Can the Supido Radar Be Used for Measuring Ball Speed during Soccer Kicking? A Reliability and Concurrent Validity Study of a New Low-Cost Device

The aim was to analyze the reliability and validity of a low-cost instrument, based on a radar system, to quantify the kicking ball speed in soccer. A group of 153 male soccer players (under-13, n = 53; under-15, n = 54; under-18, n = 46) participated in this study. Each player performed three kicks on the goal in a standardized condition while the ball speed was measured with three different devices: one Radar Stalker ATS II^® (reference criterion) and two Supido Radar^® (Supido-front of the goal and Supido-back of the goal). The standard error of measurement (SEM) expressed as a coefficient of variation (CV) and the intraclass correlation coefficient (ICC) were employed for assessing the reliability of each instrument. Stalker and Supido-back showed very high absolute (CV = 4.0-5.4%) and relative (ICC = 0.945-0.958) reliability, whereas Supido-front resulted in moderate to low reliability scores (CV = 7.4-15%, ICC = 0.134-0.693). In addition, Lin's concordance correlation coefficient (CCC) values revealed an 'almost perfect' agreement between Stalker and Supido-back for the average (r = 0.99) and maximal (r = 0.98) ball speed, regardless of the ball speed range analyzed. However, Supido-front resulted in a poor degree of concordance (CCC = 0.688) and a high magnitude of error (17.0-37.5 km·h^-1) with the reference Stalker radar gun. The Supido Radar^® placed behind the goal could be considered a reliable and valid device for measuring ball speed in soccer.

Relationship between Physical Fitness and Match Performance Parameters of Chile Women's National Football Team

The aim of this study was to analyze the relationships between the level of physical fitness and the physical performance parameters recorded by GPS in official FIFA matches of the Chilean women’s senior national football team in the period 2018–2020. Twenty-six female field players (age (mean ± SD) 26.8 ± 3.3 years, height 157.8 ± 21.5 cm, weight 58.9 ± 4.9 kg) participated in the study. Physical fitness variables were assessed: muscular strength, countermovement jump (CMJ), speed, agility and aerobic fitness. Physical performance variables were recorded by GPS in 26 official FIFA matches. The most notable associations with significant statistical significance (p < 0.001) were those observed between neuromuscular variables such as time to run 10 m (T10; r = −0.629) and jump (CMJ; r = 0.502) and the number of accelerations; aerobic fitness showed a highly significant relationship with meters run per minute (M/M; r = 0.589). The findings of this study provide evidence of how the level of physical fitness (neuromuscular and aerobic) relates to physical performance parameters recorded in official competitions.

Acute Effects on Physical Performance Measures after 45 Min of Official Competition in Youth Soccer Players

(1) Background: An improved understanding of soccer players' match-related physical performance and recovery may help conditioning programs and re-warm up strategies to increase team performance during official competitions. Therefore, the aim of this study was to analyze the acute effects of 45 min of official competition (first half in matches) on physical performance variables in U-16 youth soccer players. (2) Methods: 20 male soccer players (age: 14.4 ± 0.5 years; height: 1.70 ± 0.05 cm; body mass: 65.1 ± 11.6 kg) were recruited to participate in this study. Data was collected from five official matches. Participants performed the assessments in two stages of each match: after the pre-match warm-up and after the first half. Tests included rate of perceived exertion (RPE), 30-m sprint and countermovement (CMJ). (3) Results: Statistically significant differences were found (p < 0.001) when the measurements prior to the game were compared with those recorded after half time across all variables. Effect sizes (ES) were very large for RPE (ES = 1.82), moderate for 30-m sprint times (ES = 0.64) and small for CMJ (ES = -0.25). (4) Conclusions: After 45 min of official competition, our results suggest that U-16 soccer players demonstrated a reduction in sprint and jump performance, in addition to a higher RPE. Hence, this information could be useful when designing re-warming strategies that can be performed before the second half.

Efectos de las medidas de confinamiento por COVID-19 en el grado de bienestar y la carga de entrenamiento de las jugadoras de la selección nacional de fútbol de Chile

Introducción. Debido a la actual pandemia por COVID-19, muchos países tomaron medidas de control y prevención como el confinamiento obligatorio, afectando todas las esferas de la vida. Ya que los futbolistas profesionales no son una excepción, este tipo de medidas puede tener un impacto negativo en su bienestar y en su percepción sobre las cargas de entrenamiento. Objetivo. Determinar los efectos de las medidas de confinamiento por COVID-19 en la carga de entrenamiento y el grado de bienestar de jugadoras de fútbol profesional de Chile. Materiales y métodos. Estudio transversal, exploratorio-descriptivo realizado en 32 jugadoras de la Selección Nacional de Fútbol de Chile. El grado de bienestar y la carga de entrenamiento se evaluaron mediante un cuestionario desarrollado en 2010 y mediante la escala de percepción subjetiva del esfuerzo (PSE) y el volumen de entrenamiento expresado en minutos, respectivamente. Ambas evaluaciones se realizaron en 2 periodos de 12 semanas: periodo preparatorio regular (12/12/2019-10/03/2020) y periodo de confinamiento (16/03/2020-07/06/2020). Los datos se analizaron mediante estadística descriptiva y la prueba de Wilcoxon se utilizó para determinar si hubo diferencias significativas entre ambos periodos. Resultados. Se encontraron diferencias significativas (p<0.05) y umbrales de tamaño del efecto (TE) iguales a 1.2, 2.0 y 4.0 (grande, muy grande y extremadamente grande, respectivamente) entre ambos periodos en todas las variables evaluadas por el cuestionario de bienestar (a excepción de calidad de sueño): dolor muscular y nivel de estrés (TE=1.9), fatiga percibida (TE=2.5), bienestar general (TE=2.4) y estado de ánimo (TE=4.2). No se observaron diferencias en la PSE (TE=0.1) entre ambos periodos. Conclusiones. El confinamiento obligatorio afectó negativamente el grado de bienestar de las participantes, por lo que es necesario que los cuerpos técnicos monitoreen constantemente, de manera individual y colectiva, el grado de bienestar de los futbolistas profesionales durante estos periodos; si bien la percepción en la carga de entrenamiento no se vio afectada, no es posible asegurar que un periodo mayor de confinamiento no la disminuya y esto resulte en una baja del rendimiento.