title: Experimental pain responses support peripheral and central sensitization in patients with unilateral shoulder pain.
abstract: OBJECTIVE
  The aims of this study were to (1) examine the pattern of experimental pain responses in the affected and nonaffected extremities in patients with shoulder pain and (2) explore the intraindividual association between sensitization states derived from experimental pain testing.
  
  
  METHODS
  Experimental pain responses from 58 patients with shoulder pain (17 women, aged 18 to 52 y) were compared with those from 56 age-matched and sex-matched pain-free volunteers (16 women, aged 21 to 58 y). Experimental pain responses included pressure pain threshold (PPT), thermal pain threshold and tolerance, and suprathreshold heat pain response. Comparisons were made between the affected and nonaffected extremities of clinical participants and the average response of extremities in control participants. Peripheral and central sensitization indexes were computed for clinical participants using standardized scores and percentile cutoffs on the basis of the data from the control sample. Experimental pain responses in clinical participants observed beyond the 25th and 75th percentile of control sample responses were used for investigation of intraindividual association of sensitization states.
  
  
  RESULTS
  PPT at the acromion and masseter on the affected side of clinical participants were diminished compared with that on their nonaffected side (P<0.015). Bilateral sensitivity in clinical participants was noted for PPT at the acromion and suprathreshold heat pain response (P<0.015). Peripheral and central sensitization indexes demonstrated that individuals with shoulder pain present with variable patterns of peripheral and central sensitization.
  
  
  CONCLUSIONS
  Collectively, experimental pain responses supported peripheral and central sensitization in response to pressure and thermal stimuli. No clear association was made between individuals exhibiting peripheral or central sensitization, thus suggesting heterogeneity in pain processing in this clinical population.
authors.affiliation: *Department of Physical Therapy, College of Public Health and Health Professions ‡Center for Pain Research and Behavioral Health, University of Florida, FL †Department of Applied Medicine and Rehabilitation, Indiana State University, IN.
authors.forename: Rogelio A
authors.initials: RA
authors.lastname: Coronado
authors.forename: Corey B
authors.initials: CB
authors.lastname: Simon
authors.forename: Carolina
authors.initials: C
authors.lastname: Valencia
authors.forename: Steven Z
authors.initials: SZ
authors.lastname: George
mesh_terms: D000293:Adolescent; D000328:Adult; D002452:Cell Count; D059333:Central Nervous System Sensitization / Q000502:physiology*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D059352:Musculoskeletal Pain / Q000503:physiopathology; D009483:Neuropsychological Tests; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology; D017933:Peripheral Nervous System / Q000503:physiopathology*; D011312:Pressure; D020069:Shoulder Pain / Q000503:physiopathology*; D012959:Socioeconomic Factors; D055815:Young Adult