Unraveling Back Pain Chronicity: an EMG and EEG Study
Condition: Low Back Pain
MeSH terms: Back Pain; Low Back Pain
Study type: Interventional

Summary: 
      This study aims at examining the influence of both threat of experimentally induced pain and
      clinical low back pain (LBP) on trunk motor control on the one hand and brain activity
      related to movement preparation on the other hand. Therefore, 3 groups are studied: healthy
      controls, people with recurrent LBP, and people with chronic LBP. A comparison in
      electromyography (EMG) of the trunk muscles and electroencephalography (EEG) activity between
      the 3 groups will be made in 2 conditions: a control condition without experimental pain on 1
      test day, and a fear condition with experimental pain on another test day. In both conditions
      a motor control task will be performed and muscle and brain activity will be measured during
      each motor control task.

      It is hypothesised that motor control will be different between the 3 groups in both
      conditions, i.e. delayed trunk muscle onset in LBP groups compared with controls. With
      regards to the brain activity, it is expected that preparation for movement will also be
      delayed in the LBP groups. Furthermore, it is expected that the fear condition will entail
      differences in both EMG and EEG within each group.
    

Detailed description: 
      March 2017 - April 2018. 30 healthy participants, 30 recurrent and 30 chronic LBP patients
      all aged 18-45 and of both genders were tested for 2 conditions on 2 separate days, i.e. a
      control condition (C) on 1 test day; a fear (F) condition consisting out of threat (T) and no
      threat trials (NT) on another test day. The order of test days was randomized.

      1 block of 240 rapid arm movements (RAM) with the dominant arm was performed per condition,
      while electroencephalography (EEG) of the brain and surface electromyography (sEMG) of the
      Internal Oblique/Transversus Abdominis, External Oblique, Multifidus and Iliocostalis
      Lumborum pars Thoracis muscles were measured bilaterally. sEMG of the Anterior Deltoid muscle
      of the dominant arm was also measured. This RAM was used to induce an internal perturbation
      to the postural balance of subjects and is an often used task in the study of trunk motor
      control. Midway the RAM block, the participants got a short intermission of 90 seconds seated
      rest. Both conditions consisted of a warning cue (colored dot on a screen) followed by a go
      cue (arrow indicating either an upwards or downwards rapid arm movement) or a no-go cue
      ('STOP') and 12 seconds rest before the next trial. Harmless vibrotactile stimuli were always
      administered to the low back region during the appearance of the warning cue. During the C, a
      white warning cue was presented (safe cue), meaning that the RAM would never be accompanied
      by a painful electrocutaneous stimulus in that condition. During the F a safe (no threat) or
      a threatening warning cue could be presented (50-50%); in 25% of the trials after the
      threatening cue an electrocutaneous stimulus was given to the lower back region; the trials
      after the no threat cue were never accompanied with painful stimuli.

      The intensity of the electrocutaneous stimulus was self-determined by participants through a
      staircase paradigm and was administered by a digitimer system.

      At the beginning of each test day several questionnaires were also administered to control
      for psychological factors and physical activity, i.e. Central Sensitization Index (CSI),
      Hospital Anxiety and Depression Scale (HADS), Tampa Scale for Kinesiophobia (TSK), Pain
      Catastrophizing Scale (PCS), Pain Vigilance and Awareness Questionnaire (PVAQ), Roland-Morris
      Disability Questionnaire (RMDQ), International Physical Activity Questionnaire (IPAQ) and a
      general questionnaire regarding socio-demographic information and history of complaints.
      Furthermore, complaint specific questionnaires were also administered, but only for the
      clinical populations (RLBP and CLBP)

      Statistical analysis will be performed to assess whether and to what extent both threat and
      LBP might influence motor control as measured with EMG during RAM. Furthermore, the effect of
      both on cortical movement preparation and somatosensory processing will also be assessed
      based on the EEG measurements.
    

Intervention name(s): Rapid Arm Movements; Unpleasant stimulus; Vibrotactile stimulus
Intervention type(s): Behavioral; Device; Device
Intervention description(s): 240 trials of RAM in either a forward (50%) or backward (50%) shoulder flexion direction and back to neutral as fast as possible, with maintaining extension in the elbow. Visual cues (arrows) indicated the movement direction.; An unpleasant, but harmless, electrocutaneous stimulus is administered to the low back region in 25% of the threat trials during the fear condition. Due to a conditioning phase before testing, participants know to expect this stimulus after the presentation of a warning cue related to the fear trials (either pink or blue dot dependent on randomization).; In all trials, during the presentation of the warning cue, a vibrotactile stimulus is administered to the low back region. This stimulus is used to evoke somatosensory evoked potentials (SEP) measured with EEG during the movement-preparation phase.
Other intervention name(s): Electrocutaneous stimulus
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Each participant will perform both experimental conditions spread out over 2 test days in a randomized order. Between 2 test days a minimum of 5 days has to be present in order to ensure full recuperation from test day 1. Half of the participants will receive the control condition on test day 1 and the fear condition on day 2, the other half vice versa.
Masking: Single (Outcomes Assessor)
Primary purpose: Basic Science
Keywords: Sensorimotor control; Event-related potentials; Cortical movement preparation