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Effect of 830 nm low-level laser therapy applied before
Lasers Med Sci
DOI 10.1007/s10103-008-0633-4
ORIGINAL ARTICLE
Effect of 830 nm low-level laser therapy applied before
high-intensity exercises on skeletal muscle recovery
in athletes
Ernesto Cesar Pinto Leal Junior &
Rodrigo Álvaro Brandão Lopes-Martins &
Bruno Manfredini Baroni & Thiago De Marchi &
Daiana Taufer & Débora Sgandella Manfro &
Morgana Rech & Vanessa Danna & Douglas Grosselli &
Rafael Abeche Generosi & Rodrigo Labat Marcos &
Luciano Ramos & Jan Magnus Bjordal
Received: 22 September 2008 / Accepted: 31 October 2008
# Springer-Verlag London Ltd 2008
Abstract Our aim was to investigate the immediate effects of
bilateral, 830 nm, low-level laser therapy (LLLT) on highintensity exercise and biochemical markers of skeletal muscle
recovery, in a randomised, double-blind, placebo-controlled,
crossover trial set in a sports physiotherapy clinic. Twenty
male athletes (nine professional volleyball players and eleven
adolescent soccer players) participated. Active LLLT (830 nm
wavelength, 100 mW, spot size 0.0028 cm2, 3–4 J per point)
or an identical placebo LLLT was delivered to five points in
the rectus femoris muscle (bilaterally). The main outcome
measures were the work performed in the Wingate test: 30 s
of maximum cycling with a load of 7.5% of body weight,
and the measurement of blood lactate (BL) and creatine
kinase (CK) levels before and after exercise. There was no
significant difference in the work performed during the
Wingate test (P>0.05) between subjects given active LLLT
and those given placebo LLLT. For volleyball athletes, the
change in CK levels from before to after the exercise test
was significantly lower (P=0.0133) for those given active
LLLT (2.52 U l−1 ± 7.04 U l−1) than for those given placebo
LLLT (28.49 U l−1 ± 22.62 U l−1). For the soccer athletes,
the change in blood lactate levels from before exercise to
E. C. P. Leal Junior (*) : B. M. Baroni : T. De Marchi :
D. Grosselli : R. A. Generosi
Laboratory of Human Movement (LMH),
Sports Medicine Institute (IME),
University of Caxias do Sul (UCS),
Rua Francisco Getúlio Vargas, 1130,
95070–560 Caxias do Sul, RS, Brazil
e-mail: [email protected]
R. Á. B. Lopes-Martins : R. L. Marcos : L. Ramos
Laboratory of Pharmacology and Phototherapy of Inflammation,
Department of Pharmacology, Institute of Biomedical Sciences,
University of São Paulo (USP),
São Paulo, SP, Brazil
E. C. P. Leal Junior : B. M. Baroni : R. A. Generosi
Sports Medicine Institute (IME),
University of Caxias do Sul (UCS),
Caxias do Sul, RS, Brazil
E. C. P. Leal Junior : J. M. Bjordal
Section for Physiotherapy Science,
Institute of Public Health and Primary Health Care,
University of Bergen,
Bergen, Norway
T. De Marchi : D. Taufer : D. S. Manfro : M. Rech : V. Danna
Faculty of Physiotherapy, University of Caxias do Sul (UCS),
Caxias do Sul, RS, Brazil
R. A. Generosi
Federal University of Rio Grande do Sul (UFRGS),
Porto Alegre, RS, Brazil
D. Grosselli
Faculty of Physical Education, University of Caxias do Sul (UCS),
Caxias do Sul, RS, Brazil
J. M. Bjordal
Institute for Physical Therapy, Bergen University College,
Bergen, Norway
Lasers Med Sci
15 min after exercise was significantly lower (P<0.01) in the
group subjected to active LLLT (8.55 mmol l −1 ±
2.14 mmol l−1) than in the group subjected to placebo LLLT
(10.52 mmol l−1 ± 1.82 mmol l−1). LLLT irradiation before
the Wingate test seemed to inhibit an expected post-exercise
increase in CK level and to accelerate post-exercise lactate
removal without affecting test performance. These findings
suggest that LLLT may be of benefit in accelerating postexercise recovery.
Keywords LLLT . Skeletal muscle .
Skeletal muscle recovery . Blood lactate . Creatine kinase .
Muscle damage . Sports
Introduction
Skeletal muscle fatigue is an inevitable phenomenon in the
training and competition routine for most athletes and can
impair their performance and predispose the athlete to a
variety of musculoskeletal disorders. This kind of harm
may be transient, lasting minutes or hours after exercise,
but it can also last for several days [1]. In the first few hours
physical performance is impaired by metabolic disturbances
that occur after high-intensity exercises [2]. When physical
performance is impaired for days, this may be related to
tissue injuries caused by exercise and the phenomenon
known as delayed-onset muscle soreness (DOMS) [3].
A large number of therapeutic modalities are used in
sports rehabilitation to accelerate muscle recovery after
exercises, such as: active recovery [4–6] cryotherapy [3, 7,
8], massage [5, 9], contrast heat therapy (immersion in hot
and cold water) [10, 11], hydrotherapy [12], stretching [1],
hyperbaric oxygen therapy [13], non-steroidal anti-inflammatory drugs (NSAIDs) [14] and electrostimulation [15].
While some authors [1, 2, 16] discuss the validity of the
blood lactate concentration as a parameter to determine the
muscle recovery after exercise, this method has been widely
used for this purpose [4–6]. For example, active recovery
through low-intensity exercises seems to accelerate lactate
removal from the muscle and increase blood circulation [5,
17], and some studies [4, 18] also suggest that this
therapeutic modality can improve performance.
Serum levels of skeletal muscle enzymes are markers of
the functional status of muscle tissue and vary widely in
both pathological and physiological conditions. Early
increased levels of some of these enzymes are associated
with later cellular necrosis and tissue damage in acute and
chronic muscle injuries [19].
The changes in serum levels of muscular enzymes and
isoenzymes are also found in healthy subjects and in
athletes after strenuous exercise [20, 21], and the levels of
enzymes from muscle tissue in blood can be influenced by
physical exercise [22]. The activity of creatine kinase (CK),
measured from muscle needle biopsies, changes during and
after training bouts [23], and the serum level of CK changes
according to different training protocols and their respective
intensities and types of training [24, 25].
CK levels are important in sport medicine for obtaining
information on the current state of the muscle integrity [26].
High levels of serum CK in apparently healthy subjects is
normal after physical work. However, if a high level
persists at rest, it may be a sign of subclinical muscle
disease, which may trigger the onset of symptoms such as
profound fatigue when physical work is performed [27].
Skeletal muscle fatigue is a novel area of research in
low-level laser therapy (LLLT), and the optimal parameters
of LLLT application are not fully understood. In clinical
settings, LLLT has been used in the treatment of musculoskeletal pain. Some positive findings in conditions such as
neck muscle pain [28] and fibromyalgia [29] may be related
to the same mechanisms that cause skeletal muscle fatigue.
In a previous experiment on animals, we dissected the
anterior tibialis muscle from the distal insertion and
removed the skin before irradiating the muscle with red
LLLT (655 nm). In this experimental set-up we found that
some doses of LLLT delayed the inevitable decline in
maximal contraction during repeated electrically induced
tetanic contractions [30]. Specific doses of LLLT also
significantly reduced muscle CK activity when compared
with that in non-irradiated groups.
Laser light penetration through human skin may pose a
problem in clinical settings, and infrared wavelengths have
better skin penetration ability than red wavelengths have
[31]. In addition, there are some indications from animal
studies that infrared laser wavelengths may be effective in
reducing the release of reactive oxygen species (ROS) and
may increase the content of antioxidants and heat shock
proteins [32, 33]. For these reasons we decided to
investigate if an infrared wavelength (830 nm) would have
effects on skeletal muscle recovery in a homogeneous
sample of elite athletes, and if there were differences in
effects between active LLLT and placebo LLLT in the same
athletes in a crossover design.
Methods
We performed a crossover, randomised, double-blind,
placebo-controlled trial. The study was approved by the
ethics committee of the Vale do Paraíba University
(protocol number H260/CEP/2006 and H262/CEP/2006).
All subjects or one their parents signed written informed
consents before their participation in the experiment. The
volunteers were recruited among professional male volleyball players (n=9) and young male soccer players (n=11)
Lasers Med Sci
from Rio Grande do Sul State (Brazil) at the same sporting
level (highest national level), and they were scheduled to
receive either active LLLT or placebo LLLT before an
exercise session.
Randomisation procedure
Randomisation was performed by a simple drawing of lots
(A or B), which determined if participants should receive
active LLLT or placebo LLLT in the first session. The
randomisation procedure was administered by an assistant
not involved in the experiment. The allocation code was
then delivered to a technician who preset the laser control
unit to active or placebo LLLT mode. He then delivered the
preset laser unit to the therapist. The technician was
instructed not to communicate the type of treatment given
to either the patients or the therapist, or to the observers.
Thus, the allocation to treatments was concealed from
participants, therapist and observers.
Blinding procedure
Careful attention was paid to the blinding procedure, which
was composed of several measures to ensure complete
blinding. The infrared wavelength (830 nm) is invisible to
the human eye. The laser was only activated after the laser
probe had been placed on the skin, and the laser probe was
not removed before the irradiation was over and the laser
probe deactivated. This procedure hid sight of the laser
beam from both the therapist and the participants. To ensure
blinding further, both therapist and participants used dark
laser goggles for eye protection. Observers and analysts
were also blinded to the type of treatment given.
All athletes performed the same exercise test, but for the
volleyball athletes we analysed the creatine kinase levels
and for the soccer athletes we analysed the levels and
removal of blood lactate.
Exclusion criteria for both
1. Any previous musculoskeletal injury to the hip, knee or
ankle regions
2. Participation in fewer than 80% of the regularly
scheduled physical training and soccer sessions for
the soccer team or volleyball sessions for the volleyball
team
3. Players using any kind of nutritional supplements or
pharmacological agents
Test procedures
Period of evaluation We took care to obtain standardisation
in the execution of the exercise protocols. The subjects
performed the exercises in a standard sitting position at
approximately the same time of the day (to control for the
circadian rhythm). The exercises were performed and
evaluated in two sessions (day 1 and day 8) on the same
day of the week (Monday) during the same period of the
day (between 08:30 a.m. and 11:30 a.m.). Any hard
physical activity was not permitted during the weekend
before testing. The timeline of the experiment is shown in
Fig. 1.
Fatigue test protocol At the first session (day 1) and second
session (day 8) of the study, basal blood measurements
(creatine kinase or lactate) were obtained for each subject.
Immediately after this the test observer instructed the
athletes and supervised their conduct in a series of
muscle-stretching exercises. Stretching exercises involved
all the major muscles of the lower extremities (one round of
60 s for each muscle group).Then, the observer seated each
subject on the ergometer cycle and fixed their feet to the
pedals. Instructions for the Wingate test were then delivered
to the athletes. For each athlete, the test consisted of cycling
at maximum speed for 30 s against a load of 7.5% of the
athlete’s body weight.
Inclusion criteria for volleyball players
1. Male volleyball players
2. Having played volleyball at a professional level for at
least 2 years
3. Aged between 18 and 36 years
Inclusion criteria for soccer players
1. Male soccer players
2. Having played soccer for at least 4 years and with at
least 5 days of training per week
3. Aged between 15 and 18 years
Protocol for low-level laser therapy
At both sessions (day 1 and day 8), the participants were
given either a single treatment of active LLLT or a placebo
LLLT (both with 830 nm Thera Lase; DMC® São Carlos,
SP, Brazil), according to the result of the randomisation
procedure. Active LLLT or placebo LLLT was administered
after the stretching regimen but immediately before the
exercise fatigue test. Active LLLT and placebo LLLT were
administered by a therapist (M.R.). The laser was not
turned on until the tip of the laser probe had been put into
contact with the skin over the rectus femoris muscle. The
Lasers Med Sci
Fig. 1 Time flow chart of the
study
belly of the rectus femoris muscle was divided into five
irradiation points evenly distributed along the ventral
middle line of the muscle belly so that we could deliver
LLLT to most of the muscle belly. The laser irradiation was
performed bilaterally, and thus ten points in total were
irradiated (Fig. 2).
The laser irradiation was performed in contact mode,
with the laser probe held stationary under slight pressure at
a 90° angle to the skin surface. The laser unit incorporated a
timer, which automatically shut off the laser beam while
giving a sound signal when the preset irradiation time had
been finished. The laser probe was not removed from skin
contact until the timer had shut off the laser. All subjects
received active LLLT and placebo LLLT 1 week apart and
immediately before undergoing the Wingate tests. Because
the soccer athletes at hand were adolescents and performed
less work in the Wingate test, we decided to use lower
LLLT doses for these athletes. The laser parameters are
summarised in Table 1.
After active LLLT or placebo LLLT had been administered, the participants were immediately repositioned, and
they started the fatigue exercise protocol within an interval
of 180 s.
Blood samples and creatine kinase analysis (volleyball
athletes)
In order to measure blood CK, we took blood samples after
aseptic cleaning of the ventral side of the dominant arm.
The procedure was performed by a qualified nurse
(unaware of the group allocation), who took one sample
before the exercises were started and another blood sample
3 min after the exercises had been completed. The blood
analysis was performed by infrared spectrophotometry.
Blood samples and lactate concentration (soccer athletes)
In order to measure blood lactate concentrations, we took
blood samples after aseptic cleaning of the second finger of
the dominant arm. The procedure was performed by a
qualified nurse (unaware of the group allocation), who took
one sample before the exercises were started and another
blood sample 3 min, 10 min and 15 min after the exercises
had been completed. Accu-Chek Soft Clix® lancets were
used, and the samples were immediately analysed with the
portable Accutrend Lactate® analyser.
Statistical analysis
Fig. 2 Laser irradiation points (white circles) used for active LLLT or
placebo LLLT
Group means and their respective standard deviations were
used for statistical analysis. We used a two-sided paired ttest to test if there was a significant difference in the muscle
Lasers Med Sci
Table 1 Laser parameters
Laser parameters
Wavelength: 830 nm (infrared)
Frequency: continuous output
Optical output: 100 mW
Spot diameter: 0.0006 cm
Spot size: 0.0028 cm2
Power density: 35.71 W/cm2
Energy: 4 J at each point (volleyball players), 3 J at each point
(soccer players)
Energy density: 1,428.57 J/cm2 at each point (volleyball players),
1,071.43 J/cm2 at each point (soccer players)
Treatment time: 40 s at each point (volleyball players), 30 s
(soccer players)
Number of points: 10
Total energy delivered: 40 J (volleyball players), 30 J
(soccer players)
Application mode: probe held stationary in skin contact with a 90°
angle and slight pressure
work during the Wingate test and change in CK levels
between the group undergoing active LLLT and those
receiving placebo LLLT, and we used analysis of variance
(ANOVA) with a Student–Newman–Keuls post-test to test
if there was a significant difference in the change in blood
lactate levels between the group subjected to active LLLT
and those undergoing placebo LLLT. The significance level
was set at P<0.05.
Results
There were nine healthy male professional volleyball
players recruited who met the inclusion criteria. Their
average age was 20.67 (± 2.96) years, their weight was a
mean 91.67 kg (± 7.84 kg), and their height was 195.33 cm
(± 6.28 cm).
There were 11 healthy young male soccer players
recruited who met the inclusion criteria. Their average age
was 16.18 (± 0.75) years, their weight was a mean 66.82 kg
(± 6.68 kg), and their height was 175.82 cm (± 5.83 cm).
The Wingate test (undertaken immediately after active
LLLT or placebo LLLT) revealed a non-significant difference in muscle work between the active LLLT group
(21,888.31 J ± 2,062.98 J) and the placebo LLLT group
(22,429.79 J ± 2,842.71 J), P=0.3583, for volleyball
players, and 16,214.97 J (± 1,639.88 J) for the active
LLLT group and 16,289.21 J (± 1,700.34 J) for the placebo
LLLT group (P=0.8681) for soccer players. The results are
summarised in Fig. 3.
Fig. 3 Muscle work performed by volleyball athletes and soccer
athletes during the Wingate test
Before both treatments the volleyball players showed
similar creatine kinase levels at the pre-exercise test; before
the active LLLT the athletes had a mean level of
108.64 U l−1 (± 33.68 U l−1) and before the placebo LLLT
the athletes had a mean level of 107.72 U l−1 (±
41.12 U l−1) (P=0.7737).
The results of the creatine kinase tests after the exercises
showed that the active LLLT treatment promoted a lower
change (2.52 U l−1 ± 7.04 U l−1) in the muscle damage than
the did the placebo LLLT (28.49 U l−1 ± 22.62 U l−1) (P=
0.0133). The results are summarised in Fig. 4.
For both treatments the soccer players presented similar
blood lactate levels at the pre-exercise tests, with a mean of
2.52 mmol. l−1 (± 0.52 mmol l−1) for active LLLT and
2.24 mmol l−1 (± 0.33 mmol l−1) for placebo LLLT, with no
statistical difference (P>0.05).
The results of blood lactate tests showed that both
treatments increased the blood lactate levels from baseline
assessments to post-exercise assessments. There were,
however, no significant differences between the two treatments in the change in lactate levels 3 min after exercise
(active LLLT 10.75 mmol l−1 ± 2.11 mmol l−1; placebo
Fig. 4 Creatine kinase levels
Lasers Med Sci
Fig. 5 Blood lactate levels (# P<0.01 between laser and placebo
15 min after exercise)
LLLT 11.42 mmol l−1 ± 2.89 mmol l−1; P>0.05) and
10 min after exercise (active LLLT 10.63 mmol l−1 ± 2.17;
placebo LLLT 11.04 mmol. l−1 ± 1.42 mmol l−1; P>0.05).
However, 15 min after exercise, the active LLLT group
with a mean of 8.55 mmol l−1 (± 2.14 mmol l−1) presented a
lower significant value than did the placebo LLLT group
with a mean of 10.52 mmol l−1 (± 1.82 mmol l−1) with P<
0.01. The results are summarised in Fig. 5.
Discussion
In this clinical trial we evaluated the effect of LLLT, applied
before high-intensity exercises, on the production and
removal of blood lactate and on muscle damage in athletes.
In a previous study using a rat model, Lopes-Martins et al.
[30] found that LLLT seemed to attenuate skeletal muscle
fatigue and reduced the muscle damage caused by tetanic
contractions induced by electrical stimulation. Our previous
studies demonstrated that LLLT at 655 nm [34] and 830 nm
[35] wavelengths can delay skeletal muscle fatigue in
humans, with increased voluntary muscle contractions
without increased blood lactate levels when compared with
placebo LLLT treatment.
In the study described now we used the Wingate test to
increase the blood lactate levels and induce muscle damage,
to verify the effect of LLLT application before highintensity exercises in preventing muscles disorders. The
reason we used different blood analyses for the two types of
athletes (volleyball players and soccer players) was because
we had suffered some problems during data acquisition,
and it was a limitation of our research. Therefore, in further
studies, we recommend that both analyses should be
performed for all subjects.
Our results demonstrated that LLLT applied before
exercise was able to reduce muscle damage and increase
the removal of blood lactate. The decrease observed in the
levels of CK and blood lactate under active LLLT compared
with placebo LLLT could be related to the ability of LLLT
to prevent muscle ischaemia by reducing both the release of
reactive oxygen species (ROS) and the activity of creatine
phosphokinase, while levels of antioxidants and heat shock
proteins increase [32–33]. In a recent study [36], LLLT
improved mitochondrial function in muscle cells at doses of
0.33–8.22 J/cm2, and LLLT doses of 0.33 J/cm2 and
1.338 J/cm2 reversed the dysfunctional state induced by
electrical stimulation. This effect could, in turn, possibly
contribute to the observed decrease in CK levels in our
study. The LLLT increase the microcirculation, and it
could be the responsible to increase the blood lactate
removal [37].
The majority of therapeutic modalities are applied after
the exercises; however, in this study, we aimed to evaluate
also the effect of a novel therapeutic modality on previous
sports recovery exercises to prevent injuries and increase
muscle recovery after high-intensity exercises. These findings could help the physiotherapist to increase athlete’s
recovery between exercise sessions, reducing the injuries,
mainly muscle injuries, and, consequently, increasing the
athlete’s performance.
The clinical impact of our findings is limited by the fact
that the observed effects were measured within a few
minutes after irradiation (300–400 s of LLLT, 180 s for
repositioning, and 30 s for exercise fatigue testing). Other
factors were the very small spot size of the infrared laser
(0.0028 cm2) and the small area irradiated by five points
(bilaterally) in this clinical trial. Possibly, with a large area
of irradiated muscle, the results might have been
increased. These issues illustrate the difficult transition
of positive findings in animal studies to a clinically
relevant treatment.
Further studies need to be performed to evaluate the
optimal doses of LLLT in this novel area of research,
evaluating different biochemical parameters and irradiating
different muscle areas.
Conclusion
We conclude that LLLT applied before high-intensity
exercises can increase the removal of blood lactate and
can reduce muscle damage, providing athletes with fast
muscle recovery between exercises sessions. These findings
may indicate that LLLT before exercise can protect muscles
against minor damage and inflammatory reactions after
heavy exercise. Further research is necessary to define the
optimal laser parameters for this use.
Lasers Med Sci
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