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Table 2 Variables, outcome measures and methods of analysis

From: The Strengthening Exercises in Shoulder Impingement trial (The SExSI-trial) investigating the effectiveness of a simple add-on shoulder strengthening exercise programme in patients with long-lasting subacromial impingement syndrome: Study protocol for a pragmatic, assessor blinded, parallel-group, randomised, controlled trial

Variable/outcome Hypothesis Outcome measure Methods of analysis
Primary outcome Intervention improved outcome   
  SPADI change Δt0-t3   Score 0–100 (continuous) cLMM
Secondary outcomes Intervention improved outcome   
  Abd. MVC change Δt0-t3   Nm/kg (continuous) cLMM
  Ext. rot. MVC change Δt0-t3   Nm/kg (continuous) cLMM
  Abd. total ROM change Δt0-t3   Degrees (continuous) cLMM
  Pain last week change Δt0-t3   NRS 0–10 (continuous) cLMM
  EQ-5D change Δt0-t3   Index value (continuous) cLMM
  Global impression of change, at t3   % much improved/fully recovered (binary) χ2 test
 Pain sensitisation Δt1-t3    
  Temporal Summation of Pain   VAS increase (continuous) cLMM
  Conditioned Pain Modulation   kPa increase (continuous) cLMM
  Pain Pressure Threshold   kPa (continuous) cLMM
 Scapular involvement    
  SAT   % positive (binary) χ2 test
  SDT   % positive (binary) χ2 test
Subgroup analyses    
  Scapula involvement (SAT and SDT yes/no) Dysfunction modifies the effect of intervention SPADI score, abduction MVC and external rotation MVC (continuous) cLMM with interaction term
  Central sensitisation (TS and CPM high vs. low) CS modifies the effect of intervention SPADI score, abduction MVC and external rotation MVC (continuous) cLMM with interaction term
Sensitivity analyses Intervention improved outcome Primary outcome  
  Per protocol analysis    cLMM
  Adjusting for baseline    cLMM
  1. cLMM constrained linear mixed model, EQ-5D EuroQol 5D-3 L, MVC maximum voluntary contraction, Nm/kg Newton meter per kilo body weight, ROM range of movement, SAT scapula dysfunction, SDT scapula dyskinesia, SPADI Shoulder Pain and Disability Index, VAS visual analogue scale