Search results for " jump"
showing 10 items of 171 documents
Take-off analysis of the Olympic ski jumping competition (HS-106m).
2007
Abstract The take-off phase (approximately 6 m) of the jumps of all athletes participating in the individual HS-106 m hill ski jumping competition at the Torino Olympics was filmed with two high-speed cameras. The high altitude of the Pragelato ski jumping venue (1600 m) and slight tail wind in the final jumping round were expected to affect the results of this competition. The most significant correlation with the length of the jump was found in the in-run velocity ( r =0.628, p n =50). This was a surprise in Olympic level ski jumping, and suggests that good jumpers simply had smaller friction between their skis and the in-run tracks and/or the aerodynamic quality of their in-run position …
A sliding mode approach to H∞ synchronization of master–slave time-delay systems with Markovian jumping parameters and nonlinear uncertainties
2012
Author's version of an article published in the journal: Journal of the Franklin Institute. Also available from the publisher at: http://dx.doi.org/10.1016/j.jfranklin.2011.09.015 In this paper, a sliding-mode approach is proposed for exponential H∞ synchronization problem of a class of masterslave time-delay systems with both discrete and distributed time-delays, norm-bounded nonlinear uncertainties and Markovian switching parameters. Using an appropriate LyapunovKrasovskii functional, some delay-dependent sufficient conditions and a synchronization law, which include the masterslave parameters are established for designing a delay-dependent mode-dependent sliding mode exponential H∞ synch…
Effects of acute b-alanine supplementation on countermovement jump performance after a 4x400 m fatigue protocol: A randomized, double-blind, placebo-…
2022
This study aimed to examine the effect of acute beta-alanine (β-alanine) supplementation on jump performance after a strenuous fatigue protocol. Twelve healthy young men (age 21.4±0.5 years, body height 180.2±5.8 cm, body mass 76.6±9.2 kg) volunteered to participate in this randomized, double-blind, placebo-controlled trial. The experimental group ingested 3.2 g of β-alanine (separated into two 1.6 g dosages) mixed with 23 g of glucose, whereas the placebo group ingested two dosages containing 23 g of glucose. Following the supplementation intake, participants completed a jump protocol involving countermovement jump (CMJ) and four consecutive countermovement jumps (CMJ-4). Subsequently, a 4…
Training the Vertical Jump to Head the Ball in Soccer
2012
R esearchers involved in the training methodology to improve jump ability proposed a variety of techniques and exercise modalities (22,15,4). Nevertheless, the question on what percentage of training should be dedicated to strength and what to power seems unresolved. First of all, to better understand the matter, we have to stress the difference between strength and power. Generally speaking, in athletics, the rate of force development (RFD) is much more important than strength alone; the average RFD (mRFD) can be estimated as the ratio Fmax/Tmax, where Tmax is the time to reach the peak force, whereas Fmax is the maximum force. This ratio is also named explosive strength, commonly computed…
Altération des performances neuromusculaires après un exercice physique prolongé. Analyse comparée d'une épreuve de marathon et de triathlon
1998
The aim of this study was to compare the effects of a marathon and a triathlon on isometric and dynamic neuromuscular performances. Seven triathletes took part in 3 experimental situations : a 2 h 15 mn triathlon (TRI) (30 min swimming, 60 min cycling and 45 min running), a 2 h 15 mn marathon (MA) and a 45 min isolated run done at triathlon speed. The results showed a reduction of the isometric endurance time for knee extensor muscles (35 % of maximal voluntary contraction) after TRI (41 ± 24 %) and after MA (59 ± 19 %). The height of rise of the center of gravity of the counter-movement jumps (CMJ) was also significantly lower after MA (-12 ± 1 cm) than after TRI (-2,5 0,5 cm). Kinetic ana…
Is it still important to be light in ski jumping?
2019
In ski jumping low body weight development resulted in some serious underweight problems and therefore the International Ski Federation (FIS) decided to solve the problem by relating maximum ski length to Body Mass Index (BMI) in 2004. The present study examined the current relationship between body weight, ski length and performance (jumping distance) in ski jumping. By adopting the BMI regulation to specifications for competition equipment, the FIS succeeded in stopping the alarming development of underweight problems in ski jumping. However, as the results of the present study show, the BMI regulation adopted by the FIS has reduced the advantage of being light, but despite the use of sho…
Predictive control of convex polyhedron LPV systems with Markov jumping parameters
2012
The problem of receding horizon predictive control of stochastic linear parameter varying systems is discussed. First, constant coefficient matrices are obtained at each vertex in the interior of linear parameter varying system, and then, by considering semi-definite programming constraints, weight coefficients between each vertex are calculated, and the equal coefficients matrices for the time variable system are obtained. Second, in the given receding horizon, for each mode sequence of the stochastic convex polyhedron linear parameter varying systems, the optimal control input sequences are designed in order to make the states into a terminal invariant set. Outside of the receding horizon…
Acute effects of fatigue to strength and power variables in edurance trained athletes
2015
The purpose of this bachelor thesis was to investigate how fatigue affects strength and power in endurance trained athletes. This thesis is written for the athletes, coaches and researchers in the field of sport. Total of 7 endurance athletes (age 23.3 years ± 1.3, height 174.7 cm ± 6.4, weight 66.5 kg ± 8.4) volunteered for the study, 4 male and 3 female. Hypotheses were that measured variables do not decrease after fatiguing protocol and that the potentiation may counteract fatigue. Fatigue was induced in a continuous maximal treadmill running, where speed was increased every five minutes by one km/h. When necessary, after 45 minutes of running, speed was increased every minute by one km/…
The Origin of Non-thermal Fluctuations in Multiphase Flow in Porous Media
2021
Core flooding experiments to determine multiphase flow in properties of rock such as relative permeability can show significant fluctuations in terms of pressure, saturation, and electrical conductivity. That is typically not considered in the Darcy scale interpretation but treated as noise. However, in recent years, flow regimes that exhibit spatio-temporal variations in pore scale occupancy related to fluid phase pressure changes have been identified. They are associated with topological changes in the fluid configurations caused by pore-scale instabilities such as snap-off. The common understanding of Darcy-scale flow regimes is that pore-scale phenomena and their signature should have a…
Development of an individualized familiarization method for vertical jumps
2013
OBJETIVO: Propor um método de familiarização individualizado para saltos verticais e verificar o seu efeito na variabilidade intrassujeito. MÉTODOS: Cinquenta e três homes (média ± DP; idade 23,5 ± 3,3 anos; estatura 1,76 ± 0,08 m; massa 72,8 ± 8,6 kg; percentual de gordura 12,9 ± 5,2%) realizaram sucessivos saltos até atingir o nível de estabilidade proposto. Após 48 h este processo era repetido e a estabilidade entre dias era verificada, se necessário, mais sessões eram realizadas. O nível de estabilidade foi determinado por um teste z, com intervalo de confiança de 95%. Após o processo de familiarização, duas sessões experimentais adicionais foram realizadas para determinar a confiabilid…