An interventional study of Active Photobiomodulation and Placebo Photobiomodulation in Photobiomodulation, Fatigue and Discomfort, sponsored by Federal University of Rio Grande do Sul. Recruiting at 1 site in Brazil. Open to participants aged 18 Years to 45 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-08-25.
Sponsored by Federal University of Rio Grande do Sul · Not applicable, Interventional, and Treatment
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.
2,229 studies on the registry are indexed under Fatigue; 426 are open to participants now.
This study's planned enrollment of 36 is below the median of 54 across 1,757 interventional studies indexed under Fatigue.
Browse Fatigue studies →Federal University of Rio Grande do Sul is the lead sponsor of 121 studies on the registry; 20 are open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants in this arm will receive active photobiomodulation therapy.
Device: Active Photobiomodulation · Other: NMES-evoked fatigue protocol
Participants in this arm will receive an inactive (placebo) photobiomodulation treatment.
Device: Placebo Photobiomodulation · Other: NMES-evoked fatigue protocol
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.
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.
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).
Maximal voluntary isometric contraction (MVIC)
Largest knee extensor torque generated isometrically and voluntarily on an isokinetic dynamometer. Unit of Measure: Newton-meters (N.m)
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).
Evoked fatigue
Fall in the evoked torque during the fatigue protocol. Unit of Measure: Newton-meters (N.m)
Time frame: Continuously during the 20-minute fatigue protocol.
Muscle Echo Intensity
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
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).
Pressure Pain Threshold
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)
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).
Quadriceps Muscle Thickness
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)
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).
Countermovement Jump (CMJ) Height
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)
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).
Lower Limb Joint Kinematics During Jump
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 (°)
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).
Force-Time Curve Dynamics During Jump
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)
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).
Muscle Activation
Surface electromyography (sEMG) to assess muscle activation amplitude during MVIC. Unit of Measure: Microvolts (uV)
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).
Vastus Lateralis Fascicle Length
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)
Time frame: Continuously during the 20-minute fatigue protocol on Day 1.
Vastus Lateralis Pennation Angle
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 (°)
Time frame: Continuously during the 20-minute fatigue protocol on Day 1.
Adipose Tissue Thickness
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)
Time frame: Baseline
Plan to share: No — A final decision regarding the sharing of individual participant data has not yet been made. The study team intends to evaluate this possibility following the primary data analysis, in accordance with institutional guidelines and ethical committee requirements.
No publications or documents are linked to this record.
Started Jun 2026 (actual). Primary completion is estimated for Aug 2026, 2 months after the start.
Of 936 non-industry interventional studies with no phase under Fatigue, half reached primary completion within 12 months of starting (the median), counting those still running; a quarter within 5 and three quarters within 27. This study's planned 2 months is below that.
Counting every sponsor, half of 989 studies reached it within 11 months; a quarter within 5 and three quarters within 27.
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