Explore the vast range of titles available.

The relative age effect is a well-researched phenomenon, however there is still a dearth of understanding in track and field and female sport. This study investigated the role of relative age on selection for international competition of Spanish age group athletes between 2006-2014. Six hundred and forty two athletes competed for Spain at U20 or U18 age group international competition (n = 359 males; 283 females) across 9 years. The birthdates of these athletes were compared against the population of registered athletes at that time (14,502 males; 10,096 females). The results highlighted the influential role of relative age on selection to these opportunities. In line with previous research, this effect was mediated by age and gender, with stronger effects for both males and younger athletes (U18). The data best supported the 'maturation-selection' hypothesis as a mechanism for RAEs. These results highlight the need to carefully consider the role and need for international competitive opportunities at different age groups. A number of possible context relevant solutions are discussed, including correction adjustments techniques and competition structure within track and field.

The present review aims to analyse the research studies related to resisted sprint methods and their effects on sprint performance, power output and strength, and also the current situation in the use of the optimal load in resisted sprint training. The data were obtained from an analysis carried out in the MEDLINE/PubMed and SportDiscus databases from 1985 to 2012, with the key words “Sprint Running”, “Resisted Training”, “Sled Towing”, “Resisted Sprint” and “Resisted Sprinting”. Seven studies were selected as they included sled-towing exercises in sprinting. Results showed agreement regarding the load’s standard in sled-towing, and all studies utilised loads between 5% and 30% of body mass (BM). Recommendations for designing resisted sprint training with loads focus on resistance lower than 13% of BM to prevent a decrease of more than 10% in sprinting velocity and to maintain the athlete’s unloaded sprinting movement patterns. The lack of research focusing on the relationship between sled-towing exercise and power output and strength variables makes it difficult to determine the load to optimise specific strength and power in sprinting; thus, the use of higher loads in resisted sprint training programs remains limited. El objetivo de esta revisión es analizar la literatura científica en relación a los efectos que el trabajo con sobrecarga tiene sobre el rendimiento en velocidad, potencia y producción de fuerza así como la situación actual en relación a la carga adecuada de entrenamiento. Se emplearon las bases de datos internacionales MEDLINE/PubMed y SportDiscus entre 1985 y 2012 utilizándose las siguientes palabras clave: “Sprint Running”, “Resisted Training”, “Sled Towing”, “Resisted Sprint”, “Resisted Sprinting”. Se identificaron 7 investigaciones que cubrían los criterios establecidos. Todos los estudios muestran un completo acuerdo en cuanto al criterio de selección de cargas, todas los estudios utilizan el peso corporal (PC) con cargas entre 5% y 30%. Y las recomendaciones para el diseño del entrenamiento resistido con trineo se centran principalmente en la utilización de cargas inferiores al 13% PC, de esta manera se evita una disminución de la velocidad por encima del 10% manteniéndose el patrón técnico de carrera. La ausencia de estudios que ahonden en la relación del trabajo resistido y variables de fuerza o potencia, dificulta la determinación de cuál sería la carga adecuada para la optimización de la fuerza y potencia especifica en el sprint, limitando la utilización de cargas altas en programas de entrenamiento con arrastre de trineo.