Concurrent and prospective associations among biological maturation, and physical activity at 11 and 13 years of age.

This study examined concurrent and prospective associations between objective measures of biological maturation, body composition and physical activity (PA) in adolescent males (n = 671) and females (n = 680). Participants born to women recruited to the Avon Longitudinal Study of Parents and Children birth cohort study were assessed at 11 and 13 years. Percentage of predicted adult stature was used as an estimate of biological maturation. PA and time sedentary was assessed over 7 consecutive days using Actigraph accelerometers. Body composition was assessed using whole-body DXA scans. At 11 and 13 years, maturity in males was inversely associated with accelerometer counts-per-minute (CPM) and time engaged in light PA, and positively associated with time sedentary. In females, maturity was inversely associated with accelerometer (CPM) at 11 but not 13 years. Adjusting for accelerometer wear times and corresponding activity levels at 11 years, maturity and percentage fat mass at 11 years did not predict any indices of PA or sedentary behavior in males or females at 13 years. Whereas advanced maturation in males is associated with less PA and more sedentary behavior at 11 and 13 years, maturity at 11 does not predict PA or sedentary behavior at 13 years in either sex.

Habitual levels of vigorous, but not moderate or light, physical activity is positively related to cortical bone mass in adolescents.

CONTEXT: The intensity of habitual physical activity (PA) needed to affect skeletal development in childhood is currently unclear. OBJECTIVE: To examine associations between light PA, moderate PA, and vigorous PA (as assessed by accelerometry), and tibial cortical bone mass (BMC(C)) as measured by peripheral quantitative computed tomography. DESIGN/SETTING: Cross-sectional analysis based on the Avon Longitudinal Study of Parents and Children. PARTICIPANTS: A total of 1748 boys and girls (mean age 15.5 yr) participated in the study. OUTCOME MEASURES: We measured BMC(C), cortical bone mineral density, periosteal circumference, and endosteal circumference by tibial peripheral quantitative computed tomography. RESULTS: Multivariable models, adjusted for height and other activity levels, indicated vigorous PA was positively related to BMC(C) (P = 0.0001). There was little evidence of a relationship with light PA or moderate PA (both P ≥ 0.7). In path analyses, the relationship between vigorous PA and BMC(C) [0.082 (95% confidence interval [CI]: 0.037, 0.128), P = 0.0004] (SD change per doubling of vigorous PA) was minimally attenuated by adjusting for body composition [0.070 (95% CI: 0.026, 0.115), P = 0.002]. In analyses adjusted for body composition, the relationship between vigorous PA and BMC(C) was explained by the periosteal circumference pathway [0.043 (95% CI: 0.004, 0.082), P = 0.03] and the endosteal circumference adjusted for periosteal circumference pathway [0.031 (95% CI: 0.011, 0.050), P = 0.002], while there was little contribution from the cortical bone mineral density pathway (P = 0.3). CONCLUSIONS: Vigorous day-to-day PA is associated with indices of BMC(C) and geometry in adolescents, whereas light or moderate PA has no detectable association. Therefore, promoting PA in childhood is unlikely to benefit skeletal development unless high-impact activities are also increased.

Obesogenic diet and physical activity: independent or associated behaviours in adolescents?

OBJECTIVE: Associations between diet and physical activity may identify behaviours that could be changed together to prevent childhood obesity. The present study examines associations between physical activity and obesogenic dietary behaviours in a large UK adolescent cohort. DESIGN: Cross-sectional analysis of a UK cohort. Adolescents aged 10-11 years completed three 1 d diet diaries. Average daily energy consumption, percentage energy from fat and carbohydrate, energy density and grams of fruit and vegetables were estimated. To assess physical activity participants wore an accelerometer for three or more days. Regression models were run by sex to examine the extent to which dietary variables predicted physical activity before and after controlling for pubertal status, maternal education and adiposity. SETTING: The Avon Longitudinal Study of Parents and Children (ALSPAC), south-west England. SUBJECTS: Adolescents who provided diet data at age 10 years and physical activity data at age 11 years. RESULTS: Among boys, percentage energy from fat was consistently negatively associated with accelerometer-determined indicators of physical activity (standardized beta (beta) = -0.055 to -0.101, P < 0.05) while total energy (beta = 0.066 to 0.091, P < 0.05) and percentage energy from carbohydrate (beta = 0.054 to 0.106, P < 0.05) were positively associated before and after adjustment for confounders. For girls fruit and vegetable intake was consistently positively associated with physical activity (beta = 0.056 to 0.074, P < 0.005). However all associations were weak. Associations were broadly comparable when participants with non-plausible dietary reports were included or excluded from the analyses. CONCLUSIONS: Obesogenic diet and physical activity behaviours were weakly associated, suggesting that interventions should focus on implementing strategies that are independently successful at changing diet or physical activity behaviours either separately or in combination.

Myopia and later physical activity in adolescence: a prospective study.

OBJECTIVES: To investigate associations between objectively measured physical activity (PA) and myopia in children. METHODS: Children from the Avon Longitudinal Study of Parents and Children (ALSPAC) were asked to wear a uniaxial accelerometer for 7 days. Measures of counts per minute (cpm), minutes spent in moderate to vigorous activity (MVPA) and minutes of sedentary behaviour (msed) were derived from the accelerometer worn at age 12. Children were also examined, at age 10, using an autorefractor to estimate myopia. Social and parental factors were collected from pregnancy and physical measures of the child were recorded at age 12. RESULTS: 4880 children had valid PA and autorefraction data. In minimally adjusted models (age and gender) myopic children were less active than the other children: beta = -49.9 cpm (95% CI -73.5 to -26.4, p = <0.001). The myopic group spent less time in MVPA than the other children: beta = -3.2 minutes MVPA (95% CI -5.2 to -1.1, p = 0.003) and more time sedentary: beta = 15.8 minutes (95% CI 5.8 to 25.8, p = 0.002). The effect sizes were attenuated by adjustment for social and behavioural confounders although myopia status in the better (less myopic on autorefraction) eye remained strongly associated with cpm and MVPA but less so for sedentary behaviour: beta = -36.8 cpm (95% CI -67.8 to -5.8, p = 0.02), beta = -2.7 MVPA (95% CI -5.3 to -0.1, p = 0.04), beta = 10.1 msed (95% CI -2.9 to 23.1, p = 0.13). CONCLUSION: Myopic children may be more at risk of having lower levels of PA than their non-myopic peers, although the difference was modest.

Association of duration of television viewing in early childhood with the subsequent development of asthma.

OBJECTIVE: To investigate whether duration of television (TV) viewing in young children is associated with subsequent development of asthma. METHODS: Children taking part in the Avon Longitudinal Study of Parents and Children (ALSPAC) with no wheeze up to the age of 3.5 years and follow-up data at 11.5 years of age took part in a prospective longitudinal cohort study. The main outcome measure was asthma, defined as doctor-diagnosed asthma by 7.5 years of age with symptoms and/or treatment in the previous 12 months at 11.5 years of age. Parental report of hours of TV viewing per day by the children was ascertained at 39 months. RESULTS: In children with no symptoms of wheeze at 3.5 years of age and follow-up data at 11.5 years of age, the prevalence of asthma was 6% (185/3065). Increased TV viewing at 3.5 years was associated with increased prevalence of asthma at 11.5 years of age (p for linear trend = 0.0003). Children who watched television for >2 h/day were almost twice as likely to develop asthma by 11.5 years of age as those watching TV for 1-2 h/day (adjusted odds ratio 1.8 (95% CI 1.2 to 2.6)). CONCLUSION: Longer duration of TV viewing in children with no symptoms of wheeze at 3.5 years of age was associated with the development of asthma in later childhood.

Between- and within-day variability in physical activity and inactivity in 9- and 15-year-old European children.

To examine differences in levels of physical activity (PA), time spent at moderate-to-vigorous intensity PA (MVPA) and time spent sedentary between and within days in children from four European countries, 1954 9 - and 15-year-olds were included. PA was measured during 2 weekdays and 2 weekend days using the manufacturing technology-incorporated (MTI) accelerometer. Average count per minute, time spent sedentary, time spent at MVPA and the proportion of children accumulating > or =60 min of MVPA were calculated. Data were compared between weekdays and weekend days and between school time and leisure-time. Although not entirely consistent across countries, overall PA, time spent sedentary and the proportion of children accumulating > or =60 min of MVPA were higher during weekdays compared with weekend days. Differences in overall PA between school time and leisure-time were highly inconsistent between countries. Few children (4-31%) accumulated > or =60 min of MVPA either during school time or during leisure-time. Differences in activity patterns between weekdays and weekend days are explained by less accumulated time in MVPA during weekend days. Weekend days and leisure-time during weekdays seem appropriate targets when promoting PA in order to increase the proportion of children achieving current recommendations on health-enhancing PA.

Comparison of equations for predicting energy expenditure from accelerometer counts in children.

Several prediction equations developed to convert body movement measured by accelerometry into energy expenditure have been published. The aim of this study was to examine the degree of agreement between three different prediction equations, when applied to data on physical activity in a large sample of children. We examined 1321 children (663 boys, 658 girls; mean age 9.6+/-0.4 years) from four different countries. Physical activity was measured by the MTI accelerometer. One equation, derived from doubly labeled water (DLW) measurements, was compared with one treadmill-based (TM) and one room calorimeter-based (CAL) equation (mixture of activities). Predicted physical activity energy expenditure (PAEE) was the main outcome variable. In comparison with DLW-predicted PAEE, both laboratory-derived equations significantly (P<0.001) overestimated PAEE by 17% and 83%, respectively, when based on a 24-h prediction, while the TM equation significantly (P<0.001) underestimated PAEE by 46%, when based on awake time only. In contrast, the CAL equation agreed better with the DLW equation under the awake time assumption. Predicted PAEE differ substantially between equations, depending on time-frame assumptions, and interpretations of average levels of PAEE in children from available equations should be made with caution. Further development of equations applicable to free-living scenarios is needed.

Do children from an inner city British school meet the recommended levels of physical activity? Results from a cross sectional survey using objective measurements of physical activity.

Questionnaire surveys suggest physical activity levels in children are low, particularly among children from deprived areas. Using accelerometers, it was found that children from a deprived inner city school were active at recommended levels and had similar levels of activity to children in other studies from more affluent populations. However, this finding was dependent on the threshold used to define moderate activity.

Attitudes and practices of physicians and nurses regarding physical activity promotion in the Catalan primary health-care system.

BACKGROUND: In Catalonia a high percentage of the population remains inactive. General practices are an ideal setting to advise on physical activity (PA). However, there is a lack of evidence regarding practices, barriers and predictors of such promotion in the Catalan primary health-care system. This study set out to establish descriptive baseline data for PA promotion in Catalan general practices, and to explore the experiences of doctors/nurses in promoting PA in their day-to-day professional lives. METHODS: A mixed-method approach was adopted. A survey was conducted with 245 physicians/nurses (58% response rate). Subsequently, focus groups (n = 5) and semi-structured interviews (n = 7) were conducted with 18 physicians and 15 nurses. After coding for important themes, the final interpretation was confirmed by contributors. RESULTS: Eighty-eight percent of physicians/nurses promoted PA at least infrequently. However, work conditions were perceived as unfavourable, with the main barriers being lack of (i) time, (ii) training and (iii) protocols. Qualitative data showed that PA promotion was opportunistic, focused on selected patients, used generalized messages and was highly dependent on personal interests. Regular promotion was encouraged by direct experiences of the benefits of regular exercising, knowing patients well, being supported by medical colleagues and creating links with other community institutions. PA promotion was especially hindered by seeing PA promotion as a secondary task, and patients ignoring recommendations. CONCLUSIONS: PA promotion in Catalonia remains to be integrated into practice consultations. Therefore, strategies should be developed within public health. Using a mixed-method approach provided a broader range of evidence than most studies, which rely on quantitative methods.

The association of birthweight and contemporary size with insulin resistance among children from Estonia and Denmark: findings from the European Youth Heart Study.

OBJECTIVES: To assess the associations of birthweight, contemporary body mass index and height with insulin resistance in children. DESIGN: Cross-sectional study. PARTICIPANTS: From Estonia (n = 1174) and Denmark (n = 1018), 2192 school children aged 9 and 15 years were randomly selected. MAIN OUTCOMES: Insulin resistance (homeostasis model assessment), triglyceride levels, high-density lipoprotein cholesterol and systolic blood pressure. RESULTS: There was an inverse association between birthweight and insulin resistance and a positive association between contemporary body mass index and insulin resistance. With adjustment for maternal and paternal educational level, income, smoking and body mass index, an increase of one unit of sex, age and country standardized body mass index z-score was associated with a 5% (95% CI: 2, 7%) increase in homeostasis model assessment (HOMA) score and a one-unit z-score increase in birthweight with a 2% (95% CI: 0, 5%) decrease in HOMA score. In the 9-year-old age group, height was positively associated with insulin resistance [for a one-unit increase in height z-score HOMA score increased by 30% (95% CI: 14, 50%)], but in the 15-year-old age group there was no association between height and insulin resistance (4% (95% CI: -5, 14%), P for interaction with age group = 0.001). For both ages, those in the lowest third of the birthweight distribution and highest third of the body mass index distribution were most insulin resistant and, among 9-year olds, those in the lowest third of the birthweight distribution and highest third of the height distribution were most insulin resistant. Birthweight was only inversely associated with systolic blood pressure when adjustment was made for either contemporary body mass index or height and there was no association between birthweight and high-density lipoprotein or triglyceride concentrations. CONCLUSIONS: Taken together, these results suggest that a slow intrauterine growth trajectory and/or a fast post-natal growth trajectory is associated with greater insulin resistance in childhood.

Infant feeding and components of the metabolic syndrome: findings from the European Youth Heart Study.

AIMS: To assess the associations of type and duration of infant feeding with components of the metabolic syndrome in children aged 9 and 15. METHODS: A total of 2192 randomly selected schoolchildren aged 9 and 15 years from Estonia (n = 1174) and Denmark (n = 1018) were studied. Insulin resistance (homoeostasis model assessment), triglyceride levels, high density lipoprotein cholesterol, and systolic blood pressure were measured. RESULTS: Children who had ever been exclusively breast fed had lower systolic blood pressures than those who were not. With full adjustment for age, sex, country, birth weight, pubertal stage, body mass index, height, maternal and paternal education, income, smoking, and body mass index the mean systolic blood pressure of children who had ever been breast fed was 1.7 mm Hg (95% CI -3.0 to -0.5) lower than those who had never been exclusively breast fed. There was a dose-response in this association with decreasing mean systolic blood pressure across categories from never exclusively breast fed to breast fed for more than six months. Exclusive breast feeding was not associated with other components of the metabolic syndrome. Results were similar when examined separately in each country. CONCLUSIONS: The magnitude of the association, its independence of important confounding factors, and the dose-response suggest that exclusive breast feeding is causally associated with reduced systolic blood pressure. The magnitude of the effect we found with blood pressure is comparable to the published effects of salt restriction and physical activity on blood pressure in adult populations, suggesting that it is of public health importance.

Kiwifruit protects against oxidative DNA damage in human cells and in vitro.

Antioxidant micronutrients may account for the beneficial effects of fruits on human health. A direct demonstration that consumption of fruit decreases oxidative DNA damage in human cells would support this hypothesis. Kiwifruit was taken as an example of a food with putative antioxidant properties, and its effectiveness at decreasing oxidative DNA damage was assessed in ex vivo as well as in vitro tests. The comet assay (single-cell gel electrophoresis) was used to measure DNA damage in lymphocytes collected during a human supplementation trial with a single 0.5-liter drink of kiwifruit juice (with water as a control). The comet assay was also modified to assess the antioxidant effect of kiwifruit in vitro by measuring the ability of an extract to interfere with oxidative damage to DNA induced by H2O2. Ex vivo, consumption of kiwifruit led to an increased resistance of DNA to oxidative damage induced by H2O2 in isolated lymphocytes, in comparison with lymphocytes collected after a control drink of water. No effect was seen on endogenous DNA damage. In vitro, a simple extract of kiwifruit, buffered to pH 7, was more effective than a solution of vitamin C (of equivalent concentration) at protecting DNA from damage, whereas at the highest concentrations tested, neither kiwi extract nor vitamin C had a protective effect. We have demonstrated significant antioxidant activity of kiwifruit ex vivo and in vitro, not attributable entirely to the vitamin C content of the fruit. Our dual approach is appropriate for testing other fruit and vegetable products for potential antioxidant effects.

The physical activity, fitness and health of children.

It is clear that, despite their natural tendencies, children have become less physically active in recent decades, with children today expending approximately 600 kcal days' less than their counterparts 50 years ago. Although the health consequences of a reduced energy expenditure in adults is well documented, there is little direct evidence linking sedentariness with health in children. However, three main benefits arising from adequate childhood physical activity have been postulated. The first is direct improvements in childhood health status; evidence is accumulating that more active children generally display healthier cardiovascular profiles, are leaner and develop higher peak bone masses than their less active counterparts. Secondly, there is a biological carry-over effect into adulthood, whereby improved adult health status results from childhood physical activity. In particular, childhood obesity may be a precursor for a range of adverse health effects in adulthood, while higher bone masses in young people reduce the risk of osteoporosis in old age. Finally, there may be a behavioural carry-over into adulthood, whereby active children are more likely to become more active (healthy) adults. However, supporting evidence for this assertion is weak. Given this background, recent health guidelines suggesting that children should accumulate 60 min of moderate-intensity physical activity every day--supplemented by regular activities that promote strength flexibility and bone strength--appear to be justified. Future developments should include the implementation of large-scale, longitudinal studies spanning childhood and young adulthood, the further refinement of tools for measuring physical activity accurately in young people, and research into the relative strength of association between fitness--as well as activity--and health in children.

Charting the physical activity patterns of contemporary children and adolescents.

The impact of physical inactivity on health is well accepted throughout the medical and health service community. However, the case has largely been established through epidemiological studies with adults. Substantial attention has been paid to the activity levels of children and adolescents, largely because of changing lifestyles that have threatened the opportunity to be active and also introduced attractive sedentary alternatives such as playing computer games. The research evidence that children have become less active to the point where it is seriously damaging their current and future health has been difficult to establish. This situation is due to difficulties in establishing sensitive health risk markers, and also with the assessment of the different elements of physical activity which in children and adolescents is a complex profile of social behaviours. Self report of activity is unreliable with young children, and objective measures are required that are cheap and effective with large samples and that are capable of measuring levels, volume and patterns of physical activity. Accelerometry in combination with diaries offers the best current solution for most activity-health relationships, and for informing intervention need and design.

What is the magnitude of blood pressure response to a programme of moderate intensity exercise? Randomised controlled trial among sedentary adults with unmedicated hypertension.

BACKGROUND: Current guidelines for the management of hypertension recommend regular, moderate intensity aerobic exercise such as brisk walking as a means of blood pressure reduction. However, there is a lack of consistent evidence regarding the magnitude of blood pressure response to such a prescription. In particular, no well designed studies have investigated the efficacy of a programme of exercise meeting current guidelines. AIM: To investigate the effect of a six-week programme of moderate intensity exercise on daytime ambulatory blood pressure (10.00 am to 10.00 pm) among unmedicated, sedentary adults aged 25 years to 63 years with office blood pressure of 150 mmHg to 180 mmHg systolic and/or 91 mmHg to 110 mmHg diastolic. METHOD: Randomised controlled trial of participants carrying out 30 minutes of moderate intensity exercise (brisk walking or equivalent) five days per week for six weeks compared with controls who maintained existing levels of physical activity. RESULTS: Compliance with the exercise programme was high. The reduction in mean daytime ambulatory blood pressure between baseline and six-week follow-up was greater in the intervention group than in the control group for both systolic and diastolic blood pressure. However, this net hypotensive effect was not statistically significant (systolic = -3.4 mmHg, 95% CI = -7.4 to 0.6; diastolic = -2.8 mmHg, 95% CI = -5.8 to 0.2). Adjusting for baseline differences in mean ambulatory blood pressure in an analysis of covariance led to a reduction in the estimated magnitude of the effect (systolic = -1.9 mmHg, 95% CI = -5.4 to 1.7, P = 0.31; diastolic = -2.2 mmHg, 95% CI = -4.9 to 0.5, P = 0.11). CONCLUSION: Despite high compliance with the exercise programme, the magnitude of the hypotensive effect of moderate intensity exercise was not as great as that found in studies of higher intensity exercise among hypertensives. Expectations of general practitioners and patients that a programme of moderate intensity exercise will lead to a clinically important reduction in the individual's blood pressure are unlikely to be realised.

Comparison of stage-matched and unmatched interventions to promote exercise behaviour in the primary care setting.

This study examined the effectiveness of stages of change-based counselling for exercise delivered by nurses in four primary care centres. Two-hundred and ninety-four subjects enrolled, recruited from patients attending 30-min health checks. The average age of participants was 42.4 years (SD = 15.1) and 77% were female. Participants completed a questionnaire assessing stage of exercise adoption, self-efficacy and exercise levels. Each centre was assigned to either one of three experimental conditions or to a control condition. Participants were counselled accordingly, receiving either stage-oriented exercise materials with counselling (stage plus counselling), stage-oriented materials without counselling (stage no counselling), non-staged materials with counselling (counselling only) or the current level of advice (control). Sixty-one percent (n = 180) returned follow-up questionnaires. When baseline differences in self-efficacy, age and gender were controlled for, there was no significant group or interaction effect for stage. There was a significant time effect (F = 3.55, P = 0.031). Post hoc analyses showed that significant differences were between baseline and 2 (t = -3.02, P = 0.003) and 6 months (t = -2.67, P = 0.009). No changes in self-efficacy and exercise levels were observed. Stage-based interventions were not superior to the other interventions. All single-contact interventions, while having no impact on exercise behaviour and self-efficacy, did enhance motivation to change.

An evaluation of germinating beans as a source of vitamin C in refugee foods.

OBJECTIVE: To assess whether germinating pulses and beans are a potential source of vitamin C in rations for refugee communities with poor vitamin C status. DESIGN: High pressure liquid chromatographic assessment of vitamin C content of a range of legumes following germination in light and dark and after cooking. RESULTS: Many species of pulses produced significant quantities of vitamin C up to five days following germination in both light and dark although cooking caused a marked loss of ascorbate. CONCLUSION: Germination of approximately half of the seeds of the pulse constituents of many basic rations would be likely to generate, within a 3-5 d germination period, sufficient ascorbate to provide the 10 mg needed to protect adults against the development of scurvy.

Circulating gastrointestinal hormone changes in marathon running.

The purpose of this study was to observe the effect of marathon running on the release of gastrointestinal hormones and whether these might be related to gastrointestinal disturbances in marathon runners. Vasoactive intestinal polypeptide, gastrin, secretin, pancreatic polypeptide, neurokinin A, pancreastatin, insulin and glucagon-like peptide 1 were measured before, immediately upon finishing and 30 min after the race. Twenty-six competitors of the 1992 Belfast Marathon volunteered for this study. They had a mean age of 37 years and a mean finishing time of 239 min. Eight of the subjects complained of gastrointestinal distress during the race. The circulating concentration of all the GI hormones measured, except insulin were significantly elevated after the race. There was no significant change in glucose levels at the finish of the race. Statistical analysis revealed no direct relationship between the large increases in hormone levels and the occurrence of GI symptoms. These results show that GI hormone concentrations are affected by marathon running. Mechanisms of release and possible roles are discussed.