title: Low back pain suppresses preparatory and triggered upper-limb activation after sudden upper-limb loading.
abstract: METHODS
  A cross-sectional comparative study between healthy controls and patients with chronic low back pain (LBP).
  
  
  OBJECTIVE
  To assess the effect of chronic LBP on biceps brachii muscle activation during sudden upper-limb loading.
  
  
  BACKGROUND
  Chronic LBP is related to altered trunk muscle function. However, it is not known if these changes are also found in upper-limb function, indicating a general effect.
  
  
  METHODS
  Surface electromyographic recordings were made from the biceps brachii bilaterally from 22 control subjects without chronic LBP and 29 patients with chronic LBP. Electromyography was recorded during expected and unexpected limb loading, with the activation pattern recorded for analysis at 150 milliseconds before loading, and 3 consecutive 50 milliseconds periods following loading. RESULTS.: Chronic LBP patients had decreased biceps brachii activation before expected perturbation (P = 0.035) and during the third 50-millisecond period (from 100 to 150 milliseconds) after unexpected perturbation (P = 0.010). During the first 2, 50-millisecond periods (from 0 to 100 milliseconds) after the perturbation, the activation was similar.
  
  
  CONCLUSIONS
  Chronic LBP did not affect reflex activation of biceps brachii muscles but decreased preparatory and triggered reactions. The finding indicates that back pain may disturb higher level information processing in motor control.
authors.affiliation: Department of Neurosurgery, Kuopio University Hospital, Kuopio, Finland. ville.leinonen@kuh.fi
authors.forename: Ville
authors.initials: V
authors.lastname: Leinonen
authors.forename: Minna
authors.initials: M
authors.lastname: Airaksinen
authors.forename: Simo
authors.initials: S
authors.lastname: Taimela
authors.forename: Markku
authors.initials: M
authors.lastname: Kankaanpää
authors.forename: Ari
authors.initials: A
authors.lastname: Kukka
authors.forename: Taina
authors.initials: T
authors.lastname: Koivisto
authors.forename: Olavi
authors.initials: O
authors.lastname: Airaksinen
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D016022:Case-Control Studies; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology*; D010147:Pain Measurement; D011597:Psychomotor Performance; D011930:Reaction Time; D012018:Reflex; D013997:Time Factors; D034941:Upper Extremity / Q000503:physiopathology; D016474:Weight-Bearing