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Twisting mobility of the human back in flexed postures
1Department of Orthopaedic Surgery and Trauma, Royal Adelaide Hospital, South Australia.
Spine
|January 1, 1993
Summary
Seated postures significantly increase spinal twisting mobility compared to standing. This suggests a higher risk of back injury when twisting combined with flexion, especially in seated positions.
Area of Science:
- Biomechanics
- Spinal Anatomy
Background:
- Spinal mobility is crucial for daily activities.
- Understanding how posture affects spinal twisting is important for injury prevention.
Purpose of the Study:
- To quantify the effect of different postures on spinal twisting mobility.
- To investigate the relationship between spinal flexion and twisting.
Main Methods:
- Electromagnetic motion tracking (3SPACE Isotrak) was used.
- Ten healthy subjects were tested in five postures: upright standing, two forward-leaning, and two seated positions.
- Active twisting and spinal flexion angles were measured.
Main Results:
- Forward-leaning postures showed no significant change in twisting compared to upright.
- Seated postures with mean flexion of 32 and 44 degrees increased active twisting by 38% and 46% (P < 0.0001).
- Zygapophysial joint morphology allows increased twisting with flexion, but postural muscles may limit it in forward leaning.
Conclusions:
- Seated postures enhance spinal twisting mobility.
- The combination of twisting and flexion, particularly in seated positions, may increase the risk of posterior anulus injury.
- Postural muscle activity influences active twisting during flexion.