COMPARISON OF GROUND REACTION FORCES BETWEEN IN-PLACE AND FORWARD WATER RUNNING AT TWO LEVELS OF IMMERSION

This study compared GRF of in-place and forward water running at two levels of immersion. Twenty healthy subjects executed both exercises at a self selected speed at hip and chest immersion. Variables analyzed were: vertical peak (Fy), anterior peak (Fx anterior) and posterior peak (Fx posterior). Two-factor repeated measures ANOVA was used with

LOAD DURING THE VERTICAL JUMP IN WATER: VALUES FOR PRESCRIPTION IN HYDROTHERAPY

This study aimed to analyse the vertical component of the ground reaction force (GRF) in the vertical jump in water performed by men and women at two levels of immersion. 11 men and 11 women performed three vertical jumps on a water-proof force plate at hip and chest levels of immersion. No effect of gender was observed. No difference between levels of immersion was found for peak of propulsion [1.85 and 1.89 units of body weight (BW) at the hip and chest respectively]. During the landing phase, the force peak was significantly higher at the hip level (2.62 BW) than at the chest level (2.07 BW). The force during the propulsion phase was similar between the immersions; however the vertical load on landing needs to be considered when prescribing this exercise, even in water

A DYNAMOMETRIC METHOD FOR THE EVALUATION OF HIKING IN LASER BOATS

This study aimed to develop a dynamometric method for the evaluation of hiking in Laser boats. The boat’s and sailor’s centres of mass, the hiking distance and the hiking moment were calculated from the ground reaction force, acquired by two force plates located under the boat hoof. Three sailors performed different hiking positions varying their hip and knee angles. Pearson’s coefficient was used to verify the correlation between the measures obtained through the dynamometric method and a kinematic method. A very high correlation was observed between the methods (r=0.99) and the mean error was approximately 1% for both hiking distance and moment. Thus, the new method seems to be valid and efficient since it measured the variables in a fast and precise way, facilitating the analysis and assisting sailors and coaches on decision taking

RELATIVE ERROR ANALYSIS DURING REPRODUCTION OF ISOMETRIC FORCE OF KNEE EXTENSORS IN YOUNG ADULTS

This study compared the force reproduction of isometric knee extension at 60°, between the target forces at 30%, 50% and 70% of the maximum voluntary isometric force (MVIF) in young adults. Twenty young males took part in the study. The trials were performed on an instrumented chair developed for the study. Feedback was given to the participants during three trials prior the beginning of data collection in each analyzed target force. Participants performed 10 trials without any feedback for the target force at 30% and 50% of the MVIF and 3 trials for the target force at 70% of MVIF. The relative error decreased as the target force increased. The differences were significant between 30% and 70% (p=0.01) and between 50% and 70% (p=0.03). The reproduction of higher forces during isometric extension of the knee will produce lower relative errors for this specific task

Training loads and RSA and aerobic performance changes during the preseason in youth soccer squads

The aims of this study were to compare the internal training load (ITL) in soccer players of two competitive age groups (under-15 [U-15] and under-19 [U-19]) during an 8-week preseason training period and compare the associated changes in physical performance measures. Eighteen U-15 and twelve U-19 players were monitored over an 8-week period during the preseason phase. The ITL was monitored using the session rating of perceived exertion (RPE) method. Before and after the preseason period, physical performance was assessed by best (RSA(best)) and mean (RSA(mean)) times in a repeated sprint ability (RSA) test and peak velocity derived from the Carminatti test (PVT-CAR). Total weekly ITL increased with age (U-15: 13770 +/- 874 AU vs. U-19: 33584 +/- 2506 AU; p < 0.001). In addition, U-19 players perceived training sessions as heavier than U-15 players (6.1 +/- 0.3 vs. 5.3 +/- 0.3 AU, respectively; p < 0.001). After the preseason period, very likely to almost certainly positive changes were observed for all performance measures in both age groups. However, the U-15 group had possibly superior gains in RSA(best) (+ 1.40%, 90% CL - 0.29 to 3.05, with ES = 0.35) and likely higher effects in RSA(mean) (+ 1.89%, 90% CL 0.04 to 3.70, with ES = 0.53) and PVT-CAR (+ 2.71%, 90% CL 0.35 to 5.01, with ES = 0.37) compared to the U-19 group. In conclusion, our findings demonstrate that the U-19 group accumulate higher total weekly ITLs than the U-15 group during the preseason phase due to longer and heavier training sessions. However, the U-15 group obtained superior gains in soccer-specific physical abilities while accumulating half the total ITLs during lighter training sessions

Predição da força de reação do solo durante a corrida na água

Este estudo visou desenvolver um modelo para a predição da força de reação do solo na corrida subaquática. Participaram 20 sujeitos (9 homens e 11 mulheres), que realizaram corrida subaquática em dois níveis de imersão e três velocidades. Para cada sujeito foram coletadas seis passagens válidas em cada condição, com a utilização de uma plataforma subaquática de força. O modelo para predição da força foi construído por regressão linear múltipla. Foram consideradas variáveis dependentes a componente vertical e a componente ântero-posterior da força de reação do solo. As variáveis imersão, sexo, velocidade, massa corporal, densidade corporal e percentual de gordura foram consideradas independentes. Permaneceu no modelo final de regressão para a componente vertical a velocidade (pThis study aimed at developing a model to predict ground reaction force during deep-water running. A total of 20 subjects ((9 men, 11 women) ran in water at two immersion levels and three different speeds. Each subject performed six valid trials in each condition, data being captured by an underwater force plate. The force prediction model was build by multiple linear regression. Dependent variables were the vertical and anteroposterior components of the ground reaction force; independent variables were runners' immersion, sex, speed, body mass, body density, and percentage of fat. At the final regression model for the vertical component, only speed remained (