Deltoids
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The three-headed shoulder muscle — anterior, medial, and posterior deltoid — each with distinct actions.
Detail
The deltoid has three heads — anterior, medial (middle), and posterior — shown in three views in the source (Ellison, 1991). Each head performs a different action: the anterior deltoid is involved in pressing movements, the medial deltoid in true abduction, and the posterior deltoid in horizontal abduction and backward extension. In lateral raises, the exercise involves all three heads (with MEO on the medial deltoid).
Key facts
- Three deltoid heads: anterior, medial (middle), posterior.
- Anterior — pressing/flexion; medial — abduction; posterior — horizontal abduction/extension.
Connections
- Anterior Deltoid — front head.
- Medial Deltoid — middle head; true abduction.
- Posterior Deltoid — rear head; horizontal abduction.
- Shoulder / Arm Range of Motion — shoulder ROM values.
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.