Can pre-exercise photobiomodulation improve muscle endurance and promote recovery from muscle strength and injuries in people with different activity levels? A meta-analysis of randomized controlled trials.

Photobiomodulation therapy (PBMT) was introduced as an ergogenic aid for sport performance in healthy individuals is still controversial. The main aim of this study is to assess the potential enhancements in muscle endurance and recovery from muscle strength and injuries mediated by PBMT among individuals exhibiting diverse activity levels. Randomized controlled trials (RCT) of PBMT interventions for healthy people (both trained and untrained individuals) exercising were searched (up to January 16, 2024) in four electronic databases: Web of Science, PubMed, Scopus and Embase. Primary outcome measures included muscle endurance, muscle strength and creatine kinase (CK) levels; secondary outcome measure included Lactate dehydrogenase (LDH) levels. Subgroup analyses based on physical activity levels were conducted for each outcome measure. Thirty-four RCTs were included based on the article inclusion and exclusion criteria. Statistical results showed that PBMT significantly improved muscle endurance (standardized mean difference [SMD] = 0.31, 95%CI 0.11, 0.51, p < 0.01), indicating a moderate effect size. It also facilitated the recovery of muscle strength (SMD = 0.24, 95%CI 0.10, 0.39, p < 0.01) and CK (mean difference [MD] = -77.56, 95%CI -112.67, -42.44, p < 0.01), indicating moderate and large effect sizes, respectively. Furthermore, pre-application of PBMT significantly improved muscle endurance, recovery of muscle strength and injuries in physically inactive individuals and athletes (p < 0.05), while there was no significant benefit for physically active individuals. Pre-application of PBMT improves muscle endurance and promotes recovery from muscle strength and injury (includes CK and LDH) in athletes and sedentary populations, indicating moderate to large effect sizes, but is ineffective in physically active populations. This may be due to the fact that physically active people engage in more resistance training, which leads to a decrease in the proportion of red muscle fibres, thus affecting photobiomodulation.

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.

Effect of photobiomodulation therapy on performance and running economy in runners: A randomized double-blinded placebo-controlled trial.

The objective of this study was to evaluate effects of photobiomodulation therapy (PBMT) on the 3000 m running performance (primary outcome), running economy (RE), metabolic cost and ratings of perceived exertion during running (secondary outcomes). Twenty male endurance athletes performed 4-min treadmill rectangular test at 12 km.h-1 monitored by a gas analyser. After that, PBMT or placebo in each lower limb was applied, followed performed a maximum test of 3000 m. Immediately after 3000 m test, the athletes repeated the treadmill test. Another application of PBMT/placebo was done after the treadmill test, and athletes went back to the laboratory 24 h later to repeat the treadmill test. After a 72 h interval, athletes repeated all procedures with another treatment intervention (PBMT/placebo). Athletes performed the 3000 m running test ~7s faster when treated with PBMT with similar effort score compared placebo condition. The RE remains unchanged immediately post 3000 m running test, nonetheless RE measured post-24 h improved by 5% with PBMT application without changes in metabolic cost. The PBMT pre- and post-conditioning enhanced the 3000 m running performance and improved RE 24 h following the 3000 m test. However, no changes on ratings of perceived exertion and metabolic cost with the application of PBMT.

Thermographic response resulting from strength training: A preliminary study

INTRODUCTION: Exercise induces modifications in thermal homeostasis. The type of exercise may have a specific impact on skin temperature (Tsk). OBJECTIVE: To analyze and compare the behavior of Tsk in a resistance training between men and women and monitor the thermal recovery response. MATERIAL AND METHODS: Sixteen male and female adults (24.56±3.22 years old) underwent a resistance circuit training session. They performed 3 sets of 12 repetitions with 70-80% 1 RM for lat pulldown, leg press, and biceps arm curl exercises. Thermograms were taken in anterior and posterior body view at rest, 20min, and 24h after training. Tsk was measured in the body regions of interest corresponding to the brachial biceps, quadriceps, and upper back. ANOVA with Tukey's post hoc test was used to analyze Tsk changes among moments, and independent samples t-test was used to compare Tsk between males and females. RESULTS: At rest, women showed Tsk significantly lower than men. There was no significant Tsk change 20min after exercise. However, Tsk increased 24h after exercise in the upper back for men compared with baseline and in quadriceps for women compared with baseline and 20min after exercise (p < 0.05). CONCLUSION: The Tsk of women at rest is lower than that of men. A resistance circuit training session does not significantly change Tsk 20min after exercise, but it increases Tsk 24h after training in the upper back for men and quadriceps for women

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Low-intensity electrical muscle stimulation induces significant increases in muscle strength and cardiorespiratory fitness.

The aim of this study was to investigate the effect of low-intensity exercise training using belt electrode skeletal muscle electrical stimulation on muscle strength and cardiorespiratory fitness in healthy subjects. Nineteen healthy subjects were allocated into control or intervention groups; in both groups the participants kept regular physical activity while the intervention group underwent 30 min B-SES training at 3-4 METs for four weeks. Knee extensor muscle strength and cardiorespiratory endurance during incremental exercise test were measured at baseline and after four weeks for all participants. The relative change of knee extensor muscle strength in the intervention group was significantly higher than control group (p < .05). Also, oxygen uptake at ventilator threshold and peak oxygen uptake during incremental exercise test significantly increased in the intervention group when compared with control group (p < .05). This study showed that prolonged low-intensity B-SES training resulted in significant increases in muscle strength and cardiorespiratory fitness in healthy subjects. Our present work suggested that B-SES training could assist patients who might have difficulty performing adequate voluntary exercise because of excessive obesity, orthopaedic problems and chronic diseases such as cardiovascular disease and type 2 diabetes. An intervention study conducted for such patients is strongly recommended.

Muscular pre-conditioning using light-emitting diode therapy (LEDT) for high-intensity exercise: a randomized double-blind placebo-controlled trial with a single elite runner.

Recently, low-level laser (light) therapy (LLLT) has been used to improve muscle performance. This study aimed to evaluate the effectiveness of near-infrared light-emitting diode therapy (LEDT) and its mechanisms of action to improve muscle performance in an elite athlete. The kinetics of oxygen uptake (VO2), blood and urine markers of muscle damage (creatine kinase--CK and alanine), and fatigue (lactate) were analyzed. Additionally, some metabolic parameters were assessed in urine using proton nuclear magnetic resonance spectroscopy ((1)H NMR). A LED cluster with 50 LEDs (λ = 850 nm; 50 mW 15 s; 37.5 J) was applied on legs, arms and trunk muscles of a single runner athlete 5 min before a high-intense constant workload running exercise on treadmill. The athlete received either Placebo-1-LEDT; Placebo-2-LEDT; or Effective-LEDT in a randomized double-blind placebo-controlled trial with washout period of 7 d between each test. LEDT improved the speed of the muscular VO2 adaptation (∼-9 s), decreased O2 deficit (∼-10 L), increased the VO2 from the slow component phase (∼+348 ml min(-1)), and increased the time limit of exercise (∼+589 s). LEDT decreased blood and urine markers of muscle damage and fatigue (CK, alanine and lactate levels). The results suggest that a muscular pre-conditioning regimen using LEDT before intense exercises could modulate metabolic and renal function to achieve better performance.

Phototherapy with combination of super-pulsed laser and light-emitting diodes is beneficial in improvement of muscular performance (strength and muscular endurance), dyspnea, and fatigue sensation in patients with chronic obstructive pulmonary disease.

Phototherapy is an electrophysical intervention being considered for the retardation of peripheral muscular fatigue usually observed in chronic obstructive pulmonary disease (COPD). The objective of this study was to evaluate the acute effects of combination of super-pulsed laser and light-emitting diodes phototherapy on isokinetic performance in patients with COPD. Thirteen patients performed muscular endurance tests in an isokinetic dynamometer. The maximum voluntary isometric contraction (MVIC), peak torque (PT), and total work (TW) of the non-dominant lower limb were measured in two visits. The application of phototherapy or placebo (PL) was conducted randomly in six locations of femoral quadriceps muscle by using a cluster of 12 diodes (4 of 905 nm super-pulsed lasers, 0.3125 mW each; 4 of 875 nm LEDs, 17.5 mW each; and 4 of 640 nm LEDs, 15 mW each, manufactured by Multi Radiance Medical™). We found statistically significant increases for PT (174.7 ± 35.7 N · m vs. 155.8 ± 23.3 N · m, p = 0.003) and TW after application of phototherapy when compared to placebo (778.0 ± 221.1 J vs. 696.3 ± 146.8 J, p = 0.005). Significant differences were also found for MVIC (104.8 ± 26.0 N · m vs. 87.2 ± 24.0 N · m, p = 0.000), sensation of dyspnea (1 [0-4] vs. 3 [0-6], p = 0.003), and fatigue in the lower limbs (2 [0-5] vs. 5 [0.5-9], p = 0.002) in favor of phototherapy. We conclude that the combination of super-pulsed lasers and LEDs administered to the femoral quadriceps muscle of patients with COPD increased the PT by 20.2% and the TW by 12%. Phototherapy with a combination of super-pulsed lasers and LEDs prior to exercise also led to decreased sensation of dyspnea and fatigue in the lower limbs in patients with COPD.

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.

Effect of intermittent low-frequency electrical stimulation on the rat gastrocnemius muscle.

Low-frequency neuromuscular electrical stimulation (NMES) has been used as an endurance exercise model. This study aimed to test whether low-frequency NMES increases the phosphorylation of anabolic signaling molecules and induces skeletal muscle hypertrophy, as seen with high-frequency NMES. Using Sprague-Dawley rats, 1 bout of exercise (with dissection done immediately (Post0) and 3 h (Post3) after exercise) and another 6 sessions of training were performed. All experimental groups consisted of high- and low-frequency stimulation (HFS: 100 Hz; LFS: 10 Hz). Periodic acid-Schiff (PAS) staining was conducted to investigate type II fiber activation, and western blot analysis (WB) was conducted to examine whether NMES leads to anabolic intracellular signaling. At first, we examined the acute effect of exercise. PAS staining revealed that glycogen depletion occurred in both type I and type II fibers. WB results demonstrated that p70S6K phosphorylation was significantly increased by HFS, but there was no significant difference with LFS. In contrast, ERK 1/2 phosphorylation was increased by LFS at Post0. In the 6-session training, the wet weight and myofibrillar protein were significantly increased by both HFS and LFS. In conclusion, LFS has a similar anabolic effect for skeletal muscle hypertrophy as HFS, but the mediating signaling pathway might differ.

Vitamin D in exercise: physiologic and analytical concerns.

Despite a wide number of studies performed on the general population, little is known about the Vitamin D status of athletes. A particular influence of many factors, including skin pigmentation, early- or late-day training, indoor training, geographic location and extensive sunscreen use, has been observed in this specific population. The need of supplementation with Vitamin D in athletes is not defined or, when supplementation is needed, even the optimal amount of Vitamin D to be used is not specified. The periodic measurement of Vitamin D is the only procedure capable to define athletes' status. Although various methods for the measurement of Vitamin D are routinely used, they often give discordant and poorly reproducible results; thus, it is necessary to standardize the various methods, in order to have comparable results. In conclusion, current available data indicate both that little is known about the Vitamin D status of athletes and that is still unclear if supplementation could be desirable. Finally, it must be pointed out that all the papers about Vitamin D status should indicate in detail the method used for really allowing a correct interpretation of data.

Red light and the sleep quality and endurance performance of Chinese female basketball players.

CONTEXT: Good sleep is an important recovery method for prevention and treatment of overtraining in sport practice. Whether sleep is regulated by melatonin after red-light irradiation in athletes is unknown. OBJECTIVE: To determine the effect of red light on sleep quality and endurance performance of Chinese female basketball players. DESIGN: Cohort study. SETTING: Athletic training facility of the Chinese People's Liberation Army and research laboratory of the China Institute of Sport Science. Patients or Other Participants: Twenty athletes of the Chinese People's Liberation Army team (age = 18.60 6 3.60 years) took part in the study. Participants were divided into red-light treatment (n = 10) and placebo (n = 10) groups. INTERVENTION(S): The red-light treatment participants received 30 minutes of irradiation from a red-light therapy instrument every night for 14 days. The placebo group did not receive light illumination. MAIN OUTCOME MEASURE(S): The Pittsburgh Sleep Quality Index (PSQI) questionnaire was completed, serum melatonin was assessed, and 12-minute run was performed at preintervention (baseline) and postintervention (14 days). RESULTS: The 14-day whole-body irradiation with red-light treatment improved the sleep, serum melatonin level, and endurance performance of the elite female basketball players (P < .05). We found a correlation between changes in global Pittsburgh Sleep Quality Index and serum melatonin levels (r = -0.695, P = .006). CONCLUSIONS: Our study confirmed the effectiveness of body irradiation with red light in improving the quality of sleep of elite female basketball players and offered a nonpharmacologic and noninvasive therapy to prevent sleep disorders after training.

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

Low-level laser therapy (LLLT) has shown efficacy in muscle bioenergetic activation and its effects could influence the mechanical performance of this tissue during physical exercise. This study tested whether endurance training associated with LLLT could increase human muscle performance in isokinetic dynamometry when compared to the same training without LLLT. The primary objective was to determine the fatigue index of the knee extensor muscles (FIext) and the secondary objective was to determine the total work of the knee extensor muscles (TWext). Included in the study were 45 clinically healthy women (21 ± 1.78 years old) who were randomly distributed into three groups: CG (control group), TG (training group) and TLG (training with LLLT group). The training for the TG and TLG groups involved cycle ergometer exercise with load applied to the ventilatory threshold (VT) for 9 consecutive weeks. Immediately after each training session, LLLT was applied to the femoral quadriceps muscle of both lower limbs of the TLG subjects using an infrared laser device (808 nm) with six 60-mW diodes with an energy of 0.6 J per diode and a total energy applied to each limb of 18 J. VT was determined by ergospirometry during an incremental exercise test and muscle performance was evaluated using an isokinetic dynamometer at 240°/s. Only the TLG showed a decrease in FIext in the nondominant lower limb (P = 0.016) and the dominant lower limb (P = 0.006). Both the TLG and the TG showed an increase in TWext in the nondominant lower limb (P < 0.001 and P = 0.011, respectively) and in the dominant lower limb (P < 0.000 and P < 0.000, respectively). The CG showed no reduction in FIext or TWext in either lower limb. The results suggest that an endurance training program combined with LLLT leads to a greater reduction in fatigue than an endurance training program without LLLT. This is relevant to everyone involved in sport and rehabilitation.

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.

Effects of infrared-LED illumination applied during high-intensity treadmill training in postmenopausal women.

BACKGROUND DATA: Technology and physical exercise can enhance physical performance during aging. OBJECTIVE: The purpose of this study was to investigate the effects of infrared-light-emitting diode (LED) illumination (850 nm) applied during treadmill training. MATERIALS AND METHODS: Twenty postmenopausal women participated in this study. They were randomly divided into two groups. The LED group performed treadmill training associated with infrared-LED illumination (n=10) and the control group performed only treadmill training (n=10). The training was performed during 3 months, twice a week during 30 min at intensities between 85 and 90% of maximal heart rate. The irradiation parameters were 31 mW/cm(2), treatment time 30 min, 14,400 J of total energy and 55.8 J/cm(2) of fluence. Physiological, biomechanical, and body composition parameters were measured at the baseline and after 3 months. RESULTS: Both groups improved the time of tolerance limit (Tlim) (p<0.05) during submaximal constant-speed testing. The peak torque did not differ between groups. However, the results showed significantly higher values of power [from 56±10 to 73±8 W (p=0.002)] and total work [from 1,537±295 to 1,760±262 J (p=0.006)] for the LED group when compared to the control group [power: from 58±14 to 60±15 W (p≥0.05) and total work: from 1,504±404 to 1,622±418 J (p≥0.05)]. The fatigue significantly increased for the control group [from 51±6 to 58±5 % (p=0.04)], but not for the LED group [from 60±10 to 60±4 % (p≥0.05)]. No significant differences in body composition were observed for either group. CONCLUSIONS: Infrared-LED illumination associated with treadmill training can improve muscle power and delay leg fatigue in postmenopausal women.

Effect of linear polarized near-infrared light irradiation and light exercise on muscle performance.

This study aimed to determine the effect of active warm-up by local muscle light exercise and passive warm-up by polarized light irradiation on skin and muscle temperatures and forearm muscle performance (muscle strength, power, endurance, and controlled force-exertion). Ten healthy males performed various grip tests before and after active (local muscle light exercise) and passive (linear polarized near-infrared light irradiation) warm-ups. An active warm-up involved intermittent gripping exercise (contraction: 1 second and relaxation: 1 second) for 10 minutes using a sponge. A passive warm-up consisted of polarized light irradiation to the forearm (superficial digital flexor) for 10 minutes (irradiation: 5 seconds and rest: 1 second). Skin and muscle temperatures were measured during both warm-ups. Skin and muscle temperatures increased significantly after 5 minutes of local muscle light exercise and after 10 minutes of polarized light irradiation. Temperatures were significantly higher after 6 minutes of local muscle light exercise than after 6 minutes of polarized light irradiation. There were no significant differences of muscle strength, power, and controlled force-exertion before and after either warm-up. Average force outputs in all conditions significantly decreased with exertion time, and at 30, 60, 90, and 120 seconds they were higher in both warm-up conditions than in the non-warm-up condition. In conclusion, both warm-ups may contribute to improve muscle endurance performance in the decreasing force phase.

[The strategy of the "useful sun" improves physical endurance and structural adaptation in the myocardium].

The action of solar light transformed by special screens has been studied on CD-1 male mice. In the active control group, mice were irradiated through screens absorbing the UV-component. In the experimental group, screens transforming the UV-component into the orange-red light were used. In the active control, changes in the swimming activity, as compared to the same parameter before irradiation, were manifested much less than in animals of the experimental group. A morphological analysis showed changes in the structure of all cardiomyocyte organelles studied: the relative area of mitochondria in the experimental mice increased by more than 20% compared to intact animals (p < 0.05). A significant increase in the area of the sarcoplasmic reticulum, by 23.4% (p < 0.05), and in the volume of the myofibrillar apparatus, by 19.4% (p < 0.05), was detected. The results of our experiment show that the irradiation with using an additional orange-red component improves the physical endurance 1.5 times and initiates morphogenetic processes in cardiac muscle cells.