Horizontal Extension (Abduction)
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Returning the humerus from the front-horizontal position back to the side-horizontal position.
Detail
Horizontal extension (also called horizontal abduction) is movement of the humerus from the front-horizontal position returning to the side-horizontal position. It is the key action of the posterior deltoid. For the latissimus dorsi, horizontal abduction (extension) — drawing the arm from the front to the side-horizontal position — is a weak action because it primarily emphasizes the trapezius and rhomboids. Source attributes the movement terminology to Thompson (1989).
Key facts
- Horizontal extension / horizontal abduction = humerus moved from front-horizontal back to side-horizontal.
- Key action of the posterior deltoid.
- A weak action of the latissimus dorsi (emphasizes trapezius and rhomboids instead).
Connections
- Horizontal Flexion (Adduction) — the opposite movement.
- Posterior Deltoid — primary producer of horizontal abduction.
- Infraspinatus — involved in horizontal abduction and extension.
- Teres Minor — involved in horizontal abduction and extension.
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.