A lot of data and research show the benefits of regular physical activity for physical, social and mental health, and as a result the recommended frequency, intensity and duration of this activity has been established. However, in recent years there has been an alarming decrease in activity, especially among children and adolescents. Some authors argue that doing sport during childhood and adolescence may be a predictor for an active future lifestyle as it motivates the individual and helps create a habit. This paper is based on a number of theories about the determinants of physical activity behaviour as put forward by a number of authors. These theories include Prochaska and DiClemente (1983) and Prochaska, DiClemente and Norcross\u2019s (1992) stages of change model, Bandura\u2019s theory of self-efficacy (1986, 1999), Fishbein and Ajzen\u2019s theory of reasoned action (1975), Ajzen\u2019s theory of planned behaviour (1985, 1991), Taylor, Baranowsky and Sallis\u2019s social-cognitive model (1994) and Sallis\u2019s determinants model (1995). The determinants identified by these models include self-efficacy, a global attitude toward exercise, intentions, potential barriers to practice and the influence of \u201csignificant others\u201d. To meet these objectives this study was performed involving children aged between 10 and 12 in the third stage of primary education in state and grant-aided schools in the city of Ja\u00e9n.<\/p>\n\n