Direct and indirect lactate oxidation in trained and untrained men.

Lactate has been shown to be an important oxidative fuel. We aimed to quantify the total lactate oxidation rate (Rox) and its direct vs. indirect (glucose that is gluconeogenically derived from lactate and subsequently oxidized) components (mg·kg(-1)·min(-1)) during rest and exercise in humans. We also investigated the effects of endurance training, exercise intensity, and blood lactate concentration ([lactate]b) on direct and indirect lactate oxidation. Six untrained (UT) and six trained (T) men completed 60 min of constant load exercise at power outputs corresponding to their lactate threshold (LT). T subjects completed two additional 60-min sessions of constant load exercise at 10% below the LT workload (LT-10%), one of which included a lactate clamp (LC; LT-10%+LC). Rox was higher at LT in T [22.7 ± 2.9, 75% peak oxygen consumption (Vo2peak)] compared with UT (13.4 ± 2.5, 68% Vo2peak, P < 0.05). Increasing [lactate]b (LT-10%+LC, 67% Vo2peak) significantly increased lactate Rox (27.9 ± 3.0) compared with its corresponding LT-10% control (15.9 ± 2.2, P < 0.05). Direct and indirect Rox increased significantly from rest to exercise, and their relative partitioning remained constant in all trials but differed between T and UT: direct oxidation comprised 75% of total lactate oxidation in UT and 90% in T, suggesting the presence of training-induced adaptations. Partitioning of total carbohydrate (CHO) use showed that subjects derived one-third of CHO energy from blood lactate, and exogenous lactate infusion increased lactate oxidation significantly, causing a glycogen-sparing effect in exercising muscle

Endurance training improves oxygen uptake/demand mismatch, metabolic flexibility and recovery in patients with sickle cell disease

Patients with sickle cell disease (SCD) display lower slope coefficients of the oxygen uptake (V_O2) vs. work rate (W) relationship (delineating an O2 uptake/demand mismatch) and a poor metabolic flexibility. Because endurance training (ET) increases the microvascular network and oxidative enzymes activity including one involved in lipid oxidation, ET might improve the slope coefficient of the V_O2 vs. W curve and the metabolic flexibility of SCD patients. ET may also contribute to improve patient post-exercise cardiopulmonary and metabolic recovery. Fifteen patients with SCD performed a submaximal incremental test on a cycle ergometer before (SIT1) and after (SIT2) 8 weeks of ET. Minute ventilation, ventilation rate (VR), heart rate (HR), V_O2, CO2 production, respiratory exchange ratio, carbohydrate/lipid utilization and partitioning (including %Lipidox) and blood lactate concentration ([lactate]b) were measured during and after SIT1 and SIT2. At baseline, the slope coefficient of the V_O2 vs. W curve positively correlated with total hemoglobin, mean corpuscular hemoglobin and percentage of HbF. After training, the slope coefficient of the V_O2 vs. W curve was significantly higher and the [lactate]b increase was delayed. If patients’ energy metabolism apparently relied largely on carbohydrate sources during SIT1, %Lipidox tended to increase at low exercise intensities during SIT2, supporting a training-induced improvement of metabolic flexibility in patients with SCD. Post-exercise recovery of VR, V_E/V_CO2, HR and [lactate]b was faster after training. We concluded that ET in patients with SCD i) ameliorated the oxygen uptake/demand mismatch, ii) blunted the metabolic inflexibility, and iii) improved post-exercise cardiopulmonary and metabolic responses

Physical Exercise or Activity and Energy Balance or Metabolism in the Context of Health and Diseases

Regular long-lasting physical exercise demands a tremendous amount of metabolic energy [...

Adaptabilité de la coordination visuo-manuelle (effets de la répétitivité et d'une fatigue musculaire localisée)

De nombreuses études ont mis en évidence le caractère adaptatif de la motricité humaine. D'une part, l'organisation motrice est spécifique au contexte d'exécution. D'autre part, elle évolue avec le développement de la fatigue musculaire. Ce travail de thèse renforce ce point de vue en illustrant la capacité d'adaptation de la structure temporelle de coordination entre le regard et la main lors de l'exécution de mouvements d'atteinte. Principalement étudié pour des mouvements discrets rapides, le patron temporel de coordination visuo-manuelle est classiquement considéré comme stable et robuste. Nos données originales montrent que, dans le cadre de mouvements répétitifs rapides, le mode de coopération entre le regard et la main s'adapte finement à la taille des cibles à atteindre et évolue en situation de fatigue musculaire lorsque la précision terminale requise est élevée. Une étude complémentaire met en évidence que les stratégies de compensation sensorimotrices en situation de fatigue musculaire sont associées à des coûts neuromusculaires et cognitifs importants. Finalement, les spécialistes de l'analyse de la motricité humaine, capables d'appréhender les subtilités inhérentes aux caractères spécifique et évolutif de l'organisation motrice et des contraintes associées, ont selon nous un rôle primordial à jouer dans les démarches de prévention et de rééducation des troubles orthopédiques. Nos projets de valorisation dans ces domaines, en cours et à venir, sont présentés.Several studies have shown the adaptability of human motor control. In one sense, motor control is specific to the execution context, in another sense, it evolves with muscular fatigue. This thesis work reinforces this viewpoint by illustrating the adaptive capacity of the temporal coordination between the gaze and the hand during goal-directed movements. Principally studied during fast discrete movements, the temporal pattern of visuo-manual coordination is usually considered to be robust and stable. Our original data show that, in the context of fast repetitive movements, coordination between the gaze and the hand is fine tuned based on target size and that it evolves with muscular fatigue when the terminal accuracy requirements are high. A complementary study highlights that neuromuscular and cognitive costs are higher for a repetitive visuo-manual pointing task when muscular fatigue is present. Finally, specialists in human motor analysis, who are capable of seeing the complexity of motor organisation and the related constraints, have a role of primordial importance when it comes to prevent musculoskeletal disorders and also re-educating those who suffer from them. Our projects in these areas, in progress and to come, are presented.CHAMBERY -BU Bourget (730512101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Exacerbated in vivo metabolic changes suggestive of a spontaneous muscular vaso-occlusive crisis in exercising muscle of a sickle cell mouse

International audienceWhile sickle cell disease (SCD) is characterized by frequent vaso-occlusive crisis (VOC), no direct observation of such an event in skeletal muscle has been performed in vivo. The present study reported exacerbated in vivo metabolic changes suggestive of a spontaneous muscular VOC in exercising muscle of a sickle cell mouse. Using magnetic resonance spectroscopy of phosphorus 31, phosphocreatine and inorganic phosphate concentrations and intramuscular pH were measured throughout two standardized protocols of rest – exercise – recovery at two different intensities in ten SCD mice. Among these mice, one single mouse presented divergent responses. A statistical analysis (based on confidence intervals) revealed that this single mouse presented slower phosphocreatine resynthesis and inorganic phosphate disappearance during the post-stimulation recovery of one of the protocols, what could suggest an ischemia. This study described, for the first time in a sickle cell mouse in vivo, exacerbated metabolic changes triggered by an exercise session that would be suggestive of a live observation of a muscular VOC. However, no evidence of a direct cause-effect relationship between exercise and VOC has been put forth

Do we have to consider acidosis induced by exercise as deleterious in sickle cell disease?

International audienc

Caractéristiques structurales et fonctionnelles du muscle strié squelettique (effets de l'hémoglobine S et/ou de l'alpha-thalassémie)

De nombreuses études ont mis en évidence le caractère plastique du muscle strié squelettique en réponse à de nombreux stimuli. Ce travail de thèse s est attelé à caractériser les modifications structurales et fonctionnelles potentielles de ce tissu en présence de deux hémoglobinopathies génétiques : la drépanocytose (dans sa forme homozygote et hétérozygote), due à la production d'une hémoglobine anormale (appelée S), et/ou l alpha-thalassémie (dans sa forme hétérozygote, parfois associée à la drépanocytose), se caractérisant par une anémie microcytaire. Les analyses histologiques et biochimiques de prélèvements biopsiques du muscle vastus Iateralis témoignent d un remodelage structural et fonctionnel du muscle et notamment du réseau micro-vasculaire des sujets drépanocytaires. Une raréfaction des micro-vaisseaux, associée à une augmentation de leur diamètre et une diminution de leur tortuosité sont rapportées, adaptations qui pourraient limiter les troubles hémorhéologiques inhérents à l'hémoglobine S. Les activités des enzymes clés du métabolisme oxydatif (CS : citrate synthase et COx : cytochrome c oxydase) ont également été trouvées altérées chez les sujets porteurs de l hémoglobine S. L a-thalassémie fait elle aussi l objet d un léger remodelage micro-vasculaire marqué par une augmentation de la tortuosité des micro-vaisseaux. Enfin, l'association drépanocytose hétérozygote/a-thalassémie, connue pour atténuerles désordres hémorhéologiques et inflammatoires, n engendrerait aucune modification notable descaractéristiques structurales et fonctionnelles du tissu musculaire par rapport à une population contrôle (HbAA)Several studies have demonstrated the skeletal striated muscle plasticity in answer to differentstimuli. The aim of this thesis work was to characterize the structural and functional modifications of this particular tissue face to the sickle cell disease (in both homozygous and heterozygous forms), due to the production of an abnormal hemoglobin (called hemoglobin S), and/or the alpha thalassemia (in her heterozygous form, regularly associated with sickle cell disease). The histochemical and biochemical analysis of the vastus Iateralis biopsy showed evidence for 3 significant structural and functional remodeling of the sickle cell subjects muscle and most particularly of the microvasculature. A reduced capillary density, associated with enlarged microvessels and lower tortuosity are reported, that may possibly limit the hemorheological disorders linked to hemoglobin S. The main oxidative enzymes activities (CS: citrate synthase and COx: cytochrome c oxydase) were also altered in sickle cell subjects. Remodeling of the microvascular network occurs to a lesser extent in a-thalassemia, with an increase of the microvessels tortuosity. Finally, the association of the sickle cell heterozygous form with a-thalassemia, known to reduced hemorheological and inflammatory disorders, does not seem to modify muscle characteristics in comparison to a control population with normal hemoglobinST ETIENNE-Bib. électronique (422189901) / SudocSudocFranceF

Physiological correlates of performance. Case study of a world-class lower

This report describes the changes in physiological capacity of a heavy-weight rower who obtained seven medals in World Championships and Olympic Games. The investigation was carried out over the last 6 years of the rower's international competition career in comparison with peer champions, and the following 4 years. Over the first period, maximal oxygen uptake (V O2 max) remained above 6 l min-1 which is an outstanding value. The training load measured over the last 18 months of the period increased from 119 to 142 km wk-1 of rowing. Four years after the international competition period, V O2 max had only declined by 3.6% although the training load had declined by 35%. These data suggest that the ability of this rower to compete at top level for years was related to ability to maintain an outstanding. VO2 max. Gross efficiency and ability to rely on anaerobic glycolysis did not emerge as relevant factors. Keywords Maximal oxygen uptake ; Peak power ; Blood lactate concentration ; Training load