Optimization of Lumbar Sensory Stimulation Parameters in Office Workers With Chronic Low Back Pain (LSS-OPT)

August 30, 2026 updated by: Peemongkon Wattananon, Mahidol University

Effects of Different Lumbar Vibration Parameters on Somatosensory Cortical Responses in Office Workers With Chronic Nonspecific Low Back Pain: A Randomized Crossover Study

This study aims to determine the optimal parameters of lumbar sensory stimulation in office workers with chronic nonspecific low back pain. Participants will attend two laboratory sessions. The first session will characterize baseline clinical and sensorimotor function using clinical assessments, transcranial magnetic stimulation, functional near-infrared spectroscopy during unstable sitting, inertial measurement units, decomposition electromyography, and rehabilitative ultrasound imaging. The second session will use a randomized within-participant crossover design in which participants receive eight combinations of lumbar vibration frequency, amplitude, and direction while bilateral primary somatosensory cortex hemodynamic responses are continuously measured using functional near-infrared spectroscopy. The primary objective is to identify vibration parameters that produce a favorable and consistent cortical response while meeting predefined comfort, safety, and technical criteria.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Phase II is an experimental laboratory study designed to optimize the neurophysiological parameters of lumbar sensory stimulation in office workers with chronic nonspecific low back pain. The primary objective is to determine which combination of vibration frequency, amplitude, and direction produces the most favorable cortical response in the bilateral primary somatosensory cortex (S1), while meeting predefined safety, comfort, and technical criteria.

Participants will complete two laboratory visits separated by approximately 48-72 hours. The two visits have different purposes and are not intended to constitute a pre- and post-intervention comparison.

Visit 1: Baseline clinical and sensorimotor characterization During the first visit, participants will undergo clinical and neurophysiological assessments to characterize their baseline clinical and sensorimotor profiles. Clinical assessments will include pain intensity, low back pain-related disability, work-related musculoskeletal discomfort, movement-control testing, tactile acuity, and pressure pain threshold.

Corticospinal excitability will be assessed using single-pulse transcranial magnetic stimulation (TMS), with motor-evoked potentials recorded from the lumbar multifidus and erector spinae muscles. Somatosensory cortical and postural responses will be assessed during unstable sitting using functional near-infrared spectroscopy (fNIRS) over the bilateral S1 together with inertial measurement units (IMUs). Participants will also perform a repeated loaded forward-bending task while lumbar multifidus motor-unit behavior is recorded using decomposition electromyography (dEMG) and trunk movement is recorded using IMUs. Finally, lumbar multifidus morphology and contractile response will be assessed using rehabilitative ultrasound imaging (RUSI) at rest and during contralateral arm lifting.

The measurements obtained during Visit 1 are intended to characterize individual baseline sensorimotor function and to permit exploratory analyses of associations between clinical characteristics, corticospinal excitability, cortical responses, postural control, motor-unit behavior, lumbar multifidus contractile response, and responses to lumbar sensory stimulation. These measurements are not intended to serve as pre-intervention values for an acute pre-post comparison with Visit 2.

Visit 2: Randomized within-participant vibration-parameter optimization During the second visit, participants will undergo the vibration-fNIRS parameter-optimization experiment. Participants will lie prone in a relaxed position while an eight-channel fNIRS system records hemodynamic responses over the bilateral primary somatosensory cortex. A customized vibration apparatus will be positioned over the bilateral lumbar multifidus region.

Each participant will receive all eight vibration conditions generated from a 2 × 2 × 2 factorial combination of two vibration frequencies, two vibration amplitudes, and two stimulation directions. The order of the eight conditions will be randomized by computer for each participant to minimize systematic order effects. Randomization therefore applies to the sequence of stimulation conditions within each participant rather than allocation of participants to separate study arms.

Each vibration condition will be applied for 1 minute. A 5-minute passive rest period will be provided between successive vibration conditions to minimize fatigue and potential carryover effects and to allow the hemodynamic response to return toward baseline before the next condition.

The primary neurophysiological outcome will be the baseline-corrected change in oxygenated hemoglobin concentration (ΔHbO) in the bilateral S1 measured using fNIRS during each vibration condition. Secondary fNIRS outcomes will include changes in deoxygenated hemoglobin and total hemoglobin concentrations, peak oxygenated hemoglobin response, time to peak response, and area under the oxygenated hemoglobin response curve.

The effects of vibration frequency, amplitude, and direction, including their interactions, on the primary fNIRS outcome will be evaluated using a linear mixed-effects model with participant treated as a repeated or random effect. Condition order, testing period, baseline response, and preceding condition may be considered to evaluate potential sequence or carryover effects.

The optimal vibration parameters will not be selected solely on the basis of the largest cortical response. Parameter selection will integrate the magnitude and consistency of the bilateral S1 hemodynamic response with predefined criteria related to participant comfort, biomechanical safety, technical stability and performance of the stimulation apparatus, and suitability for subsequent incorporation into a wearable sensory stimulation belt. The selected parameters will subsequently be used in the Phase III randomized controlled trial.

Study Type

Interventional

Enrollment (Estimated)

36

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

  • Thailand
    • Changwat Nakhon Pathom
      • Salaya, Changwat Nakhon Pathom, Thailand, 73170
        • Faculty of Physical Therapy, Mahidol University
        • Contact:
        • Contact:
        • Principal Investigator:
          • Peemongkon Wattananon, PhD
        • Sub-Investigator:
          • Apinkarn Jaroenlarp, PhD Candidate
        • Sub-Investigator:
          • Preeyajit Anukulpipat, BSc
        • Sub-Investigator:
          • Nguyen The Minh Hung, BSc
        • Sub-Investigator:
          • Kent Fhilip Aseron, BSc

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Office workers who currently sit for at least 6 hours per workday.
  • Age 20-60 years.
  • Chronic nonspecific low back pain for at least 3 months.
  • Current pain intensity of at least 2/10 on the Numeric Pain Rating Scale.

Exclusion Criteria:

  • History of seizure for either the subject or any family member
  • Implanted pacemaker
  • Contraindications for TMS and fNIRS, including open wound, infection, lesions, arteriosclerosis, history of hemophilia, or demand-type pacemaker
  • Acute cerebral hemorrhage
  • History of major spinal surgery, fracture, or traumatic injury to the lumbar spine.
  • Evidence of neurological deficits (e.g., radiculopathy, loss of sensation, or motor weakness in lower limbs).
  • Diagnosis of systemic inflammatory conditions (e.g., Ankylosing Spondylitis, Rheumatoid Arthritis).
  • Allergy to adhesives or history of severe skin sensitivity to vibration/mechanical pressure.
  • Body Mass Index (BMI) > 30 kg/m2 (to ensure clarity of RUSI, dEMG, and fNIRs signal quality).
  • Pregnancy (due to changes in spinal biomechanics and hormones)

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Other
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Vibration parameter
A customized vibration apparatus will deliver controlled mechanical stimulation over the bilateral lumbar multifidus region. Participants will receive eight randomized combinations of vibration frequency, amplitude, and direction. Each condition will be delivered for 1 minute, followed by a 5-minute passive rest period.
Device: Lumbar sensory stimulation
A customized vibration apparatus will deliver controlled mechanical stimulation over the bilateral lumbar multifidus region. Participants will receive eight randomized combinations of vibration frequency, amplitude, and direction. Each condition will be delivered for 1 minute, followed by a 5-minute passive rest period.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in oxygenated hemoglobin concentration in bilateral primary somatosensory cortex
Time Frame: During each 1-minute vibration condition relative to its corresponding pre-stimulation baseline during the single Phase II parameter-optimization session.
Baseline-corrected change in oxygenated hemoglobin concentration (ΔHbO) recorded from the bilateral primary somatosensory cortex using an eight-channel functional near-infrared spectroscopy system during lumbar vibration.
During each 1-minute vibration condition relative to its corresponding pre-stimulation baseline during the single Phase II parameter-optimization session.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in deoxygenated hemoglobin concentration in the bilateral primary somatosensory cortex
Time Frame: During each vibration condition relative to the immediately preceding resting baseline during the Phase II parameter-optimization session
Deoxygenated hemoglobin concentration (ΔHHb) will be recorded from the bilateral primary somatosensory cortex using an eight-channel functional near-infrared spectroscopy (fNIRS) system. The outcome will be expressed as the baseline-corrected change in HHb during each lumbar vibration condition relative to the immediately preceding resting baseline
During each vibration condition relative to the immediately preceding resting baseline during the Phase II parameter-optimization session
Change in total hemoglobin concentration in the bilateral primary somatosensory cortex
Time Frame: During each vibration condition relative to the immediately preceding resting baseline during the Phase II parameter-optimization session
Total hemoglobin concentration (ΔHbT), calculated from oxygenated and deoxygenated hemoglobin signals, will be recorded from the bilateral primary somatosensory cortex using fNIRS. The outcome will be expressed as the baseline-corrected change in HbT during each lumbar vibration condition
During each vibration condition relative to the immediately preceding resting baseline during the Phase II parameter-optimization session
Peak oxygenated hemoglobin response in the bilateral primary somatosensory cortex
Time Frame: During each vibration condition relative to the immediately preceding resting baseline during the Phase II parameter-optimization session
The maximum baseline-corrected increase in oxygenated hemoglobin concentration (peak ΔHbO) within the predefined response window will be determined for each vibration condition. Left and right S1 responses may also be summarized separately and bilaterally
During each vibration condition relative to the immediately preceding resting baseline during the Phase II parameter-optimization session
Area under the oxygenated hemoglobin response curve in the bilateral primary somatosensory cortex
Time Frame: During each vibration condition relative to the immediately preceding resting baseline during the Phase II parameter-optimization session
The area under the curve (AUC) of the baseline-corrected oxygenated hemoglobin response will be calculated over the predefined response window for each vibration condition to quantify the magnitude and duration of the S1 hemodynamic response
During each vibration condition relative to the immediately preceding resting baseline during the Phase II parameter-optimization session
Corticospinal excitability of the lumbar multifidus measured by transcranial magnetic stimulation
Time Frame: During Visit 1 of Phase II, prior to the vibration-parameter optimization session
Corticospinal excitability will be assessed using single-pulse transcranial magnetic stimulation with surface EMG recording from the lumbar multifidus.
During Visit 1 of Phase II, prior to the vibration-parameter optimization session
Corticospinal excitability of the lumbar erector spinae measured by transcranial magnetic stimulation
Time Frame: During Visit 1 of Phase II, prior to the vibration-parameter optimization session
Corticospinal excitability will be assessed using single-pulse transcranial magnetic stimulation with surface EMG recording from the lumbar erector spinae.
During Visit 1 of Phase II, prior to the vibration-parameter optimization session
Change in oxygenated hemoglobin concentration during unstable sitting
Time Frame: During each sitting condition relative to the immediately preceding resting baseline in visit 1.
Cortical hemodynamic responses over the bilateral primary somatosensory cortex will be recorded using fNIRS during unstable sitting with eyes open and eyes closed.
During each sitting condition relative to the immediately preceding resting baseline in visit 1.
Postural-control response during unstable sitting
Time Frame: During each vibration condition relative to the immediately preceding resting baseline in visit 1
Postural-control behavior will be quantified during unstable sitting using inertial measurement units positioned at L1, S1, and the unstable chair.
During each vibration condition relative to the immediately preceding resting baseline in visit 1
Lumbar multifidus motor-unit behavior during loaded forward bending
Time Frame: During the loaded forward-bending assessment at baseline in Visit 1.
Motor-unit behavior of the bilateral lumbar multifidus will be assessed using decomposition electromyography during repeated 45° trunk flexion-extension while holding a load equivalent to 5% of body weight.
During the loaded forward-bending assessment at baseline in Visit 1.
Lumbar multifidus contractile response measured by rehabilitative ultrasound imaging
Time Frame: During the baseline assessment in Visit 1
Lumbar multifidus thickness will be measured at rest and during contralateral arm lifting using B-mode rehabilitative ultrasound imaging at the L4-L5 level.
During the baseline assessment in Visit 1

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Mahidol University

Investigators

  • Principal Investigator: Peemongkon Wattananon, PhD, Mahidol University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

January 1, 2027

Primary Completion (Estimated)

December 31, 2027

Study Completion (Estimated)

December 31, 2028

Study Registration Dates

First Submitted

August 25, 2026

First Submitted That Met QC Criteria

August 30, 2026

First Posted (Actual)

September 3, 2026

Study Record Updates

Last Update Posted (Actual)

September 3, 2026

Last Update Submitted That Met QC Criteria

August 30, 2026

Last Verified

August 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • Sensory-Stimulation-Phase-II

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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