Effects of low-level laser therapy (LLLT) in the development of exercise-induced skeletal muscle fatigue and changes in biochemical markers related to postexercise recovery

Near-infrared light therapy to attenuate strength loss after strenuous resistance exercise

CONTEXT

Near-infrared (NIR) light therapy is purported to act as an ergogenic aid by enhancing the contractile function of skeletal muscle. Improving muscle function is a new avenue for research in the area of laser therapy; however, very few researchers have examined the ergogenic effects of NIR light therapy and the influence it may have on the recovery process during rehabilitation.

OBJECTIVE

To evaluate the ergogenic effect of NIR light therapy on skeletal muscle function.

DESIGN

Crossover study.

SETTING

Controlled laboratory.

PATIENTS OR OTHER PARTICIPANTS

Thirty-nine healthy men (n = 21) and women (n = 18; age = 20.0 ± 0.2 years, height = 169 ± 2 cm, mass = 68.4 ± 1.8 kg, body mass index = 23.8 ± 0.4 kg/m(2)).

INTERVENTION(S)

Each participant received active and sham treatments on the biceps brachii muscle on 2 separate days. The order of treatment was randomized. A class 4 laser with a cumulative dose of 360 J was used for the active treatment. After receiving the treatment on each day, participants completed an elbow-flexion resistance-exercise protocol.

MAIN OUTCOME MEASURE(S)

The dependent variables were elbow range of motion, muscle point tenderness, and strength (peak torque). Analysis of variance with repeated measures was used to assess changes in these measures between treatments at baseline and at follow-up, 48 hours postexercise. Additionally, immediate strength loss postexercise was compared between treatments using a paired t test.

RESULTS

Preexercise to postexercise strength loss for the active laser treatment, although small, was less than with the sham treatment (P = .05).

CONCLUSIONS

Applied to skeletal muscle before resistance exercise, NIR light therapy effectively attenuated strength loss. Therefore, NIR light therapy may be a beneficial, noninvasive modality for improving muscle function during rehabilitation after musculoskeletal injury. However, future studies using higher treatment doses are warranted.

Pre-conditioning with low-level laser (light) therapy: light before the storm

Pre-conditioning by ischemia, hyperthermia, hypothermia, hyperbaric oxygen (and numerous other modalities) is a rapidly growing area of investigation that is used in pathological conditions where tissue damage may be expected. The damage caused by surgery, heart attack, or stroke can be mitigated by pre-treating the local or distant tissue with low levels of a stress-inducing stimulus, that can induce a protective response against subsequent major damage. Low-level laser (light) therapy (LLLT) has been used for nearly 50 years to enhance tissue healing and to relieve pain, inflammation and swelling. The photons are absorbed in cytochrome(c) oxidase (unit four in the mitochondrial respiratory chain), and this enzyme activation increases electron transport, respiration, oxygen consumption and ATP production. A complex signaling cascade is initiated leading to activation of transcription factors and up- and down-regulation of numerous genes. Recently it has become apparent that LLLT can also be effective if delivered to normal cells or tissue before the actual insult or trauma, in a pre-conditioning mode. Muscles are protected, nerves feel less pain, and LLLT can protect against a subsequent heart attack. These examples point the way to wider use of LLLT as a pre-conditioning modality to prevent pain and increase healing after surgical/medical procedures and possibly to increase athletic performance.

Effect of pre-irradiation with different doses, wavelengths, and application intervals of low-level laser therapy on cytochrome c oxidase activity in intact skeletal muscle of rats

Modulation of cytochrome c oxidase activity has been pointed as a possible key mechanism for low-level laser therapy (LLLT) in unhealthy biological tissues. But recent studies by our research group with LLLT in healthy muscles before exercise found delayed skeletal muscle fatigue development and improved biochemical status in muscle tissue. Therefore, the aim of this study was to evaluate effects of different LLLT doses and wavelengths in cytochrome c oxidase activity in intact skeletal muscle. In this animal experiment, we irradiated the tibialis anterior muscle of rats with three different LLLT doses (1, 3, and 10 J) and wavelengths (660, 830, and 905 nm) with 50 mW power output. After irradiation, the analyses of cytochrome c oxidase expression by immunohistochemistry were analyzed at 5, 10, 30 min and at 1, 2, 12, and 24 h. Our results show that LLLT increased (p < 0.05) cytochrome c oxidase expression mainly with the following wavelengths and doses: 660 nm with 1 J, 830 nm with 3 J, and 905 nm with 1 J at all time points. We conclude that LLLT can increase cytochrome c oxidase activity in intact skeletal muscle and that it contributes to our understanding of how LLLT can enhance performance and protect skeletal muscles against fatigue development and tissue damage. Our findings also lead us to think that the combined use of different wavelengths at the same time can enhance LLLT effects in skeletal muscle performance and other conditions, and it can represent a therapeutic advantage in clinical settings.

Clinical efficacy of low-level laser therapy on localized canine atopic dermatitis severity score and localized pruritic visual analog score in pedal pruritus due to canine atopic dermatitis

BACKGROUND

Canine atopic dermatitis is a genetically predisposed inflammatory skin disease often requiring multimodal treatment. There is a need to find further low-risk adjunctive therapies.

HYPOTHESIS/OBJECTIVES

To evaluate the localized effect of low-level laser therapy (LLLT) on the paws of dogs with atopic dermatitis using a localized canine atopic dermatitis severity score (LCADSS) and owner localized pruritic visual analog score (LPVAS) in comparison to treatment with a placebo.

ANIMALS

Thirty client-owned dogs with symmetrical pedal pruritus due to canine atopic dermatitis.

METHODS

Dogs were randomly assigned into two groups. In each group, one paw was treated with LLLT and one paw treated with a placebo laser (comparing either both fore- or hindpaws). Treatments were administered at 4 J/cm(2) (area from carpus/tarsus to distal aspect of digit 3) three times per week for the first 2 weeks and two times per week for the second 2 weeks. Scores were assessed for each paw at weeks 0, 2, 4 and 5.

RESULTS

There were no significant differences in LCADSS or LPVAS between LLLT and placebo treatments between weeks 0 and 5 (P = 0.0856 and 0.5017, respectively). However, LCADSS and LPVAS significantly decreased from week 0 at weeks 2, 4 and 5 in both LLLT and placebo groups (P < 0.0001 for all).

CONCLUSIONS AND CLINICAL IMPORTANCE

Low-level laser therapy is not an effective localized treatment for pedal pruritus in canine atopic dermatitis.

The influence of low-level laser therapy on parameters of oxidative stress and DNA damage on muscle and plasma in rats with heart failure

In heart failure (HF), there is an imbalance between the production of reactive oxygen species and the synthesis of antioxidant enzymes, causing damage to the cardiovascular function and increased susceptibility to DNA damage. The aim of this study was to evaluate the influence of low-level laser therapy (LLLT) on parameters of oxidative stress and DNA damage in skeletal muscle and plasma of rats with HF. Wistar rats were allocated into six groups: "placebo" HF rats (P-HF, n = 9), "placebo" Sham rats (P-sham, n = 8), HF rats at a dose 3 J/cm(2) of LLLT (3 J/cm(2)-HF, n = 8), sham rats at a dose 3 J/cm(2) of LLLT (3 J/cm(2)-sham, n = 8), HF rats at a dose 21 J/cm(2) of LLLT (21 J/cm(2)-HF, n = 8) and sham rats at a dose 21 J/cm(2) of LLLT (21 J/cm(2)-sham, n = 8). Animals were submitted to a LLLT protocol for 10 days at the right gastrocnemius muscle. Comparison between groups showed a significant reduction in superoxide dismutase (SOD) activity in the 3 J/cm(2)-HF group (p = 0.03) and the 21 J/cm(2)-HF group (p = 0.01) compared to the P-HF group. 2',7'-Dihydrodichlorofluorescein (DCFH) oxidation levels showed a decrease when comparing 3 J/cm(2)-sham to P-sham (p = 0.02). The DNA damage index had a significant increase either in 21 J/cm(2)-HF or 21 J/cm(2)-sham in comparison to P-HF (p = 0.004) and P-sham (p = 0.001) and to 3 J/cm(2)-HF (p = 0.007) and 3 J/cm(2)-sham (p = 0.037), respectively. Based on this, laser therapy appears to reduce SOD activity and DCFH oxidation levels, changing the oxidative balance in the skeletal muscle of HF rats. Otherwise, high doses of LLLT seem to increase DNA damage.

Effects of pre-irradiation of low-level laser therapy with different doses and wavelengths in skeletal muscle performance, fatigue, and skeletal muscle damage induced by tetanic contractions in rats

This study aimed to evaluate the effects of low-level laser therapy (LLLT) immediately before tetanic contractions in skeletal muscle fatigue development and possible tissue damage. Male Wistar rats were divided into two control groups and nine active LLLT groups receiving one of three different laser doses (1, 3, and 10 J) with three different wavelengths (660, 830, and 905 nm) before six tetanic contractions induced by electrical stimulation. Skeletal muscle fatigue development was defined by the percentage (%) of the initial force of each contraction and time until 50 % decay of initial force, while total work was calculated for all six contractions combined. Blood and muscle samples were taken immediately after the sixth contraction. Several LLLT doses showed some positive effects on peak force and time to decay for one or more contractions, but in terms of total work, only 3 J/660 nm and 1 J/905 nm wavelengths prevented significantly (p < 0.05) the development of skeletal muscle fatigue. All doses with wavelengths of 905 nm but only the dose of 1 J with 660 nm wavelength decreased creatine kinase (CK) activity (p < 0.05). Qualitative assessment of morphology revealed lesser tissue damage in most LLLT-treated groups, with doses of 1-3 J/660 nm and 1, 3, and 10 J/905 nm providing the best results. Optimal doses of LLLT significantly delayed the development skeletal muscle performance and protected skeletal muscle tissue against damage. Our findings also demonstrate that optimal doses are partly wavelength specific and, consequently, must be differentiated to obtain optimal effects on development of skeletal muscle fatigue and tissue preservation. Our findings also lead us to think that the combined use of wavelengths at the same time can represent a therapeutic advantage in clinical settings.

Superpulsed low-level laser therapy protects skeletal muscle of mdx mice against damage, inflammation and morphological changes delaying dystrophy progression

AIM

To evaluate the effects of preventive treatment with low-level laser therapy (LLLT) on progression of dystrophy in mdx mice.

METHODS

Ten animals were randomly divided into 2 experimental groups treated with superpulsed LLLT (904 nm, 15 mW, 700 Hz, 1 J) or placebo-LLLT at one point overlying the tibialis anterior muscle (bilaterally) 5 times per week for 14 weeks (from 6th to 20th week of age). Morphological changes, creatine kinase (CK) activity and mRNA gene expression were assessed in animals at 20th week of age.

RESULTS

Animals treated with LLLT showed very few morphological changes in skeletal muscle, with less atrophy and fibrosis than animals treated with placebo-LLLT. CK was significantly lower (p=0.0203) in animals treated with LLLT (864.70 U.l-1, SEM 226.10) than placebo (1708.00 U.l-1, SEM 184.60). mRNA gene expression of inflammatory markers was significantly decreased by treatment with LLLT (p<0.05): TNF-α (placebo-control=0.51 µg/µl [SEM 0.12], - LLLT=0.048 µg/µl [SEM 0.01]), IL-1β (placebo-control=2.292 µg/µl [SEM 0.74], - LLLT=0.12 µg/µl [SEM 0.03]), IL-6 (placebo-control=3.946 µg/µl [SEM 0.98], - LLLT=0.854 µg/µl [SEM 0.33]), IL-10 (placebo-control=1.116 µg/µl [SEM 0.22], - LLLT=0.352 µg/µl [SEM 0.15]), and COX-2 (placebo-control=4.984 µg/µl [SEM 1.18], LLLT=1.470 µg/µl [SEM 0.73]).

CONCLUSION

Irradiation of superpulsed LLLT on successive days five times per week for 14 weeks decreased morphological changes, skeletal muscle damage and inflammation in mdx mice. This indicates that LLLT has potential to decrease progression of Duchenne muscular dystrophy.

What is the ideal dose and power output of low-level laser therapy (810 nm) on muscle performance and post-exercise recovery? Study protocol for a double-blind, randomized, placebo-controlled trial

Background

Recent studies involving phototherapy applied prior to exercise have demonstrated positive results regarding the attenuation of muscle fatigue and the expression of biochemical markers associated with recovery. However, a number of factors remain unknown, such as the ideal dose and application parameters, mechanisms of action and long-term effects on muscle recovery. The aims of the proposed project are to evaluate the long-term effects of low-level laser therapy on post-exercise musculoskeletal recovery and identify the best dose andapplication power/irradiation time.

Design and methods

A double-blind, randomized, placebo-controlled clinical trial with be conducted. After fulfilling the eligibility criteria, 28 high-performance athletes will be allocated to four groups of seven volunteers each. In phase 1, the laser power will be 200 mW and different doses will be tested: Group A (2 J), Group B (6 J), Group C (10 J) and Group D (0 J). In phase 2, the best dose obtained in phase 1 will be used with the same distribution of the volunteers, but with different powers: Group A (100 mW), Group B (200 mW), Group C (400 mW) and Group D (0 mW). The isokinetic test will be performed based on maximum voluntary contraction prior to the application of the laser and after the eccentric contraction protocol, which will also be performed using the isokinetic dynamometer. The following variables related to physical performance will be analyzed: peak torque/maximum voluntary contraction, delayed onset muscle soreness (algometer), biochemical markers of muscle damage, inflammation and oxidative stress.

Discussion

Our intention, is to determine optimal laser therapy application parameters capable of slowing down the physiological muscle fatigue process, reducing injuries or micro-injuries in skeletal muscle stemming from physical exertion and accelerating post-exercise muscle recovery. We believe that, unlike drug therapy, LLLT has a biphasic dose–response pattern.

Trial registration

The protocol for this study is registered with the Protocol Registry System, ClinicalTrials.gov identifier NCT01844271.

Effects of pre- or post-exercise low-level laser therapy (830 nm) on skeletal muscle fatigue and biochemical markers of recovery in humans: double-blind placebo-controlled trial

OBJECTIVES

The purpose of this study was to investigate the effect of low-level laser therapy (LLLT) before and after exercise on quadriceps muscle performance, and to evaluate the changes in serum lactate and creatine kinase (CK) levels.

METHODS

The study was randomized, double blind, and placebo controlled.

PATIENTS

A sample of 27 healthy volunteers (male soccer players) were divided into three groups: placebo, pre-fatigue laser, and post-fatigue laser. The experiment was performed in two sessions, with a 1 week interval between them. Subjects performed two sessions of stretching followed by blood collection (measurement of lactate and CK) at baseline and after fatigue of the quadriceps by leg extension. LLLT was applied to the femoral quadriceps muscle using an infrared laser device (830 nm), 0.0028 cm(2) beam area, six 60 mW diodes, energy of 0.6 J per diode (total energy to each limb 25.2 J (50.4 J total), energy density 214.28 J/cm(2), 21.42 W/cm(2) power density, 70 sec per leg. We measured the time to fatigue and number and maximum load (RM) of repetitions tolerated. Number of repetitions and time until fatigue were primary outcomes, secondary outcomes included serum lactate levels (measured before and 5, 10, and 15 min after exercise), and CK levels (measured before and 5 min after exercise).

RESULTS

The number of repetitions (p=0.8965), RM (p=0.9915), and duration of fatigue (p=0.8424) were similar among the groups. Post-fatigue laser treatment significantly decreased the serum lactate concentration relative to placebo treatment (p<0.01) and also within the group over time (after 5 min vs. after 10 and 15 min, p<0.05 both). The CK level was lower in the post-fatigue laser group (p<0.01).

CONCLUSIONS

Laser application either before or after fatigue reduced the post-fatigue concentrations of serum lactate and CK. The results were more pronounced in the post-fatigue laser group.

Effect of phototherapy (low-level laser therapy and light-emitting diode therapy) on exercise performance and markers of exercise recovery: a systematic review with meta-analysis

Recent studies have explored if phototherapy with low-level laser therapy (LLLT) or narrow-band light-emitting diode therapy (LEDT) can modulate activity-induced skeletal muscle fatigue or subsequently protect against muscle injury. We performed a systematic review with meta-analysis to investigate the effects of phototherapy applied before, during and after exercises. A literature search was performed in Pubmed/Medline database for randomized controlled trials (RCTs) published from 2000 through 2012. Trial quality was assessed with the ten-item PEDro scale. Main outcome measures were selected as: number of repetitions and time until exhaustion for muscle performance, and creatine kinase (CK) activity to evaluate risk for exercise-induced muscle damage. The literature search resulted in 16 RCTs, and three articles were excluded due to poor quality assessment scores. From 13 RCTs with acceptable methodological quality (≥6 of 10 items), 12 RCTs irradiated phototherapy before exercise, and 10 RCTs reported significant improvement for the main outcome measures related to performance. The time until exhaustion increased significantly compared to placebo by 4.12 s (95% CI 1.21-7.02, p < 0.005) and the number of repetitions increased by 5.47 (95% CI 2.35-8.59, p < 0.0006) after phototherapy. Heterogeneity in trial design and results precluded meta-analyses for biochemical markers, but a quantitative analysis showed positive results in 13 out of 16 comparisons. The most significant and consistent results were found with red or infrared wavelengths and phototherapy application before exercises, power outputs between 50 and 200 mW and doses of 5 and 6 J per point (spot). We conclude that phototherapy (with lasers and LEDs) improves muscular performance and accelerate recovery mainly when applied before exercise.

Does phototherapy enhance skeletal muscle contractile function and postexercise recovery? A systematic review

CONTEXT

Recently, researchers have shown that phototherapy administered to skeletal muscle immediately before resistance exercise can enhance contractile function, prevent exercise-induced cell damage, and improve postexercise recovery of strength and function.

OBJECTIVE

To critically evaluate original research addressing the ability of phototherapeutic devices, such as lasers and light-emitting diodes (LEDs), to enhance skeletal muscle contractile function, reduce exercise-induced muscle fatigue, and facilitate postexercise recovery.

DATA SOURCES

We searched the electronic databases PubMed, SPORTDiscus, Web of Science, Scopus, and Rehabilitation & Physical Medicine without date limitations for the following key words: laser therapy, phototherapy, fatigue, exercise, circulation, microcirculation, and photobiomodulation.

STUDY SELECTION

Eligible studies had to be original research published in English as full papers, involve human participants, and receive a minimum score of 7 out of 10 on the Physiotherapy Evidence Database (PEDro) scale.

DATA EXTRACTION

Data of interest included elapsed time to fatigue, total number of repetitions to fatigue, total work performed, maximal voluntary isometric contraction (strength), electromyographic activity, and postexercise biomarker levels. We recorded the PEDro scores, beam characteristics, and treatment variables and calculated the therapeutic outcomes and effect sizes for the data sets.

DATA SYNTHESIS

In total, 12 randomized controlled trials met the inclusion criteria. However, we excluded data from 2 studies, leaving 32 data sets from 10 studies. Twenty-four of the 32 data sets contained differences between active phototherapy and sham (placebo-control) treatment conditions for the various outcome measures. Exposing skeletal muscle to single-diode and multidiode laser or multidiode LED therapy was shown to positively affect physical performance by delaying the onset of fatigue, reducing the fatigue response, improving postexercise recovery, and protecting cells from exercise-induced damage.

CONCLUSIONS

Phototherapy administered before resistance exercise consistently has been found to provide ergogenic and prophylactic benefits to skeletal muscle.

What is the best treatment to decrease pro-inflammatory cytokine release in acute skeletal muscle injury induced by trauma in rats: low-level laser therapy, diclofenac, or cryotherapy?

Currently, treatment of muscle injuries represents a challenge in clinical practice. In acute phase, the most employed therapies are cryotherapy and nonsteroidal anti-inflammatory drugs. In the last years, low-level laser therapy (LLLT) has becoming a promising therapeutic agent; however, its effects are not fully known. The aim of this study was to analyze the effects of sodium diclofenac (topical application), cryotherapy, and LLLT on pro-inflammatory cytokine levels after a controlled model of muscle injury. For such, we performed a single trauma in tibialis anterior muscle of rats. After 1 h, animals were treated with sodium diclofenac (11.6 mg/g of solution), cryotherapy (20 min), or LLLT (904 nm; superpulsed; 700 Hz; 60 mW mean output power; 1.67 W/cm(2); 1, 3, 6 or 9 J; 17, 50, 100 or 150 s). Assessment of interleukin-1β and interleukin-6 (IL-1β and IL-6) and tumor necrosis factor-alpha (TNF-α) levels was performed at 6 h after trauma employing enzyme-linked immunosorbent assay method. LLLT with 1 J dose significantly decreased (p < 0.05) IL-1β, IL-6, and TNF-α levels compared to non-treated injured group as well as diclofenac and cryotherapy groups. On the other hand, treatment with diclofenac and cryotherapy does not decrease pro-inflammatory cytokine levels compared to the non-treated injured group. Therefore, we can conclude that 904 nm LLLT with 1 J dose has better effects than topical application of diclofenac or cryotherapy in acute inflammatory phase after muscle trauma.

Neurological and psychological applications of transcranial lasers and LEDs

Transcranial brain stimulation with low-level light/laser therapy (LLLT) is the use of directional low-power and high-fluency monochromatic or quasimonochromatic light from lasers or LEDs in the red-to-near-infrared wavelengths to modulate a neurobiological function or induce a neurotherapeutic effect in a nondestructive and non-thermal manner. The mechanism of action of LLLT is based on photon energy absorption by cytochrome oxidase, the terminal enzyme in the mitochondrial respiratory chain. Cytochrome oxidase has a key role in neuronal physiology, as it serves as an interface between oxidative energy metabolism and cell survival signaling pathways. Cytochrome oxidase is an ideal target for cognitive enhancement, as its expression reflects the changes in metabolic capacity underlying higher-order brain functions. This review provides an update on new findings on the neurotherapeutic applications of LLLT. The photochemical mechanisms supporting its cognitive-enhancing and brain-stimulatory effects in animal models and humans are discussed. LLLT is a potential non-invasive treatment for cognitive impairment and other deficits associated with chronic neurological conditions, such as large vessel and lacunar hypoperfusion or neurodegeneration. Brain photobiomodulation with LLLT is paralleled by pharmacological effects of low-dose USP methylene blue, a non-photic electron donor with the ability to stimulate cytochrome oxidase activity, redox and free radical processes. Both interventions provide neuroprotection and cognitive enhancement by facilitating mitochondrial respiration, with hormetic dose-response effects and brain region activational specificity. This evidence supports enhancement of mitochondrial respiratory function as a generalizable therapeutic principle relevant to highly adaptable systems that are exquisitely sensitive to energy availability such as the nervous system.

Acute effects of light emitting diodes therapy (LEDT) in muscle function during isometric exercise in patients with chronic obstructive pulmonary disease: preliminary results of a randomized controlled trial

Patients with chronic obstructive pulmonary disease (COPD) are susceptible to early muscle fatigue. Light-emitting diodes therapy (LEDT) has been used to minimize muscle fatigue in athletes and healthy subjects. The aim of this study is to investigate the acute effects of LEDT on muscle fatigue and perception of effort in patients with COPD during isometric endurance test of the quadriceps femoris (QF). Ten patients (VEF₁ 50 ± 13% of predicted) underwent a single LEDT and sham application, 48 h apart, in a randomized crossover design. The LEDT and sham were applied in three localized areas of the QF (rectus femoris, vastus lateralis, and vastus medialis). Before and after exposure to LEDT and sham, the patients performed an isometric endurance test (60 % of the maximum voluntary isometric contraction), until the limit of tolerance concomitant to surface electromyography recording (median frequency as mean outcome). The slope obtained from linear regression analysis of the median frequency (MF) over endurance time was also used as an endurance index. Endurance time increased significantly after exposure to LEDT (from 26 ± 2 to 53 ± 5 s) as compared to sham (from 23 ± 3 to 30 ± 4 s) (F = 64, P = 0.0001). A greater decline in MF was observed during isometric endurance test after sham, compared to LEDT (F = 14.6, P = 0.004). The slope of the MF over time was lower post-LEDT compared to post-sham (-0.7 ± 0.3 vs. -1.5 ± 0.8; P = 0.004). The dyspnea score corrected for endurance time was lower post-LEDT (P = 0.008) but similar for fatigue both post-LEDT and post-sham. A single application of LEDT minimizes muscle fatigue and increases isometric endurance time.

Effects of light-emitting diodes on muscle fatigue and exercise tolerance in patients with COPD: study protocol for a randomized controlled trial

BACKGROUND

Light-emitting diodes (LED) have been used to minimize muscle fatigue in athletes and healthy subjects. Patients with chronic obstructive pulmonary disease (COPD) are susceptible to early muscle fatigue.

OBJECTIVE

The objective of this study is to investigate the acute effects of LED on muscle function, exercise capacity and cardiorespiratory responses during isometric and dynamic exercise in patients with COPD.

METHODS

This study will assess 30 patients with moderate to severe obstruction (forced expiratory volume-one second,FEV1 ≤70% predicted). Isometric and dynamic protocols will be conducted in two visits each, for a total of four visits a week apart. First, venous blood will be taken from the patients. The isometric protocol will start with the determination of the maximum voluntary isometric contraction (MIVC) to determine the workload (60% of MIVC) for the isometric endurance test (IET). Patients will be randomized to receive either the placebo or LED application (each point will be irradiated for 30 s and the energy received at each point will be 41.7 J). Immediately after finishing this procedure, the patients will carry out the IET until the limit of tolerance or until a 20% fall of strength is observed. After the test, another blood draw will be taken. In another visit (one week later), the same order of procedures will be performed, except with the opposite (LED or placebo). For the dynamic endurance test (DET), the same procedures described above will be followed, except with 75% of the maximal workload obtained from the incremental cycle ergometer test used instead of the IET. The electromyography will be recorded during the isometric and dynamic protocols. Differences in muscle function, exercise capacity and cardiorespiratory responses between the LED and placebo applications will be analyzed. The therapeutic effects of LED could minimize muscle fatigue in patients with COPD by increasing exercise tolerance.

TRIAL REGISTRATION

TRIAL REGISTRATION NUMBER

NCT01448564.

Recovery after high-intensity intermittent exercise in elite soccer players using VEINOPLUS sport technology for blood-flow stimulation

CONTEXT

Electric muscle stimulation has been suggested to enhance recovery after exhaustive exercise by inducing an increase in blood flow to the stimulated area. Previous studies have failed to support this hypothesis. We hypothesized that the lack of effect shown in previous studies could be attributed to the technique or device used.

OBJECTIVE

To investigate the effectiveness of a recovery intervention using an electric blood-flow stimulator on anaerobic performance and muscle damage in professional soccer players after intermittent, exhaustive exercise.

DESIGN

Randomized controlled clinical trial.

SETTING

National Institute of Sport, Expertise, and Performance (INSEP).

PATIENTS OR OTHER PARTICIPANTS

Twenty-six healthy professional male soccer players.

INTERVENTION(S)

The athletes performed an intermittent fatiguing exercise followed by a 1-hour recovery period, either passive or using an electric blood-flow stimulator (VEINOPLUS). Participants were randomly assigned to a group before the experiment started.

MAIN OUTCOME MEASURES(S)

Performances during a 30-second all-out exercise test, maximal vertical countermovement jump, and maximal voluntary contraction of the knee extensor muscles were measured at rest, immediately after the exercise, and 1 hour and 24 hours later. Muscle enzymes indicating muscle damage (creatine kinase, lactate dehydrogenase) and hematologic profiles were analyzed before and 1 hour and 24 hours after the intermittent fatigue exercise.

RESULTS

The electric-stimulation group had better 30-second all-out performances at 1 hour after exercise (P = .03) in comparison with the passive-recovery group. However, no differences were observed in muscle damage markers, maximal vertical countermovement jump, or maximal voluntary contraction between groups (P > .05).

CONCLUSIONS

Compared with passive recovery, electric stimulation using this blood-flow stimulator improved anaerobic performance at 1 hour postintervention. No changes in muscle damage markers or maximal voluntary contraction were detected. These responses may be considered beneficial for athletes engaged in sports with successive rounds interspersed with short, passive recovery periods.

Effect of low-level laser therapy on pain, quality of life and sleep in patients with fibromyalgia: study protocol for a double-blinded randomized controlled trial

Background

Low-level laser therapy (LLLT) has been widely used as adjuvant strategy for treatment of musculoskeletal disorders. The light-tissue interaction (photobiostimulation) promotes analgesic and anti-inflammatory effects and improves tissue healing, which could justify the recommendation of this therapy for patients with fibromyalgia, leading to an improvement in pain and possibly minimizing social impact related to this disease. The present study proposes to evaluate the effect of LLLT on tender points in patients with fibromyalgia, correlating this outcome with quality of life and sleep.

Methods/design

One hundred and twenty patients with fibromyalgia will be treated at the Integrated Health Center and the Sleep Laboratory of the Post Graduate Program in Rehabilitation Sciences of the Nove de Julho University located in the city of Sao Paulo, Brazil. After fulfilling the eligibility criteria, a clinical evaluation and assessments of pain and sleep quality will be carried out and self-administered quality of life questionnaires will be applied. The 120 volunteers will be randomly allocated to an intervention group (LLLT, n = 60) or control group (CLLLT, n = 60). Patients from both groups will be treated three times per week for four weeks, totaling twelve sessions. However, only the LLLT group will receive an energy dose of 6 J per tender point. A standardized 50-minute exercise program will be performed after the laser application. The patients will be evaluated regarding the primary outcome (pain) using the following instruments: visual analog scale, McGill Pain Questionnaire and pressure algometry. The secondary outcome (quality of life and sleep) will be assessed with the following instruments: Medical Outcomes Study 36-item Short-Form Health Survey, Fibromyalgia Impact Questionnaire, Berlin Questionnaire, Epworth Sleepiness Scale and polysomnography. ANOVA test with repeated measurements for the time factor will be performed to test between-groups differences (followed by the Tukey-Kramer post hoc test), and a paired t test will be performed to test within-group differences. The level of significance for the statistical analysis will be set at 5% (P ≤0.05).

Trial registration

The protocol for this study is registered with the Brazilian Registry of Clinical Trials – ReBEC (RBR-42gkzt)

Effect of simvastatin on passive strain-induced skeletal muscle injury in rats

INTRODUCTION

HMG-CoA reductase inhibitors are the most frequently prescribed drugs for treatment of lipid imbalance, but they have side effects, such as myopathy. Our aim was to assess the effect of simvastatin on the inflammatory process induced by skeletal muscle injury.

METHODS

Rats were divided into experimental groups [control group, simvastatin (20 mg/kg) group, group treated with simvastatin (20 mg/kg) and subjected to injury, and group subjected to injury only]. Histological analysis and analyses of creatine kinase activity and C-reactive protein were performed.

RESULTS

Animals treated with simvastatin exhibited significantly greater morphological and structural skeletal muscle damage in comparison to the control group and injured animals without treatment.

CONCLUSIONS

Although simvastatin has a small anti-inflammatory effect in the early stage after a muscle strain injury, the overall picture is negative, as simvastatin increases the extent of damage to muscle morphology. Further studies are needed.

Low-level laser therapy (808 nm) reduces inflammatory response and oxidative stress in rat tibialis anterior muscle after cryolesion

BACKGROUND AND OBJECTIVE

Muscle regeneration is a complex phenomenon, involving coordinated activation of several cellular responses. During this process, oxidative stress and consequent tissue damage occur with a severity that may depend on the intensity and duration of the inflammatory response. Among the therapeutic approaches to attenuate inflammation and increase tissue repair, low-level laser therapy (LLLT) may be a safe and effective clinical procedure. The aim of this study was to evaluate the effects of LLLT on oxidative/nitrative stress and inflammatory mediators produced during a cryolesion of the tibialis anterior (TA) muscle in rats.

MATERIAL AND METHODS

Sixty Wistar rats were randomly divided into three groups (n = 20): control (BC), injured TA muscle without LLLT (IC), injured TA muscle submitted to LLLT (IRI). The injured region was irradiated daily for 4 consecutive days, starting immediately after the lesion using a AlGaAs laser (continuous wave, 808 nm, tip area of 0.00785 cm(2) , power 30 mW, application time 47 seconds, fluence 180 J/cm(2) ; 3.8 mW/cm(2) ; and total energy 1.4 J). The animals were sacrificed on the fourth day after injury.

RESULTS

LLLT reduced oxidative and nitrative stress in injured muscle, decreased lipid peroxidation, nitrotyrosine formation and NO production, probably due to reduction in iNOS protein expression. Moreover, LLLT increased SOD gene expression, and decreased the inflammatory response as measured by gene expression of NF-kβ and COX-2 and by TNF-α and IL-1β concentration.

CONCLUSION

These results suggest that LLLT could be an effective therapeutic approach to modulate oxidative and nitrative stress and to reduce inflammation in injured muscle.

The effects of light emitting diode therapy following high intensity exercise

OBJECTIVE

To determine the effects of light emitting diode therapy (LEDT) irradiation on blood lactate concentration ([La]) clearance, peak power output and fatigue index (FI) following high intensity fatiguing exercise.

DESIGN

Single-blinded randomised cross-over placebo controlled trial.

SETTING

University College Dublin, Institute for Sport and Health, Human performance laboratory.

PARTICIPANTS

Eighteen healthy male athletes were recruited from field-based sports (including soccer, hockey and rugby union) and participated in the present study.

MAIN OUTCOME MEASURES

Dependent variables were the peak power output elicited during the Wingate Anaerobic Test (WAnT), FI and [La] before and after each exercise. WAnT performance was measured prior to high intensity fatiguing exercise (Yo-Yo IR2), prior to LEDT or placebo, and following LEDT or placebo. [La] was measured at baseline, immediately after the Yo-Yo IR2, and in the 3rd, 9th, and 15th min following LEDT or placebo condition.

RESULTS

No significant group by treatment interactions were observed for any outcome measures (P > 0.05).

CONCLUSION

We conclude that LEDT irradiation applied following high intensity exercise was not effective and has no immediate effect on [La] clearance, peak power and FI, and thus has no significant effect on muscle recovery in athletes at the intensity and irradiation parameters used in the present study. Further research using different parameters is required to determine how LEDT may contribute to post-exercise recovery.

Low-level laser (light) therapy (LLLT) on muscle tissue: performance, fatigue and repair benefited by the power of light

The use of low level laser (light) therapy (LLLT) has recently expanded to cover areas of medicine that were not previously thought of as the usual applications such as wound healing and inflammatory orthopedic conditions. One of these novel application areas is LLLT for muscle fatigue and muscle injury. Since it is becoming agreed that mitochondria are the principal photoacceptors present inside cells, and it is known that muscle cells are exceptionally rich in mitochondria, this suggests that LLLT should be highly beneficial in muscle injuries. The ability of LLLT to stimulate stem cells and progenitor cells means that muscle satellite cells may respond well to LLLT and help muscle repair. Furthermore the ability of LLLT to reduce inflammation and lessen oxidative stress is also beneficial in cases of muscle fatigue and injury. This review covers the literature relating to LLLT and muscles in both preclinical animal experiments and human clinical studies. Athletes, people with injured muscles, and patients with Duchenne muscular dystrophy may all benefit.

Infrared (810 nm) low-level laser therapy in experimental model of strain-induced skeletal muscle injury in rats: effects on functional outcomes

Muscle strains are among the most prevalent causes for athletes' absence from sport activities. Low-level laser therapy (LLLT) has recently emerged as a potential contender to nonsteroidal anti-inflammatory drugs in muscle strain treatment. In this work we investigated effects of LLLT and diclofenac on functional outcomes in the acute stage after muscle strain injury in rats. Muscle strain was induced by overloading the tibialis anterior muscle of rats during anesthesia. The injured groups received either no treatment, or a single treatment with diclofenac 30 min prior to injury, or LLLT (810 nm, 100 mW) with doses of 1, 3, 6 or 9 J, at 1 h after injury. Functional outcome measures included a walking index and assessment of electrically induced muscle performance. All treatments (except 9 J LLLT) significantly improved the walking index 12 h postinjury compared with the untreated group. The 3 J group also showed a significantly better walking index than the drug group. All treatments significantly improved muscle performance at 6 and 12 h. LLLT dose of 3 J was as effective as the pharmacological agent in improving functional outcomes in the early phase after a muscle strain injury in rats.

The physiological effects of low-intensity neuromuscular electrical stimulation (NMES) on short-term recovery from supra-maximal exercise bouts in male triathletes

This study investigated the acute effects of NMES on blood lactate (BLa) and performance parameters in trained male triathletes. On three separate days, 13 trained male triathletes performed six 30 s Wingate tests (30 WanT) on a cycle ergometer. Each session consisted of performing 3 × 30 WanT (bouts 1-3) followed by a randomly assigned 30 min recovery intervention of either: (i) passive (seated), (ii) active (cycling at 30% VO(2 max)) or (iii) NMES (1 Hz/500 μs-ON:OFF 2:6 s). The 3 × 30 WanT bouts were then repeated (bouts 4-6) and compared to bouts 1-3 for peak power (PP), mean power (MP) and fatigue index (FI). BLa and heart rate (HR) were recorded at designated time points throughout. Data were analyzed using repeated measures ANOVA with Tukey's honestly significant difference post hoc test. BLa decreased significantly faster during the active recovery intervention (P < 0.001), however, there were no significant differences between interventions for PP (P = 0.217), MP (P = 0.477) and FI (P = 0.234) when the post intervention bouts (4-6) where compared to the pre intervention bouts (1-3). NMES during recovery was not more effective than active or passive recovery for improving subsequent performance. Despite BLa clearing at a significantly faster rate for the active recovery intervention, PP, MP or FI did not improve significantly compared to NMES and passive. In conclusion, NMES does not appear to be more effective than traditional methods for enhancing short-term recovery from supra-maximal exercise bouts in trained male triathletes.

Low-level laser therapy improves skeletal muscle performance, decreases skeletal muscle damage and modulates mRNA expression of COX-1 and COX-2 in a dose-dependent manner

We tested if modulation in mRNA expression of cyclooxygenase isoforms (COX-1 and COX-2) can be related to protective effects of phototherapy in skeletal muscle. Thirty male Wistar rats were divided into five groups receiving either one of four laser doses (0.1, 0.3, 1.0 and 3.0 J) or a no-treatment control group. Laser irradiation (904 nm, 15 mW average power) was performed immediately before the first contraction for treated groups. Electrical stimulation was used to induce six tetanic tibial anterior muscle contractions. Immediately after sixth contraction, blood samples were collected to evaluate creatine kinase activity and muscles were dissected and frozen in liquid nitrogen to evaluate mRNA expression of COX-1 and COX-2. The 1.0 and 3.0 J groups showed significant enhancement (P < 0.01) in total work performed in six tetanic contractions compared with control group. All laser groups, except the 3.0 J group, presented significantly lower post-exercise CK activity than control group. Additionally, 1.0 J group showed increased COX-1 and decreased COX-2 mRNA expression compared with control group and 0.1, 0.3 and 3.0 J laser groups (P < 0.01). We conclude that pre-exercise infrared laser irradiation with dose of 1.0 J enhances skeletal muscle performance and decreases post-exercise skeletal muscle damage and inflammation.

Red (660 nm) and infrared (830 nm) low-level laser therapy in skeletal muscle fatigue in humans: what is better?

In animal and clinical trials low-level laser therapy (LLLT) using red, infrared and mixed wavelengths has been shown to delay the development of skeletal muscle fatigue. However, the parameters employed in these studies do not allow a conclusion as to which wavelength range is better in delaying the development of skeletal muscle fatigue. With this perspective in mind, we compared the effects of red and infrared LLLT on skeletal muscle fatigue. A randomized double-blind placebo-controlled crossover trial was performed in ten healthy male volunteers. They were treated with active red LLLT, active infrared LLLT (660 or 830 nm, 50 mW, 17.85 W/cm², 100 s irradiation per point, 5 J, 1,785 J/cm² at each point irradiated, total 20 J irradiated per muscle) or an identical placebo LLLT at four points of the biceps brachii muscle for 3 min before exercise (voluntary isometric elbow flexion for 60 s). The mean peak force was significantly greater (p < 0.05) following red (12.14%) and infrared LLLT (14.49%) than following placebo LLLT, and the mean average force was also significantly greater (p < 0.05) following red (13.09%) and infrared LLLT (13.24%) than following placebo LLLT. There were no significant differences in mean average force or mean peak force between red and infrared LLLT. We conclude that both red than infrared LLLT are effective in delaying the development skeletal muscle fatigue and in enhancement of skeletal muscle performance. Further studies are needed to identify the specific mechanisms through which each wavelength acts.

Low-level laser therapy (LLLT) in human progressive-intensity running: effects on exercise performance, skeletal muscle status, and oxidative stress

The aim of this work was to evaluate the effects of low-level laser therapy (LLLT) on exercise performance, oxidative stress, and muscle status in humans. A randomized double-blind placebo-controlled crossover trial was performed with 22 untrained male volunteers. LLLT (810 nm, 200 mW, 30 J in each site, 30 s of irradiation in each site) using a multi-diode cluster (with five spots - 6 J from each spot) at 12 sites of each lower limb (six in quadriceps, four in hamstrings, and two in gastrocnemius) was performed 5 min before a standardized progressive-intensity running protocol on a motor-drive treadmill until exhaustion. We analyzed exercise performance (VO(2 max), time to exhaustion, aerobic threshold and anaerobic threshold), levels of oxidative damage to lipids and proteins, the activities of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), and the markers of muscle damage creatine kinase (CK) and lactate dehydrogenase (LDH). Compared to placebo, active LLLT significantly increased exercise performance (VO(2 max) p = 0.01; time to exhaustion, p = 0.04) without changing the aerobic and anaerobic thresholds. LLLT also decreased post-exercise lipid (p = 0.0001) and protein (p = 0.0230) damages, as well as the activities of SOD (p = 0.0034), CK (p = 0.0001) and LDH (p = 0.0001) enzymes. LLLT application was not able to modulate CAT activity. The use of LLLT before progressive-intensity running exercise increases exercise performance, decreases exercise-induced oxidative stress and muscle damage, suggesting that the modulation of the redox system by LLLT could be related to the delay in skeletal muscle fatigue observed after the use of LLLT.

Low-level infrared laser effect on plasmid DNA

Low-level laser therapy is used in the treatment of many diseases based on its biostimulative effect. However, the photobiological basis for its mechanism of action and adverse effects are not well understood. The aim of this study, using experimental models, was to evaluate the effects of laser on bacterial plasmids in alkaline agarose gel electrophoresis and Escherichia coli cultures. The electrophoretic profile of bacterial plasmids in alkaline agarose gels were used for studying lesions in DNA exposed to infrared laser. Transformation efficiency and survival of Escherichia coli AB1157 (wild-type), BH20 (fpg/mutM(-)), BW9091 (xth(-)), and DH5αF'Iq (recA(-)) cells harboring pBSK plasmids were used as experimental models to assess the effect of laser on plasmid DNA outside and inside of cells. Data indicate low-level laser: (1) altered the electrophoretic profile of plasmids in alkaline gels at 2,500-Hz pulsed-emission mode but did not alter at continuous wave, 2.5- and 250-Hz pulsed-emission mode; (2) altered the transformation efficiency of plasmids in wild-type and fpg/mutM(-) E. coli cells; (3) altered the survival fpg/mutM(-), xthA(-) and recA(-) E. coli cultures harboring pBSK plasmids. Low-level infrared laser with therapeutic fluencies at high frequency in pulsed-emission modes have effects on bacterial plasmids. Infrared laser action can differently affect the survival of plasmids in E. coli cells proficient and deficient in DNA repair mechanisms, therefore, laser therapy protocol should take into account fluencies, frequencies and wavelength of laser, as well as tissue conditions and genetic characteristics of cells before beginning treatment.

A fototerapia com diodo emissor de luz (LEDT) aplicada pré-exercício inibe a peroxidação lipídica em atletas após exercício de alta intensidade: um estudo preliminar

Estresse oxidativo é o termo geralmente utilizado para descrever os danos causados pelo desequilíbrio entre pró-oxidantes e antioxidantes no organismo. O aumento no consumo de O2 induzido pelo exercício físico está associado ao aumento das espécies reativas de oxigênio (EROs) sendo estas indutoras do estresse oxidativo. Embora as evidências indiquem um provável efeito inibitório da fototerapia com diodos emissores de luz (LEDT) sobre a produção das EROs, não existem estudos observando tal efeito em atletas. Este estudo preliminar destina-se a verificar os efeitos da aplicação de LEDT previamente ao exercício de alta intensidade sobre a peroxidação lipídica, mensurada através dos níveis sanguíneos de substâncias reativas ao ácido tiobarbitúrico (TBARS). Todos os seis atletas de voleibol do sexo masculino foram submetidos às duas situações: aplicação de LEDT efetiva e aplicação de LEDT placebo. O desempenho no protocolo de exercício adotado não revelou diferença (p > 0,05) entre as duas situações nas variáveis potência pico, potência média e índice de fadiga. Os resultados relacionados com a peroxidação lipídica foram: na situação LEDT efetiva, não foi possível observar diferença estatisticamente significante (p > 0,05) entre os níveis pré e pós-exercício (6,98 ± 0,81 e 7,02 ± 0,47nmol/mL); na situação LEDT (LBP) placebo, houve diferença estatisticamente significante (p = 0,05) entre os valores pré e pós-exercício (7,09 ± 1,28 e 8,43 ± 0,71nmol/mL). Tais resultados demonstram que a aplicação efetiva de LEDT parece ser eficaz no controle da peroxidação lipídica em atletas submetidos a exercício intenso