Electromyographic Parameters of Muscle Fatigue in Patients with Parkinsonism

The authors studied muscle fatigue in patients with parkinsonism receiving pathogenetic therapy and in elderly healthy subjects by means of turn-amplitude analysis of surface electromyography (EMG). The healthy subjects reacted to fatigue with a significant increase in the amplitude and number of EMG turns during static exercise and a decrease in the peak ratio. In patients with parkinsonism, fatigue began after an exercise that was half of that in the healthy subjects with a decrease in the number of turns and mean amplitude and an increase in peak ratio. These data show that dynamics of strength and EMG parameters differs in patients with parkinsonism and healthy subjects.     

Electromyographic Parameters of Muscular Fatigue in Patients with Parkinson's Disease after General Cooling of the Body

The process of muscular fatigue was studied in ten patients (at the age of 59–65 years) with the rigid akinetic form of Parkinson's disease under cooling (+10°C, 60 min), during therapy (Nakom or Cyclodol), as compared to neutral thermal conditions (+22°C), using surface electromyography (EMG) and turn-amplitude analysis. Clear stages were found in the pattern of change of the turn-amplitude analysis, both in neutral thermal conditions and under cooling. A thermoregulatory component of the muscular activity was found after cooling and fatigue at small static loads. In addition, cooling and fatigue brought about an alleviation of the hidden tremor component of the EMG in patients with Parkinson's disease (in 30% of cases) and therefore can serve as a functional test. Cooling and dynamic loads reduce muscular power and decrease oligobradykinesia.     

Administration of Dihydroxyphenylalanine to Parkinsonian Patients

Dihydroxyphenylalanine (dopa), the metabolic precursor of dopamine, was administered to 10 parkinsonian patients in oral doses of 1-5 g. and intravenous doses of 0.2-0.5 g. Increases in dopamine excretion of 100- to 1000-fold following the dopa administration indicated that dopa was being absorbed and metabolized. Only two of the 10 patients showed any objective improvement on this treatment. Although dopa did not show sufficient beneficial results in this study to be considered a useful therapeutic agent, its slight activity is consistent with other evidence suggesting that some extrapyramidal cells are sensitive to dopamine.     

Interrelations between EEG Parameters and Personality Characteristics in Parkinsonian Patients

We studied a number of EEG parameters and indices of personality characteristics (evaluated with the use of the MMPI questionnaire) in sixty 44- to 73-year-old patients with Parkinson's disease (PD). According to the intensity of the symptoms, they were classified into groups 1 and 2, with an initial or moderate level of disease manifestation. In group-2 patients, the powers of the - and -range rhythms were greater, as compared with those in group 1. This was combined with higher indices in scales 2 (depression, D), 8 (individualism, Sc), and 0 (introversion/extraversion, Si). A clear correlations between the EEG parameters and indices of personality structure were found. There were positive correlations between the normalized power of ₂-rhythm and values of a few MMPI scales: 1 (supercontrol, Hs), 2 (depression, D), 4 (impulsivity, Pd), 7 (anxiety, Pt), 8 (individualism, Sc), and 0 (introversion/extraversion, Si). We also found negative correlations between the frequency of -rhythm and indices of supercontrol and anxiety scales. Correlations between different EEG parameters and MMPI scale indices depended on the level of disease manifestation. Our results allow us to assume a certain generality of the neurophysiological mechanisms determining modifications of the integral electrical activity of the brain and formation of individual psychological characteristics in parkinsonian patients.     

Differences in Muscle Strength in Parkinsonian Patients Affected on the Right and Left Side

Background

Muscular weakness is a frequent cause of instability that contributes to falls in Parkinson’s disease (PD). Isokinetic dynamometry is a method of muscle assessment useful to measure the muscular strength giving a quantification of the weakness, but only few studies about isokinetic assessment were performed in PD. The aims of the study were to evaluate the muscle strength in PD and to investigate the differences in patients affected on the right and left side.

Methods

Knee flexor and extensor muscles strength was assessed using an isokinetic dynamometer in 25 patients in stage 3 H&Y and in 15 healthy controls. Subjects were tested in both legs at three fixed angular velocities: 90°/s, 120°/s, 180°/s.

Results

Considering the whole population of Parkinsonians, no difference in strength was observed with respect to controls. Considering the side, patients affected on the right side showed a clear tendency to be weaker than patients affected on the left side and controls.

Conclusions

PD patients affected on the right side, but not those affected on the left side, had a reduction in muscle strength as compared to controls. We postulate a central origin deficit in muscle strength in PD. It is known that dopamine transporter binding is more severely reduced in the left posterior putamen and our results suggest that the control of the muscle strength in PD is linked to the right–left hemispheric asymmetry of the functional organization of basal ganglia and with their connections to cortical motor and pre-motor areas.     

Quadriceps and Respiratory Muscle Fatigue Following High-Intensity Cycling in COPD Patients

Exercise intolerance in COPD seems to combine abnormal ventilatory mechanics, impaired O₂ transport and skeletal muscle dysfunction. However their relatie contribution and their influence on symptoms reported by patients remain to be clarified. In order to clarify the complex interaction between ventilatory and neuromuscular exercise limiting factors and symptoms, we evaluated respiratory muscles and quadriceps contractile fatigue, dynamic hyperinflation and symptoms induced by exhaustive high-intensity cycling in COPD patients. Fifteen gold II-III COPD patients (age = 67±6 yr; BMI = 26.6±4.2 kg.m^-2) performed constant-load cycling test at 80% of their peak workload until exhaustion (9.3±2.4 min). Before exercise and at exhaustion, potentiated twitch quadriceps strength (Q_tw), transdiaphragmatic (P_di,tw) and gastric (P_ga,tw) pressures were evoked by femoral nerve, cervical and thoracic magnetic stimulation, respectively. Changes in operational lung volumes during exercise were assessed via repetitive inspiratory capacity (IC) measurements. Dyspnoea and leg discomfort were measured on visual analog scale. At exhaustion, Q_tw (-33±15%, >15% reduction observed in all patients but two) and P_di,tw (-20±15%, >15% reduction in 6 patients) were significantly reduced (P<0.05) but not P_ga,tw (-6±10%, >15% reduction in 3 patients). Percentage reduction in Q_tw correlated with the percentage reduction in P_di,tw (r=0.66; P<0.05). Percentage reductions in P_di,tw and P_ga,tw negatively correlated with the reduction in IC at exhaustion (r=-0.56 and r=-0.62, respectively; P<0.05). Neither dyspnea nor leg discomfort correlated with the amount of muscle fatigue. In conclusion, high-intensity exercise induces quadriceps, diaphragm and less frequently abdominal contractile fatigue in this group of COPD patients. In addition, the rise in end-expiratory lung volume and diaphragm flattening associated with dynamic hyperinflation in COPD might limit the development of abdominal and diaphragm muscle fatigue. This study underlines that both respiratory and quadriceps fatigue should be considered to understand the complex interplay of factors leading to exercise intolerance in COPD patients.     

Effects of Quadriceps Muscle Fatigue on Stiff-Knee Gait in Patients with Hemiparesis

The relationship between neuromuscular fatigue and locomotion has never been investigated in hemiparetic patients despite the fact that, in the clinical context, patients report to be more spastic or stiffer after walking a long distance or after a rehabilitation session. The aim of this study was to evaluate the effects of quadriceps muscle fatigue on the biomechanical gait parameters of patients with a stiff-knee gait (SKG). Thirteen patients and eleven healthy controls performed one gait analysis before a protocol of isokinetic quadriceps fatigue and two after (immediately after and after 10 minutes of rest). Spatiotemporal parameters, sagittal knee and hip kinematics, rectus femoris (RF) and vastus lateralis (VL) kinematics and electromyographic (EMG) activity were analyzed. The results showed that quadriceps muscle weakness, produced by repetitive concentric contractions of the knee extensors, induced an improvement of spatiotemporal parameters for patients and healthy subjects. For the patient group, the increase in gait velocity and step length was associated with i) an increase of sagittal hip and knee flexion during the swing phase, ii) an increase of the maximal normalized length of the RF and VL and of the maximal VL lengthening velocity during the pre-swing and swing phases, and iii) a decrease in EMG activity of the RF muscle during the initial pre-swing phase and during the latter 2/3 of the initial swing phase. These results suggest that quadriceps fatigue did not alter the gait of patients with hemiparesis walking with a SKG and that neuromuscular fatigue may play the same functional role as an anti-spastic treatment such as botulinum toxin-A injection. Strength training of knee extensors, although commonly performed in rehabilitation, does not seem to be a priority to improve gait of these patients.     

Muscle Activity Adaptations to Spinal Tissue Creep in the Presence of Muscle Fatigue

Aim

The aim of this study was to identify adaptations in muscle activity distribution to spinal tissue creep in presence of muscle fatigue.

Methods

Twenty-three healthy participants performed a fatigue task before and after 30 minutes of passive spinal tissue deformation in flexion. Right and left erector spinae activity was recorded using large-arrays surface electromyography (EMG). To characterize muscle activity distribution, dispersion was used. During the fatigue task, EMG amplitude root mean square (RMS), median frequency and dispersion in x- and y-axis were compared before and after spinal creep.

Results

Important fatigue-related changes in EMG median frequency were observed during muscle fatigue. Median frequency values showed a significant main creep effect, with lower median frequency values on the left side under the creep condition (p≤0.0001). A significant main creep effect on RMS values was also observed as RMS values were higher after creep deformation on the right side (p = 0.014); a similar tendency, although not significant, was observed on the left side (p = 0.06). A significant creep effects for x-axis dispersion values was observed, with higher dispersion values following the deformation protocol on the left side (p≤0.001). Regarding y-axis dispersion values, a significant creep x fatigue interaction effect was observed on the left side (p = 0.016); a similar tendency, although not significant, was observed on the right side (p = 0.08).

Conclusion

Combined muscle fatigue and creep deformation of spinal tissues led to changes in muscle activity amplitude, frequency domain and distribution.     

Oxygenation and Hemodynamics Do Not Underlie Early Muscle Fatigue for Patients with Work-Related Muscle Pain

Patients suffering from work-related muscle pain (WRMP) fatigue earlier during exercise than healthy controls. Inadequate oxygen consumption and/or inadequate blood supply can influence the ability of the muscles to withstand fatigue. However, it remains unknown if oxygenation and hemodynamics are associated with early fatigue in muscles of WRMP patients. In the present study we applied near-infrared spectroscopy (NIRS) on the extensor carpi radialis (ECR) and trapezius (TD) muscles of patients with WRMP (n = 18) and healthy controls (n = 17). Our objective was to determine if there were group differences in endurance times for a low-level contraction of 15% maximal voluntary contraction (MVC) – sustained for 12–13 min, and to see if these differences were associated with differences in muscle oxygenation and hemodynamics. At baseline, oxygen saturation (StO₂%) was similar between groups for the ECR, but StO₂% was significantly lower for TD for the WRMP patients (76%) compared to controls (85%) (P<0.01). Also, baseline ECR blood flow was similar in the two groups. For both muscles there were a larger number of patients, compared to controls, that did not maintain the 15% MVC for the allotted time. Consequently, the endurance times were significantly shorter for the WRMP patients than controls (medians, ECR: 347 s vs. 582 s; TD: 430 s vs. 723 s respectively). Responses in StO₂% during the contractions were not significantly different between groups for either muscle, i.e. no apparent difference in oxygen consumption. Overall, we interpret our findings to indicate that the early fatigue for our WRMP patients was not associated with muscle oxygenation and hemodynamics.     

Phenylalanine Absorption and Metabolism in Parkinsonian Patients

Oral and intravenous L-phenylalanine loading tests were performed in 13 Parkinsonian patients and in 12 control subjects matched for age and weight. The results showed a normal intestinal absorption and a normal elimination from plasma of phenylalanine in the Parkinsonian patients.     

The Effects of Vibration and Muscle Fatigue on Trunk Sensorimotor Control in Low Back Pain Patients

Introduction

Changes in sensorimotor function and increased trunk muscle fatigability have been identified in patients with chronic low back pain (cLBP). This study assessed the control of trunk force production in conditions with and without local erector spinae muscle vibration and evaluated the influence of muscle fatigue on trunk sensorimotor control.

Methods

Twenty non-specific cLBP patients and 20 healthy participants were asked to perform submaximal isometric trunk extension torque with and without local vibration stimulation, before and after a trunk extensor muscle fatigue protocol. Constant error (CE), variable error (VE) as well as absolute error (AE) in peak torque were computed and compared across conditions. Trunk extensor muscle activation during isometric contractions and during the fatigue protocol was measured using surface electromyography (sEMG).

Results

Force reproduction accuracy of the trunk was significantly lower in the patient group (CE = 9.81 ± 2.23 Nm; AE = 18.16 ± 3.97 Nm) than in healthy participants (CE = 4.44 ± 1.68 Nm; AE = 12.23 ± 2.44 Nm). Local erector spinae vibration induced a significant reduction in CE (4.33 ± 2.14 Nm) and AE (13.71 ± 3.45 Nm) mean scores in the patient group. Healthy participants conversely showed a significant increase in CE (8.17 ± 2.10 Nm) and AE (16.29 ± 2.82 Nm) mean scores under vibration conditions. The fatigue protocol induced erector spinae muscle fatigue as illustrated by a significant decrease in sEMG median time-frequency slopes. Following the fatigue protocol, patients with cLBP showed significant decrease in sEMG root mean square activity at L4-5 level and responded in similar manner with and without vibration stimulation in regard to CE mean scores.

Conclusions

Patients with cLBP have a less accurate force reproduction sense than healthy participants. Local muscle vibration led to significant trunk neuromuscular control improvements in the cLBP patients before and after a muscle fatigue protocol. Muscle vibration stimulation during motor control exercises is likely to influence motor adaptation and could be considered in the treatment of cLBP. Further work is needed to clearly identify at what levels of the sensorimotor system these gains are achievable.     

Oral Phenylalanine and Tyrosine Tolerance Tests in Parkinsonian Patients

Reduction of dopamine concentrations in the brains of patients with Parkinsonism, together with reported clinical improvement after the administration of dihydroxyphenylalanine, has led to the hypothesis that impaired hydroxylation of tyrosine may be associated with the disease. To test this hypothesis oral loading tests with L-phenylalanine and tyrosine were carried out in patients and controls. After phenylalanine lower blood levels of this were found in Parkinsonian patients than in controls, but tyrosine levels were the same. After tyrosine lower levels of this were also found in patients compared with controls. It is suggested that these findings indicate a decreased rate of tyrosine utilization in Parkinson''s disease together with intestinal malabsorption; the latter is supported by the finding of abnormal D-xylose tolerance in these patients.     

Assessment of Autonomic Function in Patients with a Parkinsonian Syndrome

The integrity of the autonomic nervous system was assessed in 11 Parkinsonian patients with symptoms suggestive of autonomic dysfunction. Three had the additional clinical features of the Shy-Drager variant of idiopathic orthostatic hypotension and were found to have a gross disturbance of vasomotor, sudomotor, pilomotor, and bladder function; assessment indicated that a lesion was present at sympathetic ganglionic level or beyond in two cases, though a more centrally placed lesion may well have been present also, as in the third case. In the remaining eight patients with paralysis agitans no unequivocal functional disturbance was found except in the bladder; nevertheless, the low resting blood pressure and the supersensitivity to intravenously infused L-noradrenaline in the three patients in whom it was tested is taken to imply defective regulation from higher centres, with a consequent reduction in impulse traffic at sympathetic nerve terminals. Such a concept is supported by experimental studies in animals and would account for the low renin and aldosterone secretion rates and reduced noradrenaline formation reported by others in patients with paralysis agitans.     

Effect of Age and Arteriosclerosis on the Response of Parkinsonian Patients to Levodopa

Twenty-four patients with Parkinsonism were treated with levodopa for up to one year. Ten were aged under 65, 12 were aged 65 or over, and two were specifically included because they were considered to have arteriosclerotic Parkinsonism. These two patients showed no response to treatment. The 10 younger patients showed less clinical evidence of arteriosclerosis than the older ones, and responded significantly better to treatment with levodopa. Mean improvement was 61% in the younger group after 12 months'' treatment and 28% in the older group. Improvement was greatest within three months of starting treatment. Abnormal movements which resulted from treatment with levodopa could be reduced with only slight loss of therapeutic benefit by the addition of tetrabenazine.     

Proteomic Analysis of Gastrocnemius Muscle in Rats with Streptozotocin-Induced Diabetes and Chronically Exposed to Fluoride

Administration of high doses of fluoride (F) can alter glucose homeostasis and lead to insulin resistance (IR). This study determined the profile of protein expression in the gastrocnemius muscle of rats with streptozotocin-induced diabetes that were chronically exposed to F. Male Wistar rats (60 days old) were randomly distributed into two groups of 18 animals. In one group, diabetes was induced through the administration of streptozotocin. Each group (D-diabetic and ND-non-diabetic) was further divided into 3 subgroups each of which was exposed to a different F concentration via drinking water (0 ppm, 10 ppm or 50 ppm F, as NaF). After 22 days of treatment, the gastrocnemius muscle was collected and submitted to proteomic analysis (2D-PAGE followed by LC-MS/MS). Protein functions were classified by the GO biological process (ClueGO v2.0.7+Clupedia v1.0.8) and protein-protein interaction networks were constructed (PSICQUIC, Cytoscape). Quantitative intensity analysis of the proteomic data revealed differential expression of 75 spots for ND0 vs. D0, 76 for ND10 vs.D10, 58 spots for ND50 vs. D50, 52 spots for D0 vs. D10 and 38 spots for D0 vs. D50. The GO annotations with the most significant terms in the comparisons of ND0 vs. D0, ND10 vs. D10, ND50 vs. D50, D0 vs. D10 and D0 vs. D50, were muscle contraction, carbohydrate catabolic processes, generation of precursor metabolites and energy, NAD metabolic processes and gluconeogenesis, respectively. Analysis of subnetworks revealed that, in all comparisons, proteins with fold changes interacted with GLUT4. GLUT4 interacting proteins, such as MDH and the stress proteins HSPB8 and GRP78, exhibited decreased expression when D animals were exposed to F. The presence of the two stress proteins indicates an increase in IR, which might worsen diabetes. Future studies should evaluate whether diabetic animals treated with F have increased IR, as well as which molecular mechanisms are involved.     

Characteristics of the Integrated Electromyogram in Individuals Exposed to Long-Term Vibration

The functional state of the forearm muscles in individuals exposed to long-term vibration (dressers with a duration of current employment of 7–15 years, n = 12) was assessed using turn–amplitude analysis of the integrated surface electromyogram (EMG), the nerve conduction velocity test, and the conventional motor unit action potential electromyographic test. A significant increase in the EMG amplitude and the number of turns upon graded effort, as well as a decrease in the maximal ratio of the number of turns to the average amplitude of the electromyogram from the right m. flexor carpi radialis of the dressers, was revealed, which is indicative of secondary muscular disorders connected with the specific features of the occupational movement pattern and long-term exposure to vibration.     

应用振动训练可修复小鼠肌肉疲劳损伤

为探讨不同强度全身振动训练对于生物体运动表现、运动疲劳以及生理生化反应的影响。本研究使用4周大雄性C57BL/6J小鼠为模型,随机分作3组,每组8只动物:无振动训练对照组(sedentary control,SC);相对较低强度振动训练组(5.6 Hz/0.13 g; relative low-intensity vibration, LV);相对较高强度振动训练组(13 Hz/0.68 g; relative high-intensity vibration, HV)。振动训练以每天振动15 min,每周5次,为期4周,随后进行各项测试包括:前肢抓力、衰竭性耐力运动测验、疲劳生化指标分析、临床血液生化检测以及病理组织切片观察。数据以单因素方差进行分析,并以Duncan's test检验不同的组间是否存在显著差异。两组接受振动训练介入的小鼠比对照组,具有显著提升肌力和衰竭性耐力运动的时间。在疲劳与肌肉损伤相关生化指标部分,振动训练具有明显降低单次运动测试后血氨与血乳酸浓度以及肌酸激酶活性上升的作用。在临床血液生化方面,4周振动训练显著降低草醋酸转胺酶、麸丙酮酸转胺酶与肌酸激酶活性,以及尿素氮浓度。本研究证实振动训练4周的连续介入下,具有提升运动表现与抗疲劳的作用,而且不会造成健康小鼠在生理生化以及病理上的副作用。在提供一般健康成人的运动训练指导上,全身振动训练具有健康促进的应用性。     

Extraocular Muscle Characteristics Related to Myasthenia Gravis Susceptibility

Background

The pathogenesis of extraocular muscle (EOM) weakness in myasthenia gravis might involve a mechanism specific to the EOM. The aim of this study was to investigate characteristics of the EOM related to its susceptibility to myasthenia gravis.

Methods

Female F344 rats and female Sprague-Dawley rats were assigned to experimental and control groups. The experimental group received injection with Ringer solution containing monoclonal antibody against the acetylcholine receptor (AChR), mAb35 (0.25 mg/kg), to induce experimental autoimmune myasthenia gravis, and the control group received injection with Ringer solution alone. Three muscles were analyzed: EOM, diaphragm, and tibialis anterior. Tissues were examined by light microscopy, fluorescence histochemistry, and transmission electron microscopy. Western blot analysis was used to assess marker expression and ELISA analysis was used to quantify creatine kinase levels. Microarray assay was conducted to detect differentially expressed genes.

Results

In the experimental group, the EOM showed a simpler neuromuscular junction (NMJ) structure compared to the other muscles; the NMJ had fewer synaptic folds, showed a lesser amount of AChR, and the endplate was wider compared to the other muscles. Results of microarray assay showed differential expression of 54 genes in the EOM between the experimental and control groups.

Conclusion

Various EOM characteristics appear to be related to the increased susceptibility of the EOM and the mechanism of EOM weakness in myasthenia gravis.