Clinical Significance

The serratus anterior originates from the lateral surfaces of ribs 1–9 and inserts along the entire medial border of the scapula. Its primary actions are scapular protraction and — more importantly — upward rotation of the scapula during arm elevation. Without adequate serratus activation during shoulder elevation, the scapula fails to rotate upwardly to follow the elevating humerus, the glenoid fossa tilts downward relative to the humeral head, subacromial space narrows, and impingement occurs. Medial scapular winging — the visual sign of serratus anterior weakness — is the anatomical expression of this failure.

The serratus anterior is innervated by the long thoracic nerve (C5–C7), which is vulnerable to traction injury from shoulder trauma, heavy lifting, and thoracic surgery. More commonly in clinical practice, serratus inhibition is reflexogenic — reduced neural drive secondary to shoulder pain, poor thoracic mobility, or habitual poor posture — rather than from nerve injury, and responds well to targeted activation training.

Exercises in Progression

Level 1 — Isolated protraction: Wall push-up plus (standard wall push-up, at the top position add maximal scapular protraction by pushing the thorax away from the wall an additional 2–3 cm). The protraction phase at the top is where serratus is most active. Perform slowly, holding the protractions position for 2 seconds. Progress to push-up plus (floor position).

Level 2 — Scapular dissociation exercises: Serratus punch (supine, arm vertical, push the weight toward the ceiling by protracting the scapula off the table — the arm stays straight, only the scapula moves). Cable punch (standing, cable from low position, forward punch finishing with scapular protraction). Both exercises train serratus in its protraction role without excessive loading of the glenohumeral joint.

Level 3 — Functional integration: Bear crawl (quadruped position, knees hovering 2–3 cm from floor, walking forward and backward while maintaining scapular protraction — demands sustained serratus activation under load). Plank with protraction (standard plank, but actively push the floor away and round the thoracic spine slightly, maintaining maximum scapular protraction). Single-arm cable row with exaggerated protraction phase trains serratus in its functional coupling with the rhomboids and middle trapezius.

Differentiating serratus and upper trap dominance: During shoulder elevation exercises, a patient with serratus weakness will show early shoulder shrugging (upper trapezius dominance) before the arm reaches 90° elevation. Place one hand gently on the upper trapezius during arm elevation — if it fires immediately on initiation of elevation, before the arm reaches 60–70°, serratus is underactive and trapezius is compensating. This pattern is the most common finding in patients with subacromial pain and should direct exercise selection toward serratus isolation before loaded elevation.

Programming

3 sets of 12–15 repetitions with a 2-second hold at peak protraction, 3× weekly. Serratus anterior responds well to higher-rep, moderate-load training that emphasises time under tension at the end-range protractions position. Progress from wall to floor to loaded variations over 4–6 weeks as scapular control improves.

References & Further Reading

  1. Cools AM, et al. Rehabilitation of scapular muscle balance. Am J Sports Med. 2007;35(10):1744–1751.
  2. Ludewig PM, Reynolds JF. The association of scapular kinematics and glenohumeral joint pathologies. J Orthop Sports Phys Ther. 2009;39(2):90–104.
  3. Kibler WB, et al. Clinical implications of scapular dyskinesis in shoulder injury. Br J Sports Med. 2013;47(14):877–885.