The effect of aerobic exercise training on the lipid-lipoprotein profile of children and adolescents

Longitudinal paediatric population studies have provided evidence that the risk factor theory may be extended to children and adolescents. These studi es could assist in identifying individuals at increased coronary risk. Nume rous stud ies have focused on the effects of regular exercise on the paedia tric lipoprotein profile, a recognised primary risk factor, with equivocal results. Cross-sectional comparisons of dichotomised groups provide the str ongest evidence of an exercise effect. 'Trained' or 'active' children and a dolescents demonstrate 'favourable' levels of high density lipoprotein-chol esterol (HDL-C), triacylglycerol, total cholesterol (TC)/HDL-C and low dens ity lipoprotein-cholesterol (LDL-C)/HDL-C, whilst TC is generally unaffecte d. The evidence regarding LDL-C in these studies is equivocal. A possible s elf-selection bias means that a cause-effect relationship between exercise and the lipoprotein profile cannot be readily established from this design. Correlational studies are difficult to interpret because of differences in participant characteristics, methods employed to assess peak oxygen uptake and habitual physical activity (HPA), and the statistical techniques used to analyse multivariate data. Directly measured cardiorespiratory fitness d oes not appear to be related to lipoprotein profiles in the children and ad olescents studied to date, although there are data to the contrary. The rel ationship with HPA is more difficult to decipher. The evidence suggests tha t a 'favourable' lipoprotein profile may be related to higher levels of HPA , although differences in assessment methods preclude a definitive answer. While few prospective studies exist, the majority of these longitudinal inv estigations suggest that imposed regular exercise has little, if any, influ ence on the lipoprotein levels of children and adolescents. However, most p rospective studies have several serious methodological design weaknesses, i ncluding low sample size, inadequate exercise training volume and a lack of control individuals. Recent studies have suggested that increases in HDL-C and rejections in LDL-C may be possible with regular exercise. The identif ication of a dose-response relationship between exercise training and the l ipoprotein profile during the paediatric years remains elusive.