Classification of Exercise and Muscle Action Types (Dynamic vs. Static)
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Exercise is either dynamic (concentric = shortens, eccentric = lengthens) or static (isometric = no change), mapped to what happens to muscle length.
Detail
The source classifies exercise and its muscle action types by whether the exercise is dynamic or static, and by what happens to muscle length:
| Exercise | Muscle Action | Muscle Length |
|---|---|---|
| Dynamic | Concentric | Decreases |
| Eccentric | Increases | |
| Static | Isometric | No change |
Dynamic exercise involves movement and comprises concentric (muscle length decreases) and eccentric (muscle length increases) actions. Static exercise involves no movement and uses isometric action (no change in muscle length).
Key facts
- Dynamic + Concentric → muscle length decreases.
- Dynamic + Eccentric → muscle length increases.
- Static + Isometric → no change in muscle length.
Connections
- Concentric (Positive) Muscle Action — dynamic, decreasing length.
- Eccentric (Negative) Muscle Action — dynamic, increasing length.
- Isometric (Static) Muscle Action — static, no length change.
- "Muscle Action" vs. "Contraction" — The Terminology Argument — why these are "actions," not "contractions."
Sources
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Educational content only — not medical advice. Always consult a qualified professional for individualized guidance, especially around injury, pregnancy, or medical conditions.