The Influence of Age on the Anthropometric and Performance 1 Characteristics of High Level Youth Female Soccer Players

37 38 The purpose of this study was to evaluate the anthropometric and performance characteristics 39 of high level youth female soccer players by annual-age category (U10-U16). Data were 40 collected from 157 female soccer players (U16; n=46, U14; n=43, U12; n=38, U10; n=30), 41 recruited from three high level female soccer academies in England. Players completed 42 assessments of anthropometry (height and body mass), isometric mid-thigh pull strength 43 (IMTP), jump height (CMJ), aerobic capacity (YYIRL1), change of direction (505-left/right), and 44 speed (10 and 30 m). Magnitude based-inferences were used to assess for practical significance 45 between consecutive age groups. Height (very likely – most likely), body mass (very likely – most 46 likely), absolute strength (most likely), jump height (likely – very likely), and distance on the 47 YYIRL1 (possibly – most likely) were greater in older players. Both speed and change of 48 direction time were most likely to very likely lower in older players. However, only most likely 49 trivial-possibly trivial differences were observed in relative strength between age groups. 50 Findings suggest that physical characteristics except for relative strength differentiate by age 51 categories. These findings provide comparative data and target reference data for such 52 populations and can be used by coaches and practitioners for player development purposes. 53 Practitioners should be aware that relative strength does not differ between age categories in 54 high level youth female soccer players. 55 56