The Impact of Obesity through Increased Body Fat, Added Girth and Added Weight on Lifting Capacity
Open Access
- Author:
- Cintron, Lorna Raquel
- Graduate Program:
- Industrial Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- December 07, 2012
- Committee Members:
- Andris Freivalds, Dissertation Advisor/Co-Advisor
Dr Paul Griffin, Committee Member
M Jeya Chandra, Committee Member
Dr Samuel Oyewole, Committee Member
Diane Marie Spokus, Special Member - Keywords:
- Ergonomics
Obesity
BMI
NIOSH
RWL
Lifting Capacity
MAWL
L5S1 - Abstract:
- Obesity is a condition of epidemic proportions affecting not only our country, with over 60% of the US population being at least overweight, but the entire world. As a result of obesity, an adult’s daily life may be affected physically, socially, and even psychologically. Coupled with its impact on health, the effects of obesity are often reflected in the workplace in the form of, for example, loss of productivity and increased incidence of lower-back injuries and other musculoskeletal disorders (MSDs). This research investigated the impact of obesity on lifting capacity (LC). Two experiments were conducted in a laboratory setting. The first experiment evaluated the effect of obesity by means of three common measures of obesity, Body Mass Index (BMI), waist circumference (WC) and estimated percent body fat (%BF), as well as other physical and biomechanics-related factors, on LC. LC was represented by an average lifting strength (ALS) and the Maximum Acceptable Weight of Load (MAWL), which was measured through a psychophysical test. A general lineal model (GLM) found that the weight and %BF of participants had a significant effect on MAWL at a 95% confidence level. Height, BMI and the interaction between gender and %BF had a significant effect on ALS. When biomechanics-related factors were introduced in the analysis of ALS, it was found that WC, the L5S1 disc compression and the interaction between gender and %BF. Evidence was found to confirm that when obesity was measured by BMI and %BF, the LC of obese individuals decreased and that gender difference was an underlying factor affecting the response. The second experiment was designed to analyze factors that may cause obesity to have an effect on LC: (1) increased girth and (2) increased weight in the anterior part of the body. Results of GLM analysis showed that age, gender, an experimental BMI, the compression in the L5S1 disc and the randomized lifting order had a significant effect on ALS. However, the lifting conditions (increased girth and increased weight) in which participants performed lifting tasks, did not have a significant effect on LC and were not statistically different from each other either. Because the experimental BMI was significant, it was concluded that the effect of the additional weight was confounded with this factor and that it negatively affected the LC. Results of these two research experiments suggested, in general, that the increased %BF and BMI were two obesity measures that negatively affected the LC of individuals, as well as gender. These findings led to an experimental addition to the National Institute for Occupational Safety and Health (NIOSH) Recommended Weight of Lift (RWL) equation, which currently fails to account for the health of workers. This research proposed that a physical health multiplier (PM), based on the %BF and gender, could be added to this equation to account for the health status of workers. This multiplier would depend on the average %BF of the group of subjects that will perform lifting tasks in the workplace. Adding this multiplier would decrease the RWL for overweight and obese individuals, therefore reflecting the results of the experiments conducted as part of this research. This recommendation does not intend to discriminate against any individual and is not approved by NIOSH. In addition, the multiplier was derived using the data collected in this study, which was conducted in a laboratory setting and it may not fully represent the real population of obese workers in the US. Instead, the most important benefit of such addition to the RWL equation is to increase the safety of workers by giving management an additional and alternative tool to help analyze and design lifting tasks if health is a concern of the organization. The purpose of the multiplier was to take into consideration the obesity wave affecting the US and would not only be applicable to manual material handling jobs, but may also impact patient handling tasks in the health care industry.