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Despite a growing evidence base on the effectiveness of community-based physical activity interventions for mental health, there is a lack of studies that focus on those affected by severe mental illness (SMI), who often experience poorer physical health, and are less physically active than the wider population. The use of peer support groups in this context is also understudied, despite benefits being documented in other contexts. This study examined the impact and process of a nationwide project to embed physical activity into peer support groups for those affected by SMI. Following the embedding of physical activity within peer support groups, interviews and focus groups were conducted to explore the experiences of those involved with the project and analysed using reflexive thematic analysis. The key findings related to: 1) the social aspects of embedding physical activity in the groups; 2) the focus on peer support and informal physical activity (rather than organised sport) being beneficial; 3) doing things differently and lessons to learn; and 4) the impact of the COVID-19 pandemic. Overall, we found that peer support is an important feature to include in projects encouraging those severely affected by mental illness to become more physically active.

Prior self-control exertion is consistently reported to cause decrements in subsequent physical performance. However, research into the explanatory mechanisms underpinning the effect is limited and has not been assessed under a meta-analytical lens. Therefore, the present study reports a meta-analysis examining the effects of self-control exertion on subsequent physical performance, as well as the mechanisms underpinning the effect.\ud \ud A systematic search of relevant databases was conducted to identify studies that utilized the sequential task paradigm, involving self-control manipulations lasting 30 minutes or less, and examined an aspect of physical performance. Random effects meta-analysis demonstrated that the prior exertion of self-control resulted in a statistically significant medium sized negative effect of prior self-control exertion on subsequent physical performance (g = −0.55). Further analysis revealed a small increase in initial perceptions of pain (g = 0.18) and a medium sized reduction in self-efficacy (g = −0.48), while motivation and RPE were unaffected following the exertion of self-control.\ud \ud The present study provides a novel insight into the mechanisms underpinning the effects of prior self-control exertion on subsequent physical performance. Initial perceptions of pain and self-efficacy appear important mechanisms and thus could be targeted in future interventions aimed at attenuating the effects of self-control exertion to enhance subsequent physical performance.

Exercise duration may influence the acute effects on cognition. However, only one study to date has explored the dose-response relationship between exercise duration and cognition in adolescents. Thus, the purpose of this study was to investigate the effect of differing durations of high-intensity intermittent running on cognition in adolescents. Thirty-eight adolescents (23 girls) completed three trials separated by 7 d: 30 min exercise, 60 min exercise, and rest, in a randomised crossover design. The exercise was a modified version of the Loughborough Intermittent Shuttle Test (LIST), which elicited high-intensity intermittent exercise. Cognitive function tests (Stroop test, Sternberg paradigm, Flanker task) were completed 30 min pre, immediately post, and 45 min post exercise. Response times on the incongruent level of the Flanker task improved to a greater extent 45 min following the 30 min LIST, compared to rest (p = 0.009). Moreover, response times improved to a greater extent on the three-item level of Sternberg paradigm 45 min following the 30 min LIST, compared to the 60 min LIST (p = 0.002) and rest (p = 0.013), as well as on the five-item level 45 min following the 30 min LIST, compared to the 60 min LIST (p = 0.002). In conclusion, acute exercise enhanced subsequent cognition in adolescents, but overall, 30 min of high-intensity intermittent running is more favourable to adolescents’ cognition, compared to 60 min.

This mixed-longitudinal prospective study examined the development of psychological characteristics of developing excellence in relation to the career progression of elite youth football players. In a 20-month period, 111 academy football players aged 11-16 completed the Psychological Characteristics of Developing Excellence Questionnaire (PCDEQ) on 1-5 occasions. This combination of single and repeated assessments resulted in a mixed-longitudinal sample of 226 completed PCDEQs. Players were then prospectively tracked, and their scholarship status assessed at follow-up, at age U17. Multilevel modelling revealed that coping with performance and developmental pressures scores increased with age, and that Category 1-2 academy scholars (4.35 ± 0.61) scored higher than Category 3-4 academy scholars (3.99 ± 0.67) and non-scholars (4.02 ± 0.78) (p .05). Evaluating performances and working on weaknesses scores increased with age for Category 1-2 academy scholars (U12-U14 vs. U15-U16 = 5.16 ± 0.48 vs. 5.38 ± 0.45), compared to non-scholars (U12-U14 vs. U15-U16 = 5.11 ± 0.59 vs. 5.03 ± 0.71) (p .05). Imagery use during practice and competition scores decreased with age (U12-U14 vs. U15-U16 = 4.45 ± 0.66 vs. 4.29 ± 0.70) (p .05). A blend of PCDEs may facilitate optimal career progression. Football academies should develop players' PCDEs, with a particular focus on developing their coping skills and their ability to realistically evaluate performances and work on weaknesses.

The Daily Mile is a popular physical activity initiative in primary schools, yet little is known regarding the activity patterns of children during The Daily Mile. Eighty children (10.4 ± 0.7 years) participated in The Daily Mile (20-min). Activity patterns were assessed using global positioning systems (total distance and age-specific speed zones), alongside heart rate. Cardiorespiratory fitness was assessed using the Multi-Stage Fitness Test. Participants covered a distance of 2511 ± 550 m during The Daily Mile, and heart rate was 163 ± 27 beats.min−1. Participants travelled the furthest distance, and were most intermittent, during the first 5 min (main effect of time, both p p p

The present study examined the metabolic responses to an acute bout of football and the overall and moderating role of physical fitness on these responses, in adolescents. Thirty-six adolescents (16 girls, 20 boys; 12.6±0.5 y) completed two trials (60-min football and 60-min seated rest) separated by 7-d. Capillary blood samples were taken at baseline (60-min prior to exercise/rest), immediately, 30- and 60-min post-exercise and 30-, 60- and 120-min following a standardised lunch (1.5-, 2- and 3-h post-exercise), for the determination of blood glucose and plasma insulin concentrations. The median split of distance covered on the multi-stage fitness test was used to define high- and low-fit groups. Overall plasma insulin tAUC following lunch was lower in high-fit participants compared to low-fit (high-fit: 3784.2±1653.1 pmol·L−1x120min, low-fit: 6457.3±3290.7 pmol·L−1x120min; p0.05). Football reduced blood glucose concentration 1-h post-exercise compared to control (exercise: 3.8±0.6 mmol·L−1, rest: 4.6±0.8 mmol·L−1; p0.05). Blood glucose tAUC was not affected by exercise or physical fitness (p>0.05). These data emphasise the importance of physical fitness for metabolic health in adolescents, as well as the utility of football as a popular form of games-based activity for improving glucose regulation.

The authors thank the study participants and collaborators on the individual studies that provided data for this pooled IPD analysis., Objectives To determine if subpopulations of students benefit equally from school-based physical activity interventions in terms of cardiorespiratory fitness and physical activity. To examine if physical activity intensity mediates improvements in cardiorespiratory fitness. Design Pooled analysis of individual participant data from controlled trials that assessed the impact of school-based physical activity interventions on cardiorespiratory fitness and device-measured physical activity. Participants Data for 6621 children and adolescents aged 4-18 years from 20 trials were included. Main outcome measures Peak oxygen consumption (VO2Peak mL/kg/min) and minutes of moderate and vigorous physical activity. Results Interventions modestly improved students’ cardiorespiratory fitness by 0.47 mL/kg/min (95% confidence interval 0.33 to 0.61), but the effects were not distributed equally across subpopulations. Girls and older students benefited less than boys and younger students, respectively. Students with lower levels of initial fitness, and those with higher levels of baseline physical activity benefitted more than those who were initially fitter and less active, respectively. Interventions had a modest positive effect on physical activity with approximately one additional minute per day of both moderate and vigorous physical activity. Changes in vigorous, but not moderate intensity, physical activity explained a small amount (~5%) of the intervention effect on cardiorespiratory fitness. Conclusions Future interventions should include targeted strategies to address the needs of girls and older students. Interventions may also be improved by promoting more vigorous intensity physical activity. Interventions could mitigate declining youth cardiorespiratory fitness, increase physical activity, and promote cardiovascular health if they can be delivered equitably and their effects sustained at the population level.

The present study examined if elite youth male association football (soccer) players aged 8–19 y (n = 2,875) from the English talent development system, who ultimately achieved professional status differed in stature, body mass, and physical performance (20-m sprint speed, slalom agility speed, vertical counter-movement jump with arm swing jump height, multistage fitness test distance) compared with their non-professional peers. The study also examined the longitudinal pattern of development of stature, body mass, and physical performance, and if this was different between future professionals and non-professionals, while considering the effects of playing position. Multilevel modeling of the 8,898 individual (player-occasion) data points suggested that from age 12.0, the future professionals performed better in a vertical counter-movement jump with arm swing test and slalom agility test than future non-professionals, and improved at a faster rate, so that by age 18.0 the differences in vertical counter-movement jump with arm swing and slalom agility performance were 1.7 cm (p < 0.001, d = 0.3) and 0.14 s (p < 0.001, d = 0.5), respectively. In addition, future professionals were faster (by 0.02–0.04 s on the 20-m sprint, p < 0.001, d = 0.2) and ran further in the multistage fitness test (by 47 m, p = 0.014, d = 0.2) than future non-professionals throughout their development, but there were no differences in stature or body mass during development between the groups. Whereas, multistage fitness test performance improved linearly with age, the development of all other physical characteristics was non-linear. There were inter-individual differences in the development of all characteristics, and there were differences between playing positions in the development of all characteristics. Thus, in summary, future professionals jump higher, are more agile, faster, and more endurance fit than future non-professionals as they age, and the pattern of development is different in professionals and non-professionals for vertical jumping and slalom agility performance.

Postprandial glycaemia and insulinaemia are important risk factors for type 2 diabetes. The prevalence of insulin resistance in adolescents is increasing, but it is unknown how adolescent participant characteristics such as BMI, waist circumference, fitness and maturity offset may explain responses to a standard meal. The aim of the present study was to examine how such participant characteristics affect the postprandial glycaemic and insulinaemic responses to an ecologically valid mixed meal. Data from the control trials of three separate randomised, crossover experiments were pooled, resulting in a total of 108 participants (fifty-two boys, fifty-six girls; aged 12·5 (SD 0·6) years; BMI 19·05 (SD 2·66) kg/m2). A fasting blood sample was taken for the calculation of fasting insulin resistance, using the homoeostatic model assessment of insulin resistance (HOMA-IR). Further capillary blood samples were taken before and 30, 60 and 120 min after a standardised lunch, providing 1·5 g/kg body mass of carbohydrate, for the quantification of blood glucose and plasma insulin total AUC (tAUC). Hierarchical multiple linear regression demonstrated significant predictors for plasma insulin tAUC were waist circumference, physical fitness and HOMA-IR (F(3,98) = 36·78, P < 0·001, adjusted R2 = 0·515). The variance in blood glucose tAUC was not significantly explained by the predictors used (F(7,94) = 1·44, P = 0·198). Significant predictors for HOMA-IR were BMI and maturity offset (F(2,102) = 14·06, P < 0·001, adjusted R2 = 0·021). In summary, the key findings of the study are that waist circumference, followed by physical fitness, best explained the insulinaemic response to an ecologically valid standardised meal in adolescents. This has important behavioural consequences because these variables can be modified.

High-intensity intermittent exercise (HIIE) is a potential intervention to manage hyperglycaemia and insulin resistance in adolescents. The aim of this study was to determine the optimum duration of HIIE to reduce postprandial glycaemic and insulinaemic responses in adolescents and the longevity of the response. Thirty-nine participants (12.4 &plusmn, 0.4 year) completed a 30- and 60-min exercise trial (Loughborough Intermittent Shuttle Test) and a rested control trial in a randomised crossover design. Capillary blood samples were taken at baseline, immediately and 1-h post‐exercise, and 30, 60 and 120 min following a standardised lunch (day one) and a standardised breakfast 24-h post-exercise. Plasma insulin total area under the curve (tAUC) following lunch was lower following 60-min HIIE (21754 &plusmn, 16861 pmol&middot, L&minus, 1 &times, 120 min, p = 0.032) and tended to be lower following 30-min HIIE (24273 &plusmn, 16131 pmol&middot, 120 min, p = 0.080), when compared with the resting condition (26931 &plusmn, 21634 pmol&middot, 120 min). Blood glucose concentration was lower 1-h post-exercise following 30-min HIIE (3.6 &plusmn, 0.6 mmol&middot, 1) when compared to resting (4.1 &plusmn, 0.9 mmol&middot, 1, p = 0.001). Blood glucose and plasma insulin concentration did not differ across trials on day two. Shorter bouts of HIIE (30-min), as well as a 60-min bout, reduced the postprandial insulinaemic response to lunch, an ecologically valid marker of insulin sensitivity. As the beneficial effects of HIIE were limited to 3 h post-exercise, adolescents are recommended to engage daily HIIE to enhance metabolic health.

Background: The COVID-19 pandemic is expected to negatively impact the mental health of young people and students in particular, yet there is lack of prospective longitudinal data quantifying such changes. This study examines the mental health and movement behaviours, and the associations between the changes in mental health and movement behaviours, of UK university students during the COVID-19 pandemic. Methods: A total of 214 students enrolled in a longitudinal cohort study (mean age = 20⸱0 years; males = 28⸱0%, females = 72⸱0%) at an East Midlands UK University. Participants completed a self-report, online survey on four occasions; twice before (14/10/2019; T1 and 28/01/2020; T2) and twice during the UK government enforced ‘lockdown’ (20/03/2020; T3 and 27/04/2020; T4). Mental wellbeing and perceived stress were measured using the Warwick-Edinburgh Mental Wellbeing Scale and Cohen’s Perceived Stress Scale, respectively. Repeated measures ANOVA was used to assess for changes in variables over time, whilst correlation analysis tested for associations. Findings: During the first 5 weeks of ‘lockdown’ mental wellbeing and physical activity decreased ((F (2⸱2, 465⸱0) = 6⸱6, p < ⸱0010 and (F (2⸱7, 591⸱0) = 4⸱8, p < ⸱010 respectively)). Meanwhile, perceived stress and time spent in sedentary behaviour significantly increased ((F (2⸱5, 536⸱2) = 94⸱0, p < ⸱0050 and (F (2⸱7, 578⸱9) = 41⸱2, p < ⸱0001 respectively)). The changes in mental wellbeing and stress were not associated with gender or pre-lockdown mental health, nor were they associated with changes physical activity. A positive association was found between the change in perceived stress and the change in sedentary behaviour (r = ⸱18, p < ⸱010). Interpretation: The COVID-19 pandemic is having detrimental effects on the mental health and movement behaviour of university students in the UK. However, these two constructs seem to be changing independently of one another. Funding: The authors received no financial support for the research, authorship, and/or publication of this article. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: Ethical approval was granted by the Science and Technology College Research Ethics Committee of the University.

The study aimed to quantify the measurement error / reliability of a musculoskeletal profiling test battery administered in young, elite academy soccer players, and to examine if the order in which the test battery was administered, and who it was administered by, influenced reliability. Players (n = 75; age 12-20 years; stature 1.47-1.95 m; body mass 36-89 kg) from U-12 to U-23 age groups were assigned to either: 1) intra-rater-fixed order; 2) intra-rater-non-fixed order; 3) inter-rater-fixed order; or, 4) inter-rater-non-fixed order groups. On two separate occasions separated by 3 to 7 days, 12 raters conducted a musculoskeletal profiling test battery comprising 10 tests (Supine Medial Hip Rotation, Supine Lateral Hip Rotation, Hamstring 90/90, Prone Medial Hip Rotation [degrees]; Combined Elevation, Thoracic Rotation, Weight-Bearing Dorsiflexion, Y-Balance [centimetres]; Beighton, Lumbar Quadrant [categorical]). The measurement error / reliability for tests measured in degrees and centimetres was evaluated using the intraclass correlation (relative reliability), coefficient of variation and ratio limits of agreement (absolute reliability). Intraclass correlations varied from 0.04 ("poor") to 0.95 ("excellent"), coefficient of variation from 2.9 to 43.4%, and the ratio limits of agreement from 1.058 (*/÷ 1.020) to 2.026 (*/÷ 1.319) for the tests measured in degrees and centimetres. The intraclass correlation, coefficient of variation and ratio limits of agreement were smallest for five out of eight tests measured in degrees and centimetres when the tests were administered in an intra-rater-fixed test order. These findings emphasise that different testing methods, and the administration of a musculoskeletal profiling test battery using a less than optimal design, will influence measurement error and hence test reliability. These observations need to be considered when investigating musculoskeletal function and age, injury, training or asymmetry in young, elite academy soccer players.

Background: An acute bout of exercise elicits a beneficial effect on subsequent cognitive function in adolescents. The effect of games-based activity, an ecologically valid and attractive exercise model for young people, remains unknown; as does the moderating effect of fitness on the acute exercise-cognition relationship. Therefore, the aim of the present study was to examine the effect of games-based activity on subsequent cognition in adolescents, and the moderating effect of fitness on this relationship.\ud \ud Methods: Following ethical approval, 39 adolescents (12.3 ± 0.7 year) completed an exercise and resting trial in a counterbalanced, randomised crossover design. During familiarisation, participants completed a multi-stage fitness test to predict VO2 peak. The exercise trial consisted of 60-min games-based activity (basketball), during which heart rate was 158 ± 11 beats∙min−1. A battery of cognitive function tests (Stroop test, Sternberg paradigm, trail making and d2 tests) were completed 30-min before, immediately following and 45-min following the basketball.\ud \ud Results: Response times on the complex level of the Stroop test were enhanced both immediately (p = 0.021) and 45-min (p = 0.035) post-exercise, and response times on the five item level of the Sternberg paradigm were enhanced immediately post-exercise (p = 0.023). There were no effects on the time taken to complete the trail making test or any outcome of the d2 test. In particular, response times were enhanced in the fitter adolescents 45-min post-exercise on both levels of the Stroop test (simple, p = 0.005; complex, p = 0.040) and on the three item level of the Sternberg paradigm immediately (p = 0.017) and 45-min (p = 0.008) post-exercise.\ud \ud Conclusions: Games-based activity enhanced executive function and working memory scanning speed in adolescents, an effect particularly evident in fitter adolescents, whilst the high intensity intermittent nature of games-based activity may be too demanding for less fit children.

Goto, H, Morris, JG, and Nevill, ME. Influence of biological maturity on the match performance of 8- to 16-year-old, elite, male, youth soccer players. J Strength Cond Res 33(11): 3078-3084, 2019-The aim of this study was to examine the influence of biological maturity on match performance in elite, youth, male soccer players. The participants were 80 Premier League Academy outfield players (8-16 years old). Biological maturity was determined by calculating estimated chronological age at peak height velocity. The U9 and U10 squads played 6-a-side and the U11-U16 squads played 11-a-side interacademy matches. All matches were analyzed using a 1-Hz global positioning system (SPI Elite™, GPSports, Canberra, Australia) with squad-specific speed zones, which were calculated based on 5-m flying sprint speed in the last 5 m of 10-m sprint test. In the U9/U10s, earlier maturers were given a longer pitch time by coaches (∼4 minutes per match; p = 0.029) and covered a greater total distance (∼9%; ∼400 m; p = 0.037) and a greater distance by walking (∼13%; ∼100 m; p = 0.024) and jogging (∼12%; ∼200 m; p = 0.014) during a match compared with later maturers. In the U13/U14s, earlier maturers covered a greater distance per hour of a match by high-speed running compared with later maturers (∼25%; ∼130 m; p = 0.028) and spent a longer percentage of time in high-speed running during a match compared with later maturers (3.4% vs. 2.7%, p = 0.034). Thus, coaches should take care to provide all players with a similar pitch time and should be aware in the talent identification and development process, particularly with the U13/U14 age group, because maturity can influence high-speed match running performance.

This study longitudinally examined age-related changes in the match-running performance of retained and released elite youth soccer players aged 8-18 years. The effect of playing position on age-related changes was also considered. Across three seasons, 263 elite youth soccer players were assessed in 1-29 competitive matches (988 player-matches). For each player-match, total distance and distances covered at age group-specific speed zones (low-speed, high-speed, sprinting) were calculated using 1 Hz or 5 Hz GPS. Mixed modeling predicted that match-running performance developed nonlinearly, with age-related changes best described with quadratic age terms. Modeling predicted that playing position significantly modified age-related changes (P

This study examined (1) the distances and speeds covered during match play for U11 to U16 English Premier League Academy players, (2) the differences in match performance between retained and released players and (3) the effect of calculating speed zones in different ways when analysing match performance. Eighty-one academy outfield players (10-16 years old), competing in 11-a-side matches, were analysed using a 1-Hz global positioning system with three speed zones (absolute, squad and individual). Pitch dimensions were 78.7 × 54.1 m (U11 and U12), 88.0 × 64.2 m (U13) and 100.8 × 68.2 m (U14-U16). Match durations were 20 min × 2 + 15 min × 2 or 25 min × 3 (U11), 25 min × 3 (U12 and U13) and 40 min × 2 (U14-U16). The matches were part of the regular series of inter-academy matches between Premier League Academies during a season. Completion of at least a half of the duration of a match in two separate matches (mean ± s = 3.1 ± 0.8 matches; range: 2-4 matches) was the criterion for inclusion in the study. Total match running distance increased with age from ~5700 (U11) to ~6700 m · h(-1) (U15) (P 0.01). Using the absolute speed zones, it was possible to discern differences in high-intensity (6.0 m · s(-1)) distance covered with age (U11: 29 m · h(-1), U16: 164 m · h(-1), P 0.01). Using the squad speed zones, it was possible to discern differences between retained and released players in the U11/U12s (moderate-speed running) and in the U15/U16s (walking, jogging and low-speed running) (P 0.01). Thus, total and high-intensity running distances increase with age, and walking, jogging, low-speed running and moderate-speed running distances are greater in retained than in released players and these differences are best identified through the use of absolute and squad speed zones, respectively.

During puberty young people undergo significant hormonal changes which affect metabolism and, subsequently, health. Evidence suggests there is a period of transient pubertal insulin resistance, with this effect greater in girls than boys. However, the response to everyday high and low glycaemic index (GI) meals remains unknown. Following ethical approval, forty adolescents consumed a high GI or low GI breakfast, in a randomised cross-over design. Capillary blood samples were taken during a 2-h postprandial period, examining the glycaemic and insulinaemic responses. Maturity offset and homoeostatic model assessment (HOMA) were also calculated. The glycaemic response to the breakfasts was similar between boys and girls, as shown by similar peak blood glucose concentrations and incremental AUC (IAUC) following both high and low GI breakfasts (all P>0·05). Girls exhibited a higher peak plasma insulin concentration 30 min post-breakfast following both high GI (P=0·043, g=0·69) and low GI (P=0·010, g=0·84) breakfasts, as well as a greater IAUC following high GI (P=0·041, g=0·66) and low GI (P=0·041, g=0·66) breakfasts. HOMA was positively correlated with the insulinaemic responses (all PP=0·037). The findings of the present study suggest that pubertal insulin resistance affects the postprandial insulinaemic responses to both high and low GI meals. Specifically, girls exhibit a greater insulinaemic response than boys to both meals, despite similar glycaemic responses. This study is the first to report the glycaemic and insulinaemic responses to everyday meals in boys and girls, supporting the recommendation for young people to base their diet on low GI carbohydrates.

The purpose of this study was to investigate the effect of accumulating 60 min of exercise on endothelial function and triacylglycerol concentrations following the ingestion of a high-fat breakfast and lunch in 14 adolescent boys (aged 12 to 14 years). Two, 2-day main trials (control and exercise) were completed in a counter-balanced, cross-over design. Participants were inactive on day 1 of the control trial but on day 1 of the exercise trial completed 6 × 10 min runs at 70% of peak oxygen uptake, spread over the day. On day 2, triacylglycerol concentrations and flow-mediated dilation (FMD) were measured prior to, and following, ingestion of the high-fat meals. In the control trial, FMD was reduced by 30% and 33% (P 0.05). These results support the concept of accumulating physical activity for health in adolescents as the accumulated exercise attenuated the decline in FMD seen following the consumption of high-fat meals.

The validity and reliability of a battery of field-based performance tests was examined. The opinions of coaches, fitness professionals and players (n=170, 172 and 101 respectively) on the importance of performance testing were established using a questionnaire. On 2 occasions, separated by 7 days, 80 elite, young soccer players (mean±SD [and range]: age 13.2±2.6 [8.9-19.1] years; stature 1.59±0.18 m [1.32-1.91]; body mass 50.6±17.1 [26.5-88.7] kg) completed a battery of field-based tests comprised of heart rate response to a submaximal Multi-stage fitness test, 3 types of vertical jump, sprints over 10 and 20 m, and an agility test. Physical performance testing was considered important by coaches (97%), fitness professionals (94%) and players (83%). The systematic bias ratio and the random error components of the 95% ratio limits of agreement for the first and second tests, for the U9-U11 vs. U12-U14 vs. U15-U18 age groups, were [Systematic bias (*/÷ ratio limits)]: Heart rate (Level 5): 0.983 (*/÷ 1.044) vs. 0.969 (*/÷ 1.056) vs. 0.983 (*/÷ 1.055); Rocket jump: 0998 (*/÷ 1.112) vs. 0.999 (*/÷ 1.106) vs. 0.996 (*/÷ 1.093); 10 m sprint: 0.997 (*/÷ 1.038) vs. 0.994 (*/÷ 1.033) vs. 0.994 (*/÷ 1.038); Agility test: 1.010 (*/÷1.050) vs. 1.014 (*/÷1.050) vs. 1.002 (*/÷1.053). All tests, except heart rate recovery from the Multi-stage fitness test, were able to distinguish between different ability and age groups of players (p0.05). Thus, the field-test battery demonstrated logical and construct validity, and was shown to be a reliable and objective tool for assessing elite, young soccer players.

The extent to which aerobic processes contribute to energy supply during short duration sprint swimming is not known. Therefore, the energy contribution to a maximal 30 s fully tethered swim (FTS), and repeated 4 × 30 s high intensity semi-tethered swimming bouts (STS) with 30 s of passive rest at 95% of the 30 s FTS intensity was estimated in eight elite male swimmers. Blood lactate concentration and pH after the 4 × 30 s test were 12.1 ± 3.6 mmol/L and 7.2 ± 0.1, respectively. Accumulated oxygen demand was estimated to be 50.9 ± 9.6 mL/kg and 48.3 ± 8.4, 47.2 ± 8.5, 47.4 ± 8.3, and 45.6 ± 6.8 mL/kg for the 30 s FTS and 4 × 30 s bouts, respectively. Accumulated oxygen uptake was 16.6 ± 3.6 for the 30 s FTS and progressively increased during the 4 × 30 s bouts 12.2 ± 2.1, 21.6 ± 2.5, 22.8 ± 1.8, and 23.5 ± 2.0 mL/kg (P < 0.01). The estimated aerobic contribution therefore was 33 ± 8% for the 30 s FTS and 25 ± 4, 47 ± 9, 49 ± 8, 52 ± 9% for bouts 1-4 during the 4 × 30 s STS test (P < 0.01). The results underline the importance of aerobic energy contribution during single and repeated high intensity swimming, which should be considered when prescribing swimming training sets of this nature.

This study examined the effects of menstrual cycle phase (MCP) upon sprinting and recovery as well as upon metabolic responses to such exercise. Eight females performed a repeated 30-s sprint on a non-motorised treadmill interspersed with a 2-min rest in three phases of the MCP, follicular (low 17beta-estradiol and progesterone), just prior to ovulation (midcycle trial, highest 17beta-estradiol concentration and low progesterone) and in the luteal phase (high 17beta-estradiol and high progesterone). MCP was verified later by radioimmunoassay of 17beta-estradiol and progesterone. Peak power output (PPO) and mean power output (MPO) were unaltered (P0.05) due to MCP [PPO for sprint 1: 463 (18) W vs. 443 (15) W vs. 449 (18) W; PPO for sprint 2: 395 (17) W vs. 359 (16) W vs. 397 (17) W; MPO for sprint 1: 302 (15) W vs. 298 (13) W vs. 298 (14) W; MPO for sprint 2: 252 (10) W vs. 248 (10) W vs. 259 (12) W for follicular, midcycle and luteal trial, mean (SEM), respectively]. Similarly, percentage recovery of PPO and MPO (the PPO or MPO during sprint 2 expressed as a percentage of the PPO or MPO during sprint 1) was also unchanged (P0.05). Blood lactate, blood pH and plasma ammonia after sprinting and estimated plasma volume were also unaltered by MCP (P0.05). These findings suggest that hormonal fluctuations due to MCP do not interfere with maximal intensity whole body sprinting and the metabolic responses to such exercise.

The aim of the present study was to examine the combined effects of breakfast glycaemic index (GI) and a mid-morning bout of exercise on adolescents’ cognitive function. Participants were randomly allocated to a high or low GI breakfast group in a mixed research design, where each participant completed two experimental trials (exercise and resting). Forty-two adolescents (12.4±0.5 years old), undertook a bout of exercise (ten repeats of level one of the multi-stage fitness test; exercise trial) or continued to rest (resting trial) following consumption of either a high or low GI breakfast. A battery of cognitive function tests (visual search test, Stroop test and Sternberg paradigm) was completed 30 min before and 45 min following the exercise. Average heart rate during exercise was 170±15 beats.min-1. On the complex level of the Stroop test, response times improved across the morning following the low GI breakfast on both the exercise and resting trials, though the improvement was greatest on the exercise trial. However, response times only improved on the resting trial following the high GI breakfast (p = 0.012). On the 5 letter level of the Sternberg paradigm, response times improved across the morning following the low GI breakfast (regardless of exercise) and only on the exercise trial following the high GI breakfast (p = 0.019). The findings of the present study suggest that the combined effects of breakfast GI and exercise in adolescents depend upon the component of cognitive function examined. A low GI breakfast and mid-morning bout of exercise were individually beneficial for response times on the Sternberg paradigm, whereas they conferred additional benefits for response times on the Stroop test.

Purpose: To investigate whether a single session of intermittent games activity would reduce postprandial lipemia. Methods: Twelve male volunteers completed three 2-d trials: rest, continuous exercise, and intermittent games activity. Trials were performed a minimum of 6 d apart in a balanced crossover design. In the rest trial, subjects took no exercise on day 1. On day 1 of the continuous and intermittent games trials, subjects completed four blocks (approximately 15 min per block) of uphill treadmill walking or intermittent games activity with 3 min of rest between each block. On day 2, subjects came to the laboratory for an oral fat tolerance test (blood taken fasted and for 6 h following a high-fat test meal (1.25 g of fat and 1.07 g of carbohydrate per kilogram of body mass)). Results: The intermittent games protocol elicited a higher exercise intensity than the continuous trial (lactate: 4.3 ± 0.6 vs 2.4 ± 0.3 mmol·L-1; % V?O2max: 72 ± 2 vs 62 ± 1, respectively; mean ± SE). The total area under the plasma triacylglycerol (TAG) concentration versus time curve was lower in both the intermittent games (25%, P = 0.001) and the continuous (19%, P = 0.028) trials than in the rest trial. Conclusion: These findings show for the first time that intermittent games activity can reduce postprandial lipemia, and confirm that continuous exercise reduces postprandial lipemia in young adults.

Few studies have addressed factors influencing Scottish adolescent girls’ participation in physical activity (PA). Participants (N = 352) aged 11 to 16 years completed surveys measuring PA participation and potential social-psychological and physical-environmental correlates. Data were analyzed separately by two age groups (11-13 and 14-16 years). For younger girls, mother’s participation, perceived importance, and home equipment use were higher among those higher in PA. For older girls, perceived importance, home equipment use, neighborhood perceptions, and use and enjoyment of local facilities were higher among girls higher in PA. It seems that older girls place less importance on significant others and move toward autonomy away from the home.

Background:The factors that regulate the growth hormone (GH) response to physiological stimuli, such as exercise, are not fully understood. The aim of the present study is to determine whether age, body composition, measures of sprint performance or the metabolic response to a sprint are predictors of the GH response to sprint exercise in non-obese young men. Methods:Twenty-seven healthy, non-obese males aged 18–32 years performed an all-out 30-second sprint on a cycle ergometer. Univariate linear regression analysis was employed to evaluate age-, BMI-, performance- and metabolic-dependent changes from pre-exercise to peak GH and integrated GH for 60 min after the sprint. Results:GH was elevated following the sprint (change in GH: 17.0 ± 14.2 µg l–1; integrated GH: 662 ± 582 min µg l–1). Performance characteristics, the metabolic response to exercise and BMI were not significant predictors of the GH response to exercise. However, age emerged as a significant predictor of both integrated GH (β = –0.547, p = 0.003) and change in GH (β = –0.448, p = 0.019) after the sprint. Conclusion:In non-obese young men, age is a more important predictor of GH following sprint exercise than BMI, sprint performance or the metabolic response to sprint exercise.

Nine unacclimatized university sportsmen performed a prolonged, intermittent, high-intensity shuttle running test in hot (HT) (33 degrees C, dry bulb temperature, approximately 28 %, relative humidity) and moderate (MT) (17 degrees C, 63 %) environmental conditions. Subjects performed 60 m of walking, a 15-m sprint, 60 m of cruising ( approximately 85 % V.O (2max)), and 60 m of jogging ( approximately 45 %V.O (2max)) for 14.8 +/- 0.1 min followed by a 3-min rest, repeated until volitional exhaustion. The hot trial was performed first followed, 14 days later, by the moderate trial. During exercise subjects drank water ad libitum. Subjects ran almost twice as far in the moderate as in the hot trial (HT 11216 +/- 1411, MT 21644 +/- 1629, m, p < 0.01), and the decline in average 15-m sprint performance was greater in the heat (HT, 0.17 +/- 0.05, MT, 0.09 +/- 0.03, s, p < 0.05). Average heart rates, blood lactate and glucose, and plasma adrenaline and noradrenaline concentrations were greater in the HT (main effect trial, p < 0.01), as were serum cortisol concentration (main effect trial p < 0.05, n = 5) and muscle temperature (HT exhaustion vs. same time point in MT, 40.2 +/- 0.3 vs. 39.3 +/- 0.2, degrees C, p < 0.01). Peak torque during knee flexion and extension was not different pre-and post-exercise in the HT. Muscle glycogen utilization tended to be greater in the heat (HT 193.2 +/- 19.5, MT 143.8 +/- 23.9, mmol . kg dry wt (-1), p = 0.055, n = 8). In 7 out of the 8 subjects the increase in utilization was between 19 and just over 200 % greater in the HT. Glycogen remaining in the muscle at exhaustion was greater in the hot than moderate trial (HT 207.4 +/- 34.3, MT 126.5 +/- 46.8, mmol . kg dry wt (-1), p < 0.01, n = 8). Rectal temperature (T (rec)) was higher in the HT at exhaustion than at the same point in time in the moderate trial (HT, 39.60 +/- 0.15 vs. MT 38.75 +/- 0.10, degrees C, interaction trial-time, p < 0.01). There was a very strong negative relationship between rate of rise in T (rec) and distance completed in the HT (HT r = - 0.90, p < 0.01, MT r = - 0.76, p < 0.05). Thus, the earlier onset of exhaustion during prolonged intermittent shuttle running in the heat is associated with hyperthermia. However, while muscle glycogen utilization may be elevated by heat stress, low whole muscle glycogen concentrations would not seem to be the cause of this earlier exhaustion.

Purpose: The study was conducted to examine the effects of oral creatine supplementation on training for competition in 20 elite swimmers. Methods: Subjects performed a maximal sprint test (8 x 50 yd (45.72 m), T1) before loading with creatine (Cr, 20 g[middle dot]d-1 Cr monohydrate for 5 d), 1 wk later (T2), and following a 22- to 27-wk period of training and competition (T3). Following T2, subjects supplemented with either Cr (3 g + glucose 7 g[middle dot]d-1) or placebo (glucose 10 g[middle dot]d-1; double blind) for the remainder of the 22- to 27-wk season and then both groups supplemented once more with 20 g[middle dot]d-1 Cr monohydrate for 5 d before their major competition. Venous and capillary blood samples were obtained pre- and posttest during the repeated sprint tests to determine blood metabolites and hormones. Competition times were recorded, and changes in subjects' best times were used to compare the effect of training and supplementation on competitive performance. Results: Mean competition times in the Cr and control groups changed by +1.90 +/- 1.91 and +0.72 +/- 1.64% for short course (SC, 25-m pool) and by +0.14 +/- 1.14 and -0.59 +/- 0.82% long course (LC, 50-m pool), respectively (Cr vs control, NS). No differences between groups were found in blood metabolites, although the human growth hormone (hGH) response to repeated sprints was blunted following Cr loading (T1, 30.42 +/- 14.60 and 28.95 +/- 18.27 [mu]g[middle dot]L-1; T2, 21.48 +/- 13.96 and 14.24 +/- 7.32 [mu]g[middle dot]L-1 for Cr and control groups, respectively P < 0.05). Conclusion: No statistically significant differences in performance were observed between groups after long-term maintenance during training, although small differences were observed that might be meaningful for elite performers.

This study examined the growth hormone (GH) response to repeated bouts of sprint cycling. Eight healthy men completed three trials consisting of two 30-s sprints on a cycle ergometer separated by either 60 min ( Trial A) or 240 min ( Trial B) of recovery and a single 30-s sprint carried out the day after Trial B ( Trial C). Trials A and B were separated by at least 7 days. Blood samples were obtained at rest and during recovery from each sprint. In Trial A, GH was elevated immediately before sprint 2, and there was no further increase in GH following the second sprint [area under the curve: 460 (SD 348) vs. 226 min·μg−1·l−1 (SD 182), P = 0.05]. Free insulin-like growth factor I tended to be lower immediately before sprint 2 than sprint 1 ( P = 0.06). Serum free fatty acids were not different immediately before each of the sprints. In Trial B, there was a trend for a smaller GH response to the second sprint [GH area under the curve: 512 (SD 396) vs. 242 min·μg−1·l−1 (SD 190), P = 0.09]. Free insulin-like growth factor I tended to be lower ( P = 0.06), and serum free fatty acids were higher ( P = 0.01) immediately before sprint 2 than sprint 1. There was no difference in the GH response to sprinting on consecutive days ( Trials B and C). In conclusion, repeated bouts of sprint cycling on the same day result in an attenuation or even ablation of the exercise-induced increase in GH, depending on the recovery interval between sprints.

Background:Many adolescent girls have low levels of physical activity and participation declines with age. This review identifies recent correlates of physical activity in adolescent girls.Methods:Systematic review of papers published 1999 to mid-2003. Papers (k = 51) reporting a measure of physical activity and at least one potential correlate of physical activity in adolescent girls were analyzed.Results:Demographics related to physical activity were female gender (–), non-white ethnicity (–), age (–), and socio-economic status (+). Psychological correlates positively associated with physical activity were enjoyment, perceived competence, self-efficacy, and physical self-perceptions. Behavioral correlates showed that smoking was associated with lower and organized sport involvement with greater activity. Physical activity was associated with parental and family support but we found no consistent trends for environmental variables. Effects were small-to-moderate.Conclusions:Modifiable correlates for adolescent girls clustered around “positive psychology,” organized sport involvement, and the family.

This study examined the effect of 6 weeks of prescribed sprint training on the human growth hormone (hGH) response to cycle ergometer sprinting. Sixteen male subjects were randomly assigned to a training (n=8) or a control (n=8) group. Each subject completed two main trials, consisting of two all-out 30-s cycle-ergometer sprints separated by 60 min of passive recovery, once before, and once after a 6-week training period. The training group completed three supervised sprint-training sessions per week in addition to their normal activity, whilst control subjects continued with their normal activity. In the training group, peak and mean power increased post-training by 6% (P0.05) and 5% (P0.05), respectively. Post-exercise blood pH did not change following training, but the highest post-exercise blood lactate concentrations were greater [highest measured value: 13.3 (1.0) vs 15.0 (1.1) mmol l(-1)], with lower blood lactate concentrations for the remainder of the recovery period (P0.05). Post-exercise plasma ammonia concentrations were lower after training [mean highest measured value: 184.1 (9.8) vs 139.0 (11.7) micromol l(-1), P0.05]. Resting serum hGH concentrations did not change following training, but the peak values measured post-exercise decreased by over 40% in the training group [10.3 (3.1) vs 5.8 (2.5) microg l(-1), P0.05], and mean integrated serum hGH concentrations were 55% lower after training [567 (158) vs 256 (121) min microg l(-1), P0.05]. The hGH response to the second sprint was attenuated similarly before and after training. This study showed that 6 weeks of combined speed- and speed-endurance training blunted the human growth hormone response to sprint exercise, despite an improvement in sprint performance.

Nine male student games players consumed either flavoured water (0.1 g carbohydrate, Na+ 6 mmol x l(-1)), a solution containing 6.5% carbohydrate-electrolytes (6.5 g carbohydrate, Na+ 21 mmol x l(-1)) or a taste placebo (Na+ 2 mmol x l(-1)) during an intermittent shuttle test performed on three separate occasions at an ambient temperature of 30 degrees C (dry bulb). The test involved five 15-min sets of repeated cycles of walking and variable speed running, each separated by a 4-min rest (part A of the test), followed by 60 s run/60 s rest until exhaustion (part B of the test). The participants drank 6.5 ml x kg(-1) of fluid as a bolus just before exercise and thereafter 4.5 ml x kg(-1) during every exercise set and rest period (19 min). There was a trial order effect. The total distance completed by the participants was greater in trial 3 (8441 +/- 873 m) than in trial 1 (6839 +/- 512, P0.05). This represented a 19% improvement in exercise capacity. However, the trials were performed in a random counterbalanced order and the participants completed 8634 +/- 653 m, 7786 +/- 741 m and 7099 +/- 647 m in the flavoured water (FW), placebo (P) and carbohydrate-electrolyte (CE) trials, respectively (P = 0.08). Sprint performance was not different between the trials but was impaired over time (FW vs P vs CE: set 1, 2.41 +/- 0.02 vs 2.39 +/- 0.03 vs 2.39 +/- 0.03 s; end set, 2.46 +/- 0.03 vs 2.47 +/- 0.03 vs 2.47 +/- 0.02 s; main effect time, P0.01). The rate of rise in rectal temperature was greater in the carbohydrate-electrolyte trial (rise in rectal temperature/duration of trial, degrees C x h(-1); FW vs CE, P0.05; P vs CE, N.S.). Blood glucose concentrations were higher in the carbohydrate-electrolyte than in the other two trials (FW vs P vs CE:rest, 4.4 +/- 0.1 vs 4.3 +/- 0.1 vs 4.2 +/- 0.1 mmol x l(-1); end of exercise, 5.4 +/- 0.3 vs 6.4 +/- 0.6 vs 7.2 +/- 0.5 mmol x l(-1); main effect trial, P0.05; main effect time, P0.01). Plasma free fatty acid concentrations at the end of exercise were lower in the carbohydrate-electrolyte trial than in the other two trials (FW vs P vs CE: 0.57 +/- 0.08 vs 0.53 +/- 0.11 vs 0.29 +/- 0.04 mmol x l(-1); interaction, P0.01). The correlation between the rate of rise in rectal temperature (degrees C x h(-1)) and the distance completed was -0.91, -0.92 and -0.96 in the flavoured water, placebo and carbohydrate-electrolyte conditions, respectively (P0.01). Heart rate, blood pressure, plasma ammonia, blood lactate, plasma volume and rate of perceived exertion were not different between the three fluid trials. Although drinking the carbohydrate-electrolyte solution induced greater metabolic changes than the flavoured water and placebo solutions, it is unlikely that in these unacclimated males carbohydrate availability was a limiting factor in the performance of intermittent running in hot environmental conditions.

We examined the plasma concentration curve obtained over 6 h after the ingestion of 2 g of creatine (Cr) (equivalent to 2.3 g Cr x H2O) contained in meat or in solution in five non-users of creatine supplements. Peak plasma creatine concentration was lower after the ingestion of meat but was maintained close to this for a longer period. Measurements of the area under the plasma concentration curve indicated approximate bioequivalence of creatine contained in meat with the same dose supplied in a solution. In a separate study, we examined the plasma concentration time curve after ingestion of solid Cr x H2O. Creatine ingested as a lozenge (crushed in the mouth and swallowed) or as a crystalline suspension in ice cold water resulted in a 20% lower peak concentration and 30-35% smaller area under the plasma creatine concentration curve than the same dose administered in solution. Despite a possibly lower bioavailability, 2.3 g Cr x H2O supplied in either solid form was nonetheless sufficient to raise the plasma concentration five- to six-fold in individuals with a mean body mass of 75.6 kg. We conclude that creatine administered as meat or in solid form is readily absorbed but may result in slightly lower peak concentrations than when the same dose is ingested as a solution.