Alves, F., Santinha, F., Viera, F., & Fragoso, I. (2006). Running economy in 9 to 17 years-old soccer players. Medicine and Science in Sports and Exercise, 38(5), Supplement abstract 1497.

This study investigated the influence of treadmill gradient and velocity on the relationship between maturation and running economy. It was hypothesized that a smaller increase in the oxygen uptake with increasing slope in younger children would indicate that they are less economical because of body dimensions. Soccer players (N = 40; 9-17 years-old) served as Ss. Standard anthropometric measurements as well as skeletal age (SkA), based on radiographs of the hand and wrist bones according to Tanner-Whitehouse III Method (TW3) were assessed. Running economy was evaluated during a submaximal test protocol with three 6-minute workloads with fixed velocity and gradient: the first at 8 km/h and 0% (EC8/0), the second at 9.5 km/h and 0% (EC9.5/0), and the third at 8 km/h and 5% (EC8/5). After cluster analysis, Ss were divided in three groups with the SkA as criterion: Group 1 <12 years; Group 2 >12 <14 years; and Group 3 >14 years.

VO2 uptake consistently decreased with body mass increment for the three submaximal workloads but was not related to skeletal age in any situation. Standard ratio VO2 values were negatively correlated to body mass for all workloads but were not significantly different among groups at any workload. Percent differences in VO2 were correlated in the whole sample but were not significantly different from each other nor did they vary between skeletal-age based groups.

Implication. Within a group of young soccer players, submaximal VO2 responses were explained predominantly by changes in body mass, with no additional maturity-related effects. Moreover, the variation in oxygen uptake because of increased workload either by velocity or slope increases independently of maturation.

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