- Email: [email protected]
Excerpts from CybErg 1999 discussion on lifting
International Journal of Industrial Ergonomics 31 (2003) 203–205
Technical note
Excerpts from CybErg 1999 discussion on lifting L. Straker* School of Physiotherapy, Curtin University of Technology, GPO Box U1987, Perth WA 6845, Australia
The following comments were posted to the bulletin board that discussed the papers by Burgess–Limerick and Straker on Lifting (see this issue). Two discussion threads are included: one on squat lifting and one on manual handling risk. The contributors’ names and photographs have been removed.
Thread: squat lifting Contributor 1: posted 14 September 1999 11:01 What disadvantages do people see with squat lifting? Contributor 2: posted 16 September 1999 13:00 I think a major consideration, aside from the typical focus on the acute responses of the human body, should be on how practical the technique is. The additional physiological load seems to discourage the use of the squat (as well as obvious problems for large loads). Although anecdotal, I have analysed dozens of manual handling tasks in the US and I do not think I have ever seen a worker use a true squat lift. A great deal of money has been made on posters encouraging this
*Corresponding author. Tel.: +61-8-9266-3634; fax: +61-89266-3636. E-mail address: [email protected] (L. Straker).
technique (Lift Smart, Lift Safely, etc.) and on training seminars, but workers seem to levitate to stoop or semi-squat lifts. Has anyone ever seen a successful implementation of the squat lifting technique? Contributor 1: posted 19 September 1999 02:29 My personal observations agree with yours––the only people I see doing a squat lift at work or home are: (1) people who know you are watching them and you are there to check their lifting technique (so they do know what is supposed to be the ‘correct’ technique––just don’t usually do it) (2) people who have or until very recently have had significant back pain. As you know [2], the published evidence suggests the traditional training can change knowledge, but probably doesn’t change behaviour. Contributor 3: posted 20 September 1999 12:41 Yes, I concur. I’ve had more than 100 subjects through the lab lifting loads for me. I’ve seen one person adopt a full squat––and that was a physiotherapy student who had been taught to lift that way! Other than that, in the real world I have observed a full squat being used by two people who have had lumbar fusions.
0169-8141/03/$ - see front matter r 2003 Published by Elsevier Science B.V. PII: S 0 1 6 9 - 8 1 4 1 ( 0 2 ) 0 0 1 9 8 - 1
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L. Straker / International Journal of Industrial Ergonomics 31 (2003) 203–205
Contributor 4: posted 23 September 1999 18:34 I also have yet to see a client use a true squat lift unless they were being directly observed by someone who instructed them to do this type of lift. Most clients will report that the posture is awkward and they will naturally assume a semisquat or slightly stooped posture. Most clients report that it requires increased muscle effort to try to maintain the squat posture when trying to lift a low load especially for the taller clients. It seems more beneficial to listen to what the client is reporting than to force a particular lift that will in turn be more strenuous on a client. Contributor 5: posted 23 September 1999 20:20 I absolutely agree with the observation of squattechnique ‘‘only under observation’’. But I would like to make a comment from a different point of view: I have had surgery on my right knee (due to sports) about 10 years ago. Ever since squatting is discomforting for me. Well, what do you think which lifting technique I adopted (although being a trained ergonomist)? I use the stooped lifting technique.And just a few days ago I happened to read an article on construction workers that a popular monthly German magazine had published. The worker’s actually mocked themselves about the ‘order’ to lift loads in a squatted posture: ‘‘If we do that, our knees would be ruined within 5 years’’. So my question is, has anybody ever done research what happens to our knees if we would always use the squat-technique? Contributor 1: posted 24 September 1999 03:42 Knee stress is often reported as a problem. A few have tried to quantify it––but modelling the net moments is a bit limited as many of the thigh muscles also go over the hip joint and transfer forces over both joints. Thread: manual handling risk Contributor 1: posted 05 October 1999 02:37 The validity of various criteria for judging manual handling risk (e.g. spinal compression, MAW) is often hotly argued.
I have just had reviews back from a couple of papers where I reported on MAW studies. Several reviewers were of the belief that spinal compression was the only ‘real’ and valid criterion. I noticed the latest issue of ergonomics has an article by Granata and Marras (1999, Vol. 2.9, pp. 1187–1199) which concludes spinal compression has only small predictive validity––pity this article wasn’t out a couple of months ago––it would have made my argument with certain reviewers much easier! However, Granata and Marras’ paper does suffer from using Marras’ low back disorder risk index which is based on one study in one industry––hardly a ‘gold standard’. But it does show the very poor level of evidence we have for any of our risk indicating criteria.
Contributor 1: posted 05 October 1999 02:40 Another paper in the same journal issue (Jorgensen et al., 1999, Ergonomics, Vol. 42.9, pp. 1216–1232) suggests that MAW is not a valid criteria as it is not related strongly to simple biomechanical or gross physiological measures. Whilst this is an interesting paper, it also suffers from the suggestion that these simplistic measures are valid standards to assess risk. It should really be viewed as this murky view is somewhat related to this other murky view!
Contributor 2: posted 05 October 1999 16:25 A ‘‘chicken and egg’’ MMH criteria question? Perhaps the only gold standard is sufficient epidemiological data to support causation. We do not have that for any criteria as far as I know, so most arguments are tenuous. An interesting aspect of MAW and the psychophysical approach is that it was intended to be a job design technique until more objective methods arrived. It really followed traditional job design (e.g., Taylor and the Gilbreths) approaches in the US. This is quite evident in some of Snook and colleagues earlier work. Unfortunately, I do not think the objective methods have arrived.
L. Straker / International Journal of Industrial Ergonomics 31 (2003) 203–205
Contributor 1: posted 06 October 1999 12:55 I am concerned at times at the lack of objective scepticism displayed by some ergonomics researchers! I remember being at an international ergonomics meeting where an eminent researcher presented a biomechanical model without any recognition of the assumptions and compromises that must be made. If the presentation was to a client then it (might) be excusable––but to ones peers who know the simplistic nature of biomechanical models? It seemed the person either didn’t understand the assumptions (? not possible?) or had commercial or personal ego reasons for not acknowledging them. Or is it that we live in an uncertain world and people like to close their eyes to uncertainty to feel more comfortable! Contributor 6: posted 06 October 1999 01:35 A suggestion: How about inviting the prominent people to answer some of these questions on Cyberg––say Chaffin, Norman, Snook, Marras etc. Maybe email them the papers and the comments and see the responses.
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Houston, I chaired a panel entitled ‘‘Future Directions in MMH Research’’. Ayoub, Chaffin and Snook were the panellists. There is a short proceedings paper with their thoughts. Would be interesting to continue and expand the discussions. Contributor 1: posted 07 October 1999 12:33 Good Idea [6]. This is what these symposia are supposed to be about. Maybe Patrick could chair one at next Cyberg on MMH! Ref. [2], how did the HFES discussion see the future of MMH? Contributor 2: posted 11 October 1999 15:33 Ayoub discussed addressing some of the inconsistencies between criteria derived from different domains (biomechanics, physiology, etc.). Chaffin discussed some of the things we need to do in biomechanics, including expanding the inclusion and analysis of motion. Snook feels we need to work on developing job design guidelines for workers with LBP to minimize disability. Some mention of the changing nature of MMH exposures was made. Unfortunately, there does not appear to be an easy answer to the question.
Contributor 2: posted 06 October 1999 16:39 References Perhaps we should take a lesson from the other sciences (e.g., physiology, etc.). Develop a thoery/ method, test it properly, continue if it works, move on if it doesn’t. In MMH, we sometimes get caught up in the methods. RE: Soliciting Experts. Last week at the Human Factors & Ergonomics Society Annual Meeting in
Granata, K., Marras, W., 1999. Relation between spinal load factors and high-risk probability of occupational low back disorders. Ergonomics 42 (9), 1187–1199. Jorgensen, M., Davis, K., Kirking, B., Lewis, K., Marras, W., 1999. Significance of biochanical and physiological variables during the determination of Maximum Acceptable Weight of Lift. Ergonomics 42 (9), 1216–1232.
Technical note
Excerpts from CybErg 1999 discussion on lifting L. Straker* School of Physiotherapy, Curtin University of Technology, GPO Box U1987, Perth WA 6845, Australia
The following comments were posted to the bulletin board that discussed the papers by Burgess–Limerick and Straker on Lifting (see this issue). Two discussion threads are included: one on squat lifting and one on manual handling risk. The contributors’ names and photographs have been removed.
Thread: squat lifting Contributor 1: posted 14 September 1999 11:01 What disadvantages do people see with squat lifting? Contributor 2: posted 16 September 1999 13:00 I think a major consideration, aside from the typical focus on the acute responses of the human body, should be on how practical the technique is. The additional physiological load seems to discourage the use of the squat (as well as obvious problems for large loads). Although anecdotal, I have analysed dozens of manual handling tasks in the US and I do not think I have ever seen a worker use a true squat lift. A great deal of money has been made on posters encouraging this
*Corresponding author. Tel.: +61-8-9266-3634; fax: +61-89266-3636. E-mail address: [email protected] (L. Straker).
technique (Lift Smart, Lift Safely, etc.) and on training seminars, but workers seem to levitate to stoop or semi-squat lifts. Has anyone ever seen a successful implementation of the squat lifting technique? Contributor 1: posted 19 September 1999 02:29 My personal observations agree with yours––the only people I see doing a squat lift at work or home are: (1) people who know you are watching them and you are there to check their lifting technique (so they do know what is supposed to be the ‘correct’ technique––just don’t usually do it) (2) people who have or until very recently have had significant back pain. As you know [2], the published evidence suggests the traditional training can change knowledge, but probably doesn’t change behaviour. Contributor 3: posted 20 September 1999 12:41 Yes, I concur. I’ve had more than 100 subjects through the lab lifting loads for me. I’ve seen one person adopt a full squat––and that was a physiotherapy student who had been taught to lift that way! Other than that, in the real world I have observed a full squat being used by two people who have had lumbar fusions.
0169-8141/03/$ - see front matter r 2003 Published by Elsevier Science B.V. PII: S 0 1 6 9 - 8 1 4 1 ( 0 2 ) 0 0 1 9 8 - 1
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L. Straker / International Journal of Industrial Ergonomics 31 (2003) 203–205
Contributor 4: posted 23 September 1999 18:34 I also have yet to see a client use a true squat lift unless they were being directly observed by someone who instructed them to do this type of lift. Most clients will report that the posture is awkward and they will naturally assume a semisquat or slightly stooped posture. Most clients report that it requires increased muscle effort to try to maintain the squat posture when trying to lift a low load especially for the taller clients. It seems more beneficial to listen to what the client is reporting than to force a particular lift that will in turn be more strenuous on a client. Contributor 5: posted 23 September 1999 20:20 I absolutely agree with the observation of squattechnique ‘‘only under observation’’. But I would like to make a comment from a different point of view: I have had surgery on my right knee (due to sports) about 10 years ago. Ever since squatting is discomforting for me. Well, what do you think which lifting technique I adopted (although being a trained ergonomist)? I use the stooped lifting technique.And just a few days ago I happened to read an article on construction workers that a popular monthly German magazine had published. The worker’s actually mocked themselves about the ‘order’ to lift loads in a squatted posture: ‘‘If we do that, our knees would be ruined within 5 years’’. So my question is, has anybody ever done research what happens to our knees if we would always use the squat-technique? Contributor 1: posted 24 September 1999 03:42 Knee stress is often reported as a problem. A few have tried to quantify it––but modelling the net moments is a bit limited as many of the thigh muscles also go over the hip joint and transfer forces over both joints. Thread: manual handling risk Contributor 1: posted 05 October 1999 02:37 The validity of various criteria for judging manual handling risk (e.g. spinal compression, MAW) is often hotly argued.
I have just had reviews back from a couple of papers where I reported on MAW studies. Several reviewers were of the belief that spinal compression was the only ‘real’ and valid criterion. I noticed the latest issue of ergonomics has an article by Granata and Marras (1999, Vol. 2.9, pp. 1187–1199) which concludes spinal compression has only small predictive validity––pity this article wasn’t out a couple of months ago––it would have made my argument with certain reviewers much easier! However, Granata and Marras’ paper does suffer from using Marras’ low back disorder risk index which is based on one study in one industry––hardly a ‘gold standard’. But it does show the very poor level of evidence we have for any of our risk indicating criteria.
Contributor 1: posted 05 October 1999 02:40 Another paper in the same journal issue (Jorgensen et al., 1999, Ergonomics, Vol. 42.9, pp. 1216–1232) suggests that MAW is not a valid criteria as it is not related strongly to simple biomechanical or gross physiological measures. Whilst this is an interesting paper, it also suffers from the suggestion that these simplistic measures are valid standards to assess risk. It should really be viewed as this murky view is somewhat related to this other murky view!
Contributor 2: posted 05 October 1999 16:25 A ‘‘chicken and egg’’ MMH criteria question? Perhaps the only gold standard is sufficient epidemiological data to support causation. We do not have that for any criteria as far as I know, so most arguments are tenuous. An interesting aspect of MAW and the psychophysical approach is that it was intended to be a job design technique until more objective methods arrived. It really followed traditional job design (e.g., Taylor and the Gilbreths) approaches in the US. This is quite evident in some of Snook and colleagues earlier work. Unfortunately, I do not think the objective methods have arrived.
L. Straker / International Journal of Industrial Ergonomics 31 (2003) 203–205
Contributor 1: posted 06 October 1999 12:55 I am concerned at times at the lack of objective scepticism displayed by some ergonomics researchers! I remember being at an international ergonomics meeting where an eminent researcher presented a biomechanical model without any recognition of the assumptions and compromises that must be made. If the presentation was to a client then it (might) be excusable––but to ones peers who know the simplistic nature of biomechanical models? It seemed the person either didn’t understand the assumptions (? not possible?) or had commercial or personal ego reasons for not acknowledging them. Or is it that we live in an uncertain world and people like to close their eyes to uncertainty to feel more comfortable! Contributor 6: posted 06 October 1999 01:35 A suggestion: How about inviting the prominent people to answer some of these questions on Cyberg––say Chaffin, Norman, Snook, Marras etc. Maybe email them the papers and the comments and see the responses.
205
Houston, I chaired a panel entitled ‘‘Future Directions in MMH Research’’. Ayoub, Chaffin and Snook were the panellists. There is a short proceedings paper with their thoughts. Would be interesting to continue and expand the discussions. Contributor 1: posted 07 October 1999 12:33 Good Idea [6]. This is what these symposia are supposed to be about. Maybe Patrick could chair one at next Cyberg on MMH! Ref. [2], how did the HFES discussion see the future of MMH? Contributor 2: posted 11 October 1999 15:33 Ayoub discussed addressing some of the inconsistencies between criteria derived from different domains (biomechanics, physiology, etc.). Chaffin discussed some of the things we need to do in biomechanics, including expanding the inclusion and analysis of motion. Snook feels we need to work on developing job design guidelines for workers with LBP to minimize disability. Some mention of the changing nature of MMH exposures was made. Unfortunately, there does not appear to be an easy answer to the question.
Contributor 2: posted 06 October 1999 16:39 References Perhaps we should take a lesson from the other sciences (e.g., physiology, etc.). Develop a thoery/ method, test it properly, continue if it works, move on if it doesn’t. In MMH, we sometimes get caught up in the methods. RE: Soliciting Experts. Last week at the Human Factors & Ergonomics Society Annual Meeting in
Granata, K., Marras, W., 1999. Relation between spinal load factors and high-risk probability of occupational low back disorders. Ergonomics 42 (9), 1187–1199. Jorgensen, M., Davis, K., Kirking, B., Lewis, K., Marras, W., 1999. Significance of biochanical and physiological variables during the determination of Maximum Acceptable Weight of Lift. Ergonomics 42 (9), 1216–1232.