Title: Motoneuron excitability depending on the level of muscle stretch Aim: The aim of this thesis is to evaluate if passive muscle lenght change may influence parameters of H - reflex of soleus muscle Method: Tibial nerve stimulation in the fossa poplitea area was performed on 6 persons while passive stretching or lengthening of the muscle. Action potentials were captured on soleus muscle. Stimulation was performed in three different time periods - 4s, 2s, 1s. Each period was performed twice. First in passive muscle stretching then the passive shortening. The Hmax and Mmax values during passive muscle stretching and shortening were evaluated and compared. Results: The measurment results showed that there was a significant decrease in the Hmax values during passive muscle stretching. Mmax values were evaluated as passive muscle length change independent. Keywords: EMG, recruitment curve, H-reflex, M-wave, m.soleus, excitability

Title of diploma thesis: Tactile discrimination and excitability of alpha motoneurons Objectives: The aim of this thesis is to detect whether tactile discrimination tasks affect the excitability of the alpha motoneurons. Methods: Seven volunteers aged between 20 and 26 years participated in this study. The H reflex, (M wave) were recorded during three control and three experimental conditions. The control conditions preceded each experimental condition. By stimulating the tibialis nerve in the popliteal fossa the H reflex was elicited and its amplitude and latency measured at rest (control) and during tactile discrimination tasks (experimental). As tactile discrimination tasks, three separate tasks were chosen-tactile stimulation, escape reaction to tactile stimulation, and two-point discrimination. We used an EMG stimulator with a constant voltage output and monophasic squared pulses, with a 0,5 ms interval. The stimulation was switched on manually every 3-5 seconds. To detect the electrical potential of the soleus muscle, we used a surface EMG device, a GrassTelefactor, with galvanic isolation complying with EU standards. The parameters measured were the latency and amplitude of the H reflex and M wave during the tactile discrimination tasks and these were then compared to the values at rest. The...

Title: Recruitment curve of H-reflex in diagnostics of non-radicular syndroms Objectives: The main objective of this work is to verify the conductivity of nerve structures examination recruitment curves H-reflex and M-wave in the EMG examination in probands with non-radicular syndrome L5/S1. Methods: We tested 12 probands clinical trial diagnosed with non-radicular syndrome L5/S1. The test sample was compared with an equally large group of control probands. H-reflex of m.soleus was examined by bipolar stimulation in the fossa poplitea of tibial nerve. The results of an electromyographic examination was evaluated to asymptomatic and symptomatic side. Amplitude of H-reflex and M-wave, slope of recruitment curve, peaks of recruitment curves for the H-reflex and M-wave and the ratio Hmax / Mmax were evaluated and statistically compared. Results: Results of non-radicular syndrome L5/S1showed no significant change in the H-reflex. Due to this result we can suggests that there is no damage in nerve fibres in patients with non-radicular syndrome. Keywords: non-radicular syndrome, H-reflex, M-wave, recruitment curve

Studying the responsiveness of specific central nervous system (CNS) pathways to electrical or magnetic stimulation can provide important information regarding fatigue processes occurring as a result of ongoing muscle activity. While there are some studies assessing CNS responsiveness during sustained maximal voluntary contractions (MVCs) few papers have examined such changes during sustained submaximal contractions, particularly in muscles of the lower limbs. The location of the underlying central fatigue process can be partially determined by assessing the responsiveness to magnetic or electrical stimulation at different sites along the CNS. This has been investigated during maximal and submaximal contractions in the upper limb muscles, however changes in corticospinal responsiveness at different CNS locations has yet to be determined during fatigue of lower limb muscles. Therefore, the focus of this study was to investigate changes in corticospinal responsiveness during a sustained submaximal contraction of the triceps surae. Comparisons were made between the size of motor evoked potentials (MEPs) elicited by motor cortical stimulation and cervicomedullary motor evoked potentials (CMEPs) elicited via magnetic stimulation of the descending tracts, in order to determine the site of any change in corticospinal responsiveness. Participants maintained an isometric contraction of triceps surae at 30% of MVC for as long as possible on two occasions. Stimulation was applied either to the motor cortex or to the cervicomedullary junction every minute during a contraction until task failure. Peripheral nerve stimulation was also applied to evoke maximal M-waves (Mmax) and a superimposed twitch. Additionally, MEPs and CMEPs were evoked during brief contractions at 80, 90 and 100% MVC as a non-fatigue control. During the sustained contractions, MEP size increased significantly in both soleus (113%; SOL) and medial gastrocnemius (108%; MG) and at endurance limit matched MEP size in the pre-fatigue MVC (≈20-25% Mmax). In contrast, CMEP size increased significantly in MG (51%) but not in SOL (63%), and at endurance limit was significantly smaller than during pre-fatigue MVC (5-6% Mmax versus 11-13% Mmax). The data indicate that cortical processes contribute substantially to the increase in corticospinal responsiveness observed during sustained submaximal contraction of triceps surae. The strength of corticospinal projections and the upper-limit of motor unit recruitment may explain differences in corticospinal responsiveness between SOL and upper arm muscles. Furthermore, differences in motor unit recruitment and firing rate may explain differences in spinal responsiveness between submaximal and maximal voluntary contractions.

<p> An investigation as to the appropriateness of the wavelet transform for surface electromyography (EMG) M-wave pattern recognition is described. The M-waves are obtained by stimulating the median nerve at the wrist to activate the motor units. Surface electrodes and a graded stimulus amplitude are used. The resulting M-waves are classified using both wavelet vectors and the traditional power spectral coefficients as features sets in the pattern recognition scheme. A novel system was developed to obtain M-wave collections from subjects in the laboratory and to perform both real-time and offline analysis.</p> <p> The results obtained from the left and right thenar muscles of 4 healthy females and 2 healthy males are presented. These results are further analyzed offline to determine the effects of a changing discriminatory threshold for both wavelet and power spectral pattern recognition techniques. In addition, intra-class and inter-class Euclidean distances are shown for the set of unique M-waves derived from using the different feature sets. A time-invariant wavelet transform is implemented to improve classification by eliminating errors due to latency shifts.</p> <p> The results show that the number of unique M-waves obtained usmg wavelet features is less sensitive to a variation in discriminatory threshold. It may be concluded that a wavelet based feature set shows slight improvement in M-wave pattern classification. The time-invariant wavelet offers further accuracy.</p> / Thesis / Master of Applied Science (MASc)

Cette thèse a pour but de mettre au point un nouvel outil de rééducation neuromusculaire. Elle a pour fonction, l'amélioration de la qualité et de la durée des séances de renforcement musculaire et de réentraînement de la motricité de sujets atteints de déconditionnement musculaire. Un électromyostimulateur "intelligent" utilisant en même temps des techniques d'électromyostimulation (EMS) couplées aux analyses de l'électromyogramme (EMG) est développé et permet d'asservir en temps réel les paramètres de stimulation d'un muscle en fonction de son état de fatigue physiologique. Le contrôle ainsi effectué sur les paramètres de stimulation en fonction de la réponse musculaire électrique (onde M) offre la possibilité de stimuler un muscle en prenant en compte une information sur la réaction du muscle à l'électrostimulation / This project aims to develop a new tool for neuromuscular reeducation. Its function is to improve the quality and the duration of muscular strengthening training sessions and training of motor function for patients suffering from muscle deconditioning. A "smart" electromyostimulator using, at the same time, techniques of electrostimulation (EMS) and analysis of electromyography (EMG) allows the control in real time electrical stimulation parameters considering the physiological fatigue of the stimulated muscle. This control, performed on stimulation parameters depending on electrical response of muscles (M wave), allows the muscle stimulation taking into account the muscular reaction to the electrical stimulation

Title: Consequences of forced hypokinesia on human movement aparatus. Objectives: The aim of this study was to find out the influence of forced hypokinesia after total hip replacement on the excitability of α motoneurons. I deal with the changes of H-reflex and M-wave latencies and the changes of the recruitment curves. The results of the operated and non-operated (kontrol) lower limb were compared. Methods: Five volunteers 3 - 4 weeks after total hip replacement participated in this study. The age was 62,4 (± 3,01). The H-reflex was elicited by stimulation of tibial nerve in a poplitel fossa. The H-reflex and M-wave latencies and its recruitment curves were obtained. After that the values of the operated lower limb were compared with the non-operated one (control). The results were evaluated as case studies. The EMG device Grass Telefactor was used to detect the electrical potential of soleus muscle. The rectangular pulses of 0,5 ms duration were used for stimulation tibial nerve by Grass 88 Stimulator. Then the data were transduced by CED Power 1401 device. Results: We found out that the H-reflexes of both lower limbs were not elicited in the case study no. 2 and the H-reflex of a control lower limb was not elicited in case study no. 1. The stimulus intensities for eliciting H-reflex and M-wave...

L’objectif de ce travail était de déterminer i) l’influence du niveau de force absolue sur la durée du temps de maintien, et les altérations neuromusculaires subséquentes chez un même individu à l’issue d’un exercice réalisé à la même intensité relative, avec un ou deux membres ; ii) l’influence de la commande nerveuse sur la capacité de production de force de chacun des muscles extenseurs du genou lors de contractions unilatérales (UL) vs. bilatérales (BL); iii) l’évolution des mécanismes d’activation pendant une série de contractions sous-maximales évoquées par électromyostimulation (EMS).Les résultats de la première étude confirment que le temps limite est dépendant du niveau de force absolu pour un même individu, la durée de la contraction en UL étant 20% plus longue qu’en BL. De plus, une corrélation a été trouvée entre la force lors d’une contraction maximale volontaire (CMV) et le temps limite en UL et BL. Toutefois, d’autres mécanismes semblent être également mis en jeu, car dans un cas les mécanismes sont d’origine nerveux et musculaire (UL), alors que dans l’autre cas les mécanismes sont seulement nerveux (BL). Les résultats de la deuxième étude montrent que la force maximale développée lors d’une contraction BL est inférieure à la somme des forces des contractions UL (i.e. présence d’un déficit bilatéral). Les temps d’apparition des pics de force lors des CMV de chacune des jambes ne sont pas différents de celui de la CMV BL, mais la force développée au cours de celle-ci est inférieure à la somme des CMV de chacune des jambes durant la CMV BL, c'est-à-dire à la force maximale produite par chacune des jambes lors de la CMV BL. Néanmoins, aucune différence d’activité EMG, d’amplitude d’onde M, de doublet et de niveau d’activation n’a été observée entre les conditions UL et BL. Les résultats de la troisième étude montrent que l’estimation de la commande descendante, par la technique de la secousse surimposée, lors d’un effort sous-maximal fatigant présente des biais méthodologiques. Toutefois, l’estimation des mécanismes nerveux par les deux méthodes classiques (niveau d’activation volontaire (NAV) et ratio d’activation centrale (CAR)) reste néanmoins pertinente pendant des contractions maximales volontaires. L’ensemble de nos travaux met en évidence l’intervention de mécanismes d’origine nerveux différents entre les contractions UL et BL / The aim of this work was to determine i) the influence of the level of absolute force on the duration of the endurance time, and subsequent neuromuscular alterations in same individual at the end of an exercise performed at the same relative intensity, with one or two legs, ii) the influence of central drive on the force capacity production of the knee extensor muscles during unilateral (UL) vs. bilateral (BL) contractions, iii) activation mechanisms evolution for a serie of submaximal evoked contractions by electrostimulation (EMS). The results of the first study confirm that the endurance limit depends on the level of absolute force for the same individual, contraction duration for UL is 20% longer than for BL. In addition, a correlation was found between the maximal voluntary contraction force (MVC) and the endurance time in UL and BL. However, other mechanisms also appear to be involved, because in one case the mechanisms are nervous and muscular (UL), while in other cases the mechanisms are only nervous (BL). The results of the second study show that maximal force developed during BL contraction is less than the sum of the forces of UL contraction (i.e. a bilateral deficit). The timing of MVC peak force production during each leg of MVC are not different from that of BL MVC, but the force developed during the latter is less than the sum of MVC in both legs during the BL MVC, i.e. the maximum force produced by each leg during BL MVC. However, no difference in EMG activity, M-wave amplitude, doublet and level of activation was observed between UL and BL conditions. The results of the third study show that the estimation of the central drive, by the technique of superimposed twitch during a submaximal fatiguing effort presents methodological bias. However, estimation of neural mechanisms with both conventional methods (voluntary level activation (VAL) and central activation ratio (CAR)) remains relevant during maximal voluntary contractions. This work évidences the presence of different nervous mechanisms between UL and BL contractions