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Passive tissues help the back muscles to generate extensor moments during lifting
P Dolan1, A F Mannion, M A Adams
1Department of Anatomy, University of Bristol, U.K.
Journal of Biomechanics
|August 1, 1994
Summary
Passive tissues significantly contribute to erector spinae extensor moments during lifting, especially in flexed postures. This highlights the importance of passive structures in spinal biomechanics and injury prevention.
Area of Science:
- Biomechanics
- Spinal Physiology
- Occupational Health
Background:
- The erector spinae muscles are crucial for generating extensor moments during lifting.
- The role of passive tissues in supporting spinal loads during lifting is not fully understood.
Purpose of the Study:
- To investigate the contribution of passive tissues to erector spinae extensor moments during lifting.
- To quantify the relationship between passive tissue resistance and lumbar flexion angle.
Main Methods:
- 149 healthy adults performed isometric pulls and lifted weights.
- Electromyography (EMG) of erector spinae at L3 and T10 was recorded.
- Lumbar flexion was measured using the '3-Space Isotrak' system.
Main Results:
- Passive tissues resisted a flexion moment (I) that increased with lumbar flexion, from 25 Nm to 120 Nm (men) and 77 Nm (women).
- Peak extensor moments during lifting occurred at 78-97% of the lumbar flexion range.
- A linear relationship was observed between extensor moment and EMG activity.
Conclusions:
- Passive spinal tissues play a substantial role in generating extensor moments, particularly in flexed postures.
- Understanding passive tissue contributions is vital for analyzing lifting mechanics and preventing injuries.