Neck muscle fatigue and postural control in patients with whiplash injury.
OBJECTIVE
To examine if patients with whiplash injury show identifiable increases in neck muscle fatigability and associated increase in postural body sway after contractions of dorsal neck muscles, and if physiotherapy treatment reduces these effects.


METHODS
Sway was measured during stance in 13 patients before and after 5 min of isometric dorsal neck muscle contractions and after recovery, pre- and post-physiotherapy, using a force platform. Amplitude and median frequency of neck muscle EMG were calculated during the contracting period. After each stance trial, patients gave a subjective score of sway.


RESULTS
Pre-treatment, seven patients showed EMG signs of fatigue (increases in amplitude, decreases in median frequency) and increases in sway (eyes closed) after contractions. The other patients showed neither fatigue nor increased sway. Post-treatment, no signs of fatigue or imbalance were recorded in all patients, for the same levels of muscle contraction.


CONCLUSIONS
As in normal human subjects, increases in sway are associated with signs of neck muscle fatigue in some whiplash injury patients. Physiotherapy decreases the susceptibility to fatigue of neck muscles and is an effective choice of treatment of subjective instability and sway.


CONCLUSIONS
This study demonstrates a pathophysiological link between neck muscle fatigue and impaired postural control, and also that physiotherapy can relieve symptoms and signs of impaired neck muscle function by reducing muscle fatigability.
Stapley
Paul J
PJ
Centro Studi Attività Motorie, Fondazione Salvatore Maugeri (IRCCS), Istituto Scientifico di Pavia, Via Ferrata 8, 27100 Pavia, Italy.
Beretta
Maria Vittoria
MV
Dalla Toffola
Elena
E
Schieppati
Marco
M
D000328:Adult; D000704:Analysis of Variance; D004244:Dizziness / Q000209:etiology; D004576:Electromyography / Q000379:methods; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology*; D009334:Neck Muscles / Q000503:physiopathology*; D019547:Neck Pain / Q000209:etiology; D011187:Posture / Q000502:physiology*; D011434:Proprioception / Q000502:physiology; D014911:Whiplash Injuries / Q000150:complications / Q000503:physiopathology*