Physical activity and bone health in schoolchildren: the mediating role of fitness and body fat

This is the final version of the article. Available from Public Library of Science via the DOI in this record.BACKGROUND: The relationship between physical activity (PA) and bone health is well known, although the role of percent body fat (%BF) and fitness as confounders or mediators in this relationship remains uncertain. OBJECTIVE: To examine whether the association between PA and bone mineral content (BMC) is mediated by %BF and cardiorespiratory fitness (CRF). METHODS: In this cross sectional study, BMC, total %BF (by DXA), vigorous PA (VPA), CRF, age and height were measured in 132 schoolchildren (62 boys, aged 8-11 years). ANCOVA was used to test differences in BMC by %BF, CRF and VPA, controlling for different sets of confounders. Simple mediation analyses and serial multiple mediation analyses were fitted to examine whether the relationship between PA and BMC is mediated by %BF and fitness. RESULTS: Children with high %BF had higher total body BMC than their peers after controlling for all sets of confounders. Children with good CRF or VPA had significantly less total body BMC after controlling for age and sex but in children with good CRF this inverse relation disappeared after adjusting by %BF. %BF and CRF both act as a full mediator in the association between VPA and BMC, after inclusion of the potential confounders in the models. CONCLUSION: Fitness and %BF seem to have a mediator role on the relationship between physical activity and bone mass.This study was funded by grant numbers PII1I09-0259-9898 and POII10-0208-5325 from the Ministry of Education and Science - Junta de Comunidades de Castilla-La Mancha, and Ministry of Health (FIS grant number PI081297). Additional funding was provided by the Research Network on Preventative Activities and Health Promotion (RD06/0018/0038)

Agreement between dual-energy X-ray absorptiometry and quantitative ultrasound to evaluate bone health in adolescents: The PRO-BONE study

Purpose: The present study aims to investigate the association between dual-energy X-ray absorptiometry (DXA) and quantitative ultrasound (QUS) parameters and the intermethods agreement in active males. Methods: In this cross-sectional study, bone health (by DXA and calcaneal QUS), physical activity (by accelerometers), and anthropometrics measurements were assessed in 117 active adolescents (12–14 y old). Bivariate correlation coefficients were calculated to assess the relationships between DXA standard regions of interest and QUS parameters. Intraclass correlation coefficients and Bland–Altman plots were used to assess the level of agreement between bone mineral content regions derived from DXA and stiffness index. The measurements were z score transformed for comparison. Results: Most QUS parameters were positive and significantly correlated with DXA outcomes (stiffness index: r = .43–.52; broadband ultrasound attenuation: r = .50–.58; speed of sound: r = .25–.27) with the hip showing the highest correlations. Moreover, the present study found fair to good intraclass correlation coefficients of agreement (.60–.68) between DXA and QUS to assess bone health. The Bland–Altman analysis showed a limited percentage of outliers (3.2%–8.6%). Conclusion: QUS device could represent an acceptable alternative method to assess bone health in active adolescent males

Lean mass explains the association between muscular fitness and bone outcomes in 13-year-old boys

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record AIM: This study investigated the associations between fitness indices and bone outcomes in young males. METHODS: Data were collected between autumn and winter 2014-2015 on 121 males with a mean age of 13.1 ± 0.1 years: 41 swimmers, 37 footballers, 29 cyclists and 14 nonathletes. Participants were recruited from athletic clubs and schools across South West England. Lean mass, areal bone mineral density and hip structural estimates were measured using dual-energy X-ray absorptiometry. The relationships between bone outcomes and the vertical jump, standing long jump and the 20-m shuttle run test were analysed using three regression models: model 1 was adjusted by age and stature, model 2 added vigorous physical activity and model 3 then added lean mass. RESULTS: The boys' performance in the vertical jump and standing long jump was positively associated with the majority of bone outcomes in models 1 and 2, but most of these disappeared in model 3. The 20-m shuttle run test was positively associated with most bone outcomes in all three models. Lean mass played a key role in the association between muscular fitness and bone outcomes. CONCLUSION: Vigorous physical activity did not explain the associations between fitness and bone outcomes, but lean mass did.European Union Seventh Framework Programme (FP7/2007–2013

Agreement Between Standard Body Composition Methods to Estimate Percentage of Body Fat in Young Male Athletes.

This is author's accepted manuscript.Final version available from Human Kinetics via the DOI in this record.PURPOSE: To examine the intermethods agreement of dual-energy X-ray absorptiometry (DXA) and foot-to-foot bioelectrical impedance analysis (BIA) to assess the percentage of body fat (%BF) in young male athletes using air-displacement plethysmography (ADP) as the reference method. METHODS: Standard measurement protocols were carried out in 104 athletes (40 swimmers, 37 footballers, and 27 cyclists, aged 12-14 y). RESULTS: Age-adjusted %BF ADP and %BF BIA were significantly higher in swimmers than footballers. ADP correlates better with DXA than with BIA (r = .84 vs r = .60, P < .001). %BF was lower when measured by DXA and BIA than ADP (P < .001), and the bias was higher when comparing ADP versus BIA than ADP versus DXA. The intraclass correlation coefficients between DXA and ADP showed a good to excellent agreement (r = .67-.79), though it was poor when BIA was compared with ADP (r = .26-.49). The ranges of agreement were wider when comparing BIA with ADP than DXA with ADP. CONCLUSION: DXA and BIA seem to underestimate %BF in young male athletes compared with ADP. Furthermore, the bias significantly increases with %BF in the BIA measurements. At the individual level, BIA and DXA do not seem to predict %BF precisely compared with ADP in young athletic populations.This work was done as part of the PRO-BONE study. It has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. PCIG13-GA-2013-618496. M.V.N-F. received a PhD Student Internships Abroad scholarship from the National Council for Scientific and Technological Development (CNPq; process: 200340/2015-8) and a Brazilian PhD Student scholarship from the São Paulo Research Foundation (FAPESP; process. 2016/18436-8 and 2017/11732-3). E.U-G. received a PhD scholarship from Universidad de Castilla-La Mancha (2014/10340). A.C.F.M. received a postdoctoral scholarship from the São Paulo Research Foundation (FAPESP; process: 2014/13367-2 and 2015/14319-4)

Lean mass explains the association between muscular fitness and bone outcomes in 13-year-old boys

Aim: This study investigated the associations between fitness indices and bone outcomes in young males. Methods: Data were collected between autumn and winter 2014–2015 on 121 males with a mean age of 13.1 ± 0.1 years: 41 swimmers, 37 footballers, 29 cyclists and 14 nonathletes. Participants were recruited from athletic clubs and schools across South West England. Lean mass, areal bone mineral density and hip structural estimates were measured using dual-energy X-ray absorptiometry. The relationships between bone outcomes and the vertical jump, standing long jump and the 20-m shuttle run test were analysed using three regression models: model 1 was adjusted by age and stature, model 2 added vigorous physical activity and model 3 then added lean mass. Results: The boys’ performance in the vertical jump and standing long jump was positively associated with the majority of bone outcomes in models 1 and 2, but most of these disappeared in model 3. The 20-m shuttle run test was positively associated with most bone outcomes in all three models. Lean mass played a key role in the association between muscular fitness and bone outcomes. Conclusion: Vigorous physical activity did not explain the associations between fitness and bone outcomes, but lean mass did.Sin financiación2.580 JCR (2017) Q1, 28/124 PediatricsUE