Joint Kinetics and Lumbar Curvatures during Symmetric Lifting: Squat and Stoop

In this study, joint moments, joint powers, and lumbar lordosis were investigated for two different symmetrical lifting techniques using the three- dimensional motion analysis: squat and stoop. Twentynine male volunteers lifted boxes weighing 5, 10 and 15 kg by both squat and stoop lifting techniques. There were no significant differences in maximum lumbar joint moments between two techniques. Ankle, hip and lumbar joints generated power and only knee joint absorbed power in squat lifting, Ankle, knee joints absorbed power and hip, lumbar joints generated power in stoop lifting. At the time of lordotic curvature appearance in squat lifting, strong correlations were found in all three lower extremity joint moments with the lumbar joint. Differently, in stoop lifting, strong correlations existed in hip moment with the lumbar joint. Lordotic angle difference between fluoroscopic images and markers were 6.47plusmn1.02%, 13.01plusmn2.66 degree, and 26.43plusmn5.14 degree by three different calculation methods. In conclusion, considering the correlation with the lumbar joint, the current results suggested that lower limbs contribute to minimize mechanical loading on the waist by the change of lordotic curvature in the lumbar spine for the safe lifting.