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| Name | Class |
|---|---|
| Conselho Nacional de Desenvolvimento Científico e Tecnológico | OTHER_GOV |
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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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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Photobiomodulation (PBM) | Experimental | Participants in this arm will receive active photobiomodulation therapy. |
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| Sham PBM | Sham Comparator | Participants in this arm will receive an inactive (placebo) photobiomodulation treatment. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| 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. |
| Measure | Description | Time Frame |
|---|---|---|
| Maximal voluntary isometric contraction (MVIC) | Largest knee extensor torque generated isometrically and voluntarily on an isokinetic dynamometer. Unit of Measure: Newton-meters (N.m) | 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) | Continuously during the 20-minute fatigue protocol. |
| Measure | Description | Time Frame |
|---|---|---|
| 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 | 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 | Time Frame |
|---|---|---|
| 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 (°) | Continuously during the 20-minute fatigue protocol on Day 1. |
| Adipose Tissue Thickness |
Inclusion Criteria:
Exclusion Criteria:
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Marco A Vaz, PhD | Contact | +555133085853 | marco.vaz@ufrgs.br |
| Name | Affiliation | Role |
|---|---|---|
| Marco A Vaz, PhD | Federal University of Rio Grande do Sul | Study Chair |
| Marco A Vaz, PhD | Federal University of Rio Grande do Sul | Study Director |
| Marco A Vaz, PhD |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Laboratório de Pesquisa do Exercício | Recruiting | Porto Alegre | Rio Grande do Sul | 90690200 | Brazil |
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.
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| ID | Term |
|---|---|
| D005221 | Fatigue |
| ID | Term |
|---|---|
| D012816 | Signs and Symptoms |
| D013568 | Pathological Conditions, Signs and Symptoms |
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Design Model: Parallel Assignment. Number of Arms: 2 (Arm 1: PBM; Arm 2: Sham). Timeline: Assessments will be performed at baseline, followed by the NMES-evoked fatigue protocol. Subsequent evaluations will be conducted post-intervention immediately, and at 24, 48, and 72 hours post-intervention.
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Participants and outcome assessors will be blinded to the intervention groups. The investigator responsible for data analysis will also be blinded. Due to the nature of the equipment operation, the individual administering the treatment (care provider) will not be blinded.
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| 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. |
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| 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). |
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| 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) | 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) | 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) | 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 (°) | 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) | 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) | 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) | Continuously during the 20-minute fatigue protocol on Day 1. |
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) |
| Baseline |
| Federal University of Rio Grande do Sul |
| Principal Investigator |