Atypical shoulder muscle activation in multidirectional instability

J. M. Barden, R. Balyk, V. J. Raso, M. Moreau, K. Bagnall

Research output: Contribution to journalArticlepeer-review

87 Citations (Scopus)


Objective: Surface and intramuscular electromyography was used to investigate shoulder muscle activity in subjects with multidirectional instability (MDI). Methods: Subjects (seven MDI, 11 control) performed repetitive shoulder abduction/adduction, flexion/extension and internal/external rotation movements on an isokinetic dynamometer. The activity of the deltoid, infraspinatus, supraspinatus, latissimus dorsi, and pectoralis major muscles were recorded using double-differential surface and intramuscular fine-wire electrodes. A repeated measures analysis of variance evaluated group differences in the amplitude, onset, termination and duration of the muscle activity. Results: Significant activation parameter differences for the supraspinatus, infraspinatus, posterior deltoid and pectoralis major muscles were found in the subjects with MDI. The rotator cuff and posterior deltoid muscles demonstrated abbreviated periods of activity when performing internal/external rotation, despite activation amplitudes that were similar to the controls. In contrast, the activation of the pectoralis major differed from the control group in both the amplitude and time domains when performing shoulder extension. Conclusions: MDI is associated with atypical patterns of muscle activity that occur even when highly constrained movements are used to elicit the activity. Significance: In addition to glenohumeral hyperlaxity, the results suggest that dysfunctional neuromuscular control of the rotator cuff is also a contributing factor to the pathoetiology of MDI.

Original languageEnglish
Pages (from-to)1846-1857
Number of pages12
JournalClinical Neurophysiology
Issue number8
Publication statusPublished - Aug 2005
Externally publishedYes


  • Electromyography
  • Multidirectional shoulder instability
  • Rotator cuff
  • Temporal activation characteristics

ASJC Scopus subject areas

  • Sensory Systems
  • Neurology
  • Clinical Neurology
  • Physiology (medical)


Dive into the research topics of 'Atypical shoulder muscle activation in multidirectional instability'. Together they form a unique fingerprint.

Cite this