Relationships between measures of fitness, physical activity, body composition and vascular function in children

Background : The prevalence of obesity and physical inactivity in Western countries has increased rapidly. Both are modifiable risk factors for cardiovascular disease. Atherosclerosis begins in childhood and endothelial dysfunction is its earliest detectable manifestation.

Methods : We assessed flow-mediated dilation (FMD) in 129 children (75 female; 10.3 + 0.3 yrs; 54 male; 10.4; 0.3 yrs). FMD was normalised for differences in the eliciting shear rate stimulus between subjects (SR_AUC). Fitness was assessed as peak oxygen uptake during an incremental treadmill exercise test (VO₂peak). Body composition was measured using a dual-energy X-ray absorptiometry (DEXA) scan. Physical activity (PA) was assessed using Actigraph accelerometers. The cohort was split into tertiles according to FMD% and also FMD% corrected for SR_AUC to gain insight into the determinants of vascular function.

Results : Across the cohort, significant correlations were observed between FMD%/SR_AUC and DEXA percentage fat (r = −0.23, p = 0.009) and percentage lean mass (r = 0.21, p = 0.008), and also with PA performed at moderate-to-high intensity (r = 0.363, p = 0.001). For children in the lowest FMD%/SR_AUC tertile, a stronger relationship with all PA measures was observed, particularly with high intensity PA (r = 0.572, P = 0.003). Regression analysis revealed that high intensity PA was the only predictor of impaired FMD%/SR_AUC.

Conclusions : These data suggest that traditional risk factors for CHD in adult populations impact upon vascular function in young people. Furthermore, it appears that individuals with impaired FMD may benefit from performing high intensity PA, whereas no relationships exist between FMD and lower intensities of PA or between PA and FMD in those subjects who possess preserved vascular function a priori.

A simple-to-use calculator for determining the total solar heat gain of a glazing system

Architects and designers could readily use a quick and easy tool to determine the solar heat gains of their selected glazing systems for particular orientations, tilts and climate data. Speedy results under variable solar angles and degree of irradiance would be welcomed by most. Furthermore, a newly proposed program should utilise the outputs of existing glazing tools and their standard information, such as the use of U-values and Solar Heat Gain Coefficients (SHGC’s) as generated for numerous glazing configurations by the well-known program WINDOW 6.0 (LBNL, 2001). The results of this tool provide interior glass surface temperature and transmitted solar radiation which link into comfort analysis inputs required by the ASHRAE Thermal Comfort Tool –V2 (ASHRAE, 2011). This tool is a simple-to-use calculator providing the total solar heat gain of a glazing system exposed to various angles of solar incidence. Given basic climate (solar) data, as well as the orientation of the glazing under consideration the solar heat gain can be calculated. The calculation incorporates the Solar Heat Gain Coefficient function produced for the glazing system under various angles of solar incidence WINDOW 6.0 (LBNL, 2001). The significance of this work rests in providing an orientation-based heat transfer calculator through an easy-to-use tool (using Microsoft EXCEL) for user inputs of climate and Solar Heat Gain Coefficient (WINDOW-6) data. We address the factors to be considered such as solar position and the incident angles to the horizontal and the window surface, and the fact that the solar heat gain coefficient is a function of the angle of incidence. We also discuss the effect of the diffuse components of radiation from the sky and those from ground surface reflection, which require refinement of the calculation methods. The calculator is implemented in an Excel workbook allowing the user to input a dataset and immediately produce the resulting solar gain. We compare this calculated total solar heat gain with measurements from a test facility described elsewhere in this conference (Luther et.al., 2012).

Dietary creatine supplementation during pregnancy: a study on the effects of creatine supplementation on creatine homeostasis and renal excretory function in spiny mice

Recent evidence obtained from a rodent model of birth asphyxia shows that supplementation of the maternal diet with creatine during pregnancy protects the neonate from multi-organ damage. However, the effect of increasing creatine intake on creatine homeostasis and biosynthesis in females, particularly during pregnancy, is unknown. This study assessed the impact of creatine supplementation on creatine homeostasis, body composition, capacity for de novo creatine synthesis and renal excretory function in non-pregnant and pregnant spiny mice. Mid-gestation pregnant and virgin spiny mice were fed normal chow or chow supplemented with 5 % w/w creatine for 18 days. Weight gain, urinary creatine and electrolyte excretion were assessed during supplementation. At post mortem, body composition was assessed by Dual-energy X-ray absorptiometry, or tissues were collected to assess creatine content and mRNA expression of the creatine synthesising enzymes arginine:glycine amidinotransferase (AGAT) and guanidinoacetate methyltransferase (GAMT) and the creatine transporter (CrT1). Protein expression of AGAT and GAMT was also assessed by Western blot. Key findings of this study include no changes in body weight or composition with creatine supplementation; increased urinary creatine excretion in supplemented spiny mice, with increased sodium (P < 0.001) and chloride (P < 0.05) excretion in pregnant dams after 3 days of supplementation; lowered renal AGAT mRNA (P < 0.001) and protein (P < 0.001) expressions, and lowered CrT1 mRNA expression in the kidney (P < 0.01) and brain (P < 0.001). Creatine supplementation had minimal impact on creatine homeostasis in either non-pregnant or pregnant spiny mice. Increasing maternal dietary creatine consumption could be a useful treatment for birth asphyxia.