Influence of Physical Fitness, Anthropometric Profile, and Biological Maturation on Technical Performance and Enjoyment of Untrained Children Who Participate in Continuous and Fractional Small-Sided Games.

The objective is to determine the relationship between physical fitness, anthropometric measures, and biological maturation as they relate to technical performance in small-sided games (SSGs) of continuous and fractioned regimes. Methodology: A crossover-design study in which 12 children participated in two regimens of SSG (continuous and fractional). At the beginning of the study, all children were evaluated using physical fitness tests (horizontal jump test, vertical jump, cardiorespiratory fitness, and agility), anthropometric profile (weight, height, Body Mass Index (BMI), and waist circumference (WC)), and biological maturation (peak years of growth velocity). All sessions were recorded and analyzed with the Performance Assessment in Team Sports instrument, and at the end of each game each child was asked to answer a scale of enjoyment for physical activity. Results: The results of the paired samples t-test showed no significant differences in the measures of technical performance and perceived enjoyment for the continuous and fractional regimens of SSGs (p > 0.05). The correlation results showed that technical performance in the continuous and fractional regimes was related to agility, horizontal jump, and height, while biological maturation was only related to technical performance in the fractional regimen of SSGs. Perceived enjoyment showed a negative relationship with weight, height, BMI, and WC. Conclusion: The fractional and continuous regimens of SSGs implemented in this study induced similar technical demands and enjoyment. Furthermore, the results suggest that physical fitness, anthropometric profile, and biological maturation may influence the technical performance and enjoyment of SSGs.

Efectos de un protocolo de entrenamiento excéntrico sobre el rendimiento de velocidad en adolescentes de Chile / Effects of an Eccentric Training Protocol on Speed Performance in Chilean Adolescents

Resumen Introducción: Los beneficios del entrenamiento de fuerza sobre la velocidad de carrera han sido descritos en la bibliografía especializada, sin embargo, la evidencia sobre la influencia de estímulos específicos, basados en contracciones excéntricas sobre la musculatura extensora de cadera, no han sido demostrados. Objetivo: Determinar los efectos de un protocolo de entrenamiento basado en contracciones excéntricas (curl nórdico) sobre la velocidad de carrera en 20 metros en adolescentes de la región de Ñuble, Chile. Metodología: 42 individuos escolares fueron divididos en grupo experimental (n=22) y grupo control (n=20). El entrenamiento se desarrolló durante 6 semanas, con una frecuencia de 2 sesiones/semana, pasando de un volumen de 8 a 32 repeticiones de curl nórdico por sesión para el grupo experimental. El rendimiento de velocidad fue evaluado en 20 metros. La prueba T de Student fue utilizada para comparar los resultados pre y post intervención y se calculó el tamaño del efecto (TE). Resultados: Se encontraron diferencias estadísticamente significativas (p<0,05) a partir de la intervención en el grupo experimental (pre= 3,43 s. vs post= 3,15 s.), y un TE grande (1,04). Conclusión: Se concluye que el entrenamiento excéntrico basado en la aplicación de Curl nórdico, mejora el rendimiento de la velocidad de carrera.

Abstract Introduction: The specialized literature has described the benefits of strength training on running speed. In the same way, stimulation of training based on eccentric contractions has been shown to be effective in improving this quality. Objective: To determine the effects of a training protocol based on the stretch-shortening cycle (SSC) and another on eccentric contractions (Nordic curl) on the running speed in 20 meters in adolescents from the Ñuble Region, Chile. Methodology: 42 school subjects were divided into experimental group (n = 22) and control group (n = 20). The training was developed for 6 weeks, with a frequency of 2 sessions/week, going from a volume of 8 to 32 repetitions of Nordic curl per session for the experimental group. The speed performance was evaluated in 20 meters. With photocells, the T Student's was applied to compare the pre- and post-intervention results, and the effect size (ES) was calculated. Results: Statistically significant differences were found (p <0.05) from the intervention in the experimental group (pre= 3,43 s. vs post= 3,15 s.), and a large ES (1,04). Conclusion: It is concluded that the eccentric training based on the application of Nordic Curl improves the performance of the running speed.

Resumo Introdução: Os benefícios do treinamento de força na velocidade de corrida foram descritos na literatura especializada, no entanto, não foram demonstradas evidências sobre a influência de estímulos específicos, baseados em contrações excêntricas na musculatura extensora do quadril. Objetivo: Determinar os efeitos de um protocolo de treinamento baseado em contrações excêntricas (cacho nórdico) em velocidade de corrida de 20 m em adolescentes da região do Ñuble, Chile. Metodologia: 42 escolares foram divididos em um grupo experimental (n=22) e um grupo controle (n=20). O treino foi desenvolvido durante 6 semanas, com uma frequência de 2 sessões/semana, passando de um volume de 8 para 32 repetições de ondulação nórdica por sessão para o grupo experimental. O desempenho da velocidade foi avaliado acima de 20 metros. O teste T de Student foi usado para comparar os resultados pré e pós-intervenção e o tamanho do efeito (TE) foi calculado. Resultados: Foram encontradas diferenças estatisticamente significativas (p<0,05) da intervenção no grupo experimental (pré= 3,43 s. vs pós= 3,15 s.), e um TE grande (1,04). Conclusão: Conclui-se que o treinamento excêntrico baseado na aplicação do Curl nórdico melhora o desempenho da velocidade de corrida.

Changes in the Mechanical Properties of the Horizontal Force-Velocity Profile during a Repeated Sprint Test in Professional Soccer Players.

The objective was to analyze the changes in the horizontal force-velocity profile (HFVP) during the execution of repeated sprinting. Methods: Seventeen first-division Chilean soccer players completed a repeated sprint protocol consisting of eight sprints of 30 m with 25-s pauses between repetitions. The behavior of HFVP variables in each attempt was recorded from video recordings and analysis in the MySprint® application. Results: Differences (p < 0.05) were found between sprints in the following: time (T), starting from sprint 5 (F = 35.6; η2p = 0.69); theoretical maximum speed (V0), starting from sprint 4 (F = 29.3; η2p = 0.51); maximum power (PM), starting from sprint 5 (F = 17; η2p = 0.52); rate of decrease in force index produced at each step (DRF), starting from sprint 1 (F = 3.20; η2p = 0.17); and RF10, starting from sprint 1 (F = 15.5; η2p = 0.49). In comparison, F0 and RFpeak did not present any differences (p > 0.05). Conclusion: The HFVP variables more sensitive to the effects of fatigue induced by an RSA protocol are those associated with the production of force at high speeds, being V0, DRF, and Pmax, while those that contribute to the generation of force at the beginning of the sprint, F0 and RFpeak, do not present essential variations.