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Effects of low level laser therapy (808 nm) on physical strength training in humans

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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.
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1 23
Lasers in Medical Science
ISSN 0268-8921
Volume 26
Number 3
Lasers Med Sci (2011)
26:349-358
DOI 10.1007/
s10103-010-0855-0
Effects of low level laser therapy (808 nm)
on physical strength training in humans
1 23
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ORIGINAL ARTICLE
Effects of low level laser therapy (808 nm) on physical
strength training in humans
Cleber Ferraresi &Taysa de Brito Oliveira &Leonardo de Oliveira Zafalon &
Rodrigo Bezerra de Menezes Reiff &Vilmar Baldissera &
Sérgio Eduardo de Andrade Perez &Euclides Matheucci Júnior &
Nivaldo Antônio Parizotto
Received: 3 August 2010 / Accepted: 21 October 2010 / Published online: 18 November 2010
#Springer-Verlag London Ltd 2010
Abstract 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 perfor-
mance compared with strength training only.
Keywords Low level laser therapy (LLLT) .High-intensity
exercise .Isokinetic Dynamometer .Leg press .
One-repetition maximum test
Introduction
Strength training, mainly high-intensity exercises, uses
energy from anaerobic metabolism and promotes changes
in the contractile characteristics of the muscle fibers
involving a transition from type I and type IIx to type IIa.
An increase in fiber recruitment, and the timing and firing
frequency of motor units also occurs with this kind of
exercise [1,2]. In addition, strength training increases
muscle cross-sectional area (hypertrophy), which is associ-
ated with neural adaptation of muscle recruitment, increas-
ing muscle strength and performance [1,2].
C. Ferraresi (*):T. de Brito Oliveira :L. de Oliveira Zafalon :
N. A. Parizotto
Laboratory of Electrothermophototherapy,
Department of Physical Therapy,
Federal University of São Carlos,
Rodovia Washington Luís, km 235,
13565-905, São Carlos, SP, Brazil
e-mail: cleber.ferraresi@gmail.com
C. Ferraresi :E. M. Júnior
Department of Biotechnology, Federal University of São Carlos,
São Carlos, SP, Brazil
R. B. de Menezes Reiff
Department of Orthopedics and Traumatology,
University of São Paulo,
Cerqueira César, SP, Brazil
V. Baldissera :S. E. de Andrade Perez
Laboratory of Physiology of Exercise,
Department of Physiological Sciences, Federal University of São
Carlos,
São Carlos, SP, Brazil
Lasers Med Sci (2011) 26:349358
DOI 10.1007/s10103-010-0855-0
Author's personal copy
In general, exercises can be carried out in two ways:
closed kinetic chain (CKC) and open kinetic chain (OKC)
[3,4]. CKC exercises involve multiple articulations with
body weight or random loads being unloaded on a distal
body segment that is fixed to the ground or another base,
such as in squats or leg-press exercises. OKC exercises
generally involve movement in only one articulation, and
have the workload fixed on a distal extremity of the body
segment that is free to move, such as in knee extension
fitness equipment [5].
The measurement of muscle performance in CKC and
OKC exercises usually involves isotonic tests including
the one-repetition maximum leg-press (1RMleg) test
(CKC) and isokinetic muscle performance in isokinetic
dynamometry (MPID), especially in activities involving
knee extension (OKC) [6,7]. These tests allow more
complete evaluations and assist in directing training
programs [8].
The desire to increase and/or accelerate the gains in
physical performance, such as muscle hypertrophy and
enhancement of aerobic and anaerobic capacities, often
leads athletes and sportsmen to improve their nutrition [9].
Androgenic substances can also can be used but they may
pose risks to health [10]. The potential of low level laser
therapy (LLLT) for improving performance in exercises,
such as strength and resistance to fatigue has been tested
[11,12].
LLLT is mainly used for local pain control and tissue
repair [13,14]. It interacts with the cellular mitochondria,
promoting structural changes (appearance of giant mito-
chondria) and metabolic changes (increased oxidative
enzyme activity), increasing energy synthesis (ATP) for
metabolic processes [15,16]. Thus, the few recent studies
with laser therapy in men during physical exercise have
concentrated on investigating fatigue and muscle damage
after acute exercise of high intensity, and have involved the
determination of the concentrations and kinetics of bio-
chemical markers such as lactate and muscle creatine kinase
[12,17,18]. However, some studies reported in the
literature are divergent as to the effectiveness of LLLT in
increasing muscle performance in humans [11,18]. In these
studies, LLLT parameters such as dose and wavelength are
defined in terms of the depth of tissue reached by the
energy and consequently its attenuation, which directly
influences the therapeutic effect in the target tissue [13].
Furthermore, infrared laser radiation seems to be better for
stimulating muscle tissue because it can penetrate the skin
layers and reach greater depths without significant loss of
energy [13].
The purpose of this study was to determine whether
LLLT is able to optimize the effects of chronic strength
training. It was hypothesized that a chronic strength training
program associated with LLLT would promote a greater
increase in muscle performance than strength training
alone. The study was a randomized controlled clinical trial
with three tools to measure muscle performance: (1)
1RMleg test, (2) MPID test (knee torque extensor), and
(3) thigh perimetry as a measure of changes in thigh
volume.
Materials and methods
This 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 (approval no. 342/2008) and the study was regis-
tered with NIH ClinicalTrials (NCT01113021). The sub-
jects were recruited from among graduate students at the
university. All volunteers were informed about the study
purposes and procedures. After inclusion in the trial, all
subjects signed a consent form.
Subjects
The study participants were 36 male subjects who reported
being clinically healthy.
Inclusion criteria
The inclusion criteria were: healthy males aged between 18
and 28 years with a body mass index (BMI) equal to or less
than 26 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, in accordance with previous studies [7,19].
Exclusion criteria
The exclusion criteria were: previous injury to the femoral
quadriceps or hamstring muscles (within 6 months prior to
study), osseous or articular disorder in the lower limbs,
cardiovascular system disorders, systemic disease, and
taking prescription medicines or using dietary supplements
(such as muscle mass builders).
After entering the study, subjects who did not comply
properly with the training routine, missed two consecutive
training sessions or developed any osseous or muscle or
articular injuries were excluded.
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).
350 Lasers Med Sci (2011) 26:349358
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Study groups
TG and TLG subjects were submitted to a dynamic strength
training program involving the leg-press exercise twice a
week for 12 consecutive weeks. Soon after the end of each
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 45° leg press
(ReForce, São Paulo, Brazil) for the 1RMleg test; a
goniometer (ISP, São Paulo Institute, São Paulo, Brazil) to
determine knee flexion angle in the 1RMleg test; a digital
Qwik Time QT5 metronome to standardize the timing of
concentric and eccentric muscle contractions during training;
a computerized isokinetic dynamometer (Multi-Joint System
3; Biodex, New York,NY) to record the isokinetic variables in
the MPID test; and a metric tape (3M, model Sanny, Brazil) to
measure the thigh perimeter of the subjects.
Procedures
The baseline assessments were carried out in the morning
and consisted primarily of recording the subjectsthigh
perimeter, followed by the MPID test. The MPID test
recorded the values for PT.ext. (knee peak torque extensor
of two series of evaluation) and Avg.PT.ext. (knee peak
torque extensor, average of two evaluation series). The
afternoon of the same day the 1RMleg test was performed.
The results of these muscle performance assessments were
normalized to the individual body mass (BM) and multi-
plied by 100, following the procedure described previously
[20]. All subjects were instructed not to change their usual
physical routine or eating habits during the study, not to
ingest alcohol, and to sleep well (both in quantity and
quality).
A pilot study was also conducted to establish the
reliability of the 1RMleg test, the MPID test and thigh
perimetry. The two tests were applied by the same
investigator randomly to six subjects who were not part of
the study on two separate occasions and separated by a 5-
day interval. The intraclass correlation coefficient (ICC 3,1)
was used to assess intraexaminer reliability and the standard
error of measurement (SEM) to describe measurement
accuracy. The results were: ICC 0.92, SEM (5.00 Nm/
BM)×100, for Avg.PT.ext.; ICC 0.93, SEM (5.17 Nm/
BM)×100, for PT.ext.; ICC 0.99, SEM (0.71 kg/BM)×100,
for the 1RMleg test; and ICC 0.99, SEM 0.01 cm, for
thigh perimetry.
Protocols for assessments, training and LLLT
All protocols for muscle performance assessments and
workload adjustment were performed by the same evalu-
ator. It is important to note that the assessment at baseline
and after 12 weeks were conducted on different training
days and that the assessment results were normalized by
subject BM at both the beginning and the end of the study.
Protocol I (thigh perimetry) The thigh perimeter was
measured midway between the anterior/superior iliac spine
and the base of the patella of the subjects dominant lower
limb. The dominant lower limb was determined as that used
to kick a ball with greater accuracy. This assessment was
performed in orthostatic position and with the thigh
muscles relaxed. The thigh perimeter was measured only
at baseline and after 12 weeks of strength training.
Protocol II (isokinetic dynamometry) A brief 5-min warm-
up was carried out on a cycle ergometer (Ergo 167 Cycle;
Ergo-FIT, Pirmasens, Germany) with a load of 100 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 guide-
lines for the device. The evaluation was performed only on
the subjects dominant lower limb, and the dynamometer
rotation axis was adjusted to the knee axis of the subject
being assessed (at the lateral epicondyle of the femur;
Fig. 1a). The hip was stabilized in 80° flexion and the lever
arm of the equipment was set approximately 1 cm above
the tibial malleolus. Parameters such as chair height,
backrest distance, seat level and dynamometer base were
adjusted for each subject.
Before starting the recording of isokinetic variables,
there was a familiarization period with the apparatus that
consisted of three submaximal voluntary concentric muscle
contractions in the full range of standardized and preprog-
rammed motion (9020°), with a constant angular velocity
of 60°/s. After a 3-min rest, the test began with two sets
(separated by a 3-min interval) of five maximal voluntary
concentric and reciprocal quadriceps and hamstring con-
tractions in all ranges of standardized and preprogrammed
knee motion in flexion and extension (Fig. 1b). The
subjects were encouraged verbally and visually to achieve
maximum effort. This evaluation was performed only at the
baseline and after 12 weeks of strength training. Only those
findings with a coefficient of variation less than 10% were
accepted [21].
Protocol III (1RMleg test) There was a brief warm-up
period of 5 min on a cycle ergometer (Ergo 167 Cycle;
Lasers Med Sci (2011) 26:349358 351
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Ergo-FIT, Pirmasens, Germany) with a load of 100 W and a
speed in the range 6070 rpm. Next, the load-lifting
technique was demonstrated by the evaluator. The test was
standardized by defining the subjects lower limb extension,
identifying 90° knee flexion (using the goniometer) and
marking the position (in centimeters) corresponding to this
angle on the leg-press machine. The proposed range of motion
was 0° (full knee extension, start) to 90° (finish). The
anatomical references for the identification of the desired
angle were the greater trochanter of the femur, lateral
epicondyle of the femur and the malleolus of the fibula of
the same lower limb (Fig. 1c). Before beginning the test,
there was a familiarization period with the apparatus
consisting of ten repetitions with a load estimated less than
60% of 1RM. This subjective load was identified in
accordance with the level of physical effort by the subject
during the familiarization period, following the OMNI scale
(0 equal extremely easy and 10 equal extremely hard) [22].
The load increments for identifying the 1RMleg were in
terms of percentage of the load in the familiarization period,
and depended on the subject's score on the OMNI scale. The
load choices were limited to five attempts, separated by 5-
min intervals to avoid metabolic disorders and impairment of
test quality. The subjects were encouraged verbally to
achieve maximum effort.
Protocol IV (training) TG and TLG subjects began the
strength training program based on specific scientific data
in the literature [23,24] after 2 days of baseline assess-
ments. The training program consisted of twice-weekly
training sessions for the leg-press exercise at 45° on
nonconsecutive days. The total training period was 12
consecutive weeks (3 months), giving a total of 24
sessions. The training intensity was always 80% and
the training volume was 50 repetitions divided into five
sets of ten repetitions each. If the subject could not
complete ten repetitions in each set, he would continue
until concentric muscle failure and then rest. The rest
interval between sets was 2 min and the exercise speed
was governed by the metronome: 2 s eccentric muscle
action for each second of concentric action [23]. During
all training sessions (the leg-press exercise and the
1RMleg test) the heart rate of subjects and the range of
motion of the lower limbs were monitored to validate the
training and load in the 1RMleg test. The room temper-
ature was maintained between 23°C and 26°C. Adjust-
ments in workload were made by retesting the 1RMleg
every eight sessions during normal training (thus replacing
the session). Two days after the 24th session, subjects
underwent a final thigh perimetry assessment, followed by
final MPID and the 1RMleg test.
Protocol V (LLLT) TLG subjects underwent a LLLT
protocol immediately after each training session. A contact
technique was used for the infrared laser treatment. The
beam was kept stationary and perpendicular to the skin
during the 24 sessions in seven areas distributed over the
belly of the femoral quadriceps muscle of each subject in
previously demarcated areas. The first area was 10 cm
below the superior-anterior iliac spine and the others were
every 5 cm below the initial marks (Fig. 5, part A). The
pattern in each areas was recorded to make the laser
applications uniform between sessions. A near-infrared
laser device (GaAlAs, 808 nm) with six obliquely arranged
diodes of 60 mW power each was used operating in
continuous mode with the following parameters: beam area
0.0028 cm
2
; energy per point (diode) 0.6 J; per-session total
energy in each lower limb 25.2 J (for a total of 50.4 J);
application points 42 (for a total of 84 points); diode energy
density (fluency) 214.28 J/cm
2
; diode power density
21.42 W/cm
2
; and an application time in each lower limb
of 70 s (for a total time of 140 s, both lower limbs).
Fig. 1 a Subject positioning for the MPID test. bRange of motion developed in the MPID test. cSubject positioning in the 1RMleg test and
definition of knee angle flexion
352 Lasers Med Sci (2011) 26:349358
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Statistical analysis
The normality of the data distribution was analyzed using
the Shapiro-Wilk test and the homogeneity of variances
using Levenes test. The effects of training on 1RMleg,
MPID and thigh perimetry were evaluated by two-way
analysis of variance (ANOVA) 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. The training effect
was also analyzed in terms of the percentage change in the
variables studied in relation to baseline (considered 100%)
and was compared among the groups by the Kruskal-Wallis
ANOVA test. Significance was set at P<0.05.
Results
The study began with 36 male subjects who met all the
inclusion criteria and signed a consent form. However, six
subjects were excluded during the study for the following
reasons: one subject did not agree with the group to which
he was randomly allocated, three were injured during
training and two CG subjects began a physical training
program during the study. Thus, our final sample size was 30
subjects, ten in each group. TLG subjects had a mean age of
19.7±0.8 years, a mean weight 76.6±11.5 kg, a mean height of
1.78±0.06 m and a BMI of 23.3±2.1 kg/m
2
.TGsubjectshad
a mean age of 21.2±2.5 years, a body weight of 75.7±6.3 kg,
a mean height of 1.78±0.05 m and a BMI of 23.7±1.9 kg/m
2
.
CG subjects had a mean age 21.8±2.1 years, a body weight
of 77.1±13.5 kg, a mean height of 1.80±0.05 m and a BMI
of 22.4±3.1 kg/m
2
.
The baseline 1RMleg, MPID and thigh perimetry
assessments were compared among the three groups to
identify any statistically significant differences. No signif-
icant difference was observed in any variable (P> 0.05) at
baseline. BM used for muscle performance normalization
of the 1RMleg and MPID test results changed after the
training program, but not significantly (P> 0.05). The TLG
subjects showed an increase in BM of 1.30%, the TG
subjects an increase of 1.50% and the CG subjects an
increase of 0.12%. The TLG and TG subjects showed
significant increases (P<0.001) in the 1RMleg after the
strength training program. The 1RMleg in the TLG subjects
was higher (P<0.001) than that in the CG subjects and not
significantly different from that in the TG subjects (P=
0.748). The TG subjects had a higher 1RMleg (P=0.008)
than the CG subjects. In terms of average percentage, the
1RMleg in the TLG subjects increased by 55.59%, in the
TG subjects by 26.83% and in the CG subjects by 0.27%.
Comparing the groups, the TLG subjects had a higher
percentage gain than the TG subjects (P=0.033) and the
CG subjects (P<0.001). The TG subjects had a higher
percentage gain than the CG subjects (P= 0.033). These
changes in the load in 1RMleg test are summarized in
Fig. 2and the percentages in Table 1.
The MPID test results were higher in the TLG and TG
subjects after the strength training program but only the
TLG subjects showed statistically significant increases in
Avg.PT.ext. (P=0.003) and PT.ext. (P=0.036). The com-
parison among the groups did not identify significant
differences (P>0.05). In terms of percentages, the TLG
subjects showed an increase in Avg.PT.ext. of 7.38% and in
PT.ext. of 4.67%. In terms of percentage comparisons, the
values of Avg.PT.ext. and PT.ext. in the TLG subjects were
significantly higher than the values in the CG subjects
(P<0.001, P=0.001, respectively). There were no significant
differences (P>0.05) between the TLG and TG subjects or
between the TG and CG subjects. These changes in the
MPID test results are summarized in Fig. 3and the
percentages are shown in Table 1.
The thigh perimeter of the dominant lower limb
increased significantly in TLG and TG subjects (P<
0.001). CG subjects showed a decrease in thigh perimeter
without statistical significance (P=0.999). In terms of
percentage change in thigh perimeter, the TLG subjects
showed an increase of 4.52%, the TG subjects an increase
of 2.75% and the CG subjects a decrease of 0.53%.
Comparing these percentages among groups, the thigh
perimeter in the TLG subjects was significantly higher than
in the CG subjects (P<0.001) but not significantly different
from that in the TG subjects (P= 0.775). The thigh
perimeter in the TG subjects was significantly higher than
in the CG subjects (P=0.006). These changes in the thigh
Fig. 2 Loads in the 1RMleg test in the three study groups at baseline
and after 12 weeks of strength training (TLG training and LLLT group,
TG training only group, CG control group; BM body mass; *P<0.05)
Lasers Med Sci (2011) 26:349358 353
Author's personal copy
perimeter are summarized in Fig. 4and the percentages are
shown in Table 1.
Discussion
This study investigated whether LLLT combined with
physical strength training (80% of 1RM) would promote a
higher increase in muscle performance in CKC and OKC
exercises and in the higher thigh perimetry volume in
young men when compared with strength training without
LLLT. The 30 subjects who completed the program were
randomly distributed into three groups of equal size with no
significant differences at baseline. BM was used to
standardize the force measured in the CKC and OKC tests,
and it did not change significantly from baseline values (P>
0.05). Thus, it did not significantly affect muscle perfor-
mance in the final assessment.
After the 12 weeks of strength training, the 1RM load in
the leg-press test was significantly higher than the baseline
load in subjects of both the TLG and TG. However, there
was no significant difference in the CG subjects (P>0.999)
since there was no intervention involved. An increase in
muscle strength following a strength training program has
been well established [1,2].
There were no statistically significant differences be-
tween the TLG and TG subjects in terms of their means and
variances in the 1RMleg test after training (P= 0.748). Only
the differences between TLG and CG subjects (P< 0.001)
and between TG and CG subjects (P=0.008) were
significant. This may have been due to the initial average
Fig. 4 Thigh perimetry in the three study groups at baseline and after
12 weeks of strength training. *P<0.05
Fig. 3 Results of MPID test for the three study groups at baseline and
after 12 weeks of strength training. Avg.PT.ext. knee peak torque
extensor, average of two evaluation series; PT.ext. knee peak torque
extensor of two evaluation series. *P<0.05
Table 1 Percentage change (gains or losses) in muscle performance in the MPID test, 1RMleg test and perimetry, and comparisons among the
groups (Pvalues in the Kruskal-Wallis test)
Variable Percentage change after training Pvalues
TLG TG CG TLG × CG TLG × TG TG × CG
1RMleg 55.59 26.83 0.27 <0.001* 0.033* 0.033*
Avg.PT.ext. 7.38 3.16 2.97 <0.001* 0.639 0.092
PT.ext. 4.67 1.82 2.98 0.001* 0.401 0.126
Perimetry 4.52 2.75 0.5 <0.001* 0.775 0.006*
Avg.PT.ext. knee peak torque extensor, average of two evaluation series; PT.ext. knee peak torque extensor of two evaluation series; *P<0.05.
354 Lasers Med Sci (2011) 26:349358
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1RMleg load in the TLG subjects being smaller than the
initial load in the TG subjects (a difference of 49 kg),
although the difference was not significant (P=0.919).
Thus, despite the final load average in the 1RMleg test
being higher in the TLG subjects than in the TG subjects,
the difference was not significant (P=0.748). However,
considering the percentage increase, the TLG subjects
showed an increase of 55.5% in the 1RMleg test which
was significantly higher (P=0.033) than the increase of
26.8% in the TG subjects after the training program (see
Table 1).
When these groups were compared in the OKC MPID
test, only the TLG subjects showed an increase in average
knee peak torque extensor and the knee peak torque
extensor (Avg.PT.ext. and PT.ext.; see Fig. 3). Only the
TLG subjects showed higher MPT.ext. and PT.ext. values
in comparison with the CG subjects. However, no signif-
icant difference was observed between TLG and TG
subjects for MPID (see Fig. 3and Table 1). The low
percentage transfer of muscle performance between isotonic
CKC exercises and isokinetic OKC exercises found in this
study have been reported previously [4] and is due the
specificity of the training [8,25] and the form of evaluation
[6].
Some studies that have investigated muscle performance
in men undergoing physical exercise associated with LLLT
did not find significant improvements [11,18]. However,
other studies with similar methodologies have found highly
relevant results for fatigue reduction and improvement in
the muscle performance [12,17,18]. Since the fluency,
number of application points and total energy delivered to
muscle in previous studies have differed [11,12,17,18],
we decided to use a total energy similar to that used in the
study by Leal Junior et al. [18], which was 40 J. So the
fluency used was lower (214.28 J/cm
2
vs 1,428.57 J/cm
2
)
and the total number of application points was greater (84
points vs 10 points) to get the best energy distribution in the
femoral quadriceps muscle (Fig. 5, part A).
The evaluation methods used in previous studies
analyzed the kinetics of biochemical markers of fatigue
(lactate) and muscle damage (creatine kinase) [12,17,18].
These studies were randomized, double-blind, placebo-
controlled trials and showed significantly lower levels of
these markers and also an increase in the number of
maximal voluntary contractions, indicating a reduction in
the fatigue induced by exercise [12,17,18]. The authors
considered that the improved physical performance provid-
ed by the action of LLLT was a result of lower creatine
kinase activity, increased antioxidant levels and improve-
ment in microcirculation and lactate removal.
Adding to previous hypotheses, the present study
investigated three more possible physiological mechanisms
for the improvement in physical performance in humans
when exercise is associated with LLLT, all based on the
Fig. 5 AApplication points for LLLT on the femoral quadriceps
muscle. BMitochondrial creatine shuttle mechanism. In this mecha-
nism, creatine (Cr) is transported from the ATP-utilizing sites (e.g.,
myofibrils) to the mitochondria, and the phosphocreatine (PCr)is
transported in the opposite direction. Due to the presence of creatine
kinase (CK) in the inner mitochondrial membrane, the creatine reacts
with ATP produced during oxidative phosphorylation and resynthe-
sizes phosphocreatine. This process increases the ADP concentration
and it in turn stimulates respiration. However, the phosphocreatine
decreases the ADP concentration and respiration (ANT adenine
nucleotide translocase) (modified from Tonkonogi and Sahlin [27]).
CLactate oxidation in the mitochondrial pathway. The lactate is
transported to the intermembrane space or directly to the mitochon-
drial matrix, where it is oxidized to pyruvate by NAD
+
and this
reaction is catalyzed by lactate dehydrogenase mitochondrial enzyme
(mLDH). The reduced NAD (NADH) is oxidized in the electron
transport chain (ETC) and provides electrons and protons for the
aerobic production of ATP (mMCT mitochondrial monocarboxylate
transporters) (modified from Brooks et al. [31])
Lasers Med Sci (2011) 26:349358 355
Author's personal copy
importance of the cellular mitochondria in energy produc-
tion. There is strong evidence in the scientific literature that
LLLT has a close relationship with the mitochondria,
promoting their growth and/or fusion of smaller mitochon-
dria to form giant mitochondria consequently increasing the
mitochondrial density in the tissues [15,16]. Greater
mitochondria have been associated with higher enzymatic
machinery for aerobic ATP production [15,16]. Although
these organelles play a fundamental role in the energy
production necessary in endurance training and in low-
intensity exercise [2628], they may also contribute to the
greater energy availability in high-intensity exercise, such
as that investigated in the present study. This is based on
the hierarchical and ramp recruitment of the muscle fibers.
It has been found that in increasing exercise intensity, the
order of muscle fiber recruitment necessarily follows the
following order: type I (oxidative), type II (glycolytic and
oxidative), and finally type IIx (glycolytic) [29]. Therefore,
aerobic energy production (oxidative) is supplemented by
anaerobic energy production (glycolytic) as exercise
becomes more intense [30].
The second hypothesis for the muscle performance
improvement in the TLG subjects is the integration between
the aerobic and anaerobic ATP production described by
Tonkonogi and Sahlin [27]. This mechanism involves
phosphocreatine resynthesis which is dependent on the
shuttling of mitochondrial creatine in the greatest quantities
into muscle fibers with oxidative characteristics [27]. The
creatine shuttle system captures ADP and inorganic
phosphorus that result from the use of ATP in muscle
contraction, and transports them to the mitochondrial
matrix through the inner membrane organelle by means of
adenine nucleotide translocase. The ATP produced by
oxidative phosphorylation takes the same route, although
in the opposite direction, providing energy for the phos-
phocreatine resynthesis reaction in the active muscle. This
reaction is catalyzed by muscle creatine kinase. Concom-
itantly, the use of phosphocreatine energy generates muscle
creatine, ADP and inorganic phosphorus. While the ADP
and inorganic phosphorus follow the above-mentioned
path, creatine is transported to the mitochondrial intermem-
brane spaces of the muscle, and then mitochondrial creatine
kinase catalyzes the phosphocreatine resynthesis reaction,
also using ATP produced through oxidative phosphoryla-
tion. Ultimately, the phosphocreatine is transported to the
muscle contraction site, supplies the energy necessary to
continue the contractile activity and increases the ATP/ADP
ratio [27] (Fig. 5, part B).
Considering the effects of LLLT on mitochondria, and
the greater mitochondrial density and/or the enzymatic
machinery for ATP production [15,16], a bigger phospho-
creatine re-synthesis possibly must be occurs. Phosphocre-
atine resynthesis, that mainly occurs in the rest intervals
during high-intensity exercise, would be able to supply
some of the necessary energy for the next series of muscle
contractions, by providing the resynthesis of the ATP used
during session training or during maximal CKC and OKC
tests.
The third hypothesis for the muscle performance
improvement on the TLG subjects is the removal and
oxidation of lactic acid produced anaerobically during
exercise, because metabolic acidosis may induce muscle
fatigue [31,32]. Lactic acid formation in the cytosol of
muscle fibers is due to the reduction of the pyruvate to
lactate, which is catalyzed by cytosolic lactate dehydroge-
nase, and occurs mainly in anaerobic and strength exer-
cises. Next, lactate is transported to the mitochondrial
matrix via monocarboxylic acid transporters and, by means
of the NAD
+
and mitochondrial lactate dehydrogenase, is
oxidized to pyruvate. The reduced NAD (NADH) is
oxidized in the electron transport chain and provides the
necessary electrons and protons for the aerobic production
of ATP. The pyruvate in turn is oxidized to acetyl-CoA and,
in the Krebs cycle, it continues to be oxidized to produce
ATP aerobically through the electron transport chain [31,
32] (Fig. 5, part C).
Regarding the thigh perimetry results in the TLG, TG
and CG subjects, only the TLG and TG subjects showed a
significant increase in thigh perimeter after the training
program. However, the change in thigh perimeter was not
significantly different among all groups when compared
with their the mean and variances. With regard to the
percentage changes in thigh perimeter, TLG and TG
subjects showed a greater increase than the CG subjects
(see Table 1).
Numerous studies have shown increases in cross-
sectional area of muscle tissue following physical strength
training (for review see references [2,8,23]). A hypothesis
that could explain this physiological adaptation to strength
training is the association between the degree of muscle
injury and the possible greater activation of muscle satellite
cells, i.e. situations where microdamage occurring in the
muscle structure needs repair [3335]. Microdamage
stimulates mononuclear inflammatory cells (neutrophils
and macrophages), attracts satellite cells to the injury site
through chemotactic mechanisms and activates their prolif-
eration and differentiation through molecular mechanisms
[3638]. After cell differentiation, satellite cells are called
myotubes and can fuse with damaged muscle fibers, or
originate new contractile proteins [3638]. In this process,
LLLT seems to modulate satellite cell metabolism, thus
directly influencing muscle tissue regeneration [3941].
We suggest that future work should investigate the
possible action of LLLT on gene expression in humans.
The main genes that specifically encode transcription
factors for satellite cells in the quiescent state include
356 Lasers Med Sci (2011) 26:349358
Author's personal copy
Pax7 (paired box 7) and c-met (hepatocyte growth factor
receptor), and in the activated (proliferative) state for
myoblast formation include Myf-5 (myogenic factor 5),
and for myoblast differentiation into myotubes include
myogenin (myogenic factor 4), MyoD (myogenic differen-
tiation) and MRF4 (muscle-specific regulatory factor 4),
which is known as Myf-6 (myogenic factor 6) [3638]. In
addition, the gene for expression of myostatin (GDF-8)
may be modulated by LLLT, since this gene is a major
atrophy marker and acts against the process of muscle
regeneration, leading to an inhibition of satellite cell
proliferation and less hypertrophy [36]. Furthermore, in the
context of gene expression, LLLT could alter the expression of
genes for muscular hypertrophy, such as mTOR (mechanistic
target of rapamycin) and/or the genes responsible for
mitochondrial biogenesis, including NRF-1, NRF-2 (nuclear
respiratory factor 1 and 2), Tfam (transcription factor A,
mitochondrial) and PCG-1α(peroxisome proliferator-
activated receptor gamma, coactivator 1 alpha) [42,43].
Conclusion
The results of this study suggest that strength training
combined with LLLT may be superior to strength training
only. We emphasize that care is needed in generalizing the
results. Further studies, especially those involving LLLT
and gene expression, are necessary to elucidate the
interaction between laser radiation and the molecular
mechanisms of recovery and muscle performance.
Acknowledgments The authors would like to thank the Depart-
ments of Physical Therapy and Physiological Sciences of the Federal
University of São Carlos for assistance with this study, the research
subjects, and also the Conselho Nacional de Desenvolvimento
Científico e Tecnológico (CNPq) for partial funding of the research.
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... Para realização da laserterapia, a luz vermelha atinge menores profundidades de penetração, enquanto a infravermelha atinge maiores profundidades corpóreas. Os efeitos das tecnologias a laser sobre o exercício físico têm sido recentemente investigados por vários autores (LEAL JUNIOR et al., 2010;FERRARESI et al., 2011;PAOLILLO et al., 2011;TOMAZONI et al., 2019, MACHADO et al., 2020, DUTRA, et al., 2021. Desta forma, o objetivo deste estudo foi verificar os efeitos da laserterapia combinada com o exercício físico relacionado ao esporte e a saúde. ...
... Tecnologias a laser podem ser aplicadas antes (LEAL JUNIOR et al., 2010), durante (PAOLILLO et al., 2011) ou depois dos exercícios físicos (FERRARESI et al., 2011) para potencializar o rendimento esportivo e a saúde. (SAYGUN et al., 2008;CORAZZA et al., 2013). ...
... A laserterapia melhora a ativação celular, através da fotobiomodulação de várias reações bioquímicas e acelera os processos metabólicos do organismo, principalmente quando aplicada em associação com os exercícios anaeróbios ou aeróbios. No treinamento resistido, por exemplo, a partir da utilização de pesos ou faixas elásticas, observa-se o aumento de massa, força e potência muscular (FERRARESI et al., 2011, CORA-ZZA et al., 2013. Ao realizar exercícios aeróbios como caminhada, corrida, natação, ou ciclismo, há o aumento da capacidade cardiovascular e respiratória, além do aumento do metabolismo de gorduras (DUARTE et al., 2015). ...
... Structural changes include [20]. These changes allow the mitochondria to provide higher levels of respiration and ATP to the cells [21][22][23]. Furthermore, the ability of LLLT to stimulate stem cells and progenitor cells signifies that muscle satellite cells may respond well to LLLT and aid in muscle repair [24]. In a study by Macedo et al. [8], primary cultures of mdx skeletal muscle cells were irradiated only once with LLLT at a flow of 5 J/cm 2 at a wavelength of 830 nm and analyzed after 24-48 h. ...
... LLLT is added to the positive effects of aerobic exercise on mitochondria, repair the micro lesions and reactive oxygen/nitrogen metabolites can be modulated [23]. Giant and more functional mitochondria (higher enzyme activity) can provide higher levels of cellular respiration and ATP synthesis [19,29,30] during these exercises, thereby increasing the oxygen consumption [28] and reducing the muscle fatigue [22]. LLLT inhibits LDH activity even when oxygen supply is slow and ATP synthesis is insufficient in the mitochondria during physical exercise [24,29,[31][32][33]. ...
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... 13À18 Variations with regards to the types of training and the best moment to apply the intervention have been reported. 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. ...
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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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O uso de tecnologias a laser é como para as consequências da importante para a pandemia COVID-19. Além disso, a laser saúde e reabilitação, bemterapia quando combinada com a vacuoterapia ou ultrassom terapêutico parece ter seus efeitos potencializados no tratamento da dor, lesões e doenças crônicas e degenerativas. O objetivo deste estudo foi verificar os efeitos de diferentes tecnologias a laser aplicadas a saúde e reabilitação. O atual estudo trata-se de uma revisão bibliográfica realizada a partir da busca de estudos publicados até janeiro de 2021 nas bases de dados Google Scholar, Lilacs, Scielo e Pubmed. Os estudos identificados evidenciaram que o uso de tecnologias a laser resulta em vários efeitos terapêuticos e, portanto, é considerado um importante adjuvante nas ações de cuidado à população.
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Laser exposure stimulates cell proliferation and tissue repair. Branched-chain amino acids (BCAA) are widely used in sports medicine as a stimulator of anabolic processes. However, there is no evidence of the effect of combined laser and BCAA application on skeletal muscle morphometric characteristics during exercise in the training process. Purpose: to study the effect of infrared laser exposure in combination with amino acid at myosatellitocytes and skeletal muscle myocytes during swimming training. Material and methods . The experiment was conducted on 30 Wistar rats: Group 1 – intact, Group 2 – dynamic control (trainings with endurance swimming), Group 3 – trainings and BCAA, Group 4 – trainings and laser exposure at hip muscles (970 nm, 1 W, 60 s), Group 5 – combined exposure to laser and BCAA. Trainings were three times a week for 6 weeks; laser session was after each training. Samples of the bipedal thigh muscle were fixed with formalin; histological sections were stained with hematoxylin-eosin. The morphometric analysis of the digital image of objects with statistical processing by Mann – Whitney method was made. Results. Laser exposure combined with BCAA during trainings increased the nuclei area and the number of myosatellites and myocytes; it also enlarged the cross section of muscle fibers which was more pronounced if to compare with isolated laser irradiation of the muscle or BCAA. Conclusions. Infrared laser exposure in combination with branched-chain amino acids effectively stimulates regeneration due to hyperplasia and hypertrophy of skeletal muscular tissue, thus providing physiological adaptation in the training process.
Article
Background Photobiomodulation (PBM) improves motor performance despite doubts whether it occurs immediately or late after a single dose. We evaluated the effect of a cluster PMB (laser+LED) single dose on muscle fatigue recovery in young sedentary adults, both immediately and in the short term (period between 24 to 48 h) after the fatiguing event. Methods Randomized clinical trial with 60 volunteers randomized in 5 groups (n=12 in each): control/(CG); placebo/(SG); PBM in knee extensor/(KE_G); plantar-flexor/(PF_G); knee extensor+plantar-flexor/(KE+FP_G). Before the intervention (pre) a fatiguing event (FE) was applied, which consisted in going up and down one step until exhaustion. Repetition number (RN) and time to exhaustion (TTE) were recorded. Then each group received its respective intervention and immediately after that, the FE was performed again (immediate post). In the period between 24 to 48 h after irradiation, a new FE was performed (late post). In addition to the comparative statistics, complementary metrics (if the mean difference [Diff] between the comparison pairs was higher or lower than minimum detectable change [MDC] and effect size [ES]) were calculated. Results Through the integrated analysis of inferential statistics and complementary metrics, it was observed that although there was no time of evaluation effect, there was a group effect. PBM improved performance in KE+FP_G (p-value<0.05; Diff>MDC; ES=moderate) and PF_G (p-value>0.05; but Diff>MDC; ES=moderate) regarding CG for both RN and TTE. Conclusion: A PBM single dose irradiation improves motor performance and there is specificity of the irradiated muscle group, although it does not depend on the moment.
Article
Background and purpose: Physical and therapeutic strategies to maintain and rehabilitate skeletal muscle mass, strength, and postural balance are clinically relevant to improve the health, well-being, and quality of life of older adults. The purpose of this study was to investigate the effects of photobiomodulation (PBM)/laser therapy combined with a resistance training (RT) program on quadriceps hypertrophy and strength, and postural balance in older women. Methods: In a randomized, triple-blinded, placebo-controlled design, twenty-two older women (age 66.6 ± 5.2 years) were engaged in a supervised 10-wk RT program (2 times per week) involving unilateral leg extension exercise, in which each leg of the same participant was randomly assigned to receive active (λ = 808 nm, optical output = 100 mW, total energy = 42 J) or placebo laser PBM immediately before the RT sessions. Maximal dynamic strength by unilateral knee extension 1-repetition maximum (1RM), muscle hypertrophy by vastus lateralis muscle thickness, and postural balance by one-legged stance test on a force platform were assessed before and after the training program. Results: Significance statistical analysis revealed a similar improvement (time P = .003) from pre- to posttraining for muscle hypertrophy and strength, and postural balance between active and placebo laser conditions. However, clinical interpretation for muscle hypertrophy showed a moderate effect (effect size [ES] = 0.58) for the active laser and a small effect (ES = 0.38) for the placebo laser. Clinical difference was not noticed between conditions for other analyzed variables. Conclusions: These findings indicate that RT alone can be clinically important for counteracting the deleterious effects of aging on muscle size, strength, and balance, and that applying laser PBM therapy before the RT sessions may further improve gains in muscle hypertrophy.
Article
This study evaluated the effect of photobiomodulation therapy (PBMt) before or after a high-intensity resistance exercise (RE) session on muscle oxidative stress. Female Wistar rats were assigned to one of the following groups: Sham (non-exercised, undergoing placebo-PBMt); NLRE (exercised, undergoing placebo-PBMt); PBMt + RE (pre-exercise PBMt); RE + PBMt (post-exercise PBMt). The RE comprised four climbs bearing the maximum load with a 2 min rest between each climb. An 830-nm aluminum gallium arsenide diode laser (100 mW; 0.028 cm2; 3.57 mW/cm2; 142.8 J/cm2; 4 J; Photon Laser III, DMC, São Paulo, Brazil) was applied 60 s before or after RE in gastrocnemius muscles. Analyses were performed at 24 h after RE: lipoperoxidation using malondialdehyde (MDA) and protein oxidation (OP) on Western blot. Superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activity were spectrophotometrically assessed. Nitric oxide (NO) level was determined by the Griess reaction. The MDA and OP levels were significantly higher in the NLRE group. Increased OP was prevented in all PBMt groups; however, increased MDA was prevented only in the RE + PBMT group. The RE + PBMt group had higher SOD activity compared to all other groups. A higher GPx activity was observed only in the PBMT + RE compared to Sham group, and CAT activity was reduced by RE, without PBMt effect. NO levels were unchanged with RE or PBMt. Therefore, PBMt application after a RE section has a more potent antioxidant effect than previous PBMt. Rats submitted to post-RE PBMt illustrated prevention of increased lipoperoxidation and protein oxidation as well as increased SOD activity.Graphic abstract The photobiomodulation can attenuate oxidative stress induced by resistance exercise. A more evident benefit shows to be obtained with the application after exercise, in which it has increased the activity of superoxide dismustase.
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The purpose of this study was twofold: determine which isokinetic determinants correlated best with an isotonic one-repetition maximum (1-RM) and to generate, based on these determinants a formula that will allow clinicians to utilize isokinetic testing to predict an isotonic 1-RM. Fifty female subjects, ranging from 18-35 years of age, participated in this study. Strength measurements using a Cybex II isokinetic dynamometer (peak torque, average peak torque, peak torque:body weight, work per repetition, and total work) and a Cybex isotonic knee extension machine were performed. The subject's height and body weight were recorded. Through linear regression analysis the variables peak torque and body weight were determined to be the best predictors of an isotonic 1-RM. These variables were incorporated in the following formula: Predicted 1-RM = 21.38 + (0.24 x Peak Torque) + (0.18 x Body Weight) which may used utilized by clinicians to predict an isotonic 1-RM.
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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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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.
Article
Low energy laser irradiation (LELI) has been shown to promote skeletal muscle cell activation and proliferation in primary cultures of satellite cells as well as in myogenic cell lines. Here, we have extended these studies to isolated myofibers. These constitute the minimum viable functional unit of the skeletal muscle, thus providing a close model of in vivo regeneration of muscle tissue. We show that LELI stimulates cell cycle entry and the accumulation of satellite cells around isolated single fibers grown under serum-free conditions and that these effects act synergistically with the addition of serum. Moreover, for the first time we show that LELI promotes the survival of fibers and their adjacent cells, as well as cultured myogenic cells, under serum-free conditions that normally lead to apoptosis. In both systems, expression of the anti-apoptotic protein Bcl-2 was markedly increased, whereas expression of the pro-apoptotic protein BAX was reduced. In culture, these changes were accompanied by a reduction in the expression of p53 and the cyclin-dependent kinase inhibitor p21, reflecting the small decrease in viable cells 24 hours after irradiation. These findings implicate regulation of these factors as part of the protective role of LELI against apoptosis. Taken together, our findings are of critical importance in attempts to improve muscle regeneration following injury.
Article
High-resistance strength training (HRST) is one of the most widely practiced forms of physical activity, which is used to enhance athletic performance, augment musculo-skeletal health and alter body aesthetics. Chronic exposure to this type of activity produces marked increases in muscular strength, which are attributed to a range of neurological and morphological adaptations. This review assesses the evidence for these adaptations, their interplay and contribution to enhanced strength and the methodologies employed. The primary morphological adaptations involve an increase in the cross-sectional area of the whole muscle and individual muscle fibres, which is due to an increase in myofibrillar size and number. Satellite cells are activated in the very early stages of training; their proliferation and later fusion with existing fibres appears to be intimately involved in the hypertrophy response. Other possible morphological adaptations include hyperplasia, changes in fibre type, muscle architecture, myofilament density and the structure of connective tissue and tendons. Indirect evidence for neurological adaptations, which encompasses learning and coordination, comes from the specificity of the training adaptation, transfer of unilateral training to the contralateral limb and imagined contractions. The apparent rise in whole-muscle specific tension has been primarily used as evidence for neurological adaptations; however, morphological factors (e.g. preferential hypertrophy of type 2 fibres, increased angle of fibre pennation, increase in radiological density) are also likely to contribute to this phenomenon. Changes in inter-muscular coordination appear critical. Adaptations in agonist muscle activation, as assessed by electromyography, tetanic stimulation and the twitch interpolation technique, suggest small, but significant increases. Enhanced firing frequency and spinal reflexes most likely explain this improvement, although there is contrary evidence suggesting no change in cortical or corticospinal excitability. The gains in strength with HRST are undoubtedly due to a wide combination of neurological and morphological factors. Whilst the neurological factors may make their greatest contribution during the early stages of a training programme, hypertrophic processes also commence at the onset of training.
Article
Current information and evidence indicate that for most activities free weight training can produce superior results compared to training with machines, particularly when the free weight training involves complex, multi‐joint exercises. A number of reasons can account for the superiority of free weights; the major factor deals with mechanical specificity. Mechanical specificity is concerned with appropriate movement patterns, force application and velocity of movement. Considering the available evidence that adherence to the concept of specificity of exercise and training can result in a greater transfer of training effect then free weights should produce a more effective training transfer. Therefore, the majority of resistance exercises making up a training programme should include of free weight exercises with emphasis on mechanical specificity (i.e. large muscle mass exercises, appropriate velocity, contraction type etc.). Generally, machines should be used as an adjunct to free weight training and, depending upon the sport, can be used to a greater or lesser extent during various phases of the training period (preparation, pre‐competition, competition).
Article
SUMMARY In order to stimulate further adaptation toward specific training goals, progressive resistance training (RT) protocols are necessary. The optimal characteristics of strength-specific programs include the use of concentric (CON), eccentric (ECC), and isometric muscle actions and the performance of bilateral and unilateral single- and multiple-joint exercises. In addition, it is recommended that strength programs sequence exercises to optimize the preservation of exercise intensity (large before small muscle group exercises, multiple-joint exercises before single-joint exercises, and higher-intensity before lower-intensity exercises). For novice (untrained individuals with no RT experience or who have not trained for several years) training, it is recommended that loads correspond to a repetition range of an 8-12 repetition maximum (RM). For intermediate (individuals with approximately 6 months of consistent RT experience) to advanced (individuals with years of RT experience) training, it is recommended that individuals use a wider loading range from 1 to 12 RM in a periodized fashion with eventual emphasis on heavy loading (1-6 RM) using 3- to 5-min rest periods between sets performed at a moderate contraction velocity (1-2 s CON; 1-2 s ECC). When training at a specific RM load, it is recommended that 2-10% increase in load be applied when the individual can perform the current workload for one to two repetitions over the desired number. The recommendation for training frequency is 2-3 dIwkj1 for novice training, 3-4 dIwkj1 for intermediate training, and 4-5 dIwkj1 for advanced training. Similar program designs are recom- mended for hypertrophy training with respect to exercise selection and frequency. For loading, it is recommended that loads corresponding to 1-12 RM be used in periodized fashion with emphasis on the 6-12 RM zone using 1- to 2-min rest periods between sets at a moderate velocity. Higher volume, multiple-set programs are recommended for maximizing hypertrophy. Progression in power training entails two general loading strategies: 1) strength training and 2) use of light loads (0-60% of 1 RM for lower body exercises; 30-60% of 1 RM for upper body exercises) performed at a fast contraction velocity with 3-5 min of rest between sets for multiple sets per exercise (three to five sets). It is also recommended that emphasis be placed on multiple-joint exercises especially those involving the total body. For local muscular endurance training, it is recommended that light to moderate loads (40-60% of 1 RM) be performed for high repetitions (915) using short rest periods (G90 s). In the interpretation of this position stand as with prior ones, recommendations should be applied in context and should be contingent upon an individual's target goals, physical capacity, and training