Being overweight/obese could have a negative effect on one’s muscular endurance, particularly in the large postural muscles of the shoulder and lower back, and this could contribute to workplace injuries and workers’ compensation claims, according to a recent study.

The study, from researchers at the Texas A&M School of Public Health and the University of Buffalo, and published in the journal Human Factors, points to a need for new ergonomics research focusing more on overweight/obese individuals in the workforce.

According to a news item from Texas A&M University Health Science Center, Ranjana Mehta, PhD, assistant professor in the Department of Environmental and Occupational Health in the Texas A&M School of Public Health, and colleague Lora Cavuoto, PhD, assistant professor from the University at Buffalo, developed a study to investigate the differences in muscular strength and endurance in normal-weight, overweight, and obese people, with the goal of paving the way for the development of such new ergonomics standards.

The duo divided 142 participants—all from Texas and New York—into three categories based on their body mass index, body fat percentage, and waist circumference.

They then tested the participants’ grip, shoulder flexion, and trunk extension endurances. These tasks were targeted due to their association with a high rate of injuries in the workplace, per the news story.

In their testing, the duo took note of each participant’s endurance time on different days and recorded the amount of the worker’s exertion at different work intensities.

According to their findings, the normal-weight participants had a higher endurance on some—but not all—of the tests compared with their overweight or obese counterparts.

“Interestingly, the results varied between muscle groups and work intensity levels,” says Mehta, in the news story. “There was no significant obesity differences in grip endurance, but normal-weight subjects had a roughly 22% longer endurance during the shoulder flexion tests and about 30% more in trunk extension than the obese subjects.”

These results show that obesity has a substantial negative effect on muscular endurance, particularly in large postural muscles of the shoulder and the lower back, and that the effects were largest at lower work intensity levels, the researchers conclude.

“The underlying reason for these differences is not fully understood,” Mehta states. “One possible contributing factor is additional body mass on parts of the body that are moving, particularly the trunk.”

Other reasons, according to the researchers, could include a reduction in slow-twitch muscle fibers, which offer fatigue resistance, in individuals who are obese; lower capillary density in muscles, making it harder for those muscles to get the blood needed during the fatiguing tasks; and changes in brain functioning recently associated with obesity.

“Regardless of why higher body mass correlates with lower muscular endurance, the findings of this study point to a need for ergonomics researchers to focus more on overweight and obesity in the workforce, as they account for more than two-thirds of the working population,” Mehta concludes. “This initial evidence will help inform strategies to keep workers safe and healthy, benefitting those workers and the workforce as a whole.”

[Source: Texas A&M University Health Science Center]