Acute Effects of TENS on Cervical Muscle Stiffness and Pain in Neck Pain (TENS-NECK)

Acute Effects of Transcutaneous Electrical Nerve Stimulation on Passive Muscle Stiffness and Pain in Patients With Neck Pain: A Randomized Controlled Trial

This randomized controlled trial investigates the acute effects of transcutaneous electrical nerve stimulation (TENS) on passive cervical muscle stiffness (MyotonPro "dynamic stiffness", N/m) and pain (0-10 VAS) in adults with chronic/mechanical neck pain. Participants will be allocated 1:1 to TENS or control/sham. Outcomes are measured immediately before and immediately after a single 15-minute session.

Study Overview

• Status: Enrolling by invitation
• Conditions: Neck Pain; Chronic Neck Pain; Muscle Stiffness; Transcutaneous Electrical Nerve Stimulation
• Intervention / Treatment: Device: Transcutaneous Electrical Nerve Stimulation; Device: Sham TENS

Detailed Description

Background/Rationale: TENS modulates superficial afferent input and may reduce pain and muscle tone. However, its immediate impact on objective passive muscle stiffness measured by a handheld myotonometer (MyotonPro) in neck pain is insufficiently characterized. This trial tests whether a brief, low-risk intervention produces measurable changes in mechanical muscle properties and perceived pain in a short time window.

Objectives/Hypotheses:

Primary objective: Determine whether conventional TENS acutely reduces dynamic stiffness of the upper trapezius compared with control/sham.

Secondary objectives: Evaluate pain (VAS), additional MyotonPro parameters (frequency/tone, logarithmic decrement, relaxation time, creep), and safety/tolerability.

Hypothesis: TENS will show a significant group × time interaction favoring TENS over control/sham.

Design: Single-center (optionally multi-center), parallel-group, randomized (1:1) RCT. Masking: at minimum outcome assessor-blinded; participant blinding if sham TENS is used.

Sample Size: n = 24 (12 per arm), based on a priori power analysis (f≈0.40, α=0.05, power=0.95) for a 2×2 mixed design.

Intervention (TENS): Conventional mode; ~80 Hz, ≤150 µs pulse width; 15 minutes; intensity "strong but tolerable" without visible muscle contraction. Electrodes placed over the most painful/stiff segments (typically upper trapezius and/or suboccipital region), preferably bilateral.

Control/Sham: No intervention or sham TENS (electrodes applied; intensity raised to sensation then reduced below perception/zero; device indicators remain on).

Assessments & Timing:

Time points: T0 (pre-session), T1 (immediately post-session).

Primary outcome: Upper trapezius dynamic stiffness (N/m)-three repetitions averaged at a standardized anatomical landmark.

Secondary outcomes: Pain VAS (0-10); MyotonPro frequency/tone, decrement, relaxation time, creep on upper trapezius ± SCM ± cervical extensors; adverse events/tolerability. (Neck Disability Index may be collected at baseline for descriptive characterization.)

Statistical Plan: Mixed-effects repeated-measures analysis with Group (TENS vs control/sham) × Time (T0 vs T1); assumption checks with robust alternatives/transformations as needed; multiple-comparison controls; effect sizes reported.

Eligibility (summary): Adults 18-50 years with neck pain VAS ≥3/10. Key exclusions include pacemaker, pregnancy, recent invasive procedures (≤6 weeks), significant dermatologic issues at electrode sites, cervical radiculopathy/neurological signs, acute neck injury. (Full list in Eligibility.)

Safety: Low-risk, non-invasive procedure. Expected adverse effects are minor (e.g., transient discomfort or skin irritation). AE/SAE monitoring is prospective; the session will be stopped if intolerable symptoms occur.

• Study Type: Interventional
• Enrollment (Estimated): 24
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Erzurum, Turkey (Türkiye)
    • Erzurum Technical University Faculty of Health Sciences

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Age 18-50 years.

Neck pain VAS ≥ 3/10 at screening and on test day.

Clinical diagnosis of chronic or mechanical neck pain (≥6 weeks).

Able to understand study procedures and provide written informed consent.

Willing to refrain from analgesics/muscle relaxants and vigorous neck/shoulder exercise for 24 hours before testing.

Exclusion Criteria:

• Cervical radiculopathy or neurological signs (myotomal weakness, dermatomal sensory loss, reflex changes).

Recent invasive procedures to the neck/shoulder (e.g., surgery, injections, radiofrequency/neurotomy) within 6 weeks.

Pacemaker/implantable cardioverter, or other active implanted electronic device.

Pregnancy or planning pregnancy.

Skin conditions at electrode sites (open wounds, infection, severe dermatitis) or known allergy to electrode adhesive/gel.

History of epilepsy or unexplained syncope.

Acute neck trauma (<6 weeks) or red flags (fracture, malignancy, infection, inflammatory rheumatic disease).

Systemic disorders likely to affect outcomes (e.g., uncontrolled diabetes with neuropathy, severe cardiovascular disease, fibromyalgia with widespread pain).

Ongoing electrotherapy to the neck region or botulinum toxin injections to cervical muscles within 3 months.

Inability to comply with procedures (e.g., severe communication/cognitive impairment), or insufficient proficiency in Turkish to complete measures.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: TENS; Participants receive a single session of conventional TENS targeting painful/stiff cervical muscle regions (typically upper trapezius ± suboccipital) with immediate post-session assessments.	Device: Transcutaneous Electrical Nerve Stimulation; Conventional mode TENS, frequency ~80 Hz, pulse width ≤150 µs, duration 20 minutes. Intensity set to "strong but tolerable" without visible muscle contraction. Electrodes placed bilaterally over the most painful/stiff segments (e.g., upper trapezius midpoint along C7-acromion line; adjustments per comfort; Other Names: Conventional TENS; TENS therapy; Device: Sham TENS; Electrodes applied at the same anatomical sites as the active arm. Device indicators remain on; intensity is ramped to perception briefly and then reduced to sub-sensory/zero so that no effective current is delivered for the remainder of the 20-minute session. Procedures and clinician-participant interactions mirror the active arm; Other Names: Placebo TENS
Sham Comparator: Sham TENS; Participants undergo a sham stimulation session with identical setup and timing to mimic TENS without delivering therapeutic current.	Device: Transcutaneous Electrical Nerve Stimulation; Conventional mode TENS, frequency ~80 Hz, pulse width ≤150 µs, duration 20 minutes. Intensity set to "strong but tolerable" without visible muscle contraction. Electrodes placed bilaterally over the most painful/stiff segments (e.g., upper trapezius midpoint along C7-acromion line; adjustments per comfort; Other Names: Conventional TENS; TENS therapy; Device: Sham TENS; Electrodes applied at the same anatomical sites as the active arm. Device indicators remain on; intensity is ramped to perception briefly and then reduced to sub-sensory/zero so that no effective current is delivered for the remainder of the 20-minute session. Procedures and clinician-participant interactions mirror the active arm; Other Names: Placebo TENS

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in upper trapezius dynamic stiffness	Passive muscle dynamic stiffness (N/m) measured with MyotonPro at a standardized landmark on the upper trapezius (midpoint along the C7-acromion line; side = most symptomatic or bilateral mean).	Pre-session (T0) and immediately post-session (T1; within 5 minutes of session end)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in pain intensity	0-10 Visual Analog Scale for current neck pain (0 = no pain, 10 = worst imaginable).	T0 and immediately post-session

Collaborators and Investigators

• Sponsor: Erzurum Technical University
• Collaborators: Ataturk University; Bangor University; Amasya University
• Investigators: Study Director: Gökhan YAGİZ, Dr., Amasya University

Study record dates

Study Major Dates

• Study Start (Actual): September 23, 2025
• Primary Completion (Estimated): December 10, 2025
• Study Completion (Estimated): December 15, 2025

Study Registration Dates

• First Submitted: November 17, 2025
• First Submitted That Met QC Criteria: November 20, 2025
• First Posted (Actual): November 24, 2025

Study Record Updates

• Last Update Posted (Actual): November 24, 2025
• Last Update Submitted That Met QC Criteria: November 20, 2025
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: TENS; MyotonPro; VAS pain
• Additional Relevant MeSH Terms: Pain; Neurologic Manifestations; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Neck Pain; Therapeutics; Physical Therapy Modalities; Rehabilitation; Anesthesia and Analgesia; Electric Stimulation Therapy; Analgesia; Transcutaneous Electric Nerve Stimulation
• Other Study ID Numbers: ETU-TENS-NECK-RCT-02; Erzurum Technical University (Other Identifier: Erzurum Technical University)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: De-identified IPD (outcomes, baseline demographics, allocation, adverse events) will be shared ~6 months after primary completion for 36 months via an institutional repository or encrypted transfer managed by Erzurum Technical University.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No