Obesity-related changes in prolonged repetitive lifting performance

Despite the rising prevalence of obesity, little is known about its moderating effects on injury risk factors, such as fatigue, in occupational settings. This study investigated the effect of obesity, prolonged repetitive lifting and their interaction on lifting performance of 14 participants, 7 obese (mean body mass index (BMI): 33.2 kg m(-2)) and 7 non-obese (mean BMI: 22.2 kg m(-2)) subjects. To present a physically challenging task, subjects performed repetitive lifting for 1 h at 120% of their maximum acceptable weight of lift. Generalized linear mixed models were fit to posture and acceleration data. The obese group bent to a ∼10° lower peak trunk sagittal flexion angle, had 17% lower root mean square (RMS) jerk and took 0.8 s longer per lift. Over time, the obese group increased their trunk transverse and sagittal posterior accelerations while the non-obese maintained theirs. Although the majority of lifting variables were unaffected by BMI or its interaction with prolonged lifting duration, the observed differences, combined with a greater upper body mass, necessitate a more cautious use of existing psychophysical lifting limits for individuals who are obese, particularly when fatigued.