Changes in sprint-related outcomes during a period of systematic training in a girls' soccer academy

Longitudinal data tracking performance indicators collected during structured training are lacking in young female soccer players. Therefore, changes in 5-m acceleration, 20-m speed, change-of-direction speed and repeated-sprint ability were quantified during a three-year period in an FA Centre of Excellence. Fourteen players (mean age = 12.1 years, SD = ±0.9) were recruited and their best performance scores from pre-season and in-season testing were averaged. Players were typically exposed to soccer (2 x 90 min per week) and strength and conditioning training (1 x 70 min per week) and played 20 soccer matches (50-80 min) during 35-week seasons. Mean (±90%CL) overall improvements over the three years were 5.9% (1.3) (most likely large) for speed, 4.0% (1.0) (most likely large) for repeated-sprint ability, 8.8% (1.1) for acceleration and 8.3% (1.4) for change-of-direction speed (both most likely very large). Improvements between years one and two ranged from most likely moderate to very large. Further small improvements in change-of-direction speed and 20-m speed (both likely) were observed between years two and three. Individual differences in response were apparent only for change-of-direction speed, which were moderate and small between years two and three. Most likely very large to near perfect within-player correlations were observed between maturation and sprint measures. These data from a single-arm longitudinal study indicate that systematic exposure to training, which includes one dedicated strength and conditioning session each week, is associated with improvements in sprint related physical qualities in girls.