Research Article

Experimental Brain Research

, Volume 151, Issue 2, pp 262-271

First online:

Experimental muscle pain changes feedforward postural responses of the trunk muscles

  • Paul W. HodgesAffiliated withDepartment of Physiotherapy, The University of QueenslandPrince of Wales Medical Research Institute and University of New South Wales Email author 
  • , G. Lorimer MoseleyAffiliated withDepartment of Physiotherapy, The University of QueenslandDepartment of Physiotherapy, Royal Brisbane Hospital
  • , Anna GabrielssonAffiliated withDepartment of Community Medicine and Rehabilitation Physiotherapy, Umeå University
  • , Simon C. GandeviaAffiliated withPrince of Wales Medical Research Institute and University of New South Wales

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Abstract

Many studies have identified changes in trunk muscle recruitment in clinical low back pain (LBP). However, due to the heterogeneity of the LBP population these changes have been variable and it has been impossible to identify a cause-effect relationship. Several studies have identified a consistent change in the feedforward postural response of transversus abdominis (TrA), the deepest abdominal muscle, in association with arm movements in chronic LBP. This study aimed to determine whether the feedforward recruitment of the trunk muscles in a postural task could be altered by acute experimentally induced LBP. Electromyographic (EMG) recordings of the abdominal and paraspinal muscles were made during arm movements in a control trial, following the injection of isotonic (non-painful) and hypertonic (painful) saline into the longissimus muscle at L4, and during a 1-h follow-up. Movements included rapid arm flexion in response to a light and repetitive arm flexion-extension. Temporal and spatial EMG parameters were measured. The onset and amplitude of EMG of most muscles was changed in a variable manner during the period of experimentally induced pain. However, across movement trials and subjects the activation of TrA was consistently reduced in amplitude or delayed. Analyses in the time and frequency domain were used to confirm these findings. The results suggest that acute experimentally induced pain may affect feedforward postural activity of the trunk muscles. Although the response was variable, pain produced differential changes in the motor control of the trunk muscles, with consistent impairment of TrA activity.

Keywords

Motor control Experimental pain Postural control Trunk muscles Stability