title: Selective activation of the infraspinatus muscle.
abstract: BACKGROUND
  To improve selective infraspinatus muscle strength and endurance, researchers have recommended selective shoulder external-rotation exercise during rehabilitation or athletic conditioning programs. Although selective strengthening of the infraspinatus muscle is recommended for therapy and training, limited information is available to help clinicians design a selective strengthening program.
  
  
  OBJECTIVE
  To determine the most effective of 4 shoulder external-rotation exercises for selectively stimulating infraspinatus muscle activity while minimizing the use of the middle trapezius and posterior deltoid muscles.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  University research laboratory.
  
  
  METHODS
  A total of 30 healthy participants (24 men, 6 women; age = 22.6 ± 1.7 years, height = 176.2 ± 4.5 cm, mass = 65.6 ± 7.4 kg) from a university population.
  
  
  METHODS
  The participants were instructed to perform 4 exercises: (1) prone horizontal abduction with external rotation (PER), (2) side-lying wiper exercise (SWE), (3) side-lying external rotation (SER), and (4) standing external-rotation exercise (STER).
  
  
  METHODS
  Surface electromyography signals were recorded from the infraspinatus, middle trapezius, and posterior deltoid muscles. Differences among the exercise positions were tested using a 1-way repeated-measures analysis of variance with Bonferroni adjustment.
  
  
  RESULTS
  The infraspinatus muscle activity was greater in the SWE (55.98% ± 18.79%) than in the PER (46.14% ± 15.65%), SER (43.38% ± 22.26%), and STER (26.11% ± 15.00%) (F3,87 = 19.97, P < .001). Furthermore, the SWE elicited the least amount of activity in the middle trapezius muscle (F3,87 = 20.15, P < .001). Posterior deltoid muscle activity was similar in the SWE and SER but less than that measured in the PER and STER (F3,87 = 25.10, P < .001).
  
  
  CONCLUSIONS
  The SWE was superior to the PER, SER, and STER in maximizing infraspinatus activity with the least amount of middle trapezius and posterior deltoid activity. These findings may help clinicians design effective exercise programs.
authors.affiliation: Department of Physical Therapy, Division of Health Science, Baekseok University, Republic of Korea.
authors.forename: Sung-Min
authors.initials: SM
authors.lastname: Ha
authors.forename: Oh-Yun
authors.initials: OY
authors.lastname: Kwon
authors.forename: Heon-Seock
authors.initials: HS
authors.lastname: Cynn
authors.forename: Won-Hwee
authors.initials: WH
authors.lastname: Lee
authors.forename: Su-Jung
authors.initials: SJ
authors.lastname: Kim
authors.forename: Kyue-Nam
authors.initials: KN
authors.lastname: Park
mesh_terms: D000704:Analysis of Variance; D003430:Cross-Sectional Studies; D004576:Electromyography; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D012399:Rotation; D012785:Shoulder Joint / Q000502:physiology*; D055815:Young Adult