The effect of clinically elevated body mass index on physiological stress during manual lifting activities

• Published in: PloS one Vol. 17; no. 12; p. e0278858
• Main Authors: Lemus, Sergio A, Volz, Mallory, Tiozzo, Eduard, Perry, Arlette, Best, Thomas M, Travascio, Francesco
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 28.12.2022; Public Library of Science (PLoS)
• Subjects: Biology and Life Sciences; Body mass; Body Mass Index; Body measurements; Body size; Body weight; Carbon dioxide; Classification; Energy expenditure; Energy Metabolism; Evaluation; Exercise; Gender; Geometry; Health risks; Heart rate; Hoisting; Humans; Indicators; Injuries; Lifting; Manual lifting; Mathematical analysis; Medicine and Health Sciences; Metabolism; Muscle strength; Musculoskeletal system; Obesity; Observations; Occupational health; Occupational health and safety; Occupational safety; Overweight; Oxygen; Parameters; Physical fitness; Physiological aspects; Physiological effects; Physiology; Safety; Statistical analysis; Stress; Stress (Physiology); Stress, Physiological; Vanadium oxides; Variance analysis; Weight limits; Workplace accidents; United States; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0278858

Individuals with a body mass index (BMI) classified as obesity constitute 27.7% of U.S. workers. These individuals are more likely to experience work-related injuries. However, ergonomists still design work tasks based on the general population and normal body weight. This is particularly true for manual lifting tasks and the calculation of recommended weight limits (RWL) as per National Institute of Occupational Safety & Health (NIOSH) guidelines. This study investigates the effects of BMI on indicators of physiological stress. It was hypothesized that, for clinically elevated BMI individuals, repeated manual lifting at RWL would produce physiological stress above safety limits. A repetitive box lifting task was designed to measure metabolic parameters: volume of carbon dioxide (VCO2) and oxygen (VO2), respiratory exchange ratio (RER), heart rate (HR), and energy expenditure rate (EER). A two-way ANOVA compared metabolic variables with BMI classification and gender, and linear regressions investigated BMI correlations. Results showed that BMI classification represented a significant effect for four parameters: VCO2 (p < 0.001), VO2 (p < 0.001), HR (p = 0.012), and EER (p < 0.001). In contrast, gender only had a significant effect on VO2 (p = 0.014) and EER (p = 0.017). Furthermore, significant positive relationships were found between BMI and VCO2 (R2 = 59.65%, p < 0.001), VO2 (R2 = 45.01%, p < 0.001), HR (R2 = 21.86%, p = 0.009), and EER (R2 = 50.83%, p < 0.001). Importantly, 80% of obese subjects exceeded the EER safety limit of 4.7 kcal/min indicated by NIOSH. Indicators of physiological stress are increased in clinically elevated BMI groups and appear capable of putting these individuals at increased risk for workplace injury.