Neurotransmitter release changes induced by low power 830 nm diode laser irradiation on the neuromuscular junctions of the mouse

Feasibility study of a LED light irradiation device for the treatment of chronic neck with shoulder muscle pain/stiffness

Neck with shoulder muscle stiffness/pain is a common disorder. Commonly used physical therapy, pharmacotherapy, acupuncture, and moxibustion only temporarily alleviate the disorder in most cases, thus the disorder often recurs. Low power laser therapy is often used for neck and shoulder stiffness/pain and has been effective in clinical trials. In this study, we evaluated the safety and effectiveness of a newly developed self-care device for disorders including neck with shoulder muscle stiffness/pain. The device incorporates light-emitting diodes (LEDs), which are safer than lasers, as its light source. Ten adults with neck with shoulder muscle stiffness/pain were subject to LED irradiation (wavelength 780 nm ± 15 nm, output 750 mW, power density 3.8 W/cm2, energy density 5.7×102 J/cm2) for 3 minutes on the affected shoulder at a standard acupuncture point (GB21, Jianjing). Immediately after irradiation, the subjective symptoms of the neck with shoulder muscle stiffness and pain evaluated by a visual analog scale were improved from 58.3 mm ± 18.7 mm to 45.5 mm ± 21.5 mm and from 45.8 mm ± 23.3 mm to 39.4 mm ± 21.8 mm, respectively. The symptoms further improved after 15 minutes of irradiation. The skin temperature at the irradiated point increased from 34.3°C ± 1.1°C to 41.0°C ± 0.7°C. The increase in skin temperature was observed within approximately 5 cm of the irradiated area. There was no effect on the heart rate variability, a measure of the autonomic nervous system; however, the baroreflex sensitivity was slightly increased. No irradiation-related adverse skin events were observed. Our LED irradiation device was found to be safe, and it improved the subjective symptoms of muscle stiff neck with shoulders.

Effectiveness of High Power Laser Therapy on Pain and Isokinetic Peak Torque in Athletes with Proximal Hamstring Tendinopathy: A Randomized Trial

Athletes such as long-distance runners, sprinters, hockey, and/or football players may have proximal hamstring tendinopathy (PHT). Laser therapy has been shown to be effective in tendinopathies. High power laser therapy (HPLT) is used for the treatment of several musculoskeletal conditions; however, its efficacy on PHT has not been investigated. This study is aimed at examining the effects of HPLT on pain and isokinetic peak torque (IPT) in athletes with PHT. The two-arm comparative pretest-posttest experimental design was used with random allocation of 36 athletes aged 18-35 years into two groups (experimental and conventional group). The experimental group included the application of HPLT for 3 weeks. The conventional group included treatment with a conventional physiotherapy program including ultrasound therapy, moist heat pack, and home exercises for a total of 3 weeks. Pain and IPT of the hamstring muscle were measured before and after the application of the intervention. Pain score decreased, and IPT increased significantly (p < 0.05) after application of HPLT, by 61.26% and 13.18%, respectively. In the conventional group, a significant difference (p < 0.05) was observed in pain scores only, which decreased by 41.14%. No significant difference (p > 0.05) was observed in IPT in the conventional group. When HPLT was compared with conventional physiotherapy, a significant difference was found in pain scores only. HPLT for 3 weeks was found to be effective in improving pain in athletes with PHT. However, no significant difference was found between HPLT and conventional physiotherapy (US, moist heat, and home exercises) in improving the IPT of the hamstring muscle.

Acute Photobiomodulation Effects Through a Cluster Device on Skeletal Muscle Fatigue of Biceps Brachii in Young and Healthy Males: A Randomized Double-Blind Session

Objective: The aim of this study was to investigate and compare the acute effects of red and infrared photobiomodulation (PBM) using a cluster device on biceps brachii muscle fatigue in young and healthy males. Background: Vigorous physical activity could lead to muscle fatigue, which compromises motor control and muscle strength and consequently impairs performance. The positive effects of PBM in reducing fatigue onset have been highlighted. However, the better wavelength with cluster devices is not yet established. Methods: A randomized double-blind session was used. Thirty-two young and healthy males were randomized into the control group (CG), red PBM group (RPG), and infrared PBM group (IPG). A PBM cluster device [7 visible diodes (630 nm), 7 infrared diodes (850 nm), 100 mW/diode, 2 W/cm² power density, 91 J/cm² energy density, 4 J per point, 28 J total energy, and 40 sec] was applied after muscle fatigue. Muscle fatigue was analyzed by surface electromyography (EMG) recorded from the long head of biceps brachii, blood lactate concentration, and evaluation of the rate of perceived exertion (RPE) using the Borg Scale. The fatigue protocol consisted of a maximum voluntary isotonic contraction of elbow flexion-extension with 75% of one-repetition maximum until exhaustion. The Borg Scale was applied before and at the end of the experiment to measure the RPE. The electromyography fatigue index (EMGFI) was calculated by windows of median frequency from EMG data. Results: EMGFI, blood lactate concentration, and RPE showed no intergroup statistical difference, except the EMGFI delta value that showed a difference between IPG and CG, with a greater value in the CG. However, intragroup comparisons showed that EMGFI decreased in the CG and RPE and lactate concentration increased significantly in all groups. Conclusions: There was no difference between red and infrared PBM in reduction of biceps brachii fatigue. However, the EMGFI delta value was greater in the IPG compared with the CG, suggesting that infrared can be more effective in reducing biceps brachii fatigue.

Effects of High Intensity Laser Therapy in the Treatment of Tendon and Ligament Injuries in Performance Horses

Simple Summary

High intensity laser therapy (HILT) has been introduced as a non-invasive therapy for musculoskeletal diseases in horses, but little is known about the impact of HILT in the treatment of tendon and ligament injuries. The aim of this study was to evaluate the effects of HILT on tendon and ligament injury treatment in horses. Twenty six horses with tendinopathies and desmopathies were randomly assigned to a HILT treated or to a non-treated group. Each horse from the treatment group underwent a series of fifteen HILT treatments. Clinical and ultrasound assessments were carried out. Clinical evaluation included: pain, swelling and lameness of the affected limb. The ultrasound examination evaluated lesion echogenicity and lesion percentage. In our study, HILT promoted analgesic and anti-oedema effects, with visual lameness reduction in horses with tendon and ligament injuries, and reduced lesion percentage but did not influence change in lesion echogenicity. HILT appears justifiable for its anti-inflammatory effects and can be used as a physiotherapeutic technique for supportive treatment of tendon and ligament injuries in horses. The introduction of laser therapy to veterinary medicine, particularly to analgesic therapy in horses, gives hope of improving the quality of life of patients with chronic musculoskeletal pain.

Abstract

The aim of this study was to evaluate the effects of high intensity laser therapy (HILT) on tendon and ligament injury treatment in horses. Twenty six horses with tendinopathies were randomly assigned to a HILT treated or to a non-treated group. Each horse was subjected to the same rehabilitation programme. Horses from the treatment group underwent a series of fifteen HILT treatments with the same parameters. Clinical and ultrasound assessments were performed by the same veterinarian and were carried out before (day 0), during (day 13–15) and after treatment (day 38–40). Clinical evaluation included: pain, swelling and lameness of the affected limb. The ultrasound examination evaluated lesion echogenicity and lesion percentage. After the treatment, pain, swelling and lameness were significantly improved by HILT compared with the control group (p = 0.023, 0.008 and 0.044, respectively). No significant changes were found in lesion echogenicity degree between both groups in measurements taken during treatment (p = 0.188) and after treatment (p = 0.070). For lesion percentage reduction, the statistical modelling showed a significant improvement in the HILT group compared with the control group during (p = 0.038) and after treatment (p = 0.019). In conclusion, HILT promoted analgesic and anti-oedema effects, with visual lameness reduction in horses with tendon and ligament injuries, and reduced lesion percentage but did not influence change in lesion echogenicity.

The effect of high intensity laser therapy in the management of painful calcaneal spur: a double blind, placebo-controlled study

To evaluate the effect of high-intensity laser therapy (HILT) in patients with calcaneal spur. The patients were randomized to receive either HILT + exercise (n = 21) (five times a week for a period of 3 weeks) or placebo HILT + exercise (n = 21) (five times a week for a period of 3 weeks). Pain severity (with visual analog scale (VAS) and with Roles and Maudsley score (RMS)), functionality (with Foot and Ankle Outcome Score (FAOS)), plantar pressure measurement, and quality of life (with short form-36 (SF-36)) of the patients were evaluated at baseline, at 4 weeks, and 12 weeks. A significant improvement in the VAS (p < 0.001), RMS (p < 0.001), and most of the SF-36 subgroup scores (p < 0.05) and most of the FAOS subgroup scores (p < 0.05) at 4 and 12 weeks after treatment was achieved in both groups. Besides, there was no significant difference in VAS (p > 0.05) and RMS (p > 0.05) between the groups. FAOS symptoms (p = 0.022) and quality of life (p = 0.038) subgroups were higher in the placebo group at 12 weeks. Significant improvements were observed in dynamic pedographic measurements in the HILT group (p < 0.05), and dynamic measurement values were significantly higher in the HILT group compared to placebo group (p < 0.05). Although the evaluation parameters, except dynamic pedographic measurements, have improved in both groups, our study results showed no superiority of HILT over placebo. To conclude, when the main complaint is pain in patients, only exercise therapy can be an economical, practical, and reliable treatment.

Efficacy of pulsed high-intensity laser therapy on pain, functional capacity, and gait in children with haemophilic arthropathy

AIM

The aim of this study was to evaluate the effects of pulsed high-intensity laser therapy (HILT) on pain, functional capacity, and gait in children with haemophilia.

METHODS

Thirty children with haemophilia type A with ages ranging from 9 to 13 years were selected for this study. They were assigned randomly, into two equal treatment groups. The laser group received the traditional physical therapy programme plus active laser (total energy of 1500 J through three phases/3 sessions/week), whereas the placebo group received the same physical therapy programme plus placebo laser over three consecutive months. Baseline and post-treatment assessments used the visual analogue scale (VAS) to evaluate pain, a 6-min walk test (6MWT) to evaluate functional capacity, and the GAITRite^® system to evaluate gait parameters.

RESULTS

Children in the laser group showed significant improvement in pain, functional capacity, and gait parameters compared to those in the placebo group (p < 0.05). Post-treatment functional capacity for the laser and placebo groups were 316.6 ± 35.27 and 288 ± 43.3 m, respectively.

CONCLUSIONS

HILT is an effective modality in reducing pain, increasing functional capacity, and improving gait performance in children with haemophilic arthropathy. Implications for Rehabilitation Haemophilic arthropathy due to recurrent joint bleeding leads to physical, psychological, and socioeconomic problems in children with haemophilia and reduces their quality of life. Early physiotherapeutic interventions help to prevent and treat the sequelae of recurrent haemarthrosis. High-intensity laser therapy has been introduced as non-invasive and an effective physiotherapy modality for rapid pain control, with consequent improvement in children's quality of life. High-intensity laser therapy should be used as an adjunct to exercise programme in the rehabilitation of children with haemophilic arthropathy.

Effects of low-level laser therapy (LLLT 808 nm) on lower limb spastic muscle activity in chronic stroke patients

A cerebrovascular accident (CVA) may affect basic motor functions, including spasticity that may be present in the upper extremity and/or the lower extremity, post-stroke. Spasticity causes pain, muscle force reduction, and decreases the time to onset of muscle fatigue. Several therapeutic resources have been employed to treat CVA to promote functional recovery. The clinical use of low-level laser therapy (LLLT) for rehabilitation of muscular disorders has provided better muscle responses. Thus, the aim of this study was to evaluate the effect of the application of LLLT in spastic muscles in patients with spasticity post-CVA. A double-blind clinical trial was conducted with 15 volunteer stroke patients who presented with post-stroke spasticity. Both males and females were treated; the average age was 51.5 ± 11.8 years old; the participants entered the study ranging from 11 to 48 months post-stroke onset. The patients participated in three consecutive phases (control, placebo, and real LLLT), in which all tests of isometric endurance of their hemiparetic lower limb were performed. LLLT (diode laser, 100 mW 808 nm, beam spot area 0.0314 cm(2), 127.39 J/cm(2)/point, 40 s) was applied before isometric endurance. After the real LLLT intervention, we observed significant reduction in the visual analogue scale for pain intensity (p = 0.0038), increased time to onset of muscle fatigue (p = 0.0063), and increased torque peak (p = 0.0076), but no significant change in the root mean square (RMS) value (electric signal in the motor unit during contraction, as obtained with surface electromyography). Our results suggest that the application of LLLT may contribute to increased recruitment of muscle fibers and, hence, to increase the onset time of the spastic muscle fatigue, reducing pain intensity in stroke patients with spasticity, as has been observed in healthy subjects and athletes.

Comparison of High Intensity Laser and Epicondylitis Bandage in the Treatment of Lateral Epicondylitis

Objectives

This study aims to investigate the effects of high-intensity laser therapy (HILT) and epicondylitis bandage treatment in patients with lateral epicondylitis (LE).

Patients and methods

Sixty-five patients with unilateral LE (18 males, 47 females; mean age 46.5±8.1 years; range 30 to 61 years) with unilateral complaints were included. Patients were randomly assigned into two treatment groups. The first group (n=31) was treated with HILT for 10 sessions, while the second group (n=34) used only LE bandage for treatment. The patients were assessed for handgrip strength, pain, disability, and quality of life at baseline and sixth week after treatment by using visual analog scale, the Disabilities of the Arm Shoulder and Hand questionnaire, and Short-Form 36 (SF-36).

Results

Both groups showed significant improvement in all evaluated parameters including pain scores, hand grip strength, disability, and SF-36 scores at sixth week after the treatment (all p<0.05). A comparison of percentage changes in parameters between treatment groups did not show a significant difference, except for resting visual analog scale (p=0.036) and SF-36 physical component subscale (p=0.049) scores which indicated better improvement in HILT group.

Conclusion

Our findings showed significant improvement in handgrip strength, pain, disability, and quality of life parameters in both groups. However, HILT produced better resting visual analog scale and SF-36 physical component subscale scores compared to LE bandage.

CHELT therapy in the treatment of chronic insertional Achilles tendinopathy

The application of laser therapy on soft tissue is used for pain relief, anti-inflammation action and biostimulation. The efficiency of High Energy Laser Therapy has not yet been studied on Achilles tendinopathy. The aim of the study is to evaluate the effectiveness of a flow of Cold air and High Energy Laser Therapy (CHELT) versus Extracorporeal Shock Waves Therapy (ESWT) in the treatment of Achilles tendinopathy. In this prospective, clinical trial, 60 subjects affected by insertional Achilles tendinopathy were enrolled and randomized to CHELT (30 subjects) or to ESWT (30 subjects). In CHELT group the patients received ten daily sessions of 1,200 J and 12 W of laser therapy (wavelength of 1,084, 810 and 980 nm) added to a flow of cold air at -30 °C. In the ESWT group, the patients received three sessions at 3- to 4-day intervals of 1,600 impulses with an energy flux density (EFD) of 0.05-0.07 mJ/mm(2). Both groups of participants performed stretching and eccentric exercises over a 2-month period. The visual analogue scale (VAS), the Ankle-Hindfoot Scale, and the Roles and Maudsley Score were measured before treatment (T0), and at end of the treatment session (T1) and 2 (T2) and 6 months (T3) after treatment during the follow-up examinations. In both groups, we found a statistically significant improvement of the VAS at T1, T2 and T3 (p < 0.01). The difference between the two groups was statistically significant in favour of the CHELT group (p < 0.001). At 2 months, the CHELT group was statistically better for Ankle-Hindfoot Scale and the Roles and Maudsley Score (p < 0.05) and at 6 months only for the Roles and Maudsley Score (p < 0.001). High Energy Laser Therapy gave quicker and better pain relief. It also gave the patient a full functional recovery and greater satisfaction.

Phototherapy effect on the muscular activity of regular physical activity practitioners

Clinical investigations have demonstrated the effectiveness of phototherapy on the muscle activity. The aim of this study was to investigate the effect of low-level laser therapy (LLLT) on the tibialis anterior muscle of regular physical activity practitioners by electromyographic, biomechanical, and biochemical (lactate) analysis. Double-blind controlled clinical trials were conducted with 12 healthy females, regular physical activity practitioners, between 18 and 30 years. The LLLT application (780 nm, 30 mW, 0.81 J/point, beam area of 0.2 cm(2), 27 s, ≈ 29 points) in the tibialis anterior muscle occurred after the delimitation of the points on every 4 cm(2) was held. It was observed that (a) a significant torque increase (p < 0.05) post-LLLT compared to the values after placebo therapy at the beginning of resistance exercise, (b) both muscle torque (isokinetic) and median frequency (EMG) showed a faster decay of the signals collected after placebo and laser treatment when compared to control values, (c) no significant change in torque in the strength test of five repetitions, (d) a significant muscle activity decrease (p < 0.05) after laser therapy compared to control values, and (e) an increase in lactate levels post-LLLT (p < 0.05) after 30 min of exercise. It is concluded that the LLLT increased the muscle torque at the beginning of the exercise and maintained the levels of lactate after resistance exercise. Therefore, the LLLT with the parameters used in this study can be utilized in rehabilitation to improve muscle performance in elite athletes.

Layer-specific modulation of neuronal excitability by 660-nm laser irradiation in mouse neocortex

It has been reported that laser light irradiation (LLI) could regulate neuronal activities in the forebrain, but little is known if and how LLI in the red wavelength range affects neuronal excitability. Here, we investigated the effects of a continuous diode laser at 660 nm on intrinsic membrane properties and excitability of presumed pyramidal neurons in the thalamocortical input layer (layer 3/4) and in layer 5 of mouse primary auditory cortex using the whole-cell patch-clamp recording technique. In layer 3/4 neurons, 660-nm laser irradiation (LLI-660) at 20 mW for 5 min gradually increased resting membrane potentials, which reached a plateau after irradiation. Concomitantly, LLI-660 decreased onset latency of first action potentials (spikes) without changing spike threshold or peak amplitude, but increased inter-spike interval of initial bursting spike doublets and their peak amplitude ratio. None of these changes was observed in layer 5 neurons. Instead, LLI-660 at 20 mW rapidly reduced spike width ~5 % within 1 min of irradiation onset. The magnitude of this reduction did not change during 5 or 10 min irradiation, and returned quickly to at least baseline levels after turning the LLI off. Decreasing laser power to 10 mW reduced spike width to a lesser extent, suggesting laser power dependence of this phenomenon. These data suggest that LLI-660 regulates different aspects of neuronal excitability in cortical neurons in a layer-dependent manner possibly by affecting different voltage-gated ion channels.

The effect of low-level laser irradiation on muscle tension and hardness compared among three wavelengths

BACKGROUND AND AIMS

It has been reported that low-level laser irradiation (LLLI) can influence muscle tissue by retarding attenuation of muscle tension. Since the efficacy of LLLI on the effects of muscle contraction remains unclear, we examined in an in vivo animal model whether LLLI affects both muscle tension and muscle hardness in a wavelength-dependent manner, using the rat gastrocnemius muscle.

MATERIAL AND METHODS

Forty Sprague-Dawley adult rats were used. Under pentobarbital sodium anesthesia, their gastrocnemius muscle and tibial nerve were exteriorized. Diode LLLI systems delivering 3 wavelengths (405, 532, and 808 nm; 100 mW output) were used. Ten sets of tetanus (tetanic contractions) were delivered to the tibial nerve followed by a brief rest or LLLI for 15 s and an additional 7 sets of tetanus with an inter-stimulus interval of 5 min. The muscle tension and muscle hardness were measured with a tension transducer and hardness meter, respectively.

RESULTS

405 nm LLLI did not influence either muscle tension or hardness. 532 nm LLLI significantly improved the maintenance of muscle tension compared with the 808 nm group (P<0.05). In contrast, 808 nm LLLI significantly improved the recovery from muscle hardness compared with the other groups (P<0.05).

CONCLUSION

We conclude that LLLI has wavelength-dependent effects on the gastrocnemius muscle and LLLI at appropriate wavelengths and dosimetry offers potential in the treatment to relieve muscle tension or stiffness.

The effect of low-level laser irradiation on muscle tension and hardness compared among three wavelengths

BACKGROUND AND AIMS

It has been reported that low-level laser irradiation (LLLI) can influence muscle tissue by retarding attenuation of muscle tension. Since the efficacy of LLLI on the effects of muscle contraction remains unclear, we examined in an in vivo animal model whether LLLI affects both muscle tension and muscle hardness in a wavelength-dependent manner, using the rat gastrocnemius muscle.

MATERIAL AND METHODS

Forty Sprague-Dawley adult rats were used. Under pentobarbital sodium anesthesia, their gastrocnemius muscle and tibial nerve were exteriorized. Diode LLLI systems delivering 3 wavelengths (405, 532, and 808 nm; 100 mW output) were used. Ten sets of tetanus (tetanic contractions) were delivered to the tibial nerve followed by a brief rest or LLLI for 15 s and an additional 7 sets of tetanus with an inter-stimulus interval of 5 min. The muscle tension and muscle hardness were measured with a tension transducer and hardness meter, respectively.

RESULTS

405 nm LLLI did not influence either muscle tension or hardness. 532 nm LLLI significantly improved the maintenance of muscle tension compared with the 808 nm group (P<0.05). In contrast, 808 nm LLLI significantly improved the recovery from muscle hardness compared with the other groups (P<0.05).

CONCLUSION

We conclude that LLLI has wavelength-dependent effects on the gastrocnemius muscle and LLLI at appropriate wavelengths and dosimetry offers potential in the treatment to relieve muscle tension or stiffness.

Irradiation of 850-nm laser light changes the neural activities in rat primary visual cortex

Although infrared laser was proven to be an alternative approach for neural stimulation, there is very little known about the neural response to infrared laser irradiation in visual cortex. This study is to investigate the effect of near-infrared laser irradiation on neural activities at the cortex level. A 850-nm pigtailed diode laser was applied to stimulate the rat primary visual cortex while the horizontal black and white stripe pattern was used as standard visual stimulation to evoke visual-evoked potential (VEP). Both amplitude and latency of VEP P100 was measured with or without infrared pulse stimulation applied in rat primary visual cortex. Paired t test and one-way analysis of variance were used to evaluate the impact of infrared irradiation and its pulse width on the amplitudes and latencies of P100, respectively. The results from our preliminary study revealed that, the pulsed near-infrared laser depressed the VEP amplitude and shortened the latency of P100; with the increment of pulse width of infrared irradiation, further decline of VEP amplitude and much shortened latency of P100 were observed. The present work suggests that near-infrared laser irradiation can alter the neural activities in primary visual cortex transiently, and could provide a novel contactless artificial neural stimulus to brain cortex with high spatial selectivity.

Effect of low-power gallium-aluminum-arsenium noncoherent light (640 nm) on muscle activity: a clinical study

BACKGROUND DATA

Studies have shown the significant effects of electromagnetic irradiation in the visible region, with laser as an irradiation source. However, the effect of LEDs (light-emitting diodes) irradiation in similar wavelengths is not known.

OBJECTIVE

The purpose of this clinical study was to verify the effects of the LED (640 nm with 40 nm full bandwidth at half maximum) on muscle activity.

METHODS

The study was done with 30 test subjects, of both genders, aged 23 ± 3 years, with a mean weight of 60 kg, divided into three groups (n = 10). Fatigue was induced through the maximum power of a bite, for 60 s in two overlaid occlusal platforms, coupled to a load cell and to a biologic signal-acquisition device. LED irradiation of the right masseter muscle was applied to all subjects. The left muscle received placebo treatment. Irradiation was applied in eight points on the right masseter muscle (transcutaneous), 1.044 J per point, 2.088 J per point, or 3.132 J per point, 0.116 W, 0.522 cm(2) spot size, 0.816 cm spot Ø, continuous wave, perpendicular to the skin.

RESULTS

An increase in muscle activity was observed after irradiation with 1.044 J per point (p < 0.05). A significant increase (p < 0.01) in the time before fatigue was observed in the irradiated muscle with 2.088 J per point, without a change in the force of contraction (p > 0.05). This change was not observed with 1.044 J per point and 3.132 J per point. The results suggest a dose-dependent relation with this kind of noncoherent irradiation in the red region of the electromagnetic spectrum in the muscle-fatigue process.

CONCLUSION

It was concluded that LED can be used as a clinical tool to increase muscle activity (1.044 J per point) and to prevent fatigue (2.088 J per point), without change in the muscle force.

Efficacy of low-level laser therapy in the management of neck pain: a systematic review and meta-analysis of randomised placebo or active-treatment controlled trials

BACKGROUND

Neck pain is a common and costly condition for which pharmacological management has limited evidence of efficacy and side-effects. Low-level laser therapy (LLLT) is a relatively uncommon, non-invasive treatment for neck pain, in which non-thermal laser irradiation is applied to sites of pain. We did a systematic review and meta-analysis of randomised controlled trials to assess the efficacy of LLLT in neck pain.

METHODS

We searched computerised databases comparing efficacy of LLLT using any wavelength with placebo or with active control in acute or chronic neck pain. Effect size for the primary outcome, pain intensity, was defined as a pooled estimate of mean difference in change in mm on 100 mm visual analogue scale.

FINDINGS

We identified 16 randomised controlled trials including a total of 820 patients. In acute neck pain, results of two trials showed a relative risk (RR) of 1.69 (95% CI 1.22-2.33) for pain improvement of LLLT versus placebo. Five trials of chronic neck pain reporting categorical data showed an RR for pain improvement of 4.05 (2.74-5.98) of LLLT. Patients in 11 trials reporting changes in visual analogue scale had pain intensity reduced by 19.86 mm (10.04-29.68). Seven trials provided follow-up data for 1-22 weeks after completion of treatment, with short-term pain relief persisting in the medium term with a reduction of 22.07 mm (17.42-26.72). Side-effects from LLLT were mild and not different from those of placebo.

INTERPRETATION

We show that LLLT reduces pain immediately after treatment in acute neck pain and up to 22 weeks after completion of treatment in patients with chronic neck pain.

FUNDING

None.

Short-term effects of high-intensity laser therapy versus ultrasound therapy in the treatment of people with subacromial impingement syndrome: a randomized clinical trial

BACKGROUND

Subacromial impingement syndrome (SAIS) is a painful condition resulting from the entrapment of anatomical structures between the anteroinferior corner of the acromion and the greater tuberosity of the humerus.

OBJECTIVE

The aim of this study was to evaluate the short-term effectiveness of high-intensity laser therapy (HILT) versus ultrasound (US) therapy in the treatment of SAIS.

DESIGN

The study was designed as a randomized clinical trial.

SETTING

The study was conducted in a university hospital.

PATIENTS

Seventy patients with SAIS were randomly assigned to a HILT group or a US therapy group.

INTERVENTION

Study participants received 10 treatment sessions of HILT or US therapy over a period of 2 consecutive weeks.

MEASUREMENTS

Outcome measures were the Constant-Murley Scale (CMS), a visual analog scale (VAS), and the Simple Shoulder Test (SST).

RESULTS

For the 70 study participants (42 women and 28 men; mean [SD] age=54.1 years [9.0]; mean [SD] VAS score at baseline=6.4 [1.7]), there were no between-group differences at baseline in VAS, CMS, and SST scores. At the end of the 2-week intervention, participants in the HILT group showed a significantly greater decrease in pain than participants in the US therapy group. Statistically significant differences in change in pain, articular movement, functionality, and muscle strength (force-generating capacity) (VAS, CMS, and SST scores) were observed after 10 treatment sessions from the baseline for participants in the HILT group compared with participants in the US therapy group. In particular, only the difference in change of VAS score between groups (1.65 points) surpassed the accepted minimal clinically important difference for this tool.

LIMITATIONS

This study was limited by sample size, lack of a control or placebo group, and follow-up period.

CONCLUSIONS

Participants diagnosed with SAIS showed greater reduction in pain and improvement in articular movement functionality and muscle strength of the affected shoulder after 10 treatment sessions of HILT than did participants receiving US therapy over a period of 2 consecutive weeks.

Effects of low-power laser irradiation on the threshold of electrically induced paroxysmal discharge in rabbit hippocampus CA1

In acute experiments using adult rabbits, we measured the paroxysmal discharge threshold (PADT) elicited by stimulation to the apical dendritic layer of the hippocampal CA1 region before and after low-power laser irradiation. Nd:YVO(4) laser irradiation (wavelength: 532 nm) was introduced into the same region as the stimulation site. The average PADT was 247 +/- 13 microA (n = 18) before laser irradiation, while after 5-min laser irradiation with 50, 75, and 100 mW, PADT was 333 +/- 40 (n = 4), 353 +/- 33 (n = 4) and 367 +/- 27 microA (n = 6), respectively. The latter two increments were statistically significant compared to the control (p < 0.05 and p < 0.01). After 10-min laser irradiation with 75 and 100 mW, PADT was 340 +/- 47 (n = 9) and 480 +/- 60 microA (n = 11; p < 0.01), respectively. Laser irradiation with a specific wavelength and average power offers the potential to suppress the generation of paroxysmal discharges in rabbit hippocampus CA1. Correlation analyses suggest that PADT increments are based on photochemical as well as photothermal effects of laser irradiation.

830 nm laser irradiation induces varicosity formation, reduces mitochondrial membrane potential and blocks fast axonal flow in small and medium diameter rat dorsal root ganglion neurons: implications for the analgesic effects of 830 nm laser

We report the formation of 830 nm (cw) laser-induced, reversible axonal varicosities, using immunostaining with beta-tubulin, in small and medium diameter, TRPV-1 positive, cultured rat DRG neurons. Laser also induced a progressive and statistically significant decrease (p<0.005) in MMP in mitochondria in and between static axonal varicosities. In cell bodies of the neuron, the decrease in MMP was also statistically significant (p<0.05), but the decrease occurred more slowly. Importantly we also report for the first time that 830 nm (cw) laser blocked fast axonal flow, imaged in real time using confocal laser microscopy and JC-1 as mitotracker. Control neurons in parallel cultures remained unaffected with no varicosity formation and no change in MMP. Mitochondrial movement was continuous and measured along the axons at a rate of 0.8 microm/s (range 0.5-2 microm/s), consistent with fast axonal flow. Photoacceptors in the mitochondrial membrane absorb laser and mediate the transduction of laser energy into electrochemical changes, initiating a secondary cascade of intracellular events. In neurons, this results in a decrease in MMP with a concurrent decrease in available ATP required for nerve function, including maintenance of microtubules and molecular motors, dyneins and kinesins, responsible for fast axonal flow. Laser-induced neural blockade is a consequence of such changes and provide a mechanism for a neural basis of laser-induced pain relief. The repeated application of laser in a clinical setting modulates nociception and reduces pain. The application of laser therapy for chronic pain may provide a non-drug alternative for the management of chronic pain.

Low-level laser therapy can reduce lipopolysaccharide-induced contractile force dysfunction and TNF-alpha levels in rat diaphragm muscle

Our objective was to investigate if low-level laser therapy (LLLT) could improve respiratory function and inhibit tumor necrosis factor (TNF-alpha) release into the diaphragm muscle of rats after an intravenous injection of lipopolysaccharide (LPS) (5 mg/kg). We randomly divided Wistar rats in a control group without LPS injection, and LPS groups receiving either (a) no therapy, (b) four sessions in 24 h with diode Ga-AsI-Al laser of 650 nm and a total dose of 5.2 J/cm2, or (c) an intravenous injection (1.25 mg/kg) of the TNF-alpha inhibitor chlorpromazine (CPZ). LPS injection reduced maximal force by electrical stimulation of diaphragm muscle from 24.15+/-0.87 N in controls, but the addition of LLLT partly inhibited this reduction (LPS only: 15.01+/-1.1 N vs LPS+LLLT: 18.84+/-0.73 N, P<0.05). In addition, this dose of LLLT and CPZ significantly (P<0.05 and P<0.01, respectively) reduced TNF-alpha concentrations in diaphragm muscle when compared to the untreated control group.

Effects of argon laser irradiation on polar excitations in frog sciatic nerve

BACKGROUND AND OBJECTIVES

Since the mechanisms underlying the effects of low-power laser irradiation on the nervous system remain unclear, we examined whether such irradiation can influence ionic channels of the nerve membrane using the law of polar excitation in isolated frog sciatic nerve.

STUDY DESIGN/MATERIALS AND METHODS

Using 43 frogs (Xenopus laevis), nerve preparations were stimulated at 0.5/second using a 10-millisecond pulse at supramaximal intensity. Ar+ laser irradiation (457, 488, 514 nm; 50, 75, 100 mW) was applied for 30 minutes to the portion between the anode and cathode stimulating electrodes.

RESULTS AND CONCLUSIONS

Ar+ laser irradiations (457, 488 nm; 50 mW) blocked the generation of anode-break-excitation, rather than cathode-make-excitation. Such a selective effect occurred when applying a blocker of hyperpolarization-activated cation current (Ih) channel, ZD7288. Ar+ laser irradiation may influence Na+ channels in addition to Ih channels.