Pain-Induced Reduction in Corticomotor Excitability Is Counteracted by Combined Action-Observation and Motor Imagery

Enhancing motor imagery practice using synchronous action observation

In this paper, we discuss a variety of ways in which practising motor actions by means of motor imagery (MI) can be enhanced via synchronous action observation (AO), that is, by AO + MI. We review the available research on the (mostly facilitatory) behavioural effects of AO + MI practice in the early stages of skill acquisition, discuss possible theoretical explanations, and consider several issues related to the choice and presentation schedules of suitable models. We then discuss considerations related to AO + MI practice at advanced skill levels, including expertise effects, practical recommendations such as focussing attention on specific aspects of the observed action, using just-ahead models, and possible effects of the perspective in which the observed action is presented. In section "Coordinative AO + MI", we consider scenarios where the observer imagines performing an action that complements or responds to the observed action, as a promising and yet under-researched application of AO + MI training. In section "The dual action simulation hypothesis of AO + MI", we review the neurocognitive hypothesis that AO + MI practice involves two parallel action simulations, and we consider opportunities for future research based on recent neuroimaging work on parallel motor representations. In section "AO + MI training in motor rehabilitation", we review applications of AO, MI, and AO + MI training in the field of neurorehabilitation. Taken together, this evidence-based, exploratory review opens a variety of avenues for future research and applications of AO + MI practice, highlighting several clear advantages over the approaches of purely AO- or MI-based practice.

Females with painful temporomandibular disorders present higher intracortical facilitation relative to pain-free controls

OBJECTIVES

This study aimed to investigate cortical excitability differences in the primary motor cortex (M1) hand representation between individuals with temporomandibular disorders (TMD) and healthy controls. We assessed resting motor thresholds, motor-evoked potentials (MEPs), intracortical inhibition, and intracortical facilitation and explored potential associations with clinical and psychosocial characteristics in the TMD group.

MATERIALS AND METHODS

We recruited 36 female participants with TMD and 17 pain-free controls. Transcranial magnetic stimulation (TMS) was used to assess M1 cortical excitability. Correlations between clinical and psychosocial factors and cortical excitability measures were also evaluated.

RESULTS

Patients with TMD showed significantly higher intracortical facilitation at 12 ms (z = 1.98, p = 0.048) and 15 ms (z = 2.65, p = 0.008) when compared to controls. Correlations revealed associations between intracortical facilitation and pain interference, sleep quality, depressive symptoms, and pain catastrophizing in the TMD group.

CONCLUSIONS

Females with TMD exhibit heightened motor cortex intracortical facilitation in the hand representation, potentially indicating altered cortical excitability beyond the motor face area. This suggests a role for cortical excitability in TMD pathophysiology, influenced by psychosocial factors.

CLINICAL RELEVANCE

Understanding cortical excitability in TMD may inform targeted interventions. Psychosocial variables may play a role in cortical excitability, emphasizing the multidimensional nature of TMD-related pain. Further research is needed to confirm and expand upon these findings, with potential implications for the management of TMD and related pain conditions.

A single session of action observation therapy versus observing a natural landscape in adults with chronic neck pain - a randomized controlled trial

BACKGROUND

Action observation (AO) has emerged as a potential neurorehabilitation therapy for patients with neck pain (NP), but evidence of its effectiveness is scarce. This study aims to assess the effect of a single session of AO when compared to observing a natural landscape on NP intensity, fear of movement, fear-avoidance beliefs, neck muscles' strength, pressure pain threshold, and tactile acuity.

METHODS

Sixty participants with NP were randomly allocated to the AO group (n = 30) or control group (n = 30). Both groups watched an 11-minute video: the AO group watched a video of a person matched for age and sex performing neck exercises, while the control group watched a video of natural landscapes. Neck pain intensity, fear of movement, fear-avoidance beliefs, tactile acuity, pressure pain thresholds, and neck muscle strength were assessed both at baseline and post-intervention. General linear models of repeated measures (ANCOVA of two factors) were used to explore between-group differences at post-intervention.

RESULTS

There was a significant main effect of time for pain intensity (p = 0.02; η2p = 0.09; within-group mean change and 95% CI: AO=-1.44 (-2.28, -0.59); control=-1.90 (-2.74, -1.06), but no time versus group interaction (p = 0.46). A time versus group significant interaction was found for one out of the six measurement sites of two-point discrimination and the neck flexors strength (p < 0.05) favoring the control group. No other statistically significant differences were found for the remaining variables).

CONCLUSIONS

Results suggest a similar acute benefit for both a single session of AO and observing natural landscapes for promoting hypoalgesia, but no impact on kinesiophobia, fear-avoidance beliefs, or pressure pain thresholds. Also, AO had no positive effect on two-point discrimination and muscle strength. Further research is needed, with longer interventions.

TRIAL REGISTRATION

Clinialtrials.gov (NCT05078489).

Disrupted Cortical Homeostatic Plasticity Due to Prolonged Capsaicin-induced Pain

Homeostatic plasticity (HP) regulates cortical excitability (CE) stability but is disrupted in persistent pain conditions. This study investigated how prolonged experimental pain affects HP and if pain relief modulates disrupted HP. Twenty-four healthy participants were randomised into a PainRelief or NoPainRelief group and attended four sessions; two sessions on consecutive days, separated by two weeks. Transcranial magnetic stimulation motor-evoked potentials reflecting CE and quantitative sensory testing (QST) measures were recorded. A capsaicin (pain condition) or placebo (control condition) patch was applied to the hand. HP was induced by cathodal-cathodal transcranial direct current stimulation (HP1) with CE assessment before and after. The PainRelief group had ice applied to the patch, while the NoPainRelief group waited for five minutes; subsequently another HP induction (HP2) and CE assessment were performed. After 24 h with the patch on, HP induction (HP3), QST, and CE recordings were repeated. Capsaicin reduced CE and the pain condition showed disrupted homeostatic responses at all time points (HP1: showed CE inhibition instead of facilitation; HP2 & HP3: lack of CE facilitation). Conversely, homeostatic responses were induced at all time points for the placebo condition. Capsaicin pain disrupts HP which is not restored by ice-induced pain relief. Future research may explore the prevention of HP disruption by targeting capsaicin-induced nociception but not pain perception.

Motor Imagery and Pain Processing in Patients With Entrapment Neuropathies: A Cross-sectional Study

OBJECTIVES

(1) To assess the ability to generate both kinesthetic and visual motor imagery in participants with carpal tunnel syndrome (CTS), compared with asymptomatic participants. (2) To assess the influence of psychophysiological and functional variables in the motor imagery process.

METHODS

Twenty patients with unilateral CTS and 18 pain-free individuals were recruited. An observational case-control study with a nonprobability sample was conducted to assess visual and kinesthetic movement imagery ability and psychophysiological variables in patients with CTS compared with asymptomatic participants in a control group. The trial was conducted in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology statement.

RESULTS

CTS patients have more difficulties in generating visual motor images compared with asymptomatic individuals ( t =-2.099; P <0.05; d=0.70). They need more time to complete the mental tasks (visual t =-2.424; P <0.05 and kinesthetic t =-2.200; P <0.05). A negative correlation was found between the ability to imagine and functional deficits ( r =-0.569; P =0.021) for the kinesthetic subscale and temporal summation ( r =-0.515; P <0.5). A positive correlation was found between pain pressure threshold homolateral (homolateral) and time to generate the visual mental images ( r =0.537; P <0.05).

DISCUSSION

CTS patients have greater difficulty generating motor images than asymptomatic individuals. Patients also spend more time during mental tasks. CTS patients present a relationship between temporal summation and the capacity to generate kinesthetic images. In addition, the CST patients presented a correlation between chronometry mental tasking and mechanical hyperalgesia.

Effect of Motor Imagery on Corticomotor Excitability and Pain Status in Rheumatoid Arthritis Patients

OBJECTIVES

Rheumatoid arthritis (RA) has been defined by the American College of Rheumatology in 1987 as a chronic inflammatory disease characterised by joint swelling, joint tenderness, and destruction of synovial joints leading to severe disability and premature mortality. There is a paucity of literature assessing corticomotor excitability in RA patients. This study aimed to assess the effect of motor imagery on corticomotor excitability and pain status in RA patients. The specific objectives were to study the effect of motor imagery on corticomotor excitability and pain status in RA patients. We also wanted to compare the corticomotor excitability between RA patients with healthy controls. The correlation between the measures of corticomotor excitability and pain status in RA patients has also been done.

METHODS

The study was designed as a pilot clinical trial with a case-control design. Forty participants were recruited for the study. Twenty RA patients were recruited from the Department of Rheumatology and Department of Physical Medicine and Rehabilitation (PMR), AIIMS, New Delhi, and 20 healthy controls. Testing was performed at the Pain Research & rTMS Lab, Department of Physiology, AIIMS, New Delhi. The study was approved by the Institute Ethics Committee, AIIMS New Delhi, and registered in the Clinical Trials Registry-India (CTRI). For the subjective assessment of pain, the visual analogue scale (VAS), Short-Form McGill Pain Questionnaire, WHO-Quality of Life Brief questionnaire (WHO-QOL-BREF), and Rheumatoid Arthritis Pain Scale were used. For the objective assessment of pain, hot and cold pain thresholds were assessed using thermo-tactile quantitative sensory testing (QST) using the method of limits and corticomotor excitability using a transcranial magnetic stimulation device. All participants were also asked to perform motor imagery tasks which consisted of a metronome-paced thumb opposition paradigm.  Results: The resting motor threshold (RMT) decreased significantly after motor imagery when compared to the mental calculation group. The amplitude of motor evoked potential (MEP) and QST parameter value was comparable in both the groups before and after motor imagery and mental calculation. RMT was found to be significantly higher whereas MEP values were found to be significantly lower in RA compared to controls.

CONCLUSION

We conclude that patients suffering from RA have decreased corticomotor excitability compared to controls. Motor imagery was effective in improving corticomotor excitability in these patients and can be used as rehabilitation in RA to relieve their pain.

Effects of mental practice on pain, functionality, and quality of life in individuals with chronic neck pain: A systematic review

PURPOSE

There are conflicting reports in the literature regarding the effectiveness of motor imagery (MI) and action observation (AO) in individuals with chronic non-specific neck pain (CNSNP). This study sought to systematically investigate whether mental practice has any impact on pain, functionality and quality-of-life in individuals with CNSNP.

METHODS

This is a systematic review. Randomized controlled trials (RCTs) that explored the effects of mental practice on pain, functionality and quality-of-life in individuals with CNSNP were searched using databases PubMed, Cochrane library, Medline via Ovid, Scopus, and PEDro from inception to July 2022. Two reviewers independently extracted data and evaluated the quality of the studies utilizing the PEDro scale.

RESULTS

Six high-quality RCTs with 128 participants with CNSNP in the MI and AO groups, and 93 participants with CNSNP in the control group, were included in this review. Both AO and MI were effective in improving pain response and cervical joint position sense. However, AO was more efficient than MI and its effects were retained longer. Improvements in the visual analogue scale and neck disability index were retained when MI training lasted for 6 weeks. The pain and general health sub-parameters of the short form-36 health survey improved after MI training.

CONCLUSION

Mental practice, particularly AO, can improve neck pain intensity, joint position sense, functional disability, and some aspects of quality-of-life in individuals with CNSNP. These improvements dissipated over time. Although mental practice can be an alternative to exercise when pain exists, it can be more efficient when prescribed with simple movements and exercises.

REGISTRATION

The protocol of this review was registered with PROSPERO (CRD42022330240) Available from: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022330240.

The Effect of Acute and Sustained Pain on Corticomotor Excitability: A Systematic Review and Meta-Analysis of Group and Individual Level Data

Pain alters motor function. This is supported by studies showing reduced corticomotor excitability in response to experimental pain lasting &lt;90 minutes. Whether similar reductions in corticomotor excitability are present with pain of longer durations or whether alterations in corticomotor excitability are associated with pain severity is unknown. Here we evaluated the evidence for altered corticomotor excitability in response to experimental pain of differing durations in healthy individuals. Databases were systematically searched for eligible studies. Measures of corticomotor excitability and pain were extracted. Meta-analyses were performed to examine: (1) group-level effect of pain on corticomotor excitability, and (2) individual-level associations between corticomotor excitability and pain severity. 49 studies were included. Corticomotor excitability was reduced when pain lasted milliseconds-seconds (hedges g's = -1.26 to -1.55) and minutes-hours (g's = -0.55 to -0.9). When pain lasted minutes-hours, a greater reduction in corticomotor excitability was associated with lower pain severity (g = -0.24). For pain lasting days-weeks, there were no group level effects (g = -0.18 to 0.27). However, a greater reduction in corticomotor excitability was associated with higher pain severity (g = 0.229). In otherwise healthy individuals, suppression of corticomotor excitability may be a beneficial short-term strategy with long-term consequences. PERSPECTIVE: This systematic review synthesised the evidence for altered corticomotor excitability in response to experimentally induced pain. Reduced corticomotor excitability was associated with lower acute pain severity but higher sustained pain severity, suggesting suppression of corticomotor excitability may be a beneficial short-term adaptation with long-term consequences.

The efficacy of graded motor imagery in post-traumatic stiffness of elbow: a randomized controlled trial

BACKGROUND

Physiotherapy improves the movement range after the onset of post-traumatic elbow stiffness and reduces the pain, which is a factor limiting elbow range of motion. However, no results have been reported for motor-cognitive intervention programs in post-traumatic elbow stiffness management. The objective was to investigate the efficacy of graded motor imagery (GMI) in post-traumatic elbow stiffness.

METHODS

Fifty patients with post-traumatic elbow stiffness (18 female; mean age, 41.9 ± 10.9 years) were divided into 2 groups. The GMI group (n = 25) received a program consisting of left-right discrimination, motor imagery, and mirror therapy (twice a week for 6 weeks); the structured exercise (SE) group (n = 25) received a program consisting of range-of-motion, stretching, and strengthening exercises (twice a week for 6 weeks). Both groups received a 6-week home exercise program. The primary outcome was the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire. The secondary outcomes were the active range of motion (AROM), visual analog scale (VAS), Tampa Scale for Kinesiophobia (TSK), muscle strength of elbow flexors and extensors, grip strength, left-right discrimination, and Global Rating of Change. Patients were assessed at baseline, at the end of treatment (12 sessions), and a 6-week follow-up.

RESULTS

The results indicated that both GMI and SE interventions significantly improved outcomes (P < .05). After a 6-week intervention, the DASH score was significantly improved with a medium effect size in the GMI group compared with the SE group, and improvement continued at the 6-week follow-up (F_1,45 = 3.10, P = .01). The results with a medium to large effect size were also significant for elbow flexion AROM (P = .02), elbow extension AROM (P = .03), VAS-activity (P = .001), TSK (P = .01), and muscle strength of elbow flexors and elbow extensors (P = .03) in favor of the GMI group.

CONCLUSION

The GMI is an effective motor-cognitive intervention program that might be applied to the rehabilitation of post-traumatic elbow stiffness to improve function, elbow AROM, pain, fear of movement-related pain, and muscle strength.

Effects of Self-Efficacy and Outcome Expectations on Motor Imagery-Induced Thermal and Mechanical Hypoalgesia: A Single-Blind Randomised Controlled Trial

The main aim of this study was to assess whether self-efficacy (SE) and outcome expectations (OEs) modulate the hypoalgesic effect induced by motor imagery (MI). A total of 75 asymptomatic participants were randomly assigned to the positive (SE+, OE+), negative (SE-, OE-) or non-expectation (CG) groups. Heat pain threshold (HPT) and pain pressure threshold (PPT) were the main variables. Cold detection threshold (CDT), warm detection threshold (WDT), heart rate (HR) and perceived fatigue were the secondary variables. The variables were assessed preintervention, immediately postintervention and 10 min postintervention, except for HR, which was measured continuously during the intervention. Regarding HPT, significant within-group pre-post differences were found in the OE+ group, with a low effect size (p = 0.01, d = -0.39). With regard to ΔPPT, significant intergroup differences were found in Δpost-pre between the SE+ and CG groups (p = 0.012, d = 1.04) and also between SE+ and OE- (p = 0.006, d = 1.08), both with a large effect size. CG, SE-, and OE- groups had poorer CDT and WDT. Regarding HR, significant intergroup differences were found in the postintervention measurement between OE+ and SE-, with a large effect size (p = 0.016, d = 1.34). Lastly, no between-group differences were found regarding perceived fatigue (p > 0.05). The results obtained showed that positive expectations have a slight influence on the increase in heat and mechanical pain detection thresholds. Positive and non-expectancy groups showed an autonomic activation. The results also showed that negative expectations led to poorer perceptual processes.

Sensorimotor Integration and Pain Perception: Mechanisms Integrating Nociceptive Processing. A Systematic Review and ALE-Meta Analysis

Pain treatment services and clinical indicators of pain chronicity focus on afferent nociceptive projections and psychological markers of pain perception with little focus on motor processes. Research supports a strong role for the motor system both in terms of pain related disability and in descending pain modulation. However, there is little understanding of the neurological regions implicated in pain-motor interactions and how the motor and sensory systems interact under conditions of pain. We performed an ALE meta-analysis on two clinical cohorts with atypical sensory and motor processes under conditions of pain and no pain. Persons with sensory altered processing (SAP) and no pain presented with greater activity in the precentral and supplementary motor area relative to persons with self-reported pain. In persons with motor altered processing (MAP), there appeared to be a suppression of activity in key pain regions such as the insula, thalamus, and postcentral gyrus. As such, activation within the motor system may play a critical role in dampening pain symptoms in persons with SAP, and in suppressing activity in key pain regions of the brain in persons with MAP. Future research endeavors should focus on understanding how sensory and motor processes interact both to understand disability and discover new treatment avenues.

Motor Imagery: How to Assess, Improve Its Performance, and Apply It for Psychosis Diagnostics

With this review, we summarize the state-of-the-art of scientific studies in the field of motor imagery (MI) and motor execution (ME). We composed the brain map and description that correlate different brain areas with the type of movements it is responsible for. That gives a more complete and systematic picture of human brain functionality in the case of ME and MI. We systematized the most popular methods for assessing the quality of MI performance and discussed their advantages and disadvantages. We also reviewed the main directions for the use of transcranial magnetic stimulation (TMS) in MI research and considered the principal effects of TMS on MI performance. In addition, we discuss the main applications of MI, emphasizing its use in the diagnostics of various neurodegenerative disorders and psychoses. Finally, we discuss the research gap and possible improvements for further research in the field.

Movement observation activates motor cortex in fibromyalgia patients: a fNIRS study

Scientific evidence points to a shared neural representation between performing and observing an action. The action observation notoriously determines a modulation of the observer’s sensorimotor system, a phenomenon called Motor Resonance (MR). Fibromyalgia (FM) patients suffer from a condition characterized by generalized musculoskeletal pain in which even simple movement can exacerbate their symptoms. Maladaptive functioning of the primary motor cortex is a common finding in patients with chronic pain. Activation of the motor cortex is known to induce an analgesic effect in patients with chronic pain. In this exploratory study, we intend to verify if the mere observation of a movement could elicit activation of the motor cortical areas in patients with FM. Therefore, the purpose of this study was to examine the presence of MR in patients affected by fibromyalgia. We adopted a behavioral paradigm known for detecting the presence of MR and a neurophysiological experiment. Participants watched videos showing gripping movements towards a graspable or an ungraspable object, respectively, and were asked to press a button the instant the agent touched the object (Time-to-contact detection session). In a different experimental session, participants were only requested to observe and pay attention to the videos (Observation-only session). During each experimental session, the participants’ cerebral hemodynamic activity was recorded using the functional Near-Infrared Spectroscopy method. The behavioral task analysis revealed the presence of MR in both FM patients and healthy controls. Moreover, neurophysiological findings suggested that the observation of movement during the Observation-only session provoked activation and modulation of the cortical motor networks of FM patients. These results could represent evidence of the possible beneficial effects of movement observation in restarting motor activation, notoriously reduced, in FM patients.

Hypoalgesic effects of a blood flow restriction technique at moderate intensity with or without motor imagery: a single-blind randomized controlled trial

PURPOSE

The main objective was to assess the hypoalgesic effect of adding blood flow restriction (BFR) training with or without motor imagery (MI) to moderate-intensity exercise. The secondary objective was to analyse the correlations of the pain pressure thresholds (PPTs) regarding perceived pain intensity, perceived fatigue, and cuff pressure discomfort.

METHODS

A sample of 42 asymptomatic participants were randomly assigned to 3 groups: control group (CG), BFR group, and BFR with MI group. All participants performed a squat exercise at an intensity of 60% of 1RM. For the BFR groups, blood occlusion occurred at 80% of maximal arterial occlusive pressure. Local, bilateral, and distal PPT were assessed pre-intervention, post-intervention and 48 h post-intervention. The perceived fatigue was assessed post-intervention, and pain intensity was assessed only 48 h post-intervention.

RESULTS

There were intragroup differences in the CG and BFR + MI group in the local PPT between the pre-intervention and post-intervention measurements (p = 0.039, d= -0.32 and p = 0.009, d= -0.46, respectively) and only in the CG in the bilateral PPT (p = 0.002, d= -0.41). The CG and BFR group showed significant differences at 48 h post-intervention, with a decrease in local PPT (p = 0.009, d = 0.51 and p = 0.049, d = 0.43, respectively) and bilateral PPT (p = 0.004, d = 0.53 and p = 0.021, d = 0.46, respectively). There was a negative moderate correlation between local PPT at the post-intervention time and perceived discomfort of the occlusion device only in the BFR group (r=-0.54, p = 0.045).

CONCLUSION

Moderate-intensity resistance training with high occlusion did not generate hypoalgesia but did appear to generate a hyperalgesic response within 48 h after the intervention.

Pain relief by movement representation strategies: An umbrella and mapping review with meta-meta-analysis of motor imagery, action observation and mirror therapy

OBJECTIVE

To develop a mapping and umbrella review with a meta-meta-analysis (MMA) to critically evaluate the current evidence of motor imagery (MI), action observation and mirror therapy (MT) on pain intensity.

METHODS

The study involved a systematic search of PubMed, PEDro, Scielo, EBSCO and Google Scholar.

RESULTS

Ten systematic reviews were included in the qualitative synthesis, 70% of which showed high methodological quality. Three reviews found a significant reduction in chronic musculoskeletal pain as the result of applying movement representation methods (MRM) plus usual-care (UC), with a large clinical effect (standardized mean difference [SMD] of -1.47; 95% CI -2.05 to -0.88; heterogeneity Q = 1.66; p = 0.44; I²  = 0%). However, two reviews showed no statistically significant reduction in acute and postsurgical pain as a result of applying MI plus UC. Four reviews showed no significant reduction in phantom limb pain (PLP) as a result of applying MT plus UC interventions. In four reviews, the MMA showed a significant reduction in complex regional pain syndrome (CRPS) as a result of applying MT plus UC, with a large clinical effect (SMD -1.27; 95% CI -1.87 to -0.67; heterogeneity Q = 3.95; p = 0.27; I²  = 24%). In two reviews, the MMA showed no significant differences in poststroke pain as a result of applying MT plus UC.

CONCLUSION

Results show that MRM could be effective for chronic musculoskeletal pain, with low to moderate-quality evidence. The results also show a reduction in pain intensity through MT interventions in patients with CRPS, although these results were not found in patients with PLP or poststroke pain.

SIGNIFICANCE

This umbrella review analysed systematic reviews evaluating movement representation techniques, with the aim of synthesizing the available evidence regarding motor imagery, action observation and mirror therapy on pain. The results provide relevant information about the potential clinical use of movement representation techniques in different types of patients with painful conditions.

Effects of neural mobilizations through movement representation techniques for the improvement of neural mechanosensitivity of the median nerve region: a randomized controlled trial

PURPOSE

The main objective was to compare the effects of neural mobilization (NM), NM performed through mirror therapy (MT), NM performed through action observation (AO) training and finally classic rehabilitation program (mobility and strength) exercises on neural mechanosensitivity, widespread of proximal and distal pain and pressure pain thresholds (PPT). The second objective was to assess the effects of these interventions on handgrip strength, conditioned pain modulation, motor imagery ability and temporal summation.

MATERIALS AND METHODS

Single-blinded randomized controlled trial. Fifty-four healthy subjects were randomly assigned to each group. Neural mechanosensitivity, widespread pain and PPT were the main variables. The secondary variables included handgrip strength, conditioned pain modulation, motor imagery ability and temporal summation.

RESULTS

All groups showed significant differences in time*factor for neural mechanosensitivity (p = 0.001), PPT in the dermatome of the median nerve (p = 0.007), PPT at carpal tunnel (p < 0.05) and proximal widespread (p = 0.01). No differences were found for distal widespread, conditioned pain modulation, handgrip strength motor imagery ability or temporal summation (p > 0.05). There is an absence of statistically significant differences between groups.

CONCLUSIONS

NM through movement representation techniques can reduce mechanosensitivity and mechanical hyperalgesia in the median nerve dermatome and forearm, although no differences were found between groups.

Pain, No Gain: Acute Pain Interrupts Motor Imagery Processes and Affects Mental Training-Induced Plasticity

Pain influences both motor behavior and neuroplastic adaptations induced by physical training. Motor imagery (MI) is a promising method to recover motor functions, for instance in clinical populations with limited endurance or concomitant pain. However, the influence of pain on the MI processes is not well established. This study investigated whether acute experimental pain could modulate corticospinal excitability assessed at rest and during MI (Exp. 1) and limit the use-dependent plasticity induced by MI practice (Exp. 2). Participants imagined thumb movements without pain or with painful electrical stimulations applied either on digit V or over the knee. We used transcranial magnetic stimulation to measure corticospinal excitability at rest and during MI (Exp. 1) and to evoke involuntary thumb movements before and after MI practice (Exp. 2). Regardless of its location, pain prevented the increase of corticospinal excitability that is classically observed during MI. In addition, pain blocked use-dependent plasticity following MI practice, as testified by a lack of significant posttraining deviations. These findings suggest that pain interferes with MI processes, preventing the corticospinal excitability facilitation needed to induce use-dependent plasticity. Pain should be carefully considered for rehabilitation programs using MI to restore motor function.

Effects of additional action observation to an exercise program in patients with chronic pain due to knee osteoarthritis: A randomized-controlled trial

BACKGROUND

Knee osteoarthritis (OA) leads to pain, stiffness, and functional impairment and eventually decreased level of the quality of life. Although several treatment methods have been used to achieve pain relief, patients still complain of pain.

OBJECTIVE

The aim of this study was to investigate the effects of the addition of action observation therapy to an exercise program on pain severity, pressure pain threshold, kinesiphobia functionality, and pain catastrophization in knee OA patients with chronic pain.

METHODS

This prospective, randomized-controlled, superiority trial included a total of 36 patients with knee OA. The patients were randomly divided into two groups as the treatment group (n = 18) receiving action observation therapy in addition to exercise and control group (n = 18) receiving exercise alone. The interventions were performed three times weekly for six weeks. The primary outcomes were pain and pressure pain threshold. Secondary outcomes were kinesiphobia, functionality, and pain catastrophization. All participants were assessed at baseline (pre-intervention) and after the six-week treatment (post-intervention).

RESULTS

There was no significant difference in the primary and secondary outcome measures before and after the intervention between the groups (p > 0.05). Both groups showed a significant improvement in all outcome measures after the intervention (p < 0.01).

CONCLUSION

Our study results suggest that action observation therapy in addition to an exercise program does not contribute any additional benefits to pain, pressure pain threshold, kinesiophobia, pain catastrophization, and functionality in knee OA patients with chronic pain. Nonetheless, further large-scale, long-term, prospective studies are needed to gain a better understanding on this subject.

Promising Effect of Visually-Assisted Motor Imagery Against Arthrogenic Muscle Inhibition - A Human Experimental Pain Study

Purpose

Clinically, arthrogenic muscle inhibition (AMI) has a negative impact on functional recovery in musculoskeletal disorders. One possible technique to relieve AMI is motor imagery, which is widely used in neurological rehabilitation to enhance motor neuron excitability. The purpose of this study was to verify the efficacy of visually-assisted motor imagery against AMI using a human experimental pain model.

Methods

Ten healthy volunteers were included. Experimental ankle pain was induced by hypertonic saline infusion into unilateral Kager’s fat pad. Isotonic saline was used as control. Subjects were instructed to imagine while watching a movie in which repetitive motion of their own ankle or fingers was shown. H-reflex normalized by the motor response (H/M ratio) on soleus muscle, maximal voluntary contraction (MVC) force of ankle flexion, and contractile activities of the calf muscles during MVC were recorded at baseline, pre-intervention, post-intervention, and 10 minutes after the pain had subsided.

Results

Hypertonic saline produced continuous and constant peri-ankle pain (VAS peak [median]= 6.7 [2.1–8.4] cm) compared to isotonic saline (0 [0–0.8] cm). In response to pain, there were significant decreases in the H/M ratio, MVC and contractile activities (P<0.01), all of which were successfully reversed after the ankle motion imagery. In contrast, no significant changes were observed with the finger motion imagery.

Conclusion

Visually-assisted motor imagery improved the pain-induced AMI. Motor imagery of the painful joint itself would efficiently work for relieving AMI. This investigation possibly shows the potential of a novel and versatile approach against AMI for patients with musculoskeletal pain.

Effect of adding motor imagery training to neck stabilization exercises on pain, disability and kinesiophobia in patients with chronic neck pain

PURPOSE

The investigation of this study was to compare the effect of adding motor imagery training to neck stabilization exercises on pain, disability, and kinesiophobia in patients with chronic neck pain.

MATERIAL AND METHODS

After screening, seventy-two volunteers with chronic neck pain were randomly allocated to 3 groups: neck stabilization exercises alone, n = 24, combined ( neck stabilization exercises + motor imagery training), n = 24, and a control group, n = 24. Pain intensity, disability, and kinesiophobia before and after the intervention exercises were measured by the Visual Analog Scale, Neck Disability Index, and the Tampa Scale of Kinesiophobia , respectively.

RESULTS

Statistically significant differences in pain intensity, the neck disability index, and kinesiophobia were found when a combined intervention group including neck stabilization and motor imagery training was compared with neck stabilization training alone at 6 weeks ) p ≤ 0.005). Also, there were significant between-group differences favoring experimental groups versus control for all outcomes (p ≤ 0.001).

CONCLUSION

neck stabilization exercises in combination with motor imagery training was superior to neck stabilization exercises alone in decreasing pain, disability, and kinesiophobia in patients with chronic neck pain.

The brain and behavioral correlates of motor-related analgesia (MRA)

The human motor system has the capacity to act as an internal form of analgesia. Since the discovery of the potential influence of motor systems on analgesia in rodent models, clinical applications of targeting the motor system for analgesia have been implemented. However, a neurobiological basis for motor activation's effects on analgesia is not well defined. Motor-related analgesia (MRA) is a phenomenon wherein a decrease in pain symptoms can be achieved through either indirect or direct activation of the motor axis. To date, research has focused on (a) evaluating the pain-motor interaction as one focused on the acute protection from painful stimuli; (b) motor cortex stimulation for chronic pain; or (c) exercise as a method of improving chronic pain in animal and human models. This review evaluates (1) current knowledge surrounding how pain interferes with canonical neurological performance throughout the motor axis; and (2) the physiological basis for motor-related analgesia as a means to reduce pain symptom loads for patients. A proposal for future research directions is provided.

Hypoalgesic Effects of Aerobic and Isometric Motor Imagery and Action Observation Exercises on Asymptomatic Participants: A Randomized Controlled Pilot Trial

OBJECTIVES

The objective was to explore whether action observation (AO) and motor imagery (MI) of aerobic and isometric exercise could induce hypoalgesic responses in asymptomatic individuals compared with placebo observation (PO).

METHODS

A randomized controlled pilot trial was designed. Twenty-four healthy participants (mean age = 21.9 ± 2.1 years) were randomized into three groups: AO+MI (N = 8), AO, (N = 8), and PO (N = 8). All participants performed an actual aerobic running exercise (three series of 90 seconds at 85% of their VO2max and 30 seconds at 65% of their VO2max) and an isometric exercise protocol (isometric squats). A day later, they all performed the mental intervention, observing or imagining exercise execution performed the day before, according to their allocated group. Pressure pain thresholds (PPTs) of the quadriceps and epicondyle regions were assessed at baseline, postintervention, and 15 minutes postintervention.

RESULTS

Analysis of variance revealed statistically significant differences in the group*time interaction for PPT in the quadriceps. The AO group showed a statistically significant increase at postintervention and at 15 minutes postintervention. The AO+MI group obtained a statistically significant increase in the two PPT regions compared with the PO group at Δpre-post. The AO group obtained a greater increase in the PPT in the quadriceps femoris than the PO group at Δpre-post and Δpre-post 15 minutes.

CONCLUSIONS

AO and MI induce hypoalgesic responses compared with PO. AO isolated training showed pain modulation responses in the PPTs of the quadriceps region in young physically active adults. These findings highlight the potential role of brain training in pain management.

Impact of Experimental Tonic Pain on Corrective Motor Responses to Mechanical Perturbations

Movement is altered by pain, but the underlying mechanisms remain unclear. Assessing corrective muscle responses following mechanical perturbations can help clarify these underlying mechanisms, as these responses involve spinal (short-latency response, 20-50 ms), transcortical (long-latency response, 50-100 ms), and cortical (early voluntary response, 100-150 ms) mechanisms. Pairing mechanical (proprioceptive) perturbations with different conditions of visual feedback can also offer insight into how pain impacts on sensorimotor integration. The general aim of this study was to examine the impact of experimental tonic pain on corrective muscle responses evoked by mechanical and/or visual perturbations in healthy adults. Two sessions (Pain (induced with capsaicin) and No pain) were performed using a robotic exoskeleton combined with a 2D virtual environment. Participants were instructed to maintain their index in a target despite the application of perturbations under four conditions of sensory feedback: (1) proprioceptive only, (2) visuoproprioceptive congruent, (3) visuoproprioceptive incongruent, and (4) visual only. Perturbations were induced in either flexion or extension, with an amplitude of 2 or 3 Nm. Surface electromyography was recorded from Biceps and Triceps muscles. Results demonstrated no significant effect of the type of sensory feedback on corrective muscle responses, no matter whether pain was present or not. When looking at the effect of pain on corrective responses across muscles, a significant interaction was found, but for the early voluntary responses only. These results suggest that the effect of cutaneous tonic pain on motor control arises mainly at the cortical (rather than spinal) level and that proprioception dominates vision for responses to perturbations, even in the presence of pain. The observation of a muscle-specific modulation using a cutaneous pain model highlights the fact that the impacts of pain on the motor system are not only driven by the need to unload structures from which the nociceptive signal is arising.

Comparative study of observed actions, motor imagery and control therapeutic exercise on the conditioned pain modulation in the cervical spine: a randomized controlled trial

Aim: The aim of this study was to compare the effects of cervical exercise, motor imagery (MI) and action observation (AO) of cervical exercise actions on conditioned pain modulation and pressure pain thresholds. The second objective was to assess the effects of these interventions on cervical motor activity (ranges of motion and muscle endurance), attention, and the ability to generate motor images.Study design: Single-blinded randomized controlled trial.Materials and methods: Fifty-four healthy subjects were randomly assigned to each group. Response conditioned pain modulation, pressure pain threshold, were the main variables. The secondary outcome measures included, cervical range of motion, Neck flexor endurance test, mental movement representation associated and psychosocial variables.Results: All groups showed significant differences in time factor for all evaluated variables (p < .01) except pressure pain threshold over the tibial region. The post hoc analysis revealed significant within-group differences in the AE and AO groups in conditioned pain modulation (p < .05), with medium effect size in time [AE (d -0.61); AO (d -0.74)].Conclusion: The results showed that within-group changes in conditioned pain modulation, cervical muscle endurance, and attention where founded only in the AE and AO groups. Variations in pain thresholds at pressure in the trapezium area were also obtained in the three groups. Changes in the ranges of flexion-extension and rotation movement were presented exclusively in the exercise group, and in the capacity to generate motor images only in the AO group. However, there was no difference in the pressure pain threshold over the tibial region.

Effects of mental and physical orofacial training on pressure pain sensitivity and tongue strength: A single-blind randomized controlled trial

OBJECTIVES

The main objective of this study was to analyze differences on pain pressure thresholds, tongue strength and perceived effort between various orofacial motor exercise training dosages of mental representation training through motor imagery (MI) and action observation (AO), first in isolation and then in combination with real exercise performance.

METHODS

A single-blind randomized controlled trial was designed. 48 asymptomatic individuals were randomized into two groups: Intensive training group (IG) and Moderate training group (MG). Both groups performed a first session of MI and AO of orofacial exercises training and a second session of actual orofacial exercises combined with mental representation training, but with different dosage in terms of series and repetitions. Pain pressure thresholds (PPTs) in the masseter and temporal muscles and tongue muscle strength were the main variables.

RESULTS

Regarding the PPT, ANOVA revealed significant between-group differences, where MG showed a significantly higher PPT than IG at post-day2, with a medium effect size. Both groups showed with-in group differences between pre and post intervention measures in the first session, but only the IG showed differences in the second. Regarding tongue muscle strength, ANOVA revealed significant within-group differences only in MG between the pre-day and post-day first intervention.

CONCLUSION

The results of the present study suggest that movement representation training performed in isolation may have a positive effect on PPTs and tongue muscle strength. In addition, the combination with the actual execution of the exercises could be considered effective, but it is necessary to take into account the training dosage to avoid fatigue responses.

Effect of brain training through visual mirror feedback, action observation and motor imagery on orofacial sensorimotor variables: A single-blind randomized controlled trial

OBJECTIVES

The main objective was to evaluate the effects of action observation (AO), visual mirror feedback (VMF) and motor imagery (MI), combined with an oro-facial exercise programme, on sensorimotor variables in asymptomatic participants.

METHODS

We designed a randomised, single-blind, controlled trial that included 52 asymptomatic participants who were randomly assigned to 4 groups, 13 to each of the VMF, MI and AO groups and 13 to the control group (CG), which only performed the exercise programme. The primary outcomes were pain pressure sensitivity and tongue muscle strength. The secondary outcomes were maximum mouth opening, tongue length and the ability to generate mental motor images. Each group underwent a 3-session intervention using their respective exercise. Measurements were performed before starting the intervention and after each of the 3 sessions (pre, mid1, mid2 and post).

RESULTS

ANOVA revealed significant changes in PPTs in the masseter muscle region in the MI and AO groups in the pre-post and mid1-post changes. ANOVA revealed significant differences in tongue muscle strength in the anterior direction only in the AO group in the pre-mid2 and pre-post changes.

CONCLUSIONS

AO and MI, in conjunction with exercise, could induce changes in PPTs for the masseter muscle. In addition, only AO produced changes in tongue muscle strength. More research is needed to determine the role of brain representation techniques in the oro-facial region and transferring this exercise to the rehabilitation setting.

Motor Imagery and Action Observation of Specific Neck Therapeutic Exercises Induced Hypoalgesia in Patients with Chronic Neck Pain: A Randomized Single-Blind Placebo Trial

The aim of the present study was to explore the pain modulation effects of motor imagery (MI) and action observation (AO) of specific neck therapeutic exercises both locally, in the cervical region, and remotely. A single-blind, placebo clinical trial was designed. A total of 30 patients with chronic neck pain (CNP) were randomly assigned to an AO group, MI group, or placebo observation (PO) group. Pain pressure thresholds (PPTs) of C2/C3, trapezius muscles, and epicondyle were the main outcome variables. Secondary outcomes included heart rate measurement. Statistically significant differences were observed in PPTs of the cervical region in the AO and MI groups between the preintervention and first postintervention assessment. Significant differences were found in the AO group in the epicondyle between the preintervention, first and second post-intervention assessments. Regarding heart rate response, differences were found in the AO and MI groups between the preintervention and average intervention measurements. AO and MI induce immediate pain modulation in the cervical region and AO also induces remote hypoalgesia. OA appears to lead to greater pain modulation as well as a greater heart rate response, however, both should be clinically considered in patients with CNP.