Photobiomodulation, Fatigue, Discomfort, Electrical Stimulation, Muscle Damage
Conditions
Keywords
Photobiomodulation, Fatigue, Discomfort, Muscle Damage, Electrical stimulation
Brief summary
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.
Interventions
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.
OTHERNMES-evoked fatigue protocol
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).
Sponsors
Federal University of Rio Grande do Sul
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
TRIPLE (Subject, Investigator, Outcomes Assessor)
Masking description
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.
Intervention model description
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.
Eligibility
Sex/Gender
ALL
Age
18 Years to 45 Years
Healthy volunteers
Yes
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Maximal voluntary isometric contraction (MVIC) | 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) |
| Evoked fatigue | Continuously during the 20-minute fatigue protocol. | Fall in the evoked torque during the fatigue protocol. Unit of Measure: Newton-meters (N.m) |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Muscle Echo Intensity | 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 |
| Pressure Pain Threshold | 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) |
| Quadriceps Muscle Thickness | 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) |
| Countermovement Jump (CMJ) Height | 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) |
| Lower Limb Joint Kinematics During Jump | 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 (°) |
| Force-Time Curve Dynamics During Jump | 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) |
| Muscle Activation | 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) |
| Vastus Lateralis Fascicle Length | 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) |
Countries
Brazil
Contacts
CONTACTMarco A Vaz, PhD
STUDY_CHAIRMarco A Vaz, PhD
Federal University of Rio Grande do Sul
STUDY_DIRECTORMarco A Vaz, PhD
Federal University of Rio Grande do Sul
PRINCIPAL_INVESTIGATORMarco A Vaz, PhD
Federal University of Rio Grande do Sul
Outcome results
None listed