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P Legros

Publications and source records attributed to P Legros.

At least 19 recordsLinked to original sources
PubMed2006

Time course of mechanical and neuromuscular characteristics of cyclists and triathletes during a fatiguing exercise.

This study examined the impact of sport specificity on the time course of fatigue during maximal voluntary eccentric, concentric and isometric torque production following a submaximal isokinetic fatiguing exercise. Seven cyclists and seven triathletes performed a fatiguing exercise consisting of nine sets of 31 isokinetic concentric knee extensions at 1.05 rad . s (-1). Fatigue was assessed pre-exercise, after three and six sets, and post-exercise. The maximal knee extension torque associated with electromyographic (EMG) activity was recorded during voluntary contractions and electrically induced contractions (single and paired twitches). The maximal voluntary eccentric torque production declined in cyclists (18 +/- 3.5 %, p < 0.05) and was not significantly affected in triathletes (5 +/- 2.5 %, p > 0.05). The decrease in cyclists was associated with an increase in the sum of the normalized EMG (nRMS) values of the three agonist muscles (p < 0.01). Although no significant difference was observed between groups, the two-way repeated-measure analysis of variance revealed a time effect on maximal concentric and isometric torque, twitch contractile and electrophysiological response (M (max)) properties. No modification in the activation and coactivation levels was observed. In conclusion, these results indicate that the time course of fatigue, especially during eccentric contractions, is mediated by sport-specific adaptations likely due to the mode of muscle contraction used in the activity.

Adult↗
PubMed2006

[Female prostitutes in Phnom Penh, Cambodia: changes in knowledge, attitudes and practices between 2000 and 2004].

A survey was carried out to evaluate the knowledge, attitudes and practice of female prostitutes In Phnom Penh (Cambodia) in 2000 and 2004. A total of 131 women were included both years. The population was 75% Cambodian and 25% Vietnamese. Average age was 22.9 years in 2000 and 25.5 years in 2004. Sixty-seven percent of the women surveyed stated that prostitution was a "voluntary" choice. The awareness rate for sexual transmitted diseases (STD) including AIDS and its main clinical signs and of the protective value of condoms was 90% in 2000 and 96% in 2004. However 30% reported unprotected sexual relations with at least one of their last 10 clients. Twenty-five percent performed oral sex usually without precaution. Drug use was limited to methamphetamines. Monthly income ranged from 15 dollars to 22.5 dollars (mean, 66 dollars). This amount is higher than the salary of a factory worker. Despite good knowledge of STD and prevention measures, prostitutes in Phnom Penh appear to have unsafe sexual practices.

Adult↗
PubMed2003

Night heart rate variability during overtraining in male endurance athletes.

AIM: The purpose of the study was to examine whether an unaccustomed increase in training volume would result in characteristics changes in heart rate variability (HRV), in order to determine if this marker can be used to diagnose overtraining. METHODS: Nine experienced endurance athletes increased their usual amount of training by 100% within 4 weeks. Night ECG was recorded before (baseline) and after (OVER) this period of overload, and after 2 weeks of recovery (REC). RESULTS: We diagnosed overtraining in 6 subjects using both physiological and psychological criteria. No difference was noted in heart rate for night periods (56+/-12, 55+/-10 and 53+/-15 bpm, respectively; p>0.05). We found no significant changes of LF/HF (1.10+/-0.92, 0.96+/-0.57 and 0.59+/-0.43, respectively; p>0.05) or HF expressed in normalized units (54.81+/-20.12, 53.81+/-11.35 and 66.15+/-15.12%, respectively; p>0.05). CONCLUSION: In the conditions of the present study, HRV during sleep does not seem to be a valid marker of overtraining in male endurance athletes. Before concluding to the uselessness of this tool in the monitoring of the syndrome, longitudinal studies with elite or sub-elite athletes are needed to determine if spontaneously developed overtraining results in the same response.

Adult↗
PubMed2002

SEMG power spectrum changes during a sustained 50% Maximum Voluntary Isometric Torque do not depend upon the prior knowledge of the exercise duration.

Endurance time (Tlim) is a relevant indicator of muscular resistance to fatigue. It has been recently shown that SEMG changes computed during shorter periods (sub-maximal durations) than the whole test duration could serve to predict Tlim. The aim of the present study was to test whether the prior knowledge of the sub-maximal duration had any influence on Tlim prediction throughout SEMG changes. For this purpose, we compared myoelectric changes estimated over a 30-s isometric contraction whose duration was known by the subjects, to those changes measured during the first 30 s of a test prolonged until exhaustion. The effort intensity was set at 50% of the maximal voluntary isometric torque (MVIT). The myoelectric manifestations of muscle fatigue appeared to change in a similar way during both sessions for temporal and spectral analyses. In conclusion, the prior knowledge of the duration of sustained isometric contraction did not influence the motor unit recruitment strategy throughout surface EMG evaluation. These results confirmed that the use of SEMG changes computed over shorter periods than expected endurance time may be applied to investigate the capability of the initial rate of SEMG changes to predict muscle endurance capacity at 50%MVIT. This may be of particular interest for patient evaluation in the clinical field.

Adult↗
PubMed2001

Effects of inhaled salbutamol in exercising non-asthmatic athletes.

BACKGROUND: Beta-2 agonists such as salbutamol are used, not only by asthmatic athletes to prevent exercise induced asthma, but also by non-asthmatic athletes as a potentially ergogenic agent. We have investigated whether inhaled salbutamol enhances endurance performance in non-asthmatic athletes. METHODS: A prospective double blind, randomised, three way crossover design was used to study the effects of 200 microg and 800 microg inhaled salbutamol versus a placebo in 12 trained triathletes. The treatments were compared in three identical cycle ergometer sessions at 85% of the predetermined maximal oxygen uptake. Lung function, endurance time, metabolic parameters (glucose, potassium, lactate, free fatty acid, and glycerol), and psychomotor performance were evaluated. RESULTS: Neither endurance time nor post-exercise bronchodilation were significantly different between the treatments. Metabolic parameters were affected by exercise but not by treatment. CONCLUSIONS: Inhaled salbutamol, even in a high dose, did not have a significant effect on endurance performance in non-asthmatic athletes, although the bronchodilating effect of the drug at the beginning of exercise may have improved respiratory adaptation. Our results do not preclude an ergogenic effect of beta2 agonists given by other routes or for a longer period.

Administration, Inhalation↗
PubMed1999

Antioxidants and mitochondrial respiration in lung, diaphragm, and locomotor muscles: effect of exercise.

Previous studies have shown that exhaustive exercise may increase reactive oxygen species (ROS) generation in oxidative muscles that may in turn impair mitochondrial respiration. Locomotor muscles have been extensively examined, but there is few report about diaphragm or lung. The later is a privileged site for oxygen transit. To compare the antioxidant defense system and mitochondrial function in lung, diaphragm and locomotor muscles after exercise, 24 young adult male rats were randomly assigned to a control (C) or exercise (E) group. E group rats performed an exhaustive running test on a motorized treadmill at 80-85% VO2max Mean exercise duration was 66+/-2.7 min. Lung, costal diaphragm, mixed gastrocnemius, and oxidative muscles (red gastrocnemius and soleus: RG/SOL homogenate) were sampled. Mitochondrial respiration was assessed in tissue homogenates by respiratory control index (RCI: rate of uncoupled respiration/rate of basal respiration) measurement. Lipid peroxidation was evaluated by malondialdehyde concentration (MDA) and we determined the activity of two antioxidant enzymes: superoxide dismutase (SOD) and glutathione peroxidase (GPX). We found elevated basal (C group data) SOD and GPX activities in both lung and diaphragm compared to locomotor muscles (p<.001). Exercise led to a rise in GPX activity in red locomotor muscles homogenate (GR/SOL; C = 10.3+/-0.29 and E = 14.4+/-1.51 micromol x min(-1) x gww(-1); p<.05), whereas there was no significant change in lung and diaphragm. MDA concentration and mitochondrial RCI values were not significantly changed after exercise. We conclude that lung and diaphragm had higher antioxidant protection than locomotor muscles. The exercise test did not lead to significant oxidative stress or alteration in mitochondrial respiration, suggesting that antioxidant function was adequate in both lung and diaphragm in the experimental condition.

Animals↗
PubMed1999

Foci of Schistosomiasis mekongi, Northern Cambodia: II. Distribution of infection and morbidity.

In the province of Kracheh, in Northern Cambodia, a baseline epidemiological survey on Schistosoma mekongi was conducted along the Mekong River between December 1994 and April 1995. The results of household surveys of highly affected villages of the East and the West bank of the river and of school surveys in 20 primary schools are presented. In household surveys 1396 people were examined. An overall prevalence of infection of 49.3% was detected by a single stool examination with the Kato-Katz technique. The overall intensity of infection was 118.2 eggs per gram of stool (epg). There was no difference between the population of the east and west shore of the Mekong for prevalence (P = 0.3) or intensity (P = 0.9) of infection. Severe morbidity was very frequent. Hepatomegaly of the left lobe was detected in 48.7% of the population. Splenomegaly was seen in 26.8% of the study participants. Visible diverted circulation was found in 7.2% of the population, and ascites in 0.1%. Significantly more hepatomegaly (P = 0.001), splenomegaly (P = 0. 001) and patients with diverted circulation (P = 0.001) were present on the west bank of the Mekong. The age group of 10-14 years was most affected. The prevalence of infection in this group was 71.8% and 71.9% in the population of the West and East of the Mekong, respectively. The intensity of infection was 172.4 and 194.2 epg on the West and the East bank, respectively. In the peak age group hepatomegaly reached a prevalence of 88.1% on the west and 82.8% on the east bank. In the 20 schools 2391 children aged 6-16 years were examined. The overall prevalence of infection was 40.0%, ranging from 7.7% to 72.9% per school. The overalls mean intensity of infection was 110.1 epg (range by school: 26.7-187.5 epg). Both prevalence (P = 0.001) and intensity of infection (P = 0.001) were significantly higher in schools on the east side of the Mekong. Hepatomegaly (55.2%), splenomegaly (23.6%), diverted circulation (4. 1%), ascites (0.5%), reported blood (26.7%) and mucus (24.3%) were very frequent. Hepatomegaly (P = 0.001), splenomegaly (P = 0.001), diverted circulation (P = 0.001) and blood in stool (P = 0.001) were significantly more frequent in schools of the east side of the Mekong. Boys suffered more frequently from splenomegaly (P = 0.05), ascites (P = 0.05) and bloody stools (P = 0.004) than girls. No difference in sex was found for the prevalence and intensity of infection and prevalence of hepatomegaly. On the school level prevalence and intensity of infection were highly associated (r = 0. 93, P = 0.0001). The intensity of infection was significantly associated only with the prevalence of hepatomegaly (r = 0.44, P = 0. 05) and blood in stool (r = 0.40, P = 0.02). This comprehensive epidemiological study documents for the first time the public health importance of schistosomiasis mekongi in the Province of Kracheh, Northern Cambodia and points at key epidemiological features of this schistosome species, in particular the high level of morbidity associated with infection.

Adolescent↗
PubMed1998

Variability in energy cost and walking gait during race walking in competitive race walkers.

PURPOSE: The aim of this study was to examine the variability of energy cost (Cw) and race walking gait after a 3-h walk at the competition pace in race walkers of the same performance level. METHODS: Nine competitive race walkers were studied. In the same week, after a first test of VO2max determination, each subject completed two submaximal treadmill walks (6 min length, 0% grade, 12 km X h(-1) speed) before and after a 3-h overground test completed at the individual competition speed of the race walker. During the two submaximal tests, subjects were filmed between the 2nd and the 4th min, and physiological parameters were recorded between the 4th and the 6th min. RESULTS: Results showed two trends. On the one hand, we observed a significant and systematic increase in energy cost of walking (mean deltaCw = 8.4%), whereas no variation in the gait kinematics prescribed by the rules of race walking was recorded. On the other hand, this increase in metabolic energy demand was accompanied by variations of different magnitude and direction of stride length, of the excursion of the heel and of the maximal ankle flexion at toe-off among the race walkers. CONCLUSION: These results indicated that competitive race walkers are able to maintain their walking gait with exercise duration apart from a systematic increase in energy cost. Moreover, in this form of locomotion the effect of fatigue on the gait variability seems to be an individual function of the race walk constraints and the constraints of the performer.

Adult↗
PubMed1996

Effect of three hours race walk on energy cost, cardiorespiratory parameters and stride duration in elite race walkers.

The purpose of this study was to quantify changes in energy cost of walking (C), ventilation (VE), respiratory frequency (RF), heart rate (HR), expiratory ratio (RER), blood lactate concentration (LA), body mass (W) and stride duration (SD) after a 3 hour race walk at competition pace in elite race walkers. Subjects were tested during 2 submaximal treadmill tests at 12.2 +/- 0.5 km.h(-1) (74.7% VO2max speed) before and after a 3 hour overground walk. Significant increases (p < 0.05) were found in C, HR and significant decreases were found in RER, W, VE whereas no changes were observed in LA or SD (means and intra-subject variability). However, a wide range of individual coefficients of variation were observed for C, VE, RF, HR, SD, W. These results suggest that in well trained walkers the energy cost of walking increases with exercise duration but that walkers are able to maintain the same stride duration after the test when treadmill speed is controlled. Furthermore, some individuals appear to be more sensitive to fatigue. Discussion set out a possible effect of substrate utilisation changes, thermoregulation or a decrease in mechanical efficiency for maintaining the race walk gait apart from the effect of fatigue.

Adult↗
PubMed1996

Running economy, preferred step length correlated to body dimensions in elite middle distance runners.

The purpose of this research was to study the relationship between running economy, step length, and body dimensions. Elite middle distance runners were tested for one high submaximal volocity very close to usual training speeds, near the anaerobic threshold (15 km.h-1) and one low submaximal velocity very different to usual training speeds, near the speed transition between walking and running (9 km.h-1). All the subjects were selected after a maximal protocol to be homogeneous on VO2max (65.7 +/- 2.3 ml.kg-1.min-1). Then they were monitored during two submaximal tread-mill tests at 54.4 +/- 2.2% (9 km.h-1) and 78.5 +/- 3.9% VO2max (15 km.h-1). Body weight, body fat, height, sitting height, low extremity length (height - sitting height), relative low extremity length, leg length, thigh length, foot length were determined. The results indicate an effect of the running speed on the relationship between body dimensions, step length and VO2. The relation was inverse between running economy, body dimensions at 9 and 15 km.h-1 and no significant correlation was found for running economy between these two speeds. Furthermore, the mode of expressing VO2 in ml.kg-0.75.min-1 affects these relations. Thus, this result allows us to make the assumption that mechanisms of adaptation can be different according to the running speed, and the specific constraints that it represents for each subject.

Adipose Tissue↗
PubMed1995

Use of energy cost and variability in stride length to assess an optimal running adaptation.

The aim of this study was to analyse how subjects' running adaptation was affected after a training overload. 14 middle-distance runners were tested before and after a training protocol of 15 days conducted only at one training pace. The efficacy of this training protocol to improve energy cost of running was observed only at the training pace. This improvement was correlated with a particular systematic variation in stride length whereas no changes in stability of stride length were recorded. The data were interpreted in terms of specificity of training for which energy cost and stability of stride length could be considered criteria of an optimal adaptation to the training pace.

Adult↗
PubMed1994

Daily stability in energy cost of running, respiratory parameters and stride rate among well-trained middle distance runners.

The purpose of this study was to quantify total intraindividual variability in energy cost of running (C), ventilation (VE), respiratory frequency (RF), heart rate (HR), lactate concentration (La) and stride rate (SR) at usual training pace in French elite middle distance runners. Subjects were monitored four times a week during submaximal treadmill tests at 75% VO2max speed (15.8 +/- .02 km.h-1). No significant differences (p > .05) were found between tests in C, VE, RF, HR, SR. Significant day to day differences were found in La (0.5 +/- 0.3, p < .025). However, a wide range of individual coefficients of variation were observed for C (0.2-10.6), VE (0.9-8.8) and RF (0.7-9.3). SR appears to be the most stable parameter (0.2-2.6). No correlation was found between these individual variations. These results suggest that in well-trained runners C, VE, RF, HR and SR are stable measures for assessing the efficacy of procedures aimed at improving the energy cost of running. For the speed used in testing, the respiratory parameters and energy cost of running presented a wide range of individual variation whereas stride rate appeared to be a very stable measure.

Adult↗
PubMed1994

Self-perception of fitness and personality traits.

Our aim was to analyze how subjects perceive their own physical fitness. In Study 1 the 247 subjects assessed their own fitness, endurance, strength, flexibility, and body composition according to specific category scales. Analyses showed that self-perceived physical fitness was mainly related to perceived cardiovascular endurance. According to sex and age, strength, flexibility, and body composition could have a significant influence. The scores obtained on the five scales were highly correlated, suggesting they were overdetermined by a more general factor assimilated to physical self-worth. In Study 2 the 91 subjects completed the same five scales, the Spielberger State-Trait Anxiety Inventory, the Coopersmith Self-esteem Inventory, and the Bem Sex-role Inventory. Results confirmed the hierarchical model of Fox and Corbin (1989) and showed that physical self-worth is related to self-esteem, anxiety, and masculinity.

Adult↗
PubMed1994

Variability in energy cost of running during one training season in high level runners.

The purpose of this study was to investigate the effect of training specificity on a possible change in the energy cost of running over a period of one training season in high level competition runners. Four middle distance and four long distance runners participated in treadmill tests on three sessions after a specific training period. In each session, every subject participated in two tests to determine, in the first test the maximal oxygen consumption and in the second test the energy cost of running. The second test was performed at 60% and 80% of Vmax (maximal speed reached during the first test, respectively 12 and 16 km.h-1), and at 0% grade. The maximal oxygen uptake (VO2max, ml.kg-1.min-1) increased significantly between the first and the last session (p < 0.05). For all the tests, long distance runners showed higher values of VO2max than middle distance runners (p < 0.001). During the year, there were no significant changes in energy cost (C, ml/kg-1.km-1) between the first and the last session (respectively at 60% and 80% vmax: 165 +/- 5.8 vs 164 +/- 4.9 and 167.5 +/- 3.5 vs 166.8 +/- 3.3), and no differences were found between middle and long distance runners. An addition, no changes were found in lactate concentration or in respiratory exchange ratio during all the training season. Discussion set out the difficulty to conclude to a stability in energy cost of running. First by the fact that the energy cost reflects both positive and negative effects of training.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Long-term relationship between acute rhabdomyolysis and abnormal high-energy phosphate metabolism potentiated by ischemic exercise.

Relative concentrations of inorganic phosphate [Pi]r, creatine phosphate [CP]r, adenosine triphosphate [ATP]r, and intracellular pH (pHi) were determined by 31P-NMR spectroscopy in the flexores digitorum muscles. The measurements were performed at rest, during bouts of rhythmic exercises at different powers, including one with restricted blood supply, and during recovery. Normal subjects (N) and subjects with previous histories of exercise hyperthermia (EH) were compared. No significant difference was found between N and EH subjects at rest. During exercise [ATP]r was not affected, except in EH subjects exercising under partial muscle ischemia (P less than 0.001); in both N and EH, [CP]r and pHi decreased, and the higher the load the more pronounced the reduction. These changes were significantly larger in EH patients than in N (P less than 0.05), and the differences were dramatically increased by reducing blood supply (P less than 0.001). During recovery, the return to the control values was much slower in EH patients than in N, in particular for pHi after the exercise under partial ischemia. In conclusion, the fact that metabolic disorders are still patent long after the EH occurrence supports the possibility of latent myopathy and of a persistent metabolic disorder. Thus, 31P-NMR spectroscopy could be a useful noninvasive test to detect EH susceptibility in at-risk subjects.

Acute Disease↗
PubMed1990

Does arterial PCO2 interfere with hypoxia in muscular metabolism in man?

To answer the question whether PCO2 affects the muscular metabolism, PO2, PCO2, pH, lactic acid concentration and hemoglobin were measured in the efferent muscular venous blood from common flexor digitorum, during forearm rhythmic exercise corresponding to VO2max. Exercise was carried out either in hypocapnic hypoxia i.e. in permanent high altitude residents and translocated lowlanders, or in hypercapnic hypoxia i.e. in chronic obstructive lung disease (COLD) patients. The results show that, during exercise: i) PO2 in muscular venous blood remains around 20 Torr in normoxia and hypocapnic hypoxia and even higher (25 torr) in COLD patients, despite low arterial PaO2, and ii) arterial and/or local PCO2 play a role in the control of the muscular blood flow. But we cannot conclude that a change in PaCO2 affects muscular metabolism itself, because lactic acid in the muscular venous blood, that we used to check this effect, is likely dependent on mechanisms other than anaerobic glycolysis, such as a change in lactic acid efflux from the myocytes. The increase in muscular venous PCO2 may enhance the myocyte permeability to lactic acid during exercise.

Acclimatization↗