Maturational and social factors contributing to relative age effects in school sports: Data from the London Youth Games.

Few studies have investigated whether relative age effects (RAEs) exist in school sport. None have sought to test the competing maturational and social-agent hypotheses proposed to explain the RAE. We aimed to determine the presence of RAEs in multiple school sports and examine the contribution of maturational and social factors in commonplace school sports. We analyzed birth dates of n=10645 competitors (11-18 years) in the 2013 London Youth Games annual inter-school multisport competition and calculated odds ratio (OR) for students competing based on their yearly birth quarter (Q1-Q4). Multivariate logistic regression was used to determine the relative contribution of constituent year (Grade) and relative age in netball and football which used multiyear age groupings. In girls, RAEs were present in the team sports including hockey, netball, rugby union, cricket and volleyball but not football. In boys, RAEs were stronger in common team sports (football, basketball cricket) as well as athletics and rowing. In netball and football teams with players from two constituent years, birth quarter better-predicted selection than did constituent year. Relatively older players (Q1) from lower constituent years were overrepresented compared with players from Q3 and Q4 of the upper constituent years. RAEs are present in the many sports commonplace in English schools. Selection of relatively older players ahead of chronologically older students born later in the selection year suggests social agents contribute to RAEs in school sports.

Scaling waist girth for differences in body size reveals a new improved index associated with cardiometabolic risk.

Our aim was to examine whether a new ratio, waist divided by height0.5 (WHT.5R), is both independent of stature and a stronger predictor of cardiometabolic risk (CMR) than other anthropometric indices. Subjects (4117 men and 646 women), aged 20-69 years, were assessed for stature (cm), mass (kg), waist, and hip girths (cm) from which body mass index (BMI), waist-to-hip ratio (WHR), waist-to-height ratio (WHTR), and two new indices, a body shape index (ABSI) and WHT.5R, were determined. We used the allometric power law, W = a.HTb , to obtain a simple body shape index for waist girth (W) to be independent of stature (HT). Physical activity was determined using self-report, and physical fitness was determined using the Bruce protocol. Glucose, total cholesterol, low-density lipoprotein, high-density lipoprotein, triglycerides, and TC/HDL ratio were determined from fasting venous blood samples. A single CMR composite score was derived from log-transformed z-scores of Triglycerides + average blood pressure ((diastolic + systolic)/2) + glucose + HDL (*-1). Results confirmed WHT.5R to be independent of stature and the strongest predictor of CMR, compared with BMI, WC, WHR, ABSI, and WHTR. We also found that CMR scores decline significantly with increasing fitness and physical activity, confirming that being fit and active can compensate for the adverse effects of being fat as measured by all other anthropometric indices. In conclusion, WHT.5R was the best anthropometric index associated with CMR, and being both physically fit and active has a protective effect on CMR, irrespective of weight status.

Six-year changes in body mass index and cardiorespiratory fitness of English schoolchildren from an affluent area.

We compared values of body mass index (BMI) and cardiorespiratory fitness (20 m shuttle-run test) of n=157 boys and n=150 girls aged 10-11 measured in 2014 with measures from 2008 and 1998. Boys' fitness was lower (d=0.68) in 2014 than 2008, despite a small (d=0.37) decline in BMI. Girl's BMI changed trivially (d=0.08) but cardiorespiratory fitness was lower (d=0.47) in 2014 than 2008. This study suggests fitness is declining at 0.95% per year, which exceeds the 0.8% rate of decline we reported between 1998 and 2008 and is double the global average of 0.43%. Declines in fitness were independent of changes in BMI suggesting continued reductions in English children's habitual physical activity levels.

Pilot investigation of the oxygen demands and metabolic cost of incremental shuttle walking and treadmill walking in patients with cardiovascular disease.

OBJECTIVE: To determine if the metabolic cost of the incremental shuttle-walking test protocol is the same as treadmill walking or predicted values of walking-speed equations. SETTING: Primary care (community-based cardiac rehabilitation). PARTICIPANTS: Eight Caucasian cardiac rehabilitation patients (7 males) with a mean age of 67±5.2 years. PRIMARY AND SECONDARY OUTCOME MEASURES: Oxygen consumption, metabolic power and energy cost of walking during treadmill and shuttle walking performed in a balanced order with 1 week between trials. RESULTS: Average overall energy cost per metre was higher during treadmill walking (3.22±0.55 J kg/m) than during shuttle walking (3.00±0.41 J kg/m). There were significant post hoc effects at 0.67 m/s (p<0.004) and 0.84 m/s (p<0.001), where the energy cost of treadmill walking was significantly higher than that of shuttle walking. This pattern was reversed at walking speeds 1.52 m/s (p<0.042) and 1.69 m/s (p<0.007) where shuttle walking had a greater energy cost per metre than treadmill walking. At all walking speeds, the energy cost of shuttle walking was higher than that predicted using the American College of Sports Medicine walking equations. CONCLUSIONS: The energetic demands of shuttle walking were fundamentally different from those of treadmill walking and should not be directly compared. We warn against estimating the metabolic cost of the incremental shuttle-walking test using the current walking-speed equations.

Athletic performance and birth month: is the relative age effect more than just selection bias?

The aim of this study was to determine if month of birth affects performance in 3 tests of physical function in children and adolescents. We measured cardiorespiratory fitness, handgrip strength and lower-body power expressed them relative to (whole year) age then compared scores between calendar year birth-months. We also expressed test performance as the likelihood of achieving criterion-referenced fitness standards. There were significant main effects of birth-month for cardiorespiratory fitness (F=4.54, p<0.001), strength (F=6.81, p<0.001) and power (F=3.67, p<0.001). Children born in November were fitter and more powerful than those born at other times, particularly the summer months (April, May and June). October-born children were stronger than those born in all months except September and November. This relationship was evident despite controlling for decimal age and despite no significant inter-month differences in anthropometric characteristics.There is a clear physical advantage for those born in the autumn and this may explain some of the bias in sports selection attributed to the relative age effect, particularly when the British school-year (September) cut-off is used.

Predictors of shuttle walking test performance in patients with cardiovascular disease.

OBJECTIVE: The incremental shuttle walking test (ISWT) is used to estimate cardiorespiratory fitness, but data from healthy individuals suggest that demographic and anthropometric measures account for much of the variance in test performance. The aim of this study was to determine whether anthropometric, demographic and selected gait measures also predict ISWT performance (i.e. distance walked) in patients with cardiovascular disease. DESIGN: Observational study. SETTING: A community-based cardiac rehabilitation centre (Cohort 1) and a hospital outpatient cardiac rehabilitation programme (Cohort 2). PARTICIPANTS: Sixteen patients with clinically stable cardiovascular disease (Cohort 1) and 113 patients undergoing cardiac rehabilitation (Cohort 2). INTERVENTIONS: Patients in Cohort 1 performed the ISWT on two occasions. Anthropometric data and walking and turning variables were collected. Linear regression analyses were used to identify the predictors of test performance. The authors subsequently attempted to validate the equation created by comparing predicted and actual ISWT values in a larger (n=113) validation sample (Cohort 2). MAIN OUTCOME MEASURES: Distance walked during ISWT, step length and height. RESULTS: No gait or turning measures were significantly associated with ISWT performance. Distance walked correlated most strongly with step length (r=0.83, P<0.05) and height (r=0.74, P<0.05). Given the similarity of these correlations and the rarity of step length assessment in clinical practice, ISWT performance was predicted using patient's height; this explained 55% of the variance in ISWT performance. Height was also the best predictor in Cohort 2, explaining 17% of test variance (P<0.01). Body mass index explained an additional 3% of variance (P<0.05) in ISWT performance. CONCLUSIONS: Routine clinical measures, particularly patient's height, are predictive of ISWT performance. The findings of the present study are in partial agreement with similar studies performed in healthy individuals, and it remains unclear whether the ISWT performance of patients with cardiovascular disease is influenced by the same factors as the ISWT performance of healthy individuals.

Metabolic risk profile of schoolchildren and joint physical activity with an adult in the household: multilevel analysis.

We aim to examine the relationship between metabolic risk (MR) profile and physical activity (PA) with an adult within the household. A total of 4761 schoolchildren (54% boys) aged 10-16 years old were categorized as either at high MR or low MR profile based on their weight and systolic blood pressure status. We assessed the frequency of PA with an adult within the household and fitness. Multilevel regressions were used to determine the likelihood of being at MR in schoolchildren. The proportion of males and females who engage in PA with adults daily was 17.4% and 10.4%, respectively. 16.5% male and 17.2% female did not engage in any PA with adults at all. Compared with those engaging in PA daily with adults in their household, schoolchildren who have reported no such PA were 54% (OR 1.54, 95% CI, 1.07-2.20) likely to have an elevated MR profile. Those who sometimes do PA with adult were 25% (OR 1.25, 95% CI, 0.82-1.93) more likely to have a higher MR profile. After adjusting for PA and fitness, PA with adults remains a determinant of MR profile in males. Compared with those that reported they daily did, schoolchildren were more likely to be unfit if they either sometimes engaged in PA with adults (OR 2.11, 95% CI, 1.44-3.09) or never (OR 2.89, 95% CI, 1.89-4.43). Joint PA with an adult within household could increase schoolchildren's fitness level and may reduce the risk of metabolic diseases.

Temporal relationships between screen-time and physical activity with cardiorespiratory fitness in English schoolchildren: a 2-year longitudinal study.

OBJECTIVE: To determine the temporal relationships screen-time and physical activity have with cardiorespiratory fitness. METHOD: Measures were made over two years (2008-2010) in 1500 participants aged 11.5 (SD 0.5) years at baseline. RESULTS: Tracking coefficients were low-to-moderate for all measures. At follow-up, 25% of participants moved from having low (<2h) to high (≥ 2 h) daily screen-time and 6% became unfit according to FITNESSGRAM standards. Baseline screen-time was the strongest univariate predictor of becoming unfit. Multivariate analysis controlling for decimal age, BMI and deprivation confirmed baseline screen-time as the strongest independent predictor of becoming unfit over the 2-year study period (OR 2.4; 95%CI:1.4-4.0). Current (OR 2.3; 95%CI:1.3-4.0) and previous (OR 1.7; 95%CI:1.0-2.9) physical activity levels also independently predicted becoming unfit. CONCLUSION: There is currently no guidance for limiting screen-time in UK children. These longitudinal data add to the cross-sectional evidence of lower physical activity and fitness in children reporting ≥ 2 h daily screen-time. More importantly, these data demonstrate that high screen-time during childhood is an independent predictor of lower cardiorespiratory fitness in adolescence.

The effects of views of nature on autonomic control.

Previously studies have shown that nature improves mood and self-esteem and reduces blood pressure. Walking within a natural environment has been suggested to alter autonomic nervous system control, but the mechanisms are not fully understood. Heart rate variability (HRV) is a non-invasive method of assessing autonomic control and can give an insight into vagal modulation. Our hypothesis was that viewing nature alone within a controlled laboratory environment would induce higher levels of HRV as compared to built scenes. Heart rate (HR) and blood pressure (BP) were measured during viewing different scenes in a controlled environment. HRV was used to investigate alterations in autonomic activity, specifically parasympathetic activity. Each participant lay in the semi-supine position in a laboratory while we recorded 5 min (n = 29) of ECG, BP and respiration as they viewed two collections of slides (one containing nature views and the other built scenes). During viewing of nature, markers of parasympathetic activity were increased in both studies. Root mean squared of successive differences increased 4.2 ± 7.7 ms (t = 2.9, p = 0.008) and natural logarithm of high frequency increased 0.19 ± 0.36 ms(2) Hz(-1) (t = 2.9, p = 0.007) as compared to built scenes. Mean HR and BP were not significantly altered. This study provides evidence that autonomic control of the heart is altered by the simple act of just viewing natural scenes with an increase in vagal activity.

Screen time and physical activity in youth: thief of time or lifestyle choice?

BACKGROUND: This study aimed to examine the relationship between screen time and physical activity (PA) in children and adolescents but also to determine specific elements of PA that were most closely associated with screen time. METHODS: We studied a cross-sectional sample of 6176 10.0-15.9 year olds (53% boys, 12.9 ± 1.5 years) who completed the Physical Activity Questionnaire for Children/Adolescents and reported daily screen time. Differences in total PA and specific elements of PA were examined between groups reporting: < 2 h, 2-4 h, and > 4 h daily screen time. RESULTS: There were significant differences between screen time groups in: total PA, number of bouts of PA reported, after school PA, evening PA and weekend PA (P < .0001). There was a graded, negative association between higher screen time and lower free-time PA. Participants reporting < 2 h screen time were also significantly more active during school lunch breaks than those reporting > 2 h. Boys reporting > 4 h screen time were less active during physical education lessons. CONCLUSIONS: Screen time is significantly and negatively associated with PA in British youth. Screen time may displace active pursuits out of school but is also associated with lower PA during school. Daily screen time should be limited to < 2 h in line with current recommendations.

Prevalence of high screen time in English youth: association with deprivation and physical activity.

BACKGROUND: Physical activity (PA) and deprivation are major determinants of health. We estimated the prevalence of high screen time (ST) among English youth and examined whether deprivation mediated the relationship between ST and PA. METHODS: It is a cross-sectional study of 6240 participants (53% boys, aged 10-15 years) enrolled in the East of England Healthy Hearts study. The participants were categorized into three groups based on daily ST: <2, 2-4 or >4 h. Participants were classified as 'active' or 'inactive' based on PA z-scores. RESULTS: Prevalence of >2 h ST was 36%. Participants reporting <2 h daily ST were more likely to be active than those reporting 2-4 h (adjusted OR: 1.51, 95% CI: 1.26-1.82, P< 0.001) or >4 h (adjusted OR: 2.26, 95% CI: 1.91-2.67, P< 0.001). Analysis of covariance demonstrated a significant main effect for ST on PA (F = 85.7, P< 0.001) with lower PA in each ascending ST group (P< 0.001). Deprivation was not significantly associated with PA and did not mediate the relationship between ST and PA. CONCLUSIONS: There is high prevalence of >2 h ST in English schoolchildren. PA is lower in children reporting 2-4 versus <2 h daily ST and lower still in those classified as heavy users (>4 h) independent of deprivation.

Contrasting physical activity patterns in children and adolescents living in differing environments in the U.K.

AIMS: There is evidence for lower physical activity (PA) in rural adults; it is important to evaluate how the environment influences the PA of children and adolescents. METHODS: We compared the PA of 6485 English 10-15.9 year olds according to two systems for classifying the immediate environment. System one compared urban and rural areas. System two compared urban, town and fringe, and rural areas. Analyses were carried out separately for children (<13 years) and adolescents (>13 years). RESULTS: Rural children were more active than those from urban areas (OR 1.38, 95% CI 1.15-1.66) as were adolescents (OR 1.30, 95% CI 1.11-1.51). Using trilateral division, children were more active if they lived in town and fringe (OR 1.32, 95% CI 1.03-1.67) or rural (OR 1.45, 95% CI 1.14-1.84) areas compared with urban areas. Adolescents from town and fringe areas were more active than urban dwellers (OR 1.50, 95% CI 1.24-1.81). Rural adolescents' PA did not differ from urban dwellers'. CONCLUSIONS: Rural environments support PA in children but not that of adolescents. Town and fringe areas with mixed elements of rural and urban land use appear to facilitate and sustain PA in both children and adolescents.

Associations between habitual school-day breakfast consumption, body mass index, physical activity and cardiorespiratory fitness in English schoolchildren.

OBJECTIVES: The aim of this study was to assess associations between habitual school-day breakfast consumption, body mass index (BMI), physical activity (PA) and cardiorespiratory fitness (CRF). METHODS: BMI, PA and CRF were measured in 4326 schoolchildren aged 10-16 years. Participants were classified as obese or non-obese, as having low or high PA and CRF. Habitual school-day breakfast consumption was assessed by a questionnaire and classified as never, sometimes or always. RESULTS: Participants who sometimes ate breakfast were more likely to be obese than those who always did (P<0.05). Boys who never ate breakfast were more likely to have low PA odds ratio (OR) 2.17, 95% CI 1.48-3.18) and low CRF (OR 2.02, 95% CI 1.40-2.93) than those who always did. Compared with those who always did so, girls were more likely to have low PA if they sometimes (OR 1.39, 95% CI 1.13-1.70) or never (1.48 95% CI 1.06-2.05) ate breakfast, but the likelihood of low CRF was not different between groups. CONCLUSIONS: Habitual breakfast consumption is associated with healthy BMI and higher PA levels in schoolchildren. In boys, regularly eating breakfast is also associated with higher levels of CRF. The higher PA observed in habitual breakfast eaters may explain the higher CRF values observed. These positive health behaviours and outcomes support the encouragement of regular breakfast eating in this age group.

Handgrip strength in English schoolchildren.

AIMS: The aims of this study were to evaluate patterns of handgrip (HG) strength in relation to gender and age in English schoolchildren and to compare this with existing data and produce reference data for this population. METHODS: The HG of 7147 English schoolchildren (3773 boys and 3374 girls) aged 10-15.9 years was measured using a portable Takei handgrip dynamometer (Takei Scientific Instruments Co. Ltd, Tokyo, Japan). Centile data were produced using the Generalized Additive Models for Location, Scale and Shape. Z-scores were generated using existing data for European children. Age and gender interactions were analysed using analysis of covariance. RESULTS: In boys and girls, significant increases in HG were found between every age-group (p < 0.001). Boys were significantly stronger than girls at every age (p < 0.001) and the boys' age-related increase was significantly greater than the girls' (p < 0.001). CONCLUSION: This study provides reference data for handgrip strength in English schoolchildren. Handgrip strength in English children is broadly similar to existing European data, after adjusting for mass and stature. These data could be used for clinical or athletic screening of low and high strength in this population.

Cardiac vagal activity following three intensities of exercise in humans.

SUMMARY: Cardioprotective benefits of exercising at vigorous intensities are known, but reservations remain in prescribing such activity to the untrained population, due to a perceived risk of cardiac events. Few studies have investigated the recovery of the autonomic nervous system (ANS) after a single exercise bout, especially following vigorous exercise in healthy, young but untrained individuals. In this study, the recovery of the ANS, in particular indices of vagal activity were measured postexercise, at three intensities similar to current international recommendations for health. Thirteen individuals (six females, 22.2 +/- 3.1 years) performed three 20-min constant load tests lying supine on a modified bicycle ergometer at the following intensities: moderate (2 mmol l(-1) blood lactate concentration, BLC); hard (3 mmol l(-1)BLC); and vigorous (4 mmol l(-1)BLC) as derived from a maximal test. ECG data were collected during 5-min epochs at baseline then at: 5, 15, 30, 45 and 65-min postexercise. Heart rate variability (HRV) analysis was performed to obtain R-R interval, standard time [root mean square of successive differences (RMSSD)] and frequency measures [natural logarithm of high (lnHF) and low frequency (lnHF)]. RMSSD, lnHF, lnLF and total power were reduced 5-min postexercise following all three intensities (P<0.01). Decreases persisted up to 15-min postexercise following hard and vigorous exercise only (P<0.01). In untrained young adults, parasympathetic reactivation is reduced up to 5-min postexercise regardless of intensity, returning to baseline by 30 min even after vigorous exercise. In this population, the benefits of exercise outweigh any risks of cardiac events that may be evoked by a reduction in the influence of vagal activity.

Randomized controlled trial of supervised exercise to evaluate changes in cardiac function in patients with peripheral atherosclerotic disease.

INTRODUCTION: Peripheral atherosclerotic disease (PAD) is a condition characterized by low functional capacity which is associated with impaired free living, ambulation and low exercise tolerance. The purpose of this randomized controlled study was to evaluate whether changes in maximal walking time are associated with adaptations in cardiovascular function following supervised exercise. METHODS: After ethics approval, 28 patients (63 +/- 11 years) completed a graded treadmill test (2 min stages, 3.2 km h(-1), with gradient increasing 2% every 2 min) until they reached level three or four on the claudication pain scale. Peak oxygen consumption was assessed on a breath-by-breath basis, by online expiratory gas analysis. Following a 40-min recovery period, peak cardiac output was measured using the non-invasive carbon dioxide rebreathing method described by Defares (J Appl Physiol, 13, 1958, 159). Peak cardiac power output was then computed using the equation described by Cooke et al. (Heart, 1998, 79, 289). Patients were randomly assigned to one of two groups: supervised, who exercised at the hospital twice weekly for 12 weeks or control, who received normal treatment which included encouragement to walk regularly. RESULTS: After 12 weeks, there were no significant changes in body mass, peak oxygen consumption, peak cardiac output, peak heart rate, peak cardiac power output, respiratory exchange ratio or rating of perceived exertion in both the supervised and control group. There was a significant improvement (91%) in maximal walking distance following the supervised exercise programme. Although patients' peak cardiovascular measurements were unchanged, the patients in the supervised exercise group were able to complete a higher workload at the end of the 12 weeks of exercise, for the equivalent demands on the circulation system. CONCLUSIONS: The findings from this study suggest that a short-term period of supervised exercise training results in an improved walking time in patients with limiting claudication because of PAD. It also demonstrated that the cardiovascular system becomes more efficient in meeting the demands of exercise. It is recommended that individuals with PAD should undertake exercise as a form of treatment.

The use of heart rate variability measures to assess autonomic control during exercise.

Heart rate variability (HRV) is a non-invasive indicator of cardiac autonomic modulation at rest. During rhythmic exercise, global HRV decreases as a function of exercise intensity. Measures reflecting sympathovagal interactions at rest do not behave as expected during exercise. This makes interpretation of HRV measures difficult, especially at higher exercise intensities. This problem is further confounded by the occurrence of non-neural oscillations in the high-frequency band due to increased respiratory effort. Alternative data treatments, such as coarse graining spectral analysis (CGSA), have demonstrated expected changes in autonomic function during exercise with some success. The separation of harmonic from fractal and/or chaotic components of HRV and study of the latter during exercise have provided further insight into cardioregulatory control. However, more research is needed. Some cross-sectional differences between HRV in athletes and controls during exercise are evident and data suggest longitudinal changes may be possible. Standard spectral HRV analysis should not be applied to exercise conditions. The use of CGSA and non-linear analyses show much promise in this area. Until further validation of these measures is carried out and clarification of the physiological meaning of such measures occurs, HRV data regarding altered autonomic control during exercise should be treated with caution.

Cardiac pumping capability in patients with peripheral vascular disease.

INTRODUCTION: Peripheral vascular disease (PVD) is a condition characterized by atherosclerotic occlusive disease of the lower extremities, low functional capacity and low exercise tolerance. Less empirical data are available concerning the cardiovascular response to maximum exercise tests in patients with PVD. The purpose of this study was to examine cardiovascular variables in patients with peripheral vascular disease. METHODS: Fifty patients (67 +/- 9 years) completed an incremental exercise test (2 min stages, 3.2 km h(-1), with increases of 2% every 2 min) to maximum claudication pain. Maximal oxygen consumption (VO2) was assessed on a breath-by-breath basis by online expiratory gas analysis (CardiO2, Medical Graphics Co.). Blood pressure was recorded at peak exercise. Following a 30-min rest period, patients exercised at the highest level attained during the first test and cardiac output (QT) was measured using the exponential non-invasive rebreathing method. Cardiac power output peak (CPOpeak) in Watts (W), was then computed. RESULTS: Mean +/- SD values were; 13.85 +/- 4.14 ml kg min(-1); maximal walk time 357 +/- 227 s; peak mean arterial pressure 127 +/- 15 mmHg; 9.8 +/- 2.39 (l min(-1)); CPO 2.86 +/- 0.87 W. CONCLUSION: Patients with peripheral vascular disease demonstrate attenuated levels of cardiovascular capacity. This group of patients should be given exercise therapy in order to improve cardiovascular status and ambulatory function.