title: The effect of experimental neck pain on pressure pain sensitivity and axioscapular motor control.
abstract: Clinical neck pain affects pain sensitivity and coordination of neck muscles, but the impact on the shoulder muscles is unclear. This study investigated the effect of experimental neck pain on the activity of the axioscapular muscles during arm movements and changes in pain sensitivity. Experimental neck pain was induced in 24 healthy volunteers by injecting hypertonic saline into the splenius capitis. Isotonic saline was injected as control. Before, during, and after injections, electromyography was recorded bilaterally from 8 muscles during standardized arm movements (140° scapular plane elevation), and the root mean square amplitude was extracted. Likewise, pressure pain thresholds were assessed bilaterally on 3 sites. The root mean square electromyography was decreased for the ipsilateral upper trapezius (P < .01) and increased for the ipsilateral middle deltoid (P < .03) during upward movements. The root mean square electromyography was reduced for the ipsilateral upper trapezius (P < .01) during downward movement, whereas an increase was recorded in the contralateral external oblique (P < .02). At the injection site, the pressure pain threshold increased during pain compared with the post condition (5 minutes after potential pain had subsided; P < .03). In this study, trunk and axioscapular muscle activities were reorganized in response to localized and referred pain evoked by hypertonic saline injection into an intrinsic neck muscle with no direct attachments to the trunk or shoulder girdle.
  
  
  CONCLUSIONS
  Reorganized activity of the axioscapular muscles has been shown previously in neck pain patients and is believed to happen during the transition from acute to chronic pain. The present study demonstrates for the first time that such reorganization may happen acutely, adding to our understanding of the effects of acute neck pain.
authors: Laboratory for Musculoskeletal Pain and Motor Control, Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors: Steffan W
authors: SW
authors: Christensen
authors: Laboratory for Musculoskeletal Pain and Motor Control, Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors: Rogerio P
authors: RP
authors: Hirata
authors: Laboratory for Musculoskeletal Pain and Motor Control, Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark. Electronic address: tgn@hst.aau.dk.
authors: Thomas
authors: T
authors: Graven-Nielsen
mesh_terms: D000328:Adult; D001132:Arm; D018592:Cross-Over Studies; D004576:Electromyography; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D019547:Neck Pain / Q000503:physiopathology*; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology*; D011312:Pressure; D011897:Random Allocation; D012462:Saline Solution, Hypertonic; D012782:Shoulder / Q000503:physiopathology; D016037:Single-Blind Method; D013997:Time Factors
chemical_list: D012462:Saline Solution, Hypertonic
keywords: Neck; axioscapular; experimental; pain; shoulder