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Diaphragmatic fiber type specific adaptation to endurance exercise
S K Powers1, D Criswell, F K Lieu
1Department of Exercise Science, University of Florida, Gainesville 32611.
Respiration Physiology
|August 1, 1992
Summary
Exercise training enhances diaphragm oxidative capacity, specifically in type I and IIa muscle fibers. Endurance training improved succinate dehydrogenase activity in these fibers, indicating increased metabolic function.
Area of Science:
- Exercise Physiology
- Skeletal Muscle Metabolism
Background:
- Exercise training improves the oxidative capacity of the mammalian diaphragm.
- Limited data exist on fiber-type specific metabolic adaptations in the diaphragm due to training.
Purpose of the Study:
- To investigate the effects of endurance training on diaphragm fiber type-specific changes in oxidative capacity, cross-sectional area, and capillarity.
- To test the hypothesis that exercise training increases oxidative capacity in diaphragmatic type I and IIa fibers only.
Main Methods:
- Female Fischer-344 rats underwent 10 weeks of treadmill exercise.
- Histological analysis identified capillaries and fiber types (ATPase histochemistry).
- Computerized image analysis measured fiber cross-sectional area (CSA) and succinate dehydrogenase (SDH) activity.
Main Results:
- Training increased capillary density in type IIa fibers due to reduced CSA, but not capillary-to-fiber ratio.
- Significant increases in total diaphragmatic SDH activity (17.5%) were observed.
- SDH activity increased in type I (14%) and IIa (17.4%) fibers, but not in type IIb fibers.
Conclusions:
- Endurance exercise training enhances oxidative capacity in specific diaphragm fiber types (I and IIa).
- Metabolic adaptations in the diaphragm are fiber-type specific following training.
- These findings contribute to understanding exercise-induced adaptations in respiratory muscles.