Adaptation of the Motor System to Experimental Pain
Condition: Kinesiophobia; Pain, Acute
MeSH terms: Acute Pain; Kinesiophobia
Study type: Interventional

Summary: 
      This study aims to measure the impact of an experimental pain on electromyography, kinematics
      of motion and motor cortical excitability.
    

Detailed description: 
      The main objective of this study will be to determine if the influence of pain on the
      corticospinal excitability of M1 (via the slopes of the I/O curves) is dependent on the level
      of kinesiophobia.

      The secondary objectives are firstly to measure the modifications induced by experimental
      pain on muscle activation synergies. Secondly, to measure the modifications induced by an
      experimental pain on the kinematics of the movement during a pointing task during the
      application of the pain. Finally, to determine if an experimental pain modifies the
      electrical activity of muscles located in the painful area during a pointing movement and the
      value of the cumulative sums (CUSUMs).

      Inclusion Criteria:

        -  Males and females of legal age.

        -  Healthy subjects (who do not have self-reported neurological disorders)

        -  Subjects who have signed an informed consent (who have a good command of French)

        -  Subjects who are affiliated with or benefit from a social security plan

      Criteria for non-inclusion:

        -  Psychiatric history obtained by physician questioning: individuals with mental
           retardation or severe impairment of cognitive, behavioral, or affective functions
           precluding understanding the protocol and signing informed consent

        -  Neurological history (epilepsy, stroke, surgeries performed on the brain or spinal cord,
           and history of neurological diseases affecting motor skills and sensation)

        -  Subjects who are unable to receive informed information (dementia, hearing problems,
           poor French proficiency, etc.)

        -  Contraindications to MST (epilepsy, intracranial metal foreign bodies, hearing aids or
           cochlear implants)

        -  Taking psychotropic medications

        -  Persons under guardianship or conservatorship

        -  Pregnant and nursing women

        -  Subjects with pacemakers

      Assessment before pain induction:

      ► Corticospinal excitability of M1: The TMS will be used to establish the input-output (I/O)
      curves. Stimuli of variable intensity between the threshold value (or MT for motor threshold)
      and the maximum will be delivered. In total, about ten stimulation intensities will be
      tested, and for each stimulation intensity, ten stimuli will be delivered, allowing then to
      calculate the average of the MEPs in order to draw the I/O curves of each participant. As
      recalled by national and international recommendations, TMS is a noninvasive and painless
      technique whose use in the scientific literature is extremely abundant.

      ► Pointing task: The participant will be seated on a chair facing a table so that his or her
      dominant forearm rests on the table. Markers will be placed at the table and chair legs as
      well as on the table, corresponding to the two support points of the elbow and the index
      finger, in order to standardize the starting position. The index finger should be positioned
      on the midline. The maximum amplitude of the pointing movement on the median line will be
      determined and then the target of the pointing movement will be placed at 80% of this maximum
      distance. The investigators chose a single target so that reaction time would not be impacted
      by too much cognitive load. The investigator will tell the participant to stand by, and then,
      within 4 to 10 seconds, an audible signal ("beep") will indicate to the subject that he/she
      should perform the pointing movement. Then the subject will return to the starting position
      at rest, and the procedure will repeat after a 4-10 second pause. For each evaluation
      session, 30 pointing movements reaching the target will be performed, the first three of
      which will not be counted (familiarization). The kinematic parameters of the pointing
      movements will be recorded using a 3D motion analysis video system. The markers will be
      placed on C7, and on the dominant side on the acromion, the olecranon, the dorsal aspect of
      the wrist and on the distal phalanx of the index finger.

      ► Muscle activation synergies: To measure muscle activations during this pointing task,
      surface EMG recording of the anterior deltoid and upper trapezius muscles will be performed
      on the dominant upper limb using a wireless collection system. Raw data of kinematic and EMG
      parameters will be stored and processed offline. Trials where the reaction time is less than
      100ms will be excluded from the analysis.

      Assessment during experimental pain:

      ► Experimental Pain Induction: In this study, the application of a capsaicin 1% patch will be
      performed at the participant's dominant delto-pectoral groove (between the shoulder stump and
      pectoral) on intact, non-irritated, dry skin to generate experimental pain. For the purposes
      of this study, the investigators will remove this patch before the recommended application
      time (60 minutes) in order to generate a limited pain of 3 to 5/10 on a visual analog scale
      (VAS).

      ► Completion of the EKT-CF questionnaire: During the time of onset and stabilization of pain
      induced by the capsaicin 1% patch, the participant will be asked to complete the EKT-CF
      questionnaire in computerized form. An evaluation of the pain will be made at this time using
      a VAS and the value will be noted.

      ► TMS, Pointing and muscles activation: Once the pain has settled and stabilized, TMS,
      surface EMG and kinematic measurements will be performed again in the same way as described
      previously. The similar optimum stimulation point used for the TMS will be rigorously
      stimulated using the coordinates recorded previously.

      The duration of the experimental session is estimated at 2h30min, distributed as follows:
      Information, eligibility and consent collection: 15 minutes; preparation of the experiment
      (installation of the electrodes, setting of the devices: 45 minutes; recordings: 90 minutes).
    

Intervention name(s): Experimental pain
Intervention type(s): Other
Intervention description(s): Experimental pain will be induced by capsaicin 1% on intact, non-irritated and dry shoulder's skin. For the purposes of this study, we will remove this patch before the recommended application time in order to generate a pain. The participant will be seated on a chair facing a table so that his or her dominant forearm rests on the table. Markers will be placed at the table and chair legs as well as on the table, corresponding to the two support points of the elbow and the index finger, in order to standardize the starting position. The target of the pointing movement will be placed at 80% of this maximum distance. The investigator will tell the participant to stand by, and then, within 4 to 10 seconds, an audible signal will indicate to the subject that he/she should perform the pointing movement. The procedure will repeat after a 4-10 second pause. For each session, 30 pointing movements reaching the target will be performed.
Intervention model: Single Group Assignment
Intervention model description: Cross sectional study
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: kinesiophobia; experimental pain; corticospinal excitability; motor control; CUSOM