Catherine J. Kerr

Oxidant Stress in Healthy Normal-weight, Overweight, and Obese Individuals

This study was undertaken to investigate the association among BMI and lipid hydroperoxide (LH), total antioxidant status (TAS), superoxide dismutase (SOD), and reduced glutathione (GSH). Ninety (n = 90) healthy males and females (n = 23/67) (29 normal weight (BMI: 22.74 ± 0.25 kg/m2), 36 overweight (BMI: 27.18 ± 0.23 kg/m2), and 25 obese (33.78 ± 0.48 kg/m2)) participated in the study. Data collected included anthropometric measures, fasting blood glucose, lipid profile, LH, TAS, and enzymatic antioxidants (SOD, and reduced GSH). The results of the study showed that obese individuals had significantly increased LH levels compared to normal‐weight individuals (obese vs. normal weight (0.88 ± 0.05 vs. 0.67 ± 0.03 µmol/l, P < 0.01)) but the increased levels were not significantly different when compared to the overweight group (obese vs. overweight (0.88 ± 0.05 vs. 0.79 ± 0.05 µmol/l)). No other consistent significant differences in TAS, SOD, and GSH were identified between groups. This study concluded that only obesity and not moderate overweight elevates LH levels. Furthermore, the levels of TAS, SOD, and GSH in obesity do not explain the increased LH levels observed in obesity.

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 schoolchildrens 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 (β = −.24, p<.01) and hard physical activity (≥9 METs) positively associated (β = .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.

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.

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/m2) and ten overweight (OW) healthy subjects (28.00 ± 0.81 kg/m2) 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% VO2 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.

Physical activity levels and motivational responses of boys and girls: A comparison of direct instruction and tactical games models of games teaching in physical education

The purpose of this study was to independently determine the levels of moderate-to-vigorous physical activity (MVPA) and self-determined motivation of both boys and girls as they participated in prolonged units of invasion games (i.e. 6–12 lessons) through two pedagogical models: direct instruction and the tactical games model (TGM). It was hypothesized that given the differences in domain interaction and lesson structure, both boys and girls would gain higher levels of physical activity (PA) and possess higher quality motivation during TGM-based lessons when compared to direct instruction lessons. Seventy-two children aged 11–12 years (42 boys, 30 girls) were randomly assigned to either a control or intervention group (TGM). Children wore RT3® triaxial accelerometers over a 12 week period to objectively measure time spent in MVPA. The System for Observing Fitness Instruction Time (SOFIT) tool was completed during each lesson to additionally assess lesson context information and teacher behaviour. SDT questionnaires were also completed, pre and post-intervention. Boys in the TGM condition displayed significantly higher levels of MVPA in both rugby and football activities in comparison to the control group although no significant differences in motivation were noted post-intervention. While girls in the TGM condition recorded comparable PA levels in the football sessions, they recorded significantly lower PA activity levels in the netball lessons. There were no significant differences in girls’ motivation post-intervention. It is recommended that future studies build on this research by continuing to examine PA and the quality of student motivation while using GCAs over prolonged unit lengths (i.e. greater than 12 lessons) using structural equation modelling techniques to assess the relationships between, and mediating influences of, SDT constructs on PA levels.

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 (β =  .459 and.401, respectively) and body fat% (BF%) for the Chu et al PT only (β = .322) and in girls with BF% for the Rowlands et al PT only (β =  .303) and systolic BP and blood glucose for the Vanhelst et al PT only (β = −.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 (β = −.436, −.529, and .446, respectively). SED was significantly (p<.05) associated with triglycerides (β = .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 (β = .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.

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

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.

Physical education contributes to total physical activity levels and predominantly in higher intensity physical activity categories

Children’s engagement in physical activity of a vigorous intensity or higher is more effective at promoting cardiorespiratory fitness than moderate physical activity. It remains unclear how higher intensity physical activity varies between days when schoolchildren participate in physical education (PE) and non-PE days. The purpose of this study was to assess how PE contributes to sedentary behaviour and the intensity profile of physical activity accumulated on PE days compared to non-PE days. Fifty-three schoolchildren (36 girls, 11.7 ± 0.3 years) completed five-day minute-by-minute habitual physical activity monitoring using triaxial accelerometers to determine time spent sedentary (<1.5 Metabolic Equivalent of Tasks (METs)) and in light (1.5–2.9 METs), moderate (3–5.9 METs), vigorous (6–8.9 METs), hard (9–11.9 METs) and very hard intensity (≥12 METs) physical activity on PE days and non-PE days. Sedentary time was higher on non-PE days than on PE days (mean difference: 62 minutes, p < 0.001). Hard and very hard intensity physical activity was significantly higher on PE days compared with non-PE days (mean total difference: 33 minutes, all significant at p < 0.001). During the PE lesson, boys spent more time in hard (p < 0.01) and very hard (p < 0.01) physical activity compared to girls. Schoolchildren spent significantly more time in higher intensity physical activity and significantly less time sedentary on PE days than on non-PE days. As well as reducing sedentary behaviour, the opportunity to promote such health-promoting higher intensity physical activity in the school setting warrants further investigation.

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

ABSTRACT 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.

Dietary glycaemic index and glycaemic load in relation to body mass index, body composition and waist circumference in post pubertal adolescents from Bedfordshire

Glycaemic index (GI) and Glycaemic load (GL) have been positively associated with body mass index (BMI) and obesity related cardiometabolic risk factors in adults, but limited research exists for such relationships in adolescent populations. The associations of GI and GL with adiposity measures were assessed in 14–19 year old, postpubertal adolescents (n = 47) from Bedfordshire, U.K. Data were collected as part of ongoing research studies; the SIRENS study (study of insulin resistance factors using exercise and nutritional strategies) and the CROSSROADS study (cross sectional study: risk of adolescent disease). Dietary intake was recorded using 3 day weighed food diaries and analysed using Compeat1 nutritional analysis software. Macronutrient intake, as well as GI and GL were adjusted for energy intake using the residuals method. Other measures included BMI, body fat percentage (%BF), waist circumference (WC) and a maximal test of cardiorespiratory fitness (VO2 peak).