Longitudinal Changes in the Oxygen Uptake Kinetic Response to Heavy-Intensity Exercise in 14- to 16-Year-Old Boys

There is another ORE record for this publication: http://hdl.handle.net/10036/3830This study examined longitudinal changes in the pulmonary oxygen uptake (p(V) over dotO(2)) kinetic response to heavy-intensity exercise in 14-16 yr old boys. Fourteen healthy boys (age 14.1 +/- 0.2 yr) completed exercise testing on two occasions with a 2-yr interval. Each participant completed a minimum of three 'step' exercise transitions, from unloaded pedalling to a constant work rate corresponding to 40% of the difference between the (p(V) over dotO(2)) (2), at the gas exchange threshold and peak (p(V) over dotO(2)) , (40% A). Over the 2-yr period a significant increase in the phase II time constant (25 5 vs. 30 +/- 5 s; p = .002, omega(2) = 0.34), the relative amplitude of the (p(V) over dotO(2)) slow component (9 +/- 5 vs. 13 +/- 4%; p = .036, omega(2) = 0.14) and the(p(V) over dotO(2)) gain at end-exercise (11.6 +/- 0.6 vs. 12.4 +/- 0.7 mL.min(-1).W-1; p < .001, omega(2) = 0.42) were observed. These data indicate that the control of oxidative phosphorylation in response to heavy-intensity cycling exercise is age-dependent in teenage boys

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

Componente lento do VO2 em crianças durante exercício pesado de corrida: análise com base em diferentes modelos matemáticos Componente lento de VO2 en niños durante ejercicio arduo de carrera: análisis con base en diferentes modelos matemáticos Slow component of VO2 in children during running exercise performed at heavy intensity domain: analysis with different mathematical models

O objetivo deste estudo foi verificar e quantificar a magnitude do componente lento do consumo de oxigênio (CL) em crianças submetidas a exercícios de corrida em esteira rolante, com cargas constantes de intensidade acima do limiar de lactato (75%D), utilizando para isso dois modelos de análise: a) modelo matemático com três termos exponenciais; e b) modelo deltaVO2 6-3min. Participaram do estudo oito crianças do sexo masculino (11,92 ± 0,63 anos; 44,06 ± 13,01kg; 146,63 ± 7,25cm; e níveis de maturação sexual 1 e 2), aparentemente saudáveis, não treinadas, que realizaram em diferentes dias: 1) teste incremental na esteira rolante para a determinação do consumo de oxigênio de pico (VO2pico) e do limiar de lactato (LL); e 2) dois testes de carga constante em esteira rolante durante seis minutos na intensidade de 75%delta [75%delta = LL + 0,75 x (VO2pico - LL)]. Para determinação do CL utilizaram-se: a) modelo matemático de três termos (Exp3); e b) a diferença no VO2 entre o sexto e o terceiro minuto de exercício (deltaVO2 6-3min). O CL foi expresso em valores absolutos (ml/min) e também como a contribuição percentual do CL para o aumento do VO2 no final do exercício (%CL). O CL determinado pelo modelo Exp3 (129,69 ± 75,71ml/min e 8,4 ± 2,92%) foi significantemente maior do que o obtido pelo modelo deltaVO2 6-3min (68,69 ± 102,54ml/min e 3,6 ± 7,34%). Portanto, os valores de CL obtidos em crianças durante o exercício de corrida realizado no domínio pesado (75%delta) são dependentes do modelo de análise (Exp3 x deltaVO2 6-3min).<br>El objetivo de este estudio ha sido el de verificar y cuantificar la magnitud del componente lento del consumo de oxígeno (CL) en niños, sometidos a ejercicios de carrera en cinta rodante, con cargas constantes de intensidad por encima del límite de lactato (75%delta), utilizando para esto dos modelos de análisis: a) modelo matemático con tres términos exponenciales; y b) modelo deltaVO2 6-3 min. Participaron del estudio 8 niños del sexo masculino (11,92 ± 0,63 años; 44,06 ± 13,01 kg; 146,63 ± 7,25 cm; y niveles de madurez sexual 1 y 2), aparentemente saludables, no entrenados, que realizaron en diferentes días: 1) Test incremental en la cinta rodante para determinar el consumo de oxígeno de pico (VO2pico) y del límite de lactato (LL); y 2) Dos tests de carga constante en cinta rodante durante seis minutos a intensidad de 75%delta [75%delta = LL + 0,75 x (VO2pico - LL)]. Para determinar el CL usamos: a) modelo matemático de tres términos (Exp3); y b) la diferencia en el VO2 entre el sexto y el tercer minuto de ejercicio (deltaVO2 6-3 min). El CL fue expresado en valores absolutos (ml/min) y también como contribución porcentual de CL para el aumento de VO2 al final del ejercicio (%CL). El CL determinado por el modelo Exp3 (129,69 ± 75,71 ml/min y 8,4 ± 2,92%) fue significativamente mayor al que fue obtenido por el modelo deltaVO2 6-3 min (68,69 ± 102,54 ml/min y 3,6 ± 7,34%). Por tanto, los valores de CL obtenidos en niños durante el ejercicio de carrera realizado en dominio pesado (75%delta) son dependientes del modelo de análisis (Exp3 x deltaVO2 6-3 min).<br>The purpose of this study was to identify and quantify the magnitude of the slow component of VO2 (SC) in children during running exercise, performed at heavy intensity domain (75%delta), using two different mathematical models: a) three-exponential model and; b) deltaVO2 6-3 min. Eight healthy male children (11.92 ± 0.63 years; 44.06 ± 13.01 kg; 146.63 ± 7.25 cm; and sexual maturity levels 1 and 2), not trained, performed in different days the following tests: 1) incremental running treadmill test to determine the peak oxygen uptake (VO2peak) and the lactate threshold (LT); and 2) two transitions from baseline to 75%delta [75%D = LT + 0.75 x (VO2 peak - LT)] for six minutes on treadmill. The SC was deter mined by two models: a) three-exponential model (Exp3); and b) the VO2 difference between the sixth and the third exercise minute (deltaVO2 6-3min). The SC was expressed as the absolute (ml/min) and percent contribution (%) to the total change in VO2. The SC values determined by model Exp3 (129.69 ± 75.71 ml/min and 8.4 ± 2.92%) and deltaVO2 6-3 min (68.69 ± 102.54 ml/min and 3.6 ± 7.34%) were significantly different. So, the SC values in children during running exercise performed at heavy intensity domain (75%delta) are dependent of the analysis model (Exp3 x deltaVO2 6-3 min)

Cinética do consumo de oxigênio e tempo limite na vvo2max: comparação entre homens e mulheres Oxygen uptake kinetics and threshold time at the vVO2max: tomparison between men and women

Foi investigada a influência do gênero no tempo limite (Tlim) e na cinética do VO2 durante corrida na velocidade associada ao VO2max (vVO2max) em nove homens e nove mulheres, todos adultos, jovens e sedentários, com idades entre 20 e 30 anos. Homens e mulheres realizaram dois testes em esteira rolante, sendo um teste incremental para determinar VO2max (42,66 ± 4,50 vs. 32,92 ± 6,03mL.kg-1.min-1) e vVO2max (13.2 ± 1.5 vs. 10,3 ± 2,0km.h-1), respectivamente. Um segundo teste com carga constante na vVO2max até a exaustão. O Tlim e a cinética do VO2 foram determinados. Não houve diferença significante entre homens e mulheres para constante de tempo (&#964;) (35,76 ± 21,03 vs. 36,5 ± 6,21s, respectivamente; P = 0,29); Tlim (308 ± 84,3 vs. 282,11 ± 57,19s, respectivamente; P = 0,68), tempo para atingir o VO2max (TAVO2max) (164,48 ± 96,73 vs. 167,88 ± 28,59s, respectivamente; P = 0,29), tempo para atingir o VO2max em percentual do Tlim (%Tlim) (50,24 ± 16,93 vs. 62,63 ± 16,60%, respectivamente; P = 0,19), tempo mantido no VO2max (TMVO2max) (144,08 ± 42,55 vs. 114,23 ± 76,96s, respectivamente; P = 0,13). Estes resultados sugerem que a cinética do VO2 e o Tlim são similares entre homens e mulheres sedentários na vVO2max.<br>The aim of this study was to investigate the influence of gender on Tthre and VO2 response during running exercise performed at vVO2max. Therefore, eighteen untrained individuals (9 male and 9 female) with normal weight and aged between 20 - 30 years (VO2max = 42.66 ± 4.50 vs 32.92 ± 6.03 mL.kg-1.min-1 and vVO2max = 13.2 ± 1.5 vs 10.3 ± 2.0 km.h-1, for male and female, respectively) were assessed. Subjects performed two exercise tests on treadmill. First one was an incremental test to determine VO2max, velocity at VO2max (vVO2max) and second test was performed at steady velocity - vVO2max - until exhaustion. The threshold time (Tthre) and VO2 kinetics response was determined. No significant differences were observed between men and women for time constant (&#964;) (35.76 ± 21.03 vs 36.5 ± 6.21s, respectively; P = 0.29); Tthre (308 ± 84.3 vs 282.11 ± 57.19s, respectively; P = 0.68), time to achieve VO2max (TAVO2max) (164.48 ± 96.73 vs 167.88 ± 28.59s, respectively; P = 0.29), time to achieve VO2max in Tthre percentage (%Tthre) (50.24 ± 16.93 vs 62.63 ± 16.60%, respectively; P = 0.19); time maintained at VO2max (TMVO2max) (144.08 ± 42.55 vs 114.23 ± 76.96s, respectively; P = 0.13). These results suggest that the VO2 kinetics response and Tthre is similar between untrained men and women at the vVO2max

The oxygen uptake kinetic response to moderate intensity exercise in overweight and non-overweight children

Objective: To compare the phase II oxygen uptake time constant (τV′O2) and V′O2 mean response time (V′O2MRT) in overweight (OW) and non-OW (NO) children during moderate intensity exercise. Design: Between subjects where participants completed a maximal ramp exercise test on an electromagnetically braked cycle ergometer to determine peak V′O2 (V′O2peak) and gas exchange threshold (GET). Gas exchange was measured breath-by-breath using a mass spectrometer. On subsequent visits, 6 square-wave transitions (less than or equal to2 per day) from 0 W to 90% GET were completed. Individual phase II τV′O2 and V′O2MRTs were estimated from time aligned average V′O2 traces. Subjects: Eleven OW (11.8±0.4 years) and 12 NO (11.9±0.4 years) children were recruited to the study. The OW group was significantly heavier (62.9±9.7 vs 39.4±5.8 kg, P<0.001), taller (1.58±0.05 vs 1.47±0.07 m, P<0.001) and had a higher body mass index (25.8±3.4 vs 18.3±1.8 kg m−2, P<0.001). Results: Both τV′O2 (30.2±9.6 vs 22.8±7.1 s, P0.05); absolute V′O2 at GET was similar between OW and NO groups (0.94±0.24 vs 0.78±0.27 l min−1, P>0.05); GET expressed as percentage of V′O2peak was similar between the groups (42.0±0.1 vs 44.8±0.1%, P>0.05). Conclusion: These findings demonstrate impairment in the factors determining V′O2 kinetics in OW children at a relatively young age. Furthermore, assessment of cardiorespiratory fitness using peak exercise values is likely to be misleading and not useful when designing exercise programmes for OW children