Social Science & Medicine 56 (2003) 363–374 Gender differences in physical activity in older children and adolescents: the central role of organized sport Runar Vilhjalmsson*, Gudrun Kristjansdottir Faculty of Nursing, University of Iceland, Eiriksgotu 34, Eirbergi, IS-101 Reykjavik, Iceland Abstract Previous studies have generally had limited success in accounting for gender differences in leisure time physical activity. Based on a representative national survey of 3270 Icelandic 6th, 8th and 10th grade students, the study found that girls’ lower enrollment in organized sport clubs fully accounts for gender differences in frequency of overall physical activity, and largely accounts for gender differences in frequency of strenuous activity, and weekly hours of overall and strenuous activity (enrollment hypothesis). Furthermore, girls’ higher sport club withdrawal rate accounted for a small but significant part of the gender difference in weekly hours of overall activity and frequency of strenuous activity (withdrawal hypothesis). No evidence was found to suggest that different activity levels of boys and girls enrolled in the clubs affected gender differences in levels of overall or strenuous physical activity (activity differential hypothesis). Other independent variables, i.e., perceived importance of sport achievement, sport and exercise related instruction, physical education experiences, and social modeling, did not significantly affect observed gender differences beyond the sport club variables. The meaning of the results, and their implications for gender disparities, health promotion, and future research are discussed. r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Sport participation; Physical activity; Exercise; Gender; Iceland Introduction Sport and exercise is a vast enterprise involving major social institutions and large numbers of participants, workers and consumers. Its wide ranging implications have resulted in numerous studies suggesting that active involvement in sport and exercise has beneficial effects relating to psychological well-being (Biddle, 1993; Vilhjalmsson & Thorlindsson, 1992), self esteem and sense of control (Gill, 1986; Gilroy, 1989; Gruber, 1986), physical fitness (Dotson & Ross, 1985; Hagberg, 1990; Tell & Vellar, 1988; Thorland & Gilliam, 1985), lowered risk of negative health behaviors, such as smoking and alcohol use (Escobedo, Marcus, Holtzman, & Giovino, 1993; Hastad, Segrave, Pangrasi, & Peterson, 1984; Thorlindsson & Vilhjalmsson, 1991), and longevity (Paffenbarger, Hyde, Wing, & Hsieh, 1986). Despite the reported benefits of sport and exercise, scientists and educators repeatedly report that many young people are physically inactive (Armstrong, Bald- ing, Gentle, & Kirby, 1990; Heath, Pratt, Warren, & Kann, 1994), although the reasons for their inactivity are not well understood (Biddle & Armstrong, 1992; Coakley & White, 1992). One of the most persistent findings in the literature concerns the disadvantaged status of girls (Armstrong et al., 1990; Fuchs et al., 1988; Guinn, Vincent, Semper, & Jorgensen, 2000; Tell & Vellar, 1988). Their lower activity levels, especially in late childhood and adolescence, extend across numerous sports and forms of physical involvement (Faucette et al., 1995; Sallis, Zakarian, Hovell, & Hofstetter 1996; Vilhjalmsson & Thorlindsson, 1992). However, gender differences are greatest in strenuous sports and activity forms (Fuchs et al., 1988; Ross & Gilbert, 1985). Socialization and attitudes Most investigators of gender differences in physical activity have focused on socialization into sport or *Corresponding author. Tel.: +354-525-4960; fax: +354- 525-4963. E-mail address: runarv@hi.is (R. Vilhjalmsson). 0277-9536/02/$-see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII:S0277-9536(02)00042-4