Loads in the spinal structures during lifting: development of a three-dimensional comprehensive biomechanical model

Area of Science:

• Biomechanics
• Spine Mechanics
• Occupational Health

Background:

• Daily spinal loads contribute to low back pain onset.
• Lumbar spine loads are distributed among muscles, posterior elements, and discs.
• In vivo force measurement in spinal structures is experimentally challenging.

Purpose of the Study:

• To develop and validate a biomechanical model for predicting spinal forces.
• To collect subject-specific data for accurate biomechanical modeling.
• To quantify spinal loads during dynamic and static lifting tasks.

Main Methods:

• Developed a laboratory protocol for comprehensive subject-specific data collection.
• Utilized an optimization technique based on electromyographic activities.
• Formulated a biomechanical model incorporating subject-derived data.

Main Results:

• Lifting 0 N, 90 N, and 180 N generated max external flexion moments of 109.6, 137.9, and 161.7 Nm at L3-4.
• Corresponding axial compression forces on the L3-4 disc were 469.5 N, 511.8 N, and 601.5 N.
• Disc compression ranged from 3.4 to 5.0 times body weight; dynamic lifting increased compression by 15.8%–39.4% compared to static lifting.

Conclusions:

• The developed protocol enables accurate biomechanical modeling of spinal loads.
• Dynamic lifting tasks impose significantly higher compressive forces on the lumbar disc.
• Findings highlight the biomechanical basis for low back pain in dynamic lifting activities.