Efeito da colhedora, velocidade e ponto de coleta na contaminação de sementes de soja por fungos

A pesquisa foi realizada com o objetivo de avaliar a qualidade sanitária de sementes de soja cv. Coodetec 217, colhidas por duas colhedoras operando em velocidades e pontos de coleta distintos. O delineamento foi inteiramente casualizado, no esquema fatorial 2x2x2. Os tratamentos foram constituídos por duas máquinas Massey Ferguson (MF 2003 e MF 2004), duas velocidades (4 e 7 Km.h¹) e dois pontos de coleta (tanque graneleiro e saída do tubo de descarga). A sanidade foi avaliada pelo método do papel de filtro, com quatro repetições de 50 sementes. Houve interação significativa para os fatores colhedora e ponto de coleta para a incidência de Penicillium sp. e Fusarium sp., entre colhedora e velocidade para Aspergillus spp., e, entre velocidade e ponto de coleta para Penicillium sp.. A presença de fungos associados às sementes, principalmente, Cladosporium sp. e Fusarium sp., independe do tipo de colhedora. Uma menor contaminação fúngica é observada nas sementes coletadas na saída do tubo de descarga à 4 Km.h-1. Para Fusarium sp., Aspergillus spp., e Penicillium sp. existe uma dependência dos fatores sobre suas incidências nas sementes da cultivar analisada, sob as condições estudadas.

Correlação entre tempo, erro, velocidade e compreensão de leitura em escolares com distúrbio de aprendizagem

OBJETIVO: Correlacionar as variáveis: erros, tempo, velocidade e compreensão de leitura de escolares com distúrbios de aprendizagem e escolares sem dificuldade de aprendizagem. MÉTODOS: Participaram deste estudo 40 escolares de 8 a 12 anos de idade, de ambos os gêneros, de 2ª a 4ª série do Ensino Fundamental Municipal, divididos em GI: composto por 20 escolares sem dificuldade de aprendizagem e GII: composto por 20 escolares com distúrbio de aprendizagem. Foram utilizados textos selecionados a partir da indicação de professores da 2ª à 4ª série da Rede Municipal de Ensino, para a realização de leitura oral. A compreensão foi realizada por meio de quatro perguntas apresentadas após a leitura do texto, às quais os escolares deveriam responder oralmente. RESULTADOS: Houve diferença entre GI e GII no número de erros, velocidade e compreensão de leitura e tempo total de leitura. A correlação entre tempo total de leitura e erros cometidos durante a leitura foi positiva, e entre as variáveis tempo total de leitura e velocidade de leitura foi negativa. Para o grupo GII, houve diferença com correlação negativa entre as variáveis tempo total de leitura e velocidade de leitura. CONCLUSÃO: Para os escolares com distúrbio de aprendizagem, o desempenho nas variáveis que foram correlacionadas encontra-se alterado interferindo no desenvolvimento em leitura e, consequentemente, na compreensão do texto lido.

Arquitetura com elevada taxa de processamento e reduzida largura de banda de memória para a estimação de movimento em vídeos digitais

Nowadays several electronics devices support digital videos. Some examples of these devices are cellphones, digital cameras, video cameras and digital televisions. However, raw videos present a huge amount of data, millions of bits, for their representation as the way they were captured. To store them in its primary form it would be necessary a huge amount of disk space and a huge bandwidth to allow the transmission of these data. The video compression becomes essential to make possible information storage and transmission. Motion Estimation is a technique used in the video coder that explores the temporal redundancy present in video sequences to reduce the amount of data necessary to represent the information. This work presents a hardware architecture of a motion estimation module for high resolution videos according to H.264/AVC standard. The H.264/AVC is the most advanced video coder standard, with several new features which allow it to achieve high compression rates. The architecture presented in this work was developed to provide a high data reuse. The data reuse schema adopted reduces the bandwidth required to execute motion estimation. The motion estimation is the task responsible for the largest share of the gains obtained with the H.264/AVC standard so this module is essential for final video coder performance. This work is included in Rede H.264 project which aims to develop Brazilian technology for Brazilian System of Digital Television

Mechanical comparative analysis of three different types of sutures in different dimensions tendons: experimental study

O objetivo da presente investigação experimental foi avaliar o perfil mecânico de três tipos de técnicas de sutura entre tendões de dimensões diferentes. Foram utilizados 21 cães sem raça definida (11machos/10 fêmeas), dos quais foram obtidos os tendões flexor comum dos dedos - t.c. (maior dimensão) e tibial cranial - t.cr. (menor dimensão), de ambos os membros pélvicos. Logo após a obtenção das peças foi realizada sutura, segundo cada tipo de técnica, porém sempre com o mesmo número de pontos. Os tendões utilizados para sutura foram sempre do lado direito e o controle do lado esquerdo (t.cr.). Após a sutura, os corpos de prova foram fixados em garras especialmente desenvolvidas e submetidos a ensaio de tração axial à velocidade de 30mm/minuto. Após o ensaio o programa da máquina forneceu os valores da carga máxima ( na ruptura) e deformação absoluta (mm) e relativa (%), além do diagrama carga-deformação. Os resultados foram submetidos a estudo estatístico pela análise de medidas repetidas no nível de 5% de significância. Não foi constatada diferença estatisticamente significativa nos parâmetros mecânicos avaliados nos três grupos de técnicas de suturas. em relação ao controle (tendão de menos diâmetro contra-lateral), observou-se que a sutura apresenta resistência máxima a tração significativamente menor que o controle e maior deformação.

A história do intemperismo na Província Borborema Oriental, Nordeste do Brasil: implicações paleoclimáticas e tectônicas

Until some years ago, weathering geochronology was primarily based on the K-Ar and 40Ar/39Ar dating of supergene minerals. Recent advances in the analysis of supergene goethite by the (U-Th)/He method expanded the number of suitable minerals for such purpose, as well as the time of application for weathering geochronology. This study represents the first systematic approach in Brazil, combining both the 40Ar/39Ar e (U-Th)/He methodologies to improve the knowledge on the weathering and the age of nonfossiliferous sediments. Supported by geologic and geomorphologic correlations, we identified different types of weathering profiles occurring in the interior and coastal areas of northeastern Brazil. These profiles were correlated to main regional geomorphological domains: the Borborema Plateau , the Sertaneja Depression , and the Coastal Cuestas and Plains, and respective planation surfaces, which study is fundamental to understand the landscape evolution of the northern portion of the eastern Borborema Province. The depth and stratigraphic organization of the weathering profiles in each of the geomorphological domains permitted to establish that: (i) the profiles on the highlands that cap the Borborema Surface are deeper (up to 100 m) and can be considered as typical lateritic profiles; (ii) on the lowlands that form the Sertaneja Surface , the weathering profiles are shallow and poorly developed (2-5 m deep); (iii) the profiles along the coastal area are moderately developed (up to 25 m deep), and are characterized by thick saprolites and mottle zones. Aiming to establish the timing of the evolution of northeastern Brazil, we studied 29 weathering profiles representing distinct topographic levels of the Borborema Province, from the highlands to the coast, through the analysis of 248 grains of supergene manganese oxides using laser step-heating 40Ar/39Ar geochronology. Additionally, we applied the (U-Th)/He method in 20 weathering profiles, by dating 171 grains of supergene iron oxides and hydroxides. Geochronological results for 248 grains of manganese oxides analyzed by the 40Ar/39Ar method indicate that the weathering profiles in the study area record the history of weathering from the Oligocene to the Pleistocene, with ages in the order of 31.4 ± 1.0 Ma to 0.8 ± 0.4 Ma. Dating of 171 grains of goethite by the (U-Th)/He method yielded ages ranging from 43.2 ± 4.3 Ma to 0.8 ± 0.1 Ma, suggesting the weathering processes last from the Eocene to the Pleistocene. The precipitation of supergene goethite in this interval confirms the age of the weathering processes identified from the manganese oxides record. 105 goethite grains from 8 different occurrences of the Barreiras Formation were dated by the (U-Th)/He method. Five grains collected from the cement in the Barreiras Formation sandstones, in the Lagoa Salgada and Rio do Fogo coastal cuestas, yielded ages of 17.6 ± 1.8 Ma, 17.3 ± 1.7 Ma, 16.3 ± 1.6 Ma, 16.2 ± 1.6 Ma and 13.6 ± 1.4 Ma. Results of 69 goethite grains from authigenic pisoliths collected in 7 different localities also yielded concordant ages, varying from 17.8 ± 1.8 to 7.5 ± 0.8 Ma. Results obtained from 31 detrital grains are concordant in 3 distinct localities (Lagoa Salgada, Praia da Garças e Ponta Grossa); they vary in the range of 43.2 ± 4.3 to 21.6 ± 2.2 Ma, and indicate that the maximum age for the Barreiras Formation deposition is around 22 Ma. 40Ar/39Ar results for 15 manganese oxides grains associated with the Barreiras Formation weathering profiles, in 3 different localities, vary from 13.1 ± 0.9 to 7.7 ± 0.4 Ma, in the same range of ages obtained by the (U-Th)/He method. The systematic application of the 40Ar/39Ar and (U-Th)/He methods, respectively for manganese oxides and goethites, show that the Barreiras Formation sediments were already deposited since ca. 17 Ma, and that the weathering processes were active until ca. 7 Ma ago. The ages obtained from manganese oxides collected in the Cenozoic basalts (Macau Formation) also reveal a weathering history between 19 and 7 Ma, pointing to hot and humid conditions during most of the Miocene. 40Ar/39Ar ages yielded by manganese oxides associated with the Serra do Martins Formation vary from 14.1 ± 0.4 to 10.5 ± 0.3 Ma. On the other hand, (U-Th)/He ages from iron oxides/hydroxides collected in the Serra do Martins Formation mesas vary from 20.0 ± 2.0 to 5.5 ± 0.6 Ma, indicating that those sediments are older than 20 Ma. 40Ar/39Ar and (U-Th)/He results produced in this study are in agreement with paleoclimatic interpretations based on stable isotopes and clay index values measured in the Atlantic Ocean sediments, validating the use of weathering geochronology to investigate paleoclimatic variations. The direct dating of the Barreiras Formation permitted, for the first time, confident inferences on the age of the brittle deformation recorded by this sedimentary unit in the Rio Grande do Norte and Ceará states. The first event, syn-deposition, occurred during the early Miocene; an younger event, related to the post-depositional deformation of the Barreiras Formation, is associated with tectonic activity from the very early Miocene to the Holocene. In agreement with data from other areas, results obtained in this study reveal that the depth and complexity of the weathering profiles reflect the time of exposition of such areas to the weathering agents close to the surface. However, there is no clear relationship between ages vs. altitude. The depth and the stratigraphic organization of weathering profiles in northeastern Brazil, contrary to the southeastern Brazil pattern, do not vary toward the coast. In our study area, field observations reveal the presence of ancient, thick and complex lateritic profiles preserved in the sedimentary mesas on the Borborema Plateau, as younger, narrow and incipient ones occur in the dissected areas. Geochronological results obtained for these profiles yielded older ages on the high altitudes, and younger ages in the lowlands, suggesting the scarp retreatment is the most reliable model to explain the regional landscape evolution. However, in the coastal lowlands, the relatively older ages obtained indicate that more complexes processes were involved in the modeling of the local relief

Litoestratigrafia e deformação cenzóica na região de Icapuí, Ceará, e implicações para a estruturação de campos de petróleo na borda ocidental da bacia Potiguar(NE do Brasil)

This thesis deals with the sedimentological/stratigraphic and structural evolution of the sedimentary rocks that occur in the NW continental border of the Potiguar Basin. These rocks are well exposed along coastal cliffs between the localities of Lagoa do Mato and Icapuí, Ceará State (NE Brazil). The sedimentological/stratigraphic study involved, at the outcrop scale, detailed facies descriptions, profile mapping of the vertical succession of different beds, and columnar sections displaying inferred lateral relationships. The approach was complemented by granulometric and petrographic analyses, including the characterization of heavy mineral assemblages. The data set allowed to recognize two kinds of lithological units, a carbonate one of very restricted occurrence at the base of the cliffs, and three younger, distinct siliciclastic units, that predominate along the cliffs, in vertical and lateral extent. The carbonate rocks were correlated to the late Cretaceous Jandaíra Formation, which is covered by the siliciclastic Barreiras Formation. The Barreiras Formation occurs in two distinct structural settings, the usual one with nondeformed, subhorizontal strata, or as tilted beds, affected by strong deformation. Two lithofacies were recognized, vertically arranged or in fault contacts. The lower facies is characterized by silty-argillaceous sandstones with low-angle cross bedding; the upper facies comprises medium to coarse grained sandstones, with conglomeratic layers. The Tibau Formation (medium to coarse-grained sandstones with argillite intercalations) occurs at the NW side of the studied area, laterally interlayered with the Barreiras Formation. Eolic sediments correlated to the Potengi Formation overly the former units, either displaying an angular unconformity, or simply an erosional contact (stratigraphic unconformity). Outstanding structural features, identified in the Barreiras Formation, led to characterize a neocenozoic stress field, which generated faults and folds and/or reactivated older structures in the subjacent late cretaceous (to paleogene, in the offshore basin) section. The structures recognized in the Barreiras Formation comprise two distinct assemblages, namely a main extensional deformation between the localities of Ponta Grossa and Redonda, and a contractional style (succeeded by oblique extensional structures) at Vila Nova. In the first case, the structural assemblage is dominated by N-S (N±20°Az) steep to gently-dipping extensional faults, displaying a domino-style or listric geometry with associated roll-over structures. This deformation pattern is explained by an E-W/WNW extension, contemporaneous with deposition of the upper facies of the Barreiras Formation, during the time interval Miocene to Pleistocene. Strong rotation of blocks and faults generated low-angle distensional faults and, locally, subvertical bedding, allowing to estimate very high strain states, with extension estimates varying between 40% up to 200%. Numerous detachment zones, parallel to bedding, help to acommodate this intense deformation. The detachment surfaces and a large number of faults display mesoscopic features analoguous to the ones of ductile shear zones, with development of S-C fabrics, shear bands, sigmoidal clasts and others, pointing to a hydroplastic deformation regime in these cases. Local occurrences of the Jandaíra limestone are controled by extensional faults that exhume the pre-Barreiras section, including an earlier event with N-S extension. Finally, WNWtrending extensional shear zones and faults are compatible with the Holocene stress field along the present continental margin. In the Vila Nova region, close to Icapuí, gentle normal folds with fold hinges shallowly pluging to SSW affect the lower facies of the Barreiras Formation, displaying an incipient dissolution cleavage associated with an extension lineation at high rake (a S>L fabric). Deposition of the upper facies siliciclastics is controlled by pull-apart graben structures, bordered by N-NE-trending sinistral-normal shear zones and faults, characterizing an structural inversion. Microstructures are compatible with tectonic deformation of the sedimentary pile, burried at shallow depths. The observed features point to high pore fluid pressures during deformation of the sediments, producing hydroplastic structures through mechanisms of granular flow. Such structures are overprinted by microfractures and microfaults (an essentially brittle regime), tracking the change to microfracturing and frictional shear mechanisms accompanying progressive dewatering and sediment lithification. Correlation of the structures observed at the surface with those present at depth was tested through geophysical data (Ground Penetrating Radar, seismics and a magnetic map). EW and NE-trending lineaments are observed in the magnetic map. The seismic sections display several examples of positive flower structures which affect the base of the cretaceous sediments; at higher stratigraphic levels, normal components/slips are compatible with the negative structural inversion characterized at the surface. Such correlations assisted in proposing a structural model compatible with the regional tectonic framework. The strong neogenepleistocene deformation is necessarily propagated in the subsurface, affecting the late cretaceous section (Açu and Jandaíra formations), wich host the hydrocarbon reservoirs in this portion of the Potiguar Basin. The proposed structural model is related to the dextral transcurrent/transform deformation along the Equatorial Margin, associated with transpressive terminations of E-W fault zones, or at their intersections with NE-trending lineaments, such as the Ponta Grossa-Fazenda Belém one (the LPGFB, itself controlled by a Brasiliano-age strike-slip shear zone). In a first step (and possibly during the late Cretaceous to Paleogene), this lineament was activated under a sinistral transpressional regime (antithetic to the main dextral deformation in the E-W zones), giving way to the folds in the lower facies of the Barreiras Formation, as well as the positive flower structures mapped through the seismic sections, at depth. This stage was succeeded (or was penecontemporaneous) by the extensional structures related to a (also sinistral) transtensional movement stage, associated to volcanism (Macau, Messejana) and thermal doming processes during the Neogene-Pleistocene time interval. This structural model has direct implications to hydrocarbon exploration and exploitation activities at this sector of the Potiguar Basin and its offshore continuation. The structure of the reservoirs at depth (Açu Formation sandstones of the post-rift section) may be controlled (or at least, strongly influenced) by the deformation geometry and kinematics characterized at the surface. In addition, the deformation event recognized in the Barreiras Formation has an age close to the one postulated for the oil maturation and migration in the basin, between the Oligocene to the Miocene. In this way, the described structural cenario represents a valid model to understand the conditions of hydrocarbon transport and acummulation through space openings, trap formation and destruction. This model is potentially applicable to the NW region of the Potiguar Basin and other sectors with a similar structural setting, along the brazilian Equatorial Atlantic Margin

Análise da deformação pós-Rifte na Bacia do Araripe, Nordeste do Brasil

The Araripe Basin is located over Precambrian terrains of the Borborema Province, being part of Northeast Brazil inner basins. Its origin is related to the fragmentation of the Gondwana supercontinent and consequently opening of South Atlantic during early Cretaceous. The basin has a sedimentary infill encompassing four distinct evolution stages, comprising Paleozoic syneclisis, pre-rift, rift and post-rift. The target of this study comprises the post-rift section of the basin focusing deformational styles which affect evaporates from Ipubi Member of the Santana Formation, which is composed by gypsum and anidrite layers interbedded with shales. These units occur widespread across the basin. In the central part of the basin, near Nova Olinda-Santana do Cariri, evaporites are affected by an essentialy brittle deformation tipified by fibrous gypsum filled fractures, cutting massive layers of gypsum and anidrite. Veins with variable orientations and dips are observed in the region distributed over three main populations: i) a dominant NWSE with shallow to moderate NE dipping population, consisting of gypsum filled veins in which fibers are normal to vein walls; i) NE-SW veins with moderate SE dips containing subhorizontal growth fibers; and iii) N-S veins with shallow E-W dips with fibers oblique to vein walls. In the west portion of the basin, near Trindade-Ipubi-Araripina towns, evaporate layers are dominantly constituted by gypsum/anidrite finely stratified, showing a minor density of veins. These layers are affected by a unique style of deformation, more ductile, typified by gentle to open horizontal normal folding with several tens of meters length and with double plunging NW-SE or NE-SW hinges, configuring domic features. In detail, gypsum/anidrite laminae are affected by metre to decimeter scale close to tight folding, usually kinked, with broken hinges, locally turning into box folds. Veins show NE-SW main directions with shallow NE dips, growth fibers are parallel to vein walls, constituting slickenfibers. This region is marked by faults that affect Araripina Formation with NW-SE, NE-SW and E-W directions. The main structural styles and general orientations of structures which affected the post-rift section of Araripe Basin yielded important kinematic information analysis which led us to infer a E-W to NE-SW extension direction to the northeastern part of the Basin, whereas in the southeastern part, extension occurred in N-S direction. Thus, it was possible to determine a regional kinematic setting, through this analysis, characterizing a NE-SW to ENE-WSW system for the post-rift section, which is compatible with the tension settings for the Sout American Plate since Albian. Local variations at the fluid pressure linked (or not) to sedimentary overload variation define local tension settings. This way, at the northeastern portion of the basin, the post-rift deformation was governed by a setting which σ 1 is sub-horizontal trending NE-SW and, σ 3 is sub-vertical, emphasizing a reverse fault situation. At the southwestern portion however there was characterized a strike slip fault setting, featuring σ 1 trending ENEWSW and σ3 trending NNW-SSE

Análise estrutural da deformação cenozóica na Bacia de Cumuruxatiba (BA)

The Cumuruxatiba basin is located at the southern coast State of Bahia in northeastern of Brazil. This basin was formed in distensional context, with rifting and subsequent thermal phase during Neocomian to late Cretaceous. At Cenozoic ages, the Abrolhos magmatism occurs in the basin with peaks during the Paleocene and Eocene. In this period, there was a kinematic inversion in the basin represented by folds related to reverse faults. Structural restoration of regional 2D seismic sections revealed that most of the deformation was concentrated at the beginning of the Cenozoic time with the peak at the Lower Eocene. The post-Eocene is marked by a decrease of strain rate to the present. The 3D structural modeling revealed a fold belt (trending EW to NE-SW) accommodating the deformation between the Royal Charlotte and Sulphur Minerva volcanic highs. The volcanic eruptions have caused a differential overburden on the borders of the basin. This acted as the trigger for halokinesis, as demonstrated by physical modeling in literature. Consequently, the deformation tends to be higher in the edges of the basin. The volcanic rocks occur mainly as concordant structures (sills) in the syn-tectonic sediment deposition showing a concomitant deformation. The isopach maps and diagrams of axis orientation of deformation revealed that most of the folds were activated and reactivated at different times during the Cenozoic. The folds exhibit diverse kinematic patterns over time as response to behavior of adjacent volcanic highs. These interpretations allied with information on the petroleum system of the basin are important in mapping the prospects for hydrocarbons

Caracterização multi-escalar de bandas de deformação nas tectonossequências paleozóica, pré- e sin-rifte da Bacia do Araripe, Nordeste do Brasil

Deformation bands are structures, developed in porous sandstones, that has small offsets and they are not shown on seismic section. The deformation bands of the pre and synrift sandstones of Araripe Basin were studied in outcrop, macroscopic and microscopic scales. The hierarchical, cinematic and spatial-geometric characteristics, and also the deformational mechanisms acting during its structural evolution were established too. In general, the mesoscopic scale observation allowed to discriminate deformation bands as singles or clusters in three main sets: NNE-SSW dextral; NE-SW normal (sometimes with strike-slip offset); and E-W sinistral; further a bed-parallel deformation bands as a local set. The microscopic characterization allowed to recognize the shearing and cataclastic character of such structures. Through the multi-scale study done in this work we verified that deformation bands analyzed were preferentially developed when sandstones under advanced stage of lithification. We also infer that the geometrical-spatial complexity of these bands, together with the presence of cataclastic matrix, can difficult the migration of fluids in reservoir rocks, resulting on their compartmentalization. Therefore, the study of deformation bands can aid researches about the structural evolution of sedimentary basin, as well as collaborate to understand the hydrodynamic behavior of reservoirs compartmented by these deformational structures

A variedade da dieta é fator protetor para a pressão arterial sistólica elevada

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Alterações do pH, da P O2 e da P CO2 arteriais e da concentração de lactato sangüíneo de cavalos da raça Árabe durante exercício em esteira de alta velocidade

Avaliaram-se as alterações do pH, da P O2 e da P CO2 do sangue arterial e da concentração de lactato sangüíneo de 11 cavalos adultos da raça Árabe, submetidos a exercício progressivo em esteira de alta velocidade. Antes do exercício, no intervalo dos 15 segundos finais de cada mudança de velocidade e aos 1, 3 e 5 minutos após o término do exercício foram coletadas amostras de sangue arterial e venoso para a mensuração dos gases sangüíneos e da concentração de lactato. O exercício resultou em diminuição do pH, da pressão parcial de O2 (P O2) e da pressão parcial de CO2 (P CO2). A concentração de lactato sangüíneo elevou-se exponencialmente a partir da velocidade de 8,0m/s até os momentos após término do exercício.

Comportamento mecânico de tendões calcâneo bovino sob informações clínicas

Este trabalho teve por finalidade analisar o comportamento de tendões calcâneo bovino submetidos a ensaios mecânicos cíclicos. Para cada corpo de prova foram aplicados três ensaios de dez ciclos de tração e três níveis de deformação: 2,5%, 3% e 4%. Ao término de cada ensaio o tendão era mantido em repouso por 300 s. A velocidade de carregamento adotada foi de 10% do comprimento do corpo de prova, por segundo. Os resultados obtidos foram submetidos à análise de variância com delineamento de parcelas subdivididas no tempo e blocos casualizados nas subparcelas. Conclui-se que o pré-tensionamento de tendões realizado através da deformação relativa permanece como parâmetro mais seguro, por atuar dentro dos limites fisiológicos do tendão, evitando os efeitos nocivos do sobretensionamento.

VO2máx estimado e sua velocidade correspondente predizem o desempenho de corredores amadores

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Limiar anaeróbio e velocidade crítica determinada com diferentes distâncias em nadadores de 10 a 15 anos: relações com a performance e a resposta do lactato sanguíneo em testes de endurance

O objetivo deste estudo foi comparar a velocidade crítica (VC) determinada através de diferentes distâncias com o limiar anaeróbio (LAn) e as velocidades máximas mantidas em testes de 20 (V20) e 30 (V30) minutos na natação, verificando se a idade cronológica em jovens nadadores interfere nessas relações. Participaram do estudo 31 nadadores (17 meninas e 14 meninos) divididos segundo a idade cronológica em dois grupos: 10 a 12 anos e 13 a 15 anos. O LAn foi determinado como sendo a velocidade correspondente a 4mM de lactato sanguíneo. A VC1 (25/50/100m), VC2 (100/200/400m) e a VC3 (50/100/200m) foram calculadas através do coeficiente angular da reta de regressão linear entre as distâncias e seus respectivos tempos. As V20 e V30 foram determinadas através de três a seis repetições, com coletas de sangue no 10º minuto e ao final do tiro. Para o grupo de 10 a 12 anos, a VC1 (m/s) (0,98 ± 0,17) e o LAn (0,97 ± 0,12) não foram diferentes entre si, sendo maiores do que a VC2 (0,92 ± 0,16), VC3 (0,89 ± 0,18), V20 (0,92 ± 0,11) e V30 (0,90 ± 0,11). Para o grupo de 13 a 15 anos, a VC1 (m/s)(1,11 ± 0,11) foi maior do que o LAn (1,02 ± 0,07), V20 (0,99 ± 0,09), V30 (0,97 ± 0,09), VC2 (0,98 ± 0,11) e VC3 (1,00 ± 0,11). Pode-se concluir que a distância utilizada na determinação da VC interfere no valor obtido, independente da idade cronológica. A VC determinada com distâncias entre 50 e 400m pode ser utilizada na avaliação da capacidade aeróbia de crianças e adolescentes, substituindo os testes contínuos máximos com durações próximas a 20 ou 30 minutos.

Índices técnicos correspondentes à velocidade crítica e à máxima velocidade de 30 minutos em nadadores com diferentes níveis de performance aeróbia

O principal objetivo deste estudo foi verificar o efeito do nível de performance aeróbia na relação entre os índices técnicos correspondentes à velocidade crítica (VC) e à velocidade máxima de 30 minutos (V30) em nadadores. Participaram deste estudo, 23 nadadores do gênero masculino com características antropométricas similares, divididos segundo o nível de performance aeróbia em grupo G1 (maior performance) (n = 13) e G2 (menor performance) (n = 10). Os indivíduos tinham pelo menos quatro anos de experiência no esporte e treinavam um volume semanal de 30.000 a 45.000m. A VC foi determinada através do coeficiente angular da regressão linear entre as distâncias (200 e 400m) e seus respectivos tempos. A V30 foi determinada através da máxima distância realizada em um teste de 30 minutos. Todas as variáveis foram determinadas no nado crawl. A VC foi significantemente maior do que a V30 no grupo G1 (1,30 ± 0,04 vs. 1,23 ± 0,06m.s-1) e no G2 (1,17 ± 0,08 vs. 1,07 ± 0,06m.s-1). As duas variáveis foram maiores no grupo G1. As taxas de braçada correspondentes à VC (TBVC) e à V30 (TBV30) obtidas nos grupos G1 (33,07 ± 4,34 vs. 31,38 ± 4,15 ciclos.min-1) e G2 (35,57 ± 6,52 vs. 33,54 ± 5,89 ciclos.min-1) foram similares entre si. A TBVC foi significantemente menor no grupo 1 do que no grupo 2, enquanto que a TBV30 não foi diferente entre os grupos. Os comprimentos de braçada correspondentes à VC (CBVC) e à V30 (CBV30) foram significantemente maiores no grupo G1 (2,41 ± 0,33 vs. 2,38 ± 0,30m.ciclo-1) do que no G2 (2,04 ± 0,43 vs. 1,97 ± 0,40m.ciclo-1), e similares entre si nos dois grupos. As correlações (r) entre a VC e a V30 e as variáveis técnicas correspondentes às duas velocidades foram significantes em todas as comparações (0,68 a 0,91). Portanto, a relação entre a velocidade e as variáveis técnicas correspondentes à VC e à V30 não é modificada pelo nível de performance aeróbia.