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NCT Number: NCT07602933

Photobiomodulation Effects on Fatigue and Muscle Damage Induced by NMES

Neuromuscular electrical stimulation (NMES) is widely used to improve muscle strength and mitigate atrophy. However, its clinical efficacy is often limited by early neuromuscular fatigue, muscle damage, and discomfort, which reduce patient tolerance and contraction time. Photobiomodulation (PBM) has emerged as a potential therapy to enhance muscle performance and accelerate recovery by minimizing fatigue and damage. Despite its potential, few studies have investigated the effects of PBM applied specifically before an NMES-evoked fatigue protocol. This randomized, double-blind, placebo-controlled trial aims to evaluate the acute effects of PBM on neuromuscular fatigue, muscle damage, and functional outcomes in healthy young subjects. Participants will receive either active PBM (cluster probe: 5 lasers 810nm/200mW; 4 LEDs 660nm/10mW; Total Energy: 249.6 J per limb) or sham treatment 5 minutes before a fatiguing NMES protocol (80 contractions at 20% MVIC, 80 Hz, 1ms pulse width) applied to the quadriceps muscle. Assessments will be performed at baseline, immediately post-intervention, and at 24h, 48h, and 72h post-intervention. Primary outcomes include maximum and evoked isometric strength, mechanical work, and electrical muscle activity. Secondary outcomes include muscle damage (ultrasound echo-intensity), delayed onset muscle soreness (DOMS), functional performance (unilateral vertical jump), and clinical discomfort. The study seeks to determine if PBM can effectively modulate NMES-induced fatigue and muscle damage, potentially optimizing its clinical application.

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Key information

Conditions

Photobiomodulation Discomfort Electrical Stimulation Fatigue Muscle Damage Pathological Conditions, Signs and Symptoms Signs and Symptoms

Age range

18 year–45 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Laboratório de Pesquisa do Exercício

Porto Alegre, Rio Grande do Sul, 90690200, Brazil

Location status: Recruiting

Location contact

Gustavo N Petter, MSc

SUB_INVESTIGATOR

Jeam M Geremia, PhD

CONTACT

[email protected]

5133085853

Marco A Vaz, PhD

PRINCIPAL_INVESTIGATOR

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Healthy male and female volunteers.
  • Age between 18 and 45 years.
  • Practice physical activity regularly
  • No history of musculoskeletal injuries in the lower limbs in the last 6 months
  • Ability to tolerate NMES

Exclusion criteria

  • Have sensory intolerable changes due to NMES
  • Consumed coffee or another stimulant in the last 12 hours
  • Have a body mass index (BMI) greater than 30 kg/m2 (grade I obesity)
  • Present any contraindication for the performance of maximum effort
  • Abnormal increase in blood pressure after maximal exertion

Treatment and study plan

Active Photobiomodulation

Device

Application of PBMT using a cluster probe (Thor-DD2; 5 laser diodes: 810nm, 200mW; 4 LEDs: 660nm, 10mW). The treatment involves 8 points on the quadriceps (2 on vastus medialis, 3 on vastus lateralis, and 3 on rectus femoris). Each point is irradiated for 30 seconds in continuous mode with direct contact and slight pressure. Total energy: 31.2 J per point and 249.6 J per limb. Both therapist and participant will wear protective goggles.

Placebo Photobiomodulation

Device

The procedure is identical to the active PBMT (8 points, 30 seconds per point, same pressure and positioning), but the device will be turned off. To ensure blinding, participants will wear protective goggles and a blindfold to prevent visual perception of the light.

NMES-evoked fatigue protocol

Other

Neuromuscular Electrical Stimulation (Myomed 932) applied to the quadriceps. Parameters: 80 Hz frequency, 1 ms pulse width (biphasic rectangular pulse), 5s:10s ON:OFF ratio with 1s ramp-up/down. The protocol lasts 20 minutes, totaling 80 evoked isometric contractions. Current intensity is adjusted to generate an initial torque of 20% of the baseline Maximum Voluntary Isometric Contraction (MVIC).

Primary outcomes

  1. Maximal voluntary isometric contraction (MVIC)

    Time frame: Baseline (pre-intervention) on Day 1; immediately after the fatigue protocol on Day 1; and at 24, 48, and 72 hours after the fatigue protocol (on Days 2, 3, and 4, respectively).

    Largest knee extensor torque generated isometrically and voluntarily on an isokinetic dynamometer.

    Unit of Measure: Newton-meters (N.m)

  2. Evoked fatigue

    Time frame: Continuously during the 20-minute fatigue protocol.

    Fall in the evoked torque during the fatigue protocol. Unit of Measure: Newton-meters (N.m)

Secondary outcomes

  1. Muscle Echo Intensity

    Time frame: Baseline (pre-intervention) on Day 1; immediately after the fatigue protocol on Day 1; and at 24, 48, and 72 hours after the fatigue protocol (on Days 2, 3, and 4, respectively).

    Quantitative analysis of muscle ultrasound images to assess changes in echo intensity, reflecting acute edema and changes in muscle quality. Analysis will be performed specifically on the Rectus Femoris (RF), Vastus Medialis (VM), and Vastus Lateralis (VL).

    Unit of Measure: Arbitrary Units (au) on a 0-255 grayscale

  2. Pressure Pain Threshold

    Time frame: Baseline (pre-intervention) on Day 1; immediately after the fatigue protocol on Day 1; and at 24, 48, and 72 hours after the fatigue protocol (on Days 2, 3, and 4, respectively).

    The minimum pressure at which a subject perceives a stimulus as painful, measured via pressure algometry on the quadriceps muscle bellies to quantify delayed onset muscle soreness (DOMS). Unit of Measure: Newtons (N)

  3. Quadriceps Muscle Thickness

    Time frame: Baseline (pre-intervention) on Day 1; immediately after the fatigue protocol on Day 1; and at 24, 48, and 72 hours after the fatigue protocol (on Days 2, 3, and 4, respectively).

    Ultrasound assessment of structural changes in the quadriceps muscle group, for the Rectus Femoris (RF), Vastus Medialis (VM), and Vastus Lateralis (VL). This variable evaluates acute morphological changes or edema-induced swelling following the NMES protocol.

    Unit of Measure: Millimeters (mm)

  4. Countermovement Jump (CMJ) Height

    Time frame: Baseline (pre-intervention) on Day 1; immediately after the fatigue protocol on Day 1; and at 24, 48, and 72 hours after the fatigue protocol (on Days 2, 3, and 4, respectively).

    Measure Description: Maximum jump height achieved during a vertical countermovement jump on a force platform to assess dynamic muscle power.

    Unit of Measure: Centimeters (cm)

  5. Lower Limb Joint Kinematics During Jump

    Time frame: Baseline (pre-intervention) on Day 1; immediately after the fatigue protocol on Day 1; and at 24, 48, and 72 hours after the fatigue protocol (on Days 2, 3, and 4, respectively).

    Measure Description: Sagittal plane kinematic analysis for the ankle, knee, hip, and trunk joints to evaluate movement strategies and joint range of motion during the countermovement jump.

    Unit of Measure: Degrees (°)

  6. Force-Time Curve Dynamics During Jump

    Time frame: Baseline (pre-intervention) on Day 1; immediately after the fatigue protocol on Day 1; and at 24, 48, and 72 hours after the fatigue protocol (on Days 2, 3, and 4, respectively).

    Analysis of the vertical ground reaction force-time curve during the propulsion phase of the countermovement jump. The primary parameter will be the Vertical Impulse, calculated as the integral of force over time. Unit of Measure: Newton-seconds (N.s)

  7. Muscle Activation

    Time frame: Baseline (pre-intervention) on Day 1; immediately after the fatigue protocol on Day 1; and at 24, 48, and 72 hours after the fatigue protocol (on Days 2, 3, and 4, respectively).

    Surface electromyography (sEMG) to assess muscle activation amplitude during MVIC. Unit of Measure: Microvolts (uV)

  8. Vastus Lateralis Fascicle Length

    Time frame: Continuously during the 20-minute fatigue protocol on Day 1.

    Measure Description: Assessment of real-time changes in the fascicle length of the Vastus Lateralis muscle during the fatigue protocol using continuous ultrasound imaging.

    Unit of Measure: Millimeters (mm)

Other outcomes

  1. Vastus Lateralis Pennation Angle

    Time frame: Continuously during the 20-minute fatigue protocol on Day 1.

    Measure Description: Assessment of real-time changes in the pennation angle of the Vastus Lateralis muscle during the fatigue protocol using continuous ultrasound imaging.

    Unit of Measure: Degrees (°)

  2. Adipose Tissue Thickness

    Time frame: Baseline

    Measurement of the fat layer thickness overlying the Rectus Femoris, Vastus Medialis, and Vastus Lateralis using ultrasound imaging. This measure is used to characterize the sample's morphology and will serve as a covariate to adjust the delivered PBM dose and NMES current penetration analysis. Unit of Measure: Millimeters (mm)

Study contacts

Contact information is provided by the study sponsor or research team.

Marco A Vaz, PhD

CONTACT

[email protected]

+555133085853

Sponsors and collaborators

Lead sponsor

Federal University of Rio Grande do Sul

Other

Collaborators

  • Conselho Nacional de Desenvolvimento Científico e Tecnológico

Registry information

Official study title

Effects of Photobiomodulation on Fatigue and Muscle Damage Induced by Neuromuscular Electrical Stimulation in Healthy Individuals: a Randomized Clinical Trial

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
May 22, 2026
Registry last updated
Jun 25, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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