The Antalgic Effect of Pulse Frequency and Pad Size of TENS on Blunt Pressure Pain
Condition: Transcutaneous Electrical Nerve Stimulation; Blunt Pressure Pain; Pad Size; Pulse Frequency; Analgesia
Study type: Interventional

Summary: 
      The purpose of this study is to determine the antalgic of surface electrical stimulation with
      pulse frequencies and pad sizes on blunting pressure pain on healthy human due to various
      temporal and spatial summations of the stimulation.
    

Detailed description: 
      Potential participants expressing interest in the study will be given to read the
      contraindications for the pain tests and the stimulation intervention, which has been
      documented on the consent form. All participants meeting entry requirements will be invited
      to participate in the experiments which take place on a separate occasion.

      Each participant will sign the consent form and will be told again that they can withdraw
      from the study at any time and without explanation. Each participant will be required to
      experience a 10-minute pre-stimulation period, a 30 minute TENS intervention, a 30 minute
      follow-up period.

      Participants will be seated on a chair with arm support provided by a side table. The
      investigator will be then informed the stimulation intervention and used pad size on the
      stimulation periods in written form contained in a sealed envelope. After the participant's
      verbal permission is obtained, the investigator will apply the pads on the dorsal forearm
      area.

      Either the large size pad, 5cm x 10cm, or the small size,2.5cm x 2.5cm, will be choose to
      place on the dorsal side of the forearm to straddle the site for blunt pressure pain. The
      muscle bellies of the forearm are mainly located on the proximal half part. The proximal pad
      will be attached to the lateral epi-condyle of the elbow, and the distal electrode will be
      placed 3cm distal to the proximal one along the line between the lateral part of elbow and
      the mid-point of the wrist. The pads will be then connected to the intervention stimulator.
      The investigator will relay instructions to the participants using cue cards displayed 30
      seconds before any required action.

      Before each blunting pressure pain test, the participant will sit comfortably and place their
      right upper extremity on a side table with the shoulder abduction, elbow flexion, the forearm
      pronation. The test will be induced using a pressure algometer with a flat circular probe,
      measuring 1.1cm in diameter (1cm2 on skin surface). Force will be displayed digitally in
      increments of 0.1 Newton. The algometer will be applied to the mid-point between the
      intervention pads. The rate of the pressure algometer application will be around 6 Newtons
      per second on average. The participants will be asked to concentrate on the sensations in the
      forearm. When the pressure becomes definitely painful, the participant will state "Pain!" and
      the force will be stopped. The pain threshold will be taken twice in a minute for one test
      and each measurement will take no more than 30 seconds.

      There will be seven 1-minute tests performed in this experiment. The first test in
      pre-stimulation period. The second and third tests were administered and started at 9, 19, 29
      minute time points in the stimulation-on period. A 30 minute post stimulation period will be
      then followed. Another 3 tests will be performed in this period in ten-minute intervals at
      39, 49, 59 minute time points after the stimulation start.
    

Intervention name(s): Control TENS; Sham TENS; High frequency TENS with large pads; Low frequency TENS with large pads; High frequency TENS with small pads; Low frequency TENS with small pads
Intervention type(s): Device; Device; Device; Device; Device; Device
Intervention description(s): Control TENS was the application of electrical stimulation via skin with no current; Sham TENS was the application of electrical stimulation via skin with no current on the participant, who was told "TENS is at a turn-on level whether or not you feel it"; High frequency TENS was delivered on large electrodes; Low frequency TENS was delivered on large electrodes; High frequency TENS was delivered on small electrodes; Low frequency TENS was delivered on small electrodes
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: One hundred eighty participants (equal number of females and males, Fig. 1) were randomly assigned into six groups with the following TENS characteristics. (1) Group 1:
control group, (2) group 2: sham group, (3) group 3: high frequency (80 pps)/large pad (5 cm x 10 cm) group, (4) group 4: low frequency (3 pps)/large pad (5 cm x 10 cm) group, (5) group 5: high frequency (80 pps)/small pad (5 cm x 2.5 cm) group, and (6) group 6: low frequency (3 pps)/small pad (5 cm x 2.5 cm) group.
Masking: Double (Participant, Investigator)
Primary purpose: Treatment
Keywords: transcutaneous electrical nerve stimulation; pad size; pulse frequency; blunt pressure pain; healthy humans.