The effects of sex and handedness on lumbar kinetics during asymmetric lifting tasks: A pilot study

Abstract

Manual material handling such as box lifting is a very common task that is used in the industrial and medical fields. It is widely accepted that manual lifting can potentially lead to low back injury. Asymmetric lifting, which involves twisting of the trunk, shifts trunk muscle activation and can increase the lower back loading on the spine thus further increasing the likelihood of injury. Other researchers have explored asymmetric lifting but have not considered the effects of handedness. Sex has also been considered as a factor related to low back injury, but majority of research work include only male subjects in literature. This work aims to examine the effects of sex, handedness, box load, and box origin on the maximum lumbar flexion/extension L5-S1 joint moments generated during two-handed box lifting so that safer lifting recommendations can be made for those tasks. Eight participants (sex: 4 women, 4 men; age: 28.62 ± 4.53 years; height: 170.00 ± 7.45 cm; body mass: 72.36 ± 8.97 kg; handedness: 4 left-dominant, 4 right-dominant) performed two-handed box lifts with five different box origins (two left lifts, one sagittally symmetric lift, and two right lifts) and three different box weights (1.20 kg, 5.74 kg, 10.27 kg). Motion data was collected using a motion capture system and force plates. There were no clear trends for the effect of sex, but our results suggest that individuals should lift from their dominant-hand side when performing asymmetric two-handed lifting tasks. Future work which will incorporate the use multiscale modeling (musculoskeletal modeling and finite element modeling) to perform a deeper analysis of spine biomechanics during these lifts at the muscle and tissue levels, respectively.