Effect of vertical, horizontal, and combined plyometric training on jump, sprint and change of direction performance in male soccer players

PURPOSE

The purpose of this study was to compare the effects of vertical (VPT), horizontal (HPT) and combined vertical and horizontal (V+HPT) plyometric training on sprint, jump and change of direction (COD) performance in adult male soccer players.

METHOD

Participants were randomly allocated into VPT (n = 8), HPT (n = 8) and V+HPT (n = 8) groups which undertook eight weeks of PT, executing 100 foot contacts per session, twice weekly.

RESULTS

Though demonstrably effective, no specific one of the three applied programmes enhanced performance to a greater extent than another with only the 40 m sprint for the HPT group (mean difference = 0.07 s [HPT] vs. 0.04 s [VPT] and 0.04 s [V+HPT]) and the vertical jump for the V+HPT group (mean difference = 4.5 cm [V+HPT] vs. 4.0 cm [VPT] and 3.25 cm [HPT]) appearing to deviate from a uniform pattern of group level adaptation across the performance tests.

CONCLUSION

A total volume of 100 foot contacts per session, twice per week for eight weeks was sufficient to achieve the observed changes. Though jump and changing direction performance were enhanced, linear sprint performance was largely unchanged and so a more complete and intense programme may have been warranted. No method was superior to another in eliciting changes across these tests and a directionally-specific pattern of adaptation was not apparent.

The relationship between modifiable lifestyle behaviours and self-reported health in children and adolescents in the United Kingdom

Obesity, along with its associated health issues, is closely tied to lifestyle habits. While certain elements affecting childhood health, such as genetics and ethnicity, are beyond individuals' control, there exists modifiable lifestyle behaviours that can facilitate healthier living. This study employed multiple regression analysis to investigate the relationship between specific modifiable lifestyle behaviours and self-reported health. The independent variables considered included days of moderate to vigorous physical activity (MVPA), fruit and vegetable consumption, breakfast frequency, school night sleep duration, and non-school night sleep duration. These variables were chosen for their practical modifiability within participants' daily lives. The analysis revealed a highly significant overall model (F(13,11363) = 191.117, p < .001), explaining 17.9% of the variance in self-reported health. Notably, higher MVPA levels were associated with improved self-reported health (B = 0.136 to 0.730, p < .001). Additionally, regular breakfast consumption and increased fruit and vegetable intake exhibited positive associations with self-reported health (B = 0.113 to 0.377, p < .001), while girls reported lower self-reported health (B = -0.079, p < .001). School night sleep duration was positively linked to self-reported health (B = 0.071, p < .001). Furthermore, a dose-response relationship between MVPA, dietary habits, and health was identified. These findings hold substantial potential for public health campaigns to promote healthy behaviours and prevent chronic diseases in young individuals. It is imperative to emphasise that all the variables considered in this study are readily modifiable aspects of individuals' lives, offering a promising avenue for personal health and well-being enhancement.

What determines participation in sport for older adults in England: A multilevel analysis of Active Lives data

Physical inactivity within an ageing population is an ongoing public health concern for policymakers. Engagement in sport forms a foundation of policy designed to encourage physical activity participation and improve health and wellbeing. This study aimed to (i) understand the extent to which older adults participate in sport and the (ii) correlates that predict this involvement within an English population sample of older adults. A further aim was (iii) to examine the extent in which sports participation may vary due to the opportunity provided across Active Partnerships in England. To address this, a multi-level analysis framed through COM-B was conducted of the 2021 English Active Lives dataset (i.e., during the COVID-19 pandemic). The Active Lives survey provides population-level insight into sport, exercise, and physical activity participation across England. It samples upwards of n = 180,000 participants beyond the age of 16 years and asks questions on factors that influence participation. Our findings drawn from a sample of n = 68,808 older adults (i.e., >60-years of age) indicate that when accounting for variation across regions sports participation was significantly predicted by age (β = -.246, p = .040) and multiple deprivation (β  = .706, p = .030). Further, our analysis suggests sports participation across regions is associated with changes in the perceptions of opportunity to participate (β = -28.70, p = .001). As the UK transitions from the COVID-19 pandemic, findings have implications for the promotion of sports participation for older adults, in that local, regional, and national stakeholders must do more to change perceptions of social and physical opportunity within an ageing population. This may be achieved through adaptations to the recreational sporting landscape, raising awareness, and supportive policy changes on a national level.

The Standard Error/Standard Deviation Mix-Up: Potential Impacts on Meta-Analyses in Sports Medicine

BACKGROUND

A recent review found that 45% of meta-analyses included statistical errors, of which, the most common was the calculation of effect sizes based on standard error (SE) rather than standard deviation (SD) [the SE/SD mix-up].

OBJECTIVES

The first aim of this study was to assess the impact of the SE/SD mix-up on the results of one highly cited meta-analysis. Our second aim was to identify one potential source of the SE/SD mix-up, by assessing how often SE is reported as a measure of sample variability in randomised controlled trials in sports medicine.

METHODS

We checked for potential SE/SD mix-ups in a 2015 meta-analysis of randomised controlled trials reporting the effects of recreational football interventions on aerobic fitness in adults. We corrected effect sizes affected by SE/SD mix-ups and re-analysed the data according to the original methodology. We compared pooled estimates of effect sizes from our re-analysis of corrected values with those of the original study. To assess how often SE was reported instead of SD as a measure of sample variance, we text mined results of randomised controlled trials from seven sports medicine journals and reported the proportion reporting of SE versus SD.

RESULTS

We identified potential SE/SD mix-ups in 9/16 effect sizes included in the meta-analysis describing the effects of football-based interventions versus non-exercise control. The published effect size was standardised mean difference (SMD) = 1.46 (95% confidence interval [CI] 0.91, 2.01). After correcting for SE/SD mix-ups, our re-analysis produced a smaller pooled estimate (SMD = 0.54 [95% CI 0.37, 0.71]). The original pooled estimate for trials comparing football versus running interventions was SMD = 0.68 (95% CI 0.06, 1.4). After correcting for SE/SD mix-ups and re-analysis, the effect was no longer statistically significant (SMD = 0.20 [95% CI - 0.10, 0.49)]). We found that 19.3% of randomised controlled trials reported SE rather than SD to describe sample variability. The relative frequency of the practice ranged from 0 to 25% across the seven journals sampled.

CONCLUSIONS

We found the SE/SD mix-up had inflated estimates for the effects of football on aerobic fitness. Meta-analysts should be vigilant to avoid miscalculating effect sizes. Authors, reviewers and editors should avoid and discourage (respectively) the practice of reporting SE as a measure of sample variability in sports medicine research.

How effective are external cues and analogies in enhancing sprint and jump performance in academy soccer players?

This study investigated the effect of external (EC) and internal coaching cues (IC), analogies with a directional component (ADC) on sprint (20 m) and vertical jump performance in academy soccer players (n = 20). A repeated-measures analysis, with post-hoc comparisons, was used to identify any differences between these cues and a neutral (control) cue. Significant differences were found for both sprint (p < 0.001) and jump (p = 0.022) comparisons among cue types. In post-hoc analyses for the 20 m sprint, significant differences were observed between the EC and the IC, favouring the EC (p < 0.01, ES = 1.27 [CI: 0.24, 2.30]), and "away" ADC and the IC, favouring the "away" ADC (p < 0.01, ES = 1.21 [CI: 0.19, 2.22]). No other cues showed significant differences. For vertical jump, there was just one significant difference between comparisons, that being for the "away" ADC vs. the neutral cue, favouring the latter (p = 0.023, ES = 0.4 [CI: -0.04 to 0.84]). It appears that ECs and ADCs are most effective when coaching sprinting performance in academy soccer players. However, simply encouraging maximal effort from a youth athlete also appears to be a reasonable cueing strategy to drive performance in youth athletes.

The Impact of the Coronavirus Pandemic on the Contribution of Local Green Space and Nature Connection to Mental Health

BACKGROUND

Exposure to green space and feeling connected to the natural environment have independently been associated with improved mental health outcomes. During the coronavirus pandemic, people experienced restrictions on access to the outdoors, and health data indicated a decline in mental health in the UK general population.

METHODS

Data available from two independent surveys conducted prior to and during the pandemic enabled a naturally occurring comparison of mental health and its correlates prior to and during the pandemic.

RESULTS

Survey responses from 877 UK residents were included in the analyses. Independent t-tests revealed significant declines in mental health scores during the pandemic. After controlling for age and gender, greater nature connection significantly predicted lower depression and stress and improved well-being. Percentage of green space did not significantly predict any mental health outcomes. Further, time point (pre- or during COVID) and the interaction of time point with green space and nature connection did not significantly predict any of the outcome measures. The findings indicate that nature connection may play an important role in promoting mental health. Strategies to improve mental health and reduce mental illness should consider the role of nature connection and the use of interventions that involve direct interaction with natural environments.

European fitness landscape for children and adolescents: updated reference values, fitness maps and country rankings based on nearly 8 million test results from 34 countries gathered by the FitBack network

OBJECTIVES

(1) To develop reference values for health-related fitness in European children and adolescents aged 6-18 years that are the foundation for the web-based, open-access and multilanguage fitness platform (FitBack); (2) to provide comparisons across European countries.

METHODS

This study builds on a previous large fitness reference study in European youth by (1) widening the age demographic, (2) identifying the most recent and representative country-level data and (3) including national data from existing fitness surveillance and monitoring systems. We used the Assessing Levels of PHysical Activity and fitness at population level (ALPHA) test battery as it comprises tests with the highest test-retest reliability, criterion/construct validity and health-related predictive validity: the 20 m shuttle run (cardiorespiratory fitness); handgrip strength and standing long jump (muscular strength); and body height, body mass, body mass index and waist circumference (anthropometry). Percentile values were obtained using the generalised additive models for location, scale and shape method.

RESULTS

A total of 7 966 693 test results from 34 countries (106 datasets) were used to develop sex-specific and age-specific percentile values. In addition, country-level rankings based on mean percentiles are provided for each fitness test, as well as an overall fitness ranking. Finally, an interactive fitness platform, including individual and group reporting and European fitness maps, is provided and freely available online (www.fitbackeurope.eu).

CONCLUSION

This study discusses the major implications of fitness assessment in youth from health, educational and sport perspectives, and how the FitBack reference values and interactive web-based platform contribute to it. Fitness testing can be conducted in school and/or sport settings, and the interpreted results be integrated in the healthcare systems across Europe.

Physical Activity and Sedentary Behaviors in Primary School Children in Saudi Arabia during the COVID-19 Pandemic: Association with Parents' Behaviors

During the COVID-19 pandemic, a few studies used accelerometers to assess physical activity (PA) and sedentary behavior in the family context. This study aimed to assess children and parents' moderate and vigorous physical activity (MVPA) and sedentary time, as well as their relationship in MVPA and sedentary time. Data were collected from 30 parent-child dyads during the COVID-pandemic for seven days, using a hip-worn accelerometer. Children and parents engaged in 65.6 and 34.6 min/day in MVPA and 442.2 and 427.9 min/day sedentary, respectively. There was no evidence of gender difference in MVPA and sedentary between boys and girls. Male parent spent more time in MVPA than female parents. A total of 50% of children and 53.3% of parents met the recommended PA. Children's MVPA and sedentary time were both correlated with that of their parents. Adjusted linear regression showed that only child MVPA was negatively associated with their parents' MVPA. There is evidence that multi-level interventions involving parents and children are more effective than interventions focusing on a single group. This study also provides evidence to support the link between MVPA and sedentary time between parents and children. Generalization of the findings is difficult due to the bias of self-selection sample.

A randomised controlled trial of 1- versus 2-day per week formats of Nordic hamstring training on explosive athletic tasks in prepubertal soccer players

This randomised controlled trial examined the effect of volume-equated programmes of Nordic hamstring exercise (NHE) training, executed at frequencies of 1- or 2-days per week, on explosive athletic tasks (30 m sprint, 15 m manoeuvrability and standing long jump [SLJ]) in male youth soccer players (mean age: 10.3 ± 0.5 years). Players were divided into an experimental group (n = 31) which was further subdivided into 1-day (n = 16) and 2-days (n = 15) per week training conditions, and a control group (n = 14). There were significant group-by-time interactions for 30-m sprint (p < 0.001, d = 0.6), SLJ (p = 0.001, d = 1.27) and 15 m manoeuvrability (p < 0.001, d = 0.61). The experimental group demonstrated small to moderate effect sizes in 30-m sprint (d = 0.42, p = 0.077), SLJ (d = 0.97, p < 0.001) and 15 m manoeuvrability (d = 0.61, p < 0.001). The control group showed small significant performance decrements or no change in these variables. There were no significant differences between the 1-day and 2-day training groups. In two of the three tests (30 m sprint, SLJ) the 2-day group demonstrated larger effect sizes. The NHE enhances explosive athletic task performance in prepubertal youth soccer players and there may be only small advantages to spreading training over two days instead of one.

Developing a New Curvilinear Allometric Model to Improve the Fit and Validity of the 20-m Shuttle Run Test as a Predictor of Cardiorespiratory Fitness in Adults and Youth

BACKGROUND AND OBJECTIVES

Doubts have been raised concerning the validity of the 20-m shuttle-run test (20 mSRT) as a predictor of cardiorespiratory fitness (CRF) in youth based on Léger's equation/model. An alternative allometric model has been published recently that is thought to provide, not only a superior fit (criterion validity) but also a more biologically and physiologically interpretable model (construct validity). The purposes of this study were to explore whether allometry can provide a more valid predictor of CRF using 20 mSRT compared with Léger's equation/model.

METHODS

We fitted and compared Léger's original model and an alternative allometric model using two cross-sectional datasets (youth, n = 306; adult n = 105) that contained measurements of CRF ([Formula: see text]/[Formula: see text]) and 20 mSRT performance. Quality-of-fit was assessed using explained variance (R²) and Bland and Altman's limits of agreement.

RESULTS

The allometric models provided superior fits for the youth (explained variance R² = 71.9%) and adult (R² = 77.7%) datasets compared with Léger's equation using their original fixed (R² = 35.2%) or re-estimated parameter models (R² = 65.9%), confirming that the allometric models demonstrate acceptable criterion validity. However, the allometric models also identified a non-linear "J-shaped" increase in energy cost ([Formula: see text]/[Formula: see text]) with faster final shuttle-run speeds (fitted speed exponent = 1.52; 95% CI 1.38-1.65).

CONCLUSION

Not only do allometric models provide more accurate predictions of CRF ([Formula: see text]/[Formula: see text]; ml kg^-1 min^-1) for both youth and adults (evidence of criterion validity), the "J-shaped" rise in energy demand with increasing final shuttle-run speed also provides the evidence of construct validity, resulting in a more plausible, physiologically sound, and interpretable model.

Modification of the Rosenberg Scale to Assess Self-Esteem in Children

Rosenberg's scale (RSES) is widely used to assess global self-esteem (SE) in adults and adolescents but is not validated for children <12 years. This study assessed the internal consistency, convergent validity, and factor structure of a modified RSES for schoolchildren (CRSES) aged 7–12 years. A total of 711 children aged 9.0 ± 1.5 years completed the CRSES; a subset (n = 417) also completed a life satisfaction (LS) scale. Data were submitted for confirmatory factor analysis (CFA) and tests of factorial invariance by sex. Two-way ANOVA compared scores by age-group and sex; whilst Pearson's correlations examined the relationship between LS and SE. Following the use of modification indices the fit for the global SE model met the goodness of fit statistic criteria: χ(27, n = 711) = 77.22; χ^normed = 2.860 CFI = 0.961; RMSEA = 0.051 with 90% CI = 0.038-0.065; SRMR = 0.037; and displayed respectable internal consistency (α = 0.79). The model was also factorially invariant by sex. SE scores did not vary sex (p > 0.05); but were significantly reduced in children aged 9–10 and 11–12 years compared to children aged 7–8 years. The global SE score was significantly correlated (r = 0.51; P < 0.001) with LS. The current version of the CRSES can reliably examine global SE in children aged 7–12 years; extending the use of the RSES to allow tracking across the life course.

Normative reference values for estimated cardiorespiratory fitness in apparently healthy British men and women

Objectives

To develop normative reference standards for estimated cardiorespiratory fitness (eCRF) measured from treadmill-based incremental exercise testing in ~12 000 British men and women.

Methods

Cross-sectional study using retrospectively collected eCRF data from five preventative health screening clinics in the United Kingdom. Reference centiles were developed using a parametric approach by fitting fractional polynomials. We selected the ‘best’ powers by considering both the smallest deviance, and clinical knowledge from the following set of a priori decided powers (-2,-1,-0.5, 0, 0.5,1,2,3). A series of fractional polynomials (FPs) were investigated with three-parameters (median, standard deviation and skewness). The following reference centiles were plotted (3, 5, 10, 25, 50, 75, 90, 95, 97).

Results

We included 9 204 males (median [25^th,75^th centiles] age 48 [44, 53] years; BMI 27 {25, 29] kg∙m^-2; peak VO₂ 36.9 [30.5, 44.7] ml∙kg^-1∙min^-1) and 2 687 females (age 48, [41, 51] years; BMI 24 {22, 27] kg∙m^-2; peak VO₂ 36.5 [30.1, 44.8] ml∙kg^-1∙min^-1) in our analysis to develop the normative values.

Conclusion

Reference values and nomograms for eCRF were derived from a relatively large cohort of preventative health care screening examinations of apparently healthy British men and women. Age- and sex-specific eCRF percentiles were similar to data from international cohort studies. The adoption of submaximal exercise testing protocols reduces individual risk when exercise history is unknown and testing is conducted in a community-based setting. Our findings can be used by health professionals to help guide clinical decision making.

One-year surveillance of body mass index and cardiorespiratory fitness in UK primary school children in North West England and the impact of school deprivation level

OBJECTIVES

Cardiorespiratory fitness (CRF) is independently associated with health and academic attainment in childhood and adolescence. Yet overweight/obesity remains the focus in public health policy. Surveillance of body mass index (BMI) and CRF considering school deprivation levels is limited. Therefore, we examined this in English primary schools.

METHODS

Participants (n=409) were students (9-10 years) from 13 schools. BMI and CRF (20 m shuttle run) were measured at three time points across the academic year and a fourth after summer recess.

RESULTS

BMI z-scores significantly decreased (p=0.015) from autumn (z=0.336 (95% CI 0.212 to 0.460)) to spring (z=0.252 (95% CI 0.132 to 0.371)), and then significantly increased (p=0.010) to summer (z=0.327 (95% CI 0.207 to 0.447)). CRF significantly increased (p<0.001) from autumn (z=0.091 (95% CI -0.014 to 0.196)) to spring (z=0.492 (95% CI 0.367 to 0.616)), no change (p=0.308) into summer (z=0.411 (95% CI 0.294 to 0.528)) and a significant decrease (p<0.001) into the following autumn term (z=0.125 (95% CI 0.021 to 0.230)). BMI was unaffected by deprivation; however, pupils from the most deprived areas saw significantly greater reductions in CRF compared with pupils from affluent areas. No time, or deprivation level, by sex interactions were found.

CONCLUSION

Significant reductions in children's CRF occurred over the summer recess and were greater among children from schools in the most deprived areas. This may help inform future research into interventions targeting physical activity of schoolchildren, particularly over the summer recess.

The dose-response association between V̇O2peak and self-reported physical activity in children

BACKGROUND

Previous research into the association between aerobic fitness and physical activity in children is equivocal. However, previous research has always assumed that such an association was linear. This study sought to characterize the dose-response association between physical activity and aerobic fitness and to assess whether this association is linear or curvilinear and varies by sex, age and weight status.

METHODS

Physical activity (assess using the Physical Activity Questionnaire), aerobic fitness (20 m shuttle-run), BMI, screen-time and socio-demographic data were collected at ages 12, 14 and 16 years in (n = 1422) volunteers from 9 English schools. Multilevel-regression modelling was used to analyse the longitudinal data.

RESULTS

The analysis identified a significant inverted "u-shaped" association between VO₂max and PAQ. This relationship remained having controlling for the influences of sex, age and weight status. Daily screen time >4 hours and deprivation were also associated with being less fit (P < 0.01).

CONCLUSIONS

This longitudinal study suggests that the dose-response relationship between PA and aerobic fitness in children is curvilinear. The health benefits of PA are greater in less active children and that sedentary and less active children should be encouraged to engage in PA rather than more active children to increase existing levels of PA.

Modeling the dose-response rate/associations between VO2max and self-reported Physical Activity Questionnaire in children and adolescents

Background

This study sought to explore the dose-response rate/association between aerobic fitness (VO2max) and self-reported physical activity (PA) and to assess whether this association varies by sex, age, and weight status.

Methods

VO2max was assessed using the 20-m shuttle-run test. PA was assessed using the Physical Activity Questionnaire (PAQ) for Adolescents (aged >11 years, PAQ-A) or for Children (aged ≤11 years, PAQ-C). The associations between VO2max and PAQ were analyzed using analysis of covariance (ANCOVA), adopting PAQ and PAQ2 as covariates but allowing the intercepts and slope parameters of PAQ and PAQ2 to vary with the categorical variables sex, age group, and weight status.

Results

ANCOVA identified a curvilinear association between VO2max and PAQ, with positive linear PAQ terms that varied for both sex and weight status but with a negative PAQ2 term of -0.39 (95% confidence interval (CI): -0.57 to -0.21) that was common for all groups in regard to age, sex, and weight status. These curvilinear (inverted U) associations suggest that the benefits of increasing PA (same dose) on VO2max is greater when children report lower levels of PA compared to children who report higher levels of PA. These dose-response rates were also steeper for boys and were steeper for lean children compared to overweight/obese children.

Conclusion

Health practitioners should be aware that encouraging greater PA (same dose) in inactive and underweight children will result in greater gains in VO2max (response) compared with their active and overweight/obese counterparts.

Cardiorespiratory fitness and activity explains the obesity-deprivation relationship in children

This study examined the association between obesity and deprivation in English children and whether cardiorespiratory fitness or physical activity (PA) can explain this association. Obesity was assessed using IOTF criteria in 8,398 10-16 year olds. Social deprivation was measured using the Index of Multiple Deprivation (IMD) (subdivided into 3 groups; high, mid and low deprivation). Obesity was analysed using binary logistic regression with stature, age and sex incorporated as confounding variables. Children's fitness levels were assessed using predicted VO2 max (20-metre shuttle run test) and PA was estimated using the PA Questionnaire for Adolescents or Children (PAQ). A strong association was found between obesity and deprivation. When fitness and PA were added to the logistic regression models, increasing levels in both were found to reduce the odds of obesity, although it was only by including fitness into the model that the association between obesity and deprivation disappeared. Including estimated PA into the model was found to be curvilinear. Initial increases in PA increase the odds of obesity. Only by increasing PA to exceed the 71st percentile (PAQ = 3.22) did the odds of being obese start to decline. In order to reduce deprivation inequalities in children's weight-status, health practitioners should focus on increasing cardiorespiratory fitness via physical activity levels in areas of greater deprivation.

A Method by Which to Assess the Scalability of Field-Based Fitness Tests of Cardiorespiratory Fitness Among Schoolchildren

Previous research has reported the validity and reliability of a range of field-based tests of children’s cardiorespiratory fitness. These two criteria are critical in ensuring the integrity and credibility of data derived through such tests. However, the criterion of scalability has received little attention. Scalability determines the degree to which tests developed on small samples in controlled settings might demonstrate real-world value, and is of increasing interest to policymakers and practitioners. The present paper proposes a method by which the scalability of cardiorespiratory field-based tests suitable for school-aged children might be assessed. We developed an algorithm to estimate scalability based on a six-component model; delivery, evidence of operating at scale, effectiveness, costs, resource requirements and practical implementation. We tested the algorithm on data derived through a systematic review of research that has used relevant fitness tests. A total of 229 studies that had used field based cardiorespiratory fitness tests to measure children’s fitness were identified. Initial analyses indicated that the 5-min run test did not meet accepted criteria for reliability, whilst the 6-min walk test likewise failed to meet the criteria for validity. Of the remainder, a total of 28 studies met the inclusion criteria, 22 reporting the 20-m shuttle-run and seven the 1-mile walk/run. Using the scalability algorithm we demonstrate that the 20-m shuttle run test is substantially more scalable than the 1-mile walk/run test, with tests scoring 34/48 and 25/48, respectively. A comprehensive analysis of scalability was prohibited by the widespread non-reporting of data, for example, those relating to cost-effectiveness. Of all sufficiently valid and reliable candidate tests identified, using our algorithm the 20-m shuttle run test was identified as the most scalable. We hope that the algorithm will prove useful in the examination of scalability in either new data relating to existing tests or in data pertaining to new tests.

Socio-demographic differences in Colombian children's muscular fitness: Does scaling for differences in body size present a challenge to conventional thinking?

OBJECTIVES

In low- to middle-income countries, children from less-deprived areas (from families of higher socio-economic status [SES]) have superior muscular fitness than those from low-SES groups. They are also taller and heavier, factors associated with muscular fitness. The purpose of this study was to identify any socio-demographic differences in Colombian children's muscular fitness and examine how these conclusions can be modified by scaling for differences in body size.

METHODS

A total of 38,098 youths (46% girls), ninth grade students (aged 14-15 years), participated in a study of cross-sectional design. We recorded SES and family incomes, stature, and mass. Standing broad jump and handgrip strength were used to assess muscular fitness. A multiplicative allometric model was adopted to adjust for body-size differences.

RESULTS

Children from the mid- to high-SES groups jumped significantly higher than children from the lowest SES group, although no SES group difference in grip strength was observed. After adjusting for body size, children from higher SES and with higher family incomes had significantly lower handgrip strength, and their superior jump height performances remained but were greatly reduced. Only children from the highest SES now jumped significantly higher that the lowest SES group.

CONCLUSIONS

The superior jump performance and no difference in handgrip strength of Colombian children from higher SES may simply reflect their superior physiques. When body size is accounted for, these differences are reduced or even reversed, suggesting that children from higher SES groups should not be complacent regarding their apparent superior muscular fitness.

Scaling children's waist circumference for differences in body size

OBJECTIVES

Both waist circumference (WC) and body size (height) increase with age throughout childhood. Hence, there is a need to scale WC in children to detect differences in adiposity status (eg, between populations and different age groups), independent of body size/height.

METHODS

Using two culturally different samples, 1 English (10-15.9 years n = 9471) and 2 Colombian (14-15 years, n = 37,948), for WC to be independent of height (HT), a body shape index was obtained using the allometric power law WC = a.HT^b . The model was linearized using log-transformation, and multiple regression/ANCOVA to estimate the height exponents for WC controlling for age, sex, and any other categorical/population differences.

RESULTS

In both samples, the power-law height exponent varied systematically with age. In younger children (age 10-11 years), the exponent was approximately unity, suggesting that pre-pubertal children might be geometrically similar. In older children, the height exponent declined monotonically to 0.5 (ie, HT^0.5 ) in 15+ year-olds, similar to the exponent observed in adults. UK children's height-adjusted WC revealed a "u" shaped curve with age that appeared to reach a minimum at peak-height velocity, different for boys and girls. Comparing the WC of two populations (UK versus Colombian 14-15-year-old children) identified that the gap in WC between the countries narrowed considerably after scaling for height.

CONCLUSIONS

Scaling children's WC for differences in height using allometric modeling reveals new insights into the growth and development of children's WC, findings that might well have been be overlooked if body size/height had been ignored.

Variation in Responses to Sprint Training in Male Youth Athletes: A Meta-analysis

The trainability of youths and the existence of periods of accelerated adaptation to training have become key subjects of debate in exercise science. The purpose of this meta-analysis was to characterise youth athletes' adaptability to sprint training across PRE-, MID-, and POST-peak height velocity (PHV) groups. Effect sizes were calculated as a measure of straight-line sprinting performance with studies qualifying based on the following criteria: (a) healthy male athletes who were engaged in organised sports; (b) groups of participants with a mean age between 10 and 18 years; (c) sprint training intervention duration between 4 and 16 weeks. Standardised mean differences showed sprint training to be moderately effective (Effect size=1.01, 95% confidence interval: 0.43-1.59) with adaptive responses being of large and moderate magnitude in the POST- (ES=1.39; 0.32-2.46) and MID- (ES=1.15; 0.40-1.9) PHV groups respectively. A negative effect size was found in the PRE group (ES=-0.18; -1.35-0.99). Youth training practitioners should prescribe sprint training modalities based on biological maturation status. Twice weekly training sessions should comprise up to 16 sprints of around 20 m with a work-to-rest ratio of 1:25 or greater than 90 s.

A comparison of four typical green exercise environments and prediction of psychological health outcomes

Aims:

‘Green exercise’ (GE) is physical activity while simultaneously being exposed to nature. GE comprises three physical components: the individual, the exercise and the environment, and one processes component encompassing a range of psychological and physiological processes. Previous research has consistently shown affective benefits of GE compared to equivalent non-GE. Investigating the possibility of optimum GE environments may help maximise health benefits. The aim of this study was to compare affective outcomes of GE participation between four different typical GE environments (beach, grasslands, riverside, heritage), and further examine influences of several physical component–related variables and one processes component–related variable, on these outcomes.

Method:

Participants ( N = 331) completed questionnaires before and after a 5km run, at one of four parkrun event locations.

Results:

Self-esteem (Δ = 1.61, 95% confidence interval (CI) = (1.30, 1.93)), stress (Δ = −2.36, 95% CI = (−3.01, −1.71)) and mood (Δ = −5.25, 95% CI = (−7.45, −3.05)) all significantly improved from pre- to post-run ( p < .05). Improvements in these measures were not significantly different between environments. Several component-related variables significantly predicted these improvements, accounting for 9% of self-esteem improvement, 1.6% of perceived stress improvement, and 9.5% of mood improvement.

Conclusion:

GE offers accessible provision for improving acute psychological wellbeing. Although nature-based exercise environments can facilitate affective outcomes, the overall type of nature may be less critical. Other characteristics of the individual, exercise and environment can significantly influence attainment of psychological GE benefits. However, the results support a greater importance of the processes component in attaining previously reported affective outcomes.

A cross-cultural comparison of body composition, physical fitness and physical activity between regional samples of Canadian and English children and adolescents

OBJECTIVES

Cross-cultural comparisons in children's body composition, health-related fitness and physical activity (PA) are rare due to a shortage of comparable data, but such comparisons may help avert worrying global prevalence in childhood obesity, and declining fitness and PA.

METHODS

We drew samples of Canadian and English children (10 years, n=1630, 50% boys) and adolescents (15 years, n=1406, 56% boys) from three separate, regional studies that conducted comparable school-based assessments (2006-2011). For each age-sex group, we assessed between-country differences for body composition (mass, height, BMI, waist circumference), cardiorespiratory fitness (CRF; 20 m shuttle run test), strength (handgrip) and self-reported PA. We used multiple regression to investigate whether between-country differences in fitness were explained by body composition and PA.

RESULTS

At any age, Canadian boys and girls were taller, heavier, and had greater BMIs and waist circumferences. English children had higher CRF than Canadians, which was explained by differences in body composition and PA. Canadian children were significantly stronger, partly due to greater body size. There were no between-country differences in adolescent boys. Canadian adolescent girls reported more PA than their English counterparts, but neither PA nor body size explained why Canadian adolescent girls had greater CRF or strength.

CONCLUSION

Future cross-cultural studies of PA should include indices of growth and fitness to better understand the relationship between intricate differences in PA and health outcomes.

The effect of playground- and nature-based playtime interventions on physical activity and self-esteem in UK school children

School playtime provides opportunities for children to engage in physical activity (PA). Playground playtime interventions designed to increase PA have produced differing results. However, nature can also promote PA, through the provision of large open spaces for activity. The purpose of this study is to determine which playtime interventions are most effective at increasing moderate-to-vigorous physical activity (MVPA) and if this varies by school location. Fifty-two children from an urban and rural school participated in a playground sports (PS) and nature-based orienteering intervention during playtime for one week. MVPA was assessed the day before and on the final day of the interventions using accelerometers. Intervention type (p < 0.05) and school location (p < 0.001) significantly influenced MVPA; with PS increasing MVPA more than nature-based orienteering. Urban children seemed to respond to the interventions more positively; however, differences in baseline MVPA might influence these changes. There was a positive correlation for fitness and MVPA during PS (r = 0.32; p < 0.05), but not nature-based orienteering (p > 0.05). The provision of PS influences PA the most; however, a variety of interventions are required to engage less fit children in PA.

Differential responses of adiposity, inflammation and autonomic function to aerobic versus resistance training in older adults

BACKGROUND

Increased body fat, autonomic dysfunction and low-grade chronic inflammation are interrelated risk factors implicated in the etiology of several chronic conditions normally presented by older adults.

OBJECTIVE

This study aims to assess the effectiveness of different training protocols on reducing body fat, improving autonomic function, and decreasing low-grade systemic inflammation in community-dwelling elderly adults.

METHODS

Fifty participants (11 men, 68±5.5years) were randomly allocated into resistance or aerobic training or control groups. Evaluations were done at baseline and following the 8-month intervention period on their body composition (assessed by DXA), inflammatory biomarkers (high-sensitivity C-reactive protein [hs-CRP], tumor necrosis-alpha [TNF-α], interferon-gamma [IFN-γ], interleukins-6 and -10 [IL-6, IL-10]), lipoproteic profile, fasting glycemia, blood pressure, heart rate variability (HRV; frequency and time domains) and aerobic fitness (assessed by six-minute walk distance [6MWD]). A paired t-test was used to detect changes (%Δ=[(post-test score-pretest score)/pre-test score]×100) within groups, while between-group differences were analyzed using the one-way ANOVA or General Linear Models.

RESULTS

A significant change (Δ%) both in total (-5.4±6.3% and -3.3±2.9%, respectively) and central body fat (8.9±11.3% and -4.8±4.5%) was observed in resistance and aerobic training groups, respectively; along with a change in resting systolic and diastolic blood pressures (-9.2±9.8% and -8.5±9.6%), heart rate (-4.6±6.5%), hs-CRP (-18.6±60.6%), and 6MWD (9.5±6.9%) in response to aerobic training.

CONCLUSIONS

The present findings provide further evidence for the benefits of aerobic and resistance training on reducing body fat. Aerobic training was demonstrated to reduce hs-CRP and blood pressure in community-dwelling elderly participants with no serious medical conditions.

A randomised control trial of physical activity in a perceived environment on self-esteem and mood in UK adolescents

This study assessed whether exercising whilst viewing natural or built scenes affected self-esteem (SE) and mood in adolescents. Twenty-five adolescents participated in three exercise tests on consecutive days. A graded exercise test established the work rate equivalent to 50% heart rate reserve for use in subsequent constant load tests (CLTs). Participants undertook two 15-min CLTs in random order viewing scenes of either natural or built environments. Participants completed Rosenberg's SE scale and the adolescent profile of mood states questionnaire pre- and post-exercise. There was a significant main effect for SE (F(1) = 6.10; P < 0.05) and mood (F(6) = 5.29; P < 0.001) due to exercise, but no effect of viewing different environmental scenes (P > 0.05). Short bouts of moderate physical activity can have a positive impact on SE and mood in adolescents. Future research should incorporate field studies to examine the psychological effects of contact with real environments.

Pacing strategy in schoolchildren differs with age and cognitive development

PURPOSE

The study's purpose was to examine differences in pacing strategy between schoolchildren of different age, gender, and stage of cognitive development.

METHODS

Schoolchildren (n = 106) from four age groups (5-6, 8-9, 11-12, and 14 yr) participated in this study. Each schoolchild completed four conservation tasks to evaluate his or her Piagetian stage of cognitive development. Each schoolchild then performed a best-effort running task on a 150-m running track that was video recorded to analyze pace at 5% increments. The length of the run was varied for each age group to ensure that all schoolchildren were running for approximately 4 min (5-6 yr = 450 m, 8-9 yr = 600 m, 11-12 yr = 750 m, and 14 yr = 900 m).

RESULTS

Differences in pacing strategy were found between schoolchildren of different age (P < 0.0001), gender (P < 0.0001), and cognitive development (P < 0.0001). Pacing differences were also found between age groups after controlling for cognitive development (P < 0.001), between cognitive abilities after controlling for age (P < 0.01), and between genders after controlling for both age (P < 0.0001) and cognitive ability (P < 0.0001).

CONCLUSIONS

Younger schoolchildren with less advanced cognitive development exhibited a negative pacing strategy indicating an inability to anticipate exercise demand. Older schoolchildren at a more advanced stage of cognitive development exhibited a more conservative U-shaped pacing strategy characterized by faster running speeds during the first 15% and last 20% of the run. Anticipatory pacing strategy seems to be related to both the age and cognitive development of schoolchildren.

Metabolic syndrome, physical activity and cardiac autonomic function

BACKGROUND

Our primary aim was to investigate the associations that components of metabolic syndrome and physical activity have with cardiac autonomic nervous system activity as estimated by heart rate variability (HRV) in young adults free of metabolic abnormalities. We also aimed to identify predictors of 3-year changes in HRV.

METHODS

Physical activity was assessed annually in 163 healthy participants over 3 years (2008-2010). Components of metabolic syndrome measured annually were; waist circumference, systolic blood pressure, high-density lipoprotein, triglycerides, glucose, and C-reactive protein. A linear mixed regression model was used to assess associations between HRV, metabolic syndrome components and physical activity. Linear regression was used to identify predictors of changes in HRV.

RESULTS

 Metabolic syndrome components were negatively associated with HRV indices and higher heart rate, while physical activity was associated with higher HRV and lower heart rate. Physical activity and inflammation were predictors of positive and negative changes in HRV indices, respectively.

CONCLUSIONS

 In participants without significant metabolic abnormalities, metabolic syndrome components were still associated with less favourable HRV profiles. Physical activity and inflammation were both able to predict changes in HRV, albeit in different directions. It appears that the process of autonomic dysfunction starts at a young age and may be mediated in part by inflammation. Metabolic syndrome prevalence is increasing in younger populations; promoting the metabolic and autonomic benefits of exercise remains imperative.

Centile curves and normative values for the twenty metre shuttle-run test in English schoolchildren

The aim of this study was to provide normative data for performance on the 20 m shuttle-run test of cardiorespiratory fitness in English schoolchildren. A total of 7366 10-16 year olds completed the 20 m shuttle-run test. We expressed performance as the number of shuttles completed, test score (shuttles and levels) and estimated peak oxygen consumption (VO2peak). We calculated descriptive statistics for each age-sex group to construct percentile curves and tables. To assess the cardiorespiratory fitness of our sample, we calculated the number of participants who fell below proposed cut-offs for low cardiorespiratory fitness based on either completed shuttles or VdotO2peak. These cut-offs did not agree in terms of frequency of classification. The classification based on estimated VO2peak suggested low fitness was more prevalent in males and that the incidence of low fitness increased with age in both sexes. These are the first normative data for shuttle-run performance in English youth and can now be used to interpret data from this cardiorespiratory fitness test. The two cut-offs used for low fitness did not agree and future research should establish a cut-off for test performance which can predict present or future ill-health.

Changes in cardiorespiratory fitness in cardiac rehabilitation patients: a meta-analysis

BACKGROUND/OBJECTIVES

Improving patients' cardiorespiratory fitness is an important therapeutic outcome in cardiac rehabilitation. The ability of cardiac rehabilitation to reduce mortality and morbidity has been evidenced through several meta-analyses. Whether cardiac rehabilitation can increase cardiorespiratory fitness and which factors may influence such gains are less well quantified.

METHODS

We performed detailed literature searches of electronic databases and manually searched papers concerning changes in cardiorespiratory fitness in cardiac rehabilitation patients. We performed random-effects meta-analysis of mean improvements in cardiorespiratory fitness and subgroup analyses to determine potential sources of heterogeneity.

RESULTS

Data from 31 studies produced 48 groups (n=3827) with a mean improvement of 1.55 (95% CI 1.21-1.89) METs, (p<0.001); equivalent to standardised effect size of ES=0.97 (95% CI 0.80-1.13). As this value was highly heterogeneous (Q=852, p<0.001) we performed subgroup analyses on the effect size data. Gains in fitness were highest in patients receiving >36 exercise sessions in studies where fitness was assessed using the Naughton Protocol. Patient characteristics associated with the highest fitness gains were age (being young) and sex (being male training in a male-only exercise group). Changes in fitness were unrelated to programme type (comprehensive or exercise-only), duration or study design. There was no association with patient's baseline fitness levels.

CONCLUSION

This is the first meta-analysis of changes in cardiovascular fitness in cardiac rehabilitation patients and shows clinically significant improvements in a large sample of patients from a variety of rehabilitation programmes. This analysis helps describe the characteristics of cardiac rehabilitation programmes which can increase patients' cardiorespiratory fitness.

Aerobic fitness and mode of travel to school in English schoolchildren

PURPOSE

Cycling to school is positively associated with aerobic fitness in Danish schoolchildren and adolescents. The aim of the present study was to determine whether a positive association exists between active travel and aerobic fitness in English schoolchildren, where cycling to school is rare.

METHODS

Participants (n = 6085, 47% girls, aged 10.0-15.9 yr) were recruited as part of the East of England Healthy Hearts study. Mass and stature were measured, and body mass index (BMI) was calculated. Aerobic fitness was assessed using the 20-m shuttle run test (20-mSRT); mode of travel to school and physical activity (PA) were assessed by a questionnaire. Differences in BMI, PA, and fitness by travel mode were assessed by ANOVA and ANCOVA. Participants were categorized as "fit" or "unfit" on the basis of existing cutoffs related to adult health. Logistic regression was applied to calculate age, BMI, and PA-adjusted odds of being classified as fit according to travel mode.

RESULTS

Walking was the most common travel mode to school (50%), and cycling was least frequent (8%). Walkers and cyclists of both sexes were significantly fitter than passive transport users, even after controlling for PA. Walking and cycling were associated with an increased likelihood of being categorized as fit in boys and girls. After adjustment for PA, this association remained significant only in girls. No association was observed between travel mode and BMI.

CONCLUSIONS

These data confirm findings from countries where cycling is very common in showing that cycling to school is positively associated with aerobic fitness. This study adds to the existing literature by showing that walkers and cyclists are more likely to be classified as fit using recognized cut points. Those who walk and cycle to school may, therefore, be at reduced risk for developing chronic diseases in adulthood.

Ten year secular declines in the cardiorespiratory fitness of affluent English children are largely independent of changes in body mass index

Secular changes in body mass index (BMI) and cardiorespiratory fitness (20 m shuttle-run test performance) were assessed in 10-year-old children from an affluent area of England in 1998 (n = 303; 158 boys and 145 girls) and 2008 (n = 315; 158 boys and 157 girls). Girls' BMI did not change over the 10 year period. There was a significant increase in boys' BMI (p = 0.02). Cardiorespiratory fitness declined significantly (p<0.001) in both boys (7%) and girls (9%). This study shows a large and worrying decline in cardiorespiratory fitness in children from an affluent area of England.

Association between RR interval and high-frequency heart rate variability acquired during short-term, resting recordings with free and paced breathing

High-frequency (HF) oscillations in RR interval from 0.15-0.40 Hz are widely accepted as a measure of cardiac vagal outflow but the HF/RR relationship appears complex, particularly with longer RR intervals. The aim of this study was to evaluate the HF/RR interval relationship during free and paced breathing. HF power and mean RR interval length were recorded in 150 men and 120 women (mean age 34.5 +/- 11.4) during 5 min of supine rest with either free or paced (12 cycles min(-1)) breathing. Linear and quadratic models were used to assess the relationship between RR interval and the natural logarithm of HF power (lnHF). The RR interval length at which there was no further increase in lnHF was determined as the deflection point. ANCOVA was used to determine differences in the linear regression slopes for lnHF/RR with paced or free breathing. With free breathing (n = 131), the adjusted R(2) was similar between linear (15.3%) and quadratic (17.5%) fits and saturation of lnHF occurred within the recorded RR interval range (1326 ms). With paced breathing (n = 139), adjusted R(2) values were again similar between linear (22.4%) and quadratic (23.2%) fits. The deflection point was outside the range of recorded RR intervals at 1458 ms. ANCOVA showed a significant difference in the slope of the lnHF/RR regression lines between free and paced breathing. The lnHF/RR relationship is weaker when derived from between-subject recordings than from repeated within-subject samples. lnHF/RR showed evidence of saturation at approximately 45 bpm with free breathing. With paced breathing, a deflection in lnHF was found outside the recorded RR interval range ( approximately 41 bpm). Paced breathing creates a stronger lnHF/RR relationship. The slope of the lnHF/RR regression line with paced breathing is significantly different from that observed with free breathing. It appears that lnHF is a valid index of vagal outflow, except in subjects with very low heart rates. Paced breathing data collection protocols appear preferable.

Normative values, reliability and sample size estimates in heart rate variability

HRV (heart rate variability) is a non-invasive maker of cardiac autonomic modulation utilized in many hundreds of scientific studies each year. The reliability of heart rate variability has been frequently investigated yet remains poorly quantified. Assessing the reliability of a measure that assesses dynamic physiological processes and shows large between- and within-subject variation is a complex task. In this issue of Clinical Science, Pinna and co-workers provide excellent insight into the test-retest reliability of commonly used HRV indices and put the values obtained into context by comparing them with levels of between-subject variation and by producing sample size estimates.