Increased co-contraction of arm adductors is associated with a favorable course in subacromial pain syndrome

Celeste L. Overbeek, Arjen Kolk, Jochem Nagels, Pieter Bas de Witte, Peer van der Zwaal, Cornelis P.J. Visser, Marta Fiocco, Rob G.H.H. Nelissen, Jurriaan H. de Groot

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15 Citations (Scopus)


Background: Enhancement of arm adductor activity during abduction (ie, adductor co-contraction), may be effective in the treatment of subacromial pain syndrome (SAPS). We assessed whether an increase of adductor co-contraction is associated with a favorable course of SAPS. Methods: At baseline and after nearly 4 years of follow-up, electromyography of the latissimus dorsi (LD), teres major (TM), pectoralis major, and deltoid muscle was obtained during isometric abduction and adduction tasks in 26 patients with SAPS. Changes in co-contraction were assessed with change in the activation ratio (ΔAR). The AR ranges between −1 and 1, where lower values indicate more co-contraction. Clinical course was determined from an anchor question (reduced, persistent, or increased complaints), the visual analog scale for pain (VAS), and the Western Ontario Rotator Cuff score (WORC). Results: In patients indicating persistent complaints (31%), the VAS and WORC remained stable. In patients who indicated reduced complaints (69%), the VAS reduced (z score, −3.4; P =.001) and WORC increased (z score, 3.6; P <.001). Unchanged ARs associated with complaints persistence, whereas decreased AR of the LD (ΔARLD, −0.21; 95% confidence interval [CI], −0.36 to −0.06) and TM (ΔARTM, −0.17; 95% CI, −0.34 to −0.00) coincided with reduced complaints. There was a significant between-group difference in ΔARLD (−0.35; 95% CI, −0.60 to 0.10) and ΔARTM (−0.36; 95% CI, −0.66 to –0.05). Conclusions: Increased co-contraction of the LD and TM is associated with a favorable course of SAPS. This may be explained by widening of the subacromial space accomplished by adductor co-contraction.

Original languageEnglish
Pages (from-to)1925-1931
Number of pages7
JournalJournal of Shoulder and Elbow Surgery
Issue number11
Publication statusPublished - Nov 2018
Externally publishedYes


  • biomechanical phenomena
  • co-contraction
  • electromyography
  • latissimus dorsi
  • Level I
  • Prognostic Study
  • Prospective Design
  • Shoulder impingement syndrome
  • teres major


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