title: Electromyographic Activity of Scapular Muscle Control in Free-Motion Exercise.
abstract: BACKGROUND
  The appropriate resistance intensity to prescribe for shoulder rehabilitative exercise is not completely known. Excessive activation of the deltoid and upper trapezius muscles could be counterproductive for scapulohumeral rhythm during humeral elevation.
  
  
  OBJECTIVE
  To identify the effects of different exercise intensities on the scapular muscles during a free-motion "robbery" exercise performed in different degrees of shoulder abduction in seated and standing positions.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Kinesiology Adapted Physical Education Laboratory.
  
  
  METHODS
  A total of 15 healthy male college students (age = 20.5 ± 2.2 years, height = 174.5 ± 5.3 cm, mass = 63.8 ± 6.0 kg).
  
  
  METHODS
  Participants performed 5 repetitions of a randomized exercise sequence of the robbery exercise in 2 body positions (seated, standing), 2 shoulder-abducted positions (W [20°], 90/90 [90°]) at 3 intensities (0%, 3%, and 7% body weight).
  
  
  METHODS
  Electromyographic (EMG) activity of the upper trapezius, lower trapezius, serratus anterior, anterior deltoid, and infraspinatus muscles of the upper extremity was collected. All EMG activities were normalized by the maximal voluntary isometric contraction of each corresponding muscle (%).
  
  
  RESULTS
  The serratus anterior, anterior deltoid, and infraspinatus EMG activities were greater at 7% body weight in the seated position compared with the standing position (P < .05). The EMG activities in all 5 muscles were greater in the 90/90 position than in the W position (P < .05).
  
  
  CONCLUSIONS
  Scapular muscle activity modulated relative to changes in body posture and resistance intensity. These findings will enable clinicians to prescribe the appropriate level of exercise intensity and positioning during shoulder rehabilitation.
authors.affiliation: Department of Kinesiology, San José State University, CA;
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Nakamura
authors.affiliation: Department of Kinesiology, San José State University, CA;
authors.forename: Masaaki
authors.initials: M
authors.lastname: Tsuruike
authors.affiliation: Physiotherapy Associates Scottsdale Sports Clinic, AZ.
authors.forename: Todd S
authors.initials: TS
authors.lastname: Ellenbecker
mesh_terms: D057645:Deltoid Muscle / Q000502:physiology; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D005081:Exercise Therapy; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D009068:Movement / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture; D017006:Rotator Cuff / Q000502:physiology; D012540:Scapula / Q000502:physiology*; D012782:Shoulder / Q000502:physiology*; D000070599:Shoulder Injuries; D064171:Superficial Back Muscles / Q000502:physiology; D055815:Young Adult
keywords: kinetic chain; resistance intensity; shoulder rehabilitation