Comparison of mechanical ventilatory constraints between continuous and intermittent exercises in healthy prepubescent children.

International audienceBBackground: The aim of this study was to evaluate the occurrence and severity of mechanical ventilatory constraints in healthy prepubescent children during continuous and intermittent exercise. Methods: Twelve prepubescent children (7 - 11 years old) performed 7 exercises on a treadmill: one graded test for the determination of maximal aerobic speed (MAS), three continuous exercises (CE) at 60, 70 and 80% of MAS and three intermittent exercises (IE), alternating 15s of exercise with 15s of passive recovery, at 90, 100 and 110% of MAS. During each CE and IE, tidal flow/volume loops were plotted within a maximal flow/volume loop (MFVL) measured at rest before each exercise. Expiratory flow limitation (expFL expressed in %Vt) was defined as the part of exercise tidal volume (Vt) meeting the boundary of MFVL. Breathing strategy was estimated by measuring inspiratory capacity relative to forced vital capacity and tidal volume relative to inspiratory capacity. Other breathing pattern parameters (ventilation VE, Vt, respiratory frequency f) were continuously recorded during exercise. Results: An "intensity" effect was found for during CE (p<0.001) but not during IE (p=0.08). The increase in was predominantly assumed by an increase in f for both exercise modalities. During each exercise, several children heterogeneously experienced expFL ranging between 10 - 90%Vt. For all exercises, Vt was predominantly regulated by an increase in Vt/IC with no change in IC/FVC from rest to exercise. Finally, no significant "modality" effect was found for mechanical ventilatory constraint parameters (expFL, VT/IC and IV/FVC). Discussion: We could conclude that neither of the modalities studied induced more mechanical ventilatory constraints than the other, but that exercise intensities specific to each modality might be greater sources of exacerbation for mechanical ventilatory constraints

Réponses physiologiques à l'exercice intermittent maximal sur piste et sur tapis roulant

Un exercice intermittent maximal réalisé sur piste en condition extérieure semble induire une sollicitation métabolique (exprimée par les valeurs de tVO2max, calcul du temps passé à VO2 max, et par la lactatémie de fin d'exercice) plus importante que lorsqu'il est réalisé en laboratoire sur tapis roulant avec une pente de 1%

Réponses physiologiques à l'exercice intermittent maximal sur piste et sur tapis roulant

Un exercice intermittent maximal réalisé sur piste en condition extérieure semble induire une sollicitation métabolique (exprimée par les valeurs de tVO2max, calcul du temps passé à VO2 max, et par la lactatémie de fin d'exercice) plus importante que lorsqu'il est réalisé en laboratoire sur tapis roulant avec une pente de 1%

Puissance critique de l’enfant prépubère et de l’adulte

Aim. – The aim of the study was to compare aerobic and anerobic abilities of prepubertal children and adults with the critical power concept.Methods. – Sixteen children (10.3 ± 0.9 years) and 15 adults (23.5 ± 3.6 years) performed five tests: a maximal-graded test and four constant load exercises until exhaustion. Critical power (CP) and anaerobic-work capacity (CTA) were determined from the power-1/time (P-t) linear relationship.Results. – Determination coefficients for P-t were 0.94 ± 0.05 in children and 0.96 ± 0.04 in adults. PC values were significantly (p < 0.01) lower in children (2.7 ± 0.4 W/kg) than in adults (3.1 ± 0.3 W/kg). CTA values were significantly (p < 0.001) lower in children (136.4 ± 50.8 J/kg) than in adults (247.1 ± 45.7 J/kg).Conclusion. – Satisfying determination coefficients for CP and CTA were found in children and adults. Children have a lower CP and CTA than adults. This result is in accordance with literature.Objectif. – L’objectif de cette étude était de comparer, à l’aide du concept de puissance critique, les qualités aérobie et anaérobie d’enfants prépubères et d’adultes.Méthode. – Seize enfants (10,3 ± 0,9 ans) et 15 adultes (23,5 ± 3,6 ans) ont réalisé cinq tests : un exercice maximal à puissance croissante et quatre exercices à puissance constante jusqu’à épuisement. La puissance critique (PC) et la capacité de travail anaérobie (CTA) ont été déterminées à partir de la relation linéaire puissance-1/temps (P-t).Résultats. – Des coefficients de détermination élevés ont été obtenus pour la relation P-t chez l’enfant (0,94 ± 0,05) et chez l’adulte (0,96 ± 0,04). Les valeurs de PC étaient significativement inférieures (p < 0,01) chez l’enfant (2,7 ± 0,4 W/kg) en comparaison de l’adulte (3,1 ± 0,3 W/kg). Les valeurs de CTA étaient significativement inférieures (p < 0,001) chez l’enfant (136,4 ± 50,8 J/kg) en comparaison de l’adulte (247,1 ± 45,7 J/kg).Conclusion. – Le concept de puissance critique s’avère applicable aux performances des enfants. Il donne des informations cohérentes avec les caractéristiques des enfants habituellement reportées dans le littérature concernant leurs qualités aérobies et anaérobies

Time to exhaustion and time spent at a high percentage of VO2max in severe intensity domain in children and adults.

International audienceThe aim of the study was to compare time spent at a high percentage of VO2max (>90% of VO2max) (ts90%), time to achieve 90% of VO2max (ta90%), and time to exhaustion (TTE) for exercise in the severe intensity domain in children and adults. Fifteen prepubertal boys (10.3 ± 0.9 years) and 15 men (23.5 ± 3.6 years) performed a maximal graded exercise to determine VO2max, maximal aerobic power (MAP) and power at ventilatory threshold (PVTh). Then, they performed 4 constant load exercises in a random order at PVTh plus 50 and 75% of the difference between MAP and PVTh (PΔ50 and PΔ75) and 100 and 110% of MAP (P100 and P110). VO2max was continuously monitored. The P110 test was used to determine maximal accumulated oxygen deficit (MAOD). No significant difference was found in ta90% between children and adults. ts90% and TTE were not significantly different between children and adults for the exercises at PΔ50 and PΔ75. However, ts90% and TTE during P100 (p < 0.05 and p < 0.01, respectively) and P110 (p < 0.001) exercises were significantly shorter in children. Children had a significantly lower MAOD than adults (34.3 ± 9.4 ml · kg vs. 53.6 ± 11.1 ml · kg). A positive relationship (p < 0.05) was obtained between MAOD and TTE values during the P100 test in children. This study showed that only for intensities at, or higher than MAP, lower ts90% in children was linked to a reduced TTE, compared to adults. Shorter TTE in children can partly be explained by a lower anaerobic capacity (MAOD). These results give precious information about exercise intensity ranges that could be used in children's training sessions. Moreover, they highlight the implication of both aerobic and anaerobic processes in endurance performances in both populations

Assessment of child-specific aerobic fitness and anaerobic capacity by the use of the power-time relationships constants

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Mechanical ventilatory constraints during incremental exercise in healthy and cystic fibrosis children.

International audienceTo analyze breathing pattern and mechanical ventilatory constraints during incremental exercise in healthy and cystic fibrosis (CF) children. Thirteen healthy children and 6 children with cystic fibrosis volunteered to perform an incremental test on a treadmill. Exercise tidal flow/volume loops were plotted every minute within a maximal flow/volume loop (MFVL). Expiratory flow limitation (expFL expressed in %Vt) was evaluated and end-expiratory and end-inspiratory lung volumes (EELV and EILV) were estimated from expiratory reserve volume relative to vital capacity (ERV/FVC) and from inspiratory reserve volume relative to vital capacity (IRV/FVC). During the incremental exercise, expFL was first observed at 40% of maximal aerobic speed in both groups. At maximal exercise, 46% of healthy children and 83% of CF children presented expFL, without significant effect of cystic fibrosis on the severity of expFL. According to the two-way ANOVA results, both groups adopted similar breathing pattern and breathing strategies as no significant effect of CF has been revealed. But, according to one-way ANOVA results, a significant increase of ERV/FVC associated with a significant decrease of IRV/FVC from resting value shave been observed in healthy children at maximal exercise, but not in CF children. The hypothesis of this study was based on the assumption that mild cystic fibrosis could induce more frequent and more severe mechanical ventilatory constraints due to pulmonary impairment and breathing pattern disturbances. But, this study did not succeed to highlight an effect of mild cystic fibrosis on the mechanical ventilatory constraints (expFL and dynamic hyperinflation) that occur during an incremental exercise. This absence of effect could be due to the absence of an impact of the disease on spirometric data, breathing pattern regulation during exercise and breathing strategy

Influence of recovery intensity on time spent at maximal oxygen uptake during an intermittent session in young, endurance-trained athletes.

In this study, we examined the effects of three recovery intensities on time spent at a high percentage of maximal oxygen uptake (t90[Vdot]O(2max)) during a short intermittent session. Eight endurance-trained male adolescents (16 +/- 1 years) performed four field tests until exhaustion: a graded test to determine maximal oxygen uptake ([Vdot]O(2max); 57.4 +/- 6.1 ml x min(-1) . kg(-1)) and maximal aerobic velocity (17.9 +/- 0.4 km x h(-1)), and three intermittent exercises consisting of repeat 30-s runs at 105% of maximal aerobic velocity alternating with 30 s active recovery at 50% (IE(50)), 67% (IE(67)), and 84% (IE(84)) of maximal aerobic velocity. In absolute values, mean t90[Vdot]O(2max) was not significantly different between IE(50) and IE(67), but both values were significantly longer compared with IE(84). When expressed in relative values (as a percentage of time to exhaustion), mean t90[Vdot]O(2max) was significantly higher during IE(67) than during IE(50). Our results show that both 50% and 67% of maximal aerobic velocity of active recovery induced extensive solicitation of the cardiorespiratory system. Our results suggest that the choice of recovery intensity depends on the exercise objective

Correspondences between continous and intermittent exercise intensities in healthy prepubescent

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