Associations between prolonged sedentary time and breaks in sedentary time with cardiometabolic risk in 10-14-year-old children: The HAPPY study.

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.

The triglyceride to high-density lipoprotein ratio identifies children who may be at risk of developing cardiometabolic disease.

AIM: It is important to develop simple, reliable methods to identify high-risk individuals who may benefit from intervention. This study investigated the association between the triglyceride to high-density lipoprotein cholesterol (TG/HDL) ratio and cardiometabolic risk, cardiorespiratory fitness and physical activity in children. METHODS: Anthropometric, biochemical parameters, cardiorespiratory fitness and accelerometry determined physical activity were assessed in 155 children (80 girls) from 10 to 14 years of age from Bedfordshire, UK. Participants were grouped into high and low TG/HDL ratio groups, according to published thresholds. MANCOVA and logistic regression were used in the analysis. RESULTS: Cardiometabolic risk factor levels were significantly higher in participants with a high TG/HDL ratio (p < 0.05). The odds of having high waist circumference (OR = 13.99; 95% CI 2.93, 69.25), elevated systolic blood pressure (5.27; 1.39, 20.01), high non-HDL cholesterol (19.47; 4.42, 85.81) and ≥2 cardiometabolic risk factors (15.32; 3.10, 75.79) were higher in participants with a high TG/HDL ratio. The TG/HDL ratio values were significantly lower in those with high cardiorespiratory fitness (p = 0.01), but there was no association with physical activity. CONCLUSION: These findings support the use of the TG/HDL ratio to identify children with cardiometabolic risk factors who may be at risk of developing cardiometabolic disease.

The hypertriglyceridemic waist, waist-to-height ratio, and cardiometabolic risk.

OBJECTIVE: To investigate whether the hypertriglyceridemic waist (HW) phenotype and waist-to-height ratio (WHTR) are associated with cardiometabolic disorders in children and adolescents. STUDY DESIGN: This was a cross-sectional design study. Anthropometry, biochemical variables, and cardiorespiratory fitness were assessed in 234 participants (122 girls) aged 10-19 years from Bedfordshire, United Kingdom. The HW phenotype was defined as a waist circumference ≥90(th) percentile for age and sex, and triglyceride concentrations ≥1.24 mmol/L, and a high WHTR defined as >0.5. ANCOVA and logistic regression were used in the analysis. RESULT: In participants with the HW phenotype, the odds of having high cardiorespiratory fitness (mL/kg/min) were lower (0.045; 95% CI 0.01, 0.42), and the odds of having low high-density lipoprotein cholesterol (4.41; 1.50, 12.91), impaired fasting glucose (3.37; 1.06, 10.72), and ≥1 (4.78; 1.32, 17.29) and ≥2 risk factors (7.16; 2.38, 21.54) were higher than those without the phenotype. Those with a high WHTR had higher odds of having low high-density lipoprotein cholesterol (2.57; 1.11, 5.95), high diastolic blood pressure (3.21; 1.25, 8.25), and ≥2 risk factors (5.57; 2.05, 15.17) than those with normal WHTR. CONCLUSION: The HW phenotype may be a better simple marker than WHTR for identifying children and adolescents at risk for cardiometabolic disorders.

Associations between cardiorespiratory fitness, physical activity and clustered cardiometabolic risk in children and adolescents: the HAPPY study.

Clustering of cardiometabolic risk factors can occur during childhood and predisposes individuals to cardiometabolic disease. This study calculated clustered cardiometabolic risk in 100 children and adolescents aged 10-14 years (59 girls) and explored differences according to cardiorespiratory fitness (CRF) levels and time spent at different physical activity (PA) intensities. CRF was determined using a maximal cycle ergometer test, and PA was assessed using accelerometry. A cardiometabolic risk score was computed as the sum of the standardised scores for waist circumference, blood pressure, total cholesterol/high-density lipoprotein ratio, triglycerides and glucose. Differences in clustered cardiometabolic risk between fit and unfit participants, according to previously proposed health-related threshold values, and between tertiles for PA subcomponents were assessed using ANCOVA. Clustered risk was significantly lower (p < 0.001) in the fit group (mean 1.21 ± 3.42) compared to the unfit group (mean -0.74 ± 2.22), while no differences existed between tertiles for any subcomponent of PA. Conclusion These findings suggest that CRF may have an important cardioprotective role in children and adolescents and highlights the importance of promoting CRF in youth.

Accelerometry-assessed sedentary behaviour and physical activity levels during the segmented school day in 10-14-year-old children: the HAPPY study.

UNLABELLED: The school day offers several different time periods that provide varying opportunities for sedentary time (SED) and engagement in physical activity (PA), yet little is known about the PA and sedentary behaviour patterns of boys and girls during these times. The volume, intensity and temporal distributions of SED and PA undertaken by 135 schoolchildren aged 10-14 years, during different segments of the school day: (a) school transport, (b) morning recess, (c) lunch break, (d) class time and (e) after school, were explored using triaxial accelerometry. PA was categorised into SED, light PA (LPA), moderate PA (MPA) and vigorous PA (VPA). Girls engaged in significantly more SED and LPA than boys during recess and lunch break (p < 0.05), while boys engaged in significantly higher levels of VPA during recess (p < 0.001) and MPA and VPA during lunch break (p < 0.001). PA engagement was similar between sexes during other segments of the day. CONCLUSION: PA patterns appear more beneficial for health in boys during less structured school-based time periods and interventions may therefore target opportunities for girls to be physically active during these times to overcome this observed sex deficit.

The Association Between Cardiorespiratory Fitness and Cardiometabolic Risk in Children is Mediated by Abdominal Adiposity: The HAPPY Study.

BACKGROUND: It is unclear whether cardiorespiratory fitness (CRF) is independently linked to cardiometabolic risk in children. This study investigated a) the association between CRF level and presence of cardiometabolic risk disorders using health-related cut points, and b) whether these associations were mediated by abdominal adiposity in children. METHODS: This was a cross-sectional design study. Anthropometry, biochemical parameters and CRF were assessed in 147 schoolchildren (75 girls) aged 10 to 14 years. CRF was determined using a maximal cycle ergometer test. Children were classified as 'fit' or 'unfit' according to published thresholds. Logistic regression was used to investigate the odds of having individual and clustered cardiometabolic risk factors according to CRF level and whether abdominal adiposity mediated these associations. RESULTS: Children classified as unfit had increased odds of presenting individual and clustered cardiometabolic risk factors (P < .05), but these associations no longer remained after adjusting for abdominal adiposity (P > .05). CONCLUSIONS: This study suggests that the association between CRF and cardiometabolic risk is mediated by abdominal adiposity in 10- to 14-year-old children and that abdominal adiposity may be a more important determinant of adverse cardiometabolic health in this age group.

Choice of activity-intensity classification thresholds impacts upon accelerometer-assessed physical activity-health relationships in children.

BACKGROUND: It is unknown whether using different published thresholds (PTs) for classifying physical activity (PA) impacts upon activity-health relationships. This study explored whether relationships between PA (sedentary [SED], light PA [LPA], moderate PA [MPA], moderate-to-vigorous PA, vigorous PA [VPA]) and health markers differed in children when classified using three different PTs. METHODS: 104 children (63 girls) aged 10-14 years wore an RT3 triaxial accelerometer for seven days and measures of adiposity and cardiometabolic risk markers were taken. RESULTS: Significant associations (p< .05) in boys were found between LPA and body mass index z-score and waist circumference z-score for the Rowlands et al PT only (ß =  .459 and.401, respectively) and body fat% (BF%) for the Chu et al PT only (ß = .322) and in girls with BF% for the Rowlands et al PT only (ß =  .303) and systolic BP and blood glucose for the Vanhelst et al PT only (ß = -.298 and -.283, respectively). MPA was significantly (p<.05) associated with BF%, diastolic BP, and cardiorespiratory fitness (CRF) for the Chu et al PT only in girls (ß = -.436, -.529, and .446, respectively). SED was significantly (p<.05) associated with triglycerides (ß = .492) for the Rowlands et al PT only in boys and VPA with CRF (p<.05) for the Rowlands et al and Vanhelst et al PTs only in girls (ß = .416 and .352, respectively). CONCLUSIONS: The choice of PT impacted upon activity-health relationships. A consensus on appropriate accelerometer thresholds for quantifying PA intensity and sedentary behaviour is needed in order to make accurate evidence-based recommendations for health promotion.

cardiorespiratory fitness is associated with hard and light intensity physical activity but not time spent sedentary in 10-14 year old schoolchildren: the HAPPY study.

BACKGROUND: Sedentary behaviour is a major risk factor for developing chronic diseases and is associated with low cardiorespiratory fitness in adults. It remains unclear how sedentary behaviour and different physical activity subcomponents are related to cardiorespiratory fitness in children. The purpose of this study was to assess how sedentary behaviour and different physical activity subcomponents are associated with 10-14 year-old schoolchildren's cardiorespiratory fitness. METHODS: 135 schoolchildren (81 girls, 12±1 year) completed 7-day minute-by-minute habitual physical activity monitoring using triaxial accelerometers and undertook a maximal cardiorespiratory fitness test. RESULTS: After controlling for sex, age, ethnicity, socioeconomic status and total wear time, light physical activity (1.5-2.9 METs) was negatively associated (ß = -.24, p<.01) and hard physical activity (≥9 METs) positively associated (ß = .45, p<.001) with cardiorespiratory fitness. Vigorous and hard physical activity were associated with cardiorespiratory fitness for boys (F = 5.64, p<.01) whereas light, moderate and hard physical activity were associated with physical fitness for girls (F = 10.23, p<.001). No association was found between sedentary time and cardiorespiratory fitness (r = -.13, p>.05). Sedentary to active transitions revealed little variability between cardiorespiratory fitness tertiles. CONCLUSIONS: Hard physical activity (≥9 METs) holds greater potential for cardiorespiratory fitness compared to physical activity of lower intensities. There was no relationship between sedentary behaviour and cardiorespiratory fitness. These findings suggest that, for children, advice should focus on higher intensity physical activity and not sedentary behaviour as a means to maintain or improve cardiorespiratory fitness. Future research should explore longitudinal relationships between hard physical activity, cardiorespiratory fitness and health parameters.

Selenium supplementation and exercise: effect on oxidant stress in overweight adults.

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.