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Photobiomodulation therapy (PBMT) improves performance and accelerates recovery of high-level Rugby players in field test: A randomized, crossover, double-blind, placebo-controlled clinical study

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  • Universidade Nove de Julho / Vrije Universiteit Amsterdam

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While growing evidence supports the use of photobiomodulation therapy (PBMT) for performance and recovery enhancement, there have only been laboratory-controlled studies. Therefore, the aim of this study was to analyze the effects of PBMT in performance and recovery of high-level rugby players during an anaerobic field test. Twelve male high-level rugby athletes were recruited in this randomized, crossover, double-blinded, placebo-controlled trial. No interventions were performed before the Bangsbo Sprint Test (BST) at familiarization phase (week 1), at weeks 2 and 3 pre-exercise PBMT or placebo were randomly applied to each athlete. PBMT irradiation was performed at 17 sites of each lower limb, employing a cluster with 12 diodes (4 laser diodes of 905nm, 4 LED diodes of 875nm, and 4 LED diodes of 640nm, 30J per site - manufactured by Multi Radiance Medical™). Average time of sprints, best time of sprints, and fatigue index were obtained from BST. Blood lactate levels were assessed at baseline, and at 3, 10, 30 and 60 minutes after BST. Athletes' perceived fatigue was also assessed through a questionnaire. PBMT significantly (p<0.05) improved average time of sprints and fatigue index in BST. PBMT significantly decreased percentage of change in blood lactate levels (p<0.05) and perceived fatigue (p<0.05). Pre-exercise PBMT with the combination of super-pulsed laser (low-level laser), red and infrared LEDs can enhance performance and accelerate recovery of high-level rugby players in field test. This opens a new avenue for wide use of PBMT in real clinical practice in sports settings.
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PHOTOBIOMODULATION THERAPY IMPROVES
PERFORMANCE AND ACCELERATES RECOVERY OF
HIGH-LEVEL RUGBY PLAYERS IN FIELD TEST:A
RANDOMIZED,CROSSOVER,DOUBLE-BLIND,PLACEBO-
CONTROLLED CLINICAL STUDY
HENRIQUE D. PINTO,
1,2
ADRIANE A. VANIN,
1,2
EDUARDO F. MIRANDA,
1
SHAIANE S. TOMAZONI,
3
DOUGLAS S. JOHNSON,
4
GIANNA M. ALBUQUERQUE-PONTES,
1,5
IVO DE O. ALEIXO JUNIOR,
1,2
VANESSA DOS S. GRANDINETTI,
5
HELIODORA L. CASALECHI,
1,2
PAULO DE TARSO C. DE CARVALHO,
1,2,5
AND ERNESTO CESAR P. LEAL JUNIOR,
1,2,5
1
Laboratory of Phototherapy in Sports and Exercise, University of Nove de Julho (UNINOVE), Sa˜o Paulo, Brazil;
2
Postgraduate Program in Rehabilitation Sciences, University of Nove de Julho (UNINOVE), Sa˜o Paulo, Brazil;
3
Department
of Pharmacology, University of Sa˜o Paulo, Sa˜o Paulo, Brazil;
4
Multi Radiance Medical, Solon, Ohio; and
5
Postgraduate
Program in Biophotonics Applied to Health Sciences, University of Nove de Julho (UNINOVE), Sa˜o Paulo, Brazil
ABSTRACT
Pinto, HD, Vanin, AA, Miranda, EF, Tomazoni, SS, Johnson, DS,
Albuquerque-Pontes, GM, de Oliveira Aleixo Junior, I, Grandi-
netti, VdS, Casalechi, HL, de Tarso Camillo de Carvalho, P,
and Pinto Leal Junior. Photobiomodulation therapy improves
performance and accelerates recovery of high-level rugby
players in field test: A randomized, crossover, double-blind,
placebo-controlled clinical study. J Strength Cond Res 30(12):
3329–3338, 2016—Although growing evidence supports the
use of photobiomodulation therapy (PBMT) for performance
and recovery enhancement, there have only been laboratory-
controlled studies. Therefore, the aim of this study was to ana-
lyze the effects of PBMT in performance and recovery of high-
level rugby players during an anaerobic field test. Twelve male
high-level rugby athletes were recruited in this randomized,
crossover, double-blinded, placebo-controlled trial. No inter-
ventions were performed before the Bangsbo sprint test
(BST) at familiarization phase (week 1); at weeks 2 and 3,
pre-exercise PBMT or placebo were randomly applied to each
athlete. Photobiomodulation therapy irradiation was performed
at 17 sites of each lower limb, employing a cluster with 12
diodes (4 laser diodes of 905 nm, 4 light emitting diodes
[LEDs] of 875 nm, and 4 LEDs of 640 nm, 30 J per site,
manufactured by Multi Radiance Medical). Average time of
sprints, best time of sprints, and fatigue index were obtained
from BST. Blood lactate levels were assessed at baseline, and
at 3, 10, 30, and 60 minutes after BST. Athletes’ perceived
fatigue was also assessed through a questionnaire. Photobio-
modulation therapy significantly (p#0.05) improved the
average time of sprints and fatigue index in BST. Photobiomo-
dulation therapy significantly decreased percentage of change
in blood lactate levels (p#0.05) and perceived fatigue (p#
0.05). Pre-exercise PBMT with the combination of super-
pulsed laser (low-level laser), red LEDs, and infrared LEDs
can enhance performance and accelerate recovery of high-
level rugby players in field test. This opens a new avenue for
wide use of PBMT in real clinical practice in sports settings.
KEY WORDS low-level laser therapy, light emitting diodes,
sport, exercise, phototherapy
INTRODUCTION
The sport of rugby consists of intense physical activ-
ity with frequent bursts of high-intensity activities
such as sprinting, tackling, and blocking inter-
mingled with short intervals of low-intensity activ-
ities (between 4 and 8 seconds) like standing, walking or
jogging. Preparation for play requires training to focus on
a combination of muscular strength, power, agility, speed,
aerobic, and anaerobic endurance (4,8,9,15,25).
Varley et al. (25) compared activity profiles between
rugby, American football and soccer players, and concluded
that rugby players have less running load in matches. How-
ever, the frequent collisions increase the high-intensity ef-
forts when compared with other noncollision sports. As
Address correspondence to Ernesto Cesar P. Leal Junior, ernesto.leal.
junior@gmail.com.
30(12)/3329–3338
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a high-intensity sport, rugby creates a higher physical
demand and requires better conditioning from players. Iden-
tifying methods that not only promote recovery but also
accelerate it are crucial to minimize accumulating fatigue
and risk of overuse injuries.
This is highly important in Rugby Sevens (7s), where the
number of field players is limited to 7 rather than 15 on
a full-sized field. This version of rugby increases the
physical demands on the athletes and potentiates perceived
fatigue. Moreover, according to tournament format, teams
will play several matches per day with only a few hours
between, to recover from physical and physiological stress
(8). Johnston et al. (15) state that symptoms of fatigue
appear immediately after a match and usually persist for
some days. Damage to large muscles, physiological stress,
and impairments in muscle function are commonly seen in
players, resulting in a decrease in field performance and
skill (15). It is necessary to employ strategies that enhance
and accelerate recovery after matches to best prepare the
athlete for the next match.
Photobiomodulation therapy (PBMT), with lasers or light
emitting diodes (LEDs), has been shown to prevent skeletal
muscle fatigue and accelerate recovery (20). Previous studies
have demonstrated that PBMT is able to reduce muscular
fatigue, increase contraction strength, and muscle perfor-
mance (16,19,20). Photobiomodulation therapy may prevent
the onset of fatigue during activity, thereby improving ath-
letic performance (20). Photobiomodulation therapy is
a nonthermal (11), commercially available modality that
can be used in a variety of clinical and athletic settings.
The effects of P BMT are related to photochemical and pho-
tobiological effects within the tissue, and are not attributed
to heat (11). Photobiomodulation therapy modulates biolog-
ical processes of cells on mitochondrial level, increasing the
oxygen consumption, and production of adenosine triphos-
phate (ATP) (13).
Several studies have demonstrated the positive effects of
PBMT on the improvement of biochemical markers related
to muscle damage and recovery (20), including blood lactate
levels. Furthermore, PBMT decreases the recovery time
needed between exercise sessions (16,19). More recently,
the literature showed beneficial effects in muscular recovery
when PBMT is applied using a combination of different
wavelengths synergistically (3,22), which suggests that the
combined use of different wavelengths may optimize cyto-
chrome c oxidase modulation, increasing the effects of
PBMT (1).
Currently, all randomized clinical trials performed in
this field demonstrating PBMT effectiveness in perfor-
mance enhancement and accelerating recovery have been
conducted in laboratory-controlled environment. To dem-
onstrate real world application and translation to clinical
practice, field tests are required to confirm the outcomes
seen in the controlled laboratory trials. Therefore, the aim
of this study is to analyze the effects of PBMT, with
a combination of different wavelengths and light sources
(lasers and LEDs), on performance and recovery of
high-level rugby players in a noncontrolled field test
environment.
METHODS
Experimental Approach to the Problem
A randomized, crossover, double-blind, placebo-controlled,
clinical study was performed. To our knowledge, this novel
study is the first to analyze the effects of PBMT on
performance and recovery in professional athletes in an
uncontrolled environment field test. Our hypothetical pre-
sumption was that PBMT can enhance athletes’ perfor-
mance in field test, accelerate blood lactate clearance, and
lead athletes to decreased perceived fatigue. The Bangsbo
sprint test (BST) (6) was chosen as field test because it
mimics key actions performed during rugby matches, such
as sprints, change of direction, and active recovery between
sprints (low-intensity running), and it is widely used by
rugby teams to testing athletes’ anaerobic performance.
We decided to assess blood lactate levels, because it is a bio-
chemical marker related to anaerobic metabolism and mus-
cular acidosis (7,14,21), and it is often monitored in sports
settings to evaluate athletes’ recovery. Finally, the fatigue
questionnaire (8) was used to evaluate athletes’ perceived
fatigue for each experimental condition tested. The depen-
dent variables measured were blood lactate levels; per-
ceived fatigue score (from questionnaire); mean sprint
time (ST-mean), best sprint time (ST-best) and fatigue
index from BST. The independent variables were, treat-
ment with 3 levels (familiarization, placebo-control, and
PBMT), and time for blood lactate (baseline, 3, 10, 30,
and 60 minutes post).
Subjects
The study was approved by institutional ethics committee
(process 665.347), and written informed consent was
obtained from all volunteers. The number of participants
per group was determined based on a previous study
conducted by Antonialli et al. (3) using the same PBMT
device of the current study. A total of 12 high-level male
rugby players with a mean age of 23.50 (62.32) years
(ranging 19–26-year-old), height of 178.00 (64.79) cm,
and mean body mass of 86.00 (67.63) kg were recruited
from Sa
˜oJose
´Rugby Club (Brazil), and all experimental
procedures for this study were completed with no drop-
outs. Each athlete played a minimum of once for the Brazil-
ian national team with a mean time of sports practice of
9.33 (62.99) years.
Athletes were excluded if skeletal muscle injury was
present, currently use any nutritional supplement or phar-
macological agent, presented signs and symptoms of any
disease (i.e., neurological, inflammatory, pulmonary, meta-
bolic, and oncologic), and had history of cardiac arrest that
may limit performance of high-intensity exercises.
PBMT Improves Performance and Recovery in Rugby Players
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A simple drawing of lots was used to determine which
treatment each participant would receive at second and third
exercise tests. Photobiomodulation therapy device was pre-
set to either Program 1 or Program 2 which corresponded to
either active PBMT or the placebo treatment. The
researcher that programmed the devices only knew the
identity of the devices as either active or placebo, and was
instructed to not inform the participants or other researchers
about the specific device programming.
Randomization labels were created using a randomiza-
tion table at a central office, where a series of sealed,
opaque, and numbered envelopes were used to ensure
confidentiality. The researcher who programmed the
PBMTdevicebasedontherandomizationresultsper-
formed randomization. Thus, the researcher who applied
PBMT was blinded to which treatment was provided to the
volunteers. Blinding was further maintained by the use of
opaque goggles by the participants. Because this is a cross-
over study, participants who received Program 1 at second
exercise test, received Program 2 at third exercise test, and
vice-versa. Randomization was balanced to ensure that
50% of athletes would receive active PBMT at second
exercise test, and other 50% would receive active PBMT at
third exercise test, avoiding further learning bias in our
outcomes. The study conforms to the Code of Ethics of the
World Medical Association and required players to provide
informed consent before participation.
Procedures
All exercise tests were conducted in an enclosed soccer or
rugby field. The 3 test phases, administered 1 week apart,
were performed on the same day of the week (Tuesday) and
time (1–5 PM). The average temperature inside the building
during the trials ranged from 26 to 288C. At first phase
(exercise test 1) all athletes performed the BST (6) to famil-
iarize with the procedure. No treatments were applied at this
phase. However, at the second and third phases (exercise
tests 2 and 3, respectively) either a placebo or active PBMT
was applied just before the athletes perform stretching and
warm-up according to randomization. All procedures are
summarized in Figure 1.
Blood Samples
Blood samples were collected from the athlete’s fingertips
before stretching and warm-up (baseline), and at 3, 10, 30,
and 60 minutes after BST at each of the 3 study stages or
phase (exercise tests). After finger asepsis with alcohol, punc-
ture was performed with a disposable lancet. The first blood
drop was discarded to avoid contamination with sweat, and
Figure 1. CONSORT flowchart summarizing study procedures. BST = bangsbo sprint test; PBMT = photobiomodulation therapy.
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then 25 ul of blood was collected for biochemical analysis
through electroenzymatic method, according to the instruc-
tions of the portable lactate analyzer manufacturer (Accu-
trend Lactate Plus Roche, Roche Diagnostics GmbH,
Mannheim, Germany). The analyzer has a coefficient of var-
iation between 1.8 and 3.3% (intraclass correlation [ICC] r=
0.999), with good reliability for intra-, inter-analyzers, and
between test strips (5).
Stretching and Warm-Up
After blood sample collection (to establish baseline), athletes
performed a standardized warm-up and stretching; the same
stretching and warm-up procedure was performed at each
Figure 2. Sites of PBMT irradiation at anterior muscles of the lower
limbs. PBMT = photobiomodulation therapy.
Figure 3. Sites of PBMT irradiation at posterior muscles of the lower
limbs. PBMT = photobiomodulation therapy.
PBMT Improves Performance and Recovery in Rugby Players
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phase of study. The stretching lasted about 5 minutes and
comprised dynamic stretches (30 seconds each) for knee
extensors (bilaterally), knee flexors (bilaterally), calf muscles
(bilaterally), and low-back and abdominal muscles. The
stretching was followed by a warm-up comprised of low-
intensity short running for 10 minutes. The stretching and
warm-up lasted about 15 minutes, followed by 5 minutes of
rest. At phases 2 and 3, the stretching and warm-up
procedure was performed immediately after PBMT or
placebo treatments.
Bangsbo Sprint Test
The BST was performed immediately after stretching and
warm-up procedure, and 5 minutes of rest. Therefore, in
exercise tests 2 and 3, BST started about 20 minutes after
PBMT or placebo.
The BST protocol consists of 7 maximum sprints 34.2 (m)
in length (A–E). The time of each sprint was measured by
infrared photocells positioned at the start (A) and finish line
(E) of the track (34.2 m). The athlete changes direction after
crossing cone “B,” to reach cone “C” (approximately 90 de-
grees), then runs to cone “D” and finally cone “E.” At each
sprint, the side to change direction is alternated (right and
left, consecutively). The first change of direction was per-
formed according to athletes’ preference in exercise test 1,
and the same order for change of direction was kept for
exercise tests 2 and 3 (6).
Active recovery between sprints was performed with a 25-
second low-intensity run of 40 meters to return to the
starting position on the track (F–A). The time of recovery
and return to start was moni-
tored with a manual chronom-
eter to ensure a consistent
return to starting position
within 20–22 seconds. Verbal
commands and cues were used
to encourage the athletes and to
provide feedback regarding the
remaining time for recovery,
and to start the next sprint (6).
According to Wragg et al. (26),
the BST has high reliability and
presents a subject mean coeffi-
cient of variation of 1.8% (95%
confidence interval, 1.5–2.4).
Performance was evaluated
by computing the average time
of sprints performed during
entire test (ST-mean) and for
the fastest (best) time (ST-best)
among the 7 sprints performed
at each test. In addition, fatigue
index was calculated using the
following equation: FI (%) =
(STmean/Stbest 3100) 2
100 to measure the percentage of decrease in performance
between all sprints (6,26). This index is important because it
shows the percentage of decrease in performance of athletes
over the repeated sprints.
Questionnaire of Fatigue
A quick perception of fatigue survey was administered
5 minutes after each exercise test to evaluate athletes’ per-
ceived fatigue for each experimental condition tested. The
questionnaire consisted of 8 questions pertaining to percep-
tion of training, sleep, leg pain, concentration, effectiveness,
anxiety, irritability, and stress. Each question was evaluated
according to a score scale where 1–2 points corresponded to
“not at all,” 3–4 points to “normal,” and 5–7 to “very much.”
The scores were calculated according to the relative impor-
tance of each question, and a lower score indicated better
general well-being perception, and a higher score demon-
strated greater fatigue perception (8). This questionnaire was
used in a previous study (8), and demonstrated a high reli-
ability and very good correlation (r= 0.63–0.83) with objec-
tive measures of fatigue and performance, which
demonstrates that this questionnaire is a sensitive tool for
monitoring fatigue.
Intervention
Photobiomodulation Therapy. Photobiomodulation therapy
was applied employing MR4 Laser Therapy Systems out-
fitted with LaserShower 50 4D emitters (both manufactured
by Multi Radiance Medical, Solon, OH, USA). The cluster
style emitter contains 12 diodes comprising 4 super-pulsed
laser diodes (905 nm, 0.3125 mW average power, and 12.5 W
Figure 4. Bangsbo sprint test (BST).
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peak power for each diode), 4 red LED (640 nm, 15 mW
average power for each diode), and 4 infrared LEDs (875
nm, 17.5 mW average power for each diode).
TABLE 1. Parameters for PBMT.*
Number of lasers 4 Super-pulsed infrared
Wavelength (nm) 905 (61)
Frequency (Hz) 250
Peak power (W)–each 12.5
Average mean optical
output (mW)–each
0.3125
Power density
(mW/cm
2
)–each
0.71
Energy density
(J/cm
2
)–each
0.162
Dose (J)–each 0.07125
Spot size of laser
(cm
2
)–each
0.44
Number of red LEDs 4 red
Wavelength of red
LEDs (nm)
640 (610)
Frequency (Hz) 2
Average optical output
(mW)–each
15
Power density
(mW/cm
2
)–each
16.66
Energy density
(J/cm
2
)–each
3.8
Dose (J)–each 3.42
Spot size of red LED
(cm
2
)–each
0.9
Number of infrared LEDs 4 infrared
Wavelength of
infrared LEDs (nm)
875 (610)
Frequency (Hz) 16
Average optical output
(mW)–each
17.5
Power density
(mW/cm
2
)–each
19.44
Energy density
(J/cm
2
)–each
4.43
Dose (J)–each 3.99
Spot size of LED
(cm
2
)–each
0.9
Magnetic Field (mT) 35
Irradiation time per
site (s)
228
Total dose per site (J) 30
Total dose applied per
lower limb (J)
510
Aperture of device (cm
2
)20
Application mode Cluster probe held
stationary in skin
contact with a 908
angle and slight
pressure
*PBMT = photobiomodulation therapy; LED = light
emitting diode.
Figure 5. Outcomes observed in BST, values are mean and error bars
are SEM.
a
significant difference compared with familiarization (p#0.05),
b
significant difference compared with placebo (p#0.05). BST =
bangsbo sprint test; SEM = standard error of mean; PBMT =
photobiomodulation therapy.
PBMT Improves Performance and Recovery in Rugby Players
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The cluster probe was selected because of the available
coverage area, and to reduce the number of sites needing
treatment. Treatment was applied in direct contact with the
skin with a slight applied overpressure to 9 sites on extensor
muscles of the knee (Figure 2), 6 sites on knee flexors, and 2
sites on the calf (Figure 3) of both lower limbs (22). To
ensure blinding, the device emitted the same sounds, regard-
less of the programmed mode (active or placebo). Further-
more, because the device produces a nonsignificant amount
of heat (11), the volunteers were not able to know if active or
placebo PBMT was administered. A total of 17 emitters were
used to apply the treatments, all sites of left leg were irradi-
ated simultaneously at first, fol-
lowed by all sites of right leg.
The treatments lasted about
10 minutes. The researcher,
who was blinded to randomi-
zation and the programming
of PBMT device, performed
the phototherapy. Figure 4
Photobiomodulation ther-
apy parameters and irradiation
sites were selected based upon
previous positive outcomes
demonstrated with the same
device (3,22). Table 1 provides
a full description of the PBMT
parameters.
Statistical Analyses
The number of participants per
group was determined based
on a previous study conducted
by Antonialli et al. (3) using the
same PBMT device of the cur-
rent study; for sample size cal-
culation we considered the
b-value of 20% and aof 5%.
The Kolmogorov-Smirnov test
was used to verify the normal
distribution of data. The col-
lected data demonstrated nor-
mal distribution, therefore the
data were expressed in mean
values and SD. The one-way
analysis of variance test fol-
lowed by the Bonferroni post
hoc test was performed to ver-
ify statistical significance. The
level of statistical significance
was set at p#0.05. In graphs,
data are presented as mean and
standard error of the mean.
The intention-to-treat analysis
would be followed a priori,
however, there were no dropouts in this study. The ICCs
for dependent measures were ST-mean (0.82), ST-best (0.62),
fatigue index (0.58), blood lactate (0.99), and perceived
fatigue score (0.40).
RESULTS
The average time of sprints (ST-mean) was significantly
different (p#0.05) between familiarization (6.91 60.24
seconds) and placebo (6.67 60.21 seconds), and familiariza-
tion and PBMT (6.55 60.21 seconds). Significant difference
(p#0.05) was also demonstrated between PBMT and pla-
cebo groups.
Figure 6. Blood lactate levels, values are mean and error bars are SEM.
a
significant difference compared with
familiarization (p#0.05),
b
significant difference compared with placebo (p#0.05). SEM = standard error of
mean; PBMT = photobiomodulation therapy.
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For the best time among all 7 sprints (ST-best), there was
significant difference (p#0.05) between familiarization (6.63
60.25 seconds) and placebo (6.38 60.20 seconds), and
between familiarization and PBMT (6.38 60.21 seconds, p
#0.05). However, no observed difference between PBMT
and placebo (p.0.05) was seen.
Regarding fatigue index during BST, a significant difference
(p#0.05) was observed between PBMT (2.66% 60.61) and
familiarization (4.19% 60.98), and between PBMT and pla-
cebo (4.51% 60.95, p#0.05). No differences were observed
between familiarization and placebo (p.0.05). All outcomes
observed during the BST are summarized in Figure 5.
Although no statistical differences (p.0.05) regarding
blood lactate levels in absolute values among conditions
tested was observed, the percentage of decrease in the levels
was significant (p#0.05) in favor of PBMT, when compar-
ing both with familiarization and placebo at all postexercise
time points tested (Figure 6).
Lastly, the perceived fatigue was significantly lower (p#
0.05) when athletes received pre-exercise PBMT (20.16 6
3.63), when comparing both to familiarization (23.08 6
1.92) and placebo (23.50 62.50). Outcomes are summarized
in Figure 7.
DISCUSSION
This study details an important first step for the adoption of
PBMT by both professional sports teams and high-level
athletes, and represents the bridge between laboratory
controlled studies and real world clinical practice.
Bangsbo (6) proposes the use of the BST due the inclusion
of directional change and the active recovery between the 7
sprints. According to Wragg et al. (26), a reliable field test
must be sport-specific, and reliably represent the activities of
an individual sport. Only a few field tests contain these fea-
tures (26) that mimic the key actions performed during
rugby matches.
Although no change was found between the active and
placebo PBMT for ST-best, significant improvement was
observed in the ST-mean. It was noted that active PMBT
maintained an optimal running performance over the entire
7 sprints that lead to a significant decrease in the fatigue
index, when there is typically a decrease in performance as
the test progresses (10). Photobiomodulation therapy was
successfully able to maintain the athlete’s running speed over
the entire series of sprint tests.
Fatigue is comprised of multifactorial components and
can be generally characterized as a decreasing generation
of force (2,10,12). Girard et al. (10) explains that fatigue
development is associated with the intramuscular accu-
mulation of metabolic byproducts such as hydrogen ions
and blood lactate, which changes cellular pH. Metabolite
accumulation can impair contractile function through
inhibition of ATP production, which affects muscular
performance.
Blood lactate concentration is considered an important
biochemical marker of muscular acidosis and it is often
monitored in sports settings, mainly in high-intensity sports
(7,14,21). No statistical difference was observed in the abso-
lute values of blood lactate levels in between treatments or
when compared with the familiarization test. Higher levels
of this biochemical marker should be and were expected in
the active PBMT groups, because the athlete’s performance
was significantly better.
Therefore, it is reasonable to state that active PBMT
prevented the expected increase of blood lactate levels,
reduced muscular fatigue, and promoted faster recovery after
exercise bouts. These findings are consistent with previous
reports that observed the same beneficial effects of PBMTon
muscle recovery after a high-intensity exercise (17–19).
There was a significant decrease in favor of the active PBMT
compared with other 2 tested conditions (familiarization and
placebo), when the percentage change in blood lactate levels
were calculated.
As stated by Mohr et al. (23) in their review, increased
lactate levels indicate muscular fatigue or acidosis that is
associated with anaerobic metabolism during intense exer-
cise activity. High levels of blood lactate are related to
impaired performance during intense muscular contraction
(21,23). The average blood lactate levels 3–10 minutes after
exercise test observed in this study was 15.10–12.91
mmol$L
21
for placebo, 14.00–12.28 mmol$L
21
for familiar-
ization, and 14.11–11.95 mmol$L
21
for PBMT condition,
respectively. Our observations demonstrated that the exper-
imental condition with the lowest lactate levels also
Figure 7. Perceived fatigue, values are mean and error bars are SEM.
a
significant difference compared with familiarization (p#0.05),
b
significant
difference compared with placebo (p#0.05). SEM = standard error of
mean; PBMT = photobiomodulation therapy; AU = Arbitrary Unit.
PBMT Improves Performance and Recovery in Rugby Players
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correlated with lower fatigue index ratings, which suggests
that improved performance can be accomplished by
decreasing muscle acidosis in high-intense sports activities
by applying PBMT before activity. However, additional
research in this novel area is needed to provide insights into
other sport-specific activities, and about mechanisms
through which PBMT acts.
Our study employed the same short questionnaire by
Elloumi et al. (8) previously used with rugby players to eval-
uate perceived fatigue in rugby athletes among experimental
conditions, and was sensitive enough to assess physical effort
and perception of fatigue (8). Our outcomes demonstrated
that when irradiated with active PBMT, athletes presented
a lower index of fatigue perception. This finding corrobo-
rates with other assessments performed in this study such as
fatigue index in BST and blood lactate levels. According to
Halson (12), a reliable questionnaire must corroborate with
collected physiological data, and our outcomes have dem-
onstrated this.
It should be noted that the parameters chosen for PBMT
treatment in our study were selected based upon 2 pre-
viously published studies using the same device where
positive effects were noted (3,22). Antonialli et al. (3) tested
3 different doses against a placebo-control dose of 0 J, and
found that 30 J was the best dose tested (compared with 10
J, 50 J, and placebo), that significantly increased perfor-
mance, decreased the delay of onset muscle soreness, and
modulated Creatine Kinase activity. A crossover study per-
formed by Miranda et al. (22) found significant decreases in
dyspnea sensation, improvement in time until exhaustion,
pulmonary ventilation, and distance covered when PBMT
was applied before the progressive-intensity cardiopulmo-
nary test. The main muscular groups of both lower limbs
were irradiated. We used the same irradiation sites used by
Miranda et al. (22) to provide reasonable coverage of the
major muscles of the lower extremity needed to perform
the exercise protocol (BST).
Photobiomodulation therapy demonstrates a modulatory
effect on cytochrome c oxidase activity, and can explain
how PBMT improves performance while protecting skel-
etal muscle from exercise-induced muscle damage. This has
been considered the key mechanism for light-tissue inter-
action, promoting increase in cellular metabolism through
increased mitochondrial function (1). Furthermore,
Albuquerque-Pontes et al. (1) have demonstrated that cyto-
chrome c oxidase activity stimulation by different wave-
lengths and doses occurs along different time-profiles.
This suggests that PBMT stimulation can be optimized
when different wavelengths are used simultaneously (1).
These optimized PBMT effects were supported by Santos
et al. (24), when different wavelengths and doses were
applied immediately before tetanic contractions. They re-
ported positive effects on several markers of skeletal muscle
performance and the protective effects on skeletal muscle
tissue (24).
Finally, our outcomes demonstrate the potential use of
PBMT as a prophylactic strategy for performance and
recovery enhancement of high-level athletes, and it is an
important step for wide clinical use of this therapeutic
tool.
PRACTICAL APPLICATIONS
The same outcomes previously observed in controlled-
laboratory environment were confirmed in this study. Pre-
exercise PBMT enhances performance and accelerates
recovery of high-level rugby players, which may represent
a shift in current clinical practice with wide use of PBMT in
sports settings. Photobiomodulation therapy seems to have
the potential to keep athletes at higher performance level,
and consequently help to avoid injuries because of impaired
recovery.
ACKNOWLEDGMENTS
The authors thank all rugby athletes that voluntarily
participated this study, and to Sa
˜o Jose
´Rugby.
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PBMT Improves Performance and Recovery in Rugby Players
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