Central fatigue in continuous and intermittent contractions of triceps brachii

Conflicting results have been found across studies concerning the effect of rest periods on the development of central fatigue during prolonged muscle activity. Thus, the aim of the present study was to assess differences in the development of central fatigue between continuous and intermittent elbow extension fatigue tasks in the same subjects. Force and electromyographic data were collected on eight healthy volunteers. The ability to maximally activate the triceps brachii muscle was assessed by delivering trains of electrical stimulation during maximal voluntary efforts. This was done before, during, and after three fatigue tasks involving a maximal contraction in elbow extension. One short-duration ( approximately 55-s) and two long-duration (3-min) fatigue tasks were performed by all subjects on separate sessions. One 3-min task was intermittent (5-s rests every 30 s) and the other was continuous. The main findings were that the development and extent of central fatigue were task-dependent, with a greater decrease in the ability to maximally activate triceps brachii observed for the 3-min continuous task. Also, the voluntary activation (VA) ratio was found to be a more sensitive index of central fatigue than the central activation ratio (CAR). These results suggest that, when assessing central fatigue in patients, conclusions may vary depending on the continuous/intermittent nature of the task performed and the estimate of voluntary activation used.     

Electromyographic evaluation of the midvastus approach

Compared with the standard median parapatellar approach, the muscle-splitting midvastus approach to the knee has led to claims of an easier and earlier recovery after total knee arthroplasty, but some investigators have questioned whether the midvastus approach damages the vastus medialis obliquus. We used electromyographic and nerve conduction studies to evaluate whether we could document any such damage. Twenty patients undergoing bilateral total knee arthroplasty were randomized prospectively for the treatment of 1 knee with each of the 2 approaches. Radiographs, electromyographies, nerve conduction studies, range-of-motion tests, and Knee Society function and pain tests were conducted preoperatively and at 6 weeks postoperatively. If the electromyography or nerve conduction tests were abnormal at 6 weeks, the tests were repeated at 12 weeks. At the final follow-up, these studies showed no evidence of muscle denervation. The midvastus approach appears to be a safe alternative for knee arthrotomy for total knee arthroplasty without concerns for damage to the vastus medialis obliquus.     

猴下颌角截骨术后咬肌变化的影像学与肌电功能研究

目的:研究下颌角截骨术后咬肌形态与功能的变化情况。方法:12只成年雌性恒河猴分为3组,每组4只。各组经口内随机行一侧下颌角截骨术,做自身前后对照。术前及术后3、6、12个月时以CT和肌电仪动态检测术侧咬肌的厚度、横截面积和肌电电压峰值。结果:术后咬肌厚度、横截面积和肌电峰值均减小,这些变化在术后3个月最为明显,术后6个月开始恢复,但在术后12个月时仍与正常组有显著差异。结论:下颌角截除术使咬肌的形态与功能产生一定程度的萎缩与减弱,但随着时间的推移,有逐渐恢复的趋势。     

帕金森病患者的肛门括约肌肌电图与自主神经功能障碍分析

目的分析帕金森病(PD)患者的肛门括约肌肌电图(EAS-EMG)与自主神经功能障碍情况,探讨两者的相关性及两者与PD患者病情程度的相关性。方法选择2018年1～12月就诊于浙江省人民医院临床诊断为PD的50例患者作为观察组和19例健康对照者作为研究对象,两组均进行EAS-EMG检查及PD自主神经症状量表(SCOPA-AUT)评分,分析两组的检查结果及相关性。同时依据HY分期对PD患者进行病情分级,分析病情程度与EAS-EMG、SCOPA-AUT评分的相关性。结果观察组的EAS-EMG及SCOPA-AUT评分异常度均高于对照组(P0.05)。PD患者SCOPA-AUT得分与EAS-EMG的平均时限呈正相关(r=0.46,P=0.00),与平均波幅及多相波百分比不相关(r=0.27,0.14;P=0.06,0.32)。PD患者病情程度与EAS-EMG的平均时限呈正相关(r=0.50,P=0.00),而与平均波幅及多相波百分比不相关(r=0.18,0.17;P=0.21,0.25);病情程度与SCOPA-AUT评分呈正相关(r=0.68,P=0.00)。结论 PD患者的EAS-EMG存在异常,且普遍存在自主神经功能障碍;PD患者的EASEMG异常程度越高,病情越重,出现的自主神经功能障碍症状越多、越频繁。     

Shoulder muscle activation and coordination in patients with a massive rotator cuff tear: an electromyographic study

Adaptive muscle activation strategies following a massive rotator cuff tear (MRCT) are inadequately understood, and the relationship among muscles during everyday activities has not been considered. Thirteen healthy subjects comprised the control group, and 11 subjects with a MRCT the patient group. Upper limb function was assessed using the Functional Impairment test‐hand, neck, shoulder, and arm (FIT‐HaNSA). Electromyography (EMG) was recorded from 13 shoulder muscles, comprising five muscle groups, during a shelf‐lifting task. Mean FIT‐HaNSA scores were significantly lower in MRCT patients (p ≤ 0.001), reflecting a severe functional deficit. In MRCT patients, EMG signal amplitude was significantly higher for the biceps brachii‐brachioradialis (p < 0.001), upper trapezius‐serratus anterior (p = 0.025), muscle groups and for the latissimus dorsi (p = 0.010), and teres major (p = 0.007) muscles. No significant differences in the correlation among muscle groups were identified, pointing to an unchanged neuromuscular strategy following a tear. In MRCT patients, a reorganization of muscle activation strategy along the upper limb kinetic chain is aimed at reducing demand on the glenohumeral joint. Increased activation of the latissimus dorsi and teres major muscles is an attempt to compensate for the deficient rotator cuff. Re‐education towards an alternate neuromuscular control strategy appears necessary to restore function. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1140–1146, 2012     

A Spectral Analysis of Rotator Cuff Musculature Electromyographic Activity: Surface and Indwelling

Electromyography (EMG) of the shoulder girdle is commonly performed; however, EMG spectral properties of shoulder muscles have not been clearly defined. The purpose of this study was to determine the maximum power frequency, Nyquist rate, and minimum sampling rate for indwelling and surface EMG of the normal shoulder girdle musculature. EMG signals were recorded using indwelling electrodes for the rotator cuff muscles and surface electrodes for ten additional shoulder muscles in ten healthy volunteers. A fast Fourier transform was performed on the raw EMG signal collected during maximal isometric contractions to derive the power spectral density. The 95% power frequency was calculated during the ramp and plateau subphase of each contraction. Data were analyzed with analysis of variance (ANOVA) and paired t tests. Indwelling EMG signals had more than twice the frequency content of surface EMG signals (p < .001). Mean 95% power frequencies ranged from 495 to 560 Hz for indwelling electrodes and from 152 to 260 Hz for surface electrodes. Significant differences in the mean 95% power frequencies existed among muscles monitored with surface electrodes (p = .002), but not among muscles monitored with indwelling electrodes (p = .961). No significant differences in the 95% power frequencies existed among contraction subphases for any of the muscle–electrode combinations. Maximum Nyquist rate was 893 Hz for surface electrodes and 1,764 Hz for indwelling electrodes. Our results suggest that when recording EMG of shoulder muscles, the minimum sampling frequency is 1,340 Hz for surface electrodes and 2,650 Hz for indwelling electrodes. The minimum sampling recommendations are higher than the 1,000 Hz reported in many studies involving EMG of the shoulder.     

单纤维肌电图在诊断腕管综合征中的表现和评价

目的 分析、评价单纤维肌电图(single fiber electromyography,SFEMG)在诊断腕管综合征中的表现和作用.方法 将临床确诊的14例腕管综合征患者(共20侧)根据常规电生理神经传导检测数据分为两组:患侧跨腕段SNCV(感觉神经传导)均减慢,但拇短展肌CMAP(复合肌肉动作电位)潜伏期正常者为腕管Ⅰ组(10侧),拇短展肌CMAP的潜伏期4.3ms者为腕管Ⅱ组(10侧).各组均行SFEMG检测,得到拇短展肌的纤维密度(fiber density,FD)和单纤维动作电位间间隔的连续差均值(mean of consecutive difference,MCD).10例(10侧)健康志愿者为对照组,同法测取FD、MCD值.结果 术前各组SFEbfG检测结果 :拇短展肌MCD平均值,腕管Ⅰ组为67.86μs,较对照组延长了27.47μs;腕管Ⅱ组为83.36μs,较对照组延长了42.97μs.拇短展肌FD平均值,腕管Ⅰ组较对照组增加了0.46,腕管Ⅱ组较对照组增加了0.60.腕管Ⅰ、Ⅱ组的MCD、FD明显高于对照组,Ⅱ组MCD又明显高于Ⅰ组,而Ⅰ组、Ⅱ组FD则无明显差异.结论 单纤维肌电图检测为腕部正中神经卡压,特别是早期卡压的诊断提供了一项新的更为直接的客观指标.     

Microsurgical results with large vestibular schwannomas with preservation of facial and cochlear nerve function as the primary aim

Summary Objective. To evaluate our microsurgical results in dealing with vestibular schwannomas (VS) greater than or equal to 30 mm when preservation of cranial nerve function was considered more important than total tumour removal.Methods. Sixteen consecutive cases were operated on by the same neurosurgeon according to a prospective protocol using intraoperative neuro-monitoring (IONM) based on electromyographic and brain stem auditory evoked potential recordings. Facial nerve function was evaluated on the House-Brackmann Scale and cochlear nerve function on the Gardner-Robertson Scale. Someone not involved in the clinical management of our patients collected all data.Results. Fifteen patients showed facial nerve (FN) function of House-Brackmann grade (HBG) I or II at one year postoperatively and one kept the HBG IV she had preoperatively. Two patients of four maintained a cochlear nerve function of Gardner-Robertson grade (GRG) II. The tumour excision rates were: total, 68.7%; near total, 6.3%; subtotal, 18.7%, and partial, 6.3%. The average follow-up was 55 months (1–106). Three patients underwent radiotherapy later with growth stabilisation and no additional morbidity.Conclusion. When dealing with VS greater than or equal to 30 mm, microsurgery guided by IONM, with a rate of total or near-total tumour excision of about 75%, can retain socially acceptable facial nerve function (HBG I or II) in all cases and serviceable hearing (GRG I or II) in two cases out of four. Maintaining serviceable cranial nerve function should take precedence over total tumour excision.