Effectiveness of beetroot juice derived nitrates supplementation on fatigue resistance during repeated-sprints: a systematic review.

In recent decades, the search for non-doping substances that enhance sports performance has increased. Ergogenic aids such as beetroot juice (BRJ) and BRJ rich in nitrates (NO3-) are widely used to cause physiological benefits that may lead to physical improvements. Therefore, the purpose of this systematic review was to explore the knowledge reported to date on the NO3- derived from BRJ intake effect on fatigue resistance during repeated sprints. A digital search was conducted following systematic review guidelines, and 18 studies met inclusion criteria from a total of 209 articles. In a third of the selected studies, the consumption of beet juice rich in NO3- contributes to an increase in nitrites in plasma that led to the rise in peak power, mean power, number of sprint repetitions, total work and time to task failure, and causes a decrease in fatigue index and sprints times. Some different dose has been proposed for both chronic and acute protocols. It seems that a chronic intake of ∼5-6 mmol of NO3- in 70 ml of BRJ, twice a day, for a minimum of 3-6 days could lead to a fatigue resistance improvement during repeated sprints. Besides, acute intake of NO3- 2.5-3 h before physical exertion or a dose of 250 ml/d to 500 ml/d of BRJ could lead to similar effective results. This systematic review presents some improvements (1.2-5.38%) in fatigue resistance during repeated sprints when consuming BRJ derived NO3-. The in-field practical meaning of these results should be explored.

Demands of two small-sided games of Costa Rican college soccer players

The purpose of this paper was to compare two small-sided games kinematics of Costa Rican college soccer players. Two SSG (2x10min, 3 min rest in between), C1 (600m2) and C2 (1200m2), were played by 14 college soccer players of Costa Rica. Global Positioning System was used to measure kinematic and physiological variables in both conditions. A mixed ANOVA was used, results suggested C1 and C2 were statistically different in speed (C1 C2). When analyzing the distance covered by speed category (low, moderate and high running actions) results suggest C2 had higher intensities compared to C1. This research confirms the findings of previousstudies on the effectiveness of SSG to simulate real game conditions in short periods of time. Conclusions: C2 had higher intensities compared to C1 game with lower physiological demand. Likewise, the C2 resembles more accurately matches in official conditions of Costa Rican players.

O propósito desta pesquisa foi comparar as demandas cinemáticas em dois tipos de dimensões de jogo em 14 jogadores costarricenses de futebol universitário. Estes jogaram dois jogos em campo reduzido (SSG) (2x10 min, 3 min de descanso): C1 (600m2) e C2 (1200 m2). Utilizou-se um Sistema de Posicionamento Global para medir as variáveis cinemáticas e fisiológicas em ambas as condições. Utilizou-se um ANOVA misto; os resultados sugeriram que C1 e C2 foram estatisticamente diferentes em velocidade (C1 C2). Ao analisar a distância percorrida pela categoria de velocidade, em ações de corrida baixa, moderada e alta intensidade, os resultados sugerem que C2 possui maiores intensidades em comparação a C1. Esta pesquisa confirma os resultados de estudos prévios sobre a efetividade de SSG para simular condições de jogo real em períodos curtos de tempo. Conclusões: O C2 apresentou uma maior intensidade em comparação ao jogo C1, com menores demandas fisiológicas. Igualmente, o C2 reflete de maneira mais exata as condições em jogos oficiais de jogadores costarricenses.

El propósito de esta investigación fue comparar las demandas cinemáticas en dos tipos de dimensiones de juego en jugadores de fútbol universitario costarricenses. 14 jugadores universitarios de fútbol de Costa Rica jugaron dos juegos en campo reducido (SSG) (2x10min, 3min de descanso): C1 (600m2) y C2 (1200 m2). Se utilizó un Sistema de Posicionamiento Global para medir las variables cinemáticas y fisiológicas en ambas condiciones. Se utilizó un ANOVA mixto; los resultados sugirieron que C1 y C2 fueron estadísticamente diferentes en velocidad (C1 C2). Al analizar la distancia recorrida por la categoría de velocidad; en acciones de carrera baja, moderada y alta intensidad, los resultados sugieren que C2 posee mayores intensidades en comparación con C1. Esta investigación confirma los resultados de estudios previos sobre la efectividad de SSG para simular condiciones de juego real en períodos cortos de tiempo. Conclusiones: El C2 presentó una mayor intensidad en comparación con el juego C1 con menores demandas fisiológicas. Asimismo, el C2 refleja de manera más exacta las condiciones en partidos oficiales de jugadores costarricenses.