Effect of lumbar lordotic angle on lumbosacral joint during isokinetic exercise: a simulation study.

Background: It is important to consider lumbar lordotic angle for setup of training program in field of sports and rehabilitation to prevent unexpected posture deviation and back pain. The purpose of this study was to to analyze the biomechanical impact of the level of lumbar lordosis angle during isokinetic exercise through dynamic analysis using a 3-dimensional musculoskeletal model.

Methods: Gait analysis and isokinetic exercise for the healthy adults (n=10) were performed to design a 3-dimensional musculoskeletal model and then we made each model for normal lordosis, excessive lordosis, lumbar kyphosis, and hypo-lordosis according to lordotic angle and inputted experimental data as initial values to perform inverse dynamic analysis to quantify muscle joint torque, joint forces of each joint, system energy, and estimated muscle forces at lumbosacral joint.

Findings: Comparing the joint torques, the largest torque of excessive lordosis was 16.6% larger than that of normal lordosis, and lumbar kyphosis was 11.7% less than normal lordosis. There existed no significant difference in the compressive intervertebral forces of each lumbar joint (P>0.05), but statistically significant difference in the anterioposterior shear force (lumbar kyphosis>hypo-lordosis>excessive lordosis>normal lordosis, P<0.05). Lastly, lumbar kyphosis required the least and most energy during flexion and extension respectively.

Interpretation: During the rehabilitation process, more efficient training will be possible by taking into consideration not simply weight and height but biomechanical effects on the skeletal muscle system according to lumbar lordortic angles.