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Biomedical subjects

J Coudert

Publications and source records attributed to J Coudert.

At least 55 records · Page 3Linked to original sources
PubMed1994

Blood lactate after maximal and supramaximal exercise in 10- to 12-year-old Bolivian boys. Effects of altitude and socioeconomic status.

The aim of this paper was to analyze the effects of chronic hypoxia and socioeconomic level on blood lactate concentrations obtained after maximal exercise and a 30-s Wingate test in 145 Bolivian boys (mean age: 10.8 years). Among the boys studied at high altitude (HA) (La Paz, 3600m) and at low altitude (LA) (Santa Cruz de la Sierra, 420m), 23 (HAHSES) and 48 (LAHSES) were from a high socioeconomic status (HSES), and 44 (HALSES) and 30 (LALSES) from a low socioeconomic status (LSES). The pubertal development was evaluated by salivary testosterone level ([T]). Blood samples were collected from the earlobe for blood lactate determination 2 min after cessation of maximal exercise ([L]v) and of a 30-s Wingate test ([L]w). Results (means +/- SD) showed: (1) [T] was significantly lower at HA: HA (HSES + LSES): 139.0 +/- 46.6 vs LA (HSES + LSES) = 186.2 +/- 53.7 pmole.1-1 (p = 0.0001). There was no significant difference between HAHSES and HALSES but LALSES was significantly lower than LAHSES. When the four groups were pooled, significant positive correlations between [L] and [T] were found; (2) for a same level of socioeconomic conditions, [L]v and [L]w were significantly lower at HA: HAHSES = 4.9 +/- 1.5 vs LAHSES = 7.4 +/- 2.1 and HALSES = 4.8 +/- 1.4 vs LALSES = 6.3 +/- 1.5 mmole.l-1 for [L]v; HAHSES = 5.1 +/- 1.0 vs LAHSES = 6.2 +/- 1.4 and HALSES = 4.6 +/- 1.0 vs LALSES = 5.3 +/- 1.4 mmole.l-1 for [L]w; (3) except for [L]v at HA, the HSES boys exhibited higher [L]v and [L]w than the LSES children for a same altitude; (4) there were significant linear relationships between the power developed during the 30-s Wingate test and [L]w.(ABSTRACT TRUNCATED AT 250 WORDS)

Altitude↗
PubMed1994

Habitual physical activity in 10- to 12-year-old Bolivian boys. The relation between altitude and socioeconomic status.

This study describes habitual physical activity (HPA) of Bolivian boys living at different altitudes and from different socioeconomic status. The boys were living at high altitude (HA) in La Paz (4000 m) and at low altitude (LA) in Santa Cruz (400 m). At both altitudes samples of 10- to 12-year-old boys were chosen from a relatively low socioeconomic status (LSES) and a relatively high socioeconomic status (HSES). At HA 19 boys from LSES and 10 boys from HSES were measured and at LA 14 boys from LSES and 13 boys from HSES. HPA was measured by 24-h heart rate (HR) monitoring. Also an interview was completed to recall the HPA. By comparing the registered HR data with the time they were asleep the mean HR during sleep was calculated (HRsleep). The maximal HR (HRmax) was measured from a maximal exercise test on a bicycle ergometer. Heart rate reserve (HRR = HRmax-HRsleep) was used to measure the mean level of physical activity of the subjects. The results show that HRsleep (= HRrest) in HA boys with 70 (+/- 6) beats/min was significantly lower (p < 0.05) than in LA boys with 77 (+/- 10) beats/min. HRmax was also significantly lower (p < 0.05) in HA boys (187 +/- 12 beats/min) compared to LA boys (195 +/- 8 beats/min). Because HA influences HRsleep and HRmax in the same way, HRR is not significantly different between boys of HA and LA. The mean heart rate over 24 h (HRmean) in HA boys (87 +/- 7 beats/min) was significantly lower than in LA boys (93 +/- 8 beats/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Altitude↗
PubMed1994

Effects of orchiectomy on EDL muscle ultrastructure and energy-supplying enzymes in growing male guinea pigs.

To investigate the influence of androgens on muscle maturation during growth, guinea pigs were orchiectomized (CX) or sham operated (SO) at the end of weaning. Extensor digitorum longus (EDL) muscles were removed at weeks 4, 8, and 12 of postnatal development. According to their contractile and metabolic characteristics, four fiber types were distinguished, called I, IIa, IIbox, and IIbglyc. Muscle maturation consisted of a concomitant decrease in percentages of type IIa and IIbglyc fibers and increase in the percentage of IIbox fibers in both groups. At week 12, fiber distributions were not different between the two groups. Citrate synthase activity fell and phosphofructokinase and lactate dehydrogenase (LDH) activities rose from week 4 to week 12 and were the same in CX and SO. Muscular LDH subunits increased in SO and decreased in CX during this period. In conclusion, fiber type distribution and enzyme activities at puberty were not androgen dependent in guinea pig EDL muscle. Conversely, these hormones acted on LDH isozyme distribution through the enhancement of the most glycolytic LDH fractions.

Aerobiosis↗
PubMed1994

[Physiology of muscular exercise in children].

When compared to adults, muscle mass in children is lower and the relative development of aerobic and anaerobic pathways is different. The main consequences are the following: 1) The aerobic metabolism, evaluated by measurement of maximal oxygen uptake (VO2max), is either the same as in adults or more developed when VO2 max is related to body mass or lean body mass. 2) The maximal anaerobic power developed during force-velocity test and Wingate test is lower than in adults even if it is expressed by total or lean body mass unit. Blood lactate concentration is also lower. This immaturity of the anaerobic metabolism, especially the "lactic pathway" may result from lower anaerobic enzyme activities (lactico-dehydrogenase, phosphofructokinase, etc) and glycogen content. During puberty, "lactic metabolism" starts to develop significantly, simultaneously with muscle mass. It has been suggested that sexual hormones (testosterone in boys, oestrogens in girls) and other factors, such as growth factors, are implicated in this phenomenon. During this period, the aerobic metabolism remains unchanged. In prepubertal children there is neither aerobic nor anaerobic specialization: the highest anaerobic performance is associated with the highest VO2 max. Moreover, it seems that before puberty, bioenergetic profile is not modified by training. 3) Despite a high VO2 max, performance in endurance events is not as high in children as in adults because of a lower running economy. Cardiovascular responses are characterized by higher maximal and infra-maximal heart rates, and lower systolic stroke volume and arterial blood pressures than in adults. During prolonged exercise, the hormonal adaptations for energy substrate utilization is quite different from adults: a lower decrease in insulin and increase in catecholamines and glucagon in response to exercise could be responsible for a less effective regulation of glycemia with a risk of hypoglycemia. Therefore, an adequate carbohydrate intake is recommended.

Adolescent↗
PubMed1993

Analysis of performance of prepubertal swimmers assessed from anthropometric and bio-energetic characteristics.

The relationship between anthropometric and bio-energetic data and timed performance over 50 to 400 m was studied in 25 young male swimmers [11.3 (SD 1) years]. Anthropometric measurements included height, body mass, body fat mass, body area, thoracic section area (Ats) thoracic circumferences, lengths of upper limb, bi-acromial and bi-iliac diameters. Maximal oxygen consumption (VO2max; direct method), maximal anaerobic power (W(an),max; force-velocity test) and mean power in 30 s sprint (W30 s; Wingate test) were also measured. Each of these bio-energetic variables was expressed in absolute terms, relating to body mass, body area and Ats. The stepwise regression method was used to determine contribution of the variables (anthropometric and/or bio-energetic) of the time achieved over the distance. The W30 s/Ats accounted for 46% of the time over 50 m (negative correlation). The VO2max/Ats and height were negatively correlated with the times of performances over 100 m, 200 m and 400 m, these two variables accounted for 71% to 77% of the performance. These results would indicate that even in young boys, anthropometric and bio-energetic characteristics are both important in swimming performance, particularly the bio-energetic variables expressed per Ats.

Body Composition↗
PubMed1993

Bioenergetic characteristics in prepubertal swimmers. Comparison with active and non-active boys.

The effects of physical activity (PA) on bioenergetic characteristics were studied in 53 prepubertal boys. Maximal oxygen consumption (VO2max; direct method), maximal anaerobic power (Pmax, force-velocity test), and mean power in 30 s (P30s, Wingate test) were compared (mean +/- SD) in three groups of boys of the same age (11 years): swimmers (Sw, n = 26, PA = 8 +/- 3 hrs/week), active boys (A, n = 16, PA = 7 +/- 2 hrs/week) and non-active boys (C, n = 11, PA = 3 +/- 2 hrs/week). No significant difference appeared between groups for VO2max (Sw, 50.7 +/- 5.4; A, 50.8 +/- 6.0; C, 49.4 +/- 7.0; ml.min-1 x kg-1), Pmax (Sw, 8.1 +/- 1.4; A, 8.4 +/- 1.4; C, 8.1 +/- 1.4; W.kg-1) and P30s (SW, 5.8 +/- 1.0 A, 6.3 +/- 1.7; C, 5.0 +/- 1.1; W.kg-1). Significant relationships (p < 0.01) existed between Pmax, P30s (W.kg-1) and VO2max (ml.min-1 x kg-1): r = 0.37 and r = 0.40, respectively. This indicates that there is neither aerobic nor anaerobic specialization during prepubertal development, and that regular sporting activity induces no great changes in the bioenergetic characteristics of prepubertal boys.

Child↗
PubMed1993

Chemical and nonchemical stimuli during breath holding in divers are not independent.

In the breath-hold model described by S. Godfrey and E. J. M. Campbell (Respir. Physiol. 5: 385-400, 1968), chemical and nonchemical stimuli are independent. Because these two factors are time dependent, the effect of each could not be measured by breath-holding time (BHT). The aim of this study is to dissociate chemical and nonchemical stimuli and to assess the effects of BHT and PCO2 on respiratory center output by measurement of occlusion pressure (P0.1) and mean inspiratory flow (VI). Nine well-trained divers (age 36.5 +/- 5.0 yr) took part in the study. Each subject had to hold his breath at 75% of vital capacity for 30, 50, and 70 s of BHT. Before each breath hold, the subject inspired successively two vital capacities of the same CO2-O2 gas mixture. P0.1 and VI were measured during the first reinspiration after the breath hold. For the same BHT, we observed good linear relationships between P0.1 or VI and alveolar PCO2. The slopes of these relationships increased with BHT. For alveolar PCO2 of > 50 Torr, P0.1 increased linearly with BHT. These results indicate that, during breath holding, chemical and nonchemical stimuli acted linearly on respiratory motoneuron activity, but they were not independent.

Adult↗
PubMed1992

Inter-relationships between pituitary-adrenal hormones and catecholamines during a 6-day Nordic ski race.

The aim of the study was to investigate the inter-relationships between pituitary-adrenal hormones and catecholamines during a prolonged competition over 6 days. Plasma adrenocorticotropic hormone (ACTH), cortisol (C), beta-endorphin (beta EP), free and sulphated adrenaline (A) and noradrenaline (NA) were measured in 11 volunteer male subjects during a national Nordic-ski race (323 km). Blood samples were obtained before the competition in the evening as control (D0), and before and after each day's racing (D1-D6). The mean daily heart rate (fc) was calculated from fc values recorded every minute during the race. The results showed the following: changes in mean fc [from 147 (SEM 3) to 156 (SEM 3) beats.min-1 according to the day] were not significant during the race. Diurnal variations in ACTH, beta EP and C were no longer apparent after the race: evening levels were higher than their respective D0 values during the race, except on D3 when there was a lack of response to exercise in the three hormones. Unlike ACTH and beta EP, pre- and postexercise C values on D1 and D2 were higher than those on the subsequent days (P less than 0.001). In contrast, there was a progressive accumulation of A and NA in pre- and postrace concentrations which reached a plateau in about 4 days. Positive correlations between exercise responses in ACTH, C and beta EP were found especially on D3 and D6 (P less than 0.001) but there were no significant correlations between catecholamines and the other three hormones. Thus, prolonged competition over 6 days evoked different control mechanisms for hormones of the pituitary-adrenal axis and catecholamines.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex Hormones↗
PubMed1992

A simple calibration method for mechanically braked cycle ergometers.

The calibration of cycle ergometers should be checked regularly. Some studies have shown calibration errors of more than 40%. A simple, inexpensive calibrating method for mechanically braked cycle ergometers was developed and tried out on a new type of ergocycle. The cycle ergometer was elevated and the crank replaced by a pulley fitted to the shaft. The crank speed (rpm) increased linearly as a function of time when different masses were applied on the pulley. For a given braking force on the cycle ergometer, different accelerations corresponding to the increased pulley forces could be measured. When extrapolating for zero acceleration, it was possible to determine a "limit-force" which allowed the system to be in equilibrium. Additional force creates motion. The same experiments were repeated with increasing braking forces. Using the differently sized gear sprockets of the transmission system, it was possible to calculate the actual force, including all the resistances. The actual force found by the calibrating method was then compared with the indicated force proposed by the manufacturer. With increasing forces, the relative errors decreased from 9.6 to 2.9%. The cycle ergometer calibrated by this technique meets the standards recommended in exercise physiology.

Calibration↗
PubMed1992

Bioenergetic characteristics of swimmers determined during an arm-ergometer test and during swimming.

The maximal oxygen uptake (VO2max) of 13 swimmers was determined by an arm-ergometer test (direct method) and estimated from a maximal multistage swimming test (indirect method) (23). A test-retest of the progressive swimming exercise showed that there were no significant differences from one test to the other and that there were significant correlations between the principal parameters: arm stroke index: 0.73, maximal aerobic swimming velocity: 0.94, VO2max: 0.95, p less than 0.01. Therefore, for swimmers of average ability, the reproducibility of this test has been proved. A significant difference (p less than 0.001) was observed between the two tests for VO2max: arm-ergometer test (VO2max arms): 2.4 +/- 0.5 l.min-1, swimming test (VO2max ST): 3.2 +/- 0.7 l.min-1, p less than 0.01. This difference appeared to be linked to the use of a greater muscle mass (arms and legs) during swimming. A significant correlation (r = 0.73, p less than 0.01) was obtained between VO2max (l.min-1) by using both the direct and indirect exercises as methods of measurement. However, the level of r did not permit the prediction of one parameter from the other. Significant correlations were obtained between VO2max and performances over 200 and 400 m free style regardless of the methodology used (VO2max arm, VO2max ST). Moreover, only VO2max (arm, ST) emerged as a variable accounting for swimming performance from a step-wise multiple regression analysis, in which biometric and bioenergetic parameters were taken into account.

Adolescent↗
PubMed1992

Anaerobic performance at altitude.

Anaerobic metabolism is usually evaluated by the determination of the anaerobic capacity and the maximal anaerobic mechanical external power (Wmax). Conflicting results are reported on anaerobic capacity evaluated by maximal oxygen deficit and debt, and maximal blood lactate concentration during acute or chronic hypoxia (acclimatized subjects). Data on muscle biopsies (lactate concentration, changes in ATP, phosphocreatine and glycogen stores, glycolytic enzyme activities) and the few studies on lactate flux give in most cases evidence of a non-alteration of the anaerobic capacity for altitudes up to 5,500 m. No differences are observed in Wmax measured at high altitudes up to 5,200 m during intense short-term exercises: (1) jumps on a force platform which is a good indicator of alactic Wmax, and (2) 7-10 s sprints (i.e. force-velocity test) which solicit alactic metabolism but also lactic pathway. For exercises of duration equal or more than 30 s (i.e. Wingate test), there are conflicting results because a lower participation of aerobic metabolism during this test at high altitude can interfere with anaerobic performance. In conclusion, we can admit that anaerobic performances are not altered by high altitudes up to 5,200 m if the length of exposure does not exceed 5 weeks. After this period, muscle mass begins to decrease.

Acclimatization↗
PubMed1992

Physical fitness of children resident at high altitude in Bolivia.

In 7-15-yr-old children living in La Paz (Bolivia, altitude 3,700 m) (HA): 1) Maximal oxygen consumption (VO2max) varies from 35 to 45 ml.min-1.kg-1 and maximal heart rate from 188 to 194 beats.min-1. These values are lower than those of their counterparts at low altitude (LA) by 10-20% and 10-15 b.min-1, respectively. 2) The anaerobic metabolism is not affected by chronic hypoxia if the nutritional conditions and pubertal development of HA and LA boys are the same. When related to percent of VO2max, submaximal O2 debts are similar at HA and LA. After supramaximal exercise, maximal O2 debts (45.7 +/- 2.7 vs 45.9 +/- 3.8 ml.kg-1) and blood lactate concentrations (7.6 +/- 0.6 vs 6.5 +/- 0.6 mmol.l-1) are also the same at HA and LA. No differences are observed between the 2 altitudes in ventilatory (60 vs 56% VO2max) and lactate (60 vs 65% VO2max) thresholds. The altitude of La Paz does not alter the anaerobic performance of a force-velocity test (from 6 to 10 W.kg-1) between the ages of 7 to 15 years but reduces by 14-17% the mean anaerobic power developed during a 30-s Wingate test. This decrease could be linked to a lower participation of glycolysis and aerobic metabolism at HA during this test. 3) Poor socio-economic and nutritional conditions do not modify the aerobic performance of boys living in La Paz but lead to lower maximal anaerobic power (from -17% to -25%) when compared with HA boys from a high socio-economic background.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Interrelationships between plasma insulin-like growth factor-I (IGF-I) concentrations and plasma sex hormone levels in the growing male guinea-pig.

The aim of the present study was to determine the influence of androgens on Insulin-like Growth Factor-I (IGF-I) release at puberty in male guinea-pigs. After the animals were orchiectomised (CX) or sham-operated (SO) at the end of weaning, plasma testosterone (T), dihydrotestosterone (DHT) and IGF-I levels were measured by RIA at the 4th (W4), 8th (W8) and 12th (W12) week after delivery. Body weight (BW) was recorded before sampling at each stage of the experiment. Body growth was maximal between W4 and W8 for both SO (+97%) and CX (+84%). However SO were heavier than CX at W8 and W12. In SO, a surge of plasma IGF-I levels was observed between W4 and W8, concomitantly to the increase of androgen levels (IGF-I: +86%, P less than 0.01; T: +190%, P less than 0.001; DHT: +18%; P less than 0.01). Significant correlations between IGF-I, T, DHT and BW were found only from W4 to W8 but not from W8 to W12. In CX, IGF-I levels were higher than in SO at W4 (+72%, P less than 0.01) and at W12 (+39%, P less than 0.01). A surge of IGF-I levels (+47%, P less than 0.01) was also observed but was delayed compared to SO (between W8 and W12 vs W4 and W8). BW and IGF-I levels were significantly correlated during this period. Because the surge of IGF-I levels may occur even in absence of gonads, these results give evidence that the increases in IGF-I and androgens at puberty were independent in guinea-pigs during this period.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1991

Cardiac output during exercise in paraplegic subjects.

The purpose of this study was to measure the cardiac output using the CO2 rebreathing method during submaximal and maximal arm cranking exercise in six male paraplegic subjects with a high level of spinal cord injury (HP). They were compared with eight able bodied subjects (AB) who were not trained in arm exercise. Maximal O2 consumption (VO2max) was lower in HP (1.11.min, SD 0.1; 17.5 ml.min-1.kg-1, SD 4) than in AB (2.5 l.min-1, SD 0.6; 36.7 ml.min-1.kg, SD 10.7). Maximal cardiac output was similar in the groups (HP, 14 l.min-1, SD 2.6; AB, 16.8 l.min-1, SD 4). The same result was obtained for maximal heart rate (fc,max) (HP, 175 beats.min-1, SD 18; AB, 187 beats.min-1, SD 16) and the maximal stroke volume (HP, 82 ml, SD 13; AB, 91 ml, SD 27). The slopes of the relationship fc/VO2 were higher in HP than AB (P less than 0.025) but when expressed as a %VO2max there were no differences. The results suggest a major alteration of oxygen transport capacity to active muscle mass in paraplegics due to changes in vasomotor regulation below the level of the lesion.

Adult↗
PubMed1991

Bio-energetic profile in 144 boys aged from 6 to 15 years with special reference to sexual maturation.

The effects of growth and pubertal development on bio-energetic characteristics were studied in boys aged 6-15 years (n = 144; transverse study). Maximal oxygen consumption (VO2max, direct method), mechanical power at VO2max (PVO2max), maximal anaerobic power (Pmax; force-velocity test), mean power in 30-s sprint (P30s; Wingate test) were evaluated and the ratios between Pmax, P30s and PVO2max were calculated. Sexual maturation was determined using salivary testosterone as an objective indicator. Normalized for body mass VO2max remained constant from 6 to 15 years (49 ml.min-1.kg-1, SD 6), whilst Pmax and P30s increased from 6-8 to 14-15 years, from 6.2 W.kg-1, SD 1.1 to 10.8 W.kg-1, SD 1.4 and from 4.7 W.kg-1, SD 1.0 to 7.6 W.kg-1, SD 1.0, respectively, (P less than 0.001). The ratio Pmax:PVO2max was 1.7 SD 3.0 at 6-8 years and reached 2.8 SD 0.5 at 14-15 years and the ratio P30s:PVO2max changed similarly from 1.3 SD 0.3 to 1.9 SD 0.3. In contrast, the ratio Pmax:P30s remained unchanged (1.4 SD 0.2). Significant relationships (P less than 0.001) were observed between Pmax (W.kg-1), P30s (W.kg-1), blood lactate concentrations after the Wingate test, and age, height, mass and salivary testosterone concentration. This indicates that growth and maturation have together an important role in the development of anaerobic metabolism.

Adolescent↗
PubMed1991

Force-velocity and 30-s Wingate tests in boys at high and low altitudes.

The effects of high altitude (HA, 3,700 m) on performance during a force-velocity test (maximal anaerobic power, MAnP) and a 30-s Wingate test (mean power, P) were studied in boys 7-15 yr of age. Forty-seven children acclimatized to HA were compared with 101 living at low altitude (LA, 330 m). They had the same good nutritional status and the same level of physical activities [average 5.4 +/- 1.1 (SD) and 5.2 +/- 1.9 h/wk at HA and LA, respectively]. They performed the two tests using the same calibrated cycle ergometer. For the Wingate test, O2 uptake (VO2) during the 30 s and the peak of blood lactate concentration ([L]p) during the recovery were also measured. No difference in MAnP was observed between HA and LA. P, [L]p, and VO2 were lower at HA. This suggests that the altitude of 3,700 m did not affect the performance of the force-velocity test but reduced that of the Wingate test. This decrease in P was linked to a lower participation of glycolysis and aerobic metabolism. The latter is related to a reduced aerobic performance at HA. In addition, the slopes of the relationships between age and MAnP, P, and [L]p were the same at HA and LA, indicating that chronic hypoxia did not alter the development of the anaerobic metabolism during puberty.

Acclimatization↗
PubMed1990

Plasma free and sulphated catecholamines after ultra-long exercise and recovery.

We investigated the early and late effects of two types of ultra-long exercise on sympatho-adrenal and dopaminergic activity. With this aim both free and sulphoconjugated plasma catecholamines (CA), noradrenaline (NA), adrenaline (A), and dopamine (DA) were determined in two groups of athletes immediately after completion of 24-h running or a 10-h triathlon and on recovery during the next 1-3 days. Both races stimulated the sympathetic activity, but differences were observed in the CA pattern: the 24-h run induced a marked elevation of free and sulphoconjugated NA (+175% and +180%, respectively) but failed to alter significantly A and DA levels. The triathlon challenge increased the three conjugated CA (NA sulphate +350%; A sulphate +110%; DA sulphate +270%) and to a lesser extent free CA (NA +45%; A +30%). On the first post-exercise morning, a sustained intense noradrenergic activity was still present in the 24 h-runners, as evidenced by the large increase in free and sulphated NA levels (+140% and +100%, respectively). Such a prolonged activity was also indicated after completion of the triathlon, by the increase of NA sulphate (+140%) observed on the 1st recovery day. However, after the triathlon there was a decreased release of A from the adrenal medulla for several days. These data show that both types of ultralong exercise are able to induce for several hours a sustained sympathetic activation during the test and in the recovery period. Furthermore, the study shows that plasma conjugated CA may provide delayed and cumulative indexes of sympathetic activation, complementary to the instantaneous markers such as free CA.

Catecholamines↗