title: Glenohumeral muscle activation during provocative tests designed to diagnose superior labrum anterior-posterior lesions.
abstract: BACKGROUND
  Despite considerable medical advances, arthroscopy remains the only definitive means of superior labrum anterior-posterior (SLAP) lesion diagnosis. Natural shoulder anatomic variants limit the reliability of radiographic findings and clinical evaluations are not consistent. Accurate clinical diagnostic techniques would be advantageous because of the invasiveness, patient risk, and financial cost associated with arthroscopy.
  
  
  OBJECTIVE
  The purpose of this study was to examine the behavior of the joint-stabilizing muscles in provocative tests for SLAP lesions. Electromyography was used to characterize the muscle behavior, with particular interest in the long head of the biceps brachii (LHBB), as activation of the long head and subsequent tension in the biceps tendon should, based on related research, elicit labral symptoms in SLAP lesion patients.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Volunteers (N = 21) without a history of shoulder injury were recruited. The tests analyzed were active compression, Speed's, pronated load, biceps load I, biceps load II, resisted supination external rotation, and Yergason's. Tests were performed with a dynamometer to improve reproducibility. Muscle activity was recorded for the long and short heads of the biceps brachii, anterior deltoid, pectoralis major, latissimus dorsi, infraspinatus, and supraspinatus. Muscle behavior for each test was characterized by peak activation and proportion of muscle activity.
  
  
  RESULTS
  Speed's, active compression palm-up, bicep I, and bicep II produced higher long head activations. Resisted supination external rotation, bicep I, bicep II, and Yergason's produced a higher LHBB proportion.
  
  
  CONCLUSIONS
  Biceps load I and biceps load II elicited promising long head behavior (high activation and selectivity). Speed's and active compression palm up elicited higher activation of the LHBB, and resisted supination and Yergason's elicited selective LHBB activity. These top performing tests utilize a unique range of test variables that may prove valuable for optimal SLAP test design and performance.
  
  
  CONCLUSIONS
  This study examines several provocative tests that are frequently used in the clinical setting as a means of evaluating a potential SLAP lesion.
authors.affiliation: Center for Orthopaedic and Biomechanics Research, Boise State University, Idaho, USA.
authors.forename: Vanessa J C
authors.initials: VJ
authors.lastname: Wood
authors.forename: Michelle B
authors.initials: MB
authors.lastname: Sabick
authors.forename: Ron P
authors.initials: RP
authors.lastname: Pfeiffer
authors.forename: Seth M
authors.initials: SM
authors.lastname: Kuhlman
authors.forename: Jason H
authors.initials: JH
authors.lastname: Christensen
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Curtin
mesh_terms: D000293:Adolescent; D000328:Adult; D001134:Arm Injuries / Q000175:diagnosis*; D002358:Cartilage, Articular / Q000293:injuries; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*; D055815:Young Adult