title: Attenuated skin blood flow response to nociceptive stimulation of latent myofascial trigger points.
abstract: OBJECTIVE
  To investigate the effect of painful stimulation of latent myofascial trigger points (MTrPs) on skin blood flow and to evaluate the relative sensitivity of laser Doppler flowmetry (LDF) and thermography in the measurement of skin blood flow.
  
  
  METHODS
  Painful stimulation was obtained by a bolus injection of glutamate (0.1mL, 0.5M) into a latent MTrP located in the right or left brachioradialis muscles. A bolus of glutamate injection into a non-MTrP served as control. Pain intensity (visual analog scale [VAS]) was assessed after glutamate injection. Pressure pain threshold (PPT) was recorded bilaterally in the brachioradialis muscle before and after glutamate-induced pain. Skin blood flow and surface skin temperature were measured bilaterally in the forearms before, during, and after glutamate-induced pain with LDF and thermography.
  
  
  METHODS
  A biomedical research facility.
  
  
  METHODS
  Fifteen healthy volunteer subjects.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  VAS, PPT, skin blood flow, and surface skin temperature.
  
  
  RESULTS
  Glutamate injection into latent MTrPs induced higher pain intensity (F=7.16; P<.05) and lower PPT (F=11.41, P<.005) than into non-MTrPs. Glutamate injection into non-MTrPs increased skin blood flow bilaterally in the forearms, but skin blood flow after glutamate injection into latent MTrPs was significantly less increased at the local injection area or decreased at distant areas compared with non-MTrPs (all P<.05). Skin temperature was not affected after glutamate injection into either latent MTrPs or non-MTrPs (all P>.05).
  
  
  CONCLUSIONS
  The present study demonstrated an attenuated skin blood flow response after painful stimulation of latent MTrPs compared with non-MTrPs, suggesting increased sympathetic vasoconstriction activity at latent MTrPs. Additionally, LDF was more sensitive than thermography in the detection of the changes in skin blood flow after intramuscular nociceptive stimulation.
authors.affiliation: Laboratory for Experimental Pain Research, Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Hong-You
authors.initials: HY
authors.lastname: Ge
authors.forename: Shou-Wei
authors.initials: SW
authors.lastname: Yue
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Kimura
authors.forename: Lars
authors.initials: L
authors.lastname: Arendt-Nielsen
mesh_terms: D000328:Adult; D005260:Female; D018698:Glutamic Acid; D006801:Humans; D008297:Male; D009209:Myofascial Pain Syndromes / Q000503:physiopathology*; D010146:Pain / Q000139:chemically induced* / Q000503:physiopathology*; D010147:Pain Measurement; D017288:Pain Threshold; D012867:Skin / Q000098:blood supply*; D012881:Skin Temperature; D013268:Stimulation, Chemical
chemical_list: D018698:Glutamic Acid