The reliability of surface EMG derived motor unit variables

Persistent inward currents in tibialis anterior motoneurons can be reliably estimated within the same session

The response of spinal motoneurons to synaptic input greatly depends on the activation of persistent inward currents (PICs), the contribution of which can be estimated through the paired motor unit technique. Yet, the intra-session test-retest reliability of this measurement remains to be fully established. Twenty males performed isometric triangular dorsiflexion contractions to 20 and 50 % of maximal torque at baseline and after a 15-min resting period. High-density electromyographic signals (HD-EMG) of the tibialis anterior were recorded with a 64-electrode matrix. HD-EMG signals were decomposed, and motor units tracked across time points to estimate the contribution of PICs to motoneuron firing through quantification of motor unit recruitment-derecruitment hysteresis (ΔF). A good intraclass correlation coefficient (ICC = 0.75 [0.63, 0.83]) and a large repeated measures correlation coefficient (rrm = 0.65 [0.49, 0.77]; p < 0.001) were found between ΔF values obtained at both time points for 20 % MVC ramps. For 50 % MVC ramps, a good ICC (0.77 [0.65, 0.85]) and a very large repeated measures correlation coefficient (rrm = 0.73 [0.63, 0.80]; p < 0.001) were observed. Our data suggest that ΔF scores can be reliably investigated in tibialis anterior motor units during both low- and moderate-intensity contractions within a single experimental session.

Effect of physiotherapeutic procedures on the bioelectric activity of the masseter muscle and the range of motion of the temporomandibular joints in the female population with chronic pain: a randomized controlled trial

INTRODUCTION

Physical therapy (PT) methods applied in dentistry are increasingly discussed nowadays. Taking into account a rapidly growing number of temporomandibular disorders (TMDs) and orofacial pain patients, it is reasonable to determine which of the available physiotherapeutic (PT) methods are more effective than others, especially in terms of their possible analgesic and myorelaxant effects.

OBJECTIVE

To assess manual and physical factors influencing pain reduction or elimination and increased muscle tension in patients with TMD; yet the influence of the applied forms of PT on the range of motion (ROM) of temporomandibular joints (TMJ).

MATERIAL AND METHODS

A randomized, parallel-group, RCT, single-blind, equi-randomized (1:1) study was conducted in DC/TMD Group Ib patients (20-45 years of age). An experimental group (G1, n = 104) and a control group without TMD (G2, n = 104) were created according to CONSORT guidelines. Diagnostic measurements were performed in both groups (mass sEMG, temporomandibular joint range of motion-ROM, pain intensity - NRS). Group G1 was randomly divided (envelope method) into 4 therapeutic groups, in which therapy was carried out for 10 days: magnetostimulation (MS), magnetoledotherapy (MLE), magnetolaserotherapy (MLA), manual therapy (MT). Each time after the therapy, ROM and NRS measurements were performed, and after the 5th and 10th day sEMG.

RESULTS

Statistically significant differences were found in the sEMG values of the masseter muscles, TMJ ROM and the pain intensity in G1 and G2 (p < 0.00). The largest decrease in sEMG (% MVC) of the masseter muscle occurred in the subgroup in which the manual therapy (MT) procedures were applied, p < 0.000. There was no clinically significant difference in and between other subgroups. There was a distinct mandible ROM increase noted in the MT group, with minimal changes in the MLA and MLE groups and no changes in the MS group. There was a clear increase in the lateral mobility of both right and left TMJ in the MT group. There were no differences in the course of the study in the MS group, and slight increases in the MLA and MLE groups. In the case of pain measurements, the greatest decrease in pain intensity was observed in the MT subgroup.

CONCLUSIONS

According to our results manual therapy is an effective form of treatment in patients with pain, increased masticatory muscle tension and limitation in mandible ROM. Dental physiotherapy should become an integral part of multimodal TMD patients' treatment.

Surface electromyography evaluation of selected manual and physical therapy interventions in women with temporomandibular joint pain and limited mobility. Randomized controlled trial (RCT)

Non-invasive approach is gaining an increasing recognition in the TMD patients management. It is therefore reasonable to conduct RCTs evaluating the effectiveness of both physical and manual physiotherapy interventions. The aim of this study was to evaluate the short-term efficacy of selected physiotherapeutic interventions and their effect on the bioelectrical function of the masseter muscle in patients with pain and limited TMJ mobility. The study was conducted on a group of 186 women (T) with the Ib disorder diagnosed in DC/TMD. The control group consisted of 104 women without diagnosed TMDs. Diagnostic procedures were performed in both groups. The G1 group was randomly divided into 7 therapeutic groups in which the therapy was carried out for 10 days: magnetostimulation (T1), magnetoledotherapy (T2), magnetolaserotherapy (T3), manual therapy- positional release and therapeutic exercises (T4), manual therapy - massage and therapeutic exercises (T5), manual therapy - PIR and therapeutic exercises (T6), self therapy - therapeutic exercises (T7). In the T4 and T5 groups, the treatments led to complete resolution of pain after the 10th day of therapy and to the largest minimal clinically significant difference in the MMO and LM parameter. GEE model for PC1 values using treatment method and time point showed that T4, T5 and T6 treatments had the strongest effect on the parameters studied. Therefore, it may be concluded that SEMG testing is a helpful indicator to assess the therapeutic effectiveness of physiotherapeutic interventions.

BACKGROUND

Non-invasive approach is gaining an increasing recognition in the TMD patients management. It is therefore reasonable to conduct RCTs evaluating the effectiveness of both physical and manual physiotherapy interventions in a qualitative and quantitative manner. However, there were numerous controversies reported regarding the use of surface electromyography (SEMG) in Orofacial Pain patients. Therefore, we wanted to assess the effectiveness of physiotherapy interventions in TMD patients using SEMG.

PURPOSE

Evaluation of the short-term efficacy of selected physiotherapeutic interventions and their effect on the bioelectrical function of the masseter muscle in patients with pain and limited TMJ mobility.

MATERIAL AND METHODS

The study was conducted on a group of 186 women (T) with the Ib disorder diagnosed in DC/TMD (Ib - myofascial pain with restricted mobility). The control group consisted of 104 women without diagnosed TMDs (normal reference values for TMJ ROM and masseter muscle SEMG bioelectric activity). Diagnostic procedures were performed in both groups (SEMG of the masseter muscles at baseline and during exercise, measurement of TMJ mobility, assessment of pain intensity - NRS scale). The G1 group was randomly divided into 7 therapeutic groups in which the therapy was carried out for 10 days: magnetostimulation (T1), magnetoledotherapy (T2), magnetolaserotherapy (T3), manual therapy- positional release and therapeutic exercises (T4), manual therapy - massage and therapeutic exercises (T5), manual therapy - PIR and therapeutic exercises (T6), self-therapy - therapeutic exercises (T7). Each time after therapy, the intensity of pain and TMJ mobility were assessed. Sealed, opaque envelopes were used for randomization. After 5 and 10 days of therapy, bilateral SEMG signals of the masseter muscles were acquired. PC1 factor analysis was performed. A score of 99% in the PC1 parameter, demonstrates the clinical relevance of electromyography (MVC).

RESULTS

Synergism of physical factors will lead to a higher MID on the NRS scale. Evaluating the MID of the therapeutic interventions used showed a better therapeutic effect of manual interventions over physical and self-therapy. In the T4 and T5 groups, the treatments led to complete resolution of pain after the 10th day of therapy and to the largest minimal clinically significant difference in the MMO and LM parameter. GEE model for PC1 values using treatment method and time point showed that T4, T5 and T6 treatments had the strongest effect on the parameters studied.

CONCLUSIONS

1. Exercise SEMG testing is a helpful indicator to assess the therapeutic effectiveness of physiotherapy interventions. 2. Manual therapy treatments are superior to physical treatments in their relaxation and analgesic efficacy and should therefore be prescribed as a first line non-invasive intervention for TMD pain patients.

Failure to improve task performance after visuomotor training with error reduction feedback for young adults

Visual feedback that reinforces accurate movements may motivate skill acquisition by promoting self-confidence. This study investigated neuromuscular adaptations to visuomotor training with visual feedback with virtual error reduction. Twenty-eight young adults (24.6 ± 1.6 years) were assigned to error reduction (ER) (n = 14) and control (n = 14) groups to train on a bi-rhythmic force task. The ER group received visual feedback and the displayed errors were 50% of the real errors in size. The control group was trained with visual feedback with no reduction in errors. Training-related differences in task accuracy, force behaviors, and motor unit discharge were contrasted between the two groups. The tracking error of the control group progressively declined, whereas the tracking error of the ER group was not evidently reduced in the practice sessions. In the post-test, only the control group exhibited significant task improvements with smaller error size (p = .015) and force enhancement at the target frequencies (p = .001). The motor unit discharge of the control group was training-modulated, as indicated by a reduction of the mean inter-spike interval (p = .018) and smaller low-frequency discharge fluctuations (p = .017) with enhanced firing at the target frequencies of the force task (p = .002). In contrast, the ER group showed no training-related modulation of motor unit behaviors. In conclusion, for young adults, ER feedback does not induce neuromuscular adaptations to the trained visuomotor task, which is conceptually attributable to intrinsic error dead-zones.

How to Work with Electromyography Decomposition in Practical Classes of Exercise Physiology and Biomechanics

Concepts about motor unit recruitment are important learning contents in exercise physiology and biomechanics classes that are usually taught theoretically. In the last few years, great advances have occurred in the decomposition of surface electromyography, allowing the learning of theoretical contents in an experimental way. In this tutorial paper, we have described the decomposition of surface electromyography methodological aspects and examples to teach motor unit recruitment concepts in exercise physiology and biomechanics practical lessons. This work has the aim to facilitate physiology and biomechanics academics to introduce this technique in practical classes.

Neuromotor control associates with muscle weakness observed with McArdle sign of multiple sclerosis

OBJECTIVE

Multiple Sclerosis (MS) is often accompanied by myelopathy, which may be associated with progressive worsening. A specific finding of MS-associated myelopathy is McArdle sign, wherein neck flexion is associated with prominent increased limb weakness relative to that detected with neck extension. In this study, we characterized neuromotor control properties of finger extensors in association with the McArdle sign.

METHODS

A custom-built device was utilized to monitor torque production of the wrist extensors with simultaneous recording of surface electromyography of the extensor digitorum. The electromyography was decomposed and analyzed via both linear and nominal regressions.

RESULTS

Linear regressions demonstrated a strong difference between groups for MS from healthy controls and other myelopathies for motor unit action potential amplitude and average firing rate (p < 0.001). Further, linear regression demonstrated good correlations of neuromotor variables to mechanical torque output (0.24 ≤ R²  ≤ 0.76). Nominal regression distinguished MS from healthy controls with an AUC of 0.87, specificity of 0.97, and sensitivity of 0.64. Nominal regression of MS from other myelopathies demonstrated an AUC of 0.88, specificity of 0.85, and sensitivity of 0.79.

INTERPRETATION

These data demonstrate the neuromotor control factors that largely determine muscle force production change with the observation of McArdle sign; these neuromotor control factors can differentiate MS from both healthy controls and other myelopathy conditions.