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Introduction: in view of the rapid development of the trail-running activity in recent years, we performed a comparative study of the practices of the general practitioners of Reunion Island with regard to this sport and its specificities. Method: two groups were formed, a group of untrained physicians (MNF) and a group of trained physicians (MF). Clinical cases were submitted to them and their answers evaluated on digital visual scales. According to the Delphi method, the expected answers have been discussed previously by an expert group. The averages and standard deviations were compared and allowed us an inter-group and intra-group analysis. Results: variability in practice was found significantly (p

The role of altered peripheral muscle function in exercise intolerance of chronic obstructive pulmonary disease (COPD) is now well established. However, the mechanisms underlying this phenomen, have not been determined. One hypothesis is that the oxidative stress, that leads to tissue injury may be involved. A recent study has shown that general exercise caused systemic oxidative stress in COPD patients. However, the origin of this stress was not absolutely clear: airways, muscle, both, or other? The aim of this study was first to determine with a systemic approach, whether systemic oxidative stress occur in patients who perform local exercise and then with a muscular needle biopsy approach, to confirm the muscular origin of this oxidative stress.In each approach, 7 COPD patients moderate to severe and 7 age-matched subjects performed an endurance test consisting of dynamic strength of the quadriceps against 40% (systemic approach) or 30% (biopsy approach) of maximal voluntary strength at an imposed regular pace until exhaustion.The results showed in each approach, that endurance test duration was significantly decreased in the COPD patients (p0.05). In systemic approach, the results showed that blood vitamin E at rest was significantly decreased in the COPD (p0.001), with a significant increase in superoxide anion release by stimulated phagocytes (p0.001). Local exercise induced, only in COPD, a significant increase in serum MDA (p0.05), which is an index of oxidative stress. In the biopsy approach, the results showed that local exercise induced in COPD an increase in muscular levels of MDA. A significant increase in muscular peroxidase glutathion activity (antioxidant) occurred after exercise only in normal subjects (p0.05). In conclusion, this study in COPD, confirms the altered peripheral muscle function, reveals a deficit in blood vitamin E and suggest that local muscular exercise causes a muscular oxidative stress in these patients. Further studies are needed to confirm these results and evaluate the implication of this oxidative stress in the myopathy of COPD.

International audience; Background: A high level of physical fitness is associated with cardiovascular health in adolescents. The aims of this study were to assess the levels of physical fitness of French adolescents and to determine the prevalence of these adolescents below the minimum level of cardiorespiratory fitness needed to guarantee future favorable cardiovascular profile.Methods: Participants were 12,082 French children and adolescents (5975 boys, 6107 girls) aged to 9 from 16 years. Cardiorespiratory fitness, muscular endurance, speed, flexibility and speed agility were tested. The associations of physical fitness measures with adolescent's characteristics were analyzed using Student t test, one-way ANOVA, or Pearson correlations as appropriate.Results: Boys were physically fitter than girls, expected for flexibility (P < 0.0001). Subjects of normal weight adolescents had significantly better results than overweight or obese adolescents (P < 0.05 for all comparisons), but also in comparison with underweight adolescents for muscular endurance, flexibility, cardiorespiratory fitness test (P < 0.05). Our findings indicate that, on the basis of cardiorespiratory fitness, 16% of French boys and 7.7% of French girls have a risk of future cardiovascular disease (P < 0.0001). This subgroup also performed poorly in all other tests of physical fitness used (P < 0.0001). Aerobic fitness decreased significantly with the age (r = −0.168 for boys; r = −0.261 for girls).Conclusions: Our results indicate that the physical fitness of French adolescents must be improved to help protect against cardiovascular disease in adulthood, especially in boys. The study showed also a dramatically decrease of the cardiorespiratory fitness during the adolescence period. Developing and introducing a health promotion curriculum in the French schools is suggested to improve health and physical fitness.; Position du problème: La condition physique est un déterminant important de la santé chez l’enfant et l’adolescent. L’objectif principal de notre étude était d’évaluer le niveau de la condition physique des adolescents en France. L’objectif secondaire était d’évaluer la prévalence des adolescents ayant un profil cardiovasculaire défavorable.Méthodes: Au total, 12 082 enfants et adolescents (5975 garçons, 6107 filles) âgés de 9 à 16 ans en France (16 régions) ont participé au programme Bouge. L’endurance cardiorespiratoire et musculaire, la vitesse, la souplesse et l’agilité/coordination ont été évaluées. Les liens entre les composantes de la condition physique et les caractéristiques des enfants et des adolescents ont été testés à l’aide du test t de Student, de l’analyse de la variance à un facteur et du coefficient de corrélation de Pearson.Résultats: Les garçons ont eu des scores plus élevés que les filles, excepté pour le test de souplesse (p < 0,0001). Les enfants et les adolescents normopondérés ont réalisé de meilleures performances que ceux en surpoids ou obèses sur l’ensemble des paramètres (p < 0,05), mais aussi en comparaison avec les dénutris sur l’endurance musculaire et la souplesse (p < 0,05). Nos résultats indiquent que, basé sur l’endurance cardiorespiratoire, la prévalence d’adolescent à risque de développer une maladie cardiovasculaire à l’âge adulte est de 16 % et 7,7 % chez les garçons et les filles, respectivement (p < 0,0001). Ce sous-groupe a aussi réalisé des performances plus faibles dans l’ensemble des autres tests de la condition physique (p < 0,0001). L’âge était associé à une diminution de l’endurance cardiorespiratoire (r = −0,168 pour les garçons ; r = −0,261 pour les filles ; p < 0,0001).Conclusions: Nos résultats montrent que la condition physique des jeunes français doit être améliorée pour diminuer le risque de maladies cardiovasculaires à l’âge adulte, spécifiquement chez les garçons. Notre étude montre également une diminution importante des capacités d’endurance cardiorespiratoire lors de l’adolescence. Développer et mettre en place des programmes d’intervention et/ou de promotion de la santé dans les écoles françaises est nécessaire afin d’améliorer la santé et la condition physique de ces enfants et adolescent

International audience; Background: A high level of physical fitness is associated with cardiovascular health in adolescents. The aims of this study were to assess the levels of physical fitness of French adolescents and to determine the prevalence of these adolescents below the minimum level of cardiorespiratory fitness needed to guarantee future favorable cardiovascular profile.Methods: Participants were 12,082 French children and adolescents (5975 boys, 6107 girls) aged to 9 from 16 years. Cardiorespiratory fitness, muscular endurance, speed, flexibility and speed agility were tested. The associations of physical fitness measures with adolescent's characteristics were analyzed using Student t test, one-way ANOVA, or Pearson correlations as appropriate.Results: Boys were physically fitter than girls, expected for flexibility (P < 0.0001). Subjects of normal weight adolescents had significantly better results than overweight or obese adolescents (P < 0.05 for all comparisons), but also in comparison with underweight adolescents for muscular endurance, flexibility, cardiorespiratory fitness test (P < 0.05). Our findings indicate that, on the basis of cardiorespiratory fitness, 16% of French boys and 7.7% of French girls have a risk of future cardiovascular disease (P < 0.0001). This subgroup also performed poorly in all other tests of physical fitness used (P < 0.0001). Aerobic fitness decreased significantly with the age (r = −0.168 for boys; r = −0.261 for girls).Conclusions: Our results indicate that the physical fitness of French adolescents must be improved to help protect against cardiovascular disease in adulthood, especially in boys. The study showed also a dramatically decrease of the cardiorespiratory fitness during the adolescence period. Developing and introducing a health promotion curriculum in the French schools is suggested to improve health and physical fitness.; Position du problème: La condition physique est un déterminant important de la santé chez l’enfant et l’adolescent. L’objectif principal de notre étude était d’évaluer le niveau de la condition physique des adolescents en France. L’objectif secondaire était d’évaluer la prévalence des adolescents ayant un profil cardiovasculaire défavorable.Méthodes: Au total, 12 082 enfants et adolescents (5975 garçons, 6107 filles) âgés de 9 à 16 ans en France (16 régions) ont participé au programme Bouge. L’endurance cardiorespiratoire et musculaire, la vitesse, la souplesse et l’agilité/coordination ont été évaluées. Les liens entre les composantes de la condition physique et les caractéristiques des enfants et des adolescents ont été testés à l’aide du test t de Student, de l’analyse de la variance à un facteur et du coefficient de corrélation de Pearson.Résultats: Les garçons ont eu des scores plus élevés que les filles, excepté pour le test de souplesse (p < 0,0001). Les enfants et les adolescents normopondérés ont réalisé de meilleures performances que ceux en surpoids ou obèses sur l’ensemble des paramètres (p < 0,05), mais aussi en comparaison avec les dénutris sur l’endurance musculaire et la souplesse (p < 0,05). Nos résultats indiquent que, basé sur l’endurance cardiorespiratoire, la prévalence d’adolescent à risque de développer une maladie cardiovasculaire à l’âge adulte est de 16 % et 7,7 % chez les garçons et les filles, respectivement (p < 0,0001). Ce sous-groupe a aussi réalisé des performances plus faibles dans l’ensemble des autres tests de la condition physique (p < 0,0001). L’âge était associé à une diminution de l’endurance cardiorespiratoire (r = −0,168 pour les garçons ; r = −0,261 pour les filles ; p < 0,0001).Conclusions: Nos résultats montrent que la condition physique des jeunes français doit être améliorée pour diminuer le risque de maladies cardiovasculaires à l’âge adulte, spécifiquement chez les garçons. Notre étude montre également une diminution importante des capacités d’endurance cardiorespiratoire lors de l’adolescence. Développer et mettre en place des programmes d’intervention et/ou de promotion de la santé dans les écoles françaises est nécessaire afin d’améliorer la santé et la condition physique de ces enfants et adolescent

This study investigated 1) red blood cells (RBC) rigidity and 2) lactate influxes into RBCs in endurance-trained athletes with and without exercise-induced hypoxemia (EIH). Nine EIH and six non-EIH subjects performed a submaximal steady-state exercise on a cyclo-ergometer at 60% of maximal aerobic power for 10 min, followed by 15 min at 85% of maximal aerobic power. At rest and at the end of exercise, arterialized blood was sampled for analysis of arterialized pressure in oxygen, and venous blood was drawn for analysis of plasma lactate concentrations and hemorheological parameters. Lactate influxes into RBCs were measured at three labeled [U-14C]lactate concentrations (1.6, 8.1, and 41 mM) on venous blood sampled at rest. The EIH subjects had higher maximal oxygen uptake than non-EIH ( P < 0.05). Total lactate influx was significantly higher in RBCs from EIH compared with non-EIH subjects at 8.1 mM (1,498.1 ± 87.8 vs. 1,035.9 ± 114.8 nmol·ml−1·min−1; P < 0.05) and 41 mM (2,562.0 ± 145.0 vs. 1,618.1 ± 149.4 nmol·ml−1·min−1; P < 0.01). Monocarboxylate transporter-1-mediated lactate influx was also higher in EIH at 8.1 mM ( P < 0.05) and 41 mM ( P < 0.01). The drop in arterial oxygen partial pressure was negatively correlated with total lactate influx measured at 8.1 mM ( r = −0.82, P < 0.05) and 41 mM ( r = −0.84, P < 0.05) in the two groups together. Plasma lactate concentrations and hemorheological data were similar in the two groups at rest and at the end of exercise. The results showed higher monocarboxylate transporter-1-mediated lactate influx in the EIH subjects and suggested that EIH could modify lactate influx into erythrocyte. However, higher lactate influx in EIH subjects was not accompanied by an increase in RBC rigidity.

International audience; Studies of heart rate variability (HRV) have so far produced contradictory evidence to support the common belief that endurance training enhances cardiac parasympathetic tone. This may be related to the fact that most studies failed to specifically isolate the vagally mediated influence of respiration. This study used a cross-sectional comparison of endurance athletes (n=20; ATHL) exhibiting resting bradycardia and age-matched nonathletes (n=12; CRTL) to indirectly assess training effects on amplitude and timing characteristics of respiratory sinus arrhythmia (RSA). Continuous electrocardiogram (ECG) and ventilatory flows were recorded during spontaneous breathing (SP), as well as during breathing at four cycles less than (M4) or more (P4) than SP, to also examine potential repercussions of training on the sensitivity of the cardiac vagal responses to breathing. A fast Fourier transform procedure was used to quantify the standard spectral high-frequency (HF) and low-frequency (LF) components and a respiratory-centered frequency (RCF) component of HRV. RSA was assessed using a breath-by-breath quantification of the amplitude and timing of the maximum change in instantaneous heart rate. Under baseline SP conditions, heart rate was lower in ATHL (62.6+/-6.5 vs. 75.2+/-9 beats/min; p

International audience; The influences of sex and age upon endurance performance have previously been documented for both running and swimming. A number of recent studies have investigated how sex and age influence triathlon performance, a sport that combines three disciplines (swimming, cycling and running), with competitions commonly lasting between 2 (short distance: 1.5-km swim, 40-km cycle and 10-km run) and 8 h (Ironman distance: 3.8-km swim,180-km cycle and 42-km run) for elite triathletes. Age and sex influences upon performance have also been investigated for ultra-triathlons, with distances corresponding to several Ironman distances and lasting several days, and for off-road triathlons combining swimming, mountain biking and trail running. Triathlon represents an intriguing alternative model for analysing the effects of age and sex upon endurance and ultra-endurance ([6 h) performance because sex differences and age-related declines in performance can be analysed in the same individuals across the three separate disciplines. The relative participation of both females and masters athletes (age[40 years) in triathlon has increased consistently over the past 25 years. Sex differences in triathlon performance are also known to differ between the modes of locomotion adopted (swimming, cycling or running) for both elite and non-elite triathletes. Generally, time differences between sexes in swimming have been shown to be smaller on average than during cycling and running. Both physiological and morphological factors contribute to explaining these findings. Performance density (i.e. the time difference between the winner and tenth-placed competitor) has progressively improved (time differences have decreased) for international races over the past two decades for both males and females, with performance density now very similar for both sexes. For age-group triathletes, sex differences in total triathlon performance time increases with age. However,the possible difference in age-related changes in the physiological determinants of endurance and ultra-endurance performances between males and females needs further investigation. Non-physiological factors such as low rates of participation of older female triathletes may also contribute to the greater age-related decline in triathlon performance shown by females. Total triathlon performance has been shown to decrease in a curvilinear manner with advancing age. However, when triathlon performanceis broken down into its three disciplines, there is a smaller age-related decline in cycling performance than in running and swimming performances. Age-associated changes in triathlon performance are also related to the total duration of triathlon races. The magnitude of the declines in cycling and running performances with advancing age for short triathlons are less pronounced than for longer Ironman distance races. Triathlon distance is also important when considering how age affects the rate of the decline in performance. Off-road triathlon performances display greater decrements with age than road-based triathlons, suggesting that the type of discipline (road vs. mountain bike cycling and road vs. trail running) is an important factor in age-associated changes in triathlon performance.Finally, masters triathletes have shown relative improvements in their performances across the three triathlon disciplines and total triathlon event times during Ironman races over the past three decades. This raises an important issue as to whether older male and female triathletes have yet reached their performance limits during Ironman triathlons

International audience; The influences of sex and age upon endurance performance have previously been documented for both running and swimming. A number of recent studies have investigated how sex and age influence triathlon performance, a sport that combines three disciplines (swimming, cycling and running), with competitions commonly lasting between 2 (short distance: 1.5-km swim, 40-km cycle and 10-km run) and 8 h (Ironman distance: 3.8-km swim,180-km cycle and 42-km run) for elite triathletes. Age and sex influences upon performance have also been investigated for ultra-triathlons, with distances corresponding to several Ironman distances and lasting several days, and for off-road triathlons combining swimming, mountain biking and trail running. Triathlon represents an intriguing alternative model for analysing the effects of age and sex upon endurance and ultra-endurance ([6 h) performance because sex differences and age-related declines in performance can be analysed in the same individuals across the three separate disciplines. The relative participation of both females and masters athletes (age[40 years) in triathlon has increased consistently over the past 25 years. Sex differences in triathlon performance are also known to differ between the modes of locomotion adopted (swimming, cycling or running) for both elite and non-elite triathletes. Generally, time differences between sexes in swimming have been shown to be smaller on average than during cycling and running. Both physiological and morphological factors contribute to explaining these findings. Performance density (i.e. the time difference between the winner and tenth-placed competitor) has progressively improved (time differences have decreased) for international races over the past two decades for both males and females, with performance density now very similar for both sexes. For age-group triathletes, sex differences in total triathlon performance time increases with age. However,the possible difference in age-related changes in the physiological determinants of endurance and ultra-endurance performances between males and females needs further investigation. Non-physiological factors such as low rates of participation of older female triathletes may also contribute to the greater age-related decline in triathlon performance shown by females. Total triathlon performance has been shown to decrease in a curvilinear manner with advancing age. However, when triathlon performanceis broken down into its three disciplines, there is a smaller age-related decline in cycling performance than in running and swimming performances. Age-associated changes in triathlon performance are also related to the total duration of triathlon races. The magnitude of the declines in cycling and running performances with advancing age for short triathlons are less pronounced than for longer Ironman distance races. Triathlon distance is also important when considering how age affects the rate of the decline in performance. Off-road triathlon performances display greater decrements with age than road-based triathlons, suggesting that the type of discipline (road vs. mountain bike cycling and road vs. trail running) is an important factor in age-associated changes in triathlon performance.Finally, masters triathletes have shown relative improvements in their performances across the three triathlon disciplines and total triathlon event times during Ironman races over the past three decades. This raises an important issue as to whether older male and female triathletes have yet reached their performance limits during Ironman triathlons

International audience; The goal of this study was to establish how increased ventilation modifies postural stability, as characterized by body sway and leg muscle activities. Twelve healthy subjects had to perform six 30-second postural tests: one pre-exercise test while breathing gently and then one test every minute for the five minutes immediately following a maximum-intensity, incremental cycling exercise test. Subjects were asked to maintain an upright stance on a force plate for 30 s, with their eyes open. Movement of the centre of pressure in the sagittal plane was monitored in the time and spectral domains. Myoelectric activities of the soleus and tibialis anterior muscles were recorded using surface electromyography. Ventilatory parameters were measured with a portable, telemetric device. Postural changes related to respiratory variations were quantified by coherence analysis. The results showed that hyperventilation induced by exercise was accompanied by a significant increase in postural parameters, indicating a reduction in postural stability following a change in ventilatory drive. Coherence analysis confirmed the ventilatory origin of the postural oscillations. The results suggest that ventilation may be an important factor in postural disturbance during physical activity. The observed increases in leg muscle activities were most likely related to musculo-articular stiffening.

International audience; This paper deals with the effects of exercise training on oxygen consumption (MO(2)) and ROS metabolism in the red muscle of trained and untrained female silver eels. Their critical swimming speed (U(crit)) was determined before and after a 4-day training (10h of swimming at 70% of U(crit) and 14 h at 50%, every day). The U(crit) of trained eels increased significantly (by about 7%). The in vitro MO(2) and ROS production by the red fibres were higher (not significant) in trained than in untrained eels, but the ROS production/MO(2) ratio was alike in both groups. The antioxidant-enzyme activities and lipoperoxidation index in trained eels were both lower than those of the untrained ones. These biochemical changes related to the increase in U(crit) suggest that such a training session could maintained or even increased aerobic power of the red muscle without deleterious impact by ROS. These regulations could play a role in the eel's swimming performance efficiency.

Background— Numerous studies have reported evidence of cardiac injury associated with transient left ventricular (LV) systolic and diastolic dysfunction after prolonged and strenuous exercise. We used 2D ultrasound speckle tracking imaging to evaluate the effect of an ultralong-duration exercise on LV regional strains and torsion. We speculated that systolic dysfunction after exercise is associated with depressed LV strains and torsion, and diastolic dysfunction results from decreased and delayed untwisting, a key factor of LV suction and early filling. Methods and Results— Twenty-three triathletes underwent conventional and speckle tracking imaging echocardiography at rest before and immediately after an ultralong distance triathlon. Measurements included LV longitudinal, circumferential and radial strains, LV rotations, and LV torsion. After the race, LV systolic dysfunction was characterized by a decrease in LV longitudinal, radial, and circumferential strains, especially for apical radial strains (44.6�15.1% versus 31.1�13.8%, P P =0.09) and significantly delayed (91�18% versus 128�31% of systolic duration, P Conclusions— This study documented major alterations in cardiac strains and torsion after an ultralong distance triathlon. LV systolic strains were depressed but not delayed, whereas twisting was decreased and delayed. This altered pattern hampered the rapid untwisting during isovolumic relaxation phase, reducing LV diastolic suction and early filling.

International audience; Glucagon-like peptide-1 (GLP-1) is a peptide released by the intestine and the brain. We previously demonstrated that brain GLP-1 increases glucose-dependent hyperinsulinemia and insulin resistance. These two features are major characteristics of the onset of type 2 diabetes. Therefore, we investigated whether blocking brain GLP-1 signaling would prevent high-fat diet (HFD)-induced diabetes in the mouse. Our data show that a 1-month chronic blockage of brain GLP-1 signaling by exendin-9 (Ex9), totally prevented hyperinsulinemia and insulin resistance in HFD mice. Furthermore, food intake was dramatically increased, but body weight gain was unchanged, showing that brain GLP-1 controlled energy expenditure. Thermogenesis, glucose utilization, oxygen consumption, carbon dioxide production, muscle glycolytic respiratory index, UCP2 expression in muscle, and basal ambulatory activity were all increased by the exendin-9 treatment. Thus, we have demonstrated that in response to a HFD, brain GLP-1 signaling induces hyperinsulinemia and insulin resistance and decreases energy expenditure by reducing metabolic thermogenesis and ambulatory activity.

CHRONIC HYPOXIC EXPOSURE INDUCES several structural modifications in skeletal muscles, that is, a decrease in fiber crosssectional area and in muscle mass, mainly due to an anorexic effect. Even when the anorexic effect is controlled by using a pair-fed experimental design, the composition of myosin heavy chain (MHC) is changed, and an increase in the fast-type isoforms is observed. Indeed, a shift toward glycolytic-oxidative fibers (MHC-IIA) in muscles of rats exposed to hypoxia is generally reported, except in the study of Sillau and Banchero (35), in which no difference was shown in the fiber type composition of rat soleus after hypoxic exposure. In addition, Bigard et al. (7) showed that 4 wk in hypobaric hypoxia resulted in a decrease in MHC-I in the soleus of young rats. Thus, hypoxia seems to affect the structural and biochemical properties of skeletal muscles by inducing a transformation from type I to type II fibers. Opposite to chronic hypoxia, endurance training is likely to induce a decrease in fast fibers and an increase in slow-fiber proportion. For instance, Green et al. (18) demonstrated that a prolonged (15 wk) endurance training induced a fiber transformation from fast-type IIa to slow type I on the basis of enzyme histochemistry and MLC distribution. Endurance training (10 wk) also induced changes in the distribution patterns of fast alkali MLC isoforms detectable within FMb (triplet of isomyosins with distinct MLC complement, FM1b, FM2b, and FM3b) composed of the fastest isoform MHC-IIB (3). Surprisingly, endurance training seems to induce an increase in the actomyosin ATPase activity and maximal shortening velocity in the slow-twitch soleus muscle and a decrease in the fast region of the vastus lateralis (34). These observations of changes in ATPase activity and myosin isoform shifts appear to be paradoxical, as ATP hydrolyzed by myosin represents the main component of ATP consumption during contraction. These changes in myosin isoform expression probably regulate ATP consumption. Actually, there is strong evidence that myosin isoforms are the main determinant of ATPase activity, at least at low temperature in vitro. In this study, we analyzed myosin isoform composition and myofibrillar ATPase activity in soleus muscles of rats exposed to normoxia or hypoxia with or without endurance training to assess the variations of soleus myofibrillar ATPase (m-ATPase) activity that accompany the changes in MHC isoform expression under training and/or chronic hypoxia conditions.

This study investigated the relationships between walking speed and heart rate (HR) variability (HRV) in eleven subjects during a 24-h race. It was hypothesized that the nycthemeral rhythm on HR is preserved during the race. RR intervals and walking speed were measured. Fast Fourier transform was applied to samples of 1,024 successive RR intervals collected every hour from a HR monitor. Walking speed was averaged every hour and decreased (first lap: 8.8 +/- 0.3 vs. last lap: 7.3 +/- 0.8 km h(-1), P < 0.001) with HR also decreasing (max at 19:00 h: 143 +/- 9 vs. min at 7:00 h: 117 +/- 14 beats min(-1), P < 0.001) following a third order polynomial shape. HRV power spectral components followed distribution patterns similar to the mean RR during the race with a minimum in the early evening (19:00-20:00 h) and a maximum in the morning (5:00-8:00 h). Thus, as for mean RR, spectral components over time are also fitted to a third order polynomial regression. LF/HF ratio increased linearly (min = 0.5 +/- 0.3, max = 2.8 +/- 5.3, P = 0.02). Although mean HF peak did not decrease significantly over time, it was positively correlated with walking speed. In conclusion, this study showed that despite a constant decrease in walking speed, HR circadian rhythm is preserved during a continuous 24-h walking race. The short-term HRV components remain linked to HR whereas the LF/HF ratio increases linearly until the end of the race whatever HR is.

Exercise training improves arterial compliance due to increases in blood flow to skeletal muscle during repeated bouts of daily exercise. The effect of resuming training on arterial stiffness in previously well-trained subjects is poorly documented. Hence, the purpose of this study was to determine the vascular effects induced by return to exercise in highly trained cyclists. Pulse wave velocity (PWV), an index of arterial stiffness, was assessed at rest and during constant moderate-intensity cycle exercises before and after 16 weeks of endurance training. The impact of daily exercise on the concentration of nitric oxide (NO) measured as nitrate in plasma was examined at rest and during maximal exercise before and after the training period. At rest, PWV was significantly lower in the subjects after a training session (6.4 ± 0.4 vs. 8.1 ± 0.4 m·s-1, p < 0.05). During constant exercise, PWV was significantly and positively correlated with increases in blood pressure. The increased PWV induced by exercise was, however, significantly lower after training (9.8 ± 0.6 vs. 11.4 ± 0.6 m·s-1, p < 0.05). After the training program, nitrate plasma levels at rest were higher. During the maximal test, the plasma nitrate concentration was increased in the subjects studied before the training period, but not after. These results show that resumption of chronic endurance training rapidly induces adaptive changes in arterial stiffness and NO release that may contribute to improved physical fitness in athletes.Key words: exercise, trained subjects, pulse wave velocity, nitrate, arteries.

International audience; The objective of this work was to assess the repeatability of two surface electromyographic (sEMG) recording techniques, the classical bipolar configuration and a Laplacian configuration to document their ability to provide reliable information during follow-up studies. The signals were recorded on 10 healthy subjects during voluntary isometric contractions of the biceps brachii muscle at different constant contraction levels. Slopes, area ratios (at 60% of the maximal voluntary contraction (MVC)) and initial values (at 20%, 40%, 60%, 80% and 100% MVC) of the root mean square (RMS), the mean power frequency (MPF) and the muscle fibre conduction velocity (CV) were estimated. Experimental sessions were repeated on three different days with both electrode sets to evaluate the repeatability of sEMG parameter estimates. Classical results were observed, such as an increase in the RMS and the CV with the contraction level. Only initial values of RMS and MPF were shown to be dependent on electrode type. These two parameters presented intra-class correlation coefficient values higher than .80 for high contraction levels. On the whole, the repeatability of the measures was good; however it was better for all sEMG parameter estimates with bipolar electrodes than Laplacian electrodes. Because a bipolar configuration is less selective than a Laplacian one, it provides a global view of muscular activity, which is more repeatable, hence more suitable for follow-up studies.

The aim of this study was to analyse the effect of pedalling rate on the pattern of mechanical torque application and on neuromuscular fatigue during prolonged cycling exercise. Eleven well-trained individuals performed three 1-h pedalling sessions, at 50 rev.min-1, 110 rev.min-1 and a freely chosen cadence, at an intensity corresponding to 65% of their maximal aerobic power. The mechanical torque applied on the right pedal was recorded for 30 s every 5 min while pedalling. Contractile and neural properties of the quadriceps and hamstring muscles were analysed before and immediately after each of the three pedalling sessions. The post-exercise reduction in knee extensors maximal voluntary contraction was significant (P

International audience; OBJECTIVE: To test whether ventilatory thresholds, measured during an exercise test, could be assessed using time varying analysis of respiratory sinus arrhythmia frequency (f(RSA)). METHODS: Fourteen sedentary subjects and 12 endurance athletes performed a graded and maximal exercise test on a cycle ergometer: initial load 75 W (sedentary subjects) and 150 W (athletes), increments 37.5 W/2 min. f(RSA) was extracted from heart period series using an evolutive model. First (T(V1)) and second (T(V2)) ventilatory thresholds were determined from the time course curves of ventilation and ventilatory equivalents for O(2) and CO(2). RESULTS: f(RSA) was accurately extracted from all recordings and positively correlated to respiratory frequency (r = 0.96 (0.03), p

The present study investigated whether muscular monocarboxylate transporter (MCT) 1 and 4 contents are related to the blood lactate removal after supramaximal exercise, fatigue indexes measured during different supramaximal exercises, and muscle oxidative parameters in 15 humans with different training status. Lactate recovery curves were obtained after a 1-min all-out exercise. A biexponential time function was then used to determine the velocity constant of the slow phase (γ2), which denoted the blood lactate removal ability. Fatigue indexes were calculated during 1-min all-out (FIAO) and repeated 10-s (FISprint) cycling sprints. Biopsies were taken from the vastus lateralis muscle. MCT1 and MCT4 contents were quantified by Western blots, and maximal muscle oxidative capacity ( Vmax) was evaluated with pyruvate + malate and glutamate + malate as substrates. The results showed that the blood lactate removal ability (i.e., γ2) after a 1-min all-out test was significantly related to MCT1 content ( r = 0.70, P < 0.01) but not to MCT4 ( r = 0.50, P > 0.05). However, greater MCT1 and MCT4 contents were negatively related with a reduction of blood lactate concentration at the end of 1-min all-out exercise ( r = −0.56, and r = −0.61, P < 0.05, respectively). Among skeletal muscle oxidative indexes, we only found a relationship between MCT1 and glutamate + malate Vmax ( r = 0.63, P < 0.05). Furthermore, MCT1 content, but not MCT4, was inversely related to FIAO ( r = −0.54, P < 0.05) and FISprint ( r = −0.58, P < 0.05). We concluded that skeletal muscle MCT1 expression was associated with the velocity constant of net blood lactate removal after a 1-min all-out test and with the fatigue indexes. It is proposed that MCT1 expression may be important for blood lactate removal after supramaximal exercise based on the existence of lactate shuttles and, in turn, in favor of a better tolerance to muscle fatigue.

The effect of endurance training on muscle electrical activity during general exercise testing was investigated in physically active patients with chronic obstructive pulmonary disease (COPD). Before and after rehabilitation, patients performed identical incremental exercise tests. Pulmonary gas exchange, venous lactate and pyruvate concentrations, and the quadriceps electromyographic signal were sampled every minute throughout exercise testing. Three weeks of rehabilitation increased exercise capacity without modifying pulmonary function. M-wave amplitude, root mean square (RMS) of electromyographic activity, and RMS/oxygen uptake were increased significantly during post-rehabilitation testing at the same exercise intensity compared to pre-rehabilitation. Median frequency was significantly lower after training. These modifications reflect greater muscle excitability, greater muscle activation for the same level of exercise, and higher recruitment of slow-twitch fibers. Pulmonary rehabilitation in active COPD patients may normalize the electrical activity of skeletal muscles during incremental dynamic exercise. The electromyographic signal confirms neuromuscular changes after endurance training.

We examined whether the neuromuscular function of rectus femoris (RF) and flexor digitorum brevis (FDB) in humans was modified after a 6-week training period of functional electrical stimulation (FES), and whether any effects persisted at the end of a 6-week post-FES recovery period. In both the stimulated and contralateral nonstimulated muscles, we recorded the muscle force, surface electromyogram, and M wave, and also measured the root mean square (RMS) and the median frequency (MF) during static contraction sustained until exhaustion at 60% of maximal voluntary contraction (MVC). FES was performed with symmetric biphasic pulses, with a ramp modulation of both the stimulation frequency and pulse duration. No changes in MCV and endurance time to exhaustion occurred in nonstimulated muscles, whereas a significant MVC increase occurred immediately after FES in RF (+14 +/- 5%) and FDB (+13 +/- 5%), these effects persisting 6 weeks after the end of FES. In FDB, FES also elicited a significant increase in endurance time to exhaustion (+18 +/- 7%). The M-wave characteristics never varied after FES, but a marked attenuation occurred in the MF decrease and the RMS increase measured at endurance time to sustained 60% MVC, especially in FDB, which contains the higher proportion of type II fibers. These data indicate that FES improves muscle function and elicits changes in central muscle activation. The benefits of FES were greater in FDB, which is highly fatigable, and persisted for at least a 6-week period.

International audience; The purposes of this study were (1) to determine the time sustained above 90% of VO2max in different intermittent running sessions having the same overall time run at the velocity (vVO2max) associated with VO2max, and (2) to test whether the use of a fixed-fraction (50%) of the time to exhaustion at vVO2max (Tlim) leads to longer time spent at a high percentage of VO2max. Subjects were 8 triathletes who, after determination of their track vVO2max and Tlim, performed three intermittent running sessions alternating the velocity between 100% and 50% of vVO2max, termed 30 s-30 s, 60 s-30 s, and 1/2 Tlim, where the overall time at vVO2max was similar (= 3 x Tlim). VO2max achieved in the incremental test was 71.1 +/- 3.9 ml.min-1.kg-1 and Tlim was 236 +/- 49 s. VO2peak and peak heart rate were lower in 30 s-30 s than in the other intermittent runs. The time spent above 90% of VO2max was significantly (p < 0.001) longer either in 60 s-30 s (531 +/- 187 s) or in 1/2 Tlim-1/2 Tlim (487 +/- 176 s) than in 30 s-30 s (149 +/- 33 s). Tlim was negatively correlated with the time (in % of Tlim) spent above 90% of VO2max in 30 s-30 s (r = -0.75, p < 0.05). Tlim was also correlated with the difference of time spent over 90% of VO2max between 60 s-30 s and 30 s-30 s (r = 0.77, p < 0.05), or between 1/2 Tlim-1/2 Tlim and 30 s-30 s (r = 0.97, p < 0.001). The results confirm that vVO2max and Tlim are useful for setting interval-training sessions. However, the use of an individualized fixed-fraction of Tlim did not lead to longer time spent at a high percentage of VO2max compared to when using a fixed work-interval duration.

We tested the hypothesis that prolonged administration of moderate doses of recombinant human erythropoietin (r-HuEPO) accelerates the initial rate of rise in pulmonary O2 uptake (VO2) in response to submaximal exercise and increases the maximal rate of O2 uptake (VO(2,max)). Sixteen endurance-trained athletes were divided into two groups: r-HuEPO- (n=9) or placebo-treated (n=7). r-HuEPO or placebo (saline) injections were given s.c. 3 times a week for 4 weeks. Exercise testing, before and after the 4 weeks, comprised incremental maximal tests and several transitions from rest to 10-min cycling exercise at 65% VO(2,max). VO2 was measured breath-by-breath during all tests. In the r-HuEPO group, resting haemoglobin concentration (+9.6%) and haematocrit (+8.3%), as well as VO(2,max) (+7.0%) and power output (+7.2%) increased significantly (P0.05) after the 4 weeks, whereas no change was observed in the control group. The time constant of the primary VO2 response was significantly faster (+18%) after the 4 weeks r-HuEPO treatment than before (mean+/-SD; 29.3+/-4.5 vs. 35.7+/-7.4 s, respectively, P0.05) but was unaffected in the placebo group (34.5+/-7.3 vs. 33.4+/-7.9 s). Collectively, our findings suggest that r-HuEPO contributes both to an acceleration of the dynamic response of VO2 to submaximal exercise and to an increase in maximal exercise capacity.

The training-performance relationship is particularly important for elite sports coaches who search for reproducible phenomena useful for organizing the athlete’s training program. Many authors have studied the relative influence of training (7, 22, 23, 27) and found that reactions to training depend on volume, intensity and frequency of the training sessions (7, 16, 23). Others have reported divergent results (4, 9), perhaps related to the fact that delayed effects and inter–individual differences were not taken into account. For individual swimmers, mathematical models have been developed to describe the dynamic aspect of training and the consequences of succession of training loads over time (2). The Banister model (2, 3, 4) and its modifications (5, 6) are based on two antagonistic functions, both calculated from the training impulse. Studies on cellular adaptability reactions to exercise (3) have demonstrated that the negative function can be assimilated to a fatiguing impulse. The positive function can be compared to a fitness impulse resulting from the organism’s adaptation to training. Expressed as an exponential, the functions account for the decreasing impact of the training effect. When iterative training sessions are considered, the time course of performance is described by: pt=p0+ka∑s=0t-1e-(t-s)/τaws-kf∑s=0t-1e-(t-s)/τfws where pt is the known performance at week (or day) t; ws is the known training load per week (or day) from the first week of training to the week (or day) preceding performance pt; ka, kf are the fitness and fatigue multiplying factors, respectively; τa, τf are the fitness and fatigue decay time constants, respectively; p0 corresponds to an initial basic level of performance. There is no clear consensus on just how many data points are needed per parameter to ensure a stable solution in a regression analysis. Proposals reported in the literature have ranged from 5 to 50. Stevens (26) recommends a nominal number of 15 observations per parameter (except the intercept parameter) for a multiple linear regression. But since the Banister model is a non-linear model, inference is based on asymptotic theory (10), which implies more data points per parameter than for a linear regression model. This means a large number of observations would be required to obtain precise results and enable pertinent statistical analysis. The Banister model also assumes the parameters remain constant over time, an assumption which is not consistent with observed time-dependent alterations in response to training (3, 4, 6, 22). When few repeated measurements are available for several subjects, mixed models provide an attractive solution (29). Instead of constructing a personal model for each subject, a model of popular behavior is constructed, allowing parameters to vary from one individual to another, to take into account the heterogeneity between subjects. Particular care in characterizing random variation in the data is required to recognize two levels of variability: random variation among measurements within a given individual (intra-individual variation) and random variation among individuals (inter-individual variation) (10). In addition, mixed models analyze responses corresponding to different dose inputs (10), a common situation in swimming since training loads differ with age, specialty, and/or competition level (7, 23). The aim of the present study was to investigate the effect of training on performance of 13 elite swimmers taking into account A) individual profiles; B) sub population profiles; and C) time effect over 3 seasons.

Chronic inactivity may not be the sole factor involved in the myopathy of chronic obstructive pulmonary disease (COPD) patients. One hypothesis is that exercise-induced oxidative stress that leads to muscle alterations may also be involved. This study investigated whether exercise localised to a peripheral muscle group would induce oxidative stress in COPD patients. Eleven COPD patients (FEV 1 1.15±0.4 L (mean±sd)) and 12 healthy age-matched subjects with a similar low quantity of physical activity performed endurance exercise localised to a peripheral muscle group, the quadriceps of the dominant leg. The authors measured plasma levels of thiobarbituric reactive substances (TBARs) as an index of oxidative stress, the release in superoxide anion (O 2 · − ) by stimulated phagocytes as an oxidant, and blood vitamin E as one antioxidant. Quadriceps endurance was significantly lower in the COPD patients compared with healthy subjects (136±16 s versus 385±69 s (mean±sem), respectively). A significant increase in TBARs 6 h after quadriceps exercise was only found in the COPD patients. In addition, significantly higher O 2 · − release and lower blood vitamin E levels were found in COPD patients than in controls at rest. This blood vitamin E level was significantly correlated with the resting level of plasma TBARs in the COPD patients. This study mainly showed that quadriceps exercise induced systemic oxidative stress in chronic obstructive pulmonary disease patients and that vitamin E levels were decreased in these patients at rest. The exact relevance of these findings to chronic obstructive pulmonary disease myopathy needs to be elucidated.

The aim of the present study was to evaluate the effect of an endurance training program on heart rate variability (HRV) in prepubertal healthy children and to determine the relationships between HRV components and training-induced cardiac adaptations.Nineteen prepubertal children (aged 10-11 years old) took part in this study: 12 children were assigned to participate in a 13-week endurance training program (3 x 1 h week-1; intensity,80% HRmax) and 7 children served as a control group. Before and after the 13-week study period, all the children were tested for maximal oxygen uptake (V O(2max)), HRV was measured by spectral and time domain analysis of 5 h night ECG recordings, and left ventricular (LV) cardiac morphology and function were assessed by means of Doppler-Echocardiography.V O(2max) increased significantly (+15.5% +/- 12.1; P0.01) after the training program. All the frequency domain components (absolute values) increased after training except the low (LF) to high (HF) frequency ratio. Also, LF and HF did not change when expressed relative to total power. For the time domain components, only N-N intervals, the standard deviation of all N-N and the average of all 5 min standard deviations of N-N increased after training. Our training program induced also an increase in LV internal diameter and mass as well as an enhancement in early diastolic passive LV filling with a concomitant reduction in late diastolic active LV filling. These cardiac morphological and functional adaptations did not correlate however, with the autonomous nervous system modifications due to training.Our study shows that an endurance training program had a positive effect on aerobic potential, morphological and functional cardiac parameters and on nocturnal global HRV in healthy prepubertal children without inducing sympathetic and parasympathetic modifications.

This work aimed at further investigating the mechanisms by which liver gluconeogenic capacity from alanine is improved after training in rats, with an isolated hepatocyte model. Compared with controls in hepatocytes from trained rats incubated with gluconeogenic precursors (20 mM), the glucogenic flux ( Jglucose) was increased by 64% from alanine (vs. 21% for glycerol, 18% for lactate-pyruvate 10:1, and 10% for dihydroxyacetone). Maximal intracellular alanine accumulation capacity was also increased by 50%. Further experiments conducted on perifused hepatocytes showed that the putative adaptation at the level of the phospho enolpyruvate-pyruvate cycle, which could be involved in the increased Jglucosefrom lactate-pyruvate, was not involved in the increased Jglucosefrom alanine after training. For alanine concentration higher than ∼1 mM, an increased flux through alanine aminotransferase appeared responsible for the increased Jglucose. This could, in turn, depend on an increased supply of cytosolic 2-oxoglutarate because of the higher mitochondrial respiration observed in hepatocytes from trained rats and the activation of the malate-aspartate shuttle. At lower alanine concentration, the increase in Jglucoseappeared to be entirely due to the improved transport capacity.

International audience; Previous studies suggested that certain lipid-lowering drugs such as statins suppress ubiquinone, affect mitochondrial function, and may have deleterious effect on skeletal or cardiac muscles with potentially serious clinical consequences, especially in patients with established coronary heart disease and left ventricular dysfunction. In this double-blind study, we assessed the effects of 20 mg simvastatin (S, n = 32) or 200 mg micronized fenofibrate (F, n = 32, control group) on rest and exercise left ventricular function in hypercholesterolemic survivors of a previous Q-wave acute myocardial infarction. Left ventricular radionuclide imaging was performed at rest and during submaximal exercise and global and segmental (nine segment regional wall-motion score) ejection fractions were measured before treatment and 12 weeks later. Serum ubiquinone was reduced after treatment (p = 0.03) in the S but not the F group, whereas total and low-density lipoprotein (LDL) cholesterol were significantly reduced in both groups. Before treatment, mean global ejection fraction was 52.1+/-12.2% and 49.3+/-11.8% at rest in F and S patients, respectively, and increased (56.0+/-13.7% in F and 52.1+/-12.9% in S) at peak exercise (no difference between groups). After treatment, the increase in ejection fraction tended to be lower in S (0) than in F (+3.8%) but not significantly. However, ejection fraction at rest increased after treatment in S (p = 0.009) but not in F. Subgroup analyses indicated that the improvement in rest ejection fraction in S was essentially observed in patients with ejection fraction 40% (+1.8%). Finally, the numbers of akinetic or hypokinetic segments at rest and during exercise were not different in the two groups before and after treatment. Mean maximal exercise load (113+/-23 watts in F vs. 104+/-27 W in S before treatment) was not modified by the treatment (111+/-21 and 104+/-27 W). Thus a 12-week lipid-lowering treatment with either S or F did not negatively alter left ventricular function during exercise in dyslipidemic patients with established coronary heart disease and did not affect their ability to exercise. The improvement in left ventricular function at rest after simvastatin in patients with left ventricular dysfunction warrants confirmation in further studies with large sample size.

Despite current discussions promoting physical and sports activities in asthmatics, no studies have yet been done on the possible pathophysiological justifications for rehabilitation by sports programs. Consequently asthmatics are retrained in an empirical fashion and the assessment of these programs is subjective. The aim of this article is thus to review the different studies concerning the adjustment of asthmatics to muscular exercise and to deduce from these what could or should be the pathophysiological objectives of reconditioning protocols. The principal ideas which emerge from this study derive from three fundamental facts: 1) the training of asthmatics should be based on an individual approach since clinical severity leads to very unequal adaptations during muscular exercise; 2) it is advisable to strive against the declining physical fitness of the asthmatics, which is responsible for the accelerated functional deterioration, disturbances of psychomotor development and an increased risk of exercise-induce asthma; 3) the decrease of excessive exercise hyperventilation is, from the evidence, the greatest priority among the pathophysiological objectives, because hyperventilation is a principal cause implicated in the disturbance of cardiovascular adjustments to effort by heart-lung interaction.

The aim of this study was to model the residual effects of training on the swimming performance and to compare a model that includes threshold saturation (MM) with the Banister model (BM). Seven Olympic swimmers were studied over a period of 4 +/- 2 years. For 3 training loads (low-intensity w(LIT), high-intensity w(HIT), and strength training w(ST)), 3 residual training effects were determined: short-term (STE) during the taper phase (i.e., 3 weeks before the performance [weeks 0, 1, and 2]), intermediate-term (ITE) during the intensity phase (weeks 3, 4, and 5), and long-term (LTE) during the volume phase (weeks 6, 7, and 8). ITE and LTE were positive for w(HIT) and w(LIT), respectively (p < 0.05). Low-intensity training load during taper was related to performances by a parabolic relationship (p < 0.05). Different quality measures indicated that MM compares favorably with BM. Identifying individual training thresholds may help individualize the distribution of training loads.

We questioned if a non-linear increase in ventilation defining a ventilatory threshold (V(Th)) accompanied the electromyographic (EMG) signs of neuromuscular fatigue. Indeed, the intramuscular accumulation of metabolites may activate the afferent nervous pathways responsible for both the 'muscle wisdom' phenomenon and the respiratory centre activation. During inframaximal (50%) handgrip sustained until exhaustion, minute ventilation (V(E)), V(E)/V(O2) and V(E)/V(CO2) ratios were measured simultaneously with surface EMG of the 'flexor digitorum' muscle. V(Th) was defined as a non-linear V(E) increase and/or an abrupt V(E)/V(O2) increase without any concomitant increase in the V(E)/V(CO2) ratio. Handgrip was repeated during complete arterial blood flow interruption in order to suppress any venous return from the exercising forearm. In both control and blood flow interruption conditions, an abrupt increase in the V(E)/V(O2) ratio was measured in the majority of trials (13 of 15 and 14 of 15, respectively) and the EMG signs of neuromuscular fatigue (a decline in median frequency and/or a non-linear increase in low-frequency EMG energies, E(L)) were concomitant with the V(Th) determination. Thus, V(Th) occurs during sustained static contraction and is concomitant with EMG signs of neuromuscular fatigue. Neurogenic factors seem to be responsible for the two responses which persist despite the absence of any release of metabolites in the circulation.