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Initial events in exercise-induced muscular injury
1Department of Physical Education, University of Georgia, Athens 30602.
Medicine and Science in Sports and Exercise
|August 1, 1990
Summary
Eccentric exercise causes skeletal muscle fiber injury, including myofilament disruption and protein loss. Intracellular calcium (Ca2+) imbalance may drive these damaging processes before immune cells arrive.
Area of Science:
- Exercise Physiology
- Muscle Biology
- Cellular Injury Mechanisms
Background:
- Unaccustomed exercise, especially eccentric contractions, leads to skeletal muscle fiber injury.
- This injury involves myofilament disruption and loss of intramuscular proteins, indicating sarcolemma damage.
- Consequences include reduced muscle force and delayed-onset muscle soreness.
Purpose of the Study:
- To investigate the underlying mechanisms of skeletal muscle injury following eccentric exercise.
- To explore the potential role of intracellular calcium (Ca2+) homeostasis disruption.
Main Methods:
- Microscopic examination (light and electron) of skeletal muscle fibers post-exercise.
- Analysis of intramuscular protein levels in plasma (e.g., creatine kinase).
- Review of existing experimental muscle injury models to infer potential pathways.
Main Results:
- Evidence of disrupted myofilament structures and loss of intramuscular proteins (e.g., creatine kinase) into plasma observed.
- Reduced muscle force and delayed-onset soreness are associated with this pathology.
- Elevated intracellular calcium ([Ca2+]i) is hypothesized to play a primary role in initiating injury.
Conclusions:
- The initial stages of exercise-induced muscle injury are autogenetic, originating within muscle cells.
- Disrupted intracellular Ca2+ homeostasis may trigger enzyme release and sarcolemma damage via pathways involving phospholipase A2.
- The precise mechanism of myofibril damage due to increased [Ca2+]i remains to be elucidated.