9The school day offers several different time periods that provide varying opportunities for sedentary time (SED) 10 and engagement in physical activity (PA), yet little is known about the PA and sedentary behaviour patterns of 11 boys and girls during these times. The volume, intensity and temporal distribution of SED and PA undertaken 12 by 135 schoolchildren aged 10-14 years, during different segments of the school day: a) school transport, b) 13 morning recess, c) lunch break, d) class time, and e) after school, was explored using tri-axial accelerometry. PA 17PA engagement was similar between sexes during other segments of the day. Conclusion PA patterns appear 18 more beneficial for health in boys during less structured school-based time periods and interventions may 19 therefore target opportunities for girls to be physically active during these times to overcome this observed sex 20 deficit. 22 Keywords 23Children; adolescents; physical activity; sedentary behaviour; accelerometry 24 25

8Clustering of cardiometabolic risk factors can occur during childhood and predisposes individuals to 9 cardiometabolic disease. This study calculated clustered cardiometabolic risk in 100 children and adolescents 10 aged 10-14 years (59 girls) and explored differences according to cardiorespiratory fitness (CRF) levels and 11 time spent at different physical activity (PA) intensities. CRF was determined using a maximal cycle ergometer 12 test and PA was assessed using accelerometry. A cardiometabolic risk score was computed as the sum of the 13 standardised scores for waist circumference, blood pressure, total cholesterol:HDL ratio, triglycerides, and

This study examines the association between prolonged sedentary time and breaks in sedentary time with cardiometabolic risk in 10-14-year-old children. This cross-sectional design study analysed accelerometry-determined sedentary behaviour and physical activity collected over 7 days from 111 (66 girls) UK schoolchildren. Objective outcome measures included waist circumference, fasting lipids, fasting glucose, blood pressure, and cardiorespiratory fitness. Logistic regression was used for the main data analysis. After adjustment for confounders, the odds of having hypertriglyceridaemia (P = 0.03) and an increased clustered cardiometabolic risk score (P = 0.05) were significantly higher in children who engaged in more prolonged sedentary bouts per day. The number of breaks in sedentary time per day was not associated with any cardiometabolic risk factor, but longer mean duration of daily breaks in sedentary time were associated with a lower odds of having abdominal adiposity (P = 0.04) and elevated diastolic blood pressure (P = 0.01). These associations may be mediated by engagement in light activity. This study provides evidence that avoiding periods of prolonged uninterrupted sedentary time may be important for reducing cardiometabolic disease risk in children.

30Objective Hypertriglyceridaemic waist (HW) and waist-to-height ratio (WHTR)

Both obesity and acute high-intensity exercise increase oxidant stress levels. This study investigates whether selenium (Se) supplementation could be a potential effective therapy to reduce obesity-associated oxidant stress and exercise-induced oxidant stress. Ten normal-weight (NW) (22.80 ± 0.41 kg/m 2 ) and ten overweight (OW) healthy subjects (28.00 ± 0.81 kg/m 2 ) were assessed during a randomized double-blind Se supplementation study (200 μg sodium selenite/day for 3 weeks) with a 3-week placebo control and inversion of treatment periods. Blood levels of lipid hydroperoxide (LH), superoxide dismutase (SOD), erythrocyte glutathione (GSH), and total antioxidant status (TAS), were measured at rest, pre-, and postexercise (30 min 70% VO 2 max before and after treatment (pretreatment (week 0 and 12) and post-treatment (week 3 or 15)). At rest, compared to placebo, Se supplementation had no significant effect on LH, SOD, GSH, and TAS levels. However, Se supplementation decreased LH levels in the OW group, immediately postexercise (−0.25 ± 0.12 μmol/l, P = 0.05) compared to placebo treatment. Postexercise, with or without Se supplementation, no changes in TAS, SOD, and GSH levels were observed in both the NW and OW group. This study has highlighted a potential benefit of Se in reducing LH levels postexercise in OW individuals. Given that oxidant stress is a predictor of coronary events, it is imperative to better understand oxidant stress-related responses to lifestyle factors (in particular "high-risk" population groups) and potential antioxidant therapy.