Medial Deltoid
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The middle deltoid head; the primary muscle of true shoulder abduction (90°), involving all three heads plus the supraspinatus.
Detail
The medial deltoid's function is true abduction, which involves all 3 deltoid heads with primary emphasis on the medial deltoid; it also involves the supraspinatus. Exercises are lateral raises and upright rowing. ROM is 90 degrees of shoulder-joint abduction. Some people may need a bent-over position of up to 45 degrees to fully isolate this muscle. The greater tubercle and acromion process relationship limits the movement (impingement: bones rub together). This position does not allow the use of heavy weights; beware of internal and external rotations.
Key facts
- Function: true abduction (all 3 heads, primary emphasis on medial deltoid; also supraspinatus).
- ROM: 90° of shoulder-joint abduction.
- May need a bent-over position up to 45° to isolate it.
- Greater tubercle / acromion process relationship limits the movement (impingement risk).
- Does not allow heavy weights; beware internal/external rotation.
Connections
- deltoids — group it belongs to.
- abduction — primary movement.
- supraspinatus — also involved in true abduction.
- lateral-raise / upright-row — training exercises.
Educational content only — not medical advice. Always consult a qualified professional for individualized guidance, especially around injury, pregnancy, or medical conditions.