Effect of weighted sled towing on sprinting effectiveness, power and force-velocity relationship

This study aimed to compare the components of force-velocity (F-V) and power-velocity (P- V) profiles and the mechanical effectiveness of force application (or force ratio–RF) among various sled-towing loads during the entire acceleration phase of a weighted sled sprint. Eighteen sprinters performed four 50-m sprints in various conditions: unloaded; with a load corresponding to 20% of the athlete’s body mass (BM); with a load of 30% BM; and with a load of 40% BM. Data were collected with five video cameras, and the images were digitised to obtain velocity from the derivation of the centre-of-mass position. F-V and P-V compo- nents and RF were estimated from sprinting velocity-time data for each load using a vali- dated method that is based on an inverse dynamic approach applied to the sprinter’s centre- of-mass (it models the horizontal antero-posterior and vertical ground reaction force compo- nents) and requires only measurement of anthropometric and spatiotemporal variables (body mass, stature and instantaneous position or velocity during the acceleration phase). The theoretical maximal velocity decreased with load compared with the unloaded condition (for 20% BM: -6%, effect size (ES) = 0,38; for 30% BM: -15%, ES = 1.02; for 40% BM: -18%, ES = 1.10). The theoretical maximal horizontal force (F0) and maximal power were not dif- ferent among conditions. However, power at the end of the acceleration phase increased with load (40% BM vs 0%: 72%; ES = 2.73) as well as the maximal mechanical effectiveness (12%; ES = 0.85). The linear decrease in RF was different between 30 or 40% BM and the unloaded condition (-23%; ES = 0.74 and 0.66). Better effectiveness may be developed with 40% BM load at the beginning of the acceleration and with the various load-induced changes in the components of the F-V and P-V relationships, allowing a more accurate determination of optimal loading conditions for maximizing power

INFLUENCE OF DEEP WATER RUN TRAINING SUPPLEMENT ON THE MAINTENANCE OF AEROBIC PERFORMANCE AND KINEMATICS OF MIDDLE-DISTANCE RUNNERS

The purpose of this study was to examine whether trained competitive runners could maintain on-land running performance and kinematics, using 8 wk of deep water run supplement training (30%) instead of just on-land training. Eight trained male runners (V02MAX: 53,3 ± 4.1 ml. Kg,1. min,1) were assigned to one of the two groups, on-land run just (R) or water run supplement (WR). Following 8 wk of workouts, no significant intragroup or intergroup differences were observed for treadmill V02MAX, running economy, horizontal velocity, stride length, stride rate, time of support, time of flight and segmental body positions. It was concluded that deep water running may serve as an effective training supplement to land-based running for the maintenance of aerobic performance and running kinematics for up 8 wk in trained middle-distance runners

Influência das variáveis antropométricas na economia de corrida e no comprimento de passada em corredoras de rendimento

This study was designed to investigate the relationship between running economy (ECO), step length (CP) and body dimensions. Five female were tested for one submaximal velocity, very close to usual training intensities (12 km.h-1), and one high submaximal velocity, near the anaerobic threshold (14 km.h-1). Body weight, body fat, height, leg length and relative low extremity length were determined. The test of Pearson´s correlation (pO objetivo do estudo foi investigar a relação entre economia de corrida (ECO), comprimento de passada (CP) e dimensões corporais. Cinco mulheres correram em duas intensidades submáximas: uma velocidade correspondente a velocidade utilizada em treino (12 km.h-1) e, uma velocidade próxima da velocidade no limiar anaeróbio (14 km.h-1). A massa corporal, o percentual de gordura, a estatura, o comprimento de passada e o comprimento de passada relativo ao comprimento de perna foram determinadas em ambas as velocidades. Foi feito o teste de correlação de Pearson (

Uma atualização de novas cultivares de arroz irrigado por inundação no modelo SimulArroz

The objective of this work was to model, in the SimulArroz model, the three flood-irrigated rice (Oryza sativa) cultivars currently most grown in the state of Rio Grande do Sul, Brazil. The experiments to calibrate and validate the model were conducted in the municipalities of Cachoeirinha, Santa Maria, Uruguaiana, Santa Vitória do Palmar, and Cachoeira do Sul during four crop seasons. The number of leaves, phenology, aboveground dry matter biomass, and yield of each cultivar were evaluated. The results showed a slight overestimate of the R1, R4, and R9 stages; however, overall, the SimulArroz model had a good performance in simulating rice phenology for the three studied genotypes. Furthermore, the model had a reasonable accuracy in simulating aboveground dry matter and yield. The root-mean-square error (RMSE) for aboveground dry matter (leaves, stems, panicles, and grains) ranged from 0.5 to 3.0 Mg ha-1. For yield, the RMSE ranged from 0.8 to 1.3 Mg ha-1. The calibration of the SimulArroz model is efficient in simulating the growth, development, and grain yield of the most important flood-irrigated rice cultivars in Southern Brazil and can be used to estimate harvest forecast and yield potential, as well for yield gap studies.O objetivo deste trabalho foi modelar, no modelo SimulArroz, as três cultivares de arroz (Oryza sativa) irrigado atualmente mais cultivadas no Estado do Rio Grande do Sul. Os experimentos para calibrar e validar o modelo foram conduzidos nos municípios de Cachoeirinha, Santa Maria, Uruguaiana, Santa Vitória do Palmar e Cachoeira do Sul, durante quatro safras. Foram avaliados o número de folhas, a fenologia, a biomassa da matéria seca da parte aérea e a produtividade de cada cultivar. Os resultados mostraram uma leve superestimativa dos estádios R1, R4 e R9; no entanto, no geral, o modelo SimulArroz apresentou bom desempenho na simulação da fenologia do arroz para os três genótipos estudados. Além disso, o modelo teve uma precisão razoável em simular matéria seca da parte aérea e produtividade. A raiz quadrada do erro quadrático médio (RMSE) para matéria seca da parte aérea (folhas, caules, panículas e grãos) variou de 0,5 a 3,0 Mg ha-1. Para produtividade, a RMSE variou de 0,8 a 1,3 Mg ha-1. A calibração do modelo SimulArroz é eficiente em simular o crescimento, o desenvolvimento e a produtividade de grãos das cultivares de arroz irrigado mais importantes no Sul do Brasil e pode ser utilizada para estimar a previsão de safra e o potencial de produtividade, bem como para estudos de lacunas de produtividade

Effect of weighted sled towing on sprinting effectiveness, power and force-velocity relationship.

This study aimed to compare the components of force-velocity (F-V) and power-velocity (P-V) profiles and the mechanical effectiveness of force application (or force ratio-RF) among various sled-towing loads during the entire acceleration phase of a weighted sled sprint. Eighteen sprinters performed four 50-m sprints in various conditions: unloaded; with a load corresponding to 20% of the athlete's body mass (BM); with a load of 30% BM; and with a load of 40% BM. Data were collected with five video cameras, and the images were digitised to obtain velocity from the derivation of the centre-of-mass position. F-V and P-V components and RF were estimated from sprinting velocity-time data for each load using a validated method that is based on an inverse dynamic approach applied to the sprinter's centre-of-mass (it models the horizontal antero-posterior and vertical ground reaction force components) and requires only measurement of anthropometric and spatiotemporal variables (body mass, stature and instantaneous position or velocity during the acceleration phase). The theoretical maximal velocity decreased with load compared with the unloaded condition (for 20% BM: -6%, effect size (ES) = 0,38; for 30% BM: -15%, ES = 1.02; for 40% BM: -18%, ES = 1.10). The theoretical maximal horizontal force (F0) and maximal power were not different among conditions. However, power at the end of the acceleration phase increased with load (40% BM vs 0%: 72%; ES = 2.73) as well as the maximal mechanical effectiveness (12%; ES = 0.85). The linear decrease in RF was different between 30 or 40% BM and the unloaded condition (-23%; ES = 0.74 and 0.66). Better effectiveness may be developed with 40% BM load at the beginning of the acceleration and with the various load-induced changes in the components of the F-V and P-V relationships, allowing a more accurate determination of optimal loading conditions for maximizing power

Correlação de parâmetros cinemáticos angulares com velocidade linear durante corrida em esteira

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Correlação de parâmetros cinemáticos angulares com velocidade linear durante corrida em esteira

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