Changes In Electromyographic Activity Research Articles

Changes in Electromyographic Activity of the Dominant Arm Muscles during Forehand Stroke Phases in Wheelchair Tennis.

The aim of this study was to determine the muscle activations of the dominant arm during the forehand stroke of wheelchair tennis. Five players participated in the present study (age: 32.6 ± 9.9 years; body mass: 63.8 ± 3.12 kg; height: 164.4 ± 1.7 cm). The electrical muscle activity of six dominant arm muscles was recorded using an sEMG system. A significant effect of the muscle's activity was observed, and it was shown that the muscle activation was significantly higher in the execution phase compared to the preparation phase in the anterior deltoid and biceps brachii (34.98 ± 10.23% and 29.13 ± 8.27%, p < 0.001); the posterior deltoid, triceps brachii, flexor carpi radialis, and extensor carpi radialis were higher in the follow-through phase than in the execution phase (16.43 ± 11.72%, 16.96 ± 12.19%, 36.23 ± 21.47% and 19.13 ± 12.55%, p < 0.01). In conclusion, it was determined that the muscle activations of the dominant arm muscles demonstrate variances throughout the phases of the forehand stroke. Furthermore, the application of electromyographic analysis to the primary arm muscles has been beneficial in understanding the muscular activity of the shoulder, elbow, and wrist throughout the various phases of the forehand stroke in wheelchair tennis.

Neuromuscular Response during Different Side-Cutting Maneuvers and Its Influence on the Risk of Knee Injuries.

The objective of this study was to investigate the impact of a customized exercise program on electromyographic (EMG) variables during side-cutting maneuvers. Fifty-seven physically active volunteers were recruited and randomized into two groups: a control group (CG) and an experimental group (EG). The CG maintained their regular physical activity, while the EG followed an individualized, integrated exercise regimen that included strength, neuromuscular, proprioceptive, eccentric training, and whole-body vibration (WBV) exercises, lasting for 12 weeks. EMG-Root Means Square (RMS) values for the quadriceps (Q) and hamstrings (H) were measured immediately following initial foot contact at 50, 100, 150, and 200 milliseconds. Changes in EMG activity were evaluated before and after a twelve-week intervention, and the effect size (ES, 90% confidence limit [90%CL]) was calculated. The results showed that the EG participants exhibited enhanced co-contraction as measured by the hamstring/quadriceps ratio (H/Q ratio) during both open and cross-cutting side maneuvers after the twelve-week intervention. Furthermore, the customized, integrated exercise program that combined strength, neuromuscular, proprioceptive, eccentric training, and WBV exercises were could potentially serve as a beneficial neuromuscular and biomechanical strategy for addressing knee injury risk in non-professional, physically active populations at high risk for such injuries.

Electromyographic activity of hip extensor muscles during Nordic hamstring and razor curl exercises on leveled and inclined shanks

BackgroundChanges in electromyographic (EMG) activity of hip extensor muscles and knee flexion angles at peak biceps femoris long head (BFlh) EMG activity by different shank angles during razor curl (RC) exercises are unknown.AimsWe investigated the changes in EMG activity of hip extensor muscles and knee flexion angle at peak BFlh EMG activity with different shank angles during RC and also compared the Nordic hamstring (NH) and RC exercises in the EMG activity of hip extensor muscles.MethodsTwelve male university students randomly performed two repetitions of NH and RC with the lower leg slope angle set at 0° (NH0, RC0) and 40° (NH40, RC40). The EMG activity of hip extensor muscles was measured at the BFlh and related muscles. EMG activity was calculated based on the peak value of the root mean square, normalized as a percentage of the maximum voluntary isometric contraction.ResultsThe BFlh EMG activity of NH0 was higher than that of RC0 (p = 0.002) and RC40 (p = 0.008). The knee flexion angle at peak BFlh EMG activity of NH0 was larger than that of NH40 (p = 0.003) and RC40 (p = 0.002), and RC0 was larger than that of NH40 (p = 0.002) and RC40 (p = 0.002).ConclusionNH40, the BFlh EMG activity equivalent to NH0, might be more effective for preventing recurrence of hamstring injury because the knee flexion angle at peak BFlh EMG activity remains within 30°, combined with a high BFlh EMG activity.

The Effect of Bodyweight Support and Incline Running on Triceps Surae Electromyographic Activity

Body weight support (BWS) and incline running (IR) are commonly used either during rehabilitation or during training separately, with many positive effects on athletes’ performance and rehabilitation. The aim of the present study was to investigate the interaction between bodyweight support and incline running on the electromyographic activity of the triceps surae and compare it to flat running. In eighteen healthy men (age: 20.3 ± 1.2 years, body weight: 70.2 ± 4.8 kg, body height: 179.6 ± 5.4 cm), the changes in electromyographic activity (EMGA) during a 10 min run with BWS (15% or 30% of body weight; in different occasions) and IR at 7%, as well as jumping performance and gait spatiotemporal parameters, were evaluated. A lower Rating of Perceived Exertion and a significant decrease in the size of the Vastus Lateralis (VL) (33.4%), Soleus (SOL) (17%), and Gastrocnemius Lateralis (GL) EMGA (28.5%, p &lt; 0.05) but not in Gastrocnemius Medialis (GM) (10.5%, p &gt; 0.05), was observed during BWS30% at 7% slope compared to flat running. Also, low-frequency fatigue of the quadriceps was induced only after running without BWS on a 7% slope (p = 0.011). No changes were found in jumping performance (p = 0.246) and gait spatiotemporal parameters (p &gt; 0.05) except for flight time (p &lt; 0.006). In conclusion, running with a slope of 7% and 30% of BWS can result in EMG activity comparable to that observed during level running. This method can also be used in prevention and rehabilitation training programs without creating fatigue.

Electromyographic activities of glenohumeral joint muscles during shoulder forward flexion with isometric horizontal abduction loading.

Isometric horizontal abduction loading has been applied to improve imbalanced scapular muscle activities during shoulder exercises; however, the effect on glenohumeral joint muscle activity remains unclear. The purpose of this study was to investigate the changes in electromyographic activity of shoulder muscles during forward flexion with isometric horizontal abduction loading in healthy participants. Thirteen healthy men were recruited for this study. Participants performed shoulder forward flexion with isometric horizontal abduction loading using an elastic band (Flex-band condition) and forward flexion without shoulder loading (Normal-flex condition). Muscle activities were evaluated while maintaining shoulder flexion at 60°, 90°, 120°, and 150° (static task) and during active shoulder flexion from 0° to maximum elevation (dynamic task). Surface electrodes were placed on the deltoid, pectoralis major, infraspinatus, and teres minor muscles to measure the activities of the shoulder muscles during each task. The muscle activities during the static task were compared using a 2-way analysis of variance with repeated measures of the 2 factors, loading condition and flexion position, and a paired t test was used for comparisons between the 2 conditions during the dynamic task (significance level set at P<.05). For the static task, the Flex-band condition significantly increased the deltoid middle and posterior activities by 2-15 times and the infraspinatus and teres minor activities by 2-3 times compared with the Normal-flex condition at all positions. In contrast, the Flex-band condition significantly decreased (by about half) the activities of the deltoid anterior (at 120° and 150°) and pectoralis major (at all positions) compared with the Normal-flex condition. For the dynamic task, the Flex-band condition significantly increased the deltoid middle, deltoid posterior, infraspinatus, and teres minor activities by 2-7 times and decreased the deltoid anterior activity by approximately two-thirds. Applying isometric horizontal abduction loading during shoulder forward flexion may be useful in improving the imbalanced muscle activities of the glenohumeral joint, such as excessive activity of the deltoid anterior and pectoralis major and dysfunction of the deltoid middle, deltoid posterior, and shoulder external rotator muscles. Shoulder forward flexion with horizontal abduction loading could be available for exercise in patients who have massive rotator cuff tears or who have undergone rotator cuff repair and shoulder arthroplasty.

Physiological changes associated with copper sulfate-induced nausea and retching in felines.

Nausea is a common disease symptom, yet there is no consensus regarding its physiological markers. In contrast, the process of vomiting is well documented as sequential muscular contractions of the diaphragm and abdominal muscles and esophageal shortening. Nausea, like other self-reported perceptions, is difficult to distinguish in preclinical models, but based on human experience emesis is usually preceded by nausea. Here we focused on measuring gastrointestinal and cardiorespiratory changes prior to emesis to provide additional insights into markers for nausea. Felines were instrumented to chronically record heart rate, respiration, and electromyographic (EMG) activity from the stomach and duodenum before and after intragastric delivery of saline or copper sulfate (CuSO4, from 83 to 322mg). CuSO4 is a prototypical emetic test agent that triggers vomiting primarily by action on GI vagal afferent fibers when administered intragastrically. CuSO4 infusion elicited a significant increase in heart rate, decrease in respiratory rate, and a disruption of gastric and intestinal EMG activity several minutes prior to emesis. The change in EMG activity was most consistent in the duodenum. Administration of the same volume of saline did not induce these effects. Increasing the dose of CuSO4 did not alter the physiologic changes induced by the treatment. It is postulated that the intestinal EMG activity was related to the retrograde movement of chyme from the intestine to the stomach demonstrated to occur prior to emesis by other investigators. These findings suggest that monitoring of intestinal EMG activity, perhaps in combination with heart rate, may provide the best indicator of the onset of nausea following treatments and in disease conditions, including GI disease, associated with emesis.

Changes in electromyographic activity of latent trigger points after a dry needling intervention: a randomised controlled trial

ObjectiveTo analyse the effects of dry needling (DN) in upper trapezius latent trigger points (LTrPs) on pressure pain threshold (PPT) and surface electromyography (sEMG). DesignRandomized, double-blind, placebo controlled clinical trial. SettingsSports Rehabilitation Laboratory, University of Castilla-La Mancha. ParticipantsForty-six participants (18–35 years old) with LTrP in the upper trapezius were divided into two groups: DN-group and Sham-DN-group. InterventionsIn the DN-group, the needle was inserted 10-times through the skin, and it was manipulated up and down using a "fast in and out" technique. In the Sham-DN-group, non-penetrating needles were used. Main outcome measuresPPT, sEMG at rest, and sEMG in isometric contraction of the LTrP of the upper trapezius muscle were evaluated at baseline, 30 min after treatment, and after 24 h, and 72 h of follow-up. ResultsThe mean change in sEMG at rest between baseline and 30 min was − 0.38 (0.38) %refRMS for the DN group and − 0.05 (0.31) %refRMS for the Sham-DN group (mean difference −0.34, 95% confidence interval (CI) of the difference: − 0.54 to − 0.13), and between baseline and 24 h was − 0.35 (0.35) %refRMS for the DN group and − 0.06 (0.58) %refRMS for the Sham-DN group (mean difference −0.29, 95% CI: −0.57 to −0.01). In addition, the DN-group showed higher values of PPT than the Sham-DN group at 72 h (5.22 (1.23) to 4.65 (1.03) kg/cm2; p < 0.05). ConclusionsA single session of DN intervention was effective in reducing the electromyographic activity, muscle fatigue and pain of the upper trapezius muscle in LTrP. Contribution of paperIn healthy volunteers dry needling is effective:•for reducing electromyography activity in latent trigger points.•for reducing muscle fatigue in latent trigger points.•in increasing pressure pain threshold in latent trigger points.

Dual-Motor Balance Tasks Prompts Slight Lower Limb Neuromuscular Adaptations in Healthy Young Adults

Previous literature has analyzed muscular recruitment patterns in various populations during complex balance conditions that involve a secondary task. This inquiry seeks to determine whether challenging sensory systems in young adults during single and dual-motor tasks can prompt modifications in neuromuscular patterns at the hip and leg musculature. Our study included twenty-nine healthy young adults (3 males and 25 females) with an average age of 24.3+/-2.4. Electromyography (EMG) electrodes were used to collect EMG data, and the variables of interest include the onset of muscle contraction, the decay of muscle contraction, peak muscle activation, and duration of muscle contraction. Five balance activities were conducted while performing a dual-motor task, while sensory input was altered in each condition. No significant changes in EMG activity were observed in the gastrocnemius (GA) and (TA) muscle activity. However, a tendency was observed in the onset and duration values of the gluteal muscles. Recruitment of the TA and GA remained uniform across variables, but gluteus maximus (GMax) and medius (GMed) activity appeared sooner (onset) and lasted longer (duration). Comparability in muscle recruitment during dual-task balance activities indicates healthy young adults can successfully rely on other sensory systems for balance when one or more networks are altered. Increases in GA and TA activity suggested a greater need for ankle strategies during the condition trials, while increased GMax and GMed activity indicated the same for hip strategies. Further research should examine joint kinematic to discern any adaptations during dual-motor tasks in young, healthy adults.

Електроміографічне обгрунтування доцільності застосування міорелаксуючих шин технології EXOCAD при лікуванні дисфункції скронево-нижньощелепних суглобів

The purpose of the study was to study and comparatively analyze the nature and degree of changes in electromyographic activity of the main and auxiliary chewing muscles in patients with temporomandibular joint dysfunction before and after the use of treatment with myorelaxant splints. Materials and methods. Five-year study on the basis of Stomatological Medical Center of Bogomolets National Medical University of patients with temporomandibular joint dysfunction (274 people) was conduscted. The general analysis provided 1024 detailed electromyograms before, after and at the stages of treatment of patients with temporomandibular joint dysfunction. Results and discussion. The results and conclusions of the analysis of the effectiveness of the treatment with the use of myorelaxant splints in the treatment of temporomandibular joint dysfunction indicate an increase in the quality of treatment of this pathology in patients and a reduction in the period of achievement of the result. The results obtained after 12 months indicate that the effectiveness of treatment of patients of control group I (with the lowest intensity of symptoms of temporomandibular joint dysfunction) reached 89.1±1.3%; control group II – up to 78.3±1.3%; control group III – 77.3±1.3%. In general, a study of the state of temporomandibular joint, complex clinical and paraclinic diagnosis, modern orthopedic treatment and prevention of musculoskeletal dysfunction of the temporomandibular joints were carried out. Based on the obtained data, the effectiveness of this algorithm of complex diagnosis, treatment and prevention of musculoskeletal dysfunction of temporomandibular joint was developed, clinically implemented and evaluated. Also, the data obtained as a result of the study by the authors were the basis for finding and correcting new methods and algorithms for diagnosing and treating pathology. The original author's concept of the pathogenesis of muscular-articular dysfunction of temporomandibular joint, used in the study and scientifically substantiated by the authors, united all existing theories of the development of this disease. The multifactorial analysis revealed an increase (p &lt;0.001) of the risk of not achieving the effect of treatment by reducing pain syndrome with an increase in scores on the Bayers scale before treatment, odds ratio = 1.6 (95% of BI 1.4–1.9) for each point of growth score (when standardizing on three other risk factors). An increase (p=0.002) of the risk of not achieving the effect of treatment by reducing pain syndrome with an increase in the asymmetry of the indicator J_MM_A_max, Index Bayers (visual analogue scale) = 1.08 (95% BI 1.03–1.12) for each point exceeding the value of the indicator for the left half above the right (when standardizing on three other risk factors). Also, an increase (p= 0.049) of the risk of not achieving the effect of treatment for a decrease in pain syndrome with an increase in the asymmetry of the J_MM_A_mean indicator, odds ratio = 1.28 (95% of BI 1.00–1.65) for each point exceeding the value of the indicator for the left side above the right side (when standardizing on three other risk factors) was found. Conclusion. Such a thorough approach to the implemented model of diagnosis and treatment of patients with temporomandibular joint dysfunction and a synchronized complex of studies and treatment of this pathology, developed in accordance with it, provided an opportunity to assess qualitative and quantitative changes in the link of the chewing apparatus and the central link of the corresponding functional biosystem that ensure the formation and implementation of the main functions of the temporomandibular joint

Prodromal Physiologic Changes During Copper Sulfate‐Induced Nausea and Vomiting: Potential Use of Intestinal EMG Recordings as a Marker for Nausea

Although emetic responses are present during many disease states, there is no consensus regarding the physiologic changes that signal the onset of nausea. In this study, 10 adult felines (6 males and 4 females) were instrumented to chronically record, during the awake state, the electrocardiogram, diaphragm and abdominal muscle electromyographic (EMG) activity, and EMG activity from the stomach and duodenum before and after the gavage or intragastric infusion of saline or copper sulfate (CuSO4, doses ranging from 83 to 322 mg). Intragastric CuSO4 is a prototypical emetic stimulus that triggers emesis primarily by activating a gastrointestinal vagus nerve‐to‐brain pathway. CuSO4 infusion elicited a significant increase in heart rate, decrease in respiratory rate, and a disruption in gastric (baseline~6 CPM, cycles‐per‐minute) and intestinal (baseline~20 CPM) EMG activity several minutes prior to vomiting (see Fig. 1). The change in EMG activity was most consistent in the intestine. Administration of saline did not induce these physiologic changes. Increasing the dose of CuSO4 did not alter the physiologic changes induced by the treatment. In some animals, a second bout of vomiting occurred following the first episode, when prodromal changes of the intestinal EMG were less pronounced. It is postulated that the intestinal EMG activity was related to a retrograde movement of chyme from the intestine to the stomach. These findings suggest that monitoring of intestinal EMG activity may be the best indicator of the onset of nausea following treatments and in disease conditions associated with emesis.

Justification of the need to use myorelaxing splints in the treatment of tempoal-mandibular joint dysfunction

Electromyographic substantiation of feasibility of application of myorelaxing tires of EXOCAD technology in the treatment of tempoal-mandibular joint (TMJ) dysfunction. Our study allowed us to trace and analyze changes in the chewing muscles of patients that occur during the treatment of TMJ dysfunction and indicate its effectiveness. In patients with TMJ dysfunction, qualitative and quantitative indicators of electromyography closely correlate with the stages of development of pathology and correspond to its clinical manifestations. In this study, for the first time, the relationship between changes in the parameters of the frequency of muscle contractions and the subjective sensation of pain in the area of the specified chewing muscle in patients was analyzed. The purpose of this study is comparative analysis of the nature and degree of changes in electromyographic activity of the main and auxiliary chewing muscles in patients with TMJ dysfunction before and after the use of myorelaxing spleen. TMJ dysfunction five-year study covered 274 patients, which were divided into 3 clinical groups (CG I–III). The general analysis provided 1024 electromyograms before and at the stages of patients’ treatment. The results of the analysis of the effectiveness of the use of myorelaxation tires in the treatment of TMJ dysfunction can improve the quality of treatment of this pathology in patients. The results obtained after 12 months indicate that the effectiveness of treatment of patients with CG I (with the lowest intensity of symptoms of TMJ dysfunction) reached 89.1±1.3%; CG II – up to 78.3±1.3%; CG III – 77.3±1.3%. Keywords: electromyography, dysfuction, temporomate-mandibular joint, chewing muscles, facial muscles, bioelectrical activity.

Evaluation of Electromyographic Activity of Masticatory Muscles in Adults with Posterior Crossbite.

Introduction There is evidence that patients with posterior crossbite (PXB) have neuromuscular changes in the masticatory muscles. However, up to the present time, the relationship among these changes on the electromyographic activity of the masticatory muscles is still unclear. Objective To systematic review the available literature on the electromyographic activity of masticatory muscles in adults with PXB. Methods Between August 22 and September 9, 2020, we searched the following seven electronic databases: PubMed, EMBASE, Web of Science, Cochrane Library, SciELO, LILACS, and Scopus. No restrictions were applied regarding the language and year of publication. This systematic review was registered in the Prospective Register of Systematic Reviews (PROSPERO - CRD42020205057) database and conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. After data selection and extraction, the methodological quality of the selected studies was conducted independently by two reviewers, using two different evaluation tools. Results 6957 records were initially located after the search process. In the end, eight papers were selected. Most studies were classified as having average to low methodological quality and moderate to high risk of bias. Based on the available evidence, adult patients with PXB have electromyographic activity changes in the masticatory muscles when compared with individuals without PXB. Moreover, adult patients with unilateral posterior crossbite (UPXB) have asymmetrical electromyographic activity when the crossbite side is compared with the noncrossbite side. Conclusion Despite the lack of studies with high methodological quality, electromyographic evaluation of masticatory muscles should be considered in the diagnosis and in the orthodontic treatment plan of patients with PXB. Prospective studies with a higher sample size and follow-up time, conducted using a rigorous scientific methodology, are necessary to reach a more reliable conclusion.

The Influence of Motoric Maneuvers on Cervical Vestibular Evoked Myogenic Potentials (cVEMPs).

The cervical vestibular evoked myogenic potential (cVEMP) is a vestibular response that is produced by the saccule in response to intense, often low-frequency, short-duration auditory stimuli, and is typically recorded from a contracted sternocleidomastoid (SCM) muscle. Previous research has shown that the amplitude of the cVEMP is related to the amount of SCM electromyographic (EMG) activity. The aim of this study was to determine the influence of various remote motoric maneuvers on the amplitude of the cVEMP, as well as whether they influence the level of SCM EMG activity. The cVEMP was recorded from the left SCM muscle to left ear stimulation, in response to the SCM condition, as well as three different motoric maneuvers (jaw clench, eye closure, and the Jendrassik maneuver). EMG activity was also varied between 50, 75, and 100% of maximal EMG activity. Data from 14 healthy subjects, with a mean age of 25.57 years (standard deviation = 5.93 years), was included in the present study. Mean latency and amplitude of the cVEMP were compared across the four conditions and varying magnitudes of EMG contraction. SPSS 26 was used to statistically analyze the results. cVEMP latency did not vary across condition. cVEMP amplitude decreased with decreasing EMG magnitude. SCM contraction with jaw clench produced the largest increase in cVEMP amplitude; however, this condition was not significantly different from the SCM condition alone. SCM contraction with the Jendrassik maneuver produced a cVEMP amplitude that was similar and not statistically different from SCM contraction alone, and the addition of the eye closure maneuver to SCM contraction resulted in the lowest cVEMP amplitude, which was found to be statistically different from the standard SCM condition at 100 and 75% EMG activity. The amplitude relationship across the conditions was not found to vary with changes in EMG activity; however, a significant increase in EMG amplitude was found during the 50% muscle contraction condition when subjects performed the Jendrassik maneuver in addition to the standard SCM contraction. The addition of the eye closure maneuver to SCM contraction resulted in a significant decrease in cVEMP amplitude, while the addition of the Jendrassik maneuver resulted in a significant increase in EMG activity at the lowest level of SCM activation (i.e., 50%). Additional research is necessary to determine how motoric maneuvers influence the cVEMP amplitude, and whether the results are also dependent on how SCM contraction is being produced (e.g., while supine vs. sitting).

Longitudinal changes in electromyographic activity of masseter and anterior temporalis muscles before and after alloplastic total joint replacement in patients with temporomandibular ankylosis: a prospective study

The purpose of the study was to evaluate the longitudinal changes in electromyographic (EMG) activity of the masseter and temporalis muscles before and after temporomandibular joint (TMJ) total joint replacement (TJR) in ankylosis patients. A prospective longitudinal study was designed on patients undergoing unilateral or bilateral TMJ-TJR. EMG activity at rest and maximal voluntary contraction (MVC) was recorded for the muscles preoperatively (T0), and at one-week (T1) and six-month (T2) follow up. The study sample was composed of 10 (male: female 2.3:1) patients undergoing TMJ-TJR. The number of unilateral and bilateral cases was three and seven, respectively. In both unilateral and bilateral cases a statistically significant reduction in EMG activity of the masseter and anterior temporalis muscles was observed at T1. At T2, EMG activity of the muscles was found to be approaching the preoperative value. In unilateral cases, when the affected side at T0, T1, and T2 was compared with T0 for the unaffected side, statistically significant differences were seen for the masseter. In the case of the temporalis, similar results were seen except at T2 for the postural rest position. The results indicate that re-attachment of the masseter and temporalis muscles occurs progressively post TMJ-TJR.

Changes of neuroplasticity in cortical motor control of human masseter muscle related to orthodontic treatment.

Orthodontic treatment is a common clinical method of malocclusion. Studies have found that neurons in the sensorimotor cortex of the brain undergo adaptive remodeling in response to changes in oral behavior or occlusion. To explore whether orthodontic treatment could be sufficient to cause neuroplastic changes in the corticomotor excitability of the masseter muscle. Fifteen Angle Class II malocclusion patients who were receiving orthodontic treatment participated in the study. Cortical excitability was assessed by electromyographic activity changes evoked by transcranial magnetic stimulation. Four orthodontic time points were recorded, including baseline, day 1, day 7, and day 30. Motor evoked potentials (MEPs) were recorded in the masseter muscle and the first dorsal interosseous muscle (FDI) serving as a control. The data were analysed by stimulus-response curves and corticomotor mapping. Statistical analyses involved repeated measures analysis of variance, two-way ANOVA, and Tukey's post hoc tests. Motor evoked potentials (MEPs) of the masseter muscle were significantly decreased during orthodontic treatment compared with those of the baseline (p<.001). MEPs of the masseter muscle were dependent on session and stimulus intensity (p<.001), whereas MEPs of FDI were only dependent on stimulus intensity (p=.091). Finally, Tukey's post hoc tests demonstrated that MEPs of the masseter muscle on days 1 and 7, with 70%-90% stimulus intensities, were higher than those of baseline values (p<.001). The present study suggested that orthodontic treatment can lead to neuroplastic changes in the corticomotor control of the masseter muscle, which may add to our understanding of the adaptive response of subjects to changes of oral environment during the orthodontic treatment.

Вплив болю на функцію м’язів-стабілізаторів крижово-клубового суглоба в пацієнтів із дисфункцією цього суглоба

Мета: вивчити вплив сторони локалізації болю на біоелектричну активність (БЕА) м’язів, що забезпечують стабільність крижово­клубового суглоба (ККС) під час утримування вертикальної пози при двохопорному й одноопорному стоянні у хворих із дисфункцією ККС залежно від рентгенометричних параметрів крижів та таза. Матеріали та методи. Було досліджено 50 пацієнтів із дисфункцією ККС. Критеріями включення були: локалізація болі в ділянці posterior spinae iliaca superior, що іррадіює в пах, сідниці та стегно; анамнез болю більше ніж 3 місяці; безуспішність попереднього консервативного лікування; позитивні мінімум 4 із 6 провокаційних тестів. Критерієм виключення була наявність тільки 1 або 2 позитивних провокаційних тестів. Пацієнтам проводили електроміографічне дослідження м’язів, підтримуючих стабільність ККС при двохопорному та одноопорному стоянні (Stork тест). Усі пацієнти були обстежені рентгенологічно. На отриманих рентгенограмах вимірювали: кут нахилу краніальної пластинки крижі; кут нахилу таза; кут ротації крижі; ширину суглобових щілин крижово­клубового суглоба в трьох відділах: вентральному, медіальному та дорсальному. Отримані результати були оброблені статистично. Результати. У результаті кластерного аналізу рентгенометричних параметрів всі пацієнти були розподілені на 4 кластери. У пацієнтів 1­го рентгенометричного кластера при двохопорному стоянні було підвищення біоелектричної активності m. Obliques abdominis externus на стороні, контрлатеральній стороні локалізації болю. У положенні стоячи на одній нозі при локалізації болю на опорній стороні це викликало підвищення БЕА m. Gluteus medius на контрлатеральній стороні. БЕА m. Biceps femoris, m. Rectus femoris підвищувалась на стороні локалізації болю. У пацієнтів 2­го кластера вірогідно змінилась БЕА m. Erector spinae, m. Gluteus medius. Локалізація болю на опорній стороні вірогідно підвищує БЕА цих м’язів на цій стороні. Висновки. БЕА м’язів­стабілізаторів ККС і вертикального положення залежала від сторони локалізації болю в пацієнтів із дисфункцією ККС найбільш сприятливих 1­го та 2­го рентгенометричних кластерів. Локалізація болю вірогідно впливала на показники БЕА m. Obliquus abdominis externus, m.m. Gluteus medius, m. Biceps femoris, m. Rectus femoris у пацієнтів 1­го рентгенометричного кластера и m. Gluteus, m. Erector spinae в пацієнтів 2­го рентгенометричного кластера. У всіх пацієнтів була асиметрична рухомість ККС. БЕА м’язів­стабілізаторів ККС и вертикального положення не залежала від сторони локалізації болю в пацієнтів із дисфункцією ККС найбільш несприятливих 3­го і 4­го рентгенометричних кластерів.

Analysis of electromyographic changes in gastrocnemius muscle on exposure to 24 h of dry supine immersion

Introduction: Under microgravity, changes are observed in both structure and content of the gravity-dependent muscles. This may result in disuse atrophy and muscle weakening. However, changes have not been described in the short term exposure of 24 h. Examination of changes in electromyographic activity of the gastrocnemius muscle, on exposure to 24 h of simulated microgravity using dry supine immersion (DSI), was the desired objective of the study. Material and Methods: Ten healthy volunteers were exposed to 24 h of simulated microgravity using DSI. The force generated by maximal voluntary contraction of isometric plantar flexion of ankle was recorded. Electromyography (EMG) of the gastrocnemius corresponding to more than 80% of maximal voluntary isometric contraction (labeled as submaximal contraction) was recorded pre- and post-exposure to 24 h of DSI. Results: Time domain analysis of the surface EMG of gastrocnemius during submaximal contraction revealed a significant increase in mean integrated EMG (iEMG) amplitude (effect size = 0.73, P = 0.031) following 24 h DSI. Power spectral analysis showed a significant decrease in mean frequency (MNF) (P = 0.043) and median frequency (MDF) (P = 0.024) after 24 h DSI. No significant changes were observed in total power, mean power (MNP), and maximal voluntary contraction. A very strong negative correlation was noted between iEMG, MNF, and MDF for the duration of submaximal voluntary contraction (R = −0.827 and −0.810, P = 0.003 and 0.004, respectively); whereas, a very strong positive correlation was noted between iEMG and MNP (R = 0.911, P = 0.002). Conclusion: The findings of the study point toward muscle weakening seen by an early onset of muscle fatigue in anti-gravity muscles as early as 24 h of exposure to microgravity. The same may be borne in mind even during very short duration human space missions.

Changes in electromyographic activity, mechanical power, and relaxation rates following inspiratory ribcage muscle fatigue

Muscle fatigue is a complex phenomenon enclosing various mechanisms. Despite technological advances, these mechanisms are still not fully understood in vivo. Here, simultaneous measurements of pressure, volume, and ribcage inspiratory muscle activity were performed non-invasively during fatigue (inspiratory threshold valve set at 70% of maximal inspiratory pressure) and recovery to verify if inspiratory ribcage muscle fatigue (1) leads to slowing of contraction and relaxation properties of ribcage muscles and (2) alters median frequency and high-to-low frequency ratio (H/L). During the fatigue protocol, sternocleidomastoid showed the fastest decrease in median frequency and slowest decrease in H/L. Fatigue was also characterized by a reduction in the relative power of the high-frequency and increase of the low-frequency. During recovery, changes in mechanical power were due to changes in shortening velocity with long-lasting reduction in pressure generation, and slowing of relaxation [i.e., tau (τ), half-relaxation time (½RT), and maximum relaxation rate (MRR)] was observed with no significant changes in contractile properties. Recovery of median frequency was faster than H/L, and relaxation rates correlated with shortening velocity and mechanical power of inspiratory ribcage muscles; however, with different time courses. Time constant of the inspiratory ribcage muscles during fatigue and recovery is not uniform (i.e., different inspiratory muscles may have different underlying mechanisms of fatigue), and MRR, ½RT, and τ are not only useful predictors of inspiratory ribcage muscle recovery but may also share common underlying mechanisms with shortening velocity.

Temporal Changes in Electromyographic Activity and Gait Ability during Extended Walking in Individuals Post-Stroke: A Pilot Study.

Abnormal gait, particularly in patients with stroke, causes neuromuscular fatigue. We aimed to clarify temporal changes in gait performance and lower limb muscle activity during extended walking in people with stroke hemiplegia. Twelve adults with stroke and eleven healthy controls performed an extended trial involving 20-min continuous walk at a comfortable speed. The primary outcome was electromyography amplitude during the trial and secondary outcomes were walking performance and the instantaneous mean frequency of electromyography during the trial. Data at 1, 6, 12, and 18 min after initiating walking were compared. Performance during extended walking in people with stroke was maintained over time. The electromyography amplitude decreased in the tibialis anterior during the pre-swing phase and increased in the rectus femoris during the single-support phase over time; these changes were similar on the paretic and nonparetic sides. Instantaneous mean frequency decreased over time on the nonparetic side in the tibialis anterior and on the paretic side in the rectus femoris. Healthy subjects did not show any changes over time. The changes in muscle activity in patients with stroke differed between the paretic and nonparetic sides, muscle type, and gait phase; walking performance was maintained despite being affected by neuromuscular fatigue.

Changes in electromyographic activity of deltoid muscles in women with shoulder pain during a functional task

BackgroundShoulder pain is one of the most common complaints of patients with musculoskeletal disorders in the shoulder and is usually caused by the Subacromial Impact Syndrome. Muscle imbalances can contribute to this syndrome leading to disorders that cause changes in muscle activity. The aim of this study was to determine whether pain causes changes in the electromyographic activity of the shoulder girdle muscles during an isometric task of arm elevation in the scapular plane. MethodThis is a comparative observational study using a simple convenience sampling method, composed of 22 women aged (44 ± 10) who were divided into two groups: 11 women with shoulder pain and 11 women without shoulder pain. The muscle activity evaluation was performed using surface electromyography of the muscles: anterior deltoid, middle deltoid, upper trapezius and middle trapezius, during an isometric task of arm elevation in the scapular plane. Independent Samples t-Test was used to analyze and compare the normalized electromyography data. ResultsResults revealed a significant increase in the activity of the anterior and middle deltoid muscles in women with shoulder pain compared to women without shoulder pain in the isometric task of arm elevation. ConclusionIt was concluded that the shoulder pain of the women evaluated caused changes in the activity of the anterior and middle deltoid muscles.