This study examined: 1) if estimated performance times (ETcom) at four different distances can be used to accurately define the parameters of the critical velocity (CV) test [CV and anaerobic running capacity (ARC)]; and 2) if those parameters can be used to predict time to completion (PTcom) of distances performed at velocities greater than CV. Twelve subjects provided an ETcom for maximal-effort runs at 400m, 800m, 1600m, and 3200m. The CV and ARC were derived from the total distance (TD) versus ETcom relationship. The equation: PTcom = ARC / (velocity-CV) was used to determine the PTcom for runs at 200m, 600m, and 1000m. The PTcom was validated against the actual time to complete (ATcom) runs at the same three distances. The TD versus ETcom relationship was highly linear and indicated a close relationship between running distance and time. The PTcom overestimated the ATcom at 200m, but was not different from ATcom at 600m and 1000m. The PTcom and ATcom were not related at any of the three distances. The CV model could be applied to estimated performance times to derive the CV and ARC parameters, but the parameters of the test did not accurately estimate performance times above CV.

No description available.

Abstract Helium is the second most abundant element in the Universe. It is the only known substance that can exist in liquid state at absolute zero. There are two stable isotopes of helium, fermionic ³He and bosonic ⁴He. At sufficiently low temperatures, both isotopes undergo a phase transition into a superfluid state. These superfluids are usually characterised by their ability to flow without resistance, but this is by no means their only remarkable property. In this thesis, we study theoretically superfluid ³He. The work consists of two separate projects. First, we study the effect of a quantised vortex line to spin dynamics of the superfluid. We find that the interplay between the vortex and the magnetisation of the liquid generates spin waves, dissipating energy. We find that the theoretically predicted energy dissipation is in agreement with experimental data, implying that spin-wave radiation can be an important mechanism of magnetic relaxation in superfluid ³He. Second, we study the drag force acting on an object moving through zero-temperature superfluid at a constant velocity. The drag arises if momentum is transferred from the object to the fluid. At low velocities, no such mechanism exist and thus the drag vanishes. If the velocity exceeds the Landau velocity \(v_L\), it becomes possible for the object to create quasiparticle excitations that could, in principle, transfer momentum away from the object. Thus, \(v_L\) has been generally assumed to be the critical velocity, that is, the velocity above which the drag force starts to increase rapidly towards the normal-state value. We find that this is not necessarily the case. Objects much larger than the superfluid coherence length modify the superfluid flow field around them. The spatial variation of the flow field can shield the object, preventing quasiparticles from transferring momentum away from the object. This leads to a critical velocity greater than \(v_L\). / Original papers The original publications are not included in the electronic version of the dissertation. Laine, S. M., & Thuneberg, E. V. (2016). Calculation of Leggett–Takagi Relaxation in Vortices of Superfluid ³He-B. Journal of Low Temperature Physics, 183(3–4), 222–229. https://doi.org/10.1007/s10909-016-1516-x Kuorelahti, J. A., Laine, S. M., & Thuneberg, E. V. (2018). Models for supercritical motion in a superfluid Fermi liquid. Physical Review B, 98(14). https://doi.org/10.1103/physrevb.98.144512 http://jultika.oulu.fi/Record/nbnfi-fe2018112148794 Laine, S. M., & Thuneberg, E. V. (2018). Spin-wave radiation from vortices in ³He−B. Physical Review B, 98(17). https://doi.org/10.1103/PhysRevB.98.174516 http://jultika.oulu.fi/Record/nbnfi-fe2019092630083

No description available.

Master of Science / Department of Kinesiology / Thomas J. Barstow / Purpose: To determine if a single test is accurate in determining the parameters of the velocity: time-to-fatigue relationship, i.e., critical velocity (CV) and a finite distance that can be covered above CV (D`). Methods: Ten healthy subjects completed an incremental test to volitional exhaustion followed by four constant-velocity runs on a treadmill for the determination of CV and D`, as well as an all-out 3-minute test on a track for the determination of end-test velocity (EV) and the distance above end-test velocity (DEV). Eight of the eleven subjects completed a second 3-minute test and one run each at (+) and (-) 95% confidence interval velocities of CV determined from the 1/time model. Results: The group mean 1/time model CV (12.8 ± 2.5 km·h[superscript]-1) was significantly greater than the velocity-time model CV (12.3 ± 2.4 km·h[superscript]-1; P < 0.05), while the velocity-time model W` (285 ± 106 m) was greater than the 1/time model W` (220 ± 112 m; P < 0.05). EV (13.0 ± 2.7 km·h[superscript]-1) and DEV (151 ± 45 m) were not significantly different than the 1/time model CV and W`, respectively. EV was greater than the velocity-time model CV (P < 0.05), while the DEV was significantly less than the velocity-time model W` (P = 0.002). No difference was found for group mean EV or DEV between the two 3-minute tests (P > 0.05), which demonstrated a reliability coefficient of 0.85 for EV and 0.32 for DEV. For the CV (-) 95% run, all subjects reached a steady-state in VO[subscript]2, and completed 900 s of exercise. However, for the CV (+) 95% run, VO[subscript]2 never reached a steady-state, but increased until termination of exercise at 643 ± 213 s with a VO[subscript]2peak close to but significantly lower than VO[subscript]2max (P < 0.05). Conclusion: CV can be accurately determined using a single 3-minute test, while W` is underestimated with this protocol.

Cette thèse a pour objectif la caractérisation de la vitesse de ventilation critique dans un tunnel ventilé longitudinalement lorsque survient un incendie. La vitesse critique est définie comme la vitesse de ventilation minimale pour laquelle l’ensemble des fumées nocives est repoussé à l’aval de l’incendie. Les méthodes utilisées sont théoriques, expérimentales et numériques. Dans une première approche, l’incendie est modélisé par un rejet de fluide plus léger que l’air ambiant. Dans les expériences, il s’agit soit de l’air chaud, soit d’un mélange d’air et d’hélium ce qui permet d’étudier les effets dits non-Boussinesq, c’est à dire induits par une large différence de densité entre le rejet flottant et l’air ambiant. Une modélisation théorique simple est également donnée afin d’expliquer les variations de la vitesse de ventilation critique en fonction des conditions à la source du rejet (flux de flottabilité et géométrie). Un bon accord est observé entre les résultats expérimentaux et le modèle théorique aussi bien pour les rejets dits forces (jets) que pour les rejets dits flottants (panaches). Des simulations numériques ont été également menées afin de fournir une comparaison quantitative des vitesses critiques obtenues dans le cas d’un incendie modélisé par un panache et le cas d’un feu. L’apparition d’une vitesse dite ’super-critique’ observée dans la littérature dans le cas de feux a été étudiée. L’effet sur la vitesse critique d’un feu de puissance faible peut très largement être modélisé par l’effet d’un rejet de fluide léger au sol. En revanche, un feu de forte puissance nécessite une modélisation des flammes et donc de puissance thermique produite en volume dans une partie non négligeable du tunnel. La présence de flammes représente donc une source distribuée de flux de flottabilité au-dessus et en aval du lieu d’injection des gaz de combustion. En conséquence, dans cette situation, le foyer ne peut être modélisé par une simple condition aux limites au sol du tunnel. L’effet sur la vitesse critique d’une éventuelle inclinaison ou pente du tunnel a été également étudié. Une inclinaison du tunnel dans le sens de la ventilation induit une diminution de la vitesse critique par rapport à un tunnel horizontal alors que pour une inclinaison en sens contraire la vitesse critique est augmentée. Cependant, cet effet dépend des conditions à la source du rejet. Pour les rejets flottants, l’effet de la pente du tunnel est important tandis que la vitesse critique devient de moins en moins dépendante de la pente au fur et à mesure que le rejet devient force. Le modèle théorique développé pour un rejet dans un tunnel horizontal a été adapté au cas avec pente et un bon accord a de nouveau été établi entre les résultats expérimentaux et le modèle théorique. Enfin, pour un feu, les simulations numériques ont montré que la pente influence très peu la vitesse critique. Dans une dernière partie, l’effet de la présence de véhicules dans le tunnel a été investigue aussi bien expérimentalement qu’avec l’outil numérique. Les véhicules sont modélisés par des blocs parallélépipédiques de différentes tailles places en amont de la source de flottabilité ou le feu. Il a été montré que seul le bloc proche de la source modifiait la valeur de la vitesse de ventilation critique alors que les blocs plus éloignés avaient une influence négligeable. De même, la vitesse critique obtenue en présence de blocs se rapproche très rapidement de celle obtenue pour un tunnel sans véhicule lorsque la distance entre la source et le bloc le plus proche augmente. Le paramètre qui influence le plus la vitesse critique est la position relative du bloc et de la source. Lorsque le bloc protège directement la source en étant placé à son côté aussi bien longitudinalement que latéralement, l’air frais de la ventilation n’impacte pas directement le rejet et la vitesse critique est augmentée par rapport à la situation sans bloc. [...] / This thesis investigates experimentally, theoretically and numerically the critical ventilation velocity in longitudinal ventilated tunnels in case of a fire. The critical velocity is defined as the minimum ventilation velocity that confines the front of the backlayer of harmful buoyant gases downwind of the source of emission. The fire is first modeled by a release of light gas in ambient air. In the experiments, the light fluid is an air/helium mixture. A simple mathematical model, based on the classical plume study, is formulated to interpret the variations of the critical velocity as a function of the source conditions (momentum and buoyancy fluxes and geometry). A good agreement is observed between the experimental results and the theoretical predictions for both the momentum-driven and buoyancy-driven releases. In addition, the non-Boussinesq effects, i.e. related to large differences between the densities of the buoyant plume and the ambient fluid, could be suitably modeled. Subsequently, the difference between a buoyant plume and a fire is studied, by combining experiments and numerical simulations. The reason for the appearance of the so-called ‘super-critical’ velocity, a ventilation velocity that becomes independent of the heat release rate when it becomes large, is discussed. It is shown that small fires can be reliably modeled as buoyant densimetric plumes released at ground level. The dynamics induced by larger fires require instead the modeling of large flames and hence a volumetric source of heat and buoyancy within the tunnel. In the simulation of fires, when the heat release rate is increased, the volume of combustion also increases, but the critical velocity remains nearly constant, which validates the appearance of the ‘super-critical’ velocity. The effect of tunnel inclination on the critical velocity is then studied. The influence of slope (defined as negative when the entrance of fresh air is at a lower elevation than the source) on the movement of smoke is mainly related to the role of the component of buoyancy along the tunnel axis. A positive slope helps the formation of the backlayer, while a negative slope helps reaching the critical condition. However, this effect depends on the source condition. Our experiments and numerical simulations on densimetric plumes suggest that the dynamical condition at the source affects the critical velocity of a buoyant plume: when the buoyant plume is momentum-driven, the influence of slope is small; when the buoyant plume is buoyancy-driven, the influence of slope is large. This behavior can be well described by a theoretical model based on the previous model of the critical velocity in a horizontal tunnel. These results have been extended to the case of fires by conducting numerical simulations and there is again a good agreement between the observed results and the theoretical model. In particular, the ratio of the critical velocities obtained for an inclined and an horizontal tunnel is independent of the power of the fire. Finally, the effect of vehicular blockage on the critical velocity is studied experimentally and numerically. The vehicles are modeled by blocks of different sizes placed upstream of the buoyancy or fire source. It is shown that only the block close to the source affects the critical velocity, whereas the effect of other blocks of the same size located further upstream is negligible. As the fire-blockage distance becomes larger, the critical velocity changes and becomes close to the value in an empty tunnel. The relative position between the blocks and the fire source has large influence on the critical velocity. When the blocks are placed at the center laterally, the ventilation flow cannot reach the fire plume directly, a larger critical velocity is needed compared with that in a corresponding empty tunnel. [...]

Modelos bioenergéticos de dois, três e quatro parâmetros podem ser usados para prescrever a velocidade crítica (VC) sendo que o último modelo melhor descreve a relação entre velocidade (v) e tempo de exaustão (tlim) em nadadores. O objetivo do presente estudo foi verificar as respostas metabólicas ao se nadar em intensidade equivalente à VC4par até exaustão e verificar a validade de predizê-la somente por meio de um teste de 400 m em nado crawl (T400). Para tal, esta pesquisa foi desenvolvida em duas etapas: na primeira, oito nadadores e quatro nadadoras classificados entre os oito melhores em suas provas no último Campeonato Brasileiro Juvenil de Natação (15,6 ± 0,9 anos, 63,0 ± 7,2 kg, 174,9 ± 8,3 cm de estatura, 180,7 ± 10,4 cm de envergadura, 280,2 ± 17,6 s nos 400 m nado crawl = 78,7 ± 3,3 % do recorde mundial para a prova em piscina de 25 m) realizaram testes máximos de 50, 100, 200, 400, 800 e 1500 m em ordem randomizada e com 24 h de intervalo para calcular a VC4par. Na segunda etapa, consumo de oxigênio (VO2), concentração de lactato sanguíneo ([La]), frequência cardíaca (FC) e esforço percebido (EP, escala de Borg de 6-15) foram mensurados no repouso, após o aquecimento, à cada 10 min e na exaustão em um teste retangular com velocidade controlada com duração máxima de 60 min correspondente à VC4par. Resultados: os nadadores suportaram nadar à 100% da VC4par entre 13 e 62 min. O VO2 se estabiliza a partir de, aproximadamente 10 min de teste, não atingindo seu valor máximo antes da exaustão (63,2 ± 10,5% do VO2max). [La] comportase entre uma faixa de estabilização a aumentos sem estabilização (7,2 ± 1,8 mmol·l-1 na exaustão). FC no momento exaustão situou-se em 93,0 ± 4,9da FCmax. EP aumenta sem estabilizar-se (18,3 ± 1,7 na exaustão). A relação entre a VC4par e a VN do T400 (V400) em nadadores de nível nacional é obtida pela equação VC4par = (0,9252 * V400) – 0,01. Conclusão: A VC4par situa-se no domínio de intensidade muito pesado, próxima ao limite inferior do mesmo e pode ser prescrita pelo T400. / Two, three and four bioenergetic parameter models can be used to prescribe the critical velocity (VC). The four-parameter model best describes the relationship between velocity (v) and time to exhaustion (tlim) in swimmers. The aim of this study was to determine the metabolic responses when swimming in intensity equivalent to VC4par until exhaustion and verify the validity of predicting it only through a test on 400 m front crawl (T400). To this end, this research was conducted in two stages: stage one, eight male swimmers and four female swimmers ranked among the top eight in their events at the last Brazilian Youth Swimming Championship (15.6 ± 0.9 years, 63.0 ± 7,2 kg, 174.9 ± 8.3 cm in height, 180.7 ± 10.4 cm of arm span, 280.2 ± 17.6 s in the 400 m freestyle = 78.7 ± 3.3% of world record short course) conducted maximum efforts of 50, 100, 200, 400, 800 and 1500 m in randomized order and with 24 hours of interval for calculating the VC4par. In the second stage, oxygen consumption (VO2), blood lactate concentration ([La]), heart rate (FC) and perceived exertion (EP, Borg scale 6-15) were measured at rest, after warm up, every 10 min and at exhaustion during a rectangular test with controlled speed, with a maximum duration of 60 min at 100%VC4par. Results: swimmers supported between 13 and 62 min at 100%VC4par. At this intensity VO2 stabilizes from approximately 10 minutes of testing, not reaching its maximum value before the exhaustion (10.5 ± 63.2 %VO2max). [La] behaves within the range of stabilization increases without stabilization (7.2 ± 1.8 mmol · l-1 in the exhaustion). FC at exhaustion stood at 93.0 ± 4.9% FCmax. EP increases without stabilizing (18.3 ± 1.7 in the exhaustion). The relationship between VC4par and the swimming velocity of the T400 (V400) in swimmers of national level can be obtained by equation VC4par = (0.9252 * V400) - 0.01. Conclusion: VC4par lies to the very heavy intensity domain, near the lower limit, and can be prescribed by the T400.

Modelos bioenergéticos de dois, três e quatro parâmetros podem ser usados para prescrever a velocidade crítica (VC) sendo que o último modelo melhor descreve a relação entre velocidade (v) e tempo de exaustão (tlim) em nadadores. O objetivo do presente estudo foi verificar as respostas metabólicas ao se nadar em intensidade equivalente à VC4par até exaustão e verificar a validade de predizê-la somente por meio de um teste de 400 m em nado crawl (T400). Para tal, esta pesquisa foi desenvolvida em duas etapas: na primeira, oito nadadores e quatro nadadoras classificados entre os oito melhores em suas provas no último Campeonato Brasileiro Juvenil de Natação (15,6 ± 0,9 anos, 63,0 ± 7,2 kg, 174,9 ± 8,3 cm de estatura, 180,7 ± 10,4 cm de envergadura, 280,2 ± 17,6 s nos 400 m nado crawl = 78,7 ± 3,3 % do recorde mundial para a prova em piscina de 25 m) realizaram testes máximos de 50, 100, 200, 400, 800 e 1500 m em ordem randomizada e com 24 h de intervalo para calcular a VC4par. Na segunda etapa, consumo de oxigênio (VO2), concentração de lactato sanguíneo ([La]), frequência cardíaca (FC) e esforço percebido (EP, escala de Borg de 6-15) foram mensurados no repouso, após o aquecimento, à cada 10 min e na exaustão em um teste retangular com velocidade controlada com duração máxima de 60 min correspondente à VC4par. Resultados: os nadadores suportaram nadar à 100% da VC4par entre 13 e 62 min. O VO2 se estabiliza a partir de, aproximadamente 10 min de teste, não atingindo seu valor máximo antes da exaustão (63,2 ± 10,5% do VO2max). [La] comportase entre uma faixa de estabilização a aumentos sem estabilização (7,2 ± 1,8 mmol·l-1 na exaustão). FC no momento exaustão situou-se em 93,0 ± 4,9da FCmax. EP aumenta sem estabilizar-se (18,3 ± 1,7 na exaustão). A relação entre a VC4par e a VN do T400 (V400) em nadadores de nível nacional é obtida pela equação VC4par = (0,9252 * V400) – 0,01. Conclusão: A VC4par situa-se no domínio de intensidade muito pesado, próxima ao limite inferior do mesmo e pode ser prescrita pelo T400. / Two, three and four bioenergetic parameter models can be used to prescribe the critical velocity (VC). The four-parameter model best describes the relationship between velocity (v) and time to exhaustion (tlim) in swimmers. The aim of this study was to determine the metabolic responses when swimming in intensity equivalent to VC4par until exhaustion and verify the validity of predicting it only through a test on 400 m front crawl (T400). To this end, this research was conducted in two stages: stage one, eight male swimmers and four female swimmers ranked among the top eight in their events at the last Brazilian Youth Swimming Championship (15.6 ± 0.9 years, 63.0 ± 7,2 kg, 174.9 ± 8.3 cm in height, 180.7 ± 10.4 cm of arm span, 280.2 ± 17.6 s in the 400 m freestyle = 78.7 ± 3.3% of world record short course) conducted maximum efforts of 50, 100, 200, 400, 800 and 1500 m in randomized order and with 24 hours of interval for calculating the VC4par. In the second stage, oxygen consumption (VO2), blood lactate concentration ([La]), heart rate (FC) and perceived exertion (EP, Borg scale 6-15) were measured at rest, after warm up, every 10 min and at exhaustion during a rectangular test with controlled speed, with a maximum duration of 60 min at 100%VC4par. Results: swimmers supported between 13 and 62 min at 100%VC4par. At this intensity VO2 stabilizes from approximately 10 minutes of testing, not reaching its maximum value before the exhaustion (10.5 ± 63.2 %VO2max). [La] behaves within the range of stabilization increases without stabilization (7.2 ± 1.8 mmol · l-1 in the exhaustion). FC at exhaustion stood at 93.0 ± 4.9% FCmax. EP increases without stabilizing (18.3 ± 1.7 in the exhaustion). The relationship between VC4par and the swimming velocity of the T400 (V400) in swimmers of national level can be obtained by equation VC4par = (0.9252 * V400) - 0.01. Conclusion: VC4par lies to the very heavy intensity domain, near the lower limit, and can be prescribed by the T400.

Modelos bioenergéticos de dois, três e quatro parâmetros podem ser usados para prescrever a velocidade crítica (VC) sendo que o último modelo melhor descreve a relação entre velocidade (v) e tempo de exaustão (tlim) em nadadores. O objetivo do presente estudo foi verificar as respostas metabólicas ao se nadar em intensidade equivalente à VC4par até exaustão e verificar a validade de predizê-la somente por meio de um teste de 400 m em nado crawl (T400). Para tal, esta pesquisa foi desenvolvida em duas etapas: na primeira, oito nadadores e quatro nadadoras classificados entre os oito melhores em suas provas no último Campeonato Brasileiro Juvenil de Natação (15,6 ± 0,9 anos, 63,0 ± 7,2 kg, 174,9 ± 8,3 cm de estatura, 180,7 ± 10,4 cm de envergadura, 280,2 ± 17,6 s nos 400 m nado crawl = 78,7 ± 3,3 % do recorde mundial para a prova em piscina de 25 m) realizaram testes máximos de 50, 100, 200, 400, 800 e 1500 m em ordem randomizada e com 24 h de intervalo para calcular a VC4par. Na segunda etapa, consumo de oxigênio (VO2), concentração de lactato sanguíneo ([La]), frequência cardíaca (FC) e esforço percebido (EP, escala de Borg de 6-15) foram mensurados no repouso, após o aquecimento, à cada 10 min e na exaustão em um teste retangular com velocidade controlada com duração máxima de 60 min correspondente à VC4par. Resultados: os nadadores suportaram nadar à 100% da VC4par entre 13 e 62 min. O VO2 se estabiliza a partir de, aproximadamente 10 min de teste, não atingindo seu valor máximo antes da exaustão (63,2 ± 10,5% do VO2max). [La] comportase entre uma faixa de estabilização a aumentos sem estabilização (7,2 ± 1,8 mmol·l-1 na exaustão). FC no momento exaustão situou-se em 93,0 ± 4,9da FCmax. EP aumenta sem estabilizar-se (18,3 ± 1,7 na exaustão). A relação entre a VC4par e a VN do T400 (V400) em nadadores de nível nacional é obtida pela equação VC4par = (0,9252 * V400) – 0,01. Conclusão: A VC4par situa-se no domínio de intensidade muito pesado, próxima ao limite inferior do mesmo e pode ser prescrita pelo T400. / Two, three and four bioenergetic parameter models can be used to prescribe the critical velocity (VC). The four-parameter model best describes the relationship between velocity (v) and time to exhaustion (tlim) in swimmers. The aim of this study was to determine the metabolic responses when swimming in intensity equivalent to VC4par until exhaustion and verify the validity of predicting it only through a test on 400 m front crawl (T400). To this end, this research was conducted in two stages: stage one, eight male swimmers and four female swimmers ranked among the top eight in their events at the last Brazilian Youth Swimming Championship (15.6 ± 0.9 years, 63.0 ± 7,2 kg, 174.9 ± 8.3 cm in height, 180.7 ± 10.4 cm of arm span, 280.2 ± 17.6 s in the 400 m freestyle = 78.7 ± 3.3% of world record short course) conducted maximum efforts of 50, 100, 200, 400, 800 and 1500 m in randomized order and with 24 hours of interval for calculating the VC4par. In the second stage, oxygen consumption (VO2), blood lactate concentration ([La]), heart rate (FC) and perceived exertion (EP, Borg scale 6-15) were measured at rest, after warm up, every 10 min and at exhaustion during a rectangular test with controlled speed, with a maximum duration of 60 min at 100%VC4par. Results: swimmers supported between 13 and 62 min at 100%VC4par. At this intensity VO2 stabilizes from approximately 10 minutes of testing, not reaching its maximum value before the exhaustion (10.5 ± 63.2 %VO2max). [La] behaves within the range of stabilization increases without stabilization (7.2 ± 1.8 mmol · l-1 in the exhaustion). FC at exhaustion stood at 93.0 ± 4.9% FCmax. EP increases without stabilizing (18.3 ± 1.7 in the exhaustion). The relationship between VC4par and the swimming velocity of the T400 (V400) in swimmers of national level can be obtained by equation VC4par = (0.9252 * V400) - 0.01. Conclusion: VC4par lies to the very heavy intensity domain, near the lower limit, and can be prescribed by the T400.

Orientador: Orival Andries Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Educação Fisica / Made available in DSpace on 2018-08-13T09:03:55Z (GMT). No. of bitstreams: 1 Machado_MarcusVinicius_M.pdf: 1831761 bytes, checksum: 3d1c64a2f4672ba2b4551a2f3c4ccb0b (MD5) Previous issue date: 2009 / Resumo: Os objetivos do presente estudo foram: a) avaliar o efeito de 12 semanas de treinamento sobre a velocidade crítica (VC) e o limiar anaeróbio (LAn) em nadadores; b) verificar a correlação da VC com o máximo estado estável do lactato (MEEL) de nadadores adolescentes de elite; c) verificar a influência da utilização de diferentes combinações de distâncias sobre os valores da VC e CTAn (capacidade de trabalho anaeróbio) em nadadores. Participaram do estudo 33 nadadores com idades entre 13 a 21 anos. A VC foi determinada através do coeficiente angular da reta de regressão linear entre a distância e o tempo obtido em cinco tiros máximos (50, 100, 200, 400 e 800m). Para a determinação do LAn foram realizadas três séries de quatro repetições de 400m (3 x 4 x 400m) a 98, 100 e 102% da VC, com pausa de 45 s entre os tiros e intervalo de 48 hs entre as séries. Foram coletados 25 ?l de sangue da ponta dos dedos durante o repouso e ao final de cada tiro. O LAn foi definido como a mais alta intensidade de nado na qual ocorra um platô no lactato sanguíneo. Os testes para a determinação da VC e do LAn foram repetidos após 12 semanas de treinamento. Para a comparação da VC entre os momentos utilizou-se o teste de Wilcoxon. O teste t de Student foi utilizado na comparação entre os tiros máximos nos dois momentos. A correlação linear de Pearson foi empregada na comparação entre a VC e o MEEL. A ANOVA one-way foi utilizada para comparar a concentração de lactato sanguíneo nos tiros de 400m nas três intensidades (98, 100 e 102%) e na comparação entre as diferentes combinações de tiros e o Post Hoc de Tukey quando P<0,05. A VC obtida no momento pós doze semanas de treinamento foi significativamente maior quando comparada com o momento pré (1,45 ± 0,10 vs 1,41 ± 0,11 m/s-1). No entanto, não foram observadas diferenças significativas no LAn entre os momentos pré e pós (1,41 ± 0,10 vs 1,43 ± 0,10 m/s-1). Observou-se também uma diminuição na concentração média de lactato entre os momentos. A VC superestimou o MEEL dos nadadores jovens (1,32 ± 0,06 vs 1,29 ± 0,05), sendo que o MEEL foi observado na intensidade de 98% da VC no grupo analisado. Observou-se também que nas diferentes combinações de tiros, as distâncias menores (50, 100 e 200m) proporcionaram maiores valores da VC (1,47 ± 0,13), causando com isso uma diminuição na CTAn (11,91 ± 2,61). A utilização de tiros de média e longa distância proporcionou valores mais baixos para a VC (1,38 ± 0,10, 1,34 ± 0,09 e 1,36 ± 0,09) quando comparados com os tiros curtos, respectivamente para 100, 200 e 400m; 200, 400 e 800m; 50, 100, 200, 400 e 800m. Através dos resultados obtidos, conclui-se que: a) 12 semanas de treinamento foram suficientes para promover um aumento na VC. O mesmo comportamento não foi observado com o MEEL, entretanto, a diminuição da concentração média de lactato no momento pós-experimental demonstrou uma adaptação ao treinamento e a maior eficiência do sistema aeróbio; b) a VC pode não corresponder ao MEEL em nadadores adolescentes de elite. Entretanto, a alta correlação encontrada entre os métodos sugerem a utilização da VC de forma fidedigna na prescrição e monitoramento do treinamento desses atletas; c) a distância dos tiros possui grande influência sobre os valores da VC e da CTAn, podendo com isso superestimar ou subestimar a velocidade correspondente à máxima fase estável do lactato. / Abstract: The objectives of this study were: a) verify the effect of 12 weeks of training on the critical velocity (CV) and anaerobic threshold (AT) in swimmers; b) verify the correlation between CV and maximal lactate steady state (MLSS) in teenagers elite swimmers; c) the influence of using different combinations of distances on the values of CV and anaerobic work capacity (AWC) in swimmers. Study participants were thirty-three swimmers aged 13 to 21 years. The CV was determined by the slope of the linear regression between the distance and time in five maximum shots (50, 100, 200, 400 and 800m). To determine the AT subjects were submitted to three sets with four repetitions of 400 meters (3 x 4 x 400m) at 98, 100 and 102% of CV, with break of 45 seconds between shots and 48-hour interval between series. We collected 25 ?l of blood from fingertips during rest and at the end of each shot. The AT was defined as the highest intensity of swimming in which a plateau appears in blood lactate curve. The tests for determining the CV and AT were repeated after 12 weeks of training. For comparison between CV and the distinct moments Wilcoxon test was used. With Student t test we compare the maximum shots in two periods. The linear Pearson correlation was used in the comparison between the CV and MLSS. The one-way ANOVA compared the concentration of lactate in the firing of 400m for three intensities (98, 100 and 102%) and the different combinations of shots with the Post Hoc Tukey when P <0.05. The CV obtained at the time after twelve weeks of training was significantly higher when compared with the previous moment (1.45 ± 0.10 vs. 1.41 ± 0.11 m/s-1, P <0.05). However, no significant differences were seen in AT between the moment before and after (1.41 ± 0.10 vs. 1.43 ± 0.10 m/s-1, respectively). There was also a decrease in the average concentration of lactate between times. The CV overestimated the MLSS of young swimmers (1.32 ± 0.06 vs. 1.29 ± 0.05 respectively), while MLSS was observed in the intensity of 98% of CV in the group analyzed. It was also observed that on different combinations of fire, the shorter distances (50, 100 and 200m) provided higher values of VC (1.47 ± 0.13), which caused a decrease in AWC (11.91 ± 2, 61). The use of medium and long distance fires lead to lower values for CV (1.38 ± 0.10, 1.34 ± 0.09 and 1.36 ± 0.09) when compared with the short shots, respectively, for 100, 200 and 400 meters; 200, 400 and 800meters; 50, 100, 200, 400 and 800m. With the results obtained, it is concluded that: a) 12 weeks of training was sufficient to promote an increase in CV. However, although it has not promoted a significant increase in AT between times, the decrease in average concentration of lactate at post-trial demonstrated greater efficiency for the aerobic capacity, promoting a lower wear of athletes during the tests; b) CV does not correspond to the MLSS in adolescents of elite swimmers. However, the high correlation found between the methods suggest the use of CV in a reliable manner in prescribing and monitoring training of these athletes, c) Shot distance has great influence on the values of CV and AWC, and could underestimate or overestimate the speed corresponding to the maximum steady state of lactate. / Mestrado / Biodinamica do Movimento Humano / Mestre em Educação Física