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Effects of low-level laser therapy (808 nm) on isokinetic muscle performance of young women submitted to endurance training: A randomized controlled clinical trial

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Low-level laser therapy (LLLT) has shown efficacy in muscle bioenergetic activation and its effects could influence the mechanical performance of this tissue during physical exercise. This study tested whether endurance training associated with LLLT could increase human muscle performance in isokinetic dynamometry when compared to the same training without LLLT. The primary objective was to determine the fatigue index of the knee extensor muscles (FIext) and the secondary objective was to determine the total work of the knee extensor muscles (TWext). Included in the study were 45 clinically healthy women (21 ± 1.78 years old) who were randomly distributed into three groups: CG (control group), TG (training group) and TLG (training with LLLT group). The training for the TG and TLG groups involved cycle ergometer exercise with load applied to the ventilatory threshold (VT) for 9 consecutive weeks. Immediately after each training session, LLLT was applied to the femoral quadriceps muscle of both lower limbs of the TLG subjects using an infrared laser device (808 nm) with six 60-mW diodes with an energy of 0.6 J per diode and a total energy applied to each limb of 18 J. VT was determined by ergospirometry during an incremental exercise test and muscle performance was evaluated using an isokinetic dynamometer at 240°/s. Only the TLG showed a decrease in FIext in the nondominant lower limb (P = 0.016) and the dominant lower limb (P = 0.006). Both the TLG and the TG showed an increase in TWext in the nondominant lower limb (P < 0.001 and P = 0.011, respectively) and in the dominant lower limb (P < 0.000 and P < 0.000, respectively). The CG showed no reduction in FIext or TWext in either lower limb. The results suggest that an endurance training program combined with LLLT leads to a greater reduction in fatigue than an endurance training program without LLLT. This is relevant to everyone involved in sport and rehabilitation.
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ORIGINAL ARTICLE
Effects of low-level laser therapy (808 nm) on isokinetic
muscle performance of young women submitted
to endurance training: a randomized controlled clinical trial
Wouber Hérickson de Brito Vieira &Cleber Ferraresi &
Sérgio Eduardo de Andrade Perez &Vilmar Baldissera &
Nivaldo Antônio Parizotto
Received: 12 April 2011 / Accepted: 3 August 2011
#Springer-Verlag London Ltd 2011
Abstract Low-level laser therapy (LLLT) has shown
efficacy in muscle bioenergetic activation and its effects
could influence the mechanical performance of this tissue
during physical exercise. This study tested whether endur-
ance training associated with LLLT could increase human
muscle performance in isokinetic dynamometry when
compared to the same training without LLLT. The primary
objective was to determine the fatigue index of the knee
extensor muscles (FIext) and the secondary objective was
to determine the total work of the knee extensor muscles
(TWext). Included in the study were 45 clinically healthy
women (21±1.78 years old) who were randomly distributed
into three groups: CG (control group), TG (training group)
and TLG (training with LLLT group). The training for the
TG and TLG groups involved cycle ergometer exercise
with load applied to the ventilatory threshold (VT) for 9
consecutive weeks. Immediately after each training session,
LLLT was applied to the femoral quadriceps muscle of both
lower limbs of the TLG subjects using an infrared laser
device (808 nm) with six 60-mW diodes with an energy of
0.6 J per diode and a total energy applied to each limb of
18 J. VT was determined by ergospirometry during an
incremental exercise test and muscle performance was
evaluated using an isokinetic dynamometer at 240°/s. Only
the TLG showed a decrease in FIext in the nondominant lower
limb (P=0.016) and the dominant lower limb (P=0.006).
Both the TLG and the TG showed an increase in TWext in
the nondominant lower limb (P<0.001 and P=0.011,
respectively) and in the dominant lower limb (P<0.000 and
P<0.000, respectively). The CG showed no reduction in
FIext or TWext in either lower limb. The results suggest that
an endurance training program combined with LLLT leads to
a greater reduction in fatigue than an endurance training
program without LLLT. This is relevant to everyone involved
in sport and rehabilitation.
Keywords Low-level laser therapy (LLLT) .Endurance
training .Fatigue index .Isokinetic dynamometer
Introduction
The radiation from low-level laser therapy (LLLT) interacts
with biological tissues triggering several physiological and/
or therapeutics effects [1,2], and LLLT has been shown to
enhance muscle performance in animal experiments [36],
in strength training in humans [7] and in maximum tests of
effort in isokinetic dynamometry also in humans [7,8].
LLLT seems to act on cellular energy metabolism, stimulat-
ing photochemical and photophysical events in the mito-
chondria [2,9,10]. It also promotes structural and
metabolic changes in the organelles of different cells and/
or tissues [9,11] that may be involved in the membrane
W. H. de Brito Vieira (*)
Department of Physical Therapy, Federal University of Rio
Grande do Norte (Campus Universitário Lagoa Nova),
Av. Senador Salgado Filho, 3000,
59072-970 Natal, RN, Brazil
e-mail: hericksonfisio@yahoo.com.br
C. Ferraresi :N. A. Parizotto
Department of Physical Therapy, Laboratory of
Eletrothermophototherapy, Federal University of São Carlos,
Rodovia Washington Luís, km 235,
13565-905 São Carlos, SP, Brazil
S. E. de Andrade Perez :V. Baldissera
Department of Physiological Sciences, Laboratory of Physiology
of Exercise, Federal University of São Carlos,
Rodovia Washington Luís, km 235,
13565-905 São Carlos, SP, Brazil
Lasers Med Sci
DOI 10.1007/s10103-011-0984-0
potential [12] and enzymatic activity [11,13]. The
structural changes in mitochondria promoted by LLLT
include the formation of giant mitochondria through the
merging of membranes of smaller and neighboring mito-
chondria [14]. This structural adaptation (larger mitochon-
dria) possibly results in the ability to provide higher levels
of respiration and energy (ATP) to cells, characteristic of a
metabolic adaptation (higher enzymatic machinery) [14].
Endurance training is a kind of training that can possibly
be modulated by LLLT. This training leads to an increase in
aerobic capacity [15,16] and stimulates type I muscle fibers
(oxidative) or type II fibers (oxidative and glycolytic) to
develop more mitochondria for metabolizing energy sub-
strates through oxidative phosphorylation [17,18]. The
highest aerobic capacity acquired from endurance training
can be assessed and/or monitored by an incremental and
dynamic physical test of effort on a cycle ergometer [19].
This evaluation utilizes a gas analyzer to measuring
inspired and expired gases during exercise and identifies,
for example, the ventilatory threshold (VT, the point that
indicates an exponential increase in ventilation to counter
the metabolic acidosis that occurs as a result of the
accumulation of H
+
ions from anaerobic glycolysis, which
supplements aerobic ATP production in high-intensity
exercise) [19]. Furthermore, endurance training increases
the expression of mitochondrial genes that are associated
with structural (number of mitochondria) and metabolic
adjustments (higher enzymatic machinery), which favors
aerobic metabolism and muscular endurance, i.e. fatigue
reduction during exercise [17,18].
Muscle fatigue promoted by repeated muscle contractions
is associated with the accumulation of inorganic phosphate,
ADP, magnesium ions, hydrogen ions and reactive oxygen
species in the muscle cells. In addition, muscle fatigue also
decreases sources of ATP such as muscle glycogen and
phosphocreatine [20]. Thus, muscle performance quantifica-
tion (torque, number of muscle contractions and fatigue) can
demonstrate indirectly the adaptation of skeletal muscle to
metabolic stress from exercise and can also identify muscle
responses to exercise with phototherapy stimulation [3,4,7,
8,21]. Isokinetic dynamometry has been used to evaluate
muscle performance in subjects submitted to phototherapy
before or after intense exercise [7,8,21]. The isokinetic
dynamometer is considered gold-standard equipment to
measure muscle performance and consequently muscle
fatigue, because the angular velocity (or the muscle-
shortening velocity) is always controlled (isokinetic) during
articular movement [21,22]. Thus, the forcevelocity
relationship does not affect muscle torque or work produc-
tion or the muscle fatigue index [21].
The purpose of this study was to determine if a chronic
endurance training program with LLLT would enhance the
effects of chronic endurance training without LLLT. The
considered hypothesis was that a program of chronic
endurance training with LLLT could promote a greater
increase in muscle performance than endurance training only.
The study was a randomized controlled clinical trial to
determine the fatigue index (primary objective) and the total
work (secondary objective) of the knee extensor muscles
(FIext and TWext, respectively) by isokinetic dynamometry.
Methods
The study was designed as a randomized controlled clinical
trial. All procedures were approved by the Ethics in Human
Research Committee of the Federal University of São
Carlos and the study was registered with NIH Clinical
Trials (NCT01391195). The subjects were recruited from
among graduate students at the Federal University of São
Carlos. All subjects were informed about purposes proce-
dures of the study and signed a consent form.
Subjects
The subjects were 45 female students who reported being
clinically healthy.
Inclusion criteria
The inclusion criteria were: healthy female aged between
18 and 28 years with a body mass index between 18 and 25
kg/m
2
, and with a beginner or moderately trained pattern of
physical activity, i.e. performed some physical activity with
a noncompetitive aim one to three times a week, as
described previously [23].
Exclusion criteria
The exclusion criteria were: previous injury to the femoral
quadriceps or hamstring muscles (within 6 months prior to
the study), osseous or articular disorder of the lower limbs,
cardiovascular system disorder or systemic disease such as
those in a previous study [7].
Randomization
Randomization was performed by a simple drawing
procedure and the subjects were distributed equally into
three groups: training with LLLT group (TLG), training
alone group (TG) and control group (CG).
Study groups
TG and TLG subjects were submitted to a program of
chronic endurance training involving cycle ergometer
Lasers Med Sci
exercise three times a week for 9 consecutive weeks. Soon
after the end of each training session, the TLG subjects
underwent LLLT to both femoral quadriceps muscles. CG
subjects did not carry out any form of intervention and did
not receive any treatment. Thus, this group was evaluated
only at the beginning and at the end of the study.
Instruments
The following instruments were used: a computerized
isokinetic dynamometer (Multi-Joint System 3; Biodex,
New York, NY) to record the isokinetic variables of muscle
performance (FIext and TWext); a gas analyzer (VO2000;
MedGraphics, St. Paul, MN USA) for determination of VT
and an electromagnetic brake cycle ergometer (Ergo Cycle
167; Ergo-FIT, Pirmasens, Germany).
Procedures
The subjects were submitted to physiotherapeutic, nutri-
tional and medical evaluations during the morning in order
to ensure acceptable clinical and procedural conditions for
participation in the study. Next, a dynamic and incremental
test was performed on the cycle ergometer with respiratory
gas uptake (cardiopulmonary exercise test) to determine the
VT, which was used as the training load. This assessment
was repeated every 3 weeks to adjust the training load. In
the afternoon of the same day, the subjectsmuscle
performance was evaluated by isokinetic dynamometry in
which FIext and TWext values were determined. All
subjects were instructed to keep to their normal physical
routine and eating habits during the study, to sleep for about
8 h per night, and not to consume alcohol or drugs.
Assessment protocols
All protocols for muscle performance assessment and
workload adjustment were performed by the same evalu-
ator. It is important to note that the assessments at baseline
and after 9 weeks were conducted on different training
days.
Protocol I (isokinetic dynamometry) A brief 5-min warm-
up was carried out on a cycle ergometer with a load of
50 W and a speed in the range 6070 rpm. Next, the
subjects were positioned on the isokinetic dynamometer
which had been previously calibrated. The subjects stood
properly aligned and stabilized with straps in order to avoid
possible compensatory movements in accordance with the
guidelines for the device. Both lower limbs were evaluated
in a random order for each subject. The dynamometer
rotation axis was adjusted to the knee axis of the subject at
the lateral epicondyle of the femur. The hip was stabilized
at 80° and the lever arm of the equipment was set
approximately 1 cm above the tibial malleolus. Parameters
such as chair height, back-rest distance, seat angle and
dynamometer base were adjusted for each subject (Fig. 1a).
Before starting the recording of isokinetic muscle
performance, there was a familiarization period with the
apparatus that consisted of three submaximal voluntary
concentric muscle contractions in the full range of
standardized and preprogrammed motion (9015º), with a
constant angular velocity at 240º/s. After a 3-min rest, the
test began with one set of 60 concentric and reciprocal
quadriceps and hamstring contractions in all ranges of
standardized and preprogrammed knee motion in flexion
and extension. The subjects were encouraged verbally and
visually to achieve maximum effort. FIext was calculated
as: 100 [(work last third/work first third) × 100]. TWext
was calculated as the graphical area of all repetitions (torque
curve versus displacement) of the test in accordance with the
guidelines of the equipment manufacturer (BIODEX).
Protocol II (incremental and dynamic test of effort on the
cycle ergometer) The subjects remained for 2 min at rest on
the cycle ergometer to capture baseline values of the
inspired and expired gases (Fig. 1b). The protocol was
then started with load (power) of 25 W and a load increment
of 25 W every 2 min of activity (Balkes protocol). The test
was always taken to the maximum (until volitional
exhaustion) or until the appearance of signs and limiting
symptoms, such as dyspnea, limiting pain in the legs or
chest pain. The volunteers were instructed to keep the speed
always around 6070 rpm. VT was determined by an
experienced examiner through visual inspection of ventila-
tion curves, oxygen equivalent and/or expired fraction of
oxygen. For each block of effort, the volunteer pointed to
their perceived level of subjective effort on the Borg scale
(620 points) [24]. The heart rate of the subjects, room
temperature (2225°C) and relative humidity (4060%)
were also monitored.
Protocol III (training on the cycle ergometer) The TG and
TLG training was always conducted in the afternoon three
times a week for 9 consecutive weeks, with an effort load
corresponding to VT obtained in protocol II. The volunteers
were instructed to keep their speed around 6070 rpm
during the training sessions. Each training session started
with 5 min of warm-up and ended with 5 min of cooling,
both with a load below the VT. The training sessions lasted
for 40 min in the 1st, 4th and 7th week, 50 min in the 2nd,
5th and 8th week, and 60 min in the 3rd, 6th and 9th week.
The loads were increased at the end of the 3rd and 6th
weeks of training in accordance with the VT obtained in a
new incremental effort test (protocol II). Each training
session was supervised by an instructor and all parameters
Lasers Med Sci
followed all the recommendations of the American College
of Sports Medicine [15].
Protocol IV (LLLT application) TLG subjects underwent
LLLT immediately after each training session while the
physiological stress and the consequent metabolic changes
were still present, since the efficacy of LLLT is known to be
increased under these conditions [25]. Using a contact
technique, the infrared laser beam was kept stationary and
perpendicular to the skin during 27 sessions in five different
areas distributed uniformly over the belly of the femoral
quadriceps muscle of each lower limb [26] giving in total 30
irradiated points per session (Fig. 1c). A near-infrared Ga-Al-
As laser (808 nm) with six obliquely arranged diodes
was used operating in continuous mode. The equipment
and LLLT parameters used were as follows: six diodes of
60 mW radiant power each; 10 s application time in each area;
0.6 J radiant energy per point (diode); 0.0028 cm
2
beam area;
214.28 J/cm
2
diode energy density or fluency; and 21.42 W/
cm
2
diode power density or irradiance. Thus, the total
application time for each lower limb was 50 s per session
(for a total of 100 s for the two limbs), the total energy
applied to each lower limb per session was 18 J (for a total of
36 J for the two limbs), and there were 30 application points
(for a total of 60 points for the two limbs).
Statistical analysis
The normality of the data distribution was analyzed using
the Shapiro-Wilk test and the homogeneity of variances
using Levenes test. The effect of training on muscle
performance in isokinetic dynamometry was evaluated by
two-way analysis of variance with repeated measures only
on one factor. The independent factors were group (with
three levels: TLG, TG and CG) and time (with two levels:
baseline and after 12 weeks), which was also considered as
a repeated measurement. When significant differences were
found, Tukeys post-hoc test was applied. Significance was
set at P<0.05.
Results
Table 1shows the demographic data of all the groups.
The TLG was the only group that showed a decrease in
FIext (the primary objective) for the nondominant (P=0.016)
and the dominant lower limb (P=0.006) after training. The
TG showed a decrease in FIext in both lower limbs (but
without statistical significance, P>0.05), and the CG showed
no change in FIext from the baseline values. Among the
groups no statistical differences were observed (P>0.05).
The detailed FIext results for both lower limbs of all groups
(CG, TG and TLG) are presented in Tables 2and 3,and
these results are presented graphically in Fig. 2.
The TG and TLG showed an increase in TWext (the
secondary objective) for the nondominant lower limb
(P=0.011 and P< 0.001, respectively) and for the domi-
nant lower limb (P<0.001 and P< 0.001, respectively)
after training. However, there were no significant differ-
ences between the groups (P>0.05). The detailed TWext
results for both lower limbs of all groups (CG, TG and
Fig. 1 Subject positioning for
the isokinetic dynamometry test
(a) and the ergospirometry test
(b). Application points for LLLT
on the knee extensor muscles (c)
Table 1 Anthropometric
characteristics of the three study
groups before and after
endurance training. Values are
means and standard deviations
Variable CG TG TLG
Before After Before After Before After
Age (years) 21.2± 2.1 20.5± 1.3 21.2 ± 1.7
Height (m) 1.63± 0.04 1.60± 0.04 1.64 ± 0.05
Body mass (kg) 54.5±5.2 55.3± 5.3 56.3± 6.2 57.1 ± 6.7 55.1± 6.8 55.7±6.5
BMI (kg/m
2
) 20.5± 1.8 20.8 ± 1.7 21.8± 2.1 22.2±2.3 20.6±1.8 20.7± 1.7
Lasers Med Sci
TLG) are presented in Tables 2and 3, and these results
are presented graphically in Fig. 3.
Discussion
With regard to the primary objective, the TLG was the only
group that showed a decrease in FIext after training, demon-
strating a beneficial effect of LLLTon muscle performance. The
TG also showed a decrease FIext but without statistical
significance, and the CG showed no change in FIext from the
baseline values (Fig. 2).TheFIexthasbeenusedtoassessthe
muscle endurance of subjects under fatigue protocols after
phototherapy [21], and this index, obtained by isokinetic
dynamometry, is a reliable measure of muscle response in the
evaluation of physical exercise to exhaustion [27]. With regard
to previous studies in which FIext was determined, some did
not evaluate fatigue reduction [21,28], while others corrob-
orate the results of this study in showing that LLLT promotes
a reduction in human muscle fatigue by increasing the number
of maximal voluntary contractions [29,30]. The total energy
used in previous studies that found significant differences
were 20 J for each member irradiated, similar to that found in
the present study (18 J). Furthermore, the muscle groups
irradiated were different (biceps brachial versus femoral
quadriceps) as well as the fluency (500 J/cm
2
and 1,785 J/
cm
2
versus 214.28 J/cm
2
) and the number of points irradiated
per limb (4 points versus 30 points). Compared with a more
recent study that also found better muscle performance of
subjects following LLLT [7], the parameters used were very
similar: irradiated limb, distribution of application points,
fluency, power density and total energy per member during
1weekoftraining(50.4Jversus54J).
With regard to the secondary objective, the TG and TLG
showed a significant increase in TWext after training (9 weeks),
but no differences were observed between the groups (Fig. 3).
These results demonstrate that the training was effective in
increasing the energy expended by subjects submitted to
endurance training during the fatigue test. TWext represents
the amount of energy (in Joules) that the knee extensor
muscles are able to produce during muscle contractions
(repetitions) in the performance test [27]. This energy is
calculated in terms of the graphical area of torque curves
versus displacement [27]. If the torque curves and time of
muscle contraction (displacement) are smaller, the total work
will also be lower [27]. Thus, the analysis of TWext associated
with FIext determines how torque curves versus displacement
ranged during fatigue testing and consequently it quantifies
decreases in torque production [27]. The present results do not
agree with those reported by Baroni et al. [21] who similarly
evaluated TWext and the FIext and found no improvement in
TWext or FIext in irradiated subjects. One possible reason is
related to the number of photostimulation application points
on the femoral quadriceps (3 points versus 30) and the
number of application sessions (1 versus 27 days).
After comparing the results found in this study with the
results already reported in the scientific literature, there
remains a gap in our understanding as to how LLLT can
improve muscle performance. This study was not designed to
identify the biochemical (energy metabolism) and genetic
(gene expression) effects of laser irradiation on skeletal muscle,
but to raise hypotheses that might elucidate these effects:
Table 2 FIext and TWext for the nondominant lower limbs. Values are means and standard deviations
Variable CG TG TLG
Before After PBefore After PBefore After P
FIext 65.1± 4.4 64.2 ± 5.5 0.992 66.5 ±4.5 62.9±5.9 0.201 63.8± 9.2 58.3 ± 7.6 0.016*
TWext 2,309.8± 255.6 2,403.4 ± 205.6 0.568 2,435.8±379.6 2,636.6 ± 477.2 0.011* 2,340.1± 484.2 2,644.3 ±473.2 <0.001*
*P<0.05, before vs after endurance training.
Table 3 FIext and TWext for the dominant lower limbs. Values are means and standard deviations
Variable CG TG TLG
Before After PBefore After PBefore After P
FIext 64.8±4.2 63.3± 2.9 0.760 64.5± 5.8 61.7±3.1 0.173 62.1 ± 6.8 57.7 ±5.4 0.006*
TWext 2,350.5 ± 316.3 2,417.4 ±230.5 0.798 2,501.3±433.6 2,813.0 ± 435.5 <0.001* 2,373.1 ±409.8 2,682.5± 490,2 <0.001*
*P<0.05, before vs after endurance training.
Lasers Med Sci
First hypothesis Structural changes in mitochondria of
tissues under laser therapy have been
reported, mainly involving the formation
of giant mitochondria through the merg-
ing of the membranes of smaller and
neighboring mitochondria [14]. These
organelles have receptors for laser pho-
tons such as the enzyme cytochrome c
oxidase [2,10,11,13]. The enzyme
cytochrome coxidase is a mitochondrial
enzyme responsible for the transfer of
electrons from complex III to complex
IVof the electron transport chain, direct-
ly involved in ATP synthesis (ATP) [13].
Thus, LLLT can increase muscle ATP
synthesis both by increasing the amount
of cytochrome coxidase and its activity
[13] or by increasing the activity of the
four complexes of the mitochondrial
electron transport chain, featuring a
metabolic adaptation (more ATP) for
cellular activity [11].
Second hypothesis The alactic anaerobic metabolism (phos-
phocreatine) provides ATP to skeletal
muscle during the first seconds of high-
intensity physical activity. This mecha-
nism requires resynthesis of creatine to
phosphocreatine to continue to supply
AT P d u r i n g e x e r c i s e [ 16]. This ATP
synthesis depends on ATP produced
aerobically by mitochondria via a mech-
anism called the mitochondrial creatine
shuttle, described by Tonkonogi and
Sahlin [16] and recently studied by
Ferraresi et al. [7]. Thus, the better
fatigue resistance of the TLG group in
the fatigue test may have been related
to higher amounts of alactic energy
(phosphocreatine), which may have
been a result of training and laser
photostimulation.
Third hypothesis Muscle fatigue has been related to accu-
mulation of hydrogen ions inferred from
lactate levels in the blood [31] and with
subjectively perceived increases in effort
[32]. Accordingly, Brooks et al. [31]and
Hashimoto et al. [33] have described a
mechanism for conversion of pyruvate to
lactate in the intermembrane space and in
the mitochondrial matrix of muscle cells,
contributing to lower lactate accumula-
tion and increased energy availability
during exercise, as discussed by Ferraresi
et al. [7].
Fig. 2 FIext for both lower
limbs. *P<0.05, before vs after
endurance training (TLG
dominant limb P=0.006, TLG
nondominant limb P=0.016)
Fig. 3 TWext for both lower
limbs. *P<0.05, before vs after
endurance training (TG and
TLG dominant limb P<0.001,
TG nondominant limb P=0.011,
TLG nondominant limb
P<0.001)
Lasers Med Sci
Fourth hypothesis In the TLG subjects the concentra-
tion of the cytosolic enzyme lactate
dehydrogenase (LDH) probably de-
creased [8], specifically the LDHA4
isoform which is considered a pyru-
vate reductase and has a greater
abilitytotransformpyruvicacidinto
lactic acid [34]. Thus, a lower con-
centration of LDHA4 leads to lower
levels of lactic acid production and
possibly decreases or delays the onset
of fatigue [31,32,35].
Fifth hypothesis Perhaps TLG subjects had an increase in
the expression of mitochondrial genes,
such as PPARCG-1α(peroxisome
proliferator-activated receptor gamma,
coactivator 1 alpha), or NRF-1 and NRF-
2 (nuclear respiratory factory 1 and 2)
during and after training followed by
LLLT [7]. In addition, other genes in-
volved in energy metabolism, such as
LDHC (encoding the LDH cytosolic
enzyme) or COX (encodes the cyto-
chrome coxidase enzyme) were possibly
modulated by training followed by LLLT.
The study had some limitations. TG subjects did not
receive a placebo laser treatment as performed in previous
studies [8,21,29,30], blood chemistry was not assessed
(immunological and inflammatory responses), and myo-
genic enzyme (creatine kinase) and metabolic enzymes
(such as LDH) were not assessed before and after exercise
training [8,29,30]. Another limitation is that possible
increases in body temperature, mainly of the femoral
quadriceps and the whole lower limb, following laser
therapy were not assessed although TLG subjects did not
report any warming.
Conclusion
The study results suggest that endurance training combined
with LLLT might be superior to endurance training only. We
emphasize that care is needed in generalizing the results.
Further studies, investigating in particular LLLT, myogenic
enzymes, blood chemistry and gene expression, are
necessary to elucidate the interaction between laser radia-
tion and metabolic and molecular mechanisms of recovery
and muscle performance.
Acknowledgments The authors would like to thank the Department of
Physical Therapy and the Department of Physiological Sciences of the
Federal University of São Carlos for assistance with this study, the
research volunteers, the Conselho Nacional de Desenvolvimento
Científico e Tecnológico (CNPq) for partial funding of the research, and
the DMC Equipamentos for manufacturing and lending the laser device.
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Lasers Med Sci
... Studies have demonstrated that these biochemical reactions can improve muscle functioning and delay the fatigue process [8][9][10][11][12][13][14][15][16] . However, today the big question that is asked about LLLT is no longer about its effectiveness in slowing down the FM process and increasing performance, but rather, what are the application parameters that can optimize these effects? ...
... The sample size was calculated considering α = 0.05 (5% type I error probable), β = 0.95 (95% of sample power) and data fatigue index reported in Vieira et al. 14 . The minimum number for each group was determined to be 5 volunteers, from which five participants were added to compensate possible dropouts during the study (amounting to 10 individuals per group) 16 involving a total of 40 participants. ...
... Analyzes of EMG data were done through software (Emg Works Analysis 3.1.5, Delsys®, Massachusetts, USA) and the RMS calculated from the average of the 3 sets performed 14 . ...
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Many studies have demonstrated the effectiveness of low-level laser therapy (LLLT) on muscle performance. Nonetheless, ideal application parameters are not known yet. The interval from the laser application moment until the time of the exercise is amongst them. In addition, the literature does not offer adequate studies that analyse different interval times in the same test in humans. Thus, the present study proposes the examination of the two distinct intervals, from the irradiation moment to the instant of the exercise performance. Forty male volunteers were recruited and randomly divided into four groups - control, placebo, immediate laser and 10 min after laser – to participate in this study. The therapy was performed with laser at 830 nm, with a power of 30 mW, energy of 3 J, during a time of 100 seconds per point irradiation, in the belly of the biceps brachii muscle. The comparison of the groups consisted in the Max force analysis, muscular power and muscle fatigue tests executed in the isokinetic dynamometer, and the recruitment of fibers by electromyography surface (EMG) and blood lactate levels in the brachial biceps muscle of weight training practitioners. A significant level of 5% (p <0.05) was considered for data analysis. The parameters adopted in the application of LLT significantly increased muscle activity (RMS) in all protocols (peak force, power and muscular endurance). In addition, LLLT was also effective in maintaining muscle performance. It was concluded that the interval time from the moment of application of the LLLT until the performance of the exercise can influence in a different way the physical capacities tested.
... The literature indicates that photobiomodulation therapy (PBMT) can delay muscle fatigue during maximum and submaximal contractions (9)(10)(11) . The benefits of photobiomodulation therapy for muscle tissue also include better muscle performance, greater strength gain, and muscle relaxation (12)(13)(14) . ...
... Another study (9) found a lower fatigue index in the femoral quadriceps of healthy women who trained for nine consecutive weeks. In this case, a laser with wavelength of 808 nm was applied immediately after each training session (9) . ...
... Another study (9) found a lower fatigue index in the femoral quadriceps of healthy women who trained for nine consecutive weeks. In this case, a laser with wavelength of 808 nm was applied immediately after each training session (9) . Photobiomodulation therapy with a 808-nm-wavelength laser, before exercise, led to a significantly lower dynamometric fatigue index of the plantar flexor muscles in healthy adults compared to both the control and the placebo group (16) . ...
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Purpose: To compare the immediate effects of laser photobiomodulation at wavelengths of 660 nm and 808 nm on fatigue of the orbicularis oris. Methods: This is a randomized study with 60 women aged between 19 and 43 years. The participants were divided into four groups. Group RG received photobiomodulation with a laser wavelength of 660 nm at four points of the orbicularis oris; group IRG received photobiomodulation with a laser wavelength of 808 nm at the same points; the control group did not receive light treatment; and the placebo group underwent the same procedures as RG and IRG but with the equipment switched off. The irradiation was performed with a laser of 100 mW of power, 4 J of energy per point and 133.3 J/cm2 of fluency. An electromyography evaluation was performed before and after the irradiation, concomitantly with the exercise of lip protrusion maintained until the sensation of fatigue. Fatigue was evaluated by a median frequency using the electromyographic fatigue index. The amplitude of the signal was evaluated, examining the root mean square, and the values were normalized by the peak. The difference in amplitude between the upper and lower lips was also analyzed. All variables were compared before and after irradiation. Results: No significant difference was found between the measures taken before and after irradiation. Conclusion: Photobiomodulation with the parameters investigated in this study had no immediate effect on orbicular oris fatigue.
... The laser was applied after the daily exercise regimen because the stress induced from exercise results in the maximal absorption and metabolic effects. The same protocol was previously used by our laboratory [11,15]. All animals were handled similarly, promoting the same routine. ...
... The results obtained in this study suggest that the use of a low-intensity laser (830 nm) is more effective when combined with exercise. On the other hand, this change in adipocyte area has been suggested to occur by both increased mitochondrial structure [10,11,27] and function [15]. Furthermore, the increase citrate synthase activity in ECL and EHL groups highlights the influence of these treatments (exercise and LLLT) on the process of mitochondrial biogenesis and, most importantly, on the active biogenesis of mitochondria. ...
... Photonic technology, here represented by low-level laser therapy and Light Emitting Diode (LED), is a widely used technology in the ield of health, such as skin cancer [3], orofacial lesions [4], dermatological treatments [5], physiotherapeutic rehabilitation [6], healing of venous ulcers [7], among others. ...
... The laser was applied after the exercises because the advantage of using the stress induced to get the maximum of absorption and effects on metabolism. It was used the same protocol before in different papers from our laboratory [17]. ...
... When the variables total body fat, trunk fat and visceral fat were analysed (Table 1), it was possible to observe their decrease in both groups, however, this decrease was more pronounced for the phototherapy group. Thus, it is possible to observe that the combination of moderate intensity exercises, nutritional education and low level laser therapy, was more efficient, as confirmed by previous studies [21][22][23][24][25]37,39]. These reductions may lead to the decrease in the likelihood of comorbidities, such as hypertension [8,40], various cardiovascular problems [3,40] insulin resistance and diabetes mellitus type 2 [3,41]. ...
... The laser was applied after the exercises, using the stress induced by the physical activity to get the maximum of absorption and effects on metabolism. The same protocol was tested and used in earlier studies performed by our research group [18]. ...
... In species other than rats, a small knowledge of LLLT responses, although various reviews have confirmed the advantages of LLLT in enhancing muscle function in dystrophic mice [27,28,29]. In this perspective, an experimental model of electrical nerve stimulation was used to induce fatigue by muscle contraction in mice and assess the influence of low-level laser therapy irradiation with various doses and wavelengths on development of skeletal muscle fatigue which could be relevant to rehabilitation and sports medicine [30]. ...
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The aim of this study was to evaluate the influence of pre-exercise muscle irradiation with various low-level laser therapy (LLLT) wavelengths and doses on skeletal muscle performance and fatigue after muscle contractions in in-situ mouse model using gastrocnemius muscle. Thirty-nine Swiss mice were arbitrarily allocated into control group and twelve LLLT irradiated groups receiving one of four different laser doses in the range 0.25-3.0 J from one of three wavelengths (637, 785 and 1064 nm) at one point on the gastrocnemius muscle before the fatigue protocol induced by electrical stimulation. Skeletal muscle fatigue was defined by fatigue index, half-relaxation time and force-time integration for all the 140 muscle contractions. At the 70th contraction, five laser irradiated groups (637 nm 0.5 J, 785 nm 0.5 J, 785 nm 0.75 J, 1064 nm 0.5 J and 1064 nm 1.5 J) had a significant difference (P<0.05) in terms of fatigue index. While, at the 140th contraction, only 637 nm 0.5 J and 1064 nm 0.5 J groups significantly differ (P<0.05) from control group. In term of half-relaxation time and force-time integration, there was no significant difference. These results indicate that LLLI has both wavelength and dose dependent effects on the gastrocnemius muscle and LLLI at appropriate wavelengths and dosage can enhance skeletal muscle performance and delays muscle fatigue.
... Regarding the type of training, studies have investigated the effects of PBM mainly on strength training 13,17 and endurance. 14, 16 Positive effects have been reported when PBM was applied before the exercise, for outcomes such as time until exhaustion and number of repetitions, 19 maximal voluntary contraction, 20 creatine kinase (CK) and lactate, 21 and when PBM was applied after the exercise, for outcomes such as peak torque and 1 repetition maximum (RM) test. 22 Taken together, these preliminary findings suggest that the ergogenic and protective effects may be enhanced when the PBM is applied during a training session that combines strength and endurance exercises. ...
Article
Background Previous studies have shown positive results of photobiomodulation (PBM) for improving performance and accelerating post-exercise recovery. However, the effects of PBM in healthy individuals who underwent a neuromuscular adaptation training remain unclear. Objective To investigate the effects of PBM during a training program combining sprints and explosive squats exercises on clinical, functional, and systemic outcomes in trained healthy individuals compared to a placebo intervention and a control. Methods We conducted a randomized placebo-controlled trial. Healthy males were randomly assigned to three groups: active PBM (30 J per site), placebo, or control (passive recovery). The participants performed a six-week (12 sessions) of a training program consisting of a combination of sprints and squats with recovery applied between sprints and squats. To prevent the influence of the primary neuromuscular adaptation to exercise on the results, all participants had to participate in a period of six weeks of exercise training program. Functional, clinical, and psychological outcomes and vascular endothelial growth factor (VEGF) were assessed at baseline and after six weeks. Results are expressed as mean difference (MD) and 95% confidence intervals (CI). Results Thirty-nine healthy male volunteers (aged 18–30 years; body mass index 23.9 ± 3 kg/m²) were recruited. There was no significant time by group interaction, and no significant effect of group, but there was a significant effect of time for maximal voluntary isometric contraction (primary outcome) (MD=22 Nm/kg; 95%CI: 3.9, 40) and for squat jump (MD=1.6 cm; 95CI%: 0.7, 2.5). There was no significant interaction (time*group), time, or group effect for the other outcomes. Conclusion The addition of PBM to a combined training performed for 6 weeks in previously trained individuals did not result in additional benefits compared to placebo or no additional intervention.
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Three dimensional reconstruction is a highly beneficial method of object creation using a photo-realistic way especially in medical applications. For 3D ear scanner application (such as hearing aid), the accuracy in ear details and measurement is the main issue that should be put in consideration, also the mobility and ease of use is the second issue. This work has presented the theoretical and experimental approach for design a low cost handled 3D ear scanner. In this paper, we have proposed a 3D ear canal reconstruction system based on optical scanner to reconstruct the ear canal. A low-cost ears-cope with proposed software based on Distance Regularized Level Set Evolution (DRLSE) Segmentation algorithm has been utilized in order to reconstruct ear canal from image that captured by ear-scope in real-time. The results shows good accuracy of ear canal details and measurement that related to reconstruction algorithm and reconstruction software that yield acceptable 3D meshes of the ear canal
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Physiological variables, such as maximum work rate or maximal oxygen uptake (V̇O2max), together with other submaximal metabolic inflection points (e.g. the lactate threshold [LT], the onset of blood lactate accumulation and the pulmonary ventilation threshold [VT]), are regularly quantified by sports scientists during an incremental exercise test to exhaustion. These variables have been shown to correlate with endurance performance, have been used to prescribe exercise training loads and are useful to monitor adaptation to training. However, an incremental exercise test can be modified in terms of starting and subsequent work rates, increments and duration of each stage. At the same time, the analysis of the blood lactate/ventilatory response to incremental exercise may vary due to the medium of blood analysed and the treatment (or mathematical modelling) of data following the test to model the metabolic inflection points. Modification of the stage duration during an incremental exercise test may influence the submaximal and maximal physiological variables. In particular, the peak power output is reduced in incremental exercise tests that have stages of longer duration. Furthermore, the VT or LT may also occur at higher absolute exercise work rate in incremental tests comprising shorter stages. These effects may influence the relationship of the variables to endurance performance or potentially influence the sensitivity of these results to endurance training. A difference in maximum work rate with modification of incremental exercise test design may change the validity of using these results for predicting performance, and prescribing or monitoring training. Sports scientists and coaches should consider these factors when conducting incremental exercise testing for the purposes of performance diagnostics.
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OBJECTIVE: To analyze the activity and electrophoretic pattern of the enzyme LDH in response to treadmill training, in rats undergoing photostimulation using low-level laser therapy (LLLT) (780 etam). METHOD: Fifty-four 30-day-old male Winstar rats initially weighing 112 ± 4.7g were divided into four groups. Two groups remained at rest: resting control group (RCG, n= 9) and resting LLLT group (RLG, n= 10). The other two groups underwent a five-week treadmill program of aerobic training and non-continuous incremental effort tests, with the aim of determining the anaerobic limit. One of the latter was an exercise control group (ECG, n= 16) and the other was an exercise LLLT group (ELG, n= 19). LLLT was applied to the quadriceps, gluteus maximus, soleus and tibialis anterior, bilaterally, immediately after each training session, using the following: 3.8 J/cm²; 15 mW; time 10 s; continuous mode. Samples of the soleus, tibialis anterior and heart were removed 48 hours after the last exercise session for electrophoretic and spectrophotometric analysis. The statistical analyses used were the ANOVA and post-hoc Tukey tests. The level of statistical significance was set at p
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ACSM Position Stand on The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Adults. Med. Sci. Sports Exerc., Vol. 30, No. 6, pp. 975-991, 1998. The combination of frequency, intensity, and duration of chronic exercise has been found to be effective for producing a training effect. The interaction of these factors provide the overload stimulus. In general, the lower the stimulus the lower the training effect, and the greater the stimulus the greater the effect. As a result of specificity of training and the need for maintaining muscular strength and endurance, and flexibility of the major muscle groups, a well-rounded training program including aerobic and resistance training, and flexibility exercises is recommended. Although age in itself is not a limiting factor to exercise training, a more gradual approach in applying the prescription at older ages seems prudent. It has also been shown that aerobic endurance training of fewer than 2 d·wk-1, at less than 40-50% of V˙O2R, and for less than 10 min-1 is generally not a sufficient stimulus for developing and maintaining fitness in healthy adults. Even so, many health benefits from physical activity can be achieved at lower intensities of exercise if frequency and duration of training are increased appropriately. In this regard, physical activity can be accumulated through the day in shorter bouts of 10-min durations. In the interpretation of this position stand, it must be recognized that the recommendations should be used in the context of participant's needs, goals, and initial abilities. In this regard, a sliding scale as to the amount of time allotted and intensity of effort should be carefully gauged for the cardiorespiratory, muscular strength and endurance, and flexibility components of the program. An appropriate warm-up and cool-down period, which would include flexibility exercises, is also recommended. The important factor is to design a program for the individual to provide the proper amount of physical activity to attain maximal benefit at the lowest risk. Emphasis should be placed on factors that result in permanent lifestyle change and encourage a lifetime of physical activity.
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The data on the aftereffect of He-Ne laser light (λ = 632.8 nm) on mitochondria of yeasts in late log phase were reviewed. The quantitative analysis of the ultrathin cell sections demonstrated a nonuniform thickness of the giant branched mitochondria typical for budding yeasts. Exposure to a dose of 460 J/m2 (accelerating cell proliferation and activating respiratory chain enzymes, cytochrome c oxidase and NADH dehydrogenase), changed the macrostructure of the giant mitochondria—much of the narrow regions of the mitochondrial tube with profiles ≤0.06 µm2 were expanded (while no signs of organelle damage were observed). Such mitochondria are characterized by increased relative surface area of the cristae, which can be due to the activation of their respiration and ATP synthesis. The number of associations between mitochondria and endoplasmic reticulum increased in irradiated cells in early log phase, which reflects the increased capacity of mitochondria to uptake Ca2+. Altered giant mitochondria configuration can increase the efficiency of both energy transfer and Ca2+ propagation through the cytoplasm.
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Studies suggest that high-intensity physical exercise can cause damage to skeletal muscles, resulting in muscle soreness, fatigue, inflammatory processes and cell apoptosis. The aim of this study was to investigate the effects of low-level laser therapy (LLLT) on a decrease in creatine kinase (CK) levels and cell apoptosis. Twenty male Wistar rats were randomly divided into two equal groups: group 1 (control), resistance swimming; group 2 (LLLT), resistance swimming with LLLT. They were subjected to a single application of indium gallium aluminum phosphide (InGaAlP) laser immediately following the exercise for 40s at an output power of 100mW, wavelength 660nm and 133.3J/cm2. The groups were subdivided according to sample collection time: 24h and 48h. CK was measured before and both 24h and 48h after the test. Samples of the gastrocnemius muscle were processed to determine the presence of apoptosis using terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP) nick end labeling. (There was a significant difference in CK levels between groups (P < 0.0001) as well as between the 24h and 48h levels in the control group, whereas there was no significant intra-group difference in the LLLT group at the same evaluation times. In the LLLT group there were 66.3 ± 13.2 apoptotic cells after 24h and 39.0 ± 6.8 apoptotic cells after 48h. The results suggest that LLLT influences the metabolic profile of animals subjected to fatigue by lowering serum levels of CK. This demonstrates that LLLT can act as a preventive tool against cell apoptosis experienced during high-intensity physical exercise.
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Our aim was to investigate the immediate effects of bilateral, 830nm, low-level laser therapy (LLLT) on high-intensity 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 (830nm wavelength, 100mW, spot size 0.0028cm2, 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: 30s 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 (2.52Ul−1 ± 7.04Ul−1) than for those given placebo LLLT (28.49Ul−1 ± 22.62Ul−1). For the soccer athletes, the change in blood lactate levels from before exercise to 15min after exercise was significantly lower (P < 0.01) in the group subjected to active LLLT (8.55mmoll−1 ± 2.14mmoll−1) than in the group subjected to placebo LLLT (10.52mmoll−1 ± 1.82mmoll−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 post-exercise recovery.
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Low-level laser (light) therapy (LLLT) has been known since 1967 but still remains controversial due to incomplete understanding of the basic mechanisms and the selection of inappropriate dosimetric parameters that led to negative studies. The biphasic dose-response or Arndt-Schulz curve in LLLT has been shown both in vitro studies and in animal experiments. This review will provide an update to our previous (Huang et al. 2009) coverage of this topic. In vitro mediators of LLLT such as adenosine triphosphate (ATP) and mitochondrial membrane potential show biphasic patterns, while others such as mitochondrial reactive oxygen species show a triphasic dose-response with two distinct peaks. The Janus nature of reactive oxygen species (ROS) that may act as a beneficial signaling molecule at low concentrations and a harmful cytotoxic agent at high concentrations, may partly explain the observed responses in vivo. Transcranial LLLT for traumatic brain injury (TBI) in mice shows a distinct biphasic pattern with peaks in beneficial neurological effects observed when the number of treatments is varied, and when the energy density of an individual treatment is varied. Further understanding of the extent to which biphasic dose responses apply in LLLT will be necessary to optimize clinical treatments.
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This study aimed to investigate the effect of 830 nm low-level laser therapy (LLLT) on skeletal muscle fatigue. Ten healthy male professional volleyball players entered a crossover randomized double-blinded placebo-controlled trial. Active LLLT (830 nm wavelength, 100 mW output, spot size 0.0028 cm(2), 200 s total irradiation time) or an identical placebo LLLT was delivered to four points on the biceps humeri muscle immediately before exercises. All subjects performed voluntary biceps humeri contractions with a load of 75% of the maximum voluntary contraction (MVC) force until exhaustion. After active LLLT the mean number of repetitions was significantly higher than after placebo irradiation [mean difference 4.5, standard deviation (SD) +/- 6.0, P = 0.042], the blood lactate levels increased after exercises, but there was no significant difference between the treatments. We concluded that 830 nm LLLT can delay the onset of skeletal muscle fatigue in high-intensity exercises, in spite of increased blood lactate levels.
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Recent studies have investigated whether low level laser therapy (LLLT) can optimize human muscle performance in physical exercise. This study tested the effect of LLLT on muscle performance in physical strength training in humans compared with strength training only. The study involved 36 men (20.8±2.2 years old), clinically healthy, with a beginner and/or moderate physical activity training pattern. The subjects were randomly distributed into three groups: TLG (training with LLLT), TG (training only) and CG (control). The training for TG and TLG subjects involved the leg-press exercise with a load equal to 80% of one repetition maximum (1RM) in the leg-press test over 12 consecutive weeks. The LLLT was applied to the quadriceps muscle of both lower limbs of the TLG subjects immediately after the end of each training session. Using an infrared laser device (808 nm) with six diodes of 60 mW each a total energy of 50.4 J of LLLT was administered over 140 s. Muscle strength was assessed using the 1RM leg-press test and the isokinetic dynamometer test. The muscle volume of the thigh of the dominant limb was assessed by thigh perimetry. The TLG subjects showed an increase of 55% in the 1RM leg-press test, which was significantly higher than the increases in the TG subjects (26%, P = 0.033) and in the CG subjects (0.27%, P < 0.001). The TLG was the only group to show an increase in muscle performance in the isokinetic dynamometry test compared with baseline. The increases in thigh perimeter in the TLG subjects and TG subjects were not significantly different (4.52% and 2.75%, respectively; P = 0.775). Strength training associated with LLLT can increase muscle performance compared with strength training only.