399 research outputs found
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 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 (gauge field) which parallelizes and \h. Fixed
any vector field of observers Z (), an explicit Koszul--type
formula which reconstruct bijectively all the possible 's from the
gravitational and vorticity 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 ). 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<0.01). For pooled data the relationship was contribution from anaerobic energetic system to cover total energy expenditure. R=0.70 (p<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 "SMEAR II" in Hyytiälä, Southern Finland. The density values for accumulation mode varied from 1.1 to 2 g/cm<sup>3</sup> (average 1.5 g/cm<sup>3</sup>) and for Aitken mode from 0.4 to 2 g/cm<sup>3</sup> (average 0.97 g/cm<sup>3</sup>). 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<sup>3</sup> and for grown 30 nm particles 0.5–1 g/cm<sup>3</sup>. These values are consistent with the present knowledge that the condensing species are semi-volatile organics, emitted from the boreal forest
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