From Stoop to Squat: A comprehensive analysis of lumbar loading among\n different lifting styles

Abstract

Lifting up objects from the floor has been identified as a risk factor for\nlow back pain, whereby a flexed spine during lifting is often associated with\nproducing higher loads in the lumbar spine. Even though recent biomechanical\nstudies challenge these assumptions, conclusive evidence is still lacking. This\nstudy therefore aimed at comparing lumbar loads among different lifting styles\nusing a comprehensive state-of-the-art motion capture-driven musculoskeletal\nmodeling approach. Thirty healthy pain-free individuals were enrolled in this\nstudy and asked to repetitively lift a 15 kg-box by applying 1) a freestyle, 2)\na squat and 3) a stoop lifting technique. Whole-body kinematics were recorded\nusing an optical motion capture system and used to drive a full-body\nmusculoskeletal model including a detailed thoracolumbar spine. Compressive,\nshear and total loads were calculated based on a static optimization approach\nand expressed as factor body weight (BW). In addition, lumbar lordosis angles\nand total lifting time were calculated. All parameters were compared among the\nlifting styles using a repeated measures design. For all lumbar segments, stoop\nlifting showed significantly lower compressive and total loads (-0.3 to -1.0BW)\nwhen compared to freestyle and squat lifting. Stoop lifting produced higher\nshear loads (+0.1 to +0.8BW) in the segments T12/L1 to L4/L5, but lower loads\nin L5/S1 (-0.2 to -0.4BW). Peak compressive and total loads during squat\nlifting occurred approximately 30% earlier in the lifting cycle compared to\nstoop lifting. Stoop lifting showed larger lumbar lordosis range of motion\n(35.9+/-10.1{\\deg}) than freestyle (24.2+/-7.3{\\deg}) and squat\n(25.1+/-8.2{\\deg}) lifting. Lifting time differed significantly with freestyle\nbeing executed the fastest (4.6+/-0.7s), followed by squat (4.9+/-0.7s) and\nstoop (5.9+/-1.1s).\n