Effects of a simulated industrial bin on lifting and lowering posture and trunk extensor muscle activity

Abstract

The purpose of the current study was to evaluate the effects of a simulated industrial bin on lifting and lowering posture and erector spinae activation levels for 11 male and 11 female subjects. Subjects handled loads under the following conditions: (1) two directions (loads were lifted from the floor to knuckle height or lowered from knuckle height to the floor), (2) two constraint conditions (the load was placed on the floor allowing a freestyle lift, or was placed behind a 60 cm high barrier simulating an industrial bin). Surface EMG data were collected from the right lumbar and thoracic erector spinae and posture data were collected to represent the knee, pelvis, spine and trunk angles. Peak and average values were recorded for each variable for each trial. Few posture differences existed between male and female subjects and between lifting and lowering but, as expected, lifting required greater activation of the erector spinae muscles. Interestingly, while the simulation of an industrial bin required a greater flexion of the trunk segment during both lifting and lowering, this was accomplished almost entirely by rotations of the pelvis about the hip joint. This may be seen as an effort to avoid increased spine flexion in an attempt to control the risk of injury associated with load handling over a barrier. Relevance to industry To the author's knowledge, this is one of the only studies to look at the effects of a constraining barrier on lifting and lowering, which has implications for many material handling tasks found in industry. The main finding of the study was that the constraint appeared to increase the risk of injury during lifting and lowering by increasing horizontal reach, trunk flexion and spine loading.