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Original article
Cumulative mechanical low-back load at work is a determinant of low-back pain
  1. Pieter Coenen1,2,
  2. Idsart Kingma1,2,
  3. Cécile R L Boot2,3,
  4. Paulien M Bongers2,4,
  5. Jaap H van Dieën1,5
  1. 1MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands
  2. 2Body@Work, Research Center on Physical Activity, Work and Health, The Netherlands
  3. 3Department of Public and Occupational Health, EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands
  4. 4TNO Healthy Living, Hoofddorp, The Netherlands
  5. 5King Abdulaziz University, Jeddah, Saudi Arabia
  1. Correspondence to Professor Jaap H van Dieën, Faculty of Human Movement Sciences, van der Boechorststraat 9, Amsterdam 1081 BT, The Netherlands; j.vandieen{at}fbw.vu.nl

Abstract

Objectives Reported associations of physical exposures during work (eg, lifting, trunk flexion or rotation) and low-back pain (LBP) are rather inconsistent. Mechanical back loads (eg, moments on the low back) as a result of exposure to abovementioned risk factors have been suggested to be important as such loads provide a more direct relationship with tissue failure and thus LBP. Since information on the effect of such load metrics with LBP is lacking yet, we aimed to assess this effect in a prospective study.

Methods Of 1131 workers, categorised into 19 groups, LBP was prospectively assessed over 3 years. Video and hand force recordings of 4–5 workers per group (93 in total) were used to estimate mechanical low-back loads (peak load and three cumulative load metrics, ie, linear weighted load, squared weighted load and load weighted to the tenth power) during manual materials handling (MMH) tasks using a video analysis method. These data were combined with static mechanical load estimates based on structured observation of non-MMH tasks. Associations of mechanical loads and LBP were tested using generalised estimating equations.

Results Significant effects on LBP were found for cumulative low-back moments (linear and squared weighted; both p<0.01 and ORs of 3.01 and 3.50, respectively) but not for peak and cumulative moments weighted to the tenth power.

Conclusions Results of this first prospective study on the effect of mechanical low-back load on LBP support a LBP aetiology model of cumulative loads, potentially due to accumulation of microdamage or fatigue. Therefore, prevention of LBP should focus on reducing cumulative low-back loads, especially in highly exposed occupational groups, for example, by reducing handling of heavy loads and working in awkward body postures.

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