269 research outputs found
Swimming bioenergetics: integrating biomechanical and physiological data into a coherent biophysical model for performance and training
The purpose of the present paper is to synthesise a number of scientific contributions of our research group, into a coherent corpus of knowledge related to swimming biophysics, specially centred on the availability and use of energy in swimming. After an introductory part that intends to underline the relevance of this approach base on the conceptualization of the swimmer, and swimming action itself, as a thermodynamic system and its mechanical output, we will survey a number of studies and respective contributions for a more advanced understanding of swimming performance, that can be transferred into training and enhancement of swimmers’ working capacity.
Most of the studies referred were conducted over samples of swimmers of both genders and of different types, from university/participative swimmers to Portuguese elite swimmers, crossing the large population of trained national level swimmers. Those swimmers were studied in the four different competitive swimming strokes, accomplishing progressive protocols based over distances of 200 m. Physiologic parameters like VO2 (and associated ventilatory and respiratory parameters), post exercise capillary blood [La-] peaks, and heart rate, were directly measured. Kinematical parameters were also measured in the different studies, ranging from simple semi-quantitative parameters, like stroke length (SL), and stroke frequency (SF), to more elaborated biomechanical data, like intracyclic speed fluctuations and propulsive segments kinematics.
The focus of interest ranged from swimming economy of different strokes and genders (and of different technical alternatives of the same stroke), to the effects over energy cost of intracyclic speed fluctuations. Energetic input determinant factors, like swimming VO2 kinetics, including VO2 slow component, and VO2 time limit, and its determinants, will also be analysed
The influence of stroke mechanics into energy cost of elite swimmers
The purpose of this study was to analyze the
relationships between energy cost (C), swimming velocity
(v), stroke frequency (SF) and stroke length (SL) in toplevel
swimmers. Eighteen elite swimmers (four freestylers,
five backstrokers, five breaststrokers and four butterflyers)
performed an intermittent set of n 9 200 m swims (n B 8)
with increasing velocity. The oxygen consumption was
measured breath-by-breath by a portable metabolic cart
(K4 b2, Cosmed, Rome, Italy). A respiratory snorkel and
valve system with low hydrodynamic resistance was used
to measure pulmonary ventilation and collect expiratory
gases. Blood samples were taken from the ear lobe before
and after each swim to analyze the blood lactate concentration
(YSI 1500L, Yellow Springs, OH, USA). At
Backstroke, Breaststroke and Butterfly strokes, increases of
SF were associated to increases of C, even when controlling
the v. The increases in SL only promoted significant
decreases in the C in Breaststroke. There was a significant
and polynomial relationship between v and SF for all
competitive swimming techniques. The polynomial relationship
between v and SL was significant only in Freestyle
and Butterfly stroke. Partial correlations between v and SF
controlling the effect of SL and between v and SL controlling
the effect of SF, were positive and significant for
all techniques. It is concluded that manipulation of stroke
mechanics variables (SF and SL) may be one of the factors
through which C in competitive swimming can be altered
for a given v
Performance of a Large Area Avalanche Photodiode in a Liquid Xenon Ionization and Scintillation Chamber
Scintillation light produced in liquid xenon (LXe) by alpha particles,
electrons and gamma-rays was detected with a large area avalanche photodiode
(LAAPD) immersed in the liquid. The alpha scintillation yield was measured as a
function of applied electric field. We estimate the quantum efficiency of the
LAAPD to be 45%. The best energy resolution from the light measurement at zero
electric field is 7.5%(sigma) for 976 keV internal conversion electrons from
Bi-207 and 2.6%(sigma) for 5.5 MeV alpha particles from Am-241. The detector
used for these measurements was also operated as a gridded ionization chamber
to measure the charge yield. We confirm that using a LAAPD in LXe does not
introduce impurities which inhibit the drifting of free electrons.Comment: 13 pages, 8 figure
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
Characterization, Classification And Analysis Of The Main Properties Of The Southwestern Goias Soil
Characterization of the soil and the grouping of its properties through main component analysis can assist in the classification and observation of the consequences of the conversion of native forest areas in pastures. Such data can aid in management practices. Considering the lack of studies in Cerrado soils of south-western Goias, developed metagranites of Jurubatuba suite, the objective was to classify and study the physical, chemical and mineralogical soil (under native forest and pasture) Southwest of Goias. Soil sampling and classification followed the Field Methods Manual and the Brazilian System of Soil Classification, respectively. The physical, chemical and mineralogical soil were studied, as well as main component analysis made for these attributes. The profile 1 under native forest was classified as "Cambissolo Háplico Tb eutrófico latossólico". The profile 2 under degraded pasture was rated "Latossolo Amarelo eutrófico típico". In addition, the profile 3 under rotated pasture was rated as "Latossolo Vermelho eutrófico chernossólico". It was observed that the "Latossolos" have higher bulk density and soil penetration resistance, indicating greater soil compaction. They showed high amounts of iron oxides and minor amount of nutrients such as calcium and magnesium. The principal component analysis allowed the grouping of profiles into two groups. Group 1 brought together the properties related to "Latossolos", and the second was related to "Cambissolo" properties. Thus, the principal components analysis aids the understanding of soil properties and the grouping of soils with similar characteristics, the level of order and management.3731135115
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
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
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
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