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Background: Photobiomodulation (PBM) and transcutaneous electrical nerve stimulation (TENS) are used to reduce neck pain., Objective: To investigate the immediate and 1-month post-treatment effects of 10 treatment sessions of PBM and TENS delivered over 2 weeks on pain intensity in individuals with neck pain., Methods: Individuals with neck pain were randomized into four groups: PBM+TENS, PBM, TENS, and Sham., Primary Outcome: pain intensity at rest., Secondary Outcomes: pain intensity during movement, pressure pain threshold (PPT), temporal summation (TS), conditioned pain modulation (CPM), cervical range of motion (ROM), psychosocial factors, drug intake for neck pain, and global perceived effect (GPE). All outcome assessments were made pre- and post-treatment. Mean differences and 95 % confidence intervals were calculated for between-group comparisons., Results: A total of 144 participants were recruited. No significant between-group difference was observed for pain intensity at rest, TS, CPM, ROM, psychosocial factors, and drug intake. The PBM+TENS showed a reduction in pain intensity during movement and GPE compared to the PBM (MD: 1.0 points; 95 % CI: 0.0, 2.0; MD: 2.0 points; 95 % CI: 1.0, 3.0) and Sham (MD: 2.0 points; 95 % CI: 1.0, 3.0; MD: 2.0 points; 95 % CI: 1.0, 3.0) groups. PBM+TENS presented a medium effect size to increase local PPT compared to PBM and Sham groups. TENS presented a medium effect size to increase local PPT compared to PBM and Sham groups. TENS presented a medium effect size to increase distant PPT compared to other groups., Conclusions: The use of PBM or TENS was not effective for reducing pain intensity at rest. The combination of PBM and TENS was effective in improving pain intensity during movement, local hyperalgesia, and the GPE. TENS reduced local and distant hyperalgesia., Competing Interests: Declaration of competing interest We hereby certify that no party with a direct interest in the results of the research that supports this article has or will confer benefits on us or any organization with which we are affiliated., (Copyright © 2024. Publicado por Elsevier España, S.L.U.)

Purpose: Characterize heart rate and cardiac autonomic response to painful stimulus on neck pain., Methods: Twenty-five individuals with neck pain and 25 healthy subjects were included. Heart rate variability and heart rate were assessed in the conditioned pain modulation test at pretest rest, during testing and in recovery. Heart rate variability indices were obtained using linear and nonlinear methods., Results: No significant differences were observed between groups regarding heart rate and the linear methods (p > 0.05). However, significant difference was observed between groups regarding nonlinear methods (standard deviation of the instantaneous variability of beat-to-beat interval variability, p = 0.005) CONCLUSIONS: Individuals with chronic neck pain showed autonomic responses similar to those of their healthy counterparts during the conditioning stimulus., Competing Interests: Declaration of competing interest We hereby certify that no party with a direct interest in the results of the research that supports this article has or will offer benefits to us or any organization with which we are affiliated., (Copyright © 2024. Published by Elsevier Ltd.)

Purpose: The aim of this review was to compare the heart rate variability (HRV) responses at rest of adults with chronic musculoskeletal pain against healthy controls., Methods: The PubMed, Scopus, Web of Science (Science and Social Science Citation Index), and CINAHL databases were searched, with no date restrictions. Two independent reviewers selected observational studies that characterized the HRV responses at rest in adults with chronic musculoskeletal pain compared with those of healthy controls. Methodological quality was assessed using the Downs and Black checklist., Results: This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. HRV in adults with chronic musculoskeletal pain was evaluated systematically. Of the 4893 studies screened, 20 of poor-to-moderate quality met the inclusion criteria. Most studies used electrocardiography and at least one time and/or frequency domain index. Studies were found that investigated HRV in adults with temporomandibular disorders, neck pain, whiplash, low back pain, and fibromyalgia. The heterogeneity of the studies in relation to painful conditions, parameters or position for HRV analysis precluded a meta-analysis. In general, these studies seem to show increased sympathetic and decreased parasympathetic modulation in adults with musculoskeletal pain when compared to controls., Conclusions: Adults with musculoskeletal pain exhibited a decline in HRV compared to controls. However, definitive conclusions cannot be drawn since the evidence is heterogeneous and of moderate quality. Further high-quality research with standardized measurements is needed., (© 2023 World Institute of Pain.)

Background: There is no systematic review assessing the effectiveness of interferential current (IC) in patients with low back pain., Objective: To investigate the effectiveness of IC in patients with chronic non-specific low back pain., Methods: The databases PUBMED, EMBASE, PEDro, Cochrane Library, CINAHL, and SCIELO were searched. Randomized controlled trials reporting pain intensity and disability in patients with chronic non-specific low back pain, in which IC was applied were included. Methodological quality was assessed using the PEDro scale. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) was used to evaluate the quality of evidence., Results: Thirteen RCTs were considered eligible for this systematic review (pooled n = 1367). Main results showed moderate-quality evidence and moderate effect sizes that IC probably reduces pain intensity and disability compared to placebo immediately post-treatment (Pain: MD = -1.57 points; 95% CI -2.17, -0.98; Disability: MD = -1.51 points; 95% CI -2.57, -0.46), but not at intermediate-term follow-up. Low-quality evidence with small effect size showed that IC may reduce pain intensity (SMD = -0.32; 95% CI -0.61, -0.03, p = 0.03) compared to TENS immediately post-treatment, but not for disability. There is very low-quality evidence that IC combined with other interventions (massage or exercises) may not further reduce pain intensity and disability compared to the other interventions provided in isolation immediately post-treatment., Conclusion: Moderate-quality evidence shows that IC is probably better than placebo for reducing pain intensity and disability immediately post-treatment in patients with chronic non-specific low back pain., Competing Interests: Conflicts of interest Richard Eloin Liebano is co-author of studies included in the present review. All other authors have no conflict of interests to declare., (Copyright © 2023 Associação Brasileira de Pesquisa e Pós-Graduação em Fisioterapia. Publicado por Elsevier España, S.L.U. All rights reserved.)

Background: Pain is considered the main limiting factor in carboxytherapy. Electroanalgesia has gained recognition in the field of dermatology and to date, only transcutaneous electrical nerve stimulation (TENS) has proved to be effective at reducing pain associated with carboxytherapy; however, the effect of medium frequency currents has yet to be investigated., Aims: Compare the effects of TENS, interferential current (IFC), and Aussie current on pain intensity associated with carboxytherapy and sensory comfort in the treatment of cellulite., Patients/methods: Seventy-five women aged 18-49 years with moderate and/or severe gluteal cellulite were randomized into three groups: TENS (n = 25), IFC (n = 25), and Aussie current (n = 25), which underwent three sessions of carboxytherapy associated with an electrical current. Current amplitude was adjusted after each puncture, according to the maximum tolerance reported by participants, below the motor threshold. Pain intensity was measured using a numeric rating scale (0-10) and sensory comfort with the visual analogue scale (0-10)., Results: There was no significant intergroup difference in pain intensity (p > 0.05) and sensory comfort (p = 0.502) during the application of carboxytherapy throughout the three treatment sessions., Conclusion: TENS, IFC, and Aussie currents showed no difference in pain intensity reduction and no current was found to be more comfortable., (© 2023 The Authors. Journal of Cosmetic Dermatology published by Wiley Periodicals LLC.)

Background: Nonspecific neck pain is a multifactorial and very common condition in adult individuals, traditional acupuncture (TA) and laser acupuncture (LA) may be treatment options for certain individuals in such a condition. However, no reports were found in the literature comparing the effectiveness of TA and LA in cases of chronic nonspecific neck pain. Therefore, the aim of the present study is to investigate the effectiveness of TA and LA therapies in individuals with chronic nonspecific neck pain, noting which one is more efficient for this condition. The result of this research will have direct implications for pain management and, consequently, may benefit individuals suffering from nonspecific chronic neck pain., Methods/design: This will be a controlled and randomized clinical trial. Eighty-four individuals will be recruited and distributed equally and randomly into 3 groups: TA (which will receive the acupuncture treatment with needles), LA (which will receive the laser acupuncture treatment), and Sham (who will receive the placebo intervention). The acupuncture points (Tianzhu, Fengchi, Jianjing, and Jianzhongshu) will be stimulated bilaterally. The primary outcome will be pain intensity, determined using the Numerical Rating Scale. The secondary outcomes will be pressure pain threshold, temporal summation of pain, conditioned pain modulation, use of analgesic medicines after treatment, and the global perceived effect scale. The assessments will be performed immediately before and after the treatment, which will be a single session, at the follow-up and 1 month after the end of the treatments; evaluation will be made of the pain intensity and the global perceived effect. Statistical analysis of the data obtained will consider a significance level of p < 0.05., Discussion: This study will provide evidence concerning the effects of LA treatment, in comparison with TA and sham intervention, leading to benefits for individuals suffering from chronic nonspecific neck pain., Trial Registration: Brazilian Registry of Clinical Trials - ReBEC RBR-7vbw5gd . Date of registration: August 06th, 2021., (© 2022. The Author(s).)

Background: To date, there has been no investigation addressing the effects of vibration anesthesia during carboxytherapy. Aim: Investigate the analgesic effect of different vibratory devices during carboxytherapy for the treatment of cellulite. Materials & methods: A total of 78 women between 18 and 49 years of age with cellulite in the gluteal region will be randomly allocated to three groups: Group A (carboxytherapy and vibratory device A), Group B (carboxytherapy and vibratory device B) and control group. Pain intensity will be assessed using a numerical rating scale after each puncture. Expected outcome: Vibration anesthesia is expected to be effective at diminishing the pain intensity caused by carboxytherapy comparison with the control group, with no differences between the vibratory devices. Trial registry: Brazilian Registry of Clinical Trials: ReBEC (RBR-8jcqy7c).

Background and Objectives : Transcutaneous electrical stimulation of low- and medium-frequency currents is commonly used in pain management. Interferential current (IFC) therapy, a medium frequency alternating current therapy that reportedly reduces skin impedance, can reach deeper tissues. IFC therapy can provide several different treatment possibilities by adjusting its parameters (carrier frequency, amplitudemodulated frequency, sweep frequency, sweep mode or swing pattern, type of application (bipolar or quadripolar), time of application and intensity). The objective of this review article is to discuss the literature findings on the analgesic efficacy of IFC therapy. Conclusions : According to the literature, IFC therapy shows significant analgesic effects in patients with neck pain, low back pain, knee osteoarthritis and post-operative knee pain. Most of the IFC parameters seem not to influence its analgesic effects. We encourage further studies to investigate the mechanism of action of IFC therapy.

Background and Objective: The objective of this systematic review was to investigate the effectiveness of electrical stimulation (ES) for neck pain (NP)., Databases and Data Treatment: The databases CINAHL, Embase, MEDLINE (via OVID), PEDro and Web of Science were searched, with no date restrictions. Two independent reviewers selected randomized controlled trials (RCTs) reporting pain, range of motion or psychosocial factors in people with NP, in which ES was applied. Methodological quality was assessed using the PEDro scale. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) was used to evaluate the quality of evidence. Thirty studies met eligibility criteria., Results: Main results showed evidence of moderate quality that ES combined with other intervention significantly decreases the pain intensity compared to other intervention immediately post-treatment and at short-term follow-up; evidence of low quality showed significant effects of ES combined with other intervention in decreasing neck disability compared to other intervention immediately post-treatment; evidence of very-low quality that ES increased the pressure pain threshold compared to placebo immediately post-treatment and that ES + other intervention also increased the pressure pain threshold compared to other intervention at short-term follow-up., Conclusions: ES combined with other intervention seems to be useful to relieve pain and to improve disability in people with NP, however, more studies are needed., Significance: Electrical stimulation seems to be effective for improving pain intensity, immediately post-treatment in people with neck pain, mainly as an adjunct therapeutic modality. Nevertheless, high-quality RCTs are still needed to investigate the efficacy of electrical stimulation in neck pain., (© 2021 European Pain Federation - EFIC®.)

Background: Joint manipulation is generally used to reduce musculoskeletal pain; however, evidence has emerged challenging the effects associated with the specificity of the manipulated vertebral segment. The aim of this study was to verify immediate hypoalgesic effects between specific and non-specific cervical manipulations in healthy subjects., Method: Twenty-one healthy subjects (18-30 years old; 11 males, 10 females) were selected to receive specific cervical manipulation at the C6-7 segment (SCM) and non-specific cervical manipulation (NSCM) in aleatory order. A 48h interval between manipulations was considered. Pressure pain threshold (PPT) was measured pre- and post-manipulation with a digital algometer on the dominant forearm., Results: The SCM produced a significant increase in the PPT (P < 0.001) however no difference was observed in the PPT after the NCSM (P = 0.476). The difference between the two manipulation techniques was 37.26 kPa (95% CI: 14.69 to 59.83, p = 0.002) in favor of the SCM group CONCLUSION: Specific cervical manipulation at the C6-7 segment appears to increase PPT on the forearm compared to non-specific cervical manipulation in healthy subjects., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Objectives: To evaluate the effects of interferential current and photobiomodulation in patients with knee osteoarthritis., Design: A randomized, placebo-controlled, double-blind clinical trial., Setting: Physiotherapy Clinic of City University of São Paulo., Subjects: A total of 184 patients with knee osteoarthritis were recruited and, of these, 168 were included and randomized into four groups with 42 each: interferential current, photobiomodulation, interferential current plus photobiomodulation or placebo groups. One hundred and sixty-four patients completed the study., Intervention: Patients received 12 sessions (three times a week) of treatment: 30 minutes of interferential current (active or placebo) followed by photobiomodulation (active or placebo)., Main Measures: Primary outcome: pain intensity at rest and during movement (numeric rating scale) after 12 sessions. Secondary outcomes: functional capacity (Timed Up & Go and Sit and Lift tests and Lequesne and WOMAC questionnaires), pressure pain threshold, conditioned pain modulation, and muscle strength production (isokinetic evaluation). Patients were assessed at baseline, after 12 sessions, and three and six months after the end of the treatment., Results: Interferential current plus photobiomodulation reduced pain intensity at rest and during movement compared to placebo and interferential current at all time points ( P  < 0.05). Photobiomodulation reduced pain intensity at rest compared to placebo at all time points ( P  < 0.05) and compared to interferential current at six months follow-up ( P  < 0.05). Photobiomodulation reduced pain intensity during movement compared to placebo at six months follow-up ( P  < 0.05)., Conclusion: Interferential current plus photobiomodulation or isolated photobiomodulation improve pain intensity in knee osteoarthritis.

Objective: Given the complex and unclear etiology of neck pain, it is important to understand the differences in central sensitization as well as psychosocial factors in individuals with chronic neck pain and healthy controls. The purpose of this study was to benchmark differences in central sensitization, psychosocial factors, and range of motion between people with nonspecific chronic neck pain and healthy controls and to analyze the correlation between pain intensity, neck disability, and psychosocial factors in people with chronic neck pain., Methods: Thirty individuals with chronic neck pain and 30 healthy controls were included in this case-control study. Outcome measures were as follows: central sensitization (pressure pain threshold, temporal summation, and conditioned pain modulation), psychosocial factors (depressive symptoms, pain catastrophizing, and quality of life), and active cervical range of motion., Results: People with neck pain had lower local pressure pain threshold, a decrease in conditioned pain modulation, more depressive symptoms, greater pain catastrophizing, lower quality of life, and reduced range of motion for neck rotation when compared with healthy controls. In people with neck pain, moderate correlations were observed between pain intensity and quality of life (ρ = -0.479), disability and pain catastrophizing (ρ = 0.379), and disability and quality of life (ρ = -0.456)., Conclusions: People with neck pain have local hyperalgesia, impaired conditioning pain modulation, depressive symptoms, pain catastrophizing, low quality of life, and reduced active range of motion during neck rotation, which should be taken into account during assessment and treatment., Impact: This study shows that important outcomes, such as central sensitization and psychosocial factors, should be considered during assessment and treatment of individuals with nonspecific chronic neck pain. In addition, pain intensity and neck disability are correlated with psychosocial factors., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Physical Therapy Association. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Objective: The objective of this study was to compare the hypoalgesic effects of isolated or combined use of transcutaneous electrical nerve stimulation (TENS) and cervical joint manipulation (JM) in asymptomatic participants., Methods: One hundred and forty-four healthy participants aged 18 to 30 years old were randomly assigned to 1 of 4 groups (n = 36 per group): active TENS + active JM, active TENS + placebo JM, placebo TENS + active JM, and placebo TENS + placebo JM. Active or placebo TENS was applied to the dominant forearm. JM was applied to the C6-7 segments. The pressure pain threshold was measured pre- and postintervention and after 20 minutes on the forearm and tibialis anterior of the dominant side., Results: Segmental hypoalgesia was greater in the group active TENS + active JM compared with active TENS + placebo JM (P = .002), placebo TENS + active JM (P < .0001), and placebo TENS + placebo JM (P < .0001). For the extrasegmental hypoalgesia, active TENS + active JM had greater hypoalgesic effect compared with active TENS + placebo JM (P = .033), placebo TENS + active JM (P = .002), and placebo TENS + placebo JM (P < .0001)., Conclusion: TENS and JM produced hypoalgesia when used alone and, when the treatments were combined, a higher segmental and extrasegmental hypoalgesic effect was obtained in asymptomatic participants., (Copyright © 2021. Published by Elsevier Inc.)

Introduction: Chronic neck pain is a common musculoskeletal disorder that is associated with functional disability and decreased of quality of life. Electrophysical agents are commonly used to relieve pain, however the effects of combined use of these agents are little studied. The objective is to investigate the efficacy of photobiomodulation and electrical stimulation to relieve pain, both in isolation and combined., Materials and Methods: This a 4-arm randomized placebo-controlled trial with patient and evaluator blinded. This study will be performed in Department of Physical Therapy at Federal University of São Carlos, São Carlos/SP, Brazil. One hundred and forty-four patients with chronic neck pain will be randomized into 4 groups: active photobiomodulation therapy with active electrical stimulation, active photobiomodulation therapy, active electrical stimulation, or placebo treatment. They will receive 10 sessions of treatment., Primary Outcome: pain intensity (measured by pain numerical rating scale) posttreatment., Secondary Outcomes: pain during movement, neck disability, range of motion, pressure pain threshold, temporal summation, conditioned pain modulation, depressive symptoms, pain catastrophizing, quality of life, analgesic intake, and global perceived effect at posttreatment (10 sessions). Pain intensity and global perceived effect will also be measured after 6 weeks randomization., Discussion: The findings of this study might clarify the importance of using the photobiomodulation therapy and transcutaneous electrical nerve stimulation for patients with chronic neck pain., Trial Registration: NCT04020861. https://clinicaltrials.gov/ct2/show/NCT04020861?term=NCT04020861&draw=2&rank=1.

Objectives: To evaluate the effects of thermotherapy and transcutaneous electrical nerve stimulation (TENS) on pain intensity, pressure pain threshold (PPT) and conditioned pain modulation (CPM) in patients with primary dysmenorrhea (PD)., Design: A randomized, placebo-controlled, double-blind clinical trial., Setting: Physiotherapy Department of the Universidade Cidade de São Paulo, São Paulo (Brazil)., Interventions: Eighty-eight dysmenorrheic women were randomly allocated into four groups: Thermotherapy + TENS(n = 22), Thermotherapy(n = 22), TENS(n = 22) and Placebo(n = 22). Thermotherapy was applied by microwave diathermy (20 min), and TENS (200 μs, 100 Hz, 30 min), into the lower abdomen both., Main Outcome Measures: Pain intensity was measured using the numeric rating scale (NRS) and the McGill Pain Questionnaire (Br-MPQ). PPT and CPM were recorded from women's abdominal and lumbar. The evaluation was done in 5 times: baseline, after 20, 50, 110 min and 24 h from intervention., Results: There was a significant decrease in the NRS for Thermotherapy + TENS vs. TENS, for Thermotherapy vs. TENS and for Placebo, after 20 min; for Thermotherapy vs. TENS and for Placebo, after 110 min and 24 h. Abdome PPT increased in the Thermotherapy + TENS vs. TENS and Placebo, after 50 min; for Thermotherapy + TENS vs. Placebo and for Thermotherapy vs. Placebo, after 110 min. No changes in lumbar PPT and CPM were observed., Conclusions: The use of thermotherapy reduced NRS compared to the TENS and Placebo after 20, 110 min and 24 h. Thermotherapy demonstrated an increase in the PPT in the abdomen after 50 and 110 min and decreased the Br-MPQ scores after 110 min in patients with PD., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

We conducted a systematic review and meta-analysis analysing the existing data on transcutaneous electrical nerve stimulation (TENS) or interferential current (IFC) for chronic low back pain (CLBP) and/or neck pain (CNP) taking into account intensity and timing of stimulation, examining pain, function and disability. Seven electronic databases were searched for TENS or IFC treatment in non-specific CLBP or CNP. Four reviewers independently selected randomized controlled trials (RCTs) of TENS or IFC intervention in adult individuals with non-specific CLBP or CNP. Primary outcomes were for self-reported pain intensity and back-specific disability. Two reviewers performed quality assessment, and two reviewers extracted data using a standardized form. Nine RCTs were selected (eight CLBP; one CNP), and seven studies with complete data sets were included for meta-analysis (655 participants). For CLBP, meta-analysis shows TENS/IFC intervention, independent of time of assessment, was significantly different from placebo/control (p < 0.02). TENS/IFC intervention was better than placebo/control, during therapy (p = 0.02), but not immediately after therapy (p = 0.08), or 1-3 months after therapy (p = 0.99). Analysis for adequate stimulation parameters was not significantly different, and there was no effect on disability. This systematic review provides inconclusive evidence of TENS benefits in low back pain patients because the quality of the studies was low, and adequate parameters and timing of assessment were not uniformly used or reported. Without additional high-quality clinical trials using sufficient sample sizes and adequate parameters and outcome assessments, the outcomes of this review are likely to remain unchanged., Significance: These data highlight the need for additional high-quality RCTs to examine the effects of TENS in CLBP. Trials should consider intensity of stimulation, timing of outcome assessment and assessment of pain, disability and function., (© 2017 European Pain Federation - EFIC®.)

Objective: To verify the efficacy of high voltage pulsed current in collagen realignment and synthesis and in angiogenesis after the partial rupturing of the Achilles tendon in rats., Method: Forty male Wistar rats were randomized into four groups of 10 animals each: sham, cathodic stimulation, anodic stimulation, and alternating stimulation. Their Achilles tendons were submitted to direct trauma by a free-falling metal bar. Then, the treatment was administered for six consecutive days after the injury. In the simulation group, the electrodes were positioned on the animal, but the device remained off for 30 minutes. The other groups used a frequency of 120 pps, sensory threshold, and the corresponding polarity. On the seventh day, the tendons were removed and sent for histological slide preparation for birefringence and Picrosirius Red analysis and for blood vessel quantification., Results: No significant difference was observed among the groups regarding collagen realignment (types I or III collagen) or quantity of blood vessels., Conclusion: High voltage pulsed current for six consecutive days was not effective in collagen realignment, synthesis, or angiogenesis after the partial rupturing of the Achilles tendon in rats.

Background: Tendon injury is one of the most frequent injuries in sports activities. TENS is a physical agent used in the treatment of pain but its influence on the tendon's healing process is unclear., Objective: To evaluate the influence of TENS on the healing of partial rupture of the Achilles tendon in rats., Method: Sixty Wistar rats were submitted to a partial rupture of the Achilles tendon by direct trauma and randomized into six groups (TENS or Sham stimulation) and the time of evaluation (7, 14, and 21 days post-injury). Burst TENS was applied for 30 minutes, 6 days, 100 Hz frequency, 2 Hz burst frequency, 200 µs pulse duration, and 300 ms pulse train duration. Microscopic analyses were performed to quantify the blood vessels and mast cells, birefringence to quantify collagen fiber alignment, and immunohistochemistry to quantify types I and III collagen fibers., Results: A significant interaction was observed for collagen type I (p=0.020) where the TENS group presented lower percentage in 14 days after the lesion (p=0.33). The main group effect showed that the TENS group presented worse collagen fiber alignment (p=0.001) and lower percentage of collagen III (p=0.001) and the main time effect (p=0.001) showed decreased percentage of collagen III at 7 days (p=0.001) and 14 days (p=0.001) after lesion when compared to 21 days., Conclusions: Burst TENS inhibited collagen I and III production and impaired its alignment during healing of partial rupture of the Achilles tendon in rats.

Objective: The aim of this study was to quantify mast cells at different time intervals after partial Achilles tendon rupture in rats treated with low-level laser therapy (LLLT)., Background Data: There is a high incidence of lesions and ruptures in the Achilles tendon that can take weeks and even months to heal completely. As the mast cells help in the healing repair phase, and LLLT has favorable effects on this tissue repair process, study of this modality on the quantity of mastocytes in the ruptured tendon is relevant., Methods: Sixty Wistar rats were subjected to partial Achilles' tendon rupture by direct trauma, randomized into 10 groups, and then divided into the group treated with 80 mW aluminum gallium arsenide infrared laser diode, continuous wave, 2.8 W/cm(2) power density, 40 J/cm(2) energy density, and 1.12 J total energy, and the simulation group. Both the groups were subdivided according to the histological assessment period of the sample, either 6 h, 12 h, 24 h, 2 days, or 3 days after the rupture, to quantify the mastocytes in the Achilles' tendon., Results: The group subjected to LLLT presented a greater quantity of mastocytes in the periods of 6 h, 12 h, 24 h, 2 days, and 3 days after rupture, compared with the simulation groups, but differences were detected between the sample assessment periods only in the simulation group., Conclusions: LLLT was shown to increase the quantity of mastocytes in the assessment periods compared with the simulation groups.