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Biomedical subjects

C Préfaut

Publications and source records attributed to C Préfaut.

At least 19 recordsLinked to original sources
PubMed1992

The effect of shuttle test protocol and the resulting lactacidaemia on maximal velocity and maximal oxygen uptake during the shuttle exercise test.

The purpose of this study was to investigate the influence of the shuttle test protocol (20-MST) and the resulting lactacidaemia on maximal velocity (Vmax) and maximal oxygen uptake (VO2max). Firstly, three randomly assigned tests to exhaustion were performed by 12 subjects: the treadmill test, the 20-MST, and a continuous running track test using the same prerecorded 1-min protocol as in the 20-MST (T1). One week later, subjects performed another track test, which was conducted up to the same level of effort as attained during the 20-MST (T2). For each test, Vmax, VO2max, lactate concentration at rest and during recovery, maximal heart rate, and distance covered were determined. The results indicated that the 20-MST underestimated Vmax; only T1 satisfactorily assessed Vmax (F = 15.49, P < 0.001). At the same level of effort, the peak blood lactate concentration (t = 2.7, P < 0.02) and VO2max (t = 11.35, P < 0.001) values were higher for the shuttle than for the continuous protocol. It was concluded that Vmax was limited by the running backwards and forwards in the protocol of the shuttle test. The higher values of peak blood lactate concentration and its earlier appearance obtained for the shuttle may have been one of the limiting factors of Vmax. However, the higher values of VO2max obtained for the 20-MST were most likely due to a combination of the relative hyperlactacidaemia and the biomechanical complexities required for this type of protocol.

Adolescent↗
PubMed1992

Benefits of caffeine ingestion on sprint performance in trained and untrained swimmers.

The influence of specific training on benefits from caffeine (Caf) ingestion was examined during a sprint test in a group of highly trained swimmers (T) and compared with the response of a group of untrained occasional swimmers (UT). Seven T and seven UT subjects swam freestyle two randomly assigned 2 x 100 m distances, at maximal speed and separated by 20 min of passive recovery, once after Caf (250 mg) and once after placebo (Pla) ingestion. Anaerobic capacity was assessed by the mean velocity (meters per second) during each 100 m and blood was sampled from the fingertip just before and 1, 3, 5, 7, and 9 min after each 100 m for resting and maximal blood lactate concentration ([la-]b,max) determination. The [la-]bmax was significantly enhanced by Caf in both T and UT subjects (P less than 0.01). However, only T subjects exhibited significant improvement in their swimming velocity (P less than 0.01) after Caf or any significant impairment during the second 100 m. In light of these results, it appears that specific training is necessary to benefit from the metabolic adaptations induced by Caf during supramaximal exercise requiring a high anaerobic capacity.

Adolescent↗
PubMed1992

Age and training effects on the lactate kinetics of master athletes during maximal exercise.

To study the effects of age and training on lactate production in older trained subjects, the lactate kinetics of highly trained cyclists [HT, n = 7; 65 (SEM 1.2) years] and control subjects with low training (LT, n = 7) and of similar age were compared to those of young athletes [YA, n = 7; 26 (SEM 0.7) years], during an incremental exercise test to maximum power. The results showed that the lactacidaemia at maximal oxygen uptake (VO2max) was lower for HT than for LT (P < 0.05) and, in both cases, lower than that of YA (P < 0.001). The respective values were HT: 3.9 (SEM 0.51), LT: 5.36 (SEM 1.12), and YA: 10.3 (SEM 0.63) mmol.l-1. At submaximal powers, however, the difference in lactacidaemia was not significant between HT and YA, although the values for lactacidaemia at VO2max calculated per watt and per watt normalized by body mass were significantly lower for HT (P < 0.001) and LT (P < 0.02). These results would indicate that the decline in power with age induced a decline in lactacidaemia. Yet this loss in power was not the only causative factor; indeed, our results indicated a complementary metabolic influence. In the older subjects training decreased significantly the lactacidaemia for the same submaximal power (P < 0.01) and from 60% of VO2max onwards (P < 0.05); as for YA it postponed the increase and accumulation of lactates. The lactate increase threshold (Thla-,1) was found at 46% VO2max for LT and at 56% VO2max for HT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Breathing pattern and ventilatory response to CO2 during exercise.

The aim of this study was to determine during moderate exercise whether response to the CO2 rebreathing test was dependent on differences in breathing pattern components among individuals recorded before the test and whether differences in tidal volume response and/or breathing frequency response to CO2 during the test could influence their ventilatory response to CO2. Ten healthy, sedentary male subjects, 20 to 34 years old, participated in the study. Ventilatory response to CO2 was measured by the CO2 rebreathing method (7% CO2, 50% O2). The measurements of breathing pattern components and CO2 rebreathing were made during mild steady state exercise: VCO2 = 20 ml.kg-1.min-1. We measured the following: 1) tidal volume (VTex) and breathing frequency (fex) before CO2 rebreathing and 2) ventilatory response to CO2 (SVEex), tidal volume response to CO2 (SVTex), and breathing frequency response to CO2 (Sfex) during the CO2 rebreathing test. The results showed that SVEex was correlated with VTex (r = 0.89, p less than 0.001), fex (r = -0.79, p less than 0.01), and Sfex (r = 0.83, p less than 0.01). There was no correlation between SVEex and SVTex. A curvilinear relationship existed between SVEex and alveolar ventilation calculated during exercise (r = 0.87, p less than 0.001), but there was no correlation with dead space. Sfex was positively correlated with VTex (r = 0.68, p less than 0.05) and negatively with fex (r = -0.70, p less than 0.05). We concluded that, during moderate exercise, higher tidal volumes measured before CO2 rebreathing were associated with higher response to the CO2 rebreathing test and consequently with higher ventilatory response to CO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Maximal anaerobic power: relationship to anthropometric characteristics during growth.

The purpose of this study was to determine the effects of age in relation to anthropometric characteristics upon maximal anaerobic power of legs in sixty-nine young boys aged 11 to 19 years. Maximal anaerobic power (Wmax) was measured by the force-velocity test. Lean body mass (LBM) was determined from all four skin-fold thickness measurements, leg volume (LV) was estimated by anthropometric method, and anthropometric measurements were used to determine total muscular mass (TMM). Wmax increased significantly (F = 44.1, p less than 0.001) between 11 and 19 years and was correlated with LV (r = 0.84) and TMM (r = 0.88). It was most highly correlated with LBM (r = 0.94), which best explained the percentage of the total variance of Wmax (88%). Normalized Wmax (Wmax/LBM) also increased significantly between 11 and 19 years (F = 21.9, p less than 0.001). In conclusion, Wmax determined by the force-velocity test was closely related to anthropometric characteristics, especially LBM, during the growth period. Furthermore, even when corrected for lean body mass, maximal anaerobic power was always found to increase. This suggests that other undetermined factors, in addition to the amount of lean tissue mass, may explain the increase of Wmax during the force-velocity test.

Adolescent↗
PubMed1992

Maximal and functional aerobic capacity as assessed by two graduated field methods in comparison to laboratory exercise testing in moderately trained subjects.

This study was undertaken to determine which of the two commonly used field tests, the 20-meter shuttle run test (20-MST) or the University of Montreal track test (UM-TT), provides the most accurate assessment of maximal and functional aerobic capacity in moderately trained athletes. Eleven male subjects aged from 18 to 30 years were studied in triple incremental and continuous running tests carried out until exhaustion both in laboratory and field conditions. They underwent a laboratory treadmill test and completed the outdoor 20-MST and UM-TT. During the three randomly assigned tests, maximal velocity (Vmax), maximal oxygen uptake (VO2max), maximal heart rate (HRmax), and post-exercise peak blood lactate (P[La]) measurements were made. The results indicate a significant difference in the mean Vmax (F = 9.26, p less than 0.001). Vmax determined by the 20-MST revealed a lower value than by treadmill (16.3%) and the UM-TT (19.3%). In contrast, there was no difference with regard to VO2max (F = 2.95, p = 0.06), HRmax (F = 2.72, p = 0.08), and P[La] (F = 2.79, p = 0.07). These results confirm that the UM-TT is a valid field test of maximal and functional aerobic capacity in moderately trained subjects and suggest that it can be additionally used for exercise prescription.

Adolescent↗
PubMed1992

[Evolution of bronchial hyperreactivity during post-exercise asthma].

The occurrence of a late reaction following exercise induced asthma is questionable and its relationship with the non specific bronchial hyperreactivity is poorly known. In this study, nine patients (age 15-21 years) underwent an exercise challenge in order to (a) determine the incidence of immediate and late phase reaction and (b) analyse the modifications of non specific bronchial hyperreactivity. Study design was a follow; day-3: determination of bronchial responsiveness to metacholine; day 0: control day with FEV1 measurements every hour for 11 hours; day 1: exercise challenge followed by a careful observation of change in FEV1; day 2: new determination of bronchial responsiveness to metacholine. An immediate exercise induced bronchial obstruction was observed in 5 patients. A late phase reaction (6th hour) with a fall of FEV1 equal to or more than 20% has been demonstrated in two patients. For the former, the change in FEV1 did not differ from the value of the control day. For the second, the FEV1 changed spontaneously during the control day so that decreases of FEV1 during control and challenge days were parallel. Thus, no late phase reaction were observed (F = 0.46; ns). There was no modification of bronchial responsiveness to metacholine (pre-exercise: 1,784 +/- 1,970 [SD]; post-exercise 1,827 +/- 2,231 micrograms [SD]). The lack of true late phase reaction when the post-exercise change in FEV1 is compared to the one of a control day and the absence of modification of non specific bronchial hyperreactivity weaken the hypothesis of an inflammatory mechanism of exercise induced asthma.

Adolescent↗
PubMed1992

[Relation between the change of slope of heart rate and second lactic and ventilatory thresholds in muscular exercise with large load].

The time-course of heart rate, blood lactate, and ventilatory gas exchange was studied during an incremental exercise test on cycloergometer in order to ascertain whether heart rate deflection occurred at the same load as the second lactate S[La]2) and ventilatory (SV2) thresholds. Twelve moderately trained subjects, 22 to 30 years old, participated in the study. The initial power setting was 30 W for 3 min with successive increases of 30 W every min except at the end of the test where the increase was reduced to 20 and 10 W.min-1. Ventilatory flow (VE), oxygen uptake (VO2), carbon dioxide production (VCO2, ventilatory equivalents of O2 (EO2 = VE/VO2) and CO2 (ECO2 = VE/VCO2), and heart rate (HR) were determined during the last 20 s of every min. Venous blood samples were drawn at the end of each stage of effort and analyzed enzymatically for lactate concentration ([La]). The HR deflection, S[La]2, and SV2 were represented graphically by two investigators using a double blind procedure. Following the method proposed by Conconi et al. 1982, the deflection in HR was considered to begin at the point beyond which the increase in work intensity exceeded the increase in HR and the linearity of the work rate/HR relationship was lost. S[La]2 corresponded to the second breaking point of the lactate time-course curve (onset of blood lactate accumulation) and SV2 was identified at the second breaking point in the increase in VE and ventilatory equivalent for O2 uptake accompanied by a concomitant increase in ventilatory equivalent for CO2 output. We observed that the deflection point in HR was present only in 7 subjects. The work load, VO2, HR, and [La] levels at which heart rate departed from linearity did not differ significantly from those determined with S[La]2 ans SV2. The VO2 and HR values at HR deflection point were significantly correlated with those measured at S[La]2 and SV2. It is concluded that deflection in heart rate does not always occur, and when it does, it coincides with the second lactate and ventilatory gas exchange thresholds. It can thus be used for the determination of optimal intensity for individualized aerobic training.

Adult↗
PubMed1992

[Physiopathological bases for retraining programs of asthma patients: adjustment to rehabilitation].

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.

Adaptation, Physiological↗
PubMed1991

Influence of anthropometric characteristics on changes in maximal exercise ventilation and breathing pattern during growth in boys.

The aim of this study was to investigate the effect of growth on ventilation and breathing pattern during maximal exercise oxygen consumption (VO2max) and their relationships with anthropometric characteristics. Seventy six untrained schoolboys, aged 10.5-15.5 years, participated in this study. Anthropometric measurements made included body mass, height, armspan, lean body mass, and body surface area. During an incremental exercise test, maximal ventilation (VEmax), tidal volume (VTmax), breathing frequency (fmax), inspiratory and expiratory times (tImax and tEmax), total duration of respiratory cycle (tTOTmax), mean inspiratory flow (VT/tImax), and inspiration fraction (tI/tTOTmax) were measured at VO2max. A power function was calculated between anthropometric characteristics and ventilatory variables to determine the allometric constants. The results showed firstly, that VEmax, VTmax, tImax, tEmax, tTOTmax, and VT/tImax increased with age and anthropometric characteristics (P less than 0.001), fmax decreased (P less than 0.001), and tI/tTOTmax remained constant during growth; secondly that lean body mass explained the greatest percentage of variance of VEmax (62.1%), VTmax (76.8%), and VT/tImax (70.6%), while anthropometric characteristics explained a slight percentage of variance of fmax and timing; and thirdly that VEmax, VTmax, and VT/tImax normalized by lean body mass did not change significantly with age. We concluded that at VO2max there were marked changes in ventilation and breathing pattern with growth. The changes in VEmax, VTmax, and VT/tImax were strongly related to the changes in lean body mass.

Adolescent↗
PubMed1991

Effects of caffeine ingestion on performance and anaerobic metabolism during the Wingate Test.

In order to determine the effects of caffeine ingestion on performance and metabolic responses during supramaximal exercise, six healthy volunteers performed the Wingate Anaerobic Test twice. Sixty min before each trial, while in a fasting state, they took capsules containing either caffeine (5 mg/kg) or a placebo, according to a single blind and randomized procedure. Caffeine administration did not significantly change either maximal anaerobic capacity (AC) or power (AP) and power decrease (PD). It did, however, induce significant (p less than 0.05) increases in both catecholamine and blood lactate levels as compared to values obtained after placebo administration. Moreover, maximal blood lactate occurred earlier (p less than 0.05), and lactate output seemed to be greater with caffeine (p less than 0.01). There was a strong correlation, both with and without caffeine, between epinephrine and lactate levels (r = 0.81) and between both AP and AC and lactate levels. These data suggest that caffeine, essentially via epinephrine, modifies glycolytic metabolism but fails to improve performance during the Wingate Anaerobic Test in nonspecifically trained subjects.

Adult↗
PubMed1991

Sickle cell trait in Ivory Coast athletic champions, 1956-1989.

Thirteen sickle cell trait carriers (SCTC) were found among 129 Ivory Coast champions or record holders in races for the period from 1956 to 1989 (10.1%). These 13 SCTC won 33 titles and national records (7.0%): 32 (12.5%) in races of 400 m or less and only one (0.004%) in races of 800 m or more, and the highest-performing SCTC won 8 titles and national records. A comparison with non-SCTC Ivory Coast champions shows that SCTC won significantly fewer titles than non-SCTC in long-distance races and that they won fewer titles during their careers.

Black People↗
PubMed1991

Effect of resistive loads on pattern of respiratory muscle recruitment during exercise.

In healthy subjects, we compared the effects of an expiratory (ERL) and an inspiratory (IRL) resistive load (6 cmH2O.l-1.s) with no added resistive load on the pattern of respiratory muscle recruitment during exercise. Fifteen male subjects performed three exercise tests at 40% of maximum O2 uptake: 1) with no-added-resistive load (control), 2) with ERL, and 3) with IRL. In all subjects, we measured breathing pattern and mouth occlusion pressure (P0.1) from the 3rd min of exercise, in 10 subjects O2 uptake (VO2), CO2 output (VCO2), and respiratory exchange ratio (R), and in 5 subjects we measured gastric (Pga), pleural (Ppl), and transdiaphragmatic (Pdi) pressures. Both ERL and IRL induced a high increase of P0.1 and a decrease of minute ventilation. ERL induced a prolongation of expiratory time with a reduction of inspiratory time (TI), mean expiratory flow, and ratio of inspiratory to total time of the respiratory cycle (TI/TT). IRL induced a prolongation of TI with a decrease of mean inspiratory flow and an increase of tidal volume and TI/TT. With ERL, in two subjects, Pga increased and Ppl decreased more during inspiration than during control suggesting that the diaphragm was the most active muscle. In one subject, the increases of Ppl and Pga were weak; thus Pdi increased very little. In the two other subjects, Ppl decreased more during inspiration but Pga also decreased, leading to a decrease of Pdi. This suggests a recruitment of abdominal muscles during expiration and of accessory and intercostal muscles during inspiration. With IRL, in all subjects, Ppl again decreased more, Pga began to decrease until 40% of TI and then increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Hyperpnoea and CO2 sensitivity of the respiratory centres during exercise.

The aim of this study was to specify whether exercise hyperpnoea was related to the CO2 sensitivity of the respiratory centres measured during steady-state exercise of mild intensity. Thus, ventilation (VE), breathing pattern [tidal volume (VT), respiratory frequency (f), inspiratory time (TI), total time of the respiratory cycle (TTOT), VT/TI, TI/TTOT] and CO2 sensitivity of the respiratory centres determined by the rebreathing method were measured at rest (SCO2re) and during steady-state exercise (SCO2ex) of mild intensity [CO2 output (VCO2) = 20 ml.kg-1.min-1] in 11 sedentary male subjects (aged 20-34 years). The results showed that SCO2re and SCO2ex were not significantly different. During exercise, there was no correlation between VE and SCO2ex and, for the same VCO2, all subjects had very close VE values normalized for body mass (bm), regardless of their SCO2ex (VEbm0.75 = 1.44 l.min-1.kg-1 SD 0.10). A highly significant positive correlation between SCO2ex and VT (normalised for bm) (r = 0.80, P less than 0.01), TI (r = 0.77, P less than 0.01) and TTOT (r = 0.77, P less than 0.01) existed, as well as a highly significant negative correlation between SCO2ex and (normalised for bm-0.25) (r = -0.73, P less than 0.01). We conclude that the hyperpnoea during steady-state exercise of mild intensity is not related to the SCO2ex. The relationship between breathing pattern and SCO2ex suggests that the breathing pattern could influence the determination of the SCO2ex. This finding needs further investigation.

Adult↗
PubMed1990

Differences in aerobic and anthropometric characteristics between peripubertal swimmers and non-swimmers.

In order to judge the effect of moderate sports training on the anthropometric characteristics and aerobic capacity of boys before and during puberty, a comparative study was conducted of 140 children, 94 of whom were not undergoing any specific training and 45 of whom were spending more than 3 hours a week practising swimming. The boys were divided into three maturity groups according to pubic hair status: prepubertal, pubertal, and end of puberty. The study shows greater maximal oxygen uptake in absolute terms, body weight, lean body mass, chest circumference, arm circumference, and arm muscle area for the swimmers. The morphological differences between the swimmers and non-swimmers concern physical characteristics generally involved in swimming. The difference in aerobic capacity, however, may be in part due to the morphological changes engendered by training; a longitudal study would confirm this. It is suggested that anthropometric indicators of arm muscles may be used in the biological supervision of swimming training.

Adolescent↗
PubMed1990

[Place of muscular exercise test in screening in asymptomatic smokers].

The diagnosis of smoking-related chronic obstructive pulmonary disease (COPD) is often made too late. Could the study of breathing pattern during exercise testing help in earlier detection. In order to test this hypothesis, we studied 34 asymptomatic smokers (S) compared to 55 nonsmoking controls (NS). The subjects, divided into 3 age groups (30-60 yr), were comparable in terms of anthropometric and spirometric characteristics. The smokers from 30-50 yr had a lower VO2max than the controls (p less than 0.01) whereas the older smokers (50-60 yr) had a VO2max comparable to that of the controls. The study of breathing pattern indicated rapid, shallow breathing by all smokers. Thus exercise testing, and the abnormalities observed in breathing pattern, would seem to help in early detection of COPD in asymptomatic smokers.

Adult↗
PubMed1990

[Effects of individualized aerobic training in the readaptation of the asthmatic child to exercise].

There have been few works studying the effects of training in asthmatics and there does not yet exist any study utilising the idea of the individualization of training. This is why the aim of this study was to assess the value of the effects of individualised aerobic training on cardio-respiratory aptitude in the asthmatic child. This study was carried out on two populations of asthmatics, swimmers and non-swimmers matched for age, height, degree of bronchial obstruction during a remission and baseline of physical fitness. Each child in the swimming group was trained to a metabolic level corresponding to the ventilatory threshold. After a period of 3 months a second cardio-respiratory evaluation was carried out. A clear cut improvement (20%) of VO2 max was observed as well as a proportional elevation of the ventilatory threshold in the swimming group. The VE max, the VT max, the VT/Timax, the FC max and the maximal oxygen uptake were also recorded. On the other hand aerobic training seems to be without effect on resting pulmonary function, even if the clinical state of the children improved. In conclusion this study shows that aerobic training closely adapted to the level of each child, obtains an important and rapid gain in cardio-respiratory fitness which leads to a better exercise adaptation. In addition the progression of the ventilatory threshold implies an increased capacity for work without the appearance of hyperventilation. This enables an understanding of how aerobic training is generally accompanied in the asthmatic with a better respiratory comfort and argues in favour of the perfect efficacy of this type of reconditioning in the re-adaptation to effort in these patients.

Adolescent↗