Oxygen uptake kinetics in trained adolescent females

Little evidence exists with regard to the effect that exercise training has upon oxygen uptake kinetics in adolescent females. PURPOSE: The aim of the study was to compare [Formula: see text] and muscle deoxygenation kinetics in a group of trained (Tr) and untrained (Utr) female adolescents. METHOD: Twelve trained (6.4 ± 0.9 years training, 10.3 ± 1.4 months per year training, 5.2 ± 2.0 h per week) adolescent female soccer players (age 14.6 ± 0.7 years) were compared to a group (n = 8) of recreationally active adolescent girls (age 15.1 ± 0.6 years) of similar maturity status. Subjects underwent two, 6-min exercise transitions at a workload equivalent to 80 % of lactate threshold from a 3-min baseline of 10 W. All subjects had a passive rest period of 1 h between each square-wave transition. Breath-by-breath oxygen uptake and muscle deoxygenation were measured throughout and were modelled via a mono-exponential decay with a delay relative to the start of exercise. RESULT: Peak [Formula: see text] was significantly (p < 0.05) greater in the Tr compared to the Utr (Tr: 43.2 ± 3.2 mL kg(-1 )min(-1) vs. Utr: 34.6 ± 4.0 mL kg(-1 )min(-1)). The [Formula: see text] time constant was significantly (p < 0.05) faster in the Tr compared to the Utr (Tr: 26.3 ± 6.9 s vs. Utr: 35.1 ± 11.5 s). There was no inter-group difference in the time constant for muscle deoxygenation kinetics (Tr: 8.5 ± 3.0 s vs. Utr: 12.4 ± 8.3 s); a large effect size, however, was demonstrated (-0.804). CONCLUSION: Exercise training and/or genetic self-selection results in faster kinetics in trained adolescent females. The faster [Formula: see text] kinetics seen in the trained group may result from enhanced muscle oxygen utilisation

Pulmonary oxygen uptake and muscle deoxygenation kinetics during recovery in trained and untrained male adolescents

Previous studies have demonstrated faster pulmonary oxygen uptake ( V ˙ O 2 ) kinetics in the trained state during the transition to and from moderate-intensity exercise in adults. Whilst a similar effect of training status has previously been observed during the on-transition in adolescents, whether this is also observed during recovery from exercise is presently unknown. The aim of the present study was therefore to examine V ˙ O 2 kinetics in trained and untrained male adolescents during recovery from moderate-intensity exercise. 15 trained (15 ± 0.8 years, V ˙ O 2max 54.9 ± 6.4 mL kg−1 min−1) and 8 untrained (15 ± 0.5 years, V ˙ O 2max 44.0 ± 4.6 mL kg−1 min−1) male adolescents performed two 6-min exercise off-transitions to 10 W from a preceding “baseline” of exercise at a workload equivalent to 80% lactate threshold; V ˙ O 2 (breath-by-breath) and muscle deoxyhaemoglobin (near-infrared spectroscopy) were measured continuously. The time constant of the fundamental phase of V ˙ O 2 off-kinetics was not different between trained and untrained (trained 27.8 ± 5.9 s vs. untrained 28.9 ± 7.6 s, P = 0.71). However, the time constant (trained 17.0 ± 7.5 s vs. untrained 32 ± 11 s, P < 0.01) and mean response time (trained 24.2 ± 9.2 s vs. untrained 34 ± 13 s, P = 0.05) of muscle deoxyhaemoglobin off-kinetics was faster in the trained subjects compared to the untrained subjects. V ˙ O 2 kinetics was unaffected by training status; the faster muscle deoxyhaemoglobin kinetics in the trained subjects thus indicates slower blood flow kinetics during recovery from exercise compared to the untrained subjects

Myocardial function and aerobic fitness in adolescent females

A recent report indicated that variations in myocardial functional (systolic and diastolic) responses to exercise do not contribute to inter-individual differences in aerobic fitness (peak VO2) among young males. This study was designed to investigate the same question among adolescent females. Thirteen highly fit adolescent football (soccer) players (peak VO2 43.5 ± 3.4 ml kg−1 min−1) and nine untrained girls (peak VO2 36.0 ± 5.1 ml kg−1 min−1) matched for age underwent a progressive cycle exercise test to exhaustion. Cardiac variables were measured by standard echocardiographic techniques. Maximal stroke index was greater in the high-fit group (50 ± 5 vs. 41 ± 4 ml m−2), but no significant group differences were observed in maximal heart rate or arterial venous oxygen difference. Increases in markers of both systolic (ejection rate, tissue Doppler S′) and diastolic (tissue Doppler E′, mitral E velocity) myocardial functions at rest and during the acute bout of exercise were similar in the two groups. This study suggests that among healthy adolescent females, like young males, myocardial systolic and diastolic functional capacities do not contribute to inter-individual variability in physiologic aerobic fitness

Theorising international environmental law

From The Oxford Handbook of International Legal Theory (Florian Hoffmann and Anne Orford, eds, Oxford UP, forthcoming 2014). --- This paper, part of a larger work on international law theory, sketches some early lines of inquiry towards a theoretical understanding of international environmental law. As the body of international law regulating human interaction with the natural world, one might expect this branch of law to be a cornerstone of the international system. Yet in practice, international environmental law's reach is strikingly circumscribed. Little of the governance of natural resources, for example, is 'environmental'. Subsisting at the periphery, environmental law focuses on conserving particular (rare, exotic) species and 'ecosystems', and curbing certain kinds of pollution. Its principles are vague, peppering the margins of rulings within other judicial fora: it is quintessential soft law. In this paper, we suggest that international environmental law's dilemmas are due to two competing heritages. On one hand, this law enshrines the peculiar pantheism of the European romantic period, positing the 'natural world' as sacred, inviolable, redemptive. On the other, its main antecedents are found in colonial era practices, which provided the data for the earliest environmental science and a laboratory for prototypical attempts at conservation and sustainable development. Caught between irreconcilable demands, international environmental law struggles today to avoid utopian irrelevance or nugatory paralysis

Leadership in the Mold of Jesus: Growing the Church and Saving the Nation in Neo-Pentecostal Guatemala City

Reu T. Leadership in the Mold of Jesus: Growing the Church and Saving the Nation in Neo-Pentecostal Guatemala City. JOURNAL OF LATIN AMERICAN AND CARIBBEAN ANTHROPOLOGY. 2019;24(3):746-762.Based on ethnographic fieldwork in one of the largest megachurches in Guatemala, this article describes the cultural impact that the concept of Christian leadership has on the peculiar attitudes toward society that neo-Pentecostal believers develop as members of their religious communities. Evangelical organizations promote liderazgo (leadership) as a remedy for the problems that ail the world. For the residents of Guatemala's capital city, these include extreme levels of violence and crime. At the same time, liderazgo is a principal component of the cell group model, a growth strategy that many neo-Pentecostal churches deploy. This article argues that, in Guatemala, Christian leadership and the cell group model provide a conceptual and pragmatic infrastructure for a specifically evangelical practice of citizenship. By summoning believers to engage with the world beyond their congregations, this practice qualifies the quintessential individualism that scholars typically find in the evangelical faith