Physical activity guidelines and cardiovascular risk in children: a cross sectional analysis to determine whether 60 minutes is enough.

BACKGROUND: Physical activity reduces cardiovascular mortality and morbidity. The World Health Organisation (WHO) recommends children engage in 60 min daily moderate-to-vigorous physical activity (MVPA). The effect of compliance with this recommendation on childhood cardiovascular risk has not been empirically tested. To evaluate whether achieving recommendations results in reduced composite-cardiovascular risk score (CCVR) in children, and to examine if vigorous PA (VPA) has independent risk-reduction effects. METHODS: PA was measured using accelerometry in 182 children (9-11 years). Subjects were grouped according to achievement of 60 min daily MVPA (active) or not (inactive). CCVR was calculated (sum of z-scores: DXA body fat %, blood pressure, VO2peak, flow mediated dilation, left ventricular diastolic function; CVR score ≥ 1SD indicated 'higher risk'). The cohort was further split into quintiles for VPA and odds ratios (OR) calculated for each quintile. RESULTS: Active children (92 (53 boys)) undertook more MVPA (38 ± 11 min, P < 0.001), had greater VO2peak (4.5 ± 0.8 ml/kg/min P < 0.001), and lower fat % (3.9 ± 1.1 %, P < 0.001) than inactive. No difference were observed between active and inactive for CCVR or OR (P > 0.05). CCVR in the lowest VPA quintile was significantly greater than the highest quintile (3.9 ± 0.6, P < 0.05), and the OR was 4.7 times higher. CONCLUSION: Achievement of current guidelines has positive effects on body composition and cardiorespiratory fitness, but not CCVR. Vigorous physical activity appears to have beneficial effects on CVD risk, independent of moderate PA, implying a more prescriptive approach may be needed for future VPA guidelines.

The effect of a 9-week physical activity programme on bone and body composition of children aged 10-11 years: an exploratory trial.

A high-impact exercise and a lifestyle intervention were implemented over a 9-week period; changes in bone and body composition were compared to controls. Sixty-one children volunteered from three randomly selected schools. Each school was randomly assigned to either a structured exercise (STEX) intervention, a lifestyle intervention (PASS) or control (CONT). Bone mineral content (BMC) and density (BMD) of total body, femoral neck and lumbar spine were measured as well as fat and lean mass at baseline and post-intervention by dual-energy X-ray absorptiometry. The STEX intervention resulted in an additional mean increase in total body BMC of 63.3 g (p = 0.019) and an additional increase of 0.011 g . cm (-2) (p = 0.018) for BMD over increases observed by controls. Bone mineral increases observed for the PASS intervention were not significant compared to the control group (p > 0.05). Neither intervention produced significant increases in bone mineral at femoral neck or lumbar spine sites (p > 0.05) compared with the controls. No significant changes were found in fat mass index (p > 0.05), lean mass index (p > 0.05) or percent body fat (p = 0.09) in any groups. Structured impact exercise promoted significant and clinically relevant increases in bone measures, without significant changes to body composition. A larger, definitive randomised trial is needed to confirm the present results.