Spinal shrinkage during work in a sitting posture compared to work in a standing posture

Area of Science:

• Occupational Health
• Biomechanics
• Spinal Physiology

Background:

• Existing research on spinal load in sitting vs. standing positions is contradictory.
• Little is known about thoracic and lumbar spine height reduction during prolonged (6.5 hours) work in realistic environments.
• Investigating spinal behavior under practical working conditions is necessary.

Purpose of the Study:

• To quantify differences in thoracolumbar spine shrinkage between sitting and standing work postures.
• To examine isolated shrinkage of the thoracic and lumbar spine.
• To develop and utilize a novel protocol for measuring spinal shrinkage.

Main Methods:

• A stadiometer with 0.51 mm error measured spinal height changes over 6.5-hour work periods.
• A 50-minute pre-test excluded initial spinal adaptation.
• Benchmarks at vertebrae prominens and thoracolumbar junction separated thoracic and lumbar spine measurements.
• Three cohorts: sitting work, standing work, and comparison of relaxed sitting vs. working while sitting.

Main Results:

• Relaxed sitting resulted in a stature gain, primarily in the lumbar spine, compared to working while sitting.
• Spinal shrinkage was significantly greater when working in a standing posture compared to a sitting posture.
• Lumbar spine shrinkage was notably higher in the standing cohort (4.16 mm) versus the sitting cohort (1.73 mm).

Conclusions:

• Prolonged sitting, especially when relaxed, can lead to stature gain.
• Working in a standing posture imposes a greater load on the spine.
• Increased lumbar spine shrinkage in standing work is likely due to altered lumbar lordosis and biomechanical forces like bending and torsion.