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

Reproducibility of onset and recovery oxygen uptake kinetics in moderately impaired patients with chronic heart failure

Oxygen (O2) kinetics reflect the ability to adapt to or recover from exercise that is indicative of daily life. In patients with chronic heart failure (CHF), parameters of O2 kinetics have shown to be useful for clinical purposes like grading of functional impairment and assessment of prognosis. This study compared the goodness of fit and reproducibility of previously described methods to assess O2 kinetics in these patients. Nineteen CHF patients, New York Heart Association class II–III, performed two constant-load tests on a cycle ergometer at 50% of the maximum workload. Time constants of O2 onset- and recovery kinetics (τ) were calculated by mono-exponential modeling with four different sampling intervals (5 and 10 s, 5 and 8 breaths). The goodness of fit was expressed as the coefficient of determination (R2). Onset kinetics were also evaluated by the mean response time (MRT). Considering O2 onset kinetics, τ showed a significant inverse correlation with peak- \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} \ifmmode\expandafter\dot\else\expandafter\.\fi{V}{\text{O}}_{2} \end{document} (R = −0.88, using 10 s sampling intervals). The limits of agreement of both τ and MRT, however, were not clinically acceptable. O2 recovery kinetics yielded better reproducibility and goodness of fit. Using the most optimal sampling interval (5 breaths), a change of at least 13 s in τ is needed to exceed normal test-to-test variations. In conclusion, O2 recovery kinetics are more reproducible for clinical purposes than O2 onset kinetics in moderately impaired patients with CHF. It should be recognized that this observation cannot be assumed to be generalizable to more severely impaired CHF patients

Efeitos do treinamento muscular inspiratório em universitários tabagistas e não tabagistas

O hábito de fumar pode reduzir a capacidade aeróbica, aumentar a resistência ao fluxo aéreo e afetar a função dos músculos respiratórios. O objetivo deste estudo foi comparar os efeitos do Treinamento Muscular Inspiratório (TMI) entre dois grupos: tabagistas e não tabagistas. Participaram 44 voluntários universitários, divididos em dois grupos: tabagistas (GT), composto por 20 indivíduos (25,60±7,01 anos) e não tabagistas, constituindo o Grupo Controle (GC), composto por 24 voluntários (24,08±7,52 anos). Ambos os grupos foram submetidos ao TMI, por meio do uso do manovacuômetro aneroide, com duração de 6 semanas, sendo 3 sessões semanais, totalizando 18 sessões. Os resultados mostraram diferença estatisticamente significativa (p<0,05) pós-TMI no GC para as variáveis: Pressão Inspiratória Máxima (PImáx), Pico de Fluxo Expiratório (PFE), Pressão Arterial Média ao repouso (PAM pré-TC6) e Teste de Caminhada de Seis Minutos (TC6). No GT, houve diferença estatisticamente significativa pós-TMI para as variáveis: PImáx, PFE, TC6 e saturação periférica de oxigênio após o TC6 (SpO2 pós-imediata). A comparação das médias das variáveis entre GT e GC mostrou diferença estatisticamente significativa no pós-TMI para as variáveis PImáx e PFE. A variável TC6 não apresentou diferença estatisticamente significativa. Conclui-se que o TMI proporcionou um aumento significativo da força muscular inspiratória, melhora da função pulmonar e melhora do desempenho físico nos indivíduos estudados

High-intensity kayak performance after adaptation to intermittent hypoxia

Context:Live-high train-low altitude training produces worthwhile gains in performance for endurance athletes, but the benefits of adaptation to various forms of artificial altitude are less clear.Purpose:To quantify the effects of intermittent hypoxic exposure on kayak performance.Methods:In a crossover design with a 6-week washout, we randomized 10 subelite male sprint kayak paddlers to hypoxia or control groups for 3 weeks (5 days/week) of intermittent hypoxic exposure using a nitrogen-filtration device. Each day's exposure consisted of alternately breathing hypoxic and ambient air for 5 minutes each over 1 hour. Performance tests were an incremental step test to estimate peak power, maximal oxygen uptake, exercise economy, and lactate threshold; a 500-m time trial; and 5 × 100-m sprints. All tests were performed on a wind-braked kayak ergometer 7 and 3 days pretreatment and 3 and 10 days post treatment. Hemoglobin concentration was measured at 1 day pretreatment, 5 and 10 days during treatment, and 3 days after treatment.Results:Relative to control, at 3 days post treatment the hypoxia group showed the following increases: peak power 6.8% (90% confidence limits, ± 5.2%), mean repeat sprint power 8.3% (± 6.7%), and hemoglobin concentration 3.6% (± 3.2%). Changes in lactate threshold, mean 500-m power, maximal oxygen uptake, and exercise economy were unclear. Large effects for peak power and mean sprint speed were still present 10 days posthypoxia.Conclusion:These effects of intermittent hypoxic exposure should enhance performance in kayak racing. The effects might be mediated via changes in oxygen transport.</jats:sec

Lower-body determinants of running economy in male and female distance runners

A variety of training approaches have been shown to improve running economy in well-trained athletes. However, there is a paucity of data exploring lower-body determinants that may affect running economy and account for differences that may exist between genders. Sixty-three male and female distance runners were assessed in the laboratory for a range of metabolic, biomechanical, and neuromuscular measures potentially related to running economy (ml$kg21$min21) at a range of running speeds. At all common test velocities, women were more economical than men (effect size [ES] = 0.40); however, when compared in terms of relative intensity, men had better running economy (ES = 2.41). Leg stiffness (r = 20.80) and moment arm length (r = 0.90) were large-extremely largely correlated with running economy and each other (r = 20.82). Correlations between running economy and kinetic measures (peak force, peak power, and time to peak force) for both genders were unclear. The relationship in stride rate (r = 20.27 to 20.31) was in the opposite direction to that of stride length (r = 0.32–0.49), and the relationship in contact time (r = 20.21 to 20.54) was opposite of that of flight time (r = 0.06–0.74). Although both leg stiffness and moment arm length are highly related to running economy, it seems that no single lower-body measure can completely explain differences in running economy between individuals or genders. Running economy is therefore likely determined from the sum of influences from multiple lower-body attributes

Using a site-specific technical error to establish training responsiveness: a preliminary explorative study

Ryan M Weatherwax,1,2 Nigel K Harris,1 Andrew E Kilding,3 Lance C Dalleck2 1Auckland University of Technology, Human Potential Center, Auckland, New Zealand; 2Western State Colorado University, Recreation and Exercise &amp; Sport Science, Gunnison, CO, USA; 3Auckland University of Technology, Sports Performance Research Institute New Zealand, Auckland, New Zealand Background: Even though cardiorespiratory fitness (CRF) training elicits numerous health benefits, not all individuals have positive training responses following a structured CRF intervention. It has been suggested that the technical error (TE), a combination of biological variability and measurement error, should be used to establish specific training responsiveness criteria to gain further insight on the effectiveness of the training program. To date, most training interventions use an absolute change or a TE from previous findings, which do not take into consideration the training site and equipment used to establish training outcomes or the specific cohort being evaluated. The purpose of this investigation was to retrospectively analyze training responsive&shy;ness of two CRF training interventions using two common criteria and a site-specific TE.Methods: Sixteen men and women completed two maximal graded exercise tests and verification bouts to identify maximal oxygen consumption (VO2max) and establish a site-specific TE. The TE was then used to retrospectively analyze training responsiveness in comparison to commonly used criteria: percent change of &gt;0% and &gt;+5.6% in VO2max.Results: The TE was found to be 7.7% for relative VO2max. &chi;2 testing showed significant differences in all training criteria for each intervention and pooled data from both interventions, except between %&Delta; &gt;0 and %&Delta; &gt;+7.7% in one of the investigations. Training nonresponsiveness ranged from 11.5% to 34.6%.Conclusion: Findings from the present study support the utility of site-specific TE criterion to quantify training responsiveness. A similar methodology of establishing a site-specific and even cohort specific TE should be considered to establish when true cardiorespiratory training adaptations occur. Keywords: training responders, training nonresponders, cardiorespiratory fitness, exercise training&nbsp