Tracking of physical fitness during adolescence: a panel study in boys

Purpose: To investigate the tracking in physical fitness (PF) viewed as a w hole, a multidimensional trait of the subject, and to establish the stabili ty of each factor of PF in adolescence from the perspective of a panel stud y using the structural equation modeling approach. Methods: From a sample o f 454 boys followed from 12 to 18 yr of age of the Leuven Growth Study, we considered only three consecutive measurement occasions with a mean age of 12.76, 14.69. and 17.73 yr. Physical fitness was evaluated by means of a ba ttery composed of the following tests: plate tapping, sit and reach, vertic al jump, arm pull, leg lifts, bent arm hang, and shuttle run. Structural eq uation models were fitted to the data, namely autoregressive models with la tent variables. These models were used to quantify the tracking of PF as a whole and also of the individual marker variables of fitness. Results: Stab ility estimates of PF as a whole are rather high, beta (21) = 0.86 and beta (32) = 0.68, with an explained variance of 74% and 73%, respectively. Trac king coefficients represented by disattenuated autocorrelations among the f itness factor gave high results: r(1,2) = 0.861 r(1,3) = 0.78: and r(2,3) = 0.85. Conclusions: Physical fitness as a whole is highly stable in adolesc ent years and very predictable from early years. The same is observed for e ach factor of fitness. Moreover, autoregressive models within the context o f structural equation modeling are better suited than simple Pearson or Spe arman autocorrelations to study the tracking problem of PF.