Age‐associated changes in muscle activity during isometric contraction

Introduction: We investigated the effect of age on the complexity of muscle activity and the variance in the force of isometric contraction. Methods: Surface electromyography (sEMG) from biceps brachii muscle and force of contraction were recorded from 96 subjects (20–70 years of age) during isometric contractions. Results: There was a reduction in the complexity of sEMG associated with aging. The relationship of age and complexity was approximated using a bilinear fit, with the average knee point at 45 years. There was an age‐associated increase in the coefficient of variation (CoV) of the force of muscle contraction, and this increase was correlated with the decrease in complexity of sEMG (r² = 0.76). Conclusions: There was an age‐associated increase in CoV and also a reduction in the complexity of sEMG. The correlation between these 2 factors can be explained based on the age‐associated increase in motor unit density. Muscle Nerve 47: 545–549, 2013     

Spasticity,weakness, force variability,and sustained spontaneous motor unit discharges of resting spastic–paretic biceps brachii muscles in chronic stroke

Introduction: The purpose of our study was to examine relations among spasticity, weakness, force variability, and sustained spontaneous motor unit discharges in spastic–paretic biceps brachii muscles in chronic stroke. Methods: Ten chronic stroke subjects produced submaximal isometric elbow flexion force on impaired and non‐impaired sides. Intramuscular EMG (iEMG) was recorded from biceps and triceps brachii muscles. Results: We observed sustained spontaneous motor unit discharges in resting biceps on iEMG. Spontaneous discharges increased after voluntary activation only on the impaired side. The impaired side had greater matching errors and greater fluctuations in isometric force. Spontaneous discharges were not related functionally to spasticity, force variability, or weakness. However, greater strength on the impaired side correlated with less force variability. Conclusion: Weakness rather than spasticity is a main factor interfering with voluntary force control in paretic–spastic biceps brachii muscles in chronic stroke. Muscle Nerve, 2013     

多模式神经电生理检测对脊髓手术患者神经功能状态的评估分析及其影响因素

 目的 使用肌电图(electromyography,EMG)、体感诱发电位(somatosensory evoked potential,SEP)与运动诱发电位(motor evoked potentials,MEP)多模式方法检测手术前后神经系统的多种电生理信号,探讨患者神经功能状态。方法 收集100例患者作为研究对象,术中监测患者双下肢的SEP与MEP情况;术后6个月复查患者EMG。结果 术中SEP波幅与潜伏期在较稳定情况下,MEP监测中42例患者术中的D波波幅发生降低未超过50%,22例患者出现D波波幅突然下降且超过50%。Pearson相关性分析结果表明,术中出血量与SEP及MEP波幅与潜伏期的改变具有相关性。术后复查,各组患者的腓总神经与胫神经的NCV与DL均有显著改善,异常组患者的改善情况明显低于其他四组。结论 使用EMG、SEP与MEP多模式神经电生理检测可以去除干扰因素,为脊髓手术提供客观、有价值的诊疗依据。     

Neural adaptations after 4 years vs 12 weeks of resistance training vs untrained

The purpose of this study was to compare the effect of resistance training (RT) duration, including years of exposure, on agonist and antagonist neuromuscular activation throughout the knee extension voluntary torque range. Fifty‐seven healthy men (untrained [UNT] n = 29, short‐term RT [12WK] n = 14, and long‐term RT [4YR] n = 14) performed maximum and sub‐maximum (20%‐80% maximum voluntary torque [MVT]) unilateral isometric knee extension contractions with torque, agonist and antagonist surface EMG recorded. Agonist EMG, including at MVT, was corrected for the confounding effects of adiposity (ie, muscle‐electrode distance; measured with ultrasonography). Quadriceps maximum anatomical cross‐sectional area (QACSA_MAX; via MRI) was also assessed. MVT was distinct for all three groups (4YR +60/+39% vs UNT/12WK; 12WK +15% vs UNT; 0.001 < P ≤ 0.021), and QACSA_MAX was greater for 4YR (+50/+42% vs UNT/12WK; [both] P < 0.001). Agonist EMG at MVT was +44/+33% greater for 4YR /12WK ([both] P < 0.001) vs. UNT, but did not differ between RT groups. The torque‐agonist EMG relationship of 4YR displayed a right/down shift with lower agonist EMG at the highest common torque (196 Nm) compared to 12WK and UNT (0.005 ≤ P ≤ 0.013; Effect size [ES] 0.90 ≤ ES ≤ 1.28). The torque‐antagonist EMG relationship displayed a lower slope with increasing RT duration (4YR < 12WK < UNT; 0.001 < P ≤ 0.094; 0.56 ≤ ES ≤ 1.31), and antagonist EMG at the highest common torque was also lower for 4YR than UNT (?69%; P < 0.001; ES = 1.18). In conclusion, 4YR and 12WK had similar agonist activation at MVT and this adaptation may be maximized during early months of RT. In contrast, inter‐muscular coordination, specifically antagonist coactivation was progressively lower, and likely continues to adapt, with prolonged RT.     

Electromyographic activity of masticatory, neck and trunk muscles of subjects with different skeletal facial morphology--a cross-sectional evaluation

The electromyographic pattern activity of masticatory, neck and trunk muscles was assessed using surface electromyography (sEMG) in 60 Caucasian adult females (20 subjects in skeletal class I, 20 subjects in skeletal class II and 20 subjects in skeletal class III), classified on the base of their skeletal class (ANB angle), corrected on the base of maxillary and mandibular rotations. The sEMG activity was recorded at mandibular rest position and during maximal voluntary clenching. At mandibular rest position, the sEMG activities of masseter and anterior temporal muscles were significantly higher in class III subjects than in class I and class II subjects, that showed no significant difference between them. Then, the sEMG activities of posterior cervicals and upper trapezius were significantly higher in skeletal class III subjects than in the other two groups. During maximal voluntary clenching, no significant difference was observed in the sEMG activity of masticatory muscles among the three considered groups. However, the sEMG activities of posterior cervicals and upper trapezius were significantly higher in skeletal class III subjects than in the other two groups, which showed no significant difference between them. In conclusion, the skeletal class seems to affect the sEMG pattern activity of masticatory, neck and trunk muscles.     

Review of clinical EMG studies related to muscle and occlusal factors in healthy and TMD subjects

Several electronic instruments have been developed as adjuncts to objectively record the dysfunctional features of temporomandibular disorders and to study the effectiveness of various treatment interventions. The aim of this review was to assess the value and contribution of clinical electromyographic research in the understanding of asymptomatic and dysfunctional muscle function and the therapeutic effects of interocclusal appliances. For this purpose MedLine and PubMed searches were conducted with the following main keywords alone and in various combinations: electromyography, muscles of mastication, masseter, temporalis, temporomandibular, TMD, utility, validity, repeatability, rest, postural, vertical dimension, occlusal, splint, treatment. The review includes critical evaluation, discussion and conclusions regarding electromyographic studies in asymptomatic and dysfunctional muscles, rest position, occlusal parameters and interocclusal appliances, as well as a critical summary and proposals for further research. Much of earlier critique of many electromyographic studies still applies regarding comparative sample selections, research designs, analyses and conclusions. The areas not well-understood include normal biological variation, capacity for adaptation, fluctuations regarding the clinical course and multidimensional features of temporomandibular disorders and long-term follow-up data, especially in studies that evaluate the effectiveness of therapeutic measures. Considering the required improvements in technical and research designs features and critical appraisal electromyographic research could have value as an adjunct research tool to study features of craniofacial muscle-related dysfunction. Until electromyographic measures are correlated with other multidimensional, especially subjective and pain-related methods, the clinical use of this method for diagnostic purposes of temporomandibular disorders remains in doubt, and is not at present recommended.     

四子散热熨对压力性尿失禁患者盆底功能康复的影响

目的 探讨四子散热熨对轻中度压力性尿失禁患者盆底功能的康复作用。方法 将女性轻中度压力性尿失禁患者随机分为对照组(n=39)和观察组(n=38)。对照组采用常规康复护理,观察组在对照组基础上采用四子散热熨,每次20 min, 3次/周,连续干预4周。干预前后评估患者盆底肌肉功能、盆底组织形态和尿失禁总体情况,干预1个月后随访时评估患者尿失禁总体情况和尿失禁疗效。结果 干预后观察组盆底表面肌电值前静息阶段、快速收缩阶段和后静息阶段康复效果和肛提肌裂孔面积显著优于对照组;干预后与随访时,观察组尿失禁总体评分显著优于对照组,干预后观察组尿失禁疗效显著优于对照组(P<0.05,P<0.01)。结论 四子散热熨能促进轻中度压力性尿失禁患者盆底功能康复,改善尿失禁。     

干扰型分析在诊断神经肌肉疾病中的应用

应用ＳｔａｌｌｂｅｒｇＥ的干扰型分析技术，对１０例正常人和２０例神经肌肉疾病患者进行传统肌电图和干扰型分析检测。结果表明该分析技术较之常规的运动单位定量分析具有快捷，准确率高的优点。