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Lumbar erector spinae oxygenation during prolonged contractions: implications for prolonged work
S M McGill1, R L Hughson, K Parks
1Faculty of Applied Health Sciences, Department of Kinesiology, University of Waterloo, Canada. mcgill@healthy.uwaterloo.ca
Ergonomics
|May 9, 2000
Summary
Prolonged isometric exercises, even at low intensities like 2% maximal voluntary contraction (MVC), reduce back muscle oxygenation. This finding suggests a potential biological pathway for musculoskeletal issues in occupational settings involving sustained postures.
Area of Science:
- Biomedical Engineering
- Exercise Physiology
- Occupational Health
Background:
- Growing interest in torso stabilization exercises.
- Uncertainty regarding the effects of prolonged isometric holds in occupational settings.
- Need to understand back muscle oxygenation during sustained contractions.
Purpose of the Study:
- To assess back muscle oxygenation during prolonged isometric contractions.
- To investigate oxygen saturation levels at varying contraction intensities (2-30% MVC).
- To explore potential links between reduced oxygenation and occupational musculoskeletal disorders.
Main Methods:
- Utilized Near Infrared Spectroscopy (NIRS) to measure relative oxygen saturation in the L3 erector mass.
- Employed prolonged isometric contractions at 2%, 5%, 10%, 20%, and 30% of maximal voluntary contraction (MVC).
- Conducted sham trials to validate NIRS signal accuracy and rule out motion artifacts.
Main Results:
- All tested contraction levels (2-30% MVC) demonstrated a reduction in back muscle oxygenation.
- Oxygen reduction was observed even at the lowest tested intensity of 2% MVC.
- NIRS proved effective as a non-invasive tool for monitoring muscle oxygen availability during low-level, prolonged work.
Conclusions:
- Tissue oxygenation in lumbar extensor muscles decreases with increasing contraction intensity, even at very low levels.
- These findings suggest a potential biological mechanism linking prolonged occupational isometric contractions to musculoskeletal illness.
- NIRS is a valuable tool for assessing muscle oxygenation in occupational health research.