title: Shoulder-muscle electromyography during shoulder external-rotation exercises with and without slight abduction.
abstract: Standing and side-lying external-rotation exercises produce high activation of the deltoid and infraspinatus. Slight shoulder abduction during these exercises may decrease deltoid activity and increase infraspinatus activity.
  
  
  
  To determine if the addition of a towel under the arm during standing and side-lying external rotation affects infraspinatus, middle and posterior deltoid, and pectoralis major activation characteristics compared with a no-towel condition.
  
  
  
  Controlled laboratory study.
  
  
  
  20 male volunteers (age 26 ± 3 y, height 1.80 ± 0.07 m, mass 77 ± 10 kg) who were right-hand dominant and had bilaterally healthy shoulders with no current cervical pathology and no skin infection or shoulder lesion.
  
  
  
  External-rotation exercises without a towel roll (0° shoulder abduction) and with a towel roll (30° shoulder abduction) were performed in a standing and side-lying.
  
  
  
  Maximal voluntary isometric contraction for the infraspinatus, middle and posterior deltoid, and pectoralis major and external rotation in standing and side-lying with and without a towel roll were performed. Normalized average and peak surface EMG amplitude were compared between the towel conditions during standing and side-lying external rotation.
  
  
  
  Both infraspinatus and pectoralis major activity had no significant differences between the towel conditions in standing and side-lying (P > .05). In standing and side-lying, posterior-deltoid activity was significantly greater with a towel roll (P < .05). Middle-deltoid activity had no significant differences between the towel conditions in standing (P > .05). However, in side-lying, middle-deltoid activity was significantly lower with a towel roll (P < .05).
  
  
  
  Middle-deltoid activity decreased with a towel roll during side-lying exercises. More data are needed to determine if a towel roll could be used to potentially reduce superior glide during external-rotation exercises.
authors.affiliation: Human Performance Research Center, Brigham Young University, Provo, UT.
authors.forename: Kazuto
authors.initials: K
authors.lastname: Sakita
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Seeley
authors.forename: Joseph William
authors.initials: JW
authors.lastname: Myrer
authors.forename: J Ty
authors.initials: JT
authors.lastname: Hopkins
mesh_terms: D000328:Adult; D065187:Controlled Before-After Studies; D004576:Electromyography; D015444:Exercise; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D012399:Rotation; D012782:Shoulder / Q000502:physiology*; D055815:Young Adult