Photobiomodulation And Sports: Results Of A Narrative Review Part.A
Mar 18, 2022
Laura Marinela Ailioaie 1 and Gerhard Litscher 2,*
1 Department of Medical Physics, Alexandru Ioan Cuza University, 11 Carol I Boulevard, 700506 Iasi, Romania; lauraailioaie@yahoo.com
2 Research Unit of Biomedical Engineering in Anesthesia and Intensive Care Medicine, Research Unit for Complementary and Integrative Laser Medicine, and Traditional Chinese Medicine (TCM) Research Center Graz, Medical University of Graz, Auenbruggerplatz 39, 8036 Graz, Austria
* Correspondence: gerhard.litscher@medunigraz.at; Tel.: +43-316-385-83907
For more information:ali.ma@wecistanche.com
Abstract
The benefits of photobiomodulation (PBM) have been known for several decades. More recently, PBM applied in sports offers a special chance to support the modeling of performance and recovery. Increasingly complex physical activities and fierce competition in the world of sports generate a state of psycho-emotional and physical stress that can induce chronic fatigue syndrome, failure in physical training, predisposition to muscle damage, physical and emotional exhaustion, etc., for which PBM could be an excellent solution. To evaluate and identify all risk factors and the influence of PBM on health and performance in sport and for a better understanding of its effects, we did a search for “Photobiomodulation and Sports” on PubMed, to update the PBM science applied in sports, and we retained for analysis the articles published from 2014 to date. The term “PBM” is recent, and we did not include previous studies with “low-level laser therapy” or “LLLT” before 2014. In the present research, PBM has been shown to have valuable protective and ergogenic effects in 25 human studies, being the key to success for high performance and recovery, facts supported also by 22 animal studies. PBM applied creatively and targeted depending on sport and size of the level of physical effort could perfectly modulate the mitochondrial activity and thus lead to remarkable improvements in performance.
PBM with no conclusive results or without effects from this review (14 studies from a total of 39 on humans) was analyzed and we found the motivations of the authors from the perspective of multiple causes related to technological limitations, participants, the protocols for physical activity, the devices, techniques and PBM parameters. In the near future, dose-response experiments on physical activity should be designed and correlated with PBM dose-response studies, so that quantification of PBM parameters to allow the energy, metabolic, immune, and neuroendocrine modulation, perfectly coupled with the level of training. There is an urgent need to continuously improve PBM devices, delivery methods, and protocols in new ingenious future sports trials. Latest innovations and nanotechnologies applied to perform intracellular signaling analysis, while examining extracellular targets, coupled with 3D and 4D sports motion analysis and other high-tech devices, can be a challenge to learn how to maximize PBM efficiency while achieving unprecedented sports performance and thus fulfilling the dream of millions of elite athletes.
Keywords: photobiomodulation; sports; fatigue; low-level laser therapy; light emitting diodes; muscle damage; performance; recovery; soreness; super-pulsed lasers
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1. Introduction
It is in the competitive human spirit to look for the best performance in both amateurs and sports professionals. In this search for incredible results and the implementation of new exercises and innovative training, a major role is played by the selection of the latest appropriate ergogenic means designed to improve physical and mental performance, endurance, and recovery after intense muscle training. Due to high competition, always staying on the top for professionals has become increasingly difficult due to permanent facing with the readjustments of the human body to high stress and intense training dictate by the huge tasks of physical activities. To increase muscle strength and endurance in athletes, new means of stimulating and regulating skeletal muscles are needed, in addition to improving hypertrophic and neuromuscular fitness. An essential property of skeletal muscle is contraction, which needs energy and is achieved by sliding actin molecules (thin) on the myosin (thick) filaments, together forming the sarcomere. Myosin head also binds to adenosine triphosphate (ATP), which is the basis of the energy supply for muscle contraction. Myosin can bind to actin only when actin coupling sites are exposed to calcium ions. Tropomyosin covers the myosin-binding sites of the actin molecules, so it must be removed to uncover the binding sites on the actin, a process that also requires energy. Calcium ions will connect to troponin C molecules, modifying the pattern of the tropomyosin and obliging it to disclose the cross-bridge coupling sites on the actin.
Transferring the sodium and potassium ions through the muscle membrane to keep the vital ionic gradients also needs energy, for which the ATP is the main muscle fuel. ATP is the basic energy unit in the physiological enzymatic processes of (Na+/K + ATPase), (Ca2 + ATPase), and the myofilament cross-bridge cycling (myosin ATPase) in the excitable muscle cell membrane. However, the intake of ATP for muscles can last only 1–2 s. Intramuscular deposits of ATP are reduced (~5 mmol per kg wet muscle), and at a score of ATP utilization of 3.7 mmol ATP kg−1 s −1, the muscular activity could last less than 2 s if stocked ATP was the only energy source [1]. Creatine phosphate (CK), which, like ATP contains, a high-energy phosphate bond, is a rapid source of energy for ATP regeneration. CK deposits are also limited and could supply energy for muscle contractions for only 5 to 8 s. The main sources of energy for muscles remain glucose and fatty acids, whose consumption depends on the load and fitness of the subject, as well as the availability of oxygen. ATP production from cytosolic glycolysis, mitochondrial oxidation of beta fatty acids, and the citric acid cycle are tightly regulated and respond quickly to muscle demands for more ATP [2]. The amount of ATP and its supply at the right time during skeletal muscle contraction is essential both in explosive sportive events for noticeably short periods of time (seconds or minutes), for example in sprints and jumps, but also in case of long resistance efforts in which the athlete must prove endurance for hours [1,3]. Photobiomodulation (PBM), formerly known as low-power laser therapy or low-level laser therapy (LLLT), has its new terminology adopted at the joint conference of the North American Association for Light Therapy and the World Association for Laser Therapy in September 2014, with a consensus on nomenclature for photobiomodulation as an ideal term [4]. PBM involves the use of visible and/or infrared laser/light to biologically modulate cellular activity, to improve tissue and cell functions through the activation of cellular enzymes so that the flux of photons is inducing several physiological changes such as increasing ATP production, reduction in inflammation and pain, stimulation of the formation of new muscle fibers, acceleration of angiogenesis, repair, and regeneration of tissues [5,6].
PBM has been shown in several studies to be effective in cell proliferation, stimulating metabolism, reducing inflammation, and promoting tissue healing. Amidst the parameters used, the dose delivered to a certain type of tissue is crucial, because the effects will depend on it: the application of a small dose could lead to an important cellular response, but high doses can inhibit cell proliferation or even induce apoptosis. Among the most replicable consequences of PBM is the systemic decrease in inflammation, very significant for traumatic injuries or joint diseases, lung, and brain conditions [7]. Current studies on the effects of anti-inflammatory PBM at the cellular level are focused mainly on the expression of pro-inflammatory cytokines and on the migration and concentration of macrophages at the site of impact. It is known that the macrophage plays a crucial role during the inflammatory phase; the M1 phenotype has a physiological proinflammatory activity for the defense of the host in the invasion with pathogens, and the M2 phenotype participates in the remedy of injuries in the phase of extinguishing the inflammation [8]. PBM regulates through complex mechanisms a wide range of pro-inflammatory/anti-inflammatory cytokines and the level of polarization of macrophages responsible for an excessive inflammatory response or accelerated tissue healing. Wavelength influences the propagation, flux, and rate of distribution of photons in irradiated tissues, as well as the effectiveness of the non-invasive application of the laser.
The wavelength used by PBM is a valuable parameter in the response to cell proliferation because the wavelength between 600–1070 nm (red/near-infrared (IR)) has the best non-invasive effects. It has been observed that the shorter wavelengths are absorbed by hemoglobin or melanin, producing cellular effects, while the longer wavelengths are absorbed by water, and give the sensation of warmth and induce pain relief [9]. From the first applications, PBM has been used for the treatment of many inflammatory diseases, musculoskeletal disorders, and especially for tissue regeneration and recovery. Intensive development of advanced laser systems—as well as other medical treatment devices—has led to the unprecedented expansion of the multitude of therapy options including stimulating and healing of muscles, tendons, ligaments, joints, etc. but also immunological conditions, the nervous system, as well as targeting the axis of the immune system—muscular system—brain, etc., and all in connection with training and physical exercises. The value of these therapies is the lack of side effects, of addiction, considered as energy methods that precisely address the energy processes inside the cells and what is most valuable, without drugs or toxic consequences.
2. Methodology
From previous randomized and placebo-controlled scientific LLLT studies, it is known that the wavelengths red to near-IR delivered from single laser diodes or clusters, LEDs, or arrangements of both in different impressively adaptable devices can supply energy to the cellular power plants to repair and regenerate muscles, painful joints due to intense physical activity, and restore the physiological balance. Specific muscle characteristics studied previously included parameters such as exhaustion, muscle fatigue, set of repetitions, twisting force impulse, muscle fiber hypertrophy, the degree of muscle damage, such as CK, lactate dehydrogenase (LDH), etc. and remaining muscle pain or delayed onset muscle soreness, as well as the recovery time [10].To evaluate and identify all risk factors and the influence of PBM on health and performance in sport and for a better understanding of its effects in high elite athletes, we conducted a search for “Photobiomodulation and Sports” on PubMed, to update the PBM science applied in sports, and we retained for analysis all the articles published from 2014 to date. The term “PBM” is recent, and we did not include previous studies with “low-level laser therapy” or “LLLT” before 2014 [4]. The search retrieved 90 studies, of which 29 studies were excluded (reviews, editorials, cellular studies, sports-related pathologies, inadequate studies due to lack of randomization or control group, duplicates, etc.), and the difference (61 studies) was included in the analysis (Figure 1). Of the last 61 studies considered in this review, 39 were in human subjects, and 22 were experimental animal studies. Analysis of research in human subjects revealed positive effects of PBM in 25 studies, which included 797 participants, and 14 studies did not indicate any relevant effect of PBM compared to control groups.
3. PBM Applied in Sports in Different Settings and Conditions
3.1. Positive Effects of PBM
Applying PBM both before and after training can have positive effects, so we classified the studies into applications of PBM before, after, before, and after, and in experimental laboratory conditions when participants were running on the treadmill. There were 39 randomized, placebo-controlled studies on humans, of which only 25 (with 797 subjects) had positive results due to PBM applied to various light physical activities or intensive training, before, after, both before and after, or under experimental laboratory conditions, of which 21 are summarized in Table 1, and four other studies with PBM and simultaneously applied static magnetic field are mentioned in the final discussions
In order to set out the most favorable dose of PBM, Antonialli et al. [11] evaluated skeletal muscle efficiency and the recuperation after exercise including 40 vigorous male volunteers, but physically unprepared, into a randomized, double-blind, placebo-controlled study using 12 cluster diodes (4 IR laser diodes of 905 nm, 4 IR LEDs of 875 nm and, 4 red LEDs of 670 nm). They administered 10, 30, and 50 J, or placebo, in six points on the front of the thighs, using only one PBM treatment immediately after pre-exercise maximal voluntary contraction (MVC), and finally analyzing MVC, delayed-onset muscle soreness (DOMS), and the creatinine kinase (CK). Ratings were effectuated before, 1 min, 1 h, 24 h, 48 h, 72 h, and 96 h after the procedures to provoke muscular tiredness. PBM enhanced MVC from immediately after to 96 h after exercise with 10 or 30 J doses, remarkably diminished DOMS with 30 J dose from 24 h to 96 h after exercise, and with 50 J dose from immediately after to 96 h after exercise; and significantly decreased CK activity with all PBM doses, in comparison to the placebo group, concluding that the 30 J dose was the best. In another study, Vanin et al. [12] evaluated the effects of 810 nm/200 mW PBM applied also in six sites on quadriceps with a cluster with only 5 diodes, applying 10, 30, or 50 J in a randomized, double-blind, placebo-controlled study in 28 high-level soccer athletes, also to identify the optimal dose for best recovery and performance. Researchers assessed MVC, DOMS, CK activity, IL-6 expression, before and after 1 min, 1 h, 1 day to 4 days, after the protocol to trigger the muscular exhaustion. PBM increased MVC from immediately after exercise to 24 h with 50 J dose, and from 1 day to 4 days with 10 J dose; it decreased CK and IL-6 with better results in favor of 50 J dose and had no effect on DOMS. Authors concluded that pre-exercise PBM with 50 J energy dose remarkably rose the performance and reduced the biochemical markers linked to damage and inflammation in the skeletal muscle system.
Also in athletes, but in an anaerobic field test using a randomized, crossover, double-blind, placebo-controlled clinical trial in twelve male high-level rugby players, Pinto et al. [13] demonstrated the effects of PBMT in improving performance and speeding up the rehabilitation time during the Bangsbo sprint test (BST). There were no interventions before BST in the familiarization phase (week 1) but in weeks 2 and 3, pre-exercise PBMT (at 17 points of each leg, employing a cluster with 12 diodes (4 super-pulsed IR laser diodes of 905 nm, 4 IR LEDs of 875 nm, and 4 red LEDs of 640 nm, 30 J per site) or placebo, was randomly delivered to every athlete. As a result, PBMT improved the average sprint time and fatigue index in BST and outstandingly fall down the percentage of blood lactate levels to 3, 10, 30, and 60 min after BST, initiating a novel pathway for large-scale applications of PBMT in real sports conditions. The best PBMT output power for skeletal muscle recovery was identified by AR de Oliveira et al. [14] in a randomized, double-blind, placebo-controlled study involving 28 high-level football players. PBMT was applied before the eccentric contraction protocol with a cluster also with five diodes (810 nm, 10 J dose), but three different output powers (100, 200, 400 mW per diode) or placebo, at six sites of the knee extensors. Voluntary maximal isometric contraction (MIVC), DOMS, CK and lactate dehydrogenase, inflammation (IL-1β, IL-6, and TNF-α), and oxidative stress (catalase, superoxide dismutase, carbonylated proteins, and thiobarbituric acid) were evaluated before isokinetic exercise, as well as after 1 min and 1 h to 96 h. PBMT increased MIVC and decreased DOMS and the biochemical marker levels with the best results for 100 mW output power per diode (500 mW in total) in improving performance and post-exercise restoration. Rossato et al. [15] aimed to identify the effects of two different time responses on knee extensor fatigue in sixteen male volunteers, distributed to perform the same protocol in 5 sessions.
PBMT was applied to the knee extensor (9 sites, 30 J per site). MVC was evaluated before and after isokinetic fatigue associated with electromyography (root mean square [RMS] and median frequency [MF]). Time effect was observed for peak torque (PT), RMS, and MF. The effect of treatment was checked for PT, and 6 h before + immediately before the condition showed higher PT during MIVC (pre to post) than control or placebo. Applying PBMT with 6 h + directly before exercises is capable to diminish tiredness. To test PBMT effects on futsal players’ performance and recovery, De Marchi et al. [16] included six professional athletes in a randomized, triple-blinded, placebo-controlled, crossover clinical trial. PBMT was performed 40 min before matches at 17 points of every leg, also employing a cluster with 12 diodes (4 IR laser diodes of 905 nm, 4 IR LEDs of 875 nm, and 4 red LEDs of 640 nm, 30 J per site). Blood samples were collected before treatments, immediately after the matches, and 48 h after (evaluated for CK, LDH, blood lactate, and oxidative damage of lipids and proteins). Time spent by athletes on the pitch and the distance covered were video quantified. PBMT significantly increased the time of staying in the pitch and determined a meaningful improvement in all the evaluated biochemical markers, but without any statistically significant difference in the mileage. Concluding, pre-exercise PBMT can successfully increase the workout and speed up the rehabilitation process of high-level futsal players.
Because muscle tiredness is an inherent hazard for hamstring stretch lesions in soccer players, Dornelles et al. [17] investigated the effects of PBMT (300 J per thigh or placebo on the hamstrings, before the match) on twelve young male amateur soccer players in a randomized, crossover, double-blinded, placebo-controlled trial, assessed in two sessions at least at 7-day apart. Muscle endurance and useful workout were evaluated through isokinetic dynamometry and countermovement jump (CMJ) tests, respectively, before and immediately after the match. PBMT had beneficial effects on hamstring eccentric peak torque, hamstring-to-quadriceps torque ratio, and the CMJ height, respectively, compared to placebo, attenuating hamstring muscle tiredness, and thus hindering hamstring stretch injuries, which usually occur in football players. PBM before neuromuscular electrical stimulation (NMES) is a remarkably interesting topic, investigated in a randomized, double-blind crossover trial by Jówko et al. [18] on twenty-four moderately active, healthy young men, who received 45 electrically evoked tetanic, isometric contractions of the quadriceps, preceded by PBM or placebo-PBM. The impact of PBM on muscle impairs and causes oxidative stress, as well as the return to a normal state of the muscular function after a single session of NMES, quantified by the maximal isometric voluntary muscle torques, pain, and blood samples analyzed for the muscle impairment (CK), and inflammation (C-reactive protein), were assessed from baseline to 96 h post-intervention.
PBM had a shielding effect on NMES-induced fall in enzymatic antioxidant protection and cut the duration of inflammation, but did not affect lipid peroxidation, muscle impairment, or restoration after NMES. The action of pre-exercise PBMT to increase workout, speed up recuperation and attenuate the oxidative stress were examined in twenty-two male high-level soccer players treated with IR PBMT or placebo prior to a progressive running test (ergo-spirometry) until exhaustion, by Tomazoni et al. [19] in a randomized, triple-blind, placebo-controlled crossover trial (identical group). PBMT enhanced the VO2max, fatigue time, volume and time for both anaerobic and aerobic threshold appearance, and diminished CK and LDH activities, as well as TBARS, IL-6, and carbonylated protein levels; it increases SOD and CAT activities so that PBMT before exercise plays an important antioxidant effect and therefore improves athletic presentation and the post-exercise regeneration. Da Cunha et al. [20] investigated the effects of PBM and NMES on muscle endurance, jumps’ frequency and abilities, general reactions, assessed at baseline and during follow-up at 6 and 8 weeks in a study including thirty-six volleyball athletes, randomized into three groups: control, pre-exercise PBM (IR, 850 nm, CW, 0.8 J/cm2, 6 J/point, total energy equal 36 J) and operational NMES on quadriceps femoris as a muscular workout (1 kHz base, 70 Hz modulation, highest intensity supportable).
The greatest increase in dominant lower limb endurance was in the NMES group, as opposed to control, but for non-dominant lower limbs, the increase was present in both PBM and NMES groups (highest effect), as well as better skills to jump in the last two groups, for which muscle-stamina growth kept on for two weeks after the end of the workout, in comparison to the control. In another study, Rossato et al. investigated the effects of PBMT applied 6 h before and immediately before exercise with a cluster of 5 IR lasers (850 nm) and 28 LEDs, as follows: 12 red LEDs (670 nm), 8 IR LEDs (880 nm) and 8 IR LEDs (950 nm) on quadriceps, in a randomized, crossover, double-blind placebo-controlled study on eighteen physically active men during a complex isokinetic exercise protocol of knee extensions. It was found that exercise performance was not affected by PBMT (135 J, 270 J, or 540 J) compared with placebo, but all doses of applied PBMT led to presumptive positive effects on isometric peak torque, concentric peak torque, and concentric work compared to placebo, facilitating the same total work with less fatigue, i.e., additional sets would be possible for a higher training volume [21]. Zagatto et al. [22] have evaluated in a randomized, double-blind, placebo-controlled research, the influence of 810 nm PBM applied on the adductors directly after each physical daily workout, on inflammation, muscle impairment, and operation capacity in twenty young water polo players.
Daily, before training, the physical performance was evaluated by P200 (intense swimming of 200 m) and a 30 CJ (30 s cross-jump test). Blood tests were performed for interleukins (IL) and muscle damage both before and after the physical protocol. There was no important shift in P200 in the PBMT group compared to placebo, but there was a moderate improvement in 30 CJ. IL-1β and TNF-alpha had elevated values in the PBM group at 48 h after the last treatment, compared to pre, 0, and 24 h, but did not differentiate in the two groups. IL-10 slightly increased over time in the placebo group compared to the PBM group, where creatinine kinase decreased significantly, but no important variation in lactate dehydrogenase was observed. PBM had no important effect on inflammation and muscle damage, with only a medium impact on performance. Failure of reliable results could be caused by the undersized photo biostimulation area. PBMT and cryotherapy alone or combined for skeletal muscle rehabilitation after eccentric contractions of knee extensors were applied by de Paiva et al. [23] in 50 healthy male volunteers, randomly distributed into five groups (PBMT, cryotherapy, cryotherapy + PBMT, PMBT + cryotherapy, or placebo) for a double-blinded, placebo-controlled trial to study MVC, DOMS and the muscle damage (CK). Estimations were conducted at the starting point, immediately after, and from 1 h to 96 h, at each 24 h interval. Comparative therapies were applied 3 min after exercise and repeated every 24 h until 72 h. PBMT (905 nm super pulsed laser and 875 and 640 nm LEDs) and cryotherapy by ice packs on pliable caoutchouc were utilized.
The best for post-exercise recovery with better MVC diminished DOMS, and CK activity from 24–96 h was singular PBMT, compared to placebo, cryotherapy, and cryotherapy + PBMT. In the PBMT + cryotherapy lot, the influence of photobiomodulation was reduced but proved important betterment in MVC, diminished DOMS and CK activity. Singular cryotherapy and cryotherapy + PBMT were comparable to placebo. Therefore, only PBMT alone could best enhance the post-physical recovery to original physiological degrees, one day after high-intensity eccentric exercises. The efficacy of PBMT and cryotherapy, single or mixed, for muscle rehabilitation after the administration of muscular soreness exercises, was one year later investigated by De Marchi et al. [24] who randomly divided forty volunteers into five groups: placebo (PG); PBMT (PBMT), cryotherapy (CG), cryotherapy-PBMT (CPG), and PBMT-cryotherapy (PCG), which underwent a protocol of four physical sessions every 24 h, measuring their MVC and testing the blood in the pre-exercise period and at 5 and 60 min post-exercise, as well as 24, 48, and 72 h later. In the first session, with a 5 min delay, it was applied 2 min PBMT and/or cryotherapy, after the MVC test. Significant increases in MVC capacity in PBMT, CPG, and PCG, compared with PG and CG, as well as a dramatic reduction in concentrations of oxidative damage biochemical markers in all muscle groups and muscular lesions (CK) in PBMT, PCG, and CPG, were registered compared with PG. PBMT really has a higher output in muscle rehabilitation than cryotherapy, which, when simultaneously applied, reduces the effectiveness of PBMT.
Recently, Vassão et al. [25] applied PBMT with a cluster consisting of 14 LEDs, as follows: 7 red diodes (630 nm) and 7 IR diodes (850 nm) on biceps brachii muscles in 32 healthy male participants randomly distributed into 3 groups: red PBM group (RPG), infrared PBM group (IPG) and control group (CG). There were analyzed the muscle fatigue using surface electromyography (EMG), blood lactate concentration, and the rate of perceived exertion (RPE) using the Borg Scale. Comparisons between groups pointed out that electromyography fatigue index decreased in the control group, but RPE and lactate concentrations increased significantly in all groups. There was no significant difference between red and infrared PBM in the reduction in muscle fatigue, but the electromyography fatigue index delta value was greater in the IPG compared with the CG, suggesting that infrared could be more effective than red in decreasing muscle fatigue. Consecutive stimulation with PBMT (180 J) for three successive days on the bilateral femoral quadriceps with different wavelengths: infrared (IR 940 ± 10 nm), red (RED 620 ± 10 nm), mixed red and IR (RED/IR 620 + 940 nm) or placebo, on 48 male cyclists with a mean age of 33.77 years, subjected to an assessment by an incremental test, VO2max, blood lactates, exercise perception, IR detection to study heat distribution in muscles and isokinetic summing up, was performed by Carvalho et al. [26]. For 7 days long, there were accomplished reassessments 24 h from the moment of last praxis. There were no important disparities in the examined parameters under the exploratory setup. PBMT with no connection to workout was unsuccessful in improving the cyclists’ goal.
Still, applying two wavelengths reveals higher success. Although PBM with lasers and/or LEDs on sports perfecting has been extensively investigated, not many experiments have explored the impact on strength muscular workout regarding the most favorable time for stimulation. Vanin et al. [27] randomly divided forty-eight male volunteers (18–35 years old) into four groups, who executed a robust workout, and were stimulated with PBM and/or placebo in advance, and/or after each session, using a band of probes (4 laser diodes of 905 nm, 4 IR LEDs of 875 nm, and 4 red LEDs of 640 nm). Time was 12 weeks with measurements of peak torque touched in MVC, the load in 1-RM test, and the circumference of the thigh at baseline, 4 weeks, 8 weeks, and 12 weeks. Volunteers treated with PBM before, and placebo after a workout, manifested important shifts in MVC and 1-RM tests for legs, compared to other groups. Safe and without adverse effects, PBM has the capacity to rise endurance, when used before physical activities, with extra benefits in post-lesions recovery. Feliciano et al. evaluated the effects of laser irradiation on muscle injury markers after resistance exercise in a double-blind, placebo-controlled study on 22 physically active men who were randomized into two groups: laser (n = 11) and placebo (n = 11). Laser irradiation (808 nm; 100 mW; 35.7 W/cm2, 357.14 J/cm2 per point) was applied to the arms, 1 J per point for 10 s at four points of the brachial biceps of each arm, or placebo, between each set of biceps curl exercise. The following parameters were investigated: creatine kinase (CK) activity and maximal strength performance (1 RM) before, immediately after, 24 h, 48 h, and 72 h after the exercise-induced muscle damage protocol.
Results suggested a partial attenuation of muscle injury when laser irradiation was used during exercise intervals. Maximum CK activity was attenuated after 72 h in the laser group compared to placebo, but there was no obvious positive effect on strength performance recovery [28]. De Brito Vieira et al. investigated the effects of LLLT (808 nm, 100 mW, 4 J/point), or placebo, applied to quadriceps femoris muscles between sets, and after the last series of intense exercises on fatigue resistance via the number of maximum repetitions (RM) and the electromyography fatigue index (EFI), in a randomized, double-blind, crossover trial with placebo. The participants, seven young men, clinically healthy, were allocated into two groups: active laser and placebo laser. Both groups were assessed at baseline and until the end of the study, registering the number of maximum repetitions (RM) of knee flexion extension in conjunction with EFI recorded by median frequency (MF). After 1 week (washout period), all volunteers were exchanged among groups, and then all assessments were repeated. LLLT increased the maximum number of RM, comparatively with the control group. For both groups, MF significantly decreased for all muscles, comparing pre-and post- evaluations at baseline and end-point. Heart rate between groups had no statistical significance. LLLT increased RM and reduced EFI, compared with the placebo group, which is helpful for high performance that demands a fast return to a normal state and less tiredness [29]. Recently, Florianovicz et al.—in a randomized controlled trial—studied the effects of two distinct PBMT protocols (red 660 nm vs. infrared 830 nm) combined with a blood flow restriction (BFR) training arrangement in wrist extensor muscles on the handgrip, wrist extension force, and electromyographic comportment. Fifty-eight volunteers (clinically healthy women, aged 18–25 years old) were randomly divided into 4 groups: (1) control; (2) BFR (strengthening with blood flow restriction); (3) 660 nm + BFR; and (4) 830 nm + BFR.
The hypothesis was that PBMT + BFR would increase muscle strength gain. Handgrip strength, wrist extensor muscle strength, and electromyography (EMG) of the radial carpal extensor muscle were recorded. A statistically significant increase was obtained for handgrip strength in the 660 nm group compared with the 830 nm group, and for wrist extensor strength in the 660 nm and BFR groups compared with the control group. The best increase was found for the 660 nm (red) group comparatively with the control, BFR, and the 830 nm (IR) group. Joining PBMT (660 nm) and BFR was effective for growing the handgrip strength of the wrist extensors, related to an enhancement of the electromyographic behavior [30]. Miranda et al. [31] projected in a laboratory setting, a cross-sectional study that included 20 unprepared and inexperienced male participants to receive PBMT with super pulsed lasers combined with LEDs and to evaluate the muscle efficiency resulting from the gradual cardiopulmonary attempt on the treadmill. Subjects were administered PBMT with a 12-diode cluster in 17 points (30 J/site) on each lower limb, either with combined super pulsed lasers and LEDs, or with placebo at one session, and vice versa at the next session, and completed a cardiopulmonary test on a treadmill each time. They were evaluated for: distance traveled, time to exhaustion, and pulmonary ventilation, all three parameters that increased after effective PBMT, as well as for the dyspnea score, which decreased for real PBMT, compared to placebo. A synthesis of the multitude of interdependent positive effects of PBM action in physical activities and sports, especially the plethora of ergogenic and protective properties, scientifically demonstrated by the positive studies analyzed, is illustrated in the original diagram designed and presented in Figure2
Photobiomodulation from red to near-infrared had ergogenic effects by increasing performance, muscle strength, speed of muscle adaptation, ventilation rate, time to onset muscle soreness, time to exhaustion, effects of aerobic training, stress resistance, and speed of recovery As protective effects, PBM decreased oxidative stress, muscle fatigue, blood lactate levels, inflammation (IL-1, IL-6, TNFα), oxygen deficit, dyspnea, losses during periods without training, and muscle injuries. PBM modulates renal and metabolic functions.
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