Dynamics of Trunk Performance during One-Handed Lifting

This study investigated the biomechanical effects of using one hand to perform a materials handling task. Subjects were asked to lift a box from a lower to an upper platform using either one or two hands. Three weight levels and four lower platform positions were examined. Subjects wore a back monitor (from which was calculated motion components in the three cardinal planes of the body), stood on a force plate, and were asked to give a rating of perceived exertion for each lift. Results of this study showed that one-handed lifts produced significantly higher ranges of lumbar spine motion in the lateral and transverse planes and greater flexion in the sagittal plane. Back motion risk factors previously found to be associated with high risk of injury jobs all were significantly higher for one-handed lifts. Two-handed lifts, however, produced overall faster motions in the sagittal plane, and equal or larger acceleration and deceleration magnitudes in all planes of motion. Results from the psychophysical measure found no differences in perceived exertion between one- and two-handed lifts. These results suggest that one-handed lifts load the spine more than two-handed lifts due to the added coupling and increase one's risk of suffering a low back disorder. This study also agrees with previous research finding that increased load weight and lifting from asymmetric positions increase risk of low back injury.