Concentric (Positive) Muscle Action
Sources and review status
Review pending — this text hasn’t been signed off by a reviewer yet.
Historical reference: its only source is the original reference manual, and some of it may be out of date. Not used for AI answers until re-sourced.
See this lesson’s sources0% read · 1 min left
The lifting phase — a dynamic action where the whole muscle shortens, its ends draw closer together, and joint movement occurs.
Detail
A concentric action (also called positive action) is a dynamic muscle action in which the whole muscle shortens and joint movement occurs — one in which the ends of the muscle are drawn closer together. In a repetition it is the concentric phase: the muscle shortens against a load.
It is the "positive" half of a dynamic exercise and decreases muscle length. The source recommends executing it without momentum:
- Refrain from using momentum (which reduces muscular loading).
- Use a deliberate, controlled manner.
- Ballistic-type movements compromise safety and effectiveness.
Concentric action produces less force than eccentric action: the muscles produce more force in lowering (eccentric) action than in lifting (concentric) action — the eccentric phase is roughly 40% stronger than the concentric phase. Typical prescribed tempos in the source's programs run about 1 to 2 seconds for the concentric (positive) phase.
Key facts
- Concentric = positive action; the muscle shortens, ends draw closer, joint moves.
- The lifting phase of a repetition; decreases muscle length.
- Produces less force than eccentric action (concentric ≈ 40% weaker).
- Perform deliberately, controlled, without momentum or ballistic movement.
Connections
- Eccentric (Negative) Muscle Action — the stronger lowering counterpart.
- Isometric (Static) Muscle Action — the static, no-movement action.
- "Muscle Action" vs. "Contraction" — The Terminology Argument — why "action" rather than "contraction."
- Positive and Negative Resistance — positive/negative resistance framing.
- Tempo / Time Per Repetition — repetition timing of the concentric phase.
Sources
Keep this lesson, or ask how it applies to you.
Educational content only — not medical advice. Always consult a qualified professional for individualized guidance, especially around injury, pregnancy, or medical conditions.