Body Mass Index Related to Musculoskeletal Discomfort and Job Stress

A team of researchers from the Department of Sports Medicine & Physiotherapy at Guru Nanak Dev University in Punjab India, and from the Department of Psychology at Laxmi Memorial College of Physiotherapy in Mangalore India, performed a study looking at various associations between body mass index (BMI), musculoskeletal discomfort, and occupational stress. The team studied computer workers in India with the objective of seeing if there was any effect of Body Mass Index (BMI) on musculoskeletal discomfort and occupational stress in computer workers.

Body Mass Index, or BMI, is the ratio of weight in kg/cm². The BMI is a simple yet valid screening tool to estimate body composition without requiring expensive instruments or trained individuals. For example, the weights below are the BMI based descriptors for a 5’9” (175 cm) person.

• < 18.5 BMI Underweight (< 124 lbs/ 56 kg)
• 18.5 – 24.9 BMI Normal weight (124 – 168 lbs/ 56 – 76 kg)
• 25.0 – 29.9 Overweight (169 – 202 lbs/ 76 – 92 kg)
• 30.0+ Obese (203 + lbs/ 92 + kg)

Methods

Musculoskeletal discomfort was measured using the Cornell Musculoskeletal Discomfort Questionnaires (CMDQ). The CMDQ allows individuals to report body part discomfort and to qualify that discomfort relative to:

• Frequency of discomfort
• Intensity of discomfort
• Interference with the ability to work

Work stress was measured with the Occupational Stress Index (OSI). The developer describes the OSI as “an additive burden model, which focuses on work stressors relevant to the cardiovascular system and how stress leads to cardiovascular disease, such as features of work in high-risk occupations. The OSI derives more from cognitive ergonomics and brain research, attempting to describe, in quantitative terms, the burden of work processes upon the human being.” The OSI checklist has a number of components including:

1. Role overload
2. Role ambiguity
3. Role conflict
4. Unreasonable group pressure
5. Responsibility for persons
6. Under participation
7. Powerlessness
8. Poor peer relations
9. Intrinsic impoverishment
10. Low status
11. Strenuous working conditions
12. Unprofitability

Participants

100 computer workers, aged 25-35 years, were randomly sampled from software and IT companies in Bangalore India. Participants were screened to exclude anyone with a chronic illness, eye problems, existing musculoskeletal disorders, or anyone who has had major surgery.

Participants were required to undergo an ergonomic analysis of their workstation to ensure that it met the guidelines outlined in the US – OSHA eTool Evaluation Checklist. Each participant was required to have an adjustable chair that met defined ergonomic requirements, they all had 17-inch monitors positioned at eye level, and each was using a keyboard tray. Details of the workstation ergonomics are described in the study, cited below, and interested readers are encouraged to review the full paper (open source).

Participants signed a written consent form and then anonymously completed self-report questionnaires including the BMI, OSI, and CMDQ.

Results

• 60% (N=100) of subjects were in the oldest subset; 31-35 years of age.
• 64% of subjects were in the 25.0 – 29.9 Overweight BMI category
• No subjects were in the 30.0+ Obese category
• The subjects with the highest BMI had the highest discomfort scores (significant at the p<0.001 level)
• The subjects with the highest BMI also had the highest Occupational Stress scores (significant at the p<0.001 level)
• Together, these results suggest that the Overweight BMI group perceives a high level of work-related musculoskeletal discomfort and occupational stress.
• A multivariate analysis shows that as BMI increases the CMDQ significantly increases (p<0.001), and the OSI score also increases (p<0.001).
• The BMI is also shown to predict OSI subcomponents of Role Overload, Unreasonable Group Pressure, Responsibility, and Strenuous Working Conditions, but not other subcomponents.

What Does this Mean?
This study demonstrates that BMI/overweight is associated with increased discomfort and stress, which may contribute to increased risk of injury. These results align with other studies showing an association between excess weight and chronic illnesses and musculoskeletal disorders. For example, according to the National Medical Spending Attributable To Overweight And Obesity report (cited below), overweight Americans spend 14% more on medical care, while obese Americans spent 37% more than their normal weight peers. Ergonomists typically focus their efforts on the physical, organizational and cognitive features of a human-system interface — a computer workstation, in this case — looking for risk factors that are known to contribute to discomfort and injury, reduced productivity, and increased error rates. Personal risk factors, though important, as this study shows, are often overlooked. Therefore, wellness initiatives are increasingly being seen as companions to an MSD prevention effort. 

A word of caution: Wellness initiatives are not a replacement for an ergonomics process. While they have potential to affect musculoskeletal discomfort or job stress, they do not address physical, cognitive or organizational root casues, whereas an effective ergonomics process does, or should. 

Study Limitations

• The study does not report if the subjects were male or female. However, in conclusion the authors do suggest including an equal number of male and female subjects for future research.
• Young participant population — the age ranges did not include a representative working population (the oldest subjects were 35 years of age).
• The study relied entirely on self-reported data generated by the BMI, OSI, and CMDQ questionnaires.

Sources

Jasobanta Sethi, Jaspal SINGH Sandhu, Vijay Imbanathan, Effect of Body Mass Index on work related musculoskeletal discomfort and occupational stress of computer workers in a developed ergonomic setup, Sports Medicine, Arthroscopy, Rehabilitation, Therapy & Technology, 2011, 3:22 doi:10.1186/1758-2555-3-22

At the time of this writing, the full text of this open source article was available at this link: http://www.smarttjournal.com/content/3/1/22

(1) National Medical Spending Attributable To Overweight And Obesity  http://www.asu.edu/educ/epsl/CERU/Articles/CERU-0305-71-OWI.doc

Gene Kay has a Masters degree in Exercise Science and is a Certified Ergonomics Associate. He has been designing web-based ergonomics programs for 10 years, and owns the ErgoAdvocate Ergonomics Training program.  Gene has served as the American Express Global Ergonomics Manager, a Rehab Services Manager, and is Past-President of the Upper Midwest Chapter of HFES.
 

This article originally appeared in The Ergonomics Report™ on 2011-11-15.