L'oxygénation cérébrale mesurée par spectroscopie dans le proche infrarouge comme témoin des ajustements de la commande motrice centrale

Exploration des aspects métaboliques de la fatigue musculaire in vivo : la spectroscopie dans le proche infrarouge (NIRS), une technique adaptée pour l'enregistrement de paramètres hémodynamiques localisés, et notamment l'oxygénation tissulaire de façon dynamique à l'exercic

L'état énergétique du muscle fatigué vu par la résonance magnétique nucléaire

Quantification des processus métaboliques oxydatifs et glycolytiques au niveau cellulaire au cours de l'exercice et en récupération, au moyen de la spectroscopie par résonance magnétique du phosphore-31, qui permet la mesure des concentrations de composés impliqués dans le métabolisme musculaire tels que l'ATP, la phosphocréatine et le phosphate inorganiqu

Basal power reconstruction during cycling using a robust discrete-time PI observer

International audienceThe basal metabolic rate characterizes the energy consumption of the human body at rest. It can be estimated by using respiratory gas exchange analyzers and indirect calorimetry. During cycling this value could vary due to several adaptation processes such as an increase in breathing and blood circulation, controlling body temperature, among others. In this paper we propose to reconstruct the instantaneous value of this basal metabolic rate, referred here as basal power (measured in Watts), by using a robust discrete-time proportional integral (PI) observer. The observer design is based on a solution of linear matrix inequalities and uses an uncertain linear parameter varying model of the gas exchange dynamics. The proposed methodology allows the reconstruction of the basal power while making the respiratory gas exchange estimation robust to bounded uncertainties and disturbances. The PI observer has been validated in simulation

Electrical stimulation for testing neuromuscular function: from sport to pathology

International audienceThe use of electrical stimulation (ES) can contribute to our knowledge of how our neuromuscular system can adapt to physical stress or unloading. Although it has been recently challenged, the standard technique used to explore central modiWcations is the twitch interpolated method which consists in superimposing single twitches or high-frequency doublets on a maximal voluntary contraction (MVC) and to compare the superimposed response to the potentiated response obtained from the relaxed muscle. Alternative methods consist in (1) superimposing a train of stimuli (central activation ratio), (2) comparing the MVC response to the force evoked by a high-frequency tetanus or (3) examining the change in maximal EMG response during voluntary contractions, if this variable is normalized to the maximal M wave, i.e. EMG response to a single stimulus. ES is less used to examine supraspinal factors but it is useful for investigating changes at the spinal level, either by using H reXexes, F waves or cervicomedullary motor-evoked potentials. Peripheral changes can be examined with ES, usually by stimulating the muscle in the relaxed state. Neuromuscular propagation of action potentials on the sarcolemma (M wave, high-frequency fatigue), excitation–contraction coupling (e.g. low-frequency fatigue) and intrinsic force (high-frequency stimulation at supra-maximal intensity) can all be used to non-invasively explore muscular function with ES. As for all indirect methods, there are limitations and these are discussed in this review. Finally, (1) ES as a method to measure respiratory muscle function and (2) the comparison between electrical and magnetic stimulation will also be considered

Basal power reconstruction during cycling using a robust discrete-time PI observer

International audienceThe basal metabolic rate characterizes the energy consumption of the human body at rest. It can be estimated by using respiratory gas exchange analyzers and indirect calorimetry. During cycling this value could vary due to several adaptation processes such as an increase in breathing and blood circulation, controlling body temperature, among others. In this paper we propose to reconstruct the instantaneous value of this basal metabolic rate, referred here as basal power (measured in Watts), by using a robust discrete-time proportional integral (PI) observer. The observer design is based on a solution of linear matrix inequalities and uses an uncertain linear parameter varying model of the gas exchange dynamics. The proposed methodology allows the reconstruction of the basal power while making the respiratory gas exchange estimation robust to bounded uncertainties and disturbances. The PI observer has been validated in simulation

Procédé, dispositif, programme produit d’ordinateur et support d’enregistrement comportant ledit programme pour le contrôle d’un état métabolique

Provided is a method for monitoring the metabolic state ofan individual in the context of exercise during which the individual delivers mechanical power, said metabolic state being represented by a physiological index, the method being implemented by a device (400) comprising a processor (401) executing software code (404) leading to the implementa- ion of the steps of the method by said device (400), said method compris- ing: (a) computing (301) an error in the index with respect to a reference value (125) of the index at a time k; (b) applying (302), to said error, a metabolic law, lo obtain a power setting to be respected to decrease the error; (c) obtaining (303) a prediction of the variation in the index for a plurality of values of a correction ot be applied ni the context of determina- tion of the power setting; (d) determining (304) one among the plurality of values of the correction depending on at least one objective to be achieved ni the long term; (e) applying (305) the correction value chosen (136) to adjust the process of obtaining the power setting; D() generating (306) a signal representative of said power sctting. Adevicc alowing implemen- tation, a computer program product and a storage medium containing such a program are also provided.Il est proposé un procédé de contrôle de l'état métabolique d'une personne dans le cadre d'un exercice au cours duquel la personne fournit une puissance mécanique, ledit étatmétabolique étant représenté par un indice physiologique, le procédé étant mis en œuvre par un dispositif (400) comportant un processeur (401) exécutant du code logiciel (404) conduisant à la mise en œuvre des étapes du procédé par ledit dispositif (400), ledit procédé comportant :(a) le calcul (301) d'une erreur sur l'indice par rapport à une valeur de référence (125)de l'indice à un temps k ;(b) l'application (302) à ladite erreur d'une loi métabolique pour l'obtention d'uneconsigne de la puissance à respecter pour réduire l'erreur ;(c) l'obtention (303) d'une prédiction de l'évolution de l'indice pour une pluralité de valeurs d'une correction à appliquer dans le cadre de la détermination de la consigne de la puissance ;(d) la détermination (304) de l'une parmi la pluralité de valeurs de la correction en fonction d'au moins un objectif à atteindre dans la durée ;(e) l'application (305) de la valeur de correction choisie (136) pour ajuster le processus d'obtention de la consigne de la puissance ;(f) la génération (306) d'un signal représentatif de ladite consigne de puissance.Sont également proposés un dispositif de mise en œuvre, ainsi qu'un produit programme d'ordinateur et un support d'enregistrement comportant un tel programme

Estimation of carbon-dioxide production during cycling by using a set-membership observer

International audienceThis paper presents a set-membership observer for the estimation of carbon dioxide production during cycling. The observer uses measurements of oxygen consumption and power at pedal level together with a discrete-time linear model of gas exchange dynamics. The real process is assumed to be disturbed by unknown but bounded disturbances. The proposed observer provides a deterministic interval which contains the real state. Since the excess of carbon dioxide production is linked to the overtake of the anaerobic threshold, the observer can be applied to predict the physiological state of the cyclist by using a reduced number of gas exchange sensors. The methodology is illustrated and validated using experimental data

Estimation of carbon-dioxide production during cycling by using a set-membership observer

International audienceThis paper presents a set-membership observer for the estimation of carbon dioxide production during cycling. The observer uses measurements of oxygen consumption and power at pedal level together with a discrete-time linear model of gas exchange dynamics. The real process is assumed to be disturbed by unknown but bounded disturbances. The proposed observer provides a deterministic interval which contains the real state. Since the excess of carbon dioxide production is linked to the overtake of the anaerobic threshold, the observer can be applied to predict the physiological state of the cyclist by using a reduced number of gas exchange sensors. The methodology is illustrated and validated using experimental data