Effect of transcutaneous electrical nerve stimulation on muscle metaboreflex in healthy young and older subjects

Modulating activity of PVN neurons prevents atrial fibrillation induced circulation dysfunction by electroacupuncture at BL15

BACKGROUND

Circulation dysfunction is a major contributing factor to thrombosis in patients with atrial fibrillation (AF) for which effective interventions are lacking. Growing evidence indicates that regulating the paraventricular nucleus (PVN), an autonomic control center, could offer a novel strategy for treating cardiovascular and circulatory diseases. Concurrently, electroacupuncture (EA) at Xinshu (BL15), a form of peripheral nerve stimulation, has shown efficacy in treating several cardiovascular conditions, although its specific mechanism remains unclear. This study aimed to assess the impact of EA at BL15 on circulatory dysfunction in a rat AF model and investigate the pivotal role of PVN neuronal activity.

METHODS

To mimic the onset of AF, male SD rats received tail intravenous injection of ACh-CaCl2 and were then subjected to EA at BL15, sham EA, or EA at Shenshu (BL23). Macro- and micro-circulation function were evaluated using in vivo ultrasound imaging and laser doppler testing, respectively. Vasomotricity was assessed by measuring dimension changes during vascular relaxation and contraction. Vascular endothelial function was measured using myograph, and the activation of the autonomic nerve system was evaluated through nerve activity signals. Additionally, chemogenetic manipulation was used to block PVN neuronal activation to further elucidate the role of PVN activation in the prevention of AF-induced blood circulation dysfunction through EA treatment.

RESULTS

Our data demonstrate that EA at BL15, but not BL23 or sham EA, effectively prevented AF-induced macro- and micro-circulation dysfunction. Furthermore, EA at BL15 restored AF-induced vasomotricity impairment. Additionally, EA treatment prevented abnormal activation of the autonomic nerve system induced by AF, although it did not address vascular endothelial dysfunction. Importantly, excessive activation of PVN neurons negated the protective effects of EA treatment on AF-induced circulation dysfunction in rats.

CONCLUSION

These results indicate that EA treatment at BL15 modulates PVN neuronal activity and provides protection against AF-induced circulatory dysfunction.

Eliciting blinks by transcutaneous electric nerve stimulation improves tear fluid in healthy video display terminal users: A self-controlled study

We aimed to elicit strong blinks among healthy video display terminal (VDT) users by periorbital transcutaneous electric nerve stimulation (TENS) and evaluate its impact on the tear fluid and visual task. Appropriate TENS conditions were evaluated to evoke strong blinks under minimum discomfort. Seventeen healthy VDT users with noninvasive Keratograph first breakup time (NIKf-BUT) 5-15 s and Ocular Surface Disease Index (OSDI) scores < 15 were recruited in this study. Before the trial, noninvasive Keratograph average breakup time (NIKa-BUT), tear meniscus height (TMH) and OSDI scores were evaluated. Before each TENS session, the volunteers played Tetris while the corresponding blink rate and Tetris scores were recorded. Then, the participants underwent 30 minutes of TENS, which evoked blinking of their right eye 20 times per minute. Tetris scores were evaluated again during TENS. The Tetris scores and corresponding blink rate were assessed after each TENS session while NIKa-BUT, TMH and OSDI scores were recorded after the third and sixth TENS sessions. We found that OSDI scores declined significantly after the sixth TENS (P = .003). The NIKa-BUT of the right eye was promoted after the sixth TENS (P = .02), and the TMH was higher after the third and sixth TENS in both eyes (P = .03, P = .03 for right eyes respectively, P = .01, P = .01 for left eyes respectively). There was no significant difference between the adjusted Tetris scores before and during TENS (P = .12). The blink rate before and after TENS were unaffected after 6 sessions (P = .61). The results indicated that periorbital TENS effectively ameliorated ocular irritation and improved tear secretion and tear film stability by eliciting strong blinks in healthy VDT users without disturbing the visual task.

Analgesic effects of high-frequency and low-frequency TENS currents in patients with distal neuropathy

Currently, diabetes mellitus (DM) is relevant problem, both for its prevalence and complications, including distal polyneuropathy (DPNP). At the same time, discussions continue on analgesic efficacy of transcutaneous electrical nerve stimulation (TENS) in DPNP. Aim of this study was to conduct a multi-faceted assessment of pain syndrome in these patients before and after TENS, taking into account levels of polyneuropathy, its severity and age of patients. The study was conducted in accordance with the research of the Federal State Budgetary Institution of the National Medical Research Center for Rehabilitation and Balneology of the Ministry of Health of the Russian Federation (CTR No. 121040100062-3) and with the permission of the Local Ethics Committee (IRB No. 2 dated 14.01.2021). The study included 75 patients with DM type II with DPNP, which are distributed into 3 groups of 25 people: Group 1a, patients received high–frequency TENS (HF); Group Ib, patients received low-frequency TENS (LF); as control, Group C received a standard method of pharmacological therapy without physiotherapy. Intensity of DPNP was evaluated before and after the course of treatment using a visual analog scale (VAS), the McGill Pain Questionnaire (MPQ), and a graphical linear analysis of pain on the neuropathic pain diagnostic questionnaire 4 (DN4) scale. TENS provides an analgesic effect that may exceed pharmacotherapy in terms of efficacy and safety. There was a 65.9% reduction in neuropathic pain according to VAS after a course of application, with the effects remaining up to 34% during the 6-month follow-up. HF TENS provided a higher significant analgesic effects than LF TENS, as it ensures the reduction of pain syndrome according to VAS by 25.8% (p <0.01), and total estimated characteristics - 35.5% (p <0.01), and touch - in at 58.1% (p = 0.001) and according to the scales of the MPQ (S) and DN4 - by 21% (p = 0.007). The observed differences in analgesic effects between HF TENS and LF TENS are based on analyses of pain in the immediate and long-term follow-up periods of type II DM patients with DPNP. These results, based on summation of the estimated parameters of the international pain scales support expectation of an expansion of the the use of analgesic TENS in aging patients suffering with DM of varying severity and extent of DPNP damage, a goal of great scientific and practical importance.

Sex difference in blood pressure response to orthostatic stress: effects of transcutaneous electrical nerve stimulation

OBJECTIVE

We investigated sex differences in blood pressure (BP) response to transcutaneous electrical nerve stimulation (TENS) during orthostatic stress (ORT).

METHODS

Seventeen healthy young adults (males = 9; females = 8) underwent TENS or SHAM stimulus applied in the cervicothoracic region for 30 min in the supine position followed by 10 min in the orthostatic position. Electrocardiogram and BP were continuously recorded at rest and during ORT. Stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) were calculated from the BP signal.

RESULTS

Orthostatic challenge decreased BP similarly for both sexes during ORT, a deeper drop in CO and a slight increase in heart rate were found in women compared with men (P = 0.03 and 0.05, respectively). TENS evoked a pronounced fall in SBP in men compared with the SHAM condition (P < 0.05). TENS has no effect on SBP in women compared with the SHAM condition.

CONCLUSION

This finding suggests a possible modulatory effect by one cervicothoracic TENS session on sympathetic tonus in healthy men.

High Versus Low Frequency Transcutaneous Electric Nerve Stimulation On Chronic Venous Lower Limb Ulceration Randomized Controlled Trial

The major objective of the current paper is to trace and investigate which method is more effective whether the high or the low Transcutaneous electric Nerve Stimulations (TENS) on venous ulcers. A single-blinded, randomized, and controlled trial was done successfully. Sixty venous ulcer patients were divided randomly into three groups; Group (A): control group, Group(B): High-TENS group, and Group(C): Low-TENS group. Group (A), contains twenty participants who received routine medical care and dressing. As for group (B), includes twenty participants who obtained high-frequency TENS; Frequency (80-120) HZ, Intensity (15 - 30 amp), Pulse duration 250 Micro sec, 60 min per session with routine medical care and dressing. The third group (c) L-TENS, encompasses twenty participants who received low-frequency TENS (1-5) HZ; Intensity (30 -80 amp), Pulse duration 250 Micro sec, 60 min per session with routine medical care and dressing. All the participants were examined before and after two months of intervention; four weeks (post1), then after eight weeks (post2). Participants were examined by using (image j) to measure the ulcer area. Saline was used for measuring the ulcer volume, and a visual analog scale was adopted to evaluate pain. After drawing a comparison among the three groups after four weeks and after eight weeks of treatment, a statistically significant decrease (P <0.05) in wound surface area, wound volume, and pain in favor of L-TENS was noticed. It has been found that L- TENS is more effective than H -TENS and is highly recommended in the treatment protocol for such debilitating conditions.

Gender moderates the association between chronic academic stress with top-down and bottom-up attention

Research on the relationship between chronic stress and cognition is limited by a lack of concurrent measurement of state-anxiety, physiological arousal, and gender. For the first time, we assessed the impact of these factors on top-down/conscious (simple and choice reaction time) and bottom-up/reflexive (saccadic reaction time) measures of attention using CONVIRT virtual-reality cognitive tests. Participants (N = 163) completed measures of academic stress (effort-reward imbalance; ERI) and state-anxiety while heart-rate variability was recorded continuously throughout the experiment. Gender moderated the association between academic stress with the top-down measures (b = -0.002, t = -2.023, p = .045; b = -0.063, t = -3.080, p = .002) and higher academic stress was associated with poorer/slower reaction times only for male participants. For bottom-up attention, heart rate variability moderated the relationship between academic stress and saccadic reaction time (b = 0.092, t = 1.991, p = .048), and only female participants who were more stressed (i.e., ERI ≥ 1) and displayed stronger sympathetic dominance had slower reaction times. Our findings align with emerging evidence that chronic stress is related to hyperarousal in women and cognitive decrements in men. Our findings suggest that higher ERI and sympathetic dominance during cognitive testing was associated with poorer bottom-up attention in women, whereas for men, academic stress was related with poorer top-down attention irrespective of sympathovagal balance.

Clinical Experience of High Frequency and Low Frequency TENS in Treatment of Diabetic Neuropathic Pain in Russia

Background: Transcutaneous electrical nerve stimulation (TENS) is presently one of the main methods of treatment for neuropathic pain in type II diabetes mellitus. The discussion about which TENS frequency is more effective in the treatment of neuropathic pain has been ongoing for many years. Despite this, the response of different aspects of neuropathic pain to various TENS modalities has not been sufficiently studied. Aim: To analyze changes in characteristics of neuropathic pain depending on the frequency of TENS. Materials and methods: Seventy-five Russian diabetic patients with painful distal axonal neuropathy were enrolled in the study. Patients were assigned to three groups: in the HF TENS group, 25 patients received standard drug therapy (Alpha-lipoic acid, Pentoxifylline, Vitamin B12, Gabapentin) + high-frequency TENS (HF); in the LF TENS group, 25 patients received standard drug therapy (Alpha-lipoic acid, Pentoxifylline, Vitamin B12, Gabapentin) + low-frequency TENS (LF); in the control group, 25 patients underwent just standard drug therapy (Alpha-lipoic acid, Pentoxifylline, Vitamin B12, Gabapentin). Pain intensity was calculated before and after treatment with visual analogue scale (VAS), McGill pain questionnaire (MPQ), Douleur Neuropathique 4 Questions (DN4) and Pain Drawing. Results: TENS increased the therapeutic effect of standard drug therapy, in the treatment of neuropathic pain, by 65.9% and prolonged its efficacy by 31% for up to 6 months after treatment. HF TENS had a more pronounced analgesic effect than LF TENS based on VAS (34.7%), sensory (57.6%) MPQ dimensions and DN4 (21%). Affective MPQ dimension with the use of LF TENS was lower than HF TENS by 34.7% immediately after treatment, by 47.3% after 2 months and by 34.8% after 6 months of the follow-up period. Conclusion: There are significant differences between HF and LF TENS based on pain assessment using various pain scales. This reflects the distinctive effects of different TENS modalities on different aspects of neuropathic pain.

Effects of Acute Microcurrent Electrical Stimulation on Muscle Function and Subsequent Recovery Strategy

Microcurrent electrical neuromuscular stimulation (MENS) is believed to alter blood flow, increasing cutaneous blood perfusion, with vasodilation and hyperemia. According to these physiological mechanisms, we investigated the short-term effects of MENS on constant-load exercise and the subsequent recovery process. Ten healthy subjects performed, on separate days, constant-load cycling, which was preceded and followed by active or inactive stimulation to the right quadricep. Blood lactate, pulmonary oxygen, and muscle deoxyhemoglobin on-transition kinetics were recorded. Hemodynamic parameters, heart rate variability, and baroreflex sensitivity were collected and used as a tool to investigate the recovery process. Microcurrent stimulation caused a faster deoxyhemoglobin (4.43 ± 0.5 vs. 5.80 ± 0.5 s) and a slower VO₂ (25.19 ± 2.1 vs. 21.94 ± 1.3 s) on-kinetics during cycling, with higher lactate levels immediately after treatments executed before exercise (1.55 ± 0.1 vs. 1.40 ± 0.1 mmol/L) and after exercise (2.15 ± 0.1 vs. 1.79 ± 0.1 mmol/L). In conclusion, MENS applied before exercise produced an increase in oxygen extraction at muscle microvasculature. In contrast, MENS applied after exercise improved recovery, with the sympathovagal balance shifted toward a state of parasympathetic predominance. MENS also caused higher lactate values, which may be due to the magnitude of the muscular stress by both manual treatment and electrical stimulation than control condition in which the muscle received only a manual treatment.

[The use of transdermal electroneurostimulation in the rehabilitation of patients after surgical decompression of the carpal tunnel]

Most of the clinical and neurophysiological disorders of the median nerve that persisted in patients after surgical decompression of the carpal tunnel (DCT) are associated not with acute compression of the nerve, but with myelinoaxonopathic disorders in the structure of the nerve that developed as a result of prolonged compression.

OBJECTIVE

To study the effectiveness of transdermal electroneurostimulation (TENS) in the rehabilitation of patients with residual neurological deficit after surgical DCT.

MATERIAL AND METHODS

We observed 45 patients after DCT (6-12 months), aged 30 to 50 years (mean age 42±3 years). All patients were diagnosed with primary carpal tunnel syndrome with a lesion of the dominant hand, of which 15 patients received pharmacotherapy; 15 patients - in addition to pharmacotherapy, received a course of low-frequency high-amplitude TENS (NTENS) and 15 patients - a course of high-frequency low-amplitude TENS (VTENS).

RESULTS

The regression of positive sensory symptoms was more pronounced against the background of VTENS and NTENS than after the use of pharmacotherapy, on average 6.6 times (p<0.01). At the same time, VTENS turned out to be more effective than NTENS by 28.5% (p<0.05). In the long-term follow-up period (2 months), the severity of positive sensory symptoms decreased in patients who received VTENS and NTENS, by an average of 58.1% compared with the baseline values before treatment (p<0.05). The severity of Tinel's symptom in patients who received a course of VTENS decreased by 44%, after a course of NTENS - by 67%, and after pharmacotherapy - by 14%. It was found that NTENS compared with VTENS was 51% more effective in reducing Tinel's symptom (p<0.05) and by 64% - Falen's symptom (p<0.05). The decrease in the time to perform the Jebsen-Taylor test (JTT) after the use of pharmacotherapy was on average 9% (p>1.00), and after TENS - 23% (p<0.05). When comparing VTENS and NTENS among themselves, NTENS turned out to be more effective on average by 68% (p<0.05). An improvement in electro-kymographic parameters was revealed only after the use of VTENS. At the same time, the decrease in the residual latency was 21.3% and the increase in the amplitude of the M-response was 14.3%.

CONCLUSION

Transdermal electroneurostimulation is a highly effective method used in the complex treatment of patients with residual neurological disorders after undergoing surgical decompression of the carpal tunnel. The maximum regression of positive sensory symptoms develops against the background of high-frequency low-amplitude transcutaneous electroneurostimulation, and the maximum anti-inflammatory effect, the greatest improvement in the function of small hand muscles and statistically significant neurophysiological restoration of the function of the median nerve are revealed after the application of a course of low-frequency high-amplitude transcutaneous electroneurostimulation. At the same time, positive dynamics after low-frequency high-amplitude transcutaneous electroneurostimulation and high-frequency low-amplitude transcutaneous electroneurostimulation persists in the long-term period.

Transcutaneous electrical nerve stimulation attenuates cardiac sympathetic drive in heart failure: a 123MIBG myocardial scintigraphy randomized controlled trial

Cardiac sympathetic overdrive provides inotropic support to the failing heart. However, as myocardial insult evolves, this compensatory response impairs contractile function and constitutes an independent mortality predictor and a primary target in the treatment of heart failure (HF). In this prospective, randomized, double-blind, controlled crossover trial, we proposed cervicothoracic transcutaneous electrical nerve stimulation (CTENS) as a nonpharmacological therapy on cardiac sympathetic activity in patients with HF. Seventeen patients with HF were randomly assigned to an in-home CTENS (30 min twice daily, 80-Hz frequency, and 150-μs pulse duration) or a control intervention (Sham) for 14 consecutive days. Following a 60-day washout phase, patients were crossed over to the opposite intervention. The heart-to-mediastinum ratio (HMR) and washout rate (WR) (indexes of sympathetic innervation density and activity from planar ¹²³iodo-metaiodobenzylguanidine myocardial scintigraphy images, respectively), as well as blood pressure (BP) and heart rate (HR), were quantified before and after each intervention. HMR, BP, and HR did not change throughout the study. Nonetheless, CTENS reduced WR (CTENS -4 ± 10 vs. Sham +5 ± 15%, P = 0.03) when compared with Sham. When allocated in two independent groups, preserved (PCSI, HMR > 1.6, n = 10) and impaired cardiac sympathetic innervation (ICSI, HRM ≤1.6, n = 7), PCSI patients showed an important attenuation of WR (-11 ± 9 vs. Sham +8 ± 19%, P = 0.007) after CTENS. Nonetheless, neither Sham nor CTENS evoked changes in WR of the ICSI patients (P > 0.05). These findings indicate that CTENS attenuates the cardiac sympathetic overdrive in patients with HF and a preserved innervation constitutes an essential factor for this beneficial neuromodulatory impact. Clinical Trial Registration: URL: https://www.clinicaltrials.gov . Identifier: NCT03354689. NEW & NOTEWORTHY We found that short-term cervicothoracic transcutaneous electrical nerve stimulation (CTENS) attenuates cardiac sympathetic overdrive in patients with heart failure and a preserved autonomic innervation may constitute an essential factor to maximize this beneficial neuromodulatory effect. CTENS then emerges as an alternative noninvasive and nonpharmacological strategy to attenuate exaggerated cardiac sympathetic drive in patients with heart failure.

Attenuation of hypertension by C-fiber stimulation of the human median nerve and the concept-based novel device

High blood pressure (BP) is a highly controllable risk factor for cardiovascular diseases; however, awareness of this condition and the rates of controlled hypertension are low. Experimental animal studies have shown that stimulation of the median nerve or PC6 acupoint over the wrist has effects on cardiovascular activities, including reductions in systolic and diastolic BPs. A proof-of-concept study was conducted in humans to investigate whether stimulation of median nerve near PC6 acupoint decreased high BP, identify the optimal stimulation parameters for the BP-lowering effects of median nerve stimulation, and determine the specific peripheral nerves or types of afferent fibers mediating the BP-lowering effects. Median nerve stimulation was carried out bilaterally or unilaterally with different stimulation parameters, and the BP and heart rate were monitored. The afferent mechanisms underlying the effects of median nerve stimulation on hypertension were investigated via microneurography, A-fiber blocking experiments, and localized chemical or electrical stimulation. Bilateral median nerve stimulation at either low or high frequencies produced profound but transient reductions in systolic BP, which were elicited when median nerve stimulation was unilaterally applied at interelectrode distances of 2 and 4 cm. Systolic BP was also reduced by electrical stimulation of the thumb on the palm side. Although microneurographic recordings revealed the excitation of both A- and C-fibers following median nerve stimulation, the median nerve-mediated reductions in BP were not affected by A-fiber blockade, and they were mimicked by the activation of C-fibers with capsaicin. The present results indicate that activation of C-fibers in the median nerve generates BP-lowering effects in humans. Based on our clinical study, an optimized median nerve stimulator was built and combined with a wrist BP monitor for simultaneous BP measurements and median nerve stimulation.

Immediate effects of transcutaneous electrical nerve stimulation (TENS) administered during resistance exercise on pain intensity and physical performance of healthy subjects: a randomized clinical trial

PURPOSE

Exercise-induced muscle pain is a self-limiting condition which impacts physical activity habits. Transcutaneous electrical nerve stimulation (TENS) promotes pain reduction and functional improvement in different pain conditions. We propose that applying TENS during exercise might reduce pain and improve physical performance. Thus, we aimed to investigate immediate effects of TENS applied during resistance exercise.

METHODS

Healthy subjects of both sexes, irregularly active or sedentary were assigned into two groups: active (n = 24) or placebo (n = 22) TENS. The study was conducted over five moments: on day 0, subjects were recruited, on day 1 subjects performed the one-repetition maximum test (1RM); 72 h later, on day 2, 1RM was retested; 48 h later, on day 3, TENS was applied during a functional-resisted exercise protocol for upper limbs (bench press and rowing), with an intensity of 80% of 1RM; and 24 h after, on day 4, subjects were reevaluated. Assessment included pain intensity at rest and with movement, pressure pain thresholds, and muscle fatigue.

RESULTS

TENS did not reduce pain intensity when compared to placebo (p > 0.05). TENS reduce PPT in the latissmus dorsi: p = 0.02 and anterior tibialis: p = 0.04 in immediate reassessment. Immediate effects of TENS were significant for fatigue perception at rest (p = 0.01) and number of maximum repetitions during exercise sets, starting from the 5th set of rowing exercise (p = 0.002).

CONCLUSION

Our results show that TENS did not reduce pain perception in healthy individuals, but its use induced increased muscle action, contributing to a greater fatigue perception.

The Effect of Transcutaneous Electrical Nerve Stimulation of Sympathetic Ganglions and Acupuncture Points on Distal Blood Flow

Transcutaneous electrical nerve stimulation (TENS) is a widely-practiced method to increase blood flow in clinical practice. The best location for stimulation to achieve optimal blood flow has not yet been determined. We compared the effect of TENS application at sympathetic ganglions and acupuncture points on blood flow in the foot of healthy individuals. Seventy-five healthy individuals were randomly assigned to three groups. The first group received cutaneous electrical stimulation at the thoracolumbar sympathetic ganglions. The second group received stimulation at acupuncture points. The third group received stimulation in the mid-calf area as a control group. Blood flow was recorded at time zero as baseline and every 3 minutes after baseline during stimulation, with a laser Doppler flow-meter. Individuals who received sympathetic ganglion stimulation showed significantly greater blood flow than those receiving acupuncture point stimulation or those in the control group (p<0.001). Data analysis revealed that blood flow at different times during stimulation increased significantly from time zero in each group. Therefore, the application of low-frequency TENS at the thoracolumbar sympathetic ganglions was more effective in increasing peripheral blood circulation than stimulation at acupuncture points.

An experimental examination of the effort-reward imbalance model of occupational stress: Increased financial reward is related to reduced stress physiology

Effort-reward imbalance in the workplace is linked to a variety of negative health and organisational outcomes, but it has rarely been assessed experimentally. We manipulated reward (while keeping effort constant) in a within-subjects design with female participants (N=60) who were randomly assigned to high and standard reward conditions within a simulated office environment. Self-report, behavioural (task performance), and physiological (heart rate variability, salivary alpha amylase) measures assessed the impact of increased financial reward. Participants reported increased perceptions of reward, performed moderately better on the task, and were less physiologically reactive in the high reward versus the standard condition. These findings highlight the importance of assessing both subjective self-reports of stress together with objective physiological measures of stress, and suggest that increasing monetary rewards has the potential to decrease stress physiological reactivity, and in turn, reduce the risk of ill-health in employees, and may also positively influence task efficacy.

Hemodynamic Effects Induced by Transcutaneous Electrical Nerve Stimulation in Apparently Healthy Individuals: A Systematic Review With Meta-Analysis

OBJECTIVE

To determine the immediate effects of transcutaneous electrical nerve stimulation (TENS) on heart rate, systolic blood pressure (SBP), and diastolic blood pressure (DBP) in apparently healthy adults (age ≥18y).

DATA SOURCES

The Cochrane Library (online version 2014), PubMed (1962-2014), EMBASE (1980-2014), and LILACS (1980-2014) electronic databases were searched.

STUDY SELECTION

Randomized controlled trials were included when TENS was administered noninvasively with surface electrodes during rest, and the effect of TENS was compared with that of control or placebo TENS. A sensitive search strategy for identifying randomized controlled trials was used by 2 independent reviewers. The initial search led to the identification of 432 studies, of which 5 articles met the eligibility criteria.

DATA EXTRACTION

Two independent reviewers extracted data from the selected studies. Quality was evaluated using the PEDro scale. Mean differences or standardized mean differences in outcomes were calculated.

DATA SYNTHESIS

Five eligible articles involved a total of 142 apparently healthy individuals. Four studies used high-frequency TENS and 3 used low-frequency TENS and evaluated the effect on SBP. Three studies using high-frequency TENS and 2 using low-frequency TENS evaluated the effect on DBP. Three studies using high-frequency TENS and 1 study using low-frequency TENS evaluated the effect on heart rate. A statistically significant reduction in SBP (-3.00mmHg; 95% confidence interval [CI], -5.02 to -0.98; P=.004) was found using low-frequency TENS. A statistically significant reduction in DBP (-1.04mmHg; 95% CI, -2.77 to -0.03; I(2)=61%; P=.04) and in heart rate (-2.55beats/min; 95% CI, -4.31 to -0.78; I(2)=86%; P=.005]) was found using both frequencies. The median value on the PEDro scale was 7 (range, 4-8).

CONCLUSIONS

TENS seems to promote a discrete reduction in SBP, DBP, and heart rate in apparently healthy individuals.

Effect of transcutaneous electrical nerve stimulation on peripheral to central blood pressure ratio in healthy subjects

PURPOSE

To investigate the effect of transcutaneous electrical nerve stimulation (TENS) on the arterial stiffness in healthy young adult and middle-aged men using the augmentation index (AI-x) and hemodynamic measures.

METHODS

Twenty-four men (12 aged 27·25 ± 5·53 years and 12 aged 54·83 ± 5·10 years) were randomly allocated to two subgroups: TENS or placebo in ganglion region for 45 min. The AI-x and hemodynamic measures [late systolic blood pressure (SBP), central blood pressure (CBP), difference between P1 and P2 (ΔP) and tension time index (TTI)] were determined before and after protocols.

RESULTS

TENS resulted in reduction of SBP in younger adults (TENSpre: 111 ± 2; post: 105 ± 2·2 mm Hg; PLACEBOpre: 113 ± 1·8; post: 114 ± 2·5 mm Hg; GEE, P<0·01), whereas no difference was found in middle-aged group. TENS also resulted in reduction of AI-x younger adults group (TENSpre: 56 ± 2·8; post: 53 ± 2%; PLACEBOpre: 55 ± 3; post: 58 ± 2·5%; GEE, P<0·01). ΔP and TTI were significantly decreased after the application of TENS in both groups, but significantly greater reductions in TTI and the SBP/CBP ratio were found in the group of younger adults.

CONCLUSIONS

The acute application of ganglion TENS attenuated arterial stiffness in younger adults as well as hemodynamic measures in the middle-aged group. This method could emerge as effective therapy for the management of arterial blood pressure.

Effects of transcutaneous electrical nerve stimulation on fetal and placental development in an experimental model of placental insufficiency

OBJECTIVE

To elucidate the effects of transcutaneous electrical nerve stimulation (TENS) in pregnancies with placental insufficiency.

METHODS

Pregnant rats were subjected to uterine artery ligation and to TENS according to the following groups: ligated stimulated (LS); ligated non-stimulated (LN), control stimulated (CS); and control non-stimulated (CN). Fetal external measurements, such as crown-rump length (CRL), fronto-occipital distance (FOD), thoracic ventral-dorsal (TVDD) and abdominal ventral-dorsal (AVDD) distances were analyzed together with the area occupied by fetal internal organs. Glucose transporter 1 (GLUT-1) expression was evaluated by immunohistochemistry in fetal organs. Thickness of junctional, labyrinth and intermediate placental zones was analyzed by morphometric evaluation in HE-stained slides, and placental hypoxia-inducible factor 1 alfa expression was measured by real-time polymerase chain reaction.

RESULTS

In LN and CS groups compared to the CN group, CRL was reduced (27.51/28.95 versus 30.16 mm), as well as FOD (6.63/6.63 versus 7.36 mm), AVDD (7.38/8.00 versus 8.61 mm) and TVDD (6.46/6.87 versus 7.23 mm). Brain GLUT-1 expression was higher in LS (1.3%) and CS (1.8%). The area occupied by placental vessels in the labyrinth zone (29.67 ± 3.51 versus 20.83 ± 7.63) and intermediate zone (26.46 ± 10.21 versus 10.86 ± 8.94) was larger in the LS group than in the LN group.

CONCLUSIONS

Our results suggest a negative effect of TENS on placental development, thus compromising the maintenance of adequate blood flow to the fetus.

An experimental study of the job demand-control model with measures of heart rate variability and salivary alpha-amylase: Evidence of increased stress responses to increased break autonomy

We assessed in an experimental design whether the stress response towards a work task was moderated by the autonomy to choose a break during the assigned time to complete the task. This setting is defined in accordance with the theoretical framework of the job-demand-control (JDC) model of work related stress. The findings from naturalistic investigations of a stress-buffering effect of autonomy (or 'buffer hypothesis') are equivocal and the experimental evidence is limited, especially with relation to physiological indices of stress. Our objective was to investigate if increased autonomy in a particular domain (break time control) was related with adaptive physiology using objective physiological markers of stress; heart rate variability (HRV) and salivary alpha amylase (sAA). We used a within-subject design and the 60 female participants were randomly assigned to an autonomy (free timing of break) and standard conditions (fixed timing of break) of a word processing task in a simulated office environment in a random order. Participants reported increased perceptions of autonomy, no difference in demand and performed worse in the task in the break-time autonomy versus the standard condition. The results revealed support for the manipulation of increased autonomy, but in the opposing direction. Increased autonomy was related with dysregulated physiological reactivity, synonymous with typical increased stress responses. Potentially, our findings may indicate that autonomy is not necessary a resource but could become an additional stressor when it adds additional complexity while the amount of work (demands) remains unchanged. Further, our findings underscore the need to collect objective physiological evidence of stress to supplement self-reported information. Self-report biases may partially explain the inconsistent findings with the buffer hypothesis.

Sympathetic ganglion transcutaneous electrical nerve stimulation after coronary artery bypass graft surgery improves femoral blood flow and exercise tolerance

We tested the hypothesis that transcutaneous electrical nerve stimulation (TENS) over the stellate ganglion region would reduce sympathetic overstimulation and improve femoral blood flow (FBF) after coronary artery bypass graft surgery. Thirty-eight patients (20 men, 24 New York Heart Association class III-IV) were randomized to 5-day postoperative TENS (n = 20; 4 times/day; 30 min/session) or sham TENS (n = 18) applied to the posterior cervical region (C7-T4). Sympathetic nervous system was stimulated by the cold pressor test, with FBF being measured by ultrasound Doppler. Femoral vascular conductance (FVC) was calculated as FBF/mean arterial pressure (MAP). Six-min walking distance established patients' functional capacity. Before and after the intervention periods, pain scores, opiate requirements, and circulating β-endorphin levels were determined. As expected, preoperative MAP increased and FBF and FVC decreased during the cold pressor test. Sham TENS had no significant effect on these variables (P > 0.05). In contrast, MAP decreased in the TENS group (125 ± 12 vs. 112 ± 10 mmHg). This finding, in association with a consistent increase in FBF (95 ± 5 vs. 145 ± 14 ml/min), led to significant improvements in FVC (P < 0.01). Moreover, 6-min walking distance improved only with TENS (postsurgery-presurgery = 35 ± 12 vs. 6 ± 10 m; P < 0.01). TENS was associated with lesser postoperative pain and opiate requirements but greater circulating β-endorphin levels (P < 0.05). In conclusion, stellate ganglion TENS after coronary artery bypass graft surgery positively impacted on limb blood flow during a sympathetic stimulation maneuver, a beneficial effect associated with improved clinical and functional outcomes.

Improvement of exercise capacity and peripheral metaboreflex after bariatric surgery

BACKGROUND

Bariatric surgery is the only predictable method to obtain weight loss in severe obesity. Poor physical performance of obese individuals may be mediated by the peripheral metaboreflex, which controls blood flow redistribution to exercising muscles. Weight reduction improves exercise capacity through several possible mechanisms that are insufficiently understood. We hypothesized that the metaboreflex is one among the causes of improvement in exercise capacity after weight loss. This study thus aimed to examine the effect of bariatric surgery on exercise performance and metaboreflex.

METHODS

Severely obese patients were assessed before and 3 months after bariatric surgery. Metaboreflex was evaluated by the technique of selective induction by post-exercise circulatory occlusion (PECO+) after isometric handgrip exercise at 30% of maximum voluntary contraction. The exercise capacity was assessed by 6-min walking test.

RESULTS

Seventeen patients completed the protocol. Body mass index decreased from 46.4 ± 2 to 36.6 ± 2 kg/m2 (P < 0.001). The distance walked in 6 min increased from 489 ± 14 to 536 ± 14 m (P < 0.001). The peripheral metaboreflex activity, expressed by the area under the curve of vascular resistance, was lower after than before bariatric surgery (42 ± 5 to 20 ± 4 units, P = 0.003). Heart rate, blood pressure, and vascular resistance were also significantly decreased. The correlation between change in distance walked in 6 min and change in peripheral metaboreflex activity was not significant.

CONCLUSIONS

Weight loss after bariatric surgery increases exercise capacity and reduces peripheral metaboreflex, heart rate, and blood pressure. Further investigation on the role of metaboreflex regarding mechanisms of exercise capacity of individuals with obesity is warranted.

Effects of different frequencies of transcutaneous electrical nerve stimulation on venous vascular reactivity

Transcutaneous electrical nerve stimulation (TENS) is a type of therapy used primarily for analgesia, but also presents changes in the cardiovascular system responses; its effects are dependent upon application parameters. Alterations to the cardiovascular system suggest that TENS may modify venous vascular response. The objective of this study was to evaluate the effects of TENS at different frequencies (10 and 100 Hz) on venous vascular reactivity in healthy subjects. Twenty-nine healthy male volunteers were randomized into three groups: placebo (n=10), low-frequency TENS (10 Hz, n=9) and high-frequency TENS (100 Hz, n=10). TENS was applied for 30 min in the nervous plexus trajectory from the superior member (from cervical to dorsal region of the fist) at low (10 Hz/200 μs) and high frequency (100 Hz/200 μs) with its intensity adjusted below the motor threshold and intensified every 5 min, intending to avoid accommodation. Venous vascular reactivity in response to phenylephrine, acetylcholine (endothelium-dependent) and sodium nitroprusside (endothelium-independent) was assessed by the dorsal hand vein technique. The phenylephrine effective dose to achieve 70% vasoconstriction was reduced 53% (P<0.01) using low-frequency TENS (10 Hz), while in high-frequency stimulation (100 Hz), a 47% increased dose was needed (P<0.01). The endothelium-dependent (acetylcholine) and independent (sodium nitroprusside) responses were not modified by TENS, which modifies venous responsiveness, and increases the low-frequency sensitivity of α1-adrenergic receptors and shows high-frequency opposite effects. These changes represent an important vascular effect caused by TENS with implications for hemodynamics, inflammation and analgesia.