Influence of body size and skeletal maturity status on strength and motor performances of soccer players 9-16 years.

The contributions of height, weight and skeletal age (SA) to strength and motor performances of male soccer players 9-12 (n = 60) and 13-16 (n = 52) years were estimated. SA was assessed with the Fels method, and was expressed as the standardized residual of the regression of SA on chronological age CA (SAsr). Static strength (right + left grip), speed (5 m, 20 m sprints), acceleration (10 to 20 m), agility (figure-of-eight run), explosive strength (vertical jump) and endurance (yo-yo intermittent shuttle run, 13-16 years only) were measured. Hierarchical multiple regression was used. The interaction of SAsr with body size (height and height x weight interaction) explained most of the variance in strength in both age groups, 9-12 years (51.6%) and 13-16 years (56.7%), and in speed (31.4%, 38.7%), acceleration (39.6%), and explosive strength (32.6%) among players 13-16 years. In contrast, SAsr alone explained limited amounts of variance in strength, speed, acceleration and vertical jump among players 9-12 years (1.4-4.5%) and 13-16 years (0-0.5%). Results for agility varied with CA group, while SAsr per se was the primary contributor to endurance among players 13-16 years (18.5% of the variance). Although the influence of body size and skeletal maturity status on performances was significant, the explained variance differed among tasks and between CA groups, and suggested a role for other factors affecting performances of the soccer players.