A Comparison of Electromyographic Activity & Glenohumeral Motion
Condition: Orthopedic Disorder
MeSH terms: Musculoskeletal Diseases
Study type: Interventional

Summary: 
      Pain pressure measurements, fine wire EMG and real time imaging ultrasound will be used to
      determine the relationships between motion, pain perception, and mobility in the glenohumeral
      joint. Muscle activity, joint motion, and pain will be measured pre-post randomized
      interventions to determine the response to various physical therapy techniques.
    

Detailed description: 
      To achieve the study aims, 88 adults (44 controls, 44 with stiff shoulders) between the ages
      of 18-65 will be recruited. The investigators will apply a protocol based on current evidence
      for effectiveness of mobilizations (4 bouts of 30 sec, oscillatory gr III mobilization @1 Hz
      vs. 4 bouts of 30 seconds, static gr III mobilization), with interventions determined by
      randomized blocked assignment. Before and after the intervention, the investigators will
      assess levels of EMG activity of the posterior rotator cuff during a posterior glide, the
      force required for the mobilization to reach end range stretch, the amount of humeral head
      translation on the glenoid via US, and pain pressure thresholds (PPT). The data collected
      will allow investigators to determine the mechanisms involved in range of motion (ROM)
      changes and hypoalgesia produced by glenohumeral (GH) joint mobilization in both normal and
      stiff shoulders by evaluating the main and interaction effects of: the type of mobilization
      (static vs oscillatory), the magnitude of joint translation via imaging ultrasound, the EMG
      response of the supraspinatus and infraspinatus muscles, and changes in local and central
      pain processing observed via PPT testing. These data will allow investigators to evaluate
      whether motion improvements occur due to mechanical factors (stretch of the capsule observed
      via change in translation), neurophysiologic factors (change in translation associated with
      reduction in EMG activity), or both. Concurrent measurements of pain processing by the
      nervous system (local and central mechanisms) will allow evaluation of whether changes in
      pain processing occur following oscillatory movements, sustained movements, or both. This
      information will result in improved understanding of the mechanisms of action of joint
      mobilization, determination of the efficacy of various modes of mobilization to improve joint
      translation, and determination of the efficacy of various modes of mobilization to decrease
      pain.

      Data analysis:

      All data will be analyzed in aggregate form using quantitative statistics. Descriptive
      statistics will be utilized for demographic data including age, height, weight, gender,
      handedness, and side of intervention.

      Groups will be measured using tests of difference based on group assignments (normal vs stiff
      shoulder; sustained vs oscillatory mobilization) comparing peak and root mean squared EMG
      activity, pain pressure thresholds, force of mobilization, and amount of translation measured
      via US as well as analysis of interaction effects.

      All data will be analyzed using an intention to treat model, and any missing data points were
      replaced using imputation via means of the group.

      All outliers, defined as data points beyond the 95th percentile and identified as outliers
      during analysis in SPSS, will be Winsorized to minimize the effect of potentially spurious
      outliers via replacement with the highest non-outlier obtained value for the group.

      Descriptive statistics including means, ranges and standard deviations will be assessed for
      each group condition.

      Data will be assessed for the required assumptions for parametric testing/ Analysis of
      variance(ANOVA) including Mauchly's test of sphericity and the Shapiro-Wilk test of
      normality. Data not meeting the required assumptions will be assessed with the appropriate
      non-parametric equivalent test.

      Aim 1 will investigate the relationships and within and between group differences in rotator
      cuff activity (EMG) and posterior glide mobility and mobilization force in the glenohumeral
      joint in individuals with stiff and normal shoulders based on joint mobilization type.

      To analyze within subjects main effects, interaction effects, and second order interaction
      effects of group and mobilization condition on the DV, three-way between-between-within mixed
      ANOVAs will be used.

      IV: shoulder condition stiff vs normal; oscillation vs static posterior glide; time.

      X Repeated measure Dependent variables(DV)s: EMG, US translation, force In the presence of
      significant three way interactions, post hoc testing to determine simple two way interaction
      effects will be performed using separate two way ANOVAs Univariate testing will be utilized
      to determine the presence of simple main effects.

      Post hoc analysis will utilize pairwise comparisons in the presence of significant main
      effects. Bonferroni correction will be utilized due to multiple tests, with comparisons
      within each simple-simple main effect considered a family of comparisons.

      To investigate the relationships between rotator cuff activity (EMG) and posterior glide
      mobility in individuals with stiff and normal shoulders, point bi-serial correlation will be
      utilized to assess for meaningful relationships between the following variables:

      Mobilization condition x change in EMG, US, force Group (stiff vs control) assignment x
      change in EMG, US, force Aim 2 will investigate the within and between group differences and
      relationships between changes in PPT and type of mobilization (static, oscillatory) in
      individuals with stiff and normal shoulders.

      Between group differences will be assessed via ind. t-tests, using the dichotomous
      independent variables (IV) static vs. oscillatory mobilization, and the DV of PPT measures.

      Within group differences will be assessed via paired t-tests, using the dichotomous IV static
      vs. oscillatory mobilization, and the DV of PPT measures.
    

Intervention name(s): glenohumeral mobilization-oscillation; glenohumeral mobilization-sustained
Intervention type(s): Other; Other
Intervention description(s): posterior glide mobilizations oscillated at 1hz, 4 x 30 seconds; posterior glide mobilization, sustained 4 x 30 seconds
Other intervention name(s): musculoskeletal manipulation; musculoskeletal manipulation
Allocation: Randomized
Intervention model: Factorial Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: shoulder; mobilization; electromyography; imaging ultrasound