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Open Access Research article

Prediction of trapezius muscle activity and shoulder, head, neck, and torso postures during computer use: results of a field study

Jennifer L Bruno Garza12, Belinda HW Eijckelhof345, Maaike A Huysmans345, Peter W Johnson6, Jaap H van Dieen7, Paul J Catalano89, Jeffrey N Katz1101112, Allard J van der Beek345 and Jack T Dennerlein1134*

Author Affiliations

1 Department of Environmental Health, Harvard University, Boston, USA

2 Division of Occupational and Environmental Medicine, UConn Health, Farmington, USA

3 Department of Public and Occupational Health VU University Medical Center, Amsterdam, The Netherlands

4 EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands

5 Body@Work Research Center on Physical Activity, Work and Health, TNO-VU/VUmc, Amsterdam, The Netherlands

6 Department of Environmental Health, University of Washington Seattle, Seattle, USA

7 Faculty of Human Movement Sciences, VU University, Amsterdam, The Netherlands

8 Department of Biostatistics, Harvard School of Public Health Boston, Boston, USA

9 Dana Farber Cancer Institute Boston, Boston, USA

10 Department of Epidemiology, Harvard School of Public Health, Boston, USA

11 Division of Rheumatology, Immunology and Allergy, Brigham and Women’s Hospital, Boston, USA

12 Department of Orthopaedic Surgery, Brigham and Women’s Hospital, Boston, USA

13 Department of Physical Therapy, Bouvé College of Health Sciences, Northeastern University, Boston, USA

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BMC Musculoskeletal Disorders 2014, 15:292  doi:10.1186/1471-2474-15-292

Published: 3 September 2014

Abstract

Background

Due to difficulties in performing direct measurements as an exposure assessment technique, evidence supporting an association between physical exposures such as neck and shoulder muscle activities and postures and musculoskeletal disorders during computer use is limited. Alternative exposure assessment techniques are needed.

Methods

We predicted the median and range of amplitude (90th-10th percentiles) of trapezius muscle activity and the median and range of motion (90th-10th percentiles) of shoulder, head, neck, and torso postures based on two sets of parameters: the distribution of keyboard/mouse/idle activities only (“task-based” predictions), and a comprehensive set of task, questionnaire, workstation, and anthropometric parameters (“expanded model” predictions). We compared the task-based and expanded model predictions based on R2 values, root mean squared (RMS) errors, and relative RMS errors calculated compared to direct measurements.

Results

The expanded model predictions of the median and range of amplitude of trapezius muscle activity had consistently better R2 values (range 0.40-0.55 compared to 0.00-0.06), RMS errors (range 2-3%MVC compared to 3-4%MVC), and relative RMS errors (range 10-14%MVC compared to 16-19%MVC) than the task-based predictions. The expanded model predictions of the median and range of amplitude of postures also had consistently better R2 values (range 0.22-0.58 compared to 0.00-0.35), RMS errors (range 2–14 degrees compared to 3–22 degrees), and relative RMS errors (range 9–21 degrees compared to 13–42 degrees) than the task-based predictions.

Conclusions

The variation in physical exposures across users performing the same task is large, especially in comparison to the variation across tasks. Thus, expanded model predictions of physical exposures during computer use should be used rather than task-based predictions to improve exposure assessment for future epidemiological studies. Clinically, this finding also indicates that computer users will have differences in their physical exposures even when performing the same tasks.