Evaluating the Effectiveness of Estimating Cumulative Loading Using Linear Integration Method
Exposure to cumulative loading is a significant risk factor in the development of musculoskeletal disorders (MSD). To better understand the dose-response relationship, it is critically to quantify the cumulative exposure. Different integration methods have been used in estimating cumulative loading (force or torque). The general objective of the integration methods has been to sum the independently calculated task exposure. Each task was calculated by multiplying the magnitude of the task loading times the task duration which is the “area under the loading curve”. An assumption of this linear integration model is that long-time exposure to low forces will result in a similar level of damage as relatively short time exposure to high forces. To evaluate the effectiveness of this model, three loading groups of eccentric exercise with the same “area under the loading curve” were performed by thirty participants (ten in each group). Maximum isometric voluntary contractions (MIVC) and relaxed elbow angle (REA) were collected before, immediately after, and 2, 4, 8 days after the exercise. The REA and MIVC changes after the eccentric exercise were significantly impacted by the loading group. It suggests that estimating cumulative loading using linear integration method may underestimate the impact of high force loading in terms of cumulative muscle damage.
KeywordsLinear integration Cumulative load Eccentric exercise
The authors wish to thank Chad Abrams and Steve Kisor from RehabWorks for their support during the data collection. Thanks to Aimee Sacks, Heather Murphree, Jackie McCoy, Jean Evans, Joy Shirley, Juan Barnes, Laura Allen, Lurlene Buck from the University Clinic for sharing their expertise and valuable time in this study. This research was supported by the pilot research project from the National Institute for Occupational Safety and Health (NIOSH) Sunshine Education and Research Center.
- 3.Norman R, Wells R, Neumann P, Frank J, Shannon H, Kerr M, Beaton DE, Bombardier C, Ferrier S, Hogg-Johnson S, Mondloch M, Peloso P, Smith J, Stansfeld SA, Tarasuk V, Andrews DM, Dobbyn M, Edmonstone MA, Ingelman JP, Jeans B, McRobbie H, Moore A, Mylett J, Outerbridge G, Woo H (1998) A comparison of peak vs cumulative physical work exposure risk factors for the reporting of low back pain in the automotive industry. Clin Biomech 13:561–573. https://doi.org/10.1016/S0268-0033(98)00020-5CrossRefGoogle Scholar
- 4.Waters T, Yeung S, Genaidy A, Callaghan J, Barriera-Viruet H, Deddens J (2006) Cumulative spinal loading exposure methods for manual material handling tasks. Part 2: methodological issues and applicability for use in epidemiological studies. Theor Issues Ergon Sci 7:131–148. https://doi.org/10.1080/14639220500111392CrossRefGoogle Scholar
- 6.Jäger M, Jordan C, Luttmann A, Laurig W, Dolly Group (2000) Evaluation and assessment of lumbar load during total shifts for occupational manual materials handling jobs within the Dortmund Lumbar Load Study – DOLLY. Int J Ind Ergon 25:553–571. https://doi.org/10.1016/s0169-8141(99)00043-8