Estudo piloto da resposta bioenergética a diferentes ritmos respiratórios na técnica de mariposa

Introdução e objectivos: O objectivo do presente trabalho foi o de efectuar um estudo piloto, comparando a resposta bioenergética à adopção de diferentes ritmos respiratórios na técnica de Mariposa. Material e métodos: Foram estudadas duas nadadoras e um nadador de nível nacional (17.0±3.6 anos de idade, 159.0±12.0cm de estatura, 56.9±10.3Kg de massa corporal e 18.0±8.9% de massa gorda). Cada nadador efectuou, numa piscina de 25m, 3 repetições de 200m, a uma velocidade tão próxima quanto possível da máxima. De forma aleatória, em cada repetição, os nadadores realizaram inspirações frontais em todos os ciclo gestuais (1:1F), uma inspiração frontal em cada dois ciclos gestuais (1:2F) e ciclo gestuais inspirando pelo tubo de condução de gases, mas sem a emersão da face (0:0). Avaliaram-se as trocas gasosas e os parâmetros cardiorespiratórios através de um oxímetro breath-by-breath (K4 b2, Cosmed, Itália). Uma válvula de baixa resistência hidrodinâmica encontrava-se ligada ao oxímetro, permitindo a recolha das amostras de gases a analisar (Toussaint et al., 1987; Keskinen et al. 2003). Foram retiradas amostras de sangue capilar da orelha antes, imediatamente após cada 200m e 1, 3, 5 e 7 minutos depois do fim do protocolo, para a avaliação da concentração sérica de lactato (YSI ASPECTOS BIOLÓGICOS DO DESPORTO E DO EXERCÍCIO Revista Portuguesa de Ciências do Desporto, 2004, vol. 4, nº 2 (suplemento) [237–274] 241 1500L, Yellow Springs, EUA). Foi utilizado um cardiofrequencímetro para medição da frequência cardíaca (Vantage NV, POLAR, Finlândia). Foi avaliado o consumo máximo de oxigénio relativo (VO2-max), o consumo líquido de oxigénio (VO2- net=VO2-max-VO2-repouso), a concentração máxima de lactato (La-max), a concentração líquida de lactato (La-net= Lamax- La-repouso), o quociente respiratórios (R), o volume ventilatório (VV) e a frequência cardíaca (FC). Também foram avaliados o dispêndio energético total (Etot) calculado com base no VO2-net e na La-net, transformada em equivalentes de VO2 através da constante de 2.7 ml.kg.-1.mmol-1 (di Prampero et al., 1978) e o custo energético (CE= Etot .velocidade-1). Principais resultados e conclusões: O VO2-max foi 26.0% superior utilizando o ritmo de 1:1F do que o ritmo de 0:0 e 7.25% superior do que o ritmo de 1:2F. O VO2-net foi respectivamente 27.3% e 9.94% superior adoptando o ritmo 1:1F do que os ritmos de 0:0 e de 1:2F. O ritmo que exigiu um menor Etot foi o de 0:0, com menos 19.24% do que o 1:1F e menos 9.44% do que o 1:2F. O CE foi substancialmente superior usando o ritmo de 1:1F do que o ritmo de 0:0, com uma variação média de 23.8%. O VV foi superior usando o 1:1F do que o 1:2F ou o 0:0 em respectivamente, 14.57% e 3.19%. Em conclusão, a adopção de diferentes ritmos respiratórios induzirá alterações na resposta bioenergética ao nadar a técnica de Mariposa. Contudo, sugere-se um estudo com uma amostra mais alargada, procurando aferir se as tendências manifestadas no presente estudo revelam robustez do ponto de vista estatístico. Mesmo assim, parece que a diminuição do número de actos inspiratórios promove uma redução dramática do Etot e do CE. Logo, em contextos competitivos, os mariposistas terão algumas vantagens em reduzir, tanto quant

Estudo da relação entre o custo energético e a mecânica gestual mariposa

Introdução e objectivos: Foi objectivo do presente estudo identificar a relação entre variáveis bioenergéticas (gasto energético e custo energético) e biomecânicas (parâmetros do ciclo gestual) ao longo de um leque de velocidades na técnica de Mariposa. Material e métodos: Três nadadores e uma nadadora de nível internacional foram submetidos a um protocolo incremental de 200m a Mariposa. A velocidade inicial foi de 1.18 m.s-1 para os nadadores e de 1.03 m.s-1 para a nadadora. A cada 200m a velocidade apresentava um incremento de 0.05.s-1 até o nadador atingir a exaustão. Avaliaram-se as trocas gasosas e os parâmetros cardiorespiratórios através de um oxímetro breathby- breath (K4 b2, Cosmed, Itália). Uma válvula de baixa resistência hidrodinâmica encontrava-se ligada ao oxímetro, permitindo a recolha das amostras de gases a analisar (Toussaint et al., 1987; Keskinen et al. 2003). Foram colhidas amostras de sangue capilar da orelha antes, imediatamente após cada 200m e 1, 3, 5 e 7 minutos depois do fim do protocolo, para a avaliação da concentração sérica de lactato (YSI 1500L, Yellow Springs, EUA). Foi calculado o dispêndio energético total (Etot), o custo energético (CE), a frequência gestual (FG), a distância de ciclo (DC), a velocidade média de deslocamento (V) e o índice de braçada (IB) para cada percurso, e calculado o valor médio para cada patamar de 200m. Foram calculadas rectas de regressão individuais, assim como os respectivos coeficientes de determinação e de correlação entre as variáveis bioenergéticas e as variáveis biomecânicas em estudo (p£ 0.05). Principais resultados e conclusões: Os coeficientes de correlação entre o Etot e a V, entre o CE e a FG e entre o CE e o IB apresentaram significado estatístico em todos os nadadores. Da relação entre o CE e a DC, apenas uma equação de regressão apresentou o coeficiente de correlação com significado estatístico. A relação entre a FG e a V, bem como, a relação entre o IB e a V foram significativas em todos os nadadores. Apenas duas equações de regressão apresentaram coeficientes de correlação significativos entre a V e a DC. Em conclusão, a amostra apresentou uma elevada variação inter-individual na relação entre as variáveis bioenergéticas e as variáveis biomecânicas em estudo, a Mariposa. Assim, sugere-se a análise individual da relação entre a V, a FG e a DC, com o intuito de identificar o ponto de deflexão da DC em função da V. Desta forma, será possível determinar as intensidades de treino adequadas com o objectivo de melhorar o custo energético específico de transporte

Energy cost and intracyclic variation of the velocity of the centre of mass in butterfly stroke

The purpose of this study was to examine the relationship between the intra-cycle variation of the horizontal velocity of displacement (dV) and the energy cost (EC) in butterfly stroke. Five Portuguese national level swimmers performed one maximal and two submaximal 200-m butterfly swims. The oxygen consumption was measured breath-by-breath by portable metabolic cart. A respiratory snorkel and valve system with low hydrodynamic resistance was used to measure pulmonary ventilation and to collect breathing air samples. Blood samples from the ear lobe were collected before and after each swim to analyse blood lactate concentration. Total energy expenditure (Etot) and EC were calculated for each swim. The swims were videotaped in the sagittal plane with a set of two cameras providing dual projection from both underwater and above the water surface. The APAS system was used to analyse dV for the centre of mass. The Etot increased linearly with the increasing V, presenting a significant correlation coefficient between these parameters (r=0.827, P<0.001). The increase in EC was significantly associated with the increase in the dV (r=0.807, P<0.001). All data were presented as the mean value and the standard deviation. It is concluded that high intra-cycle variation of the velocity of the centre of mass was related to less efficient swimming and vice versa for the butterfly stroke

Leibnizian, Galilean and Newtonian structures of spacetime

The following three geometrical structures on a manifold are studied in detail: (1) Leibnizian: a non-vanishing 1-form $\Omega$ plus a Riemannian metric \h on its annhilator vector bundle. In particular, the possible dimensions of the automorphism group of a Leibnizian G-structure are characterized. (2) Galilean: Leibnizian structure endowed with an affine connection $\nabla$ (gauge field) which parallelizes $\Omega$ and \h. Fixed any vector field of observers Z ($\Omega (Z) = 1$), an explicit Koszul--type formula which reconstruct bijectively all the possible $\nabla$'s from the gravitational ${\cal G} = \nabla_Z Z$ and vorticity $\omega = rot Z/2$ fields (plus eventually the torsion) is provided. (3) Newtonian: Galilean structure with \h flat and a field of observers Z which is inertial (its flow preserves the Leibnizian structure and $\omega = 0$). Classical concepts in Newtonian theory are revisited and discussed.Comment: Minor errata corrected, to appear in J. Math. Phys.; 22 pages including a table, Late

Speed fluctuation as a determinant factor of energy cost in Butterfly stroke

The purpose of this study was to examine the relationships between the speed fluctuation of the centre of mass and the EC, in butterfly stroke. Five national level Portuguese swimmers performed one maximal and two sub-maximal (85% and 75%) 200-m butterfly swims in a 25-m swimming pool. Cardio-pulmonary and gas exchange parameters were measured breath by breath for each swim to analyze VO2 and other energetic parameters by portable metabolic cart (K4b2, Cosmed, Rome, Italy). A respiratory snorkel and valve system with low hydrodynamic resistance was used to measure pulmonary ventilation and to collect breathing air samples. Blood samples from the ear lobe were collected before and after each swim to analyze blood lactate concentration (YSI 1500L, Yellow Springs, US). Total energy expenditure (È-tot) and EC were calculated for each swim. The swims were videotaped (50 Hz) in sagital plane with a set of two cameras providing dual-media images from both underwater and above the water surface. The cameras were real time synchronised and the images were edited on a mixing table to create one single image of dual-media. APAS system (Ariel Dynamics Inc, USA) was used to analyse speed fluctuation for the centre of mass. Coefficients of variation for the horizontal velocity of the centre of mass along the stroke cycle (dV) were calculated. Linear regressions between the bioenergetic and biomechanical variables were computed, as well as, its 0.05). Coefficients of determination and correlation (p). There was a significant and linear relationship between È-tot and velocity (r=0.827, p=0.0005). Statistically significant correlation coefficient between the EC and the dV (r=0.807, p=0.0009) was found, the coefficient of determination being r2=0.651. This means that the increase in the EC being strongly associated with the increase in the speed fluctuation. The individual coefficients of correlation and determination between the EC and the dV were very high (mean r2 0.018, ranging from 0.973 to 1.000). The mean of individual correlation È= 0.986 0.009 coefficients was higher than the overall correlation coefficient (r=0.993 vs r=0.807) of the pooled data. It is concluded that the speed fluctuation of the centre of mass was related to less efficient swimming and vice versa in butterfly. We suggest that the swimmers should strive to improve their technique performances by avoiding large variations in the speed fluctuation.info:eu-repo/semantics/publishedVersio

Assessment of time limit at lowest speed corresponding to maximal oxygen consumption in the four competitive swimming strokes

Time limit at lowest speed of maximal oxygen consumption (TLim-v O2max) was characterized in the 4 swimming strokes, and related with O2max and anaerobic threshold (AnT). 23 elite swimmers performed an incremental protocol for v O2max assessment. 48 hours later, Tlim-v O2max was assessed. O2 was directly measured BxB (K4 b2, Cosmed, Italy) and AnT was assessed individually (YSI 1500L Sport, USA). Tlim-v O2max values were 238.8±39.0, 246.1±51.9, 277.6±85.6 and 331.4±82.7 s in crawl, backstroke, butterfly, and breaststroke (no differences observed). No correlations were found between Tlim-v O2max and O2max, and AnT. However, inverse relationships were observed between Tlim-v O2max and v O2max (r=-0.63, p<0.01) and vAnT (r=-0.52, p=0.01), pointing out that the higher the velocities commonly related to aerobic proficiency, the lower the TLim- v O2max

Time limit at the minimum velocity of VO2max and intracyclic variation of the velocity of the centre of mass

The purpose of this study was to analyse the relationship between time limit at the minimum velocity that elicits maximal oxygen consumption (TLim-vVO2max) and intra-cyclic variations of the velocity of the centre of mass (dv) in the four competitive swimming techniques. Twelve elite male swimmers SWIMMING BIOENERGETICS Rev Port Cien Desp 190 6(Supl.2) 185–197 swam their own best technique until exhaustion at their previously determined v O2max to assess TLim-v O2max. The test was videotaped in the sagittal plan and the APAS software was used to evaluate the horizontal velocity of the centre of mass (Vcm) and its intra-cyclic variation (dv) per swimming technique. Results pointed out that the strokes that presented higher intra-cyclic variations also presented larger values of TLim. Intra-cyclic speed fluctuations (dv) decreased during the TLim test in the four strokes studied, probably due to fatigue. Key words: VO2, intra-cyclic velocity variations, time limit, centre of mass.Authors want to express their gratitude to the Portuguese National Team, and the Portuguese Swimming Federation, for their cooperation

Relationships between energy cost, swimming velocity and speed fluctuation in elite butterfliers

In swimming science, economy of movement is an interesting field of research. Several investigations have been conducted to understand the role of bioenergetical profile to performance. Most of those studies focused exclusively on the contribution of The individual correlations between E-tot and v ranged from R=0.95 aerobic system to produce energy for movement, even though all competitive swimming events also require significant (p=0.05) to R=0.90 (p&lt;0.01). For pooled data the relationship was contribution from anaerobic energetic system to cover total energy expenditure. R=0.70 (p&lt;0.01). The individual correlations between EC and d

Mode resolved density of atmospheric aerosol particles

In this study, we investigate the mode resolved density of ultrafine atmospheric particles measured in boreal forest environment. The method used here enables us to find the distinct density information for each mode in atmospheric fine particle population: the density values for nucleation, Aitken, and accumulation mode particles are presented. The experimental data was gained during 2 May 2005–19 May 2005 at the boreal forest measurement station &quot;SMEAR II&quot; in Hyytiälä, Southern Finland. The density values for accumulation mode varied from 1.1 to 2 g/cm&lt;sup&gt;3&lt;/sup&gt; (average 1.5 g/cm&lt;sup&gt;3&lt;/sup&gt;) and for Aitken mode from 0.4 to 2 g/cm&lt;sup&gt;3&lt;/sup&gt; (average 0.97 g/cm&lt;sup&gt;3&lt;/sup&gt;). As an overall trend during the two weeks campaign, the density value of Aitken mode was seen to gradually increase. With the present method, the time dependent behaviour of the particle density can be investigated in the time scale of 10 min. This allows us to follow the density evolution of the nucleation mode particles during the particle growth process following the nucleation burst. The density of nucleation mode particles decreased during the growth process. The density values for 15 nm particles were 1.2–1.5 g/cm&lt;sup&gt;3&lt;/sup&gt; and for grown 30 nm particles 0.5–1 g/cm&lt;sup&gt;3&lt;/sup&gt;. These values are consistent with the present knowledge that the condensing species are semi-volatile organics, emitted from the boreal forest