The aim of this study was to investigate the effects of fatigue induced by repeated sprint in the kicking accuracy and velocity in female soccer players. Eighteen Under-23 female soccer players from a Spanish professional club were subjected to a fatigue protocol based on a repeated-sprint ability (RSA) test. Measurements of the kicking velocity (maximal ball velocity) and accuracy (Loughborough Soccer Shooting Test) were taken before and after fatigue induction. Correlations between the change in the maximal ball velocity/accuracy and the heart rate (HR), the fatigue index (FI), the sprint decrement (S dec) and the rating of perceived exertion (RPE) were made. There was a significant difference between maximal ball velocity under fatigue conditions with respect to non-fatigue conditions (p = 0.001; ES = 0.89). However, despite a lower kicking accuracy punctuation with fatigue, this was not statistically significant (p = 0.433; ES = 0.22). Significant correlations were found between the maximal kicking velocity and the FI (r = 0.632, p < 0.01) and the S dec (r =-0.554, p < 0.05) and between the kicking accuracy and the RPE (r =-0.506, p < 0.05). In conclusion, there was a significant reduction in the maximal kicking velocity, but not in the kicking accuracy, under fatigued conditions. The RSA-related FI and S dec were the best predictors of the maximal kicking velocity and the RPE for the kicking accuracy.

Pen ˜as, C. Elite soccer players do not cover less distance in the second half of the matches when game interruptions are considered. J Strength Cond Res 38(4): 709-713, 2024-This study aimed to analyze quantitative differences in the physical demands of male elite soccer players between the first and second halves during official matches, accounting for effective playing time (the duration of play after subtracting the game interruptions) and playing positions. A total of 4,249 individual match observations of 412 outfield players competing in the Spanish first division league (LaLiga) were undertaken during the 2018-2019 season, using a computerized tracking system (TRACAB, Chyronhego, New York, NY). The players were classified into 5 positional roles: central defenders (CD), external defenders (ED), central midfielders (CM), external midfielders (EM), and forwards (F). The main results showed that in contrast to those observed when total playing time was considered, independent of playing position, there were no significant differences on high-speed running (HSR) (5.5 6 2.4 vs. 5.5 6 2.4 m•min 21 ) and sprint (5.3 6 3.3 vs. 5.4 6 3.3 m•min 21 ) distances between the first and second halves in professional soccer players when the effective playing time was considered. However, differences in match running performance at HSR and sprint distances between the first and second halves were dependent on players' playing position. Whereas ED and EM maintained HSR and sprint efforts during the second half, CD and CM significantly increased (p , 0.001) the distance covered at sprint during the second period of the match. Contrarily, F were unable to maintain their HSR (6.2 6 2.3 vs. 5.9 6 3.3 m•min 21 ) and sprint (7.0 6 3.5 vs. 6.5 6 3.4 m•min 21 ) match running performances during the second half. Such findings demonstrate that total playing time could overestimate fatigue-induced performance declines. Thus, effective playing time and playing position should be taken into account when interpreting the match running performance of professional soccer players.

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The aim of this study was to examine the effects of chronological age on acceleration and deceleration match performance in professional soccer players. A total of 5317 individual match observations were collected on 420 professional players competing in the Spanish LaLiga during the 2018–2019 season, using a multiple-camera computerised tracking system (TRACAB; ChyronHego, Melville, NY, USA). Players were classified using a k-means cluster analysis into four different age groups: 17–23 years, 24–27 years, 28–30 years, and 31–38 years. Linear mixed models were adjusted to compare the players’ match performance according to their age group and playing position (central defenders, external defenders, central midfielders, external midfielders, and forwards). The results showed that players aged between 31–38 years performed a significantly less total number of accelerations (ES=0.30–0.48) and decelerations (ES=0.29–0.49) in comparison with younger players. These age-related physical performance declines were more pronounced among central defenders, central midfielders, and forwards. However, no significant effects were obtained for players’ maximum acceleration and deceleration capacities. The current findings provide useful information for coaches and strength and conditioning specialists to better understand the effects of age on players’ physical performance and to develop age-tailored training programs.

ResumenEl objetivo del trabajo fue comparar las demandas físicas de tres situaciones de fútbol reducido, modificando de manera concurrente el espacio relativo de juego y el número de jugadores participantes, con las demandas propias de la competición en base al perfil físico de cada jugadora. También se estudiaron los efectos en la capacidad de salto vertical (CMJ) tras cada tarea de juego reducido y la relación con diferentes variables cinemáti-cas. El estudio se llevó a cabo con 12 jugadoras de fútbol de categoría sub 13. Las tareas fueron monitorizadas con dispositivos GPS, y consistieron en un 3x3 (51 m 2 /j), 4x4 (90 m 2 /j) y 5x5 (144 m 2 /j). También se monitorizaron 7 partidos de competición. Se encontraron diferencias sustanciales (> 75% probabilidad) en las demandas fí-sicas de cada tarea de fútbol reducido y respecto a la competición. No se encontraron diferencias sustanciales entre la pérdida de capacidad de salto de las distintas tareas de fútbol reducido. En conclusión, se ratifica la capacidad de los juegos reducidos para reproducir las demandas de la competición, aunque es necesario complementar las demandas de carrera a alta intensidad con algún entrenamiento complementario. Un aumento del espacio relativo se traduce en demandas físicas más exigentes y próximas a la competición. La pérdida de salto no es un método válido para discriminar cargas en diferentes tareas de fútbol reducido, aunque parece ser un buen indicador de la fatiga que acumula el jugador.Palabras clave: GPS, juegos reducidos, fútbol, CMJ. AbstractThe aim of the study was to compare the physical demands, based on the physical profile of each player, of three small sided games, modifying the relative pitch area per player, and the physical demands of the competition. The jumping capacity was also tested after each small sided games. A total of 12 football players under 13 participated in the study. The three small sided games and football matches were monitored using GPS devices: 3x3 (51 m 2 /p), 4x4 (90 m 2 /p) y 5x5 (144 m 2 /p) and 7 competition matches. Substantial differences (> 75% probability) were found in the physical demands of each small sided game and the competition, even though the jumping capacity was maintained without change. In conclusion, this study suggests that the capacity of small sided games reproduces the physical demands of the real game, although it is necessary mixed training gather high intensity training. An increase in the relative pitch area involves physical demands close to the full sized competition. The decrease of the jumping capacity is not a valid method for quantifying the load on a small sided game, even though it seems a good indicator of the player accumulating fatigue.

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