Acute and cumulative effects of rTMS on behavioural and EMG parameters in Focal Hand Dystonia

Previous studies suggest that low-frequency repetitive Transcranial Magnetic Stimulation (rTMS) over contralateral premotor cortex (PMC) might ameliorate Focal Hand Dystonia (FHD) symptoms. In the present study behavioral and muscle activity outcomes were explored in a patient with FHD following a single and multiple sessions of rTMS. The patient's behavior was assessed on handwriting tasks, while surface EMG signals were recorded. In Experiment 1 evaluations were performed before and after one session of active and sham 1Hz rTMS over contralateral PMC. In Experiment 2, evaluations were performed before and after six sessions of the same treatment. In Experiment 1 active rTMS improved the patient's performance, although the EMG amplitude did not change. In Experiment 2, the patient showed an improvement of performance along with a decrease of 20% in the EMG amplitude. These results demonstrated that a single session of rTMS ameliorated the patient's performance, while multiple sessions were necessary to reduce muscles activity

Motor unit firing rates and synchronisation affect the fractal dimension of simulated surface electromyogram during isometric/isotonic contraction of vastus lateralis muscle

During fatiguing contractions, many adjustments in motor units behaviour occur: decrease in muscle fibre conduction velocity; increase in motor units synchronisation; modulation of motor units firing rate; increase in variability of motor units inter-spike interval. We simulated the influence of all these adjustments on synthetic EMG signals in isometric/isotonic conditions. The fractal dimension of the EMG signal was found mainly influenced by motor units firing behaviour, being affected by both firing rate and synchronisation level, and least affected by muscle fibre conduction velocity. None of the calculated EMG indices was able to discriminate between firing rate and motor units synchronisation

Andrea Pozzo (1642-1709) pittore e prospettico in Italia settentrionale

Il volume analizza in modo sistematico l'attività di Andrea Pozzo in Lombardia, Ligura e Piemonte, nel corso degli anni sessanta e settanta del Seicento, prima della partenza dell'artista gesuita per Roma, nel 1681

Electromyographic Manifestations of Fatigue Correlate With Pulmonary Function, 6-Minute Walk Test, and Time to Exhaustion in COPD

BACKGROUND: The aim of this study was to investigate whether electromyographic manifestations of fatigue and exercise tolerance were related to stage of disease in men with a COPD diagnosis. METHODS: Fourteen men with COPD with a diagnosis of mild to severe air flow obstruction were involved in 2 separate testing sessions. The first one consisted of a pulmonary function (FEV1 and FEV1/FVC) and an exercise tolerance assessment using the 6-min walk test. During the second session, a multichannel surface electromyography was recorded from vastus medialis and vastus lateralis muscles during an isometric knee extension at 70% of maximum voluntary contraction. The slope of muscle fiber conduction velocity during the contraction was calculated as the index of fatigue. RESULTS: Conduction velocity slope significantly correlated with FEV1 (vastus medialis: r = 0.86, P < .001; vastus lateralis: r = 0.68, P = .01), FEV1/FVC (vastus medialis: r = 0.70, P = .006), and 6-min walk test (vastus medialis: r = 0.72, P = .005; vastus lateralis: r = 0.80, P = .001). CONCLUSIONS: The electromyographic manifestations of fatigue during sustained quadriceps contraction significantly correlated with disease severity and exercise tolerance in moderate to severe COPD

Differences in age-related fiber atrophy between vastii muscles of active subjects : a multichannel surface EMG study

The aim of the study was to non-invasively determine if vastus lateralis (VL) and vastus medialis obliquus (VM) muscles are equally affected by age-related fiber atrophy. Multichannel surface electromyography was used since it allows to estimate muscle fiber conduction velocity (CV), which has been demonstrated to be related to the size of recruited muscle fibers. Twelve active elderly men (age 69 +/- 4 years) and 12 active young men (age 23 +/- 2 years) performed isometric knee extension at 30%, 50%, and 70% of maximal voluntary contraction. Electromyographic signals were recorded from VL and VM muscles of the dominant limb using arrays with eight electrodes and CVs were estimated for each contraction. CV estimates showed a different behavior in the two muscles: in VL at 50% and 70% of maximum voluntary contraction they were greater in young than in elderly; whereas such a difference was not observed in VM. This finding suggest that in active elderly VM seems to be less affected by the age-related fibers atrophy than VL. Hence, the common choice of studying VL as a muscle representative of the whole quadriceps could generate misleading findings. Indeed, it seemed that the sarcopenic ageing effects might be heterogeneous within quadriceps muscle

Gender differences in neuromuscular fatigue after 21km run

Aim: Little is known about the gender differences in fatigue during prolonged locomotor exercise. This study investigated possible gender differences in central and peripheral fatigue and in the rate of force development in the knee extensor muscles after 21 km run. Methods: Ten males and eight females amateur runners (aged 25 to 50 years) were evaluated before and immediately after the \u201cRun for Science\u201d 21 km race. Knee extensors forces were obtained under voluntary and electrically evoked isometric contractions. Maximal voluntary isometric contraction (MVC), rate of force development (RFD), and relative RFD (i.e. RFD/MVC) were obtained. Electrically elicited twitches were recorded during MVC [interpolated twitch (IT)] and at rest [resting twitch (RT)], and the level of voluntary activation (VA) during each MVC was calculated as VA(%)=100(1-IT/RT). Electromechanical delays (EMD) were calculated as the difference between the onset of electromyographic activity in vastus lateralis and the onset of force production. Results: Changes in most neuromuscular variables were found similar between males (former values) and females (latter values), such as MVC (-14%, - 11%, p=0.41), RFD (-20%, -11%, p=0.24), relative RFD (-1%, - 7%, p=0.14), voluntary activation (-7%, -4%, p=0.54), and resting twitch (+ 2%, - 8%, p=0.20). The EMD showed different behaviours between genders (p=0.02) since were found increased in females (+20%) and decreased in males (-19%). Conclusions: Contrary to the expectation, no difference in voluntary force expressions (MVC and RFD) was observed between genders. Otherwise, it was expected the absence of difference in central and peripheral fatigue between genders. The greater impairment of electromechanical delay in females than in males was a novel results for this type of prolonged running. The small sample size may have limited the capacity to distinguish between groups

Neuromuscular fatigue on locomotor and nonlocomotor muscles induced by half marathon run

This experiment investigated the fatigue induced by half-marathon run (21.1 km) on neuromuscular function of locomotor and non-locomotor muscle groups

Severe COPD Alters Muscle Fiber Conduction Velocity During Knee Extensors Fatiguing Contraction

The aim of this study was to assess the changes in muscle fiber conduction velocity (CV), as a sign of fatigue during knee extensor contraction in patients with chronic obstructive pulmonary disease (COPD) as compared with healthy controls. Eleven male patients (5 with severe and 6 with moderate COPD; age 67 +/- 5 years) and 11 age-matched healthy male controls (age 65 +/- 4 years) volunteered for the study. CV was obtained by multichannel surface electromyography (EMG) from the vastus lateralis (VL) and medialis (VM) of the quadriceps muscle during isometric, 30-second duration knee extension at 70% of maximal voluntary contraction. The decline in CV in both the VL and VM was steeper in the severe COPD patients than in healthy controls (for VL: severe COPD vs. controls -0.45 +/- 0.07%/s; p < 0.001, and for VM: severe COPD vs. controls -0.54 +/- 0.09%/s, p < 0.001). No difference in CV decline was found between the moderate COPD patients and the healthy controls. These findings suggest that severe COPD may impair muscle functions, leading to greater muscular fatigue, as expressed by CV changes. The results may be due to a greater involvement of anaerobic metabolism and a shift towards fatigable type II fibers in the muscle composition of the severe COPD patients

Lower fatigability of locomotor than non-locomotor muscles in endurance runners

Knee extensor and elbow flexor muscles have been demonstrated to have similar fatigability, i.e. time to task failure at submaximal force level, in healthy non-trained individuals. This experiment investigated if continuative endurance training can influence the fatigability of these two muscle groups in amateur runners. Surface electromyography was used to assess fatigability in twelve amateur runners. Participants were requested to sustain for 30 s the 70 % of their maximum voluntary contraction of knee extensor and elbow flexor muscles. During contractions, electromyographic signals were recorded, respectively, from vastus lateralis and biceps brachii muscles with linear array of eight electrodes. Muscle fiber conduction velocity (CV), mean power spectral frequency (MNF), and fractal dimension (FD) of electromyographic signals were calculated. During the sustained contraction vastus lateralis muscle showed smaller decrease of CV (p = 0.006), MNF (p = 0.001), and FD (p = 0.001) than biceps brachii muscle. The lower fatigability found in knee extensors than in elbow flexors suggests that the physiological adaptation promoted by the endurance training was specific to the musculature involved in the training (i.e. the lower limbs)