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Papers by stephane delliaux

Research paper thumbnail of Commentaries on Viewpoint: The two-hour marathon: Who and when?

Journal of Applied Physiology, 2011

TO THE EDITOR: It was with great interest that we read the Journal of Applied Physiology Viewpoin... more TO THE EDITOR: It was with great interest that we read the Journal of Applied Physiology Viewpoint on the 2-h marathon barrier (3). We would argue that, alongside having a superlative V O 2max , lactate threshold, and running economy, it will be required for this athlete to have an individualized and aggressive fueling strategy coupled with a predisposition for high exogenous CHO oxidation (CHO exog), without a history of GI distress. It is clear that supplemented carbohydrate (CHO) improves prolonged endurance performance (Ͼ90 min) compared with water (2). Furthermore, recent evidence has demonstrated a positive dose-response relationship between supplemented CHO, CHO exog , and endurance performance; where 60 g CHO/h outperformed either 15 or 30 g CHO/h (5). The maximal CHO exog with single CHO sources appears to be ϳ1 g/min due to limitations of the intestinal transporters (1). However, despite any individual differences in CHO exog or history of GI distress (4), CHO exog is not dependent on body weight (BW), as a recent analysis has shown no relationship between BW and CHO exog (1). Accordingly, a 56-kg runner is able to oxidize ϳ20% more per kg BW compared with a 70-kg runner with a given CHO exog rate of ϳ1 g/min (1.07 vs.0.86 g CHO•h Ϫ1 •kg BW Ϫ1). Therefore, there appears to be a distinct CHO exog advantage for lighter marathon runners compared with heavier. Thus the future 2-h marathon runner will feature a low BW, both for improved thermoregulation, but also optimal CHO exog per kg BW. All of these elements will need to be possessed by the first athlete to break the 2-h marathon barrier.

Research paper thumbnail of moderate muscle activation during dynamic exercise Human cardiovascular and humoral responses to

Research paper thumbnail of exercisepositive pressure at rest and during dynamic Effects of posture on cardiovascular responses to lower

Research paper thumbnail of lower body negative pressure and head-up tilt Comparison of cardiovascular responses between

Research paper thumbnail of La réhabilitation par l’effort modifie la production des cytokines induites par l’exercice

Revue des Maladies Respiratoires, 2017

A58 21 e Congrès de pneumologie de langue française-Marseille, 27-29 janvier 2017 Objectifs Déter... more A58 21 e Congrès de pneumologie de langue française-Marseille, 27-29 janvier 2017 Objectifs Déterminer la corrélation entre le taux de CRP au cours des EABPCO et la sévérité de la maladie. Méthodes Étude rétrospective portant sur les dossiers des patients porteurs de BPCO hospitalisés à notre service entre janvier 1990 et décembre 2014. Nous avons réparti notre population en 2 groupes : G1 : patients avec CRP moyenne au cours des EA sévère de BPCO < 50 mg/L (238 patients), G2 : CRP ≥ 50 mg/L (350 patients). Résultats Au total, 1119 patients BPCO ont été hospitalisés durant cette période (âge moyen = 67 ans). La CRP était faite dans 53 % des cas (588 patients). Il n'y avait pas de différence concernant l'âge, le genre, l'intensité de l'intoxication tabagique, les données spirométriques, nombre d'EA/an, la durée d'hospitalisation et le délai de la prochaine EA entre les 2 groupes. Le G2 est caractérisé par une PaO2 significativement plus basse au cours des EA sévères de BPCO (G1 : 69,4 vs. G2 : 67,7 mmHg, p < 0,001), une SatO2 plus basse (93 % vs 92 % ; p < 0,001) et une hyperleucocytose plus élevée (10,629, 14,041/mm 3 ; p < 0,001). Les EA sévères du G2 sont souvent anthonisen type 1 (G1 : 62 %, G2 : 85 % ; p < 0,001) avec plus d'acidose respiratoire (13,6, 20,5 % ; p = 0,022) et une durée de corticothérapie systémique plus prolongée (12,6, 14j ; p = 0,03). Le G2 est caractérisé par un recours plus fréquent à la ventilation mécanique (0,13 vs 0,26/patient/an ; p = 0,02) et une médiane de survie réduite (132 vs 96 mois ; Log Rank et Breslow < 0,001). Conclusion L'élévation de la CRP au cours des EA sévères de BPCO doit être considérée comme un facteur prédictif péjoratif dans le cours évolutif de la maladie. Déclaration de liens d'intérêts Les auteurs déclarent ne pas avoir de liens d'intérêts.

Research paper thumbnail of Cardiovascular responses to forearm muscle metaboreflex activation during hypercapnia in humans

American journal of physiology. Regulatory, integrative and comparative physiology, Jan 22, 2015

We characterized the cardiovascular responses to forearm muscle metaboreflex activation during hy... more We characterized the cardiovascular responses to forearm muscle metaboreflex activation during hypercapnia. Ten healthy males participated under three experimental conditions: 1) hypercapnia (HCA, PetCO2: +10mmHg) induced by inhalation of a CO2-enriched gas mixture; 2) muscle metaboreflex activation (MMA) induced by 5 min of local circulatory occlusion following 1 min of 50% MVC isometric handgrip under normocapnia; and 3) HCA+MMA combination. We measured mean arterial pressure (MAP, finger photoplethysmography), heart rate (HR, electrocardiography) and cardiac output (CO, Doppler ultrasound); calculated stroke volume (SV) and total peripheral resistance (TPR); and evaluated myocardial oxygen consumption (MVO2, double product) and cardiac work (CW, triple product). MAP increased in the three experimental conditions (p<0.001) but HCA+MMA led to the highest (p<0.01) MAP (110±3 mmHg), CO (7.3±0.4 l/min) and HR (77±4 bpm). Moreover, HCA+MMA increased SV (85±4 vs. 98±4 ml, p<0.0...

Research paper thumbnail of Cardiopulmonary Response to Exercise in COPD and Overweight Patients: Relationship between Unloaded Cycling and Maximal Oxygen Uptake Profiles

BioMed Research International, 2015

Cardiopulmonary response to unloaded cycling may be related to higher workloads. This was assesse... more Cardiopulmonary response to unloaded cycling may be related to higher workloads. This was assessed in male subjects: 18 healthy sedentary subjects (controls), 14 hypoxemic patients with chronic obstructive pulmonary disease (COPD), and 31 overweight individuals (twelve were hypoxemic). They underwent an incremental exercise up to the maximal oxygen uptake (VO2max), preceded by a 2 min unloaded cycling period. Oxygen uptake (VO2), heart rate (HR), minute ventilation (VE), and respiratory frequency (fR) were averaged every 10 s. At the end of unloaded cycling period, HR increase was significantly accentuated in COPD and hypoxemic overweight subjects (resp.,+14±2and+13±1.5 min−1, compared to+7.5±1.5 min−1in normoxemic overweight subjects and+8±1.8 min−1in controls). The fR increase was accentuated in all overweight subjects (hypoxemic:+4.5±0.8; normoxemic:+3.9±0.7 min−1) compared to controls (+2.5±0.8 min−1) and COPDs (+2.0±0.7 min−1). The plateau VE increase during unloaded cycling wa...

Research paper thumbnail of Fin swimming improves respiratory gas exchange

International journal of sports medicine, 2009

Data in the literature suggest that compared to dry-land exercise fin swimming might delay the ac... more Data in the literature suggest that compared to dry-land exercise fin swimming might delay the activation of the anaerobic metabolism. To verify this hypothesis, we explored indirect indices such as the oxygen pulse (VO(2)/HR), carbon dioxide production (VCO(2)), and ventilatory threshold, comparing fin swimming exercise to dry-land cycling. Thirteen participants, experienced or inexperienced in fin swimming, completed an incremental fin swimming exercise and a maximal exercise on a cycloergometer with breath-by-breath measurements of heart rate (HR), ventilation (VE), tidal volume (VT), VO(2), VCO(2), and VO(2)/HR and determination of the ventilatory threshold and maximal oxygen uptake (VO(2)max). Compared to dry-land cycling exercise, fin swimming resulted in elevated or absent ventilatory threshold. Although VO(2)max did not differ in either condition, in fin swimming the maximal HR value was lower (-18%, p=0.0072), maximal VO(2)/HR higher (+20%, p=0.0325), and maximal VCO(2) low...

Research paper thumbnail of The oxidative stress in response to routine incremental cycling exercise in healthy sedentary subjects

Respiratory Physiology & Neurobiology, 2004

The kinetics of blood markers of the oxidative stress during and after an incremental exercise un... more The kinetics of blood markers of the oxidative stress during and after an incremental exercise until the maximal performances is not documented in healthy sedentary subjects. We studied subjects of both sexes cycling on an ergometer until or near the V O 2 max measurement, and we measured during exercise and a 30-min recovery period the plasma concentration of thiobarbituric acid reactive substances (TBARS) which explored the production of reactive oxygen species (ROS) and two antioxidants (plasma reduced ascorbic acid (RAA) and erythrocyte reduced glutathione (GSH)). Despite we noted inter-individual differences in the instants of maximal variations of TBARS, GSH, and RAA, they were all measured within the first 20 min of the post-exercise recovery period, and at the 30th min of recovery, the three ROS blood markers tended to recover their pre-exercise levels. The maximal TBARS increase was positively correlated with V O 2 max and negatively correlated with the magnitude of RAA consumption. Our results indicate the existence of an early post-exercise oxidative stress in healthy sedentary volunteers. They also show that the ROS production is proportional to the maximal aerobic power and inversely related to the consumption of plasma antioxidants.

Research paper thumbnail of Muscle Metaboreflex Functions During Dynamic Exercise in Humans

Medicine & Science in Sports & Exercise, 2010

for VO2p resulted in the [HHb]/VO2 displaying a transient "overshoot" relative to the subsequent ... more for VO2p resulted in the [HHb]/VO2 displaying a transient "overshoot" relative to the subsequent steady state level. That "overshoot" was progressively reduced as tauVO2 became smaller with a correlation between [HHb]/VO2 and tauVO2p of 0.91. CONCLUSION: When tauVO2p is greater than ~20s, the rate of adjustment of phase 2 VO2p (muscle VO2) appears to be mainly constrained by the matching of local O2 delivery to muscle VO2 (i.e., microvascular blood flow distribution). In those with a shorter tauVO2 there is a reduced "overshoot" in the [HHb]/VO2 as represented by a lower [HHb]/VO2 ratio. These data experimentally support the idea that groups with progressively slower VO2 kinetics are O2 availability dependent, requiring a progressively greater O2 extraction during the on-transient of exercise.

Research paper thumbnail of Hypercapnic Chemoreflex And Muscle Metaboreflex Interactions: Effects on Heart

Medicine & Science in Sports & Exercise, 2010

Research paper thumbnail of Chronic fatigue syndrome: acute infection and history of physical activity affect resting levels and response to exercise of plasma oxidant/antioxidant status and heat shock proteins

Journal of Internal Medicine, 2012

Chronic fatigue syndrome: acute infection and history of physical activity affect resting levels ... more Chronic fatigue syndrome: acute infection and history of physical activity affect resting levels and response to exercise of plasma oxidant ⁄ antioxidant status and heat shock proteins.

Research paper thumbnail of Statins alter oxidant-antioxidant status and lower exercise-induced oxidative stress

Int. Journal of Clinical Pharmacology and Therapeutics, 2007

Data on effects of statins on resting oxidant-antioxidant status are contradictory and no study h... more Data on effects of statins on resting oxidant-antioxidant status are contradictory and no study has been published on the effects of statins on exercise-induced oxidative stress. We carried out a 6-month longitudinal study in 10 dyslipidemic patients receiving 10 mg/day atorvastatin and 13 healthy sedentary subjects. Thiobarbituric acid reactive substances (TBARS) and reduced ascorbic acid (RAA) were measured in plasma at rest and every 5 minutes after submaximal isometric thumb adduction and handgrip sustained until exhaustion. At inclusion, resting TBARS and RAA levels in controls and patients did not differ and exercise increased TBARS and decreased RAA. Atorvastatin reduced resting TBARS and RAA levels in a time-dependent but lipid-independent manner. The main effect was a post-exercise increase in TBARS, without affecting the post-exercise RAA levels. The reduction in oxidative stress occurred earlier in oxidative muscles involved in thumb adduction. In conclusion, atorvastatin lowers resting oxidant-antioxidant activity: exercise-induced oxidative stress occurs mainly in muscles having a high oxidative capacity.

Research paper thumbnail of The changes in neuromuscular excitability with normobaric hyperoxia in humans

Experimental Physiology, 2009

Based on previous observations in hyperbaric hyperoxia, we hypothesized that normobaric hyperoxia... more Based on previous observations in hyperbaric hyperoxia, we hypothesized that normobaric hyperoxia, often used during general anaesthesia and resuscitation, might also induce a neuromuscular excitability. In healthy volunteers, we studied the consequences of a 50 min period of pure oxygen breathing on the neuromuscular conduction time (CT), the amplitude of the compound evoked muscle potential (M-wave), the latency and amplitude of the Hoffman reflex (H reflex) and the electromyographic tonic vibratory response (TVR) of the flexor digitorum superficialis muscle to explore the proprioceptive reflex loop. Hyperoxia-induced oxidative stress was measured by the changes in blood markers of lipid peroxidation (thiobarbituric acid reactive substances, TBARS) and antioxidant response (reduced ascorbic acid, RAA). During hyperoxia, the M-wave amplitude increased, both CT and H reflex latency were shortened, and the H reflex amplitude increased. By contrast, TVR significantly decreased. Concomitantly, an oxidative stress was assessed by increased TBARS and decreased RAA levels. This study shows the existence of dual effects of hyperoxia, which facilitates the muscle membrane excitability, nerve conduction and spinal reflexes, but reduces the gain of the proprioceptive reflex loop. The activation of the group IV muscle afferents by hyperoxia and the resulting oxidative stress might explain the TVR depression.

Research paper thumbnail of Accuracy of the double indicator method for measurement of extravascular lung water depends on the type of acute lung injury*

Critical Care Medicine, 2004

The double indicator method is sensitive to alterations in the distribution of pulmonary blood fl... more The double indicator method is sensitive to alterations in the distribution of pulmonary blood flow. This distribution is influenced by the type of lung injury. The aim of this study was to compare measurements of lung water by the double indicator method with measurements obtained by gravimetry in a direct lung injury model induced by tracheal instillation of hydrochloric acid and in an indirect lung injury model induced by the intravenous injection of oleic acid. Prospective, randomized laboratory study. Animal research laboratory. Forty-two female pigs (28+/-3 kg). Pigs were anesthetized and ventilated and were allocated into three groups: control (n = 6), hydrochloric acid (4 mL/kg intratracheally, n = 24), or oleic acid (0.1 mL/kg intravenously, n = 12). Hydrochloric acid instillation or oleic acid injection resulted in a similar hypoxemia and induced a two- to three-fold increase in extravascular lung water (EVLW) by gravimetry (EVLWG) at 3 hrs compared with controls. In the oleic acid group, there was a significant correlation between EVLWG and EVLW by double indicator method (EVLWDI; r =.88, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;.0001). The bias for EVLWDI - EVLWG measurements was -5.2 mL/kg (95% confidence interval, -5.7 to -4.7 mL/kg) with 95% limits of agreement of -7 to -3.4 mL/kg. In the hydrochloric acid group, there was no significant correlation between EVLWDI and EVLWG values, and the double indicator method failed to detect pulmonary edema in 65% of the animals (EVLWDI &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;8 mL/kg). The bias was -7.9 mL/kg (95% confidence interval, -9.3 to -6.5 mL/kg) with 95% limits of agreement of -14.4 to -1.4 mL/kg. The double indicator method is useful for evaluation of pulmonary edema in indirect lung injury, as induced by oleic acid, but produces misleading values in direct lung injury, as produced by hydrochloric instillation.

Research paper thumbnail of Effect of voluntary hypocapnic hyperventilation on cutaneous circulation in resting heated humans

American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2012

Hypocapnia attenuates the sweat response normally seen in hyperthermic resting subjects, but its ... more Hypocapnia attenuates the sweat response normally seen in hyperthermic resting subjects, but its effect on the blood flow response in their nonglabrous skin under the same hyperthermic conditions remains unclear. In the present study, we investigated whether hypocapnia induced by voluntary hyperventilation affects the blood flow response to heat stress in the nonglabrous skin of resting humans. Nine healthy male subjects were passively heated using legs-only hot water immersion and a water-perfused suit, which caused esophageal temperature (Tes) to increase by as much as 1.0°C. During normothermia and at +0.6°C Tes and +1.0°C Tes, the subjects performed two voluntary 7-min hyperventilation (minute ventilation = 40 l/min) trials (hypocapnic and eucapnic) in random order. End-tidal CO2 pressure was reduced by 23–25 torr during hypocapnic hyperventilation, but it was maintained at the spontaneous breathing level during eucapnic hyperventilation. Cutaneous blood flow was evaluated as th...

Research paper thumbnail of Evaluation of muscle metaboreflex function through graded reduction in forearm blood flow during rhythmic handgrip exercise in humans

American Journal of Physiology-Heart and Circulatory Physiology, 2011

Hypoperfusion of active skeletal muscle elicits a reflex pressor response termed the muscle metab... more Hypoperfusion of active skeletal muscle elicits a reflex pressor response termed the muscle metaboreflex. Our aim was to determine the muscle metaboreflex threshold and gain in humans by creating an open-loop relationship between active muscle blood flow and hemodynamic responses during a rhythmic handgrip exercise. Eleven healthy subjects performed the exercise at 5 or 15% of maximal voluntary contraction (MVC) in random order. During the exercise, forearm blood flow (FBF), which was continuously measured using Doppler ultrasound, was reduced in five steps by manipulating the inner pressure of an occlusion cuff on the upper arm. The FBF at each level was maintained for 3 min. The initial reductions in FBF elicited no hemodynamic changes, but once FBF fell below a threshold, mean arterial blood pressure (MAP) and heart rate (HR) increased and total vascular conductance (TVC) decreased in a linear manner. The threshold FBF during the 15% MVC trial was significantly higher than during...

Research paper thumbnail of Commentaries on Viewpoint: The two-hour marathon: Who and when?

Journal of Applied Physiology, 2011

TO THE EDITOR: It was with great interest that we read the Journal of Applied Physiology Viewpoin... more TO THE EDITOR: It was with great interest that we read the Journal of Applied Physiology Viewpoint on the 2-h marathon barrier (3). We would argue that, alongside having a superlative V O 2max , lactate threshold, and running economy, it will be required for this athlete to have an individualized and aggressive fueling strategy coupled with a predisposition for high exogenous CHO oxidation (CHO exog), without a history of GI distress. It is clear that supplemented carbohydrate (CHO) improves prolonged endurance performance (Ͼ90 min) compared with water (2). Furthermore, recent evidence has demonstrated a positive dose-response relationship between supplemented CHO, CHO exog , and endurance performance; where 60 g CHO/h outperformed either 15 or 30 g CHO/h (5). The maximal CHO exog with single CHO sources appears to be ϳ1 g/min due to limitations of the intestinal transporters (1). However, despite any individual differences in CHO exog or history of GI distress (4), CHO exog is not dependent on body weight (BW), as a recent analysis has shown no relationship between BW and CHO exog (1). Accordingly, a 56-kg runner is able to oxidize ϳ20% more per kg BW compared with a 70-kg runner with a given CHO exog rate of ϳ1 g/min (1.07 vs.0.86 g CHO•h Ϫ1 •kg BW Ϫ1). Therefore, there appears to be a distinct CHO exog advantage for lighter marathon runners compared with heavier. Thus the future 2-h marathon runner will feature a low BW, both for improved thermoregulation, but also optimal CHO exog per kg BW. All of these elements will need to be possessed by the first athlete to break the 2-h marathon barrier.

Research paper thumbnail of moderate muscle activation during dynamic exercise Human cardiovascular and humoral responses to

Research paper thumbnail of exercisepositive pressure at rest and during dynamic Effects of posture on cardiovascular responses to lower

Research paper thumbnail of lower body negative pressure and head-up tilt Comparison of cardiovascular responses between

Research paper thumbnail of La réhabilitation par l’effort modifie la production des cytokines induites par l’exercice

Revue des Maladies Respiratoires, 2017

A58 21 e Congrès de pneumologie de langue française-Marseille, 27-29 janvier 2017 Objectifs Déter... more A58 21 e Congrès de pneumologie de langue française-Marseille, 27-29 janvier 2017 Objectifs Déterminer la corrélation entre le taux de CRP au cours des EABPCO et la sévérité de la maladie. Méthodes Étude rétrospective portant sur les dossiers des patients porteurs de BPCO hospitalisés à notre service entre janvier 1990 et décembre 2014. Nous avons réparti notre population en 2 groupes : G1 : patients avec CRP moyenne au cours des EA sévère de BPCO < 50 mg/L (238 patients), G2 : CRP ≥ 50 mg/L (350 patients). Résultats Au total, 1119 patients BPCO ont été hospitalisés durant cette période (âge moyen = 67 ans). La CRP était faite dans 53 % des cas (588 patients). Il n'y avait pas de différence concernant l'âge, le genre, l'intensité de l'intoxication tabagique, les données spirométriques, nombre d'EA/an, la durée d'hospitalisation et le délai de la prochaine EA entre les 2 groupes. Le G2 est caractérisé par une PaO2 significativement plus basse au cours des EA sévères de BPCO (G1 : 69,4 vs. G2 : 67,7 mmHg, p < 0,001), une SatO2 plus basse (93 % vs 92 % ; p < 0,001) et une hyperleucocytose plus élevée (10,629, 14,041/mm 3 ; p < 0,001). Les EA sévères du G2 sont souvent anthonisen type 1 (G1 : 62 %, G2 : 85 % ; p < 0,001) avec plus d'acidose respiratoire (13,6, 20,5 % ; p = 0,022) et une durée de corticothérapie systémique plus prolongée (12,6, 14j ; p = 0,03). Le G2 est caractérisé par un recours plus fréquent à la ventilation mécanique (0,13 vs 0,26/patient/an ; p = 0,02) et une médiane de survie réduite (132 vs 96 mois ; Log Rank et Breslow < 0,001). Conclusion L'élévation de la CRP au cours des EA sévères de BPCO doit être considérée comme un facteur prédictif péjoratif dans le cours évolutif de la maladie. Déclaration de liens d'intérêts Les auteurs déclarent ne pas avoir de liens d'intérêts.

Research paper thumbnail of Cardiovascular responses to forearm muscle metaboreflex activation during hypercapnia in humans

American journal of physiology. Regulatory, integrative and comparative physiology, Jan 22, 2015

We characterized the cardiovascular responses to forearm muscle metaboreflex activation during hy... more We characterized the cardiovascular responses to forearm muscle metaboreflex activation during hypercapnia. Ten healthy males participated under three experimental conditions: 1) hypercapnia (HCA, PetCO2: +10mmHg) induced by inhalation of a CO2-enriched gas mixture; 2) muscle metaboreflex activation (MMA) induced by 5 min of local circulatory occlusion following 1 min of 50% MVC isometric handgrip under normocapnia; and 3) HCA+MMA combination. We measured mean arterial pressure (MAP, finger photoplethysmography), heart rate (HR, electrocardiography) and cardiac output (CO, Doppler ultrasound); calculated stroke volume (SV) and total peripheral resistance (TPR); and evaluated myocardial oxygen consumption (MVO2, double product) and cardiac work (CW, triple product). MAP increased in the three experimental conditions (p<0.001) but HCA+MMA led to the highest (p<0.01) MAP (110±3 mmHg), CO (7.3±0.4 l/min) and HR (77±4 bpm). Moreover, HCA+MMA increased SV (85±4 vs. 98±4 ml, p<0.0...

Research paper thumbnail of Cardiopulmonary Response to Exercise in COPD and Overweight Patients: Relationship between Unloaded Cycling and Maximal Oxygen Uptake Profiles

BioMed Research International, 2015

Cardiopulmonary response to unloaded cycling may be related to higher workloads. This was assesse... more Cardiopulmonary response to unloaded cycling may be related to higher workloads. This was assessed in male subjects: 18 healthy sedentary subjects (controls), 14 hypoxemic patients with chronic obstructive pulmonary disease (COPD), and 31 overweight individuals (twelve were hypoxemic). They underwent an incremental exercise up to the maximal oxygen uptake (VO2max), preceded by a 2 min unloaded cycling period. Oxygen uptake (VO2), heart rate (HR), minute ventilation (VE), and respiratory frequency (fR) were averaged every 10 s. At the end of unloaded cycling period, HR increase was significantly accentuated in COPD and hypoxemic overweight subjects (resp.,+14±2and+13±1.5 min−1, compared to+7.5±1.5 min−1in normoxemic overweight subjects and+8±1.8 min−1in controls). The fR increase was accentuated in all overweight subjects (hypoxemic:+4.5±0.8; normoxemic:+3.9±0.7 min−1) compared to controls (+2.5±0.8 min−1) and COPDs (+2.0±0.7 min−1). The plateau VE increase during unloaded cycling wa...

Research paper thumbnail of Fin swimming improves respiratory gas exchange

International journal of sports medicine, 2009

Data in the literature suggest that compared to dry-land exercise fin swimming might delay the ac... more Data in the literature suggest that compared to dry-land exercise fin swimming might delay the activation of the anaerobic metabolism. To verify this hypothesis, we explored indirect indices such as the oxygen pulse (VO(2)/HR), carbon dioxide production (VCO(2)), and ventilatory threshold, comparing fin swimming exercise to dry-land cycling. Thirteen participants, experienced or inexperienced in fin swimming, completed an incremental fin swimming exercise and a maximal exercise on a cycloergometer with breath-by-breath measurements of heart rate (HR), ventilation (VE), tidal volume (VT), VO(2), VCO(2), and VO(2)/HR and determination of the ventilatory threshold and maximal oxygen uptake (VO(2)max). Compared to dry-land cycling exercise, fin swimming resulted in elevated or absent ventilatory threshold. Although VO(2)max did not differ in either condition, in fin swimming the maximal HR value was lower (-18%, p=0.0072), maximal VO(2)/HR higher (+20%, p=0.0325), and maximal VCO(2) low...

Research paper thumbnail of The oxidative stress in response to routine incremental cycling exercise in healthy sedentary subjects

Respiratory Physiology & Neurobiology, 2004

The kinetics of blood markers of the oxidative stress during and after an incremental exercise un... more The kinetics of blood markers of the oxidative stress during and after an incremental exercise until the maximal performances is not documented in healthy sedentary subjects. We studied subjects of both sexes cycling on an ergometer until or near the V O 2 max measurement, and we measured during exercise and a 30-min recovery period the plasma concentration of thiobarbituric acid reactive substances (TBARS) which explored the production of reactive oxygen species (ROS) and two antioxidants (plasma reduced ascorbic acid (RAA) and erythrocyte reduced glutathione (GSH)). Despite we noted inter-individual differences in the instants of maximal variations of TBARS, GSH, and RAA, they were all measured within the first 20 min of the post-exercise recovery period, and at the 30th min of recovery, the three ROS blood markers tended to recover their pre-exercise levels. The maximal TBARS increase was positively correlated with V O 2 max and negatively correlated with the magnitude of RAA consumption. Our results indicate the existence of an early post-exercise oxidative stress in healthy sedentary volunteers. They also show that the ROS production is proportional to the maximal aerobic power and inversely related to the consumption of plasma antioxidants.

Research paper thumbnail of Muscle Metaboreflex Functions During Dynamic Exercise in Humans

Medicine & Science in Sports & Exercise, 2010

for VO2p resulted in the [HHb]/VO2 displaying a transient "overshoot" relative to the subsequent ... more for VO2p resulted in the [HHb]/VO2 displaying a transient "overshoot" relative to the subsequent steady state level. That "overshoot" was progressively reduced as tauVO2 became smaller with a correlation between [HHb]/VO2 and tauVO2p of 0.91. CONCLUSION: When tauVO2p is greater than ~20s, the rate of adjustment of phase 2 VO2p (muscle VO2) appears to be mainly constrained by the matching of local O2 delivery to muscle VO2 (i.e., microvascular blood flow distribution). In those with a shorter tauVO2 there is a reduced "overshoot" in the [HHb]/VO2 as represented by a lower [HHb]/VO2 ratio. These data experimentally support the idea that groups with progressively slower VO2 kinetics are O2 availability dependent, requiring a progressively greater O2 extraction during the on-transient of exercise.

Research paper thumbnail of Hypercapnic Chemoreflex And Muscle Metaboreflex Interactions: Effects on Heart

Medicine & Science in Sports & Exercise, 2010

Research paper thumbnail of Chronic fatigue syndrome: acute infection and history of physical activity affect resting levels and response to exercise of plasma oxidant/antioxidant status and heat shock proteins

Journal of Internal Medicine, 2012

Chronic fatigue syndrome: acute infection and history of physical activity affect resting levels ... more Chronic fatigue syndrome: acute infection and history of physical activity affect resting levels and response to exercise of plasma oxidant ⁄ antioxidant status and heat shock proteins.

Research paper thumbnail of Statins alter oxidant-antioxidant status and lower exercise-induced oxidative stress

Int. Journal of Clinical Pharmacology and Therapeutics, 2007

Data on effects of statins on resting oxidant-antioxidant status are contradictory and no study h... more Data on effects of statins on resting oxidant-antioxidant status are contradictory and no study has been published on the effects of statins on exercise-induced oxidative stress. We carried out a 6-month longitudinal study in 10 dyslipidemic patients receiving 10 mg/day atorvastatin and 13 healthy sedentary subjects. Thiobarbituric acid reactive substances (TBARS) and reduced ascorbic acid (RAA) were measured in plasma at rest and every 5 minutes after submaximal isometric thumb adduction and handgrip sustained until exhaustion. At inclusion, resting TBARS and RAA levels in controls and patients did not differ and exercise increased TBARS and decreased RAA. Atorvastatin reduced resting TBARS and RAA levels in a time-dependent but lipid-independent manner. The main effect was a post-exercise increase in TBARS, without affecting the post-exercise RAA levels. The reduction in oxidative stress occurred earlier in oxidative muscles involved in thumb adduction. In conclusion, atorvastatin lowers resting oxidant-antioxidant activity: exercise-induced oxidative stress occurs mainly in muscles having a high oxidative capacity.

Research paper thumbnail of The changes in neuromuscular excitability with normobaric hyperoxia in humans

Experimental Physiology, 2009

Based on previous observations in hyperbaric hyperoxia, we hypothesized that normobaric hyperoxia... more Based on previous observations in hyperbaric hyperoxia, we hypothesized that normobaric hyperoxia, often used during general anaesthesia and resuscitation, might also induce a neuromuscular excitability. In healthy volunteers, we studied the consequences of a 50 min period of pure oxygen breathing on the neuromuscular conduction time (CT), the amplitude of the compound evoked muscle potential (M-wave), the latency and amplitude of the Hoffman reflex (H reflex) and the electromyographic tonic vibratory response (TVR) of the flexor digitorum superficialis muscle to explore the proprioceptive reflex loop. Hyperoxia-induced oxidative stress was measured by the changes in blood markers of lipid peroxidation (thiobarbituric acid reactive substances, TBARS) and antioxidant response (reduced ascorbic acid, RAA). During hyperoxia, the M-wave amplitude increased, both CT and H reflex latency were shortened, and the H reflex amplitude increased. By contrast, TVR significantly decreased. Concomitantly, an oxidative stress was assessed by increased TBARS and decreased RAA levels. This study shows the existence of dual effects of hyperoxia, which facilitates the muscle membrane excitability, nerve conduction and spinal reflexes, but reduces the gain of the proprioceptive reflex loop. The activation of the group IV muscle afferents by hyperoxia and the resulting oxidative stress might explain the TVR depression.

Research paper thumbnail of Accuracy of the double indicator method for measurement of extravascular lung water depends on the type of acute lung injury*

Critical Care Medicine, 2004

The double indicator method is sensitive to alterations in the distribution of pulmonary blood fl... more The double indicator method is sensitive to alterations in the distribution of pulmonary blood flow. This distribution is influenced by the type of lung injury. The aim of this study was to compare measurements of lung water by the double indicator method with measurements obtained by gravimetry in a direct lung injury model induced by tracheal instillation of hydrochloric acid and in an indirect lung injury model induced by the intravenous injection of oleic acid. Prospective, randomized laboratory study. Animal research laboratory. Forty-two female pigs (28+/-3 kg). Pigs were anesthetized and ventilated and were allocated into three groups: control (n = 6), hydrochloric acid (4 mL/kg intratracheally, n = 24), or oleic acid (0.1 mL/kg intravenously, n = 12). Hydrochloric acid instillation or oleic acid injection resulted in a similar hypoxemia and induced a two- to three-fold increase in extravascular lung water (EVLW) by gravimetry (EVLWG) at 3 hrs compared with controls. In the oleic acid group, there was a significant correlation between EVLWG and EVLW by double indicator method (EVLWDI; r =.88, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;.0001). The bias for EVLWDI - EVLWG measurements was -5.2 mL/kg (95% confidence interval, -5.7 to -4.7 mL/kg) with 95% limits of agreement of -7 to -3.4 mL/kg. In the hydrochloric acid group, there was no significant correlation between EVLWDI and EVLWG values, and the double indicator method failed to detect pulmonary edema in 65% of the animals (EVLWDI &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;8 mL/kg). The bias was -7.9 mL/kg (95% confidence interval, -9.3 to -6.5 mL/kg) with 95% limits of agreement of -14.4 to -1.4 mL/kg. The double indicator method is useful for evaluation of pulmonary edema in indirect lung injury, as induced by oleic acid, but produces misleading values in direct lung injury, as produced by hydrochloric instillation.

Research paper thumbnail of Effect of voluntary hypocapnic hyperventilation on cutaneous circulation in resting heated humans

American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2012

Hypocapnia attenuates the sweat response normally seen in hyperthermic resting subjects, but its ... more Hypocapnia attenuates the sweat response normally seen in hyperthermic resting subjects, but its effect on the blood flow response in their nonglabrous skin under the same hyperthermic conditions remains unclear. In the present study, we investigated whether hypocapnia induced by voluntary hyperventilation affects the blood flow response to heat stress in the nonglabrous skin of resting humans. Nine healthy male subjects were passively heated using legs-only hot water immersion and a water-perfused suit, which caused esophageal temperature (Tes) to increase by as much as 1.0°C. During normothermia and at +0.6°C Tes and +1.0°C Tes, the subjects performed two voluntary 7-min hyperventilation (minute ventilation = 40 l/min) trials (hypocapnic and eucapnic) in random order. End-tidal CO2 pressure was reduced by 23–25 torr during hypocapnic hyperventilation, but it was maintained at the spontaneous breathing level during eucapnic hyperventilation. Cutaneous blood flow was evaluated as th...

Research paper thumbnail of Evaluation of muscle metaboreflex function through graded reduction in forearm blood flow during rhythmic handgrip exercise in humans

American Journal of Physiology-Heart and Circulatory Physiology, 2011

Hypoperfusion of active skeletal muscle elicits a reflex pressor response termed the muscle metab... more Hypoperfusion of active skeletal muscle elicits a reflex pressor response termed the muscle metaboreflex. Our aim was to determine the muscle metaboreflex threshold and gain in humans by creating an open-loop relationship between active muscle blood flow and hemodynamic responses during a rhythmic handgrip exercise. Eleven healthy subjects performed the exercise at 5 or 15% of maximal voluntary contraction (MVC) in random order. During the exercise, forearm blood flow (FBF), which was continuously measured using Doppler ultrasound, was reduced in five steps by manipulating the inner pressure of an occlusion cuff on the upper arm. The FBF at each level was maintained for 3 min. The initial reductions in FBF elicited no hemodynamic changes, but once FBF fell below a threshold, mean arterial blood pressure (MAP) and heart rate (HR) increased and total vascular conductance (TVC) decreased in a linear manner. The threshold FBF during the 15% MVC trial was significantly higher than during...