Relation Between Temporal Summation and Fatigue
Condition: Central Sensitisation; Elbow Pain; Fatigue
MeSH terms: Fatigue
Study type: Interventional

Summary: 
      Central sensitization (CS) is a common feature in chronic musculoskeletal pain conditions
      including rheumatoid arthritis, chronic whiplash syndrome, fibromyalgia, temporomandibular
      joint disorders, low back pain and lateral elbow pain. CS is defined as "an amplification of
      neural signaling within the central nervous system that elicits pain hypersensitivity".
      Clinical signs are allodynia, hyperalgesia and widespread pain, originating from the enhanced
      activity of central nervous system to peripheral afferent input from unimodal and polymodal
      receptors.

      CS not only induces abnormal pain processing, it may also lead to motor performance
      dysfunction in chronic pain population. CS induce cortical reorganization including changes
      in gray matter, cortical representation and cortical excitability both in motor and
      somatosensory cortex. This process ultimately generates sensorimotor conflict that described
      as a mismatch between motor intention and sensory feedback, and may directly effect on motor
      performance. The structural changes in basal ganglia and reduced GABAergic activity in the
      motor cortex contribute to the alteration of the motor performance. It has been known that CS
      and fatigue, another indicator of the motor performance, has a bidirectional effect and
      fatigue is predicted by CS, independently of the presence of pain. CS affect fatigue via
      causing disrupted reward process, increased effort and pain expactation.

      The increased cervical spine hypersensitivity in patients with LEP even if there is no
      accompanied neck or upper limb pain may also indicate of the fatigue as pain does not always
      suggest an injury and biomechanical damage to a tissue does not always suggest that an
      individual will experience pain. If neck muscle fatigue is effected by central sensitization
      in patients with LEP, it can be important to develop therapeutic strategies to prevent neck
      muscle fatigue as there is a relationship between fatigue and increased risk of injury.
      Despite the fact that central sensitization effect on neck pain has been well documented in
      patients with LEP, its role on fatigue had not gain enough clinical and research attention.
      To know about central sensitization effect on motor performance can also be useful for
      determine subgroup of population who have central sensitization. However, it is unknown
      whether remote body endurance alteration occur in lateral elbow pain or not.
    

Detailed description: 
      EMG assessment Electrode Placement Before electrode placement, the skin will be cleaned with
      alcohol to reduce skin impedance.

      Sternocleidomastoid Muscle (SCM) Electrode Placement Electrodes will be placed to the the
      sternal head of the SCM while participants were sitting in a erect position. A line will be
      drawn from the sternal notch to the mastoid process and marked at 1/3 of the distance from
      the sternal notch. Electrodes initially will placed adjacent to the this point with 20 mm
      apart and over the muscle belly based on the muscle palpation during manually resisted neck
      flexion contractions. This location is anticipated to place between the innervation zone and
      the tendon. In supine, the head will be placed in a neutral anatomic position that
      craniocervical and cervical spine is in a mid position. It will be ensured visually by
      examiner that cervical spine is in the neutral position which means from the middle of the
      subject's forehead to the middle of the chin is horizontal and a line bisecting the neck
      longitudinally is parallel to the treatment plinth. Participants will asked to completely
      relax in this position. For normalization, isometric neck flexor contraction will be carried
      out in supine position via applying manual resistance on frontal region by gradually
      increasing force that reached maximum force level in 2 second and then contracted maximally
      for 5 second. This procedure will be repeated 3 times with a 30 second time interval.

      Upper Trapezius (UT) Muscle Electrode Placement Electrodes will be attached 20% laterally to
      the midpoint between the dorsal processes of C4 and the posterior lateral third of the
      clavicle. For normalization, manual resistance will be given neck extensor while participant
      lying in prone position. Contraction will be lasted 5 second for 3 times with 30 interval.

      After electrode placement, a 5 seconds rest recording will be performed for eliminating basal
      noise from recording. During the endurance test, participants will asked not to cough, laugh
      or talk and head position will be controlled by inclinometer adapted to EMG system.
      Participants will be given 3 minutes resting time between neck flexor/extensor endurance
      tests for the experimental group.

      Neck Flexor Endurance Test An examiner will place her hand under the occiput of the
      participant, while the participant is lying in supine position with the knees bend and the
      arms resting on the abdomen. Cranicervical flexion will be taught to the participants. For
      this, participants will asked to place tongue on roof of the mouth, with lips together and
      teeth slightly apart while cervical spine is in neutral position. Participants will not be
      allowed to open mouth during the test. Participants will be requested to perform gentle head
      nodding as if saying "yes" via sliding head in caudal and cephalic directions on the bed and
      concentrate feeling of back of the head. After learning of the craniocervical flexion, the
      participant will be requested to head off from the examiners hand (approximately 2.5 cm from
      the plint) vhile maintaining the craniocervical flexion and then sustain this position as
      long as possible. The holding time will be recorded with a stopwatch. The test will be ended
      once the participant is unable to hold their head in a correct position that chances occur
      more than 5 degree for more than one second, can no longer maintain craniocervical flexion or
      head position due to fatigue.

      Neck Extensor Endurance Test Participants will be asked to lie in a prone position
      maintaining thoracal extension with a strap at the level of T6, arms in their side and head
      is end of the plinth. The subject's head and neck will be positioned in a comfortable neutral
      position with the chin retracted. 2 kg weight will be placed around the participants head.
      Participants will be asked to sustain this position as long as possible after removing
      support from the head. The test will be ended when the participant can no longer sustain a
      correct position or when the head position changes more than 5 degrees. The holding time will
      be recorded with a stopwatch.

      Experimental group:

      Experimental pain induction: Temporal Summation Then participants will be asked to seat in a
      comfortable position placing their volar faces of the tested dominant arm in elbow flexion on
      a table during the experiment. The tested area will be marked with a pen to apply every
      stimulus in the same place.

      Temporal summation will be evoked in a predetermined area:

        1. ECRL muscle origin: Distal humerus supracondylar ridge;

        2. ECRB muscle belly: identified with resisted radial wrist flexion

        3. Brachioradialis: 2 cm distal from in the middle of the line extend from lateral
           epicondyle to middle of the fossa cubiti via identifying resisted elbow flexion in 90°
           elbow flexion and wrist in neutral position Pressure pain thresholds (PPTs) will be
           identified two times with a 30 s interval for each predetermined area via applying
           circular probe in a perpendicular direction with an increasing pressure at a rate of
           approximately 1 kg/s. PPTs will be recorded when the sensation of the mechanical
           pressure stimulus changes into the first painful sensation. The average of two
           measurements will be used as a PPTs value. Temporal summation was induced two minutes
           after last PPTs was recorded. To evoke temporal summation at the lateral elbow, the
           probe will be applied with the pressure of the predefined PPT threshold at the rate of
           approximately 2 kg/s where it will be maintained for 1 s before being released with a 1
           s interstimulus interval (ISI). This procedure will be repeated 10 times in each
           predetermined area. Pain intensity will be asked to participants at first, fifth and
           tenth pulse using a Visual Analog Scale range from "0 indicate no pain" to "10 most
           painful".

      Placebo Group: After flexor and extensor endurance test, participants will be provided 20
      minutes resting time. PPTs value will be evaluted once in each predetermined region with a 30
      s interval.

      Before PPTs assessment in predetermined area on lateral elbow, a familirisation session for
      the perceived PTTs by participants will be performed on palm of the non dominant arm for each
      group.
    

Intervention name(s): Temporal summation; Placebo
Intervention type(s): Other; Other
Intervention description(s): Temporal summation will be evoked in each predetermined area; PPTs will be assessed once in each predetermined area
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Other
Keywords: motor performance; pain; temporal summation