Nociceptive flexion reflexes elicited by noxious laser radiant heat in man

This study, carried out in humans, is an attempt to elicit nociceptive flexion reflexes and to investigate the sensation reported by the subjects, using thermal stimulation achieved with laser radiant heat. It was found that noxious thermal stimulation elicited long latency nociceptive reflexes very well correlated with a pricking pain. Since thermal stimulus is more specific and natural than an electrical one, it seems that this method should be of interest for pain research in man.     

Analgesia after lesions of nucleus reticularis magnocellularis: differential effect on supraspinal versus spinal pain reflexes

The present studies examine the effect of bilateral electrolytic lesions of descending fibers arising from nucleus reticularis magnocellularis (NMC) on responding to noxious peripheral thermal or mechanical stimulation and on spinal cord monoamine levels. The lesion effects were quantified by examining two supraspinally organized pain responses, the hot plate latency and vocalization threshold and two spinally organized nociceptive reflexes, tail flick latency and hind limb flexion threshold. Following interruption of descending NMC fibers, a profound analgesia was observed on supraspinally organized pain responses. Assay of spinal cord serotonin (5-HT) indicated that the NMC lesions also destroyed appreciable numbers of descending 5-HT fibers of passage originating in nucleus raphe magnus (RM). A modest hypersensitivity to pain occurred after control lesions in RM suggesting that the analgesia observed after NMC lesions would have been even more pronounced if RM fibers of passage had not been concomitantly destroyed. To assess whether the analgesia observed after NMC lesions was due to non-specific destruction of a given volume of reticular tissue, control lesions were placed in nucleus subcoeruleus (NSC). NSC lesions resulted in a hypersensitivity to pain and significant depletion of spinal cord noradrenaline (NA). These data suggest both that the analgesia observed after NMC lesions was not due to non-specific destruction of the reticular formation, and that descending NSC NA fibers tonically suppress pain. The above analgesic effects were observed exclusively on supraspinally organized pain responses, not spinally organized nociceptive reflexes. This supported previous studies demonstrating differential descending control of nociception in the spinal versus intact preparations. In summary, the present data suggest that descending NMC fibers tonically suppress ascending pain transmission.     

Sex differences in perceived pain are affected by an anxious brain

Decades of research confirm that women have greater pain sensitivity than men. Women also show greater overall anxiety sensitivity than men. Given these differences, we hypothesized that sex differences in anxiety would explain sex differences in experienced pain and physiological responses to pain (at both spinal and cortical levels). By measuring subjective pain, state/trait anxiety, nociceptive flexion reflexes, and somatosensory evoked potentials (SEPs), it was possible to test the effects of anxiety on the processing of painful drives at different levels of the neuraxis while also documenting the role played by anxiety on sex differences in experienced pain. Results confirm that women are indeed more sensitive to pain than men. Importantly, this difference was accompanied by a significant sex difference in cortical activity (SEP amplitude) but not spinal nociceptive activity, suggesting that much of the sex difference in experienced pain is attributable to variations in thalamocortical processing and to ensuing changes in the appraisal of and/or emotional response to noxious insult. In support of this claim, we found that sex differences in cortical activity and subjective pain disappeared when trait anxiety was controlled for. This means that stable predispositions to respond with heightened apprehension contribute to baseline pain sensitivity differences between the sexes. These results indicate that the modulatory effect of affect on pain-related brain processes may explain why men and women experience painful shocks so differently. In our study, the mediating role of anxiety on sex differences in pain was tested and confirmed using path analysis.     

Pain-related fear, lumbar flexion, and dynamic EMG among persons with chronic musculoskeletal low back pain

OBJECTIVES: The purpose of this study was to examine the relationship between pain-related fear, lumbar flexion, and dynamic EMG activity among persons with chronic musculoskeletal low back pain. It was hypothesized that pain-related fear would be significantly related to decreased lumbar flexion and specific patterns of EMG activity during flexion and extension. STUDY DESIGN: Data was obtained from subjects who, on a single day, completed self-report measures of pain and pain-related fear, and were interviewed to determine demographic and pain information. Subjects then underwent a dynamic EMG evaluation for which they were asked to stand, then bend forward as far as possible, stay fully flexed, and return to standing. Lumbar EMG and angle of flexion were recorded during this time. A flexion-relaxation ratio (FRR) was computed by comparing maximal EMG while flexing to the average EMG in full flexion. SUBJECTS: Seventy-six persons with chronic musculoskeletal low back pain. RESULTS: Zero-order correlations indicated that pain-related fear was significantly related to reduced lumber flexion (r = -0.55), maximum EMG during flexion (r = -0.38) and extension (r = -0.51), and the FRR (r = -0.40). When controlling for pain and demographic factors, pain-related fear continued to be related to reduced lumbar flexion. Using a path-analytic model to examine whether angle of flexion mediated the relationship between fear and EMG activity, the models examining maximal EMG during flexion and extension supported the notion that pain-related fear influences these measures indirectly through its association with decreased range of motion. Conversely, pain-related fear was independently related to higher average EMG in full flexion, while angle of flexion was not significantly related. Pain-related fear was directly related to a smaller FRR, as well as indirectly through angle of flexion. CONCLUSIONS: Pain-related fear is significantly associated with reduced lumbar flexion, greater EMG in full flexion, and a smaller FRR. The relationship between pain-related fear and EMG during flexion and extension appears to be mediated by reduced lumbar flexion. These results suggest that pain-related fear is directly associated with musculoskeletal abnormalities observed among persons with chronic low back pain, as well as indirectly through limited lumbar flexion. These musculoskeletal abnormalities as well as limited movement may be involved in the development and maintenance of chronic low back pain. In addition, changes in musculoskeletal functioning and flexion associated with pain-related fear may warrant greater attention as part of treatment.     

Fear-avoidance beliefs as measured by the fear-avoidance beliefs questionnaire: change in fear-avoidance beliefs questionnaire is predictive of change in self-report of disability and pain intensity for patients with acute low back pain

OBJECTIVES: The purposes of this study were to investigate the association among measures of fear-avoidance beliefs, pain intensity, and lumbar flexion and to determine if changes in these measures were predictive of treatment outcome following physical therapy for acute low back pain. It was hypothesized that items of the Fear-Avoidance Beliefs Questionnaire would be correlated with concurrent measures of pain intensity and lumbar flexion. In addition, it was hypothesized that changes in fear-avoidance beliefs would be predictive of changes in self-report of pain intensity and disability. STUDY DESIGN: Patients underwent a standard examination that included measures of fear-avoidance beliefs, pain intensity, lumbar flexion, and disability from low back pain. Patients were then re-examined after 4 weeks of physical therapy treatment. PATIENTS: Sixty-three patients with acute low back pain enrolled in a clinical trial of physical therapy treatment. RESULTS: Fear-Avoidance Beliefs Questionnaire items were consistently correlated with lumbar flexion, but not with measures of pain intensity. Pearson correlations indicated that changes in disability were significantly associated with changes in fear-avoidance beliefs and pain intensity, but not changes in lumbar flexion. Changes in fear-avoidance beliefs explained significant amounts of variance in changes in average pain intensity while controlling for changes in lumbar flexion. Changes in fear-avoidance beliefs explained significant amounts of variance in changes in disability while controlling for changes in average pain intensity. CONCLUSIONS: These results suggest that fear-avoidance beliefs have a similar association with pain intensity, physical impairment, and disability for patients with acute and chronic low back pain. This study provides preliminary support for the use of the Fear-Avoidance Beliefs Questionnaire as an outcome measure for patients with acute low back pain.     

Effects of static flexion-relaxation on paraspinal reflex behavior

BACKGROUND: Static trunk flexion working postures and disturbed trunk muscle reflexes are related to increased risk of low-back pain. Animal studies conclude that these factors may be related; passive tissue strain in spinal ligaments causes subsequent short-term changes in reflex. Although studies have documented changes in the myoelectric onset angle of flexion-relaxation following prolonged static flexion and cyclic flexion we could find no published evidence related to the human reflex response of the trunk extensor muscles following a period of static flexion-relaxation loading. METHODS: Eighteen subjects maintained static lumbar flexion for 15 min. Paraspinal muscle reflexes were elicited both before and after the flexion-relaxation protocol using pseudorandom stochastic force disturbances while recording EMG. Reflex gain was computed from the peak value of the impulse response function relating input force perturbation to EMG response using time-domain deconvolution analyses. FINDINGS: Reflexes showed a trend toward increased gain after the period of flexion-relaxation (P < 0.055) and were increased with trunk extension exertion (P < 0.021). Significant gender differences in reflex gain were observed (P < 0.01). INTERPRETATIONS: Occupational activities requiring extended periods of trunk flexion contribute to changes in reflex behavior of the paraspinal muscles. Results suggest potential mechanisms by which flexed posture work may contribute to low-back pain. Significant gender differences indicate risk analyses should consider personal factors when considering neuromuscular behavior.     

The influence of patellofemoral pain on lower limb loading during gait

Objective. To determine if subjects with patellofemoral pain demonstrate excessive lower limb loading during gait.

Design. Prospective study utilizing a group of patients with patellofemoral pain and a control group.

Background. Increased rate of lower limb loading has been hypothesized as being contributory to knee osteoarthritis and may be the result of decreased knee flexion during weight acceptance. Since patients with patellofemoral pain have been reported to limit knee flexion during gait, these individuals may be at risk for the adverse effects of impulse loading.

Methods. Force plate parameters, lower extremity kinematics and stride characteristics were recorded in 15 females with patellofemoral pain and 10 pain-free controls during self-selected free and fast walking velocities.

Results. Individuals in the patellofemoral pain group demonstrated a significantly slower gait velocity during the free and fast trials as well as decreased stance phase knee flexion during fast walking. The average peak loading rate for the patellofemoral pain group was significantly less than the control group during both free (P=0.004) and fast walking (P=0.03).

Conclusions. Despite diminished stance phase knee flexion during fast walking, subjects with patellofemoral pain did not demonstrate increased lower limb loading. During gait, the ground reaction forces appeared to be minimized by adopting a slower walking velocity.

Relevance

These results indicate that altered knee kinematics as a result of patellofemoral pain do not place these individuals at risk for the adverse effects of impulse loading.     

Neurophysiological assessment of craniofacial pain

This review deals with the diagnostic usefulness of neurophysiological testing in patients with craniofacial pain. Neurophysiological testing of trigeminal nerve function relies on trigeminal reflexes and laser–evoked potentials (LEPs). This review briefly describes the physiology of trigeminal reflexes and LEPs, reports normal values and highlights the neurophysiological abnormalities in the main clinical conditions.     

Transcutaneous electrical nerve stimulation: nonparallel antinociceptive effects on chronic clinical pain and acute experimental pain

OBJECTIVE: To investigate to what extent a single 60-minute session of transcutaneous electrical nerve stimulation (TENS) would modify chronic clinical pain, acute experimental pain, and the flexion reflex evoked in chronic low back pain patients. STUDY DESIGN: Thirty young subjects with chronic low back pain were randomly allocated to two groups, receiving either TENS or placebo stimulation to the lumbosacral region for 60 minutes. The flexion reflex was elicited by an electrical stimulation applied to the subject's right sole and recorded electromyographically from the biceps femoris and the tibialis anterior muscles. MAIN OUTCOME MEASURES: Subjective sensation of low back pain and the electrically induced pain were measured by two separate visual analog scales, termed VAS(LBP) and VAS(FR), respectively. Data obtained before, during, and 60 minutes after TENS and placebo stimulations were analyzed using repeated measures ANOVA. RESULTS: The VAS(LBP) score was significantly reduced to 63.1% of the prestimulation value after TENS (p<.001), but the reduction was negligible after placebo stimulation (to 96.7%, p = .786). In contrast, no significant change was found in the VASFR score (p = .666) and the flexion reflex area (p = .062) during and after stimulation within each group and between the two groups (p = .133 for VASFR and p = .215 for flexion reflex area). CONCLUSIONS: The same TENS protocol had different degrees of antinociceptive influence on chronic and acute pain in chronic low back pain patients.     

Correlation between change in pain,disability, and surface electromyography topographic parameters after interferential current treatment in patients with chronic low back pain

[Purpose] Surface electromyography (SEMG) topography is used to objectively assess patients with low back pain (LBP). This study aimed to investigate the correlation between SEMG topographic variables, pain, and disability in patients with chronic LBP (CLBP) after interferential current (IFC) treatment, and to evaluate IFC treatment efficacy using SEMG topography. [Participants and Methods] Twenty nine patients with CLBP were recruited for a 6-week IFC treatment. Pain and disability scores, and the root-mean-square difference (RMSD) of SEMG topographic variables (relative areas [RAs] at flexion and extension) were compared before and after the intervention by repeated measures ANOVA; the correlation between variables was also explored and p-value was set at 0.001. [Results] Significant positive correlations between changes in pain score and the RMSD of RA at flexion (r(29)=0.593), and between changes in pain and disability scores (r(29)=0.426) were observed. All participants showed statistically significant improvements in the RMSD of RA at flexion, pain score, and disability score after IFC treatment. [Conclusion] SEMG topographic variables are closely associated with changes in pain score in patients with CLBP after IFC treatment. The RMSD of RA at flexion can be used as an objective marker in IFC treatment efficacy evaluation.     

Emotional modulation of spinal nociception and pain: the impact of predictable noxious stimulation

Recent evidence suggests that emotional picture-viewing is a reliable method of engaging descending modulation of spinal nociception. The present study attempted to replicate these findings and determine the effect of noxious stimulus predictability. Participants viewed pictures from the International Affective Picture System (IAPS), during which pain and nociceptive flexion reflexes (NFR) were elicited by electric shocks delivered to the sural nerve. For half of the participants (n=25) shocks were preceded by a cue (predictable), whereas the other half received no cue (unpredictable). Results suggested emotion was successfully induced by pictures, but the effect of picture-viewing on the NFR was moderated by the predictability of the shocks. When shock was unpredictable, spinal nociception (NFR) and pain ratings were modulated in parallel. Specifically, pain and NFR magnitudes were lower during pleasant emotions and higher during unpleasant emotions. However, when shocks were predictable, only pain was modulated in this way. NFRs from predictable shocks were not altered by pictures. Further, exploratory analyses found that pain ratings, but not NFRs, were lower during predictable shocks. These data suggest emotional picture-viewing is a reliable method of engaging descending modulation of spinal nociception. However, descending modulation could not be detected in NFRs resulting from predictable noxious stimuli. Although preliminary, this study implies that separate mechanisms are responsible for emotional modulation of nociception at spinal vs. supraspinal levels, and that predictable noxious events may disengage modulation at the spinal level. The current paradigm could serve as a useful tool for studying descending modulation.     

Laboratory pain perception and clinical pain in post-menopausal women and age-matched men with osteoarthritis: relationship to pain coping and hormonal status

The present study examined relationships between pain coping, hormone replacement therapy, and laboratory and clinical pain reports in post-menopausal women and age-matched men with osteoarthritis. Assessment of nociceptive flexion reflex threshold was followed by an assessment of electrocutaneous pain threshold and tolerance. Participants rated their arthritis pain using the Arthritis Impact Measurement Scales. To assess pain coping, participants completed measures of emotion-focused coping, problem-focused coping, and pain catastrophizing. Results indicated that women were more likely than men to report using emotion-focused pain strategies, and that emotion-focused coping was associated with more arthritic pain and lower electrocutaneous pain tolerance. Correlations between coping measures and pain reports revealed that catastrophizing was associated with greater arthritis pain and lower pain threshold and tolerance levels. However, catastrophizing was not related to nociceptive flexion reflex threshold, suggesting that the observed relationship between catastrophizing and subjective pain does not rely on elevated nociceptive input. A comparison of men (n=58), post-menopausal women receiving hormone replacement therapy (n=32), and post-menopausal women not receiving hormone replacement therapy (n=42) revealed no significant group differences in arthritis pain, electrocutaneous pain threshold or tolerance, or nociceptive flexion reflex threshold. Thus, older adults with osteoarthritis do not exhibit the pattern of sex differences in response to experimental pain procedures observed in prior studies, possibly due to the development of disease-related changes in pain coping strategies. Accordingly, individual differences in clinical and experimental pain may be better predicted by pain coping than by sex or hormonal differences.     

Physical therapy for chronic low back pain: correlations between spinal mobility and treatment outcome

Chronic low back pain in 151 men aged 54 to 63 years was treated for three weeks in a rehabilitation centre or as outpatients at a health centre. Spinal mobility of forward and lateral flexion, and rotation, were measured before and two months after treatment. The effects of the treatment on low back pain were recorded from questionnaires answered before and 2, 6 and 12 months after treatment. A favourable outcome correlated significantly with an increase of spinal lateral flexion (p less than 0.01) and rotation (p less than 0.05). The hypothetical utility of mobilizing lateral flexion and rotation exercises as part of the rehabilitation of patients with chronic low back pain is discussed.     

Skeletal muscle stiffness and pain following eccentric exercise of the elbow flexors

Stiffness and pain occurring after eccentric exercise have been studied in human elbow flexor muscles. Increased muscle stiffness and flexion deformities of the elbow developed immediately after the exercise and were greatest 1-4 days later. Muscle tenderness and pain experienced during elbow extension developed more slowly but were both maximal at the same time as the muscle stiffness. EMG recordings at times when there was pain and flexion deformity showed the biceps to be electrically silent. This demonstrates that the pain was not due to sustained electrical activity in the muscle and the flexion was a consequence of shortening of non-contractile elements, presumably the connective tissue. It is suggested that some response to damaged connective tissue may cause increased mechanical sensitivity of muscle receptors which, in turn, gives rise to pain when the muscle is stretched or pressed.     

Electrical stimulation of motor cortex for pain control: a combined PET-scan and electrophysiological study.

Although electrical stimulation of the precentral gyrus (MCS) is emerging as a promising technique for pain control, its mechanisms of action remain obscure, and its application largely empirical. Using positron emission tomography (PET) we studied regional changes in cerebral flood flow (rCBF) in 10 patients undergoing motor cortex stimulation for pain control, seven of whom also underwent somatosensory evoked potentials and nociceptive spinal reflex recordings. The most significant MCS-related increase in rCBF concerned the ventral-lateral thalamus, probably reflecting cortico-thalamic connections from motor areas. CBF increases were also observed in medial thalamus, anterior cingulate/orbitofrontal cortex, anterior insula and upper brainstem; conversely, no significant CBF changes appeared in motor areas beneath the stimulating electrode. Somatosensory evoked potentials from SI remained stable during MCS, and no rCBF changes were observed in somatosensory cortex during the procedure. Our results suggest that descending axons, rather than apical dendrites, are primarily activated by MCS, and highlight the thalamus as the key structure mediating functional MCS effects. A model of MCS action is proposed, whereby activation of thalamic nuclei directly connected with motor and premotor cortices would entail a cascade of synaptic events in pain-related structures receiving afferents from these nuclei, including the medial thalamus, anterior cingulate and upper brainstem. MCS could influence the affective-emotional component of chronic pain by way of cingulate/orbitofrontal activation, and lead to descending inhibition of pain impulses by activation of the brainstem, also suggested by attenuation of spinal flexion reflexes. In contrast, the hypothesis of somatosensory cortex activation by MCS could not be confirmed by our results.     

Origin of neck pain and direction of movement influence dynamic cervical joint motion and pressure pain sensitivity

BackgroundPatients with neck pain normally showed alterations in cervical motion and pressure pain sensitivity. Cervical joints show scattered motions opposite to (anti-directional) the primary motion direction (pro-directional) during dynamic cervical flexion and extension. This study aimed to assess dynamic cervical joint motion and pressure pain sensitivity when pain originated from different cervical muscles which may have clinical relevance in diagnosis of impairments related with neck pain.MethodsFluoroscopic video recordings of cervical flexion and extension were collected from fifteen healthy subjects before and during hypertonic saline-induced pain in right multifidus and trapezius muscles. Cervical flexion and extension motions were divided into 10 epochs with respect to time. Pro-directional, anti-directional, and total joint motion were extracted across epochs as well as joint motion variability. Pressure pain thresholds (PPTs) were assessed bilaterally over C2/C3 and C5/C6 facet joints.FindingsCompared with baseline: 1) Multifidus muscle pain increased the C3/C4 anti-directional motion (P < 0.01), decreased the C6/C7 anti-directional motion (P < 0.05) during extension, and redistributed total joint motion between joints and between half ranges during flexion (P < 0.05). 2) Trapezius muscle pain decreased pro-directional motion (P < 0.05), anti-directional motion (P < 0.05), and joint motion variability (P < 0.05) during extension. 3) Trapezius and multifidus muscle pain increased the PPTs bilaterally over C2/C3 and on the left side of C5/C6 facet joints (P < 0.05).InterpretationThe direction of motion influenced the effects of experimental muscle pain on dynamic cervical joint kinematics, and deep muscle pain showed local effects on individual joints while superficial muscle pain showed global effects spread to all joints.     

Nociceptive flexion reflexes during analgesic neurostimulation in man

Nociceptive flexion reflexes of the lower limbs (RIII responses) have been studied in 21 patients undergoing either epidural (DCS, n = 16) or transcutaneous (TENS, n = 5) analgesic neurostimulation (AN) for chronic intractable pain. Flexion reflex RIII was depressed or suppressed by AN in 11 patients (52.4%), while no modification was observed in 9 cases and a paradoxical increase during AN was evidenced in 1 case. In all but 2 patients, RIII changes were rapidly reversible after AN interruption. RIII depression was significantly associated with subjective pain relief, as assessed by conventional self-rating; moreover, in 2 patients it was possible to ameliorate the pain-suppressing effects of AN by selecting those stimulation parameters (intensity and frequency) that maximally depressed nociceptive reflex RIII. We recorded 2 cases of RIII attenuation after contralateral neurostimulation. AN appeared to affect nociceptive reflexes rather selectively, with no or very little effect on other cutaneous, non-nociceptive responses. Recording of RIII reflexes is relatively simple to implement as a routine paraclinical procedure. It facilitates the objective assessment of AN efficacy and may help to choose the most appropriate parameters of neurostimulation. In addition, RIII behavior in patients could be relevant to the understanding of some of the mechanisms involved in AN-induced pain relief.     

The relationship beween posture and back muscle endurance in industrial workers with flexion-related low back pain

This preliminary cross-sectional study was undertaken to determine if there were measurable relationships between posture, back muscle endurance and low back pain (LBP) in industrial workers with a reported history of flexion strain injury and flexion pain provocation. Clinical reports state that subjects with flexion pain disorders of the lumbar spine commonly adopt passive flexed postures such as slump sitting and present with associated dysfunction of the spinal postural stabilising musculature. However, to date there is little empirical evidence to support that patients with back pain, posture their spines differently than pain-free subjects. Subjects included 21 healthy industrial workers and 24 industrial workers with flexion-provoked LBP. Lifestyle information, lumbo-pelvic posture in sitting, standing and lifting, and back muscle endurance were measured. LBP subjects had significantly reduced back muscle endurance (P < 0.01). LBP subjects sat with less hip flexion, (P = 0.05), suggesting increased posterior pelvic tilt in sitting. LBP subjects postured their spines significantly closer to their end of range lumbar flexion in 'usual' sitting than the healthy controls (P < 0.05). Correlations between increased time spent sitting, physical inactivity and poorer back muscle endurance were also identified. There were no significant differences found between the groups for the standing and lifting posture measures. These preliminary results support that a relationship may exist between flexed spinal postures, reduced back muscle endurance, physical inactivity and LBP in subjects with a history of flexion injury and pain.     

Ultrasound in treatment of back pain resulting from prolapsed intervertebral disc

The efficacy of ultrasound therapy in the management of back pain resulting from rupture of the intervertebral disc was evaluated in 3 groups: treatment, placebo, and control. Range of motion of total flexion and extension, total side flexion and total rotation of the lumbar spine, and subjective assessment of pain were used as criteria to determine the efficacy of treatment. Group comparisons showed statistical significance in favor of the treatment group (p 0.01), leading to the conclusion that ultrasound therapy is significantly effective in the treatment of back pain resulting from prolapse of the lumbar intervertebral disc.     

The effects of non-painful transcutaneous electrical nerve stimulation on cutaneous pain threshold and muscular reflexes in normal men and in subjects with chronic pain

In healthy subjects and in subjects with chronic myofascial pain of one lower limb, the following was measured in both lower limbs: (i) sequential Hoffman (H) reflex, (ii) sequential Achilles tendon (T) reflex, (iii) cutaneous pain threshold determined with electrical stimuli, before, during and after transcutaneous electrical nerve stimulation (TENS).In healthy subjects no significant differences were observed between the pain thresholds of the two limbs. During and after TENS, changes of the reflexes were related to the pain thresholds.In the pathological subjects a significant difference of pain threshold was present between the affected limb and the contralateral one. An important difference between healthy and pathological subjects is not the quality but the quantity of the changes induced by TENS, in the sense that the levels of inhibition and facilitation of the reflexes are more evident in patients with pain. Indeed, TENS induces a reset of sensory and of motor system and a parallel long lasting effect both on sensory and on muscular function, with concomitant pain relief in the pathological subjects.