The aim of the present study was to determine the behaviour of the main factors of aerobic condition in young soccer players (15–18 years).

For this, we studied 79 subjects who belong to Albacete Balompié's young teams. These players passed two effort tests at least during the period (00/01–07/08).

We obtained data about the maximum oxygen intake (VO2max), maximum heart rate, maximum speed at the moment of VO2max and the percentage of VO2max when the anaerobic threshold happenes

Maximal oxygen intake like exponent of aerobic power doesn't experiment significant changes during ages 15 to 18.

Run's economy improves during puberty and stabilizes as of 17 years.

Maximal heart rate decrease during adolescence us 7–8 beat each 5 years.

There aren't differences between VO2max's percentages which 15–18 players experiment their anaerobic threshold.