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Lumbar stress distribution in sitting posture with considering spinal alignment: A finite element analysis
Ryota Toyohara1,2, Takahiro Hiramukai3, Toshiro Ohashi1
1Faculty of Engineering, Hokkaido University, Sapporo, Japan.
Bio-Medical Materials and Engineering
|July 14, 2025
Summary
Sitting shallowly and tilting the seat pan forward reduces lower back pain. This ergonomic adjustment decreases stress on intervertebral discs and sacroiliac joints (SIJs) by altering trunk-thigh angles.
Area of Science:
- Biomechanics
- Ergonomics
- Spinal Health
Background:
- Prolonged sitting on chairs places significant stress on the lower back.
- This posture can lead to the development of lower back pain.
- Understanding lumbar stress distribution is crucial for ergonomic design.
Purpose of the Study:
- To analyze lumbar stress distribution under various sitting conditions.
- To visualize stress on intervertebral discs and sacroiliac joints (SIJs).
- To identify optimal sitting postures for reducing lower back load.
Main Methods:
- Measured body pressure distribution on chair backrests and seat pans for six subjects.
- Created finite element models of the spine and pelvis to simulate sitting postures.
- Analyzed lower back stress distribution based on pressure measurements and finite element analysis.
Main Results:
- Forward-tilted seat pans reduced backrest pressure; larger sitting distances increased it.
- Shallow sitting and forward-tilted seat pans decreased equivalent stresses on SIJs and intervertebral discs.
- These postures increase the trunk-thigh angle, reducing the moment applied to the sacrum.
Conclusions:
- Sitting shallowly with a forward-tilted seat pan reduces the load on the lower back.
- Ergonomic adjustments to chair design can mitigate risks of lower back pain.
- Optimizing sitting posture is key to improving spinal health during seated activities.
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