Investigation of lumbar and cervical lordosis variation in sit-to-stand-to-sit movement with different strategies in healthy subjects

BackgroundDue to lower limb impairment, people use greater trunk flexion strategies and cannot maintain the alignment of the upper body, leading to loss of lordosis over time.ObjectiveA comprehensive study is needed to understand the heightened trunk flexion effect on lumbar and cervical lordosis and associated joint moments.MethodsThe three sit-to-stand-to-sit strategies, Natural, Full trunk flexion, and Pelvis-spine alignment, were conducted in 3D motion capture. The hypothesis is that increasing the total lumbar and cervical lordosis depth will reduce the total lumbosacral and cervicothoracic joint moment. Using Visual 3D, inverse kinematics and dynamics for joint moments and angles of the head, trunk, and pelvis at five events/phases, and the corresponding lordosis depth was calculated.ResultsPelvis-spine alignment strategies show a strong positive correlation (r = 0.70) between the total depth of lordosis and reducing the lumbosacral and cervicothoracic joint moment. The full flexion strategy mirrored the compensatory movement with a negative correlation (r = -0.88) on the reduction of lordosis depth and compensated by increasing the cervical lordosis depth.ConclusionsThese findings guide the correcting of spine disorders, the development of physical rehabilitation programs, the design of devices, and the correctness of posture to prevent low back pain and disease progression.