The Effect of Frequency Modulation in TENS on Habituation and Pain Threshold

Study Overview
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Brief Summary
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Purpose The purpose of this study is to determine whether application of Transcutaneous Electrical Nerve Stimulation (TENS) is effective on habituation to electrical current whether delivered at a fixed frequency of 100 Hz or at patterned frequency. The secondary purposes are to determine the effectiveness on mechanical pressure pain and the subjective perception of the subjects regarding habituation and comfort of the different stimulations.

Detailed Description
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Low frequency and low intensity TENS showed strong evidence of inefficiency while conventional high frequency TENS (around 100Hz) applied at strong but comfortable intensity proved strong evidence of efficacy on pressure pain. In addition, some studies have shown the importance of current intensity in the effect of TENS. Either in clinical practice and in research, TENS intensity is usually adjusted according to the sensation of the subjects strong but comfortable strong just below the motor threshold, ...). Usually throughout the TENS applications there is a phenomenon called habituation that involve a wide decrease of the sensation of the current applied, even though the perception the output-parameters are maintained. In this sense, It has been seem that adjusting the intensity throughout the TENS intervention produced a greater hypoalgesic effect than when the intensity remained fixed. On the other hand, most TENS devices offer the possibility of modulating current with the aim of preventing habituation phenomenon. The modulation of the electric current consists of changing the characteristics of the current (pulse width, pulse frequency, ...) every few seconds during the intervention. Nevertheless, the most common pattern used is the frequency modulation. However, there is a lack of evidence regarding what it is the better methods to avoid habituation during a TENS application.

Official Title
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The Effect of Frequency Modulation in Transcutaneous Electrical Nerve Stimulation (TENS) on Habituation and Pain Threshold: a Randomized, Double Blind, Controlled Cross-over

Conditions
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Transcutaneous Electrical Nerve Stimulation

Intervention / Treatment
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* Device: TENS: Randomized frequency modulation
* Device: TENS: Scan 6/6 of frequency modulation
* Device: TENS: Fixed frequency
* Device: Sham Stimulation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Participants will be volunteer healthy students of University of Castilla - La Mancha, older than 18 years. Exclusion Criteria: Neuromuscular disease. Epilepsy. Trauma, surgery or pain affecting the upper limb, shoulder girdle or cervical area. Osteosynthesis material in the upper limb. Cancer. Cardiovascular disease. Pacemaker or other implanted electrical device. Take any drug (NSAIDs, corticosteroids, antidepressants, analgesics, antiepileptics, ...) during the study and in the previous 7 days. Presence of tattoos or other external agent introduced into the treatment or assessment area. Pregnancy. Sensitivity disturbance in upper limb.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 30 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: TENS: Randomized frequency modulation<br>TENS transcutaneous electrical stimulation over superficial radial nerve through the electrotherapy device Myomed 932. (Enraf-Nonius, Delft, Netherlands) | Device: TENS: Randomized frequency modulation<br>* Transcutaneous application of Conventional TENS current over the course of the superficial radial nerve in the right forearm for a 20 minutes session. The intensity of the current will increase until participants report a strong but comfortable sensation, just Transcutaneous application of Conventional TENS current over the course of the superficial radial nerve in the right forearm for a 20 minutes session. The intensity of the current will increase until participants report a strong but comfortable sensation, just below motor threshold. Currents parameters are: Frequency modulation: randomized pattern (from 80 to 120 Hz) Pulse width 200 microseconds<br>|
| Experimental: TENS: Scan 6/6 of frequency modulation<br>TENS transcutaneous electrical stimulation over superficial radial nerve through the electrotherapy device Myomed 932. (Enraf-Nonius, Delft, Netherlands) | Device: TENS: Scan 6/6 of frequency modulation<br>* Transcutaneous application of Conventional TENS current over the course of the superficial radial nerve in the right forearm for a 20 minutes session. The intensity of the current will increase until participants report a strong but comfortable sensation, just below motor threshold. Currents parameters are: Frequency modulation: Scan of frequency from 80 to 120 Hz in 6/6 mode (frequency sweep from 80 Hz to 120 Hz in 6 seconds and from 120 to 80 Hz in 6 secons) Pulse width 200 microseconds<br>|
| Experimental: TENS: Fixed frequency<br>TENS transcutaneous electrical stimulation over superficial radial nerve through the electrotherapy device Myomed 932. (Enraf-Nonius, Delft, Netherlands) | Device: TENS: Fixed frequency<br>* Transcutaneous application of Conventional TENS current over the course of the superficial radial nerve in the right forearm for a 20 minutes session. The intensity of the current will increase until participants report a strong but comfortable sensation, just below motor threshold. Currents parameters are: Fixed frequency at 100 Hz Pulse width 200 microseconds<br>|
| Sham Comparator: TENS: Sham stimulation<br>Sham transcutaneous electrical stimulation over superficial radial nerve through the electrotherapy device Myomed 932. (Enraf-Nonius, Delft, Netherlands) | Device: Sham Stimulation<br>* Electrodes are placed over the course of the superficial radial nerve in the right forearm for a 20 minutes in the same manner as experimental groups, but will be applied a sham electrical stimulation increasing the current intensity of an unconnected channel.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Habituation to electrical stimulation | Due to habituation it is necessary to increase the intensity of the current throughout the session. Two measures were recorded within this variable: i) the increase in current density (mA / cm2) throughout the session (difference between its initial frequency and final frequency value of the current) and the number of times the participant requested to increase the intensity (subjects were instructed to maintain the same threshold) | Baseline | 
| Habituation to electrical stimulation | Due to habituation it is necessary to increase the intensity of the current throughout the session. Two measures were recorded within this variable: i) the increase in current density (mA / cm2) throughout the session (difference between its initial frequency and final frequency value of the current) and the number of times the participant requested to increase the intensity (subjects were instructed to maintain the same threshold) | during treatment at 15 min | 
| Habituation to electrical stimulation | Due to habituation it is necessary to increase the intensity of the current throughout the session. Two measures were recorded within this variable: i) the increase in current density (mA / cm2) throughout the session (difference between its initial frequency and final frequency value of the current) and the number of times the participant requested to increase the intensity (subjects were instructed to maintain the same threshold) | at 10 min. post-treatment | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Mechanical pain threshold | The pressure pain threshold will be measured by a pressure digital algometer (Wagner Instruments, FDIX. Post Office Box 1217, Greenwich, CT 06836-1217 USA.) and will be expressed in Newton; on the back of the right hand (about 3 cm from the first interdigital foldand) . The mechanical pain threshold will be assessed 3 time in order to calculate the mean value. | Baseline | 
| Mechanical pain threshold | The pressure pain threshold will be measured by a pressure digital algometer (Wagner Instruments, FDIX. Post Office Box 1217, Greenwich, CT 06836-1217 USA.) and will be expressed in Newton; on the back of the right hand (about 3 cm from the first interdigital foldand) . The mechanical pain threshold will be assessed 3 time in order to calculate the mean value. | during treatment at 15 min. | 
| Mechanical pain threshold | The pressure pain threshold will be measured by a pressure digital algometer (Wagner Instruments, FDIX. Post Office Box 1217, Greenwich, CT 06836-1217 USA.) and will be expressed in Newton; on the back of the right hand (about 3 cm from the first interdigital foldand) . The mechanical pain threshold will be assessed 3 time in order to calculate the mean value. | at 10 min. post-treatment | 
| Perception current comfortability | Visual scale from 0 mm to 100 mm | at 1min. post-treatment | 
| Perception current habituation | Visual scale from 0 mm to 100 mm | at 1min. post-treatment | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Pain Threshold, Transcutaneous Electrical Nerve Stimulation, Habituation