For the past years, there is enough data to display the important problem of inactivity among childhood and adolescence. When designing an intervention programme to increase physical activity levels, it is important to gather precise information about children physical activity levels as well as their determinants. For this purpose, a study has been designed to assess children physical activity levels for boys and girls, aged 10 to 13 of the Autonomic Community of Madrid. The conclusions of this study were: subjects of the study spend more than one and a half hour in physical activities. The percentage of subjects physically active varies according to the physical activity guideline considered, varying from only 20% when the more strict guideline was considered (minimum of one hour a day) to a 79,1% when considering the least strict guideline (minimum of half and hour at least 5 days a week). Finally, the time devoted by the individuals who do not fullfil the recommendations reveals that not performing the recommendations mainly has to do with the frequency of the practice but not with the length of it.<\/p>\n\n