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Fibre types in human lumbar back muscles
1Department of Physiology III, Karolinska Institute, Stockholm, Sweden.
Acta Physiologica Scandinavica
|October 1, 1987
Summary
Human lumbar back muscles show similar fiber type distribution between multifidus and longissimus. Females have a higher proportion of type I muscle fibers by area, suggesting different functional capacity compared to males.
Area of Science:
- Human anatomy and physiology
- Muscle biology
- Histochemistry
Background:
- The human erector spinae muscle group in the lumbar region is crucial for posture and movement.
- Understanding the composition of the multifidus and longissimus muscles is key to understanding lumbar spine function.
- Previous research has not fully elucidated the differences or similarities in muscle fiber types between these two key lumbar muscles.
Purpose of the Study:
- To compare the distribution and characteristics of muscle fiber types in the human multifidus and longissimus muscles.
- To investigate potential sex-based differences in muscle fiber composition and area in the lumbar erector spinae.
- To assess the functional implications of muscle fiber distribution in the lumbar back muscles.
Main Methods:
- Biopsy samples were taken from the multifidus and longissimus muscles of 16 healthy young adults (9 males, 7 females).
- Muscle fibers were histochemically classified as types I, IIA, IIB, or IIC based on myofibrillar ATPase pH lability.
- Oxidative potential was assessed using NADH-diaphorase staining intensity.
Main Results:
- No significant differences were found in the relative occurrence or size of muscle fiber types (I, IIA, IIB) between the multifidus and longissimus muscles.
- Type I fibers exhibited high oxidative potential, while type II fibers showed low oxidative potential in both muscles.
- Females had a larger relative area occupied by type I fibers due to smaller type II fibers, leading to higher type I/II area ratios compared to males.
Conclusions:
- The multifidus and longissimus muscles share similar histochemical fiber-type distributions, suggesting no functional differentiation between them in the lumbar erector spinae.
- Sex-based differences in muscle fiber area ratios indicate potentially distinct functional capacities of lumbar back muscles between males and females.
- These findings contribute to a better understanding of lumbar muscle structure and potential functional variations.