Studies with alternative designs, for example, quasiexperimental and qualitative studies, have been largely ignored in occupational medicine journals, which is criticised …
Westgaard makes additional points:
- RCT based study designs were developed to guard against bias in the closed circumstances of testing clinical treatment or medication.
- In contrast, ergonomic intervention studies are usually conducted in dynamic workplace environments where things change, and those changes influence the study variables (i.e., an ability to control variables is lacking).
- The effectiveness of ergonomic interventions are heavily influenced by the way they are introduced (e.g., whether or not employees received training, how thorough/effective that training was, whether or not management supported the interventions, financial difficulties, organizational changes in general, etc.).
- Process evaluation, generally not available in RCT studies, is valuable in post-hoc analysis of ergonomic studies in complex, changing environments.
- With only 10 studies in the review, and only one of those investigating organizational intervention, it is not fair to extend the conclusions to ergonomic interventions in general.
- The interventions investigated in the 10 studies may in themselves have minor effects, but other factors, such as psychosocial exposures that were not included in the study, may have influenced outcomes.
- Subject/Employee compliance with interventions and other confounders in the studies were largely unknown, and could have significant effect on outcomes.
Westgaard calls for a "best evidence" approach "where studies utilising the strengths of different study designs are combined to provide the best overall assessment of ergonomic intervention effects, considering worker exposures, intervention delivery, setting and other relevant contextual factors," rather than a strict RCT requirement. He closes his comments by noting that even though Driessen et al recognize the limitations of their review and caution against generalizing the results, those limitations are often forgotten when referring to the review.
In their response to Westgaard’s comments, Driessen et al state that:
Although we agree that other study designs can add to the existing knowledge on ergonomic interventions, we believe that the RCT is the gold standard for investigating the effectiveness of different interventions untainted by bias.
They suggest that the confounders and challenges inherent to using RCTs in complex environments can be addressed by alternative study designs:
A possible solution to reduce the influences of these factors is to perform cluster randomisation at the level of the workplace (department or working unit). Similarly to individual randomised trials, the cluster randomised trial also minimises the risk of bias. Moreover, by performing a cluster randomisation, contamination between workers in the intervention group and those in the control group is avoided.
Driessen et al strongly support Westgaard’s opinion that ergonomics researchers should perform process evaluations with their studies that help to understand unexpected results, which
… can also shed light on whether the intervention was delivered as intended and resulted in the implementation and use of ergonomic measures (ie, implementation, compliance, satisfactions and experiences) and on the successes and failures of the intervention. We found that implementation of ergonomic measures was poorly reported in ergonomic intervention studies, while the effectiveness of ergonomic interventions is strongly determined by its end-users. To improve compliance, future ergonomic interventions should use an adequate implementation strategy. Furthermore, researchers should improve reporting on compliance.
They close their response by once again cautioning against generalizing the results of their review to the general population:
We agree with Westgaard’s final point that the conclusions of our review have to be interpreted with caution. First of all, we found limited studies per outcome measure and secondly, most studies were conducted in an office setting and study populations consisted of both symptomatic and non-symptomatic workers. Therefore, our results cannot be generalised to the whole population.
There is much more to this review and the debate that follows, and interested readers are encouraged to review the entire review, commentary, and response to commentary, cited below.
The Bottom Line – How This Applies To Ergonomists
The scientific basis for ergonomics as a means to reduce or eliminate workplace MSDs has been under fire for many years. This study and the debate it sparks is representative of a conflict among researchers as to which study designs and methods are most likely to yield unbiased results. Each perspective in the debate has merit, so it’s not easy to dismiss opinions on either side. These types of debates are healthy and serve to spur improvement across the scientific spectrum.
However, without a thorough understanding of the science and the debates it fosters, it’s easy for the public to hear only the sensationalistic sound bites that at first glance would suggest ergonomic interventions don’t work. When politically motivated groups and individuals pick up on the "news," it becomes very difficult to remember, much less explain, that these results should be interpreted with care, and that they cannot be generalised to the whole population.
Any ergonomist who has worked first hand in the field knows that ergonomics interventions can be very successful at reducing the risk of developing MSDs, or at reducing the effects of existing MSDs. Much, however, depends upon how the interventions are implemented, including the specific intervention, training and gaining buy-in from employees, management support, etc. This is where the primary challenges are, and this is where success is made or lost.
This debate also highlights the need for occupational ergonomists to expand their focus beyond MSDs alone. Professional ergonomists bring far more to the workplace than injury prevention and accommodation. Some of the greatest value ergonomists bring is in productivity, quality, job satisfaction, morale, reduced absenteeism and turnover, and more. Rather than focusing our value primarily on risk reduction, we should expand that focus to the many other benefits we create.
The articles reviewed above can be acquired from the copyright holder at: http://oem.bmj.com/content/67/4.toc
Maurice T Driessen, Karin I Proper, Maurits W van Tulder, Johannes R Anema, Paulien M Bongers, Allard J van der Beek, "The effectiveness of physical and organisational ergonomic interventions on low back pain and neck pain: a systematic review," Occup Environ Med 2010 67: 277-285.
Rolf H Westgaard, "RCTs of ergonomic interventions," Occup Environ Med 2010 67: 217-218.
Maurice T Driessen, Johannes R Anema, Karin I Proper, Allard J van der Beek, "Authors’ response: RCTs of ergonomic interventions," Occup Environ Med 2010;67:218–219
This article originally appeared in The Ergonomics Report™ on 2010-07-14.