Whole-Body Photobiomodulation Use in Professional Soccer Players During a State Championship
Phase: NA
Conditions: Athletic Performance, Muscle Fatigue, Muscle Strength, Sports
Sponsor: Universidade Federal de Sao Carlos

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Document Type: Study Protocol and Statistical Analysis Plan 
NCT Number:  
Document Date: September 04, 2025 
Prepared by: Italo Amaral de Oliveira, PT, MSc 
Institution: Federal University of São Carlos (UFSCar), São Paulo, Brazil 
 
 
 
 
 
 
 
Study Title: 
Whole-body Photobiomodulation Use in Professional Soccer Players During a State 
Championship: Randomized Controlled Trial 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
São Carlos, 2025 
 
 

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1. Introduction 
Photobiomodulation (PBM) is a non-invasive therapy that uses red and near-infrared 
light to stimulate mitochondrial activity, reduce muscle fatigue, and improve recovery. 
This protocol aims to evaluate the effects of whole-body PBM in professional soccer 
players during a state championship. 
2. Methods 
This study is a randomized, placebo-controlled clinical trial conducted in accordance with 
the SPIRIT 2013 guidelines (Chan et al., 2013). 
2.1 Sample Description 
The study sample will consist of a convenience sample comprising athletes from 
a professional soccer team, Desportivo Brasil. This club, located in Porto Feliz, São 
Paulo, is widely recognized for its excellence in player development and high-standard 
facilities, encompassing athletes from multiple youth categories as well as the main 
professional team competing in the São Paulo State Championship – Série A3 Division. 
For this study, only athletes from the professional team will be considered, totaling 
35 active players in the main roster. The predominant age range of these athletes is 
between 18 and 35 years, with anthropometric and physical performance characteristics 
consistent with the high-performance standards required in competitive soccer. 
It is important to emphasize that participation in the study will be voluntary, and 
each athlete will be individually invited to take part in the research. No advantage or 
disadvantage will result from their decision, ensuring ethical conduct and respect for all 
participants. 
2.1.1 Eligibility Criteria 
Inclusion Criteria: 
• Male individuals aged between 18 and 35 years; 

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• Professional soccer players who engage in regular training sessions at least five 
times per week; 
• Availability to participate in all study sessions and assessments; 
• Voluntary participation with signed informed consent. 
Exclusion Criteria: 
• Athletes currently undergoing treatment for injuries or temporarily removed 
from training for medical reasons; 
• Presence of neuromuscular or orthopedic dysfunctions that may impair full 
physical activity or prevent execution of the study protocol; 
• Any condition or medical limitation that may interfere with muscle performance 
or safety during the procedures. 
Study Location and Sample Selection 
Data collection will be conducted at Desportivo Brasil Football Club, located in 
Porto Feliz, São Paulo, Brazil. From a total of 35 professional athletes in the main roster, 
24 participants will be selected based on the sample size calculation described in Section 
3.7. All experimental procedures and assessments will take place within the club 
facilities, ensuring practicality and standardization throughout the process.  
2.1.2 Training Routine Description 
The athletes perform daily training sessions throughout the week, following the 
routine described below: 
Table 1 – Weekly Training Composition 
Period 
Monday 
Tuesday 
Wednesday 
Thursday 
Friday 
Saturday 
Morning 
Rest day 
Strength 
training at 
the gym (30 
min) + 
Field 
session 
(aerobic 
activity – 
60 min) 
Strength 
training at the 
gym (30 min) 
+ Field session 
(aerobic 
activity – 90 
min) 
Strength 
training at 
the gym 
(30 min) 
Field 
session 
(aerobic 
activity – 
45–60 
min) 
Training 
match or 
official 
match 

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Afternoon 
Strength 
training at 
the gym (30 
min) + 
Field 
session 
(aerobic 
activity – 
45 min) 
Field 
session 
(aerobic 
activity – 
60 min) 
Rest 
Field 
session 
(aerobic 
activity – 
60 min) 
Rest 
Day off 
 
This training schedule reflects the standard weekly routine of the professional 
team during the competitive season, ensuring consistency in workload and recovery 
management. 
2.1.3 Randomization and Allocation Concealment 
Participants will be randomly allocated according to the type of intervention 
(PBM or Placebo). The randomization process will be performed using the website 
randomization.com, with participants distributed into two blocks of 12 individuals each. 
To ensure allocation concealment, sealed opaque envelopes will be used, 
containing the randomized assignments: PBM or Placebo. 
Only one researcher (Therapist 1) will be involved in this process and will be 
responsible for administering PBM to all participants. This researcher will be blinded to 
all other assessments, which will be conducted by another investigator (Evaluator 2).  
2.2 Study Design 
The selected participants will be randomly allocated into two balanced groups, as 
follows: 
1) PBM Group: Participants will follow the club’s standard physical training 
program (Table 1), combined with whole-body photobiomodulation (PBM) twice per 
week, after training sessions, on non-consecutive days. 
2) Placebo Group: Participants will follow the club’s standard physical training 
program (Table 1), combined with whole-body placebo photobiomodulation twice per 
week, after training sessions, on non-consecutive days. 
On the first day (T1), participants will undergo the following baseline 
assessments: medical history (anamnesis), jump performance tests (Squat Jump – SJ and 
Countermovement Jump – CMJ), dynamometry, complete blood count, Numeric Rating 

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Scale (NRS) for pain, pain map, and the Pittsburgh Sleep Quality Index – Portuguese 
version (PSQI-PT). 
Subsequently, participants will continue their daily training routines for eight 
weeks, coinciding with the professional soccer championship period. Out of the five 
weekly training sessions, athletes will receive whole-body PBM (or placebo) twice a 
week, always on non-consecutive days and immediately after training. 
The assessments performed at T1—except for anamnesis, sleep quality index, and 
complete blood count—will be repeated weekly (T2). All assessments will be repeated 
again after eight weeks (T3). 
The study design is summarized in Figure 1 below:    

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Figure 1.  Study flow diagram 
 

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2.3 Assessments / Measurement Instruments 
a) Anamnesis: 
During this initial assessment, participants’ personal information will be 
collected, including name, age, medical history, duration of sports practice, body mass, 
height, and body mass index (BMI) calculation. 
 
b) Vertical Jump Tests (SJ - Squat Jump; CMJ - Countermovement Jump):  
Vertical jumps will be performed in two formats: Squat Jump (SJ) and 
Countermovement Jump (CMJ). Both tests will be performed twice, and the mean 
jump height (in centimeters) will be used for analysis. 
Jump height will be measured using a contact platform that records flight time and 
calculates height based on the equations of vertical kinematics: 
ℎ= 𝑡2 × 𝑔× 8−1 
where h = jump height, t = flight time (in seconds), and g = gravitational 
acceleration (9.81 m/s²) (Moreira, Lizana, Martins & Oliveira, 2008). The system 
automatically converts the measured flight time into height values, expressed in 
centimeters. 
To perform the vertical jumps, participants will keep their hands on their hips and 
receive verbal cues before initiating the movement. 
 For the Squat Jump (SJ) test, the athlete will start from a semi-squat position, 
maintaining it for approximately 3 seconds before takeoff. 
For the Countermovement Jump (CMJ) test, the athlete will start from a 
standing position and execute a quick downward movement (squat) immediately followed 
by an upward movement leading to takeoff (Van Hooren & Zolotarjova, 2017). 
 
c) Dynamometry of the Knee Extensor Muscles: 
The manual dynamometry test will be performed on the participant’s dominant 
leg, according to a previous study (Lesnak, Anderson, Farmer, Katsavelis et al., 2019), 
using a portable hand-held dynamometer (Manual Muscle Test – Lafayette 
Instrument). 
The athlete will be seated on a wooden examination table with the legs hanging 
freely over the edge, and the knee positioned at approximately 90° of flexion (Figure 2). 
All participants will perform two maximal voluntary contractions (MVCs), 
each lasting five seconds, with verbal encouragement provided during the test. A one-

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minute rest interval will be allowed between contractions, and the mean value of the 
two attempts will be used for analysis.  
 
 
 
Figure 2.  Positioning for the test adapted from Lesnak et al., 2019. (A) The test will be performed with 
the participant seated, legs hanging freely over the edge of an examination table, with the knee positioned 
at approximately 90° of flexion. A small wedge-shaped cushion will be placed under the distal posterior 
thigh to minimize posterior thigh discomfort, and a standard gait belt will be used to stabilize the thighs on 
the table. Participants will be instructed to keep their arms crossed during the test to isolate quadriceps 
activation. A foam pad will be positioned on the anterior aspect of the leg, where the dynamometer will be 
placed (5 cm proximal to the lateral malleolus), with the strap wrapped around the pad and the device 
anchored to the leg of the table (B). A small elastic wrap will be positioned between the table leg and the 
triceps surae muscle to minimize slack in the strap (A).  
 
d) Complete Blood Count (CBC): 
Blood collection will be performed by qualified professionals from a partner clinical 
analysis laboratory. To ensure convenience and practicality for participants, all 
collections will take place directly in the medical department room of the Desportivo 
Brasil Football Club, eliminating the need for external travel. 
The laboratory professionals will be responsible for bringing all necessary materials 
and equipment to the club and for conducting the tests safely and efficiently, in full 
compliance with biosafety protocols. This approach avoids the need for athletes to travel 
to an external laboratory, thereby minimizing potential interference with their training 
routine and the study protocol. 
The analysis will include the identification and quantification of the following blood 
markers: 
• 
Red Blood Cells (Erythrocytes): Assess the number of red blood cells responsible 
for oxygen transport. 

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• 
Hemoglobin: Measures the concentration of hemoglobin, the protein responsible 
for oxygen carriage within red blood cells. 
• 
Hematocrit: Indicates the proportion of red blood cells in the total blood volume. 
• 
Iron, Ferritin, and Transferrin: The combined evaluation of these parameters 
provides insight into hematologic health and iron homeostasis. Understanding the 
levels of iron, ferritin, and transferrin is crucial for diagnosing and managing 
conditions such as anemia, hemochromatosis (iron overload), and other disorders 
related to iron metabolism. 
 
e)  Numeric Rating Scale (NRS) and Pain Map: 
The perception of delayed onset muscle soreness (DOMS) will be assessed using 
a Numeric Rating Scale (NRS). The scale ranges from 0 to 10, where 0 indicates no 
muscle soreness and 10 represents extreme muscle soreness during a maximal voluntary 
knee 
extension 
performed 
in 
the 
seated 
position 
(see 
Appendices). 
The NRS was selected due to its reliability and responsiveness in assessing pain 
intensity (Ferreira-Valente, Pais-Ribeiro & Jensen, 2011; Thong, Jensen, Miró & Tan, 
2018). 
The location of DOMS will be evaluated using a pain mapping tool (see 
Appendices). Participants will be instructed to color a body chart representing the human 
body from frontal, lateral, and dorsal views. Two variables will be analyzed from the 
drawings: pain extent and pain location (Barbero, Moresi, Leoni, Gatti et al., 2015). 
f)  Pittsburgh Sleep Quality Index – Portuguese Version (PSQI-PT): 
Sleep quality perception will be assessed using the Pittsburgh Sleep Quality Index 
– Portuguese Version (PSQI-PT). 
This instrument consists of 19 self-rated questions covering seven components 
related to sleep, including duration, efficiency, and disturbances. 
The total score ranges from 0 to 21, with higher scores indicating poorer sleep 
quality. 
The PSQI-PT is widely used due to its reliability and validity across different 
populations.  
2.4 Risks and Benefits 
The risks and discomforts involved in this study are minimal and are described 
below according to each stage of the research: 

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Complete Blood Count (CBC): This procedure consists of drawing blood from a 
vein in the antecubital fossa using a 25x8 mm multiple-sample collection needle. A 5 mL 
vacuum collection tube with gel will be attached to the needle. The procedure will be 
performed by a qualified professional from the partner laboratory, using sterile gloves 
and proper aseptic techniques to ensure biosafety. 
Blood collection may cause mild pain or slight bleeding, which typically resolves 
spontaneously within 5 minutes. An adhesive bandage will be applied, and participants 
will be advised to use ice if minor bruising occurs.  
Muscle Soreness Assessment: This assessment involves rating muscle soreness 
using a Numeric Rating Scale (NRS) ranging from 0 to 10, where 0 indicates no pain and 
10 indicates severe pain. Participants will be instructed to sit and perform a maximal 
voluntary isometric knee extension, which may cause temporary muscle soreness or 
discomfort. However, such sensations are normal responses to physical activity and do 
not require medication or intervention, only rest if necessary.  
Jump Tests: This evaluation measures jump height (in centimeters) through four 
jumps—two Squat Jumps (SJ) and two Countermovement Jumps (CMJ). The test is quick 
and painless, though participants may experience mild discomfort upon landing. The 
evaluator will provide guidance on proper posture before each trial to minimize potential 
discomfort.  
Muscle Strength Test: Muscle strength of the quadriceps of the dominant leg will 
be assessed using a portable hand-held dynamometer. Two consecutive measurements 
will be taken. The test poses no harm to participants, though it may cause temporary 
fatigue or mild discomfort due to pressure from the stabilizing strap used during the test. 
To minimize discomfort, foam pads will be placed between the strap and the 
participant’s skin to prevent localized pressure. 
Whole-Body Photobiomodulation (PBM): The therapy is non-invasive, painless, 
and free of adverse effects. Participants may feel a mild warmth on the skin during light 
exposure. All participants and the operator will wear protective goggles, and instructions 
will be provided to avoid looking directly at the LED panels. If accidental exposure 
occurs, participants may experience mild transient visual discomfort, but this will not 
cause ocular damage. The device used in this study is FDA-approved and regulated by 
the U.S. Food and Drug Administration, ensuring safety and compliance with 
international health standards.  

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Potential Benefits: The potential benefits of this study include the identification 
of new therapeutic and ergogenic strategies that may effectively enhance muscle 
performance, accelerate post-training recovery, and reduce delayed-onset muscle 
soreness (DOMS) in athletes. 
 
2.5 Photobiomodulation Protocol (PBM)  
Whole-body photobiomodulation (PBM) will be administered using a Joovv Elite 
System (Figure 3), composed of six panels containing 76 red LEDs (660 ± 10 nm) and 
74 near-infrared LEDs (850 ± 10 nm), totaling 900 LEDs covering an irradiated area 
of 12,193 cm². 
Participants will stand 20 cm in front of the device, wearing only swimming 
trunks to ensure optimal light exposure to the thigh muscles and other body areas. 
The total irradiation time will be 15 minutes (450 seconds for the anterior body and 
450 seconds for the posterior body). 
The effective PBM dose applied to each body region (anterior or posterior) will 
be 25.71 J/cm², with an irradiance of 81.62 mW/cm². 
The placebo condition will consist of sham irradiation, in which the device 
remains turned off. Additional non-therapeutic accessory lights will remain active to 
minimize visual differences between the placebo and the active PBM sessions. 
All PBM (active and placebo) sessions will be performed by a researcher not involved 
in data collection or analysis. 
The order of treatments will follow a simple balanced randomization, as 
illustrated in Figure 1. 
PBM (active or placebo) applications will occur twice per week on non-
consecutive days, always after the standard physical training sessions prescribed by 
the professional soccer club, over a total period of 8 weeks, corresponding to the duration 
of the professional soccer championship. 
In all sessions, participants will wear blindfolds and headphones (listening to 
neutral background music) to prevent visual or auditory bias during treatment. 
All PBM parameters will be verified beforehand using a power and energy meter 
(PM100D, Thorlabs Inc.) equipped with a S130C light sensor (sensitive area = 0.70 cm²). 
. 
 

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Figure 3. Whole-body photobiomodulation using the Joovv Elite System, containing light-emitting diodes 
(LEDs) in the near-infrared (850 nm) and red (660 nm) wavelength ranges.  
 
Photobiomodulation Parameters 
Table 1. Irradiation Parameters (Units) 
Manufacturer 
Joovv 
Wavelength 
Red Light 
Near-Infrared Light 
Central Wavelength (nm) 
660 – 10 
850 – 10 
Number of LEDs (6 panels) 
456 
444 
Beam Area per LED (cm²) 
2,54 
2,54 
Operational Mode 
Continuous 
Continuous 
Distance from Body (cm) 
20 
20 
Radiant Power (mW) 
31,85 
25,29 
Power Density (mW/cm²) 
45,50 
36,13 
Irradiation Time – Front (s) 
450 
450 
Irradiation Time – Back (s) 
450 
450 
Energy Density – Front (J/cm²) 
14,33 
11,38 
Energy Density – Back (J/cm²) 
14,33 
11,38 
Total Average Radiant Power (mW) 
(31,85 + 25,29) = 57,14 
Total Average Power Density (mW/cm²) 
(45,50 + 36,13) = 81,62 
Total Average Energy Density (J/cm²) 
(14,33 + 11,38) = 25,71 
Total Irradiated Area (6 panels, cm²) 
12.193 
Energy Meter Distance (cm) 
20 
20 
Sensor Detection Area (cm²) 
0,70 
0,70 
 
2.6 Sample Size Calculation 
The sample size of 24 participants was calculated a priori using G*Power 3.1 
software, considering two groups and three time points (T1, T2, and T3). 
A two-way repeated-measures analysis of variance (ANOVA) was selected, with a 
minimum effect size of 0.25, statistical power of 80% (1-β = 0.80), and a significance 

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level (α) of 5%. To account for potential participant dropout, a total of 24 participants 
will be recruited. 
2.7 Data Analysis 
Data analysis will be performed by a researcher blinded to group allocation, 
meaning that the evaluator will not have access to participants’ group assignments. 
The primary outcome of the study will be Delayed-Onset Muscle Soreness (DOMS) 
assessed using the Numeric Rating Scale (NRS). 
Descriptive statistics will be used to summarize the data, including absolute and 
relative frequency, mean, and standard deviation. The independent variables will be 
the experimental conditions (i.e., PBM and Placebo) and the assessment time points 
(T1, T2, and T3). 
Assumptions of normality and homogeneity of variances will be tested in 
advance using the Shapiro–Wilk and Levene tests, respectively. 
The dependent variables will include: 
• 
DOMS (measured by NRS) 
• 
Jump height in the Squat Jump (SJ) and Countermovement Jump (CMJ) tests 
• 
Quadriceps muscle strength assessed by manual dynamometry 
A two-way mixed analysis of variance (ANOVA) will be conducted to examine 
the interaction between factors (condition × time) and the main effects of condition 
and time on the dependent variables. When significant interactions are detected, simple 
effects analyses will be performed to identify differences between groups and across time 
points. 
The 
level 
of 
significance 
will 
be 
set 
at 
5% 
(p 
< 
0.05). 
All statistical analyses will be performed using SPSS Statistics for Windows, version 
20.0 (IBM Corp., Chicago, IL, USA).