Acute dose-response effect of photobiomodulation therapy on 5-km running performance in trained runners: a randomized, double-blind, placebo-controlled, crossover study.

Photobiomodulation therapy (PBMT) has been advocated as a potential intervention to improve muscle performance and recovery in the health and sports context. However, the short- and long-term effects of PBMT on endurance running performance remain under-researched and controversial. The purpose of this study was to investigate the acute dose-response effect of PBMT with light-emitting diodes (LEDs) on endurance performance and rating of perceived exertion (RPE; 6-20 Borg) during a 5-km running trial in recreational runners. In a crossover design, eighteen young adult runners (28.7 ± 7.8 years) were randomized to receive 1 of 4 PBMT conditions (placebo, 300, 900, and 1260 Joules [J]) 60 min before the 5-km running trial on four occasions, separated by a 2-wk washout period. The treatments were applied to the quadriceps, hamstrings, and gastrocnemius muscles of both legs using a device containing 200 LEDs (100 red and 100 infrared). The following variables were assessed: endurance performance (i.e. total time, mean velocity, and velocity in the split distances at the initial 200 m and every 400 m lap) and RPE in the split distances at the initial 200 m and every 400 m lap. Data normality and homogeneity were tested using Shapiro-Wilk's and Levene's tests, respectively. Differences between treatment conditions were assessed using the analysis of variance tests (one- or two-way ANOVA, depending on the comparisons), complemented by the Bonferroni post hoc test. There were significant time effects for the running velocity and RPE in the split distances (p < 0.0001), with no significant treatment-by-time interaction (running velocity, p = 0.59; RPE, p = 0.95). The mean velocity (p = 0.997), total time (p = 0.998), and total mean of the RPE (p = 0.91) were similar between treatment conditions. In conclusion, acute PBMT with LEDs at doses of 300, 900, and 1260 J is not recommended for improving endurance performance and RPE in the 5-km running trial in recreational runners.

Influence of Different Photobiomodulation Parameters on Multi-Potent Adipose Tissue Mesenchymal Cells In Vitro.

Objective: Investigating the effect of different parameters of photobiomodulation (PBM) with low-power laser on multi-potent mesenchymal stem cells (MSCs) derived from adipose tissue in terms of proliferation and cell death. Methods: MSCs were submitted to PBM applications with combinations of the following physical parameters: control group (no intervention), wavelengths of 660 and 830 nm; energy of 0.5, 2, and 4 J; and power of 40 and 100 mW. MSC analysis was performed using MetaXpress® software at 24, 48, and 72 h. Results: Irradiation promoted a significant increase in cell proliferation (p < 0.05), with 830 nm laser, 100 mW, with energy of 0.5, 2, and 4 J in relation to the control group at all times. PBM with 660 nm, power of 40 mW, and energy of 0.5, 2, and 4 J produced greater cell death at 24 h compared with the control group. At the time of 72 h, there was no significant difference concerning cell death. Conclusions: According to the results found, we can conclude that both wavelengths were effective; however, the 830 nm laser was more effective in terms of cell proliferation compared with the 660 nm laser. The 660 nm wavelength showed a significant increase in cell death when compared with the 830 nm laser.

Photobiomodulation therapy (red/NIR LEDs) reduced the length of stay in intensive care unit and improved muscle function: A randomized, triple-blind, and sham-controlled trial.

CONTEXT: Photobiomodulation therapy (PBMT) has been widely used to improve strength, fatigue resistance and increase muscle mass in healthy individuals. These effects could help critically ill patients admitted to intensive care units (ICUs) who show reduced mobility and muscle strength. ICU-acquired weakness lessens overall health and increases the patient's length of stay in the ICU. OBJECTIVE: This study evaluated the effects of PBMT using low intensity light-emitting diodes (LEDs) on the mobility and muscle strength (functional capacity) and length of stay of patients admitted to hospital ICU. METHODS: This randomized, triple-blind, sham-controlled trial was conducted in a hospital ICU. Sixty patients were randomly assigned to two equal groups: (a) PBMT and (b) Sham. PBMT was applied daily to patients until their discharge from the ICU, using a flexible neoprene array of 264 LEDs (120 at 635 nm, 1.2 mW each; 144 at 880 nm, 15 mW each) for 90s (207.36 Joules) at each site. Ten sites were located bilaterally on the thighs, legs, arms, and forearms ventrally and dorsally, 15 min totaling 2,073.6 Joules per session. Outcomes were length of stay (in h) until discharge from the ICU, muscle strength by the Medical Research Council (MRC) score and handgrip dynamometry (HGD), patient mobility by Intensive Care Unit Mobility Scale (IMS) and the Simplified Acute Physiology Score 3 (SAPS 3) for predicting mortality of patients admitted to the ICU. RESULTS: PBMT reduced the average length of stay in the ICU by ~30% (p = 0.028); increased mobility (IMS: 255% vs. 110% p = 0.007), increased muscle strength (MRC: 12% vs. -9% p = 0.001) and HGD (34% vs. -13% p < 0.001), and the SAPS3 score was similar (p > 0.05). CONCLUSION: The results suggest that daily PBMT can reduce the length of stay of ICU patients and increase muscle strength and mobility.

Dose and time-response effect of photobiomodulation therapy on glycemic control in type 2 diabetic patients combined or not with hypoglycemic medicine: A randomized, crossover, double-blind, sham-controlled trial.

Photobiomodulation therapy (PBMt) combined or not with oral hypoglycemic medication has not been investigated in type 2 diabetes (T2DM) patients. All 10 T2DM patients were assessed randomly at 6 different occasions (3 with and 3 without regular oral hypoglycemic medication). Capillary glycemia was assessed after overnight fast (pre-prandial), 1 h postprandially (standardized meal, 338 kcal), and 30 min, 3 h, 6 h, 12 h post-PBMt (830 nm; 25 arrays of LEDs, 80 mW/array). Three doses (0 J-sham, 100 J, 240 J per site) were applied bilaterally on quadriceps femoris muscles, hamstrings, triceps surae, ventral upper arm and forearm; and randomly combined or not with oral hypoglicemic medication, totaling six different therapies applied for all 10 TDM2 patients (PBMt sham, PBMt 100 J, PBMt 240 J, PBMt sham + medication, PBMt 100 J + medication, PBMt 240 J + medication). Cardiac autonomic control was assessed by heart rate variability (HRV) indices. Without medication, there was reduction in glycemia after all PBMt doses, with 100 J as the best dose that persisted until 12 h and presented lower area under the curve (AUC). With medication, glycemia decreased similarly among doses. No differences between 100 J and sham + medication, but AUC was significantly lower after 100 J, suggesting better glycemic control. Low frequency component of HRV increased after sham + medication and 100 J, suggesting higher sympathetic activation. PBMt showed time- and dose-response effect to reduce glycemia in T2DM patients. Effects on HRV were consistent with glycemic control.

Effects of the association of different volumes of strength training with photobiomodulation therapy on insulin resistance: A protocol for a randomized, triple-blind, placebo-controlled trial.

Background: Insulin resistance (IR) is the main risk factor for developing type 2 diabetes. Both strength training (ST) and photobiomodulation therapy (PBMt) reduce IR, but the effect of combining different volumes of ST with PBMt is unknown. Methods: Overweight/obese individuals will be assigned to 4 groups (n = 12/group): ST with volume following international guidelines (3 sets per exercise - high volume) or one-third of this volume (1 set per exercise - low volume), combined with PBMt or placebo. ST will be performed for 20 sessions over 10 weeks and will consist of 7 exercises. The PBMt will be applied after training sessions using blankets with light emitters (LEDs) placed over the skin on the frontal and the posterior region of the body, following the parameters recommended by the literature. The placebo group will undergo an identical procedure, but blankets will emit insignificant light. To measure plasma glucose and insulin concentrations, oral glucose tolerance tests (OGTT) will be performed before and after the training period. Thereafter, IR, the area under the curve of glucose and insulin, and OGTT-derived indices of insulin sensitivity/resistance will be calculated. Expected impact on the field: This study will determine the effects of different ST volumes on IR and whether the addition of PBMt potentiates the effects of ST. Because previously sedentary, obese, insulin-resistant individuals might not comply with recommended volumes of exercise, the possibility that adding PBMt to low-volume ST enhances ST effects on IR bears practical significance.

Photobiomodulation Therapy on the Treatment of Insulin Resistance: A Narrative Review.

Background: Insulin resistance (IR) is the main risk factor for the development of type 2 diabetes mellitus (DM2). Noninvasive and nonpharmacological therapies, such as exercise and diet are effective in treating IR and DM2; however, adherence to them generally is low and diminishes positive effects in the long term. Photobiomodulation therapy (PBMT) is another noninvasive and nonpharmacological therapy, which produces positive effects on mitochondrial metabolism, oxidative stress, and inflammation generally linked to IR and DM2 and may improve or attenuate the severity of these diseases. Objective: In this narrative review, we focus on the available literature related to the effects of PBMT on IR. Results: In fact, recent in vitro and in vivo studies have demonstrated improvements in IR in skeletal muscle, adipose tissue, and hepatic cells mediated by PBMT. Further, there is evidence that PBMT can potentiate exercise-induced improvement in IR through ameliorating mitochondrial dysfunction, reducing inflammation, and modulating oxidative stress. Moreover, reduced adiposity and altered gut microbiota also appear to mediate PBMT effects on IR. Conclusions: Although these results are exciting, randomized clinical trials are urgently needed to confirm the clinical relevance of PBMT in the treatment of IR. Investigation about the effects of PBMT combined with different volumes of physical exercises may also contribute significantly for those patients having difficulty to adhere to the recommended minimal exercise volume. Finally, studies on PBMT parameters (e.g., dosimetry, wavelengths, single-point vs. full-body irradiation) are also necessary for the appropriate prescription of PBMT for the treatment of IR.

Neuromuscular electrical stimulation but not photobiomodulation therapy improves cardiovascular parameters of rats with heart failure.

The aim of the present study was to analyze the effect of neuromuscular electrical stimulation (NMES) and photobiomodulation (PBMT) on the cardiovascular parameters, hemodynamic function, arterial baroreflex sensitivity (BRS), and autonomic balance (ANS) of rats with heart failure (HF). Male Wistar rats (220-290 g) were organized into five groups: Sham (n = 6), Control-HF (n = 5), NMES-HF (n = 6), PBMT-HF (n = 6), and NMES + PBMT-HF (n = 6). Myocardial infarction (MI) was induced by left coronary artery ligation. Animals were subjected to an eight-week NMES and PBMT protocol. Statistical analysis included the General Linear Model (GLM) followed by a Bonferroni post-hoc test. Rats of the NMES-HF group showed a higher MI area than the Control-HF (P = 0.003), PBMT-HF (P = 0.002), and NMES + PBMT-HF (P = 0.012) groups. NMES-HF and NMES + PBMT-HF showed higher pulmonary congestion (P = 0.004 and P = 0.02) and lower systolic pressure (P = 0.019 and P = 0.002) than the Sham group. NMES + PBMT-HF showed lower mean arterial pressure (P = 0.02) than the Sham group. Control-HF showed a higher heart rate than the NMES-HF and NMES + PBMT-HF (P = 0.017 and P = 0.013) groups. There was no difference in the BRS and ANS variables between groups. In conclusion, eight-week NMES isolated or associated with PBMT protocol reduced basal heart rate, systolic and mean arterial pressure, without influence on baroreflex sensibility and autonomic control, and no effect of PBMT was seen in rats with HF.

Full Body Photobiomodulation Therapy to Induce Faster Muscle Recovery in Water Polo Athletes: Preliminary Results.

Objective: To investigate the recovery of male water polo athletes applying full body photobiomodulation therapy (PBMT) regarding inflammation and muscle damage markers, testosterone and cortisol hormonal responses, heart rate variability (HRV), maximal voluntary contraction, and squat jump (SJ) after official water polo matches. Background: PBMT has been applied locally on specific muscle groups to induce faster recovery and improve the performance of athletes and nonathletes. However, many sports modalities require movement of the whole body, and a full body PBMT could be more adequate to irradiate large muscle areas homogeneously and faster. Methods: In a randomized, parallel, and double-blinded design, 13 athletes (whole team) aged 18 years attended the study and were allocated into two groups: PBMT (dose of 6.9 J/cm2, irradiance of 46.17 mW/cm2, 5 min irradiation) and placebo treatment. The study was conducted during the 2019 Brazilian under 20 water polo championship. All athletes were assessed by blood samples and neuromuscular evaluation. Immediately after each match, all athletes received PBMT (effective or placebo). Results: No significant interactions (raw values and percentage related to baseline) were observed for testosterone and cortisol, tumor necrosis factor-alpha, interleukin-6, creatine kinase concentration, maximal isometric voluntary contraction, SJ test, and HRV. Only an isolated interaction (decrease) was found for lactate dehydrogenase (LDH) response after the first match (p = 0.004, post-hoc p = 0.038). Conclusions: The parameters of the full body PBMT of this study did not induce faster recovery of inflammatory, muscle damage (excepting LDH), testosterone, cortisol, HRV, and neuromuscular responses during repeated days of water polo matches.

Time-Response of Photobiomodulation Therapy by Light-Emitting Diodes on Muscle Torque and Fatigue Resistance in Young Men: Randomized, Double-Blind, Crossover and Placebo-Controlled Study.

Background: Photobiomodulation therapy (PBMT) by lasers or light-emitting diodes (LEDs) has been used in the last two decades to increase muscle performance in humans. The main findings of PBMT on muscle performance are increment in torque and number of muscle contractions, and fatigue resistance in high-intensity exercises. Although there are suggested light energies to be followed, the literature has also pointed out to a possible time-response of PBMT to increase exercise performance and recovery in humans. Objective: To investigate the possible time-response of PBMT by LEDs to increase muscle performance in young men regarding peak torque (PT), rate of torque development (RTD), fatigue resistance, and subjective perception of effort in maximal voluntary isometric contractions (MVIC) of elbow flexion. Methods: This randomized, double-blind, placebo-controlled, crossover trial with two arms enrolled 34 healthy and physically active young men, but 30 (21.10 ± 2.25 years old) completed all procedures. All volunteers were allocated into two equal arms (groups): PBMT (60 J; 1152 mW; 52 sec; and 166.75 cm2) applied on biceps brachii by a flexible array of LEDs, and placebo treatment. Each arm (n = 15) investigated the time-response (5 min, 1 h, 3 h, and 6 h) of PBMT in a randomized, double-blind, and crossover manner on the PT, RTD, fatigue resistance, and subjective perception of effort. Results: There were no significant results (p > 0.05) for all comparisons within and between groups regarding PT, RTD, fatigue resistance, and subjective perception of effort in MVIC of the elbow flexion in all time-response tested (5 min, 1 h, 3 h, and 6 h) before or after fatigue test. Only RTD did not decay significantly after fatigue test at all time-responses for PBMT group. Conclusions: PBMT was not effective to increase muscle performance and decrease fatigue to demonstrate the possible time-response in humans.

Effects of Photobiomodulation Therapy and Restriction of Wrist Extensor Blood Flow on Grip: Randomized Clinical Trial.

Objective: To evaluate the influence of two different photobiomodulation therapy (PBMT) protocols (red 660 nm vs. infrared 830 nm) combined with a blood flow restriction (BFR) training protocol in wrist extensor muscles on handgrip, wrist extension force, and electromyographic behavior [root mean square (RMS)]. Background: PBMT has been widely used to increase muscle performance and recovery in recent clinical trials. However, there is no evidence whether PBMT (red and/or infrared) can promote better results when combined with BFR, a known method to induce better strength gains. Methods: This study was a randomized controlled trial including 58 volunteers allocated into four groups: (1) control (conventional strengthening), (2) BFR (strengthening with BFR), (3) 660 nm (BFR strengthening with 660 nm PBMT-35 mW; 0.05 cm2; 2.10 J, total energy 18.9 J), and (4) 830 nm (BFR strengthening with 830 nm PBMT-32 mW; 0.101 cm2; 1.92 J, total energy 17.2 J). Data were analyzed by using a mixed-effects model, with a 5% significance index. Results: A statistically significant increase was obtained for handgrip strength for the 660 nm group [27.36 ± 2.61 kilogram force (kgF)] compared with the 830 nm group (23.04 ± 3.06 kgF) (p = 0.010) and for wrist extensor strength in the 660 nm (7.77 ± 0.58 kgF) and BFR (7.54 ± 0.92 kgF) groups compared with the control group (5.33 ± 0.61 kgF) (p = 0.001 and p = 0.004, respectively). The RMS value for the 660 nm group was significantly higher than control (p < 0.0001), BFR (p < 0.0001), and the 830 nm group (p = 0.0009). Conclusions: The association of PBMT (660 nm) and BFR was effective for increasing handgrip strength of the wrist extensors, associated with an increase in RMS.

Effect of 12 Weeks of Endurance Training Combined with Creatine Supplement, Photobiomodulation Therapy, or Both on Performance and Muscle Damage in Rats.

Background: Photobiomodulation therapy (PBMT) and creatine (Cr) intake have been used in conjunction with heavy training, but little is known about their possible effects during a long-term training program. Objective: We assessed long-term use of PBMT and Cr in an exercise training program. Methods: Twenty-five male Wistar rats weighing ∼300 g were randomly allocated to one of five groups: a nontraining control group, a training group, a training group receiving Cr, a training group receiving PBMT, and a training group receiving both PBMT and Cr. The training program consisted of 12 weeks of daily swimming training. PBMT was delivered in six points with a laser device (808 nm, 100 mW, 30 sec per point of irradiation, 3 J, 75 J/cm2). Results: All training groups showed significantly higher peak force and longer time to 50% decay of force, and lower creatine kinase (CK) levels than the nontraining control group, thus confirming the benefit of the training program. In all outcomes related to muscle performance, the groups receiving PBMT with or without Cr supplement performed significantly better (p < 0.05) peak force and time of force decay during an electrical stimulation protocol than all the other groups. In addition, CK levels were also significantly lower for the PBMT groups than for the other groups. Conclusions: We conclude that PBMT alone or in conjunction with Cr supplement during a 12-week training program resulted in significantly better muscle performance and lower levels of CK, a biochemical marker of muscle damage.

Acute Photobiomodulation by LED Does Not Alter Muscle Fatigue and Cycling Performance.

PURPOSE: The purpose of the present study was to investigate the ergogenic effects of two doses of photobiomodulation therapy (PBMT) in comparison to placebo on markers of respiratory and muscle activity, blood acid-base, ion and lactate concentrations, indicators of muscle fatigue (global, central, and peripheral), and time to exhaustion in severe-intensity cycling. METHODS: Two separate studies were performed, both in a pseudorandomized and balanced, crossover design. In study 1, 14 male recreational cyclists completed three constant-load, severe-intensity cycling bouts that were duration matched. The PBMT (18 × 38 cm array with 200 diodes) treatments occurred before bouts at 260, 130, or 0 J (placebo) doses. EMG activity of selected lower limb musculature was assessed during each bout. Maximal voluntary contractions of knee extension with peripheral nerve stimulations and EMG activity evaluation of vastus lateralis was also performed before and after cycling. In study 2, 13 recreational cyclists performed three bouts of constant-load, severe-intensity cycling until exhaustion, preceded by PBMT as detailed previously. Blood lactate concentrations, respiratory responses, EMG activity, and capillary gasometry aspects were monitored. RESULTS: In both studies, there were no interactions effects (time-condition) on the EMG activity, which was displayed as root mean square (P ≥ 0.168) and median frequency (P ≥ 0.055) during cycling. In study 1, there were no interaction effects on the indicators of muscle fatigue after exercise (P ≥ 0.130). In study 2, there were no differences on time to exhaustion (P = 0.353) and no interaction effects among the physiological responses monitored (P ≥ 0.082). CONCLUSIONS: Based on our findings, the PBMT at 260- and 130-J doses does not have a beneficial effect on muscle fatigue, cycling performance, metabolic parameters, and muscle activity in male recreational cyclists.

Can photobiomodulation therapy (PBMT) control blood glucose levels and alter muscle glycogen synthesis?

Photobiomodulation therapy (PBMT) has many effects on the energy metabolism of musculoskeletal tissue, such as increased glycogen and adenosine triphosphate synthesis. In addition, these effects may be due to a systemic blood glucose control. Twenty-four Wistar rats were randomly and equally allocated into four groups: sham, PBMT 10 J/cm2, PBMT 30 J/cm2 and PBMT 60 J/cm2. The animals were fasting for 6 h for blood glucose evaluations during pre-irradiation period, 1 h, 3 h and 6 h after PBMT. Muscle glycogen synthesis was measured 24 h after PBMT. This PBMT used a cluster of 69 LEDs (light-emitting diodes) with 35 red (630 ± 10 nm) and 34 infrared (850 ± 20 nm); 114 mW/cm2 for 90s (10 J/cm2), 270 s (30 J/cm2), 540 s (60 J/cm2) applied on large muscle areas (back and hind legs) of the animals. The 10 J/cm2 group showed lower blood glucose levels and glucose variability over 6 h (5.92 mg/dL) compared to the sham (13.03 mg/dL), 30 J/cm2 (7.77 mg/dL) and 60 J/cm2 (9.07 mg/dL) groups. The PBMT groups had the greatest increase in muscle glycogen (10 J/cm2 > 60 J/cm2 > 30 J/cm2 > sham), characterizing a triphasic dose-response of PBMT. There was a strong negative correlation between blood glucose variability over 6 h and muscle glycogen concentration for 10 J/cm2 group (r = -0.94; p < .001) followed by 30 J/cm2 group (r = -0.84; p < .001) and 60 J/cm2 group(r = -0.73; p < .006). These results suggest that PBMT can play a very important role in the control of blood glucose levels, and its possible mechanism of action is the induction of greater muscle glycogen synthesis independently of physical exercise.

Systematic Review of Photobiomodulation Therapy (PBMT) on the Experimental Calcaneal Tendon Injury in Rats.

This systematic review analyzed the light parameters and the effects of photobiomodulation therapy (PBMT) through low-level laser therapy (LLLT) and/or LED (light-emitting diode) on tendon repair of rats submitted to calcaneal injury. This study was conducted in accordance with the guidelines of the Preferred Reporting Items for Meta-Analysis, and PubMed and MEDLINE databases were accessed to search eligible studies published in English. The search terms were as follows: "Achilles tendon" or "Calcaneal tendon" or "tendon injuries" or "soft tissue injuries" and "tendinopathy" or "tendinitis" and "low-level light therapy" or "low-level laser therapy" or "low intensity power therapy" or "light-emitting diode" or photobiomodulation." The SYRCLE (SYstematic Review Center for Laboratory animal Experimentation) risks of bias was used to assess the risk of bias for selected studies. A total of 225 studies were found based on the descriptors used, and only 33 studies were eligible. Light parameters identified per point of irradiation were approximately 60 mW (continuous mode at infrared spectra), 2 W cm-2 , 2 J and 45 J cm-2 . Light parameters at red spectra, continuous versus pulsed mode, and PBMT combined or compared with other therapies such as ultrasound, and studies using unhealthy rats (ovariectomized and/or diabetic models) were also identified and grouped according to these similarities. The main effects found were decreased inflammatory markers and signs of inflammatory process. PBMT (laser/LED) has positive effects in reducing the inflammatory and time for tissue repair in animal models of tendon injury and/or tendinitis using parameters identified.

Photobiomodulation 30 min or 6 h Prior to Cycling Does Not Alter Resting Blood Flow Velocity, Exercise-Induced Physiological Responses or Time to Exhaustion in Healthy Men.

PURPOSE: The aim of the current study was to investigate the effects of photobiomodulation therapy (PBMT) applied 30 min or 6 h prior to cycling on blood flow velocity and plasma nitrite concentrations at rest, time to exhaustion, cardiorespiratory responses, blood acid-base balance, and K+ and lactate concentrations during exercise. METHODS: In a randomized, crossover design, 13 healthy untrained men randomly completed four cycling bouts until exhaustion at the severe-intensity domain (i.e., above respiratory compensation point). Thirty minutes or 6 h prior to the cycling trials, participants were treated with PBMT on the quadriceps, hamstrings, and gastrocnemius muscles of both limbs using a multi-diode array (11 cm × 30 cm with 264 diodes) at doses of 152 J or a sham irradiation (with device turned off, placebo). Blood samples were collected before and 30 min or 6 h after treatments to measure plasmatic nitrite concentrations. Doppler ultrasound exams of the femoral artery were also performed at the same time points. Cardiorespiratory responses, blood acid-base balance, and K+ and lactate concentrations were monitored during exercise sessions. RESULTS: PBMT did not improve the time to exhaustion (p = 0.30). At rest, no differences were found in the peak systolic velocity (p = 0.97) or pulsatility index (p = 0.83) in the femoral artery, and in plasma nitrite concentrations (p = 0.47). During exercise, there were no differences for any cardiorespiratory response monitored (heart rate, p = 0.15; oxygen uptake, p = 0.15; pulmonary ventilation, p = 0.67; carbon dioxide output, p = 0.93; and respiratory exchange ratio, p = 0.32), any blood acid-base balance indicator (pH, p = 0.74; base excess, p = 0.33; bicarbonate concentration, p = 0.54), or K+ (p = 0.22) and lactate (p = 0.55) concentrations. CONCLUSIONS: PBMT at 152 J applied 30 min or 6 h before cycling at severe-intensity did not alter resting plasma nitrite and blood flow velocity in the femoral artery, exercise-induced physiological responses, or time to exhaustion in healthy untrained men.

Acute effect of photobiomodulation using light-emitting diodes (LEDs) on baroreflex sensitivity during and after constant loading exercise in patients with type 2 diabetes mellitus.

To evaluate the photobiomodulation (PBM) effect on the cardiovascular autonomic control, analyzed by baroreflex sensitivity (sequence method), during constant load exercise and recovery in diabetic men, we evaluated 11 men with type 2 diabetes (DM2) (40-64 years). The constant workload exercise protocol (TECC) was performed on two different days, 14 days apart from each other, to guarantee PBM washout period. After PBM by light-emitting diode (LED) irradiation (150 J or 300 J or placebo), 10 min of rest (REST) was performed. After this period, the volunteer was positioned on a cycloergometer to start the test (1-min rest, 3-min free-load heating, 6-min constant workload-EXERCISE, 6-min free-load cool-down, 1-min rest) followed by a sitting period of 10 min (RECOVERY). The constant workload corresponded to 80%VO2GET (gas exchange threshold) identified by a previous cardiopulmonary exercise test (CPET). PBM was applied in continuous mode, contact technique, bilaterally, on both femoral quadriceps and gastrocnemius muscle groups. The electrocardiogram R-R intervals (BioAmp FE132) and the peripheral pulse pressure signals (Finometer PRO) were collected continuously throughout the protocol. Stable sequences of 256 points were chosen at REST, EXERCISE, and RECOVERY. The baroreflex sensitivity (BRS) was computed in time domain according to the sequence method (αseq). The comparison between therapies (150 J/300 J/placebo) and condition (REST, EXERCISE, and RECOVERY) was performed using the ANOVA two-way repeated measures test. There was no interaction between therapy and conditions during the TECC. There was only the condition effect (p < 0.001), showing that the behavior of αseq was similar regardless of the therapy. Photobiomodulation with 150 J or 300 J applied previously to a moderate-intensity TECC in DM2 was not able to promote cardiovascular autonomic control changes leading to an improvement in BRS.

Photobiomodulation effect on local hemoglobin concentration assessed by near-infrared spectroscopy in humans.

Exposure of biological tissue to photobiomodulation therapy (PBMT) seems to increase the oxygen availability and mitochondrial electrochemical activity. With the advancement of new technologies, such as near-infrared spectroscopy (NIRS), information can be obtained about the balance between oxygen utilization and delivery by assessing local oxy- ([O2Hb]) and deoxy-myohemoglobin ([HHb]) concentrations, both measured in micromolars (µM). Consequently, NIRS can be used to study ("in vivo") PBMT effects on the oxidative system, including oxygen availability. Thus, the main objective of the present study was to use NIRS to investigate the acute effects of PBMT by light-emitting diode (LED) on the oxygen delivery and utilization in humans. Twelve healthy young participants were treated with a LED device (850 nm, 50 mW, 2 J) and placebo applied over the proximal third of the flexor carpi ulnaris muscle of the left or right forearm selected in a random order. The LED was applied in direct contact with skin and the device was switched on for 40 s in 4 different interventions (I1, I2, I3 and I4) with a 3-min interval between interventions. The placebo condition was considered as the period before the first PBMT. The NIRS device was used to evaluate the relative changes in [O2Hb] and [HHb] before and after placebo and interventions. We found that PBMT statistically increased the [O2Hb] in 0.39 µM. These results demonstrate the potential of PBMT to increase oxygen availability.

Acute effects of photobiomodulation therapy applied to respiratory muscles of chronic obstructive pulmonary disease patients: a double-blind, randomized, placebo-controlled crossover trial.

To investigate the effects of photobiomodulation applied to respiratory muscles on lung function, thoracoabdominal mobility, respiratory muscle strength, and functional capacity in COPD patients. This is a randomized double-blind crossover clinical trial. Twelve male COPD patients participated in the study. Participants were randomly allocated to receive two photobiomodulation sessions, 1 week apart: (1) an effective photobiomodulation session applied at the main respiratory muscles by means of a cluster with 69 light-emitting diodes (LEDs), containing 35 red (630 ± 10 nm; 10 mW; 0.2 cm2) and 34 near-infrared (830 ± 20 nm; 10 mW; 0.2 cm2) LEDs and (2) a sham photobiomodulation session, following the same procedures without emitting light. The primary outcomes were pulmonary function (spirometric indexes); thoracoabdominal mobility (cirtometry); respiratory muscle strength (maximal respiratory pressures), assessed at three moments: (1) baseline, (2) 1 h after intervention, and (3) 24 h after intervention; and the functional capacity, assessed by the 6-min walk test (6MWT) at baseline and 24 h after intervention. No significant interactions were found for spirometric variables, maximal respiratory pressures, and cirtometry. However, there was a Time × Condition interaction (F = 18.63; p = 0.001; η2p = 0.62) in the walked distance on the 6MWT, with a significant increase after photobiomodulation intervention (p < 0.01) compared with the baseline. Photobiomodulation applied to respiratory muscles was effective in improving acute functional capacity in COPD patients. To the best of our knowledge, this is the first study assessing the effects of photobiomodulation applied to respiratory muscles in patients with COPD.

Insulin resistance is improved in high-fat fed mice by photobiomodulation therapy at 630 nm.

Photobiomodulation therapy (PBMT) in the infrared spectrum exerts positive effects on glucose metabolism, but the use of PBMT at the red spectrum has not been assessed. Male Swiss albino mice were divided into low-fat control and high-fat diet (HFD) for 12 weeks and were treated with red (630 nm) PBMT or no treatment (Sham) during weeks 9 to 12. PBMT was delivered at 31.19 J/cm2 , 60 J total dose per day for 20 days. In HFD-fed mice, PBMT improved glucose tolerance, insulin resistance and fasting hyperinsulinemia. PBMT also reduced adiposity and inflammatory infiltrate in adipose tissue. Phosphorylation of Akt in epididymal adipose tissue and rectus femoralis muscle was improved by PBMT. In epididymal fat PBMT reversed the reduced phosphorylation of AS160 and the reduced Glut4 content. In addition, PBMT reversed the alterations caused by HFD in rectus femoralis muscle on proteins involved in mitochondrial dynamics and ß-oxidation. In conclusion, PBMT at red spectrum improved insulin resistance and glucose metabolism in HFD-fed mice.