Physical activity is associated with increased risk of a wide variety of diseases such as cardiovascular, hypertension, type 2 diabetes, obesity, and depression (U.S. Department of Health and Human Services, 1996). It has been noted that these diseases seldom manifest themselves before adulthood. However, promotion of physical activity may be important since inactivity may also predispose individuals to a future sedentary lifestyle which leads to an increase risk for these diseases (Rowland, 1990).
It is known that physical activity has positive effects on the physiological and psychological well-being of children and adolescents, and believed to be important to the development and maintenance of health-related behavior patterns that will carry over into adulthood (Anderssen & Wold, 1992). The benefits of being physically active are also thought to extend to psychological and sociological realms. Sport and exercise participation is often linked with such characteristics as attitudes and self-perceptions (Asci, 2003; Asci, Kosar, & Kin-Isler, 2001) and with social interpersonal patterns (Sallis, Prochaska, & Taylor, 2000).
Descriptive epidemiological studies of physical activity have consistently indicated that physical activity declines with age. It has been reported that physical activity is inversely associated with age in studies of children (Sallis, Prochaska, & Taylor, 2000; Trost, Pate, Sallis, Freedson, Taylor, Dowda, & Sirard, 2002) adolescents (Caspersen, Pereira, & Curran, 2000; Trost et al., 2002), and in adults (Caspersen et al., 2000; Telema & Yang, 2000). In addition, cross-sectional and longitudinal studies of habitual physical activity during childhood and adolescence confirm the subjective impression that regular exercise diminishes with age. For instance, in a longitudinal study by Telama and Yang (2000) that investigated the decline in physical activity between the ages of 9 to 27 in Finland, a remarkable decline in physical activity level was observed after the age of 12. In a cross-sectional study by Caspersen, Pereira, and Curran (2000) it was found that physical activity patterns eroded most from ages 15 through 18, and regular vigorous activity declined consistently from age 12 in the United States. Similarly Trost and colleagues (2002) reported a significant inverse relationship with age and daily moderate and vigorous physical activity level in students through grade twelve.
Research also indicates higher physical activity of males as compared to females. Most of the published data from different countries reported that boys are more active than girls (Caspersen et al., 2000; Telama & Yang, 2000; Riddoch, Andersen, Wedderkopp, Harro, Klasson-Heggebo, Sardinha, Cooper, & Ekelund, 2004; Van Mechelen, Twisk, Post, Snel, & Kemper, 2000). One of the reasons for this gender difference may be that there are fewer opportunities for girls to participate in sports or regular exercise (Wells, 1991). In addition it has been indicated that regular participation in sports and exercise are behaviors that are heavily influenced by observation of others who model these behaviors and by social reinforcement (Bandura, 1977; Godin & Shephard, 1986). Physically active role modeling by parents and parental support and encouragement for physical activity are consistent correlates of children's physical activity (U. S. Department of Health and Human Services, 1996; Sallis et al. 2000). Until recently women were far less likely to participate in sports and exercise.
Despite these gender differences, differences in the age-related decline in physical activity among adolescents are controversial. For example, Sallis (1993) reported that the rate of decline in physical activity is greater for girls. In contrast, recent studies (Caspersen et al., 2000; Telama & Yang, 2000; Van Mechelen et al., 2000) indicate that …