Oxygen uptake kinetics in children and adults after the onset of moderate-intensity exercise

Abstract

The literature suggests that the oxygen uptake (VO2) response to the onset of moderate-intensity exercise may be both mature from childhood and independent of sex. Yet the cardiorespiratory response to exercise and the metabolic profile of the muscle appear to change with growth and development and to differ between the sexes. The aim of this study was to investigate further changes in the VO2 kinetic response with age and sex. Participants completed a series of no less than four step change transitions, from unloaded pedalling to a constant work rate corresponding to 80% of their previously determined ventilatory threshold. Each participant's breath-by-breath responses were interpolated to 1 s intervals, time aligned and then averaged. A single exponential model that included a time delay was used to analyse the averaged response following phase 1 (15 s). Participants with parameter confidence intervals more than +/- 5 s were removed from the sample; the results for the remaining 13 men and 12 women (age 19-26 years), 12 boys and 11 girls (age 11-12 years) were used for statistical analysis. Children had a significantly shorter time constant than adults, both for males (19.0+/-2.0 and 27.9+/-8.6 s respectively; P<0.01) and females (21.0+/-5.5 and 26.0+/-4.5 s respectively; P<0.05). There were no significant differences in the time constant between the sexes for either adults or children (P>0.05). A significant relationship between the time constant and peak VO2 was found only in adult males (P<0.05). A shorter time constant in children may reflect an enhanced potential for oxidative metabolism.

Cinética do consumo de oxigênio a intensidades de nado moderada e extrema

“…Regarding the intensity corresponding to the lan ind , the values presented corroborate the ones reported in the literature for efforts performed in cycle ergometer [17][18][19][20][21] . In the present study, the fact the time constant is not similar between the two intensities seems to be due to the extreme intensity at which the 200 m crawl were performed.…”

“…Although no study has been carried out at this specific intensity, other ones conducted at the moderate intensity domain presented monoexponential fitting in the VO 2 kinetics [17][18][19][20][21] . Concerning extreme intensity, monoexponential fittings were previously defined as being more positive for this intensity domain 7 .…”

No acetyl group deficit is evident at the onset of exercise at 90% of maximal oxygen uptake in humans

“…Unfortunately due to ethical committee concerns over the infusate, we were unable to conduct more than one exercise transition. However, despite the use of only a single transition for each condition in the present study, the large amplitude of the pulmonary (Fawkner et al 2002) …”

“…To improve the signal-to-noise ratio of breath-by-breath pulmonary (Lamarra, Whipp, Ward, & Wasserman, 1987;Fawkner, Armstrong, Potter, & Welsman, 2002). Unfortunately due to ethical committee concerns over the infusate, we were unable to conduct more than one exercise transition.…”

Cinética do consumo de oxigênio e tempo limite na vvo2max: comparação entre homens e mulheres

“…Tem sido encontrada correlação inversa entre o τ, VO 2max (7,8) e atividade da enzima citrato sintase (5) , indicando limitação periférica para o VO 2 (inércia metabólica) como sendo o principal fator limitante para o rápido ajuste do metabolismo aeróbio (6) . Tem sido hipotetizado que a resposta frente ao esforço físico de carga constante, controlada pela oferta e utilização de O 2 , pode diferir entre homens e mulheres (7,8) . Entretanto, em exercício executado em intensidade de 80% do limiar ventilatório, não foi observada diferença entre homens e mulheres (7) .…”