Activity of the Rotator Cuff During Glenohumeral Mobilization
Condition: Shoulder Pain
MeSH terms: Shoulder Pain
Study type: Interventional

Summary: 
      Shoulder pain is one of the most common musculoskeletal conditions treated by physical
      therapists. One common treatment is passive glenohumeral joint accessory mobilization, which
      is the application of a therapist generated force to move the humeral head (ball) on the
      glenoid (socket) of the shoulder to improve motion and decrease pain. It is generally
      accepted that these mobilizations do not elicit active muscular contractions of the
      surrounding musculature. However, there is very little literature to support this assumption,
      and a preliminary PubMed search utilizing the terms "shoulder"," mobilization", and "EMG"
      returned zero relevant references. Therefore, the investigators plan to utilize surface
      electromyography (EMG), a non-invasive assessment tool, to objectively measure the activity
      of the rotator cuff muscles (the muscles that surround the shoulder and provide stability to
      the joint) during various grades(levels of force and amplitude of movement) of glenohumeral
      mobilization ( a standard of care treatment). It is also unknown if subjects pain levels
      impact the level of rotator cuff activity. To investigate these questions, the investigators
      will collect EMG data while performing mobilizations on a total of 20 subjects, divided into
      two groups: 10 pain free shoulders and 10 painful shoulders. Data analysis will then include
      descriptive analysis, estimates of effect size, and analysis for between group differences.

      The investigators hypothesize that there will be significant differences in muscular activity
      between groups related to the presence of shoulder pain.
    

Detailed description: 
      Following informed consent, all participants will be assessed in a private EMG lab setting.
      After exposing the posterior shoulder girdle, the areas of the upper trapezius,
      supraspinatus, and infraspinatus will be cleaned using a cloth alcohol prep pad, and the skin
      at the area of electrode placement will be vigorously abraded for 5 seconds. A previously
      calibrated (per Delsys system protocol) Delsys mini-wireless electrode will then be placed at
      the appropriate location over each muscle as described by Criswell. These electrodes will be
      securely taped in place using specialized tape as specified by the manufacturer.

      Once electrode placement is complete, each participant will first undergo a standardizing
      reference contraction of each muscle group. For the upper trapezius, this will consist of 1)
      a 9 second shrug,2) 9 second elevation of the arm to 90 degrees in the empty can position,
      and 3) a side lying external rotation of the shoulder to 90 degrees. The middle 3 seconds of
      each trial will be used to record the average electrical activity of each muscle during
      voluntary contraction.

      Participants will then be placed supine on a standard plinth. The investigators will then
      proceed to provide a mobilizing force to the subject's glenohumeral joints. Each of two
      investigators will, in sequence perform a 15 second longitudinal distraction, followed by a
      15 second posteriorly directed glenohumeral glide with the shoulder placed in the open pack
      resting position (~50 degrees abduction, slight horizontal adduction, external rotation). The
      middle 5 seconds will be captured for mean electrical activity at each of the three
      previously identified muscles. Following completion of the mobilizations by the second
      investigator, the electrodes will be removed, and the subject's participation will be
      complete.

      Data analysis will include basic subject demographics such as age, gender, and handedness.
      Tests of between group difference will be analyzed for each mobilization and tester
      condition. Data will be analyzed comparing mean EMG values during mobilization compared to
      the active contraction using the reference voluntary contraction (RVC) method, as this has
      been shown be a more accurate comparator for low levels of muscle activity.
    

Intervention name(s): Glenohumeral mobilization
Intervention type(s): Other
Intervention description(s): Participants will then be placed supine on a standard plinth. The investigators will then proceed to provide a mobilizing force to the participant's glenohumeral joints. Each of two investigators will, in sequence perform a 15 second longitudinal distraction, followed by a 15 second posteriorly directed glenohumeral glide with the shoulder placed in the open pack resting position (~50 degrees abduction, slight horizontal adduction, external rotation).
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: Manual therapy