1. Armstrong, N. and Van Mechelen, W. (1998). How fit and active are children and youth? In Young and Active? (edited by S. Biddle, N. Cavill and J. Sallis), pp. 69-97. London: Health Education Authority.
2. Armstrong, N. and Welsman, J.R. (1997). Young People and Physical Activity. Oxford: Oxford University Press.
3. Atkins, S., Stratton, G., Dugdill, L. and Reilly, T. (1997). The free living physical activity of schoolchildren: A longitudinal study. In Children and Exercise XIX: Promoting Health and Well-B eing (edited by N. Armstrong, B.J. Kirby and J.R. Welsman), pp. 145-150. London: E & FN Spon.
4. Bar-Or, O. (1983). Pediatric Sports M edicine for the Practitioner. New York: Springer-Verlag.