Daily physical activity and physical fitness from adolescence to adulthood: a longitudinal study. - Lefevre,J.; Philippaerts,R.M.; Delvaux,K.; Thomis,M.; Vanreusel,B.; Vanden Eynde,B.; Claessens,A.L.; Lysens,R.; Renson,R.; Beunen,G. (Am J Hum Biol, 2000)