The evolution of reproductive strategies in turtles.

Optimal egg size theory assumes that changes in the egg and clutch are driven by selection, resulting in adjustments for the largest possible production of offspring with the highest fitness. Evidence supports the idea that large-bodied turtles tend to produce larger clutches with small and round eggs, while smaller species produce small clutches with large and elongated eggs. Our goals were to investigate whether egg and clutch size follow the predictions of egg size theory, if there are convergent reproductive strategies, and identify ecological factors that influence clutch and egg traits across all clades of living turtles. Using phylogenetic methods, we tested the covariance among reproductive traits, if they are convergent among different turtle lineages, and which ecological factors influence these traits. We found that both egg shape and size inversely correlate with clutch size, although with different evolutionary rates, following the predictions of the egg size theory. We also present compelling evidence for convergence among different turtle clades, over at least two reproductive strategies. Furthermore, climatic zone is the only ecological predictor to influence both egg size and fecundity, while diet only influences egg size. We conclude that egg and clutch traits in Testudines evolved independently several times across non-directly related clades that converged to similar reproductive strategies. Egg and clutch characteristics follow the trade-offs predicted by egg size theory and are influenced by ecological factors. Climatic zone and diet play an important role in the distribution of reproductive characteristics among turtles.

How does curve sprint evolve across different age categories in soccer players?

Research has shown that soccer players regularly execute curved sprints during matches. The purpose of this study was to determine the age-related effects on curve sprint (CS) performance to both sides, asymmetry, and association with linear sprint (LS). Eighty-four soccer players (aged 16.1 ± 1.6 categorized in U15, U17, and U20) were recruited, who performed CS and LS tests. One-way analysis of variance (ANOVA) and effect size (ES) were used to compare CS performance between age categories, and relationships between physical performance measures were calculated using Pearson's correlation coefficient. The main findings of this study were that: 1) there were significant differences in the "good" side CS among age groups (p < 0.001; ES from moderate to large), but not in the "weak" side CS, 2) curve asymmetry was significantly higher in U20 than U15 (p < 0.05; ES large) and U17 players (p < 0.05; ES moderate), and 3) relationships between CS and LS times decreased with age (from significant and very large [p < 0.001] to non-significant and smallmoderate [p > 0.05]). This study highlights the importance of assessing and training CS in different age categories, an action that becomes less correlated with LS as age increases, with the aim of mitigating the increase in asymmetries as a result of the specialization process, focusing interventions mainly on improving the CS "weak" side.

The influence of anthropometric variables, body composition, propulsive force and maturation on 50m freestyle swimming performance in junior swimmers: An allometric approach.

The purpose of the current article was to use allometric models to identify the best body size descriptors and other anthropometric variables, body composition, and offset maturity that might be associated with the youngsters' 50m personal-best (PB) swim speeds (m·s-1). Eighty-five competitive swimmers (male, n=50; 13.5±1.8 y; female, n=35; 12.6±1.8 y) participated in this study. Height, body mass, sitting height, arm span, skinfolds, arm muscle area (AMA), and maturity offset were assessed. Swimming performance was taken as the PB time recorded in competition, and the propulsive force of their arm (PFA) was assessed by the tied swimming test. The multiplicative allometric model relating 50m PB swim speeds (m·s-1) to all the predictor variables found percentage body fat as a negative [(BF%) ß= -.121±.036; P=0.001], and PFA (PFA ß=.108±.033; P=0.001) and the girl's arm span (ß=.850±.301; P=0.006), all log-transformed, as positive significant predictors of log-transformed swim speed. The adjusted coefficient of determination, Radj2 was 54.8% with the log-transformed error ratio being 0.094 or 9.8%, having taken antilogs. The study revealed, using an allometric approach, that body fatness and PFA were significant contributors to 50m freestyle swim performance in young swimmers.

Anthropometric variables, propulsive force and biological maturation: A mediation analysis in young swimmers.

Youth swimming performance may be influenced by anthropometric and body composition factors during growth. Propulsive force of the arm (PFA) is highly related to swimming performance as 85-90% of the propulsive power comes from the arms. The current study analyzed the mediating effect of biological maturation on the relationship between anthropometric variables and body composition with PFA in young swimmers. A total of 128 swimmers [boys: n = 53, age = 13.6 (1.8) y; girls: n = 75, age = 12.5 (1.8) y] were evaluated. Propulsive force of the arm was estimated by the tethered swimming test. Anthropometric characteristics (body mass, stature, sitting height, arm span, arm muscle area, %body fat, and fat-free mass) were evaluated. Biological maturation was estimated by the age of peak height velocity. Mediation analyses were performed using the Preacher and Hayes bootstrapping method, adjusted for chronological age and sex. All anthropometric and body composition variables, except %body fat, were positively associated with PFA, being mediated by biological maturation. Indirect effects and 95% confidence intervals were: body mass [.20 (.09-.34)], stature [.22 (.11-.43)], arm span [0.17 (.05-.31)], arm muscle area [.74 (.38-1.19)] and fat free-mass [.17 (.05-.34)]. In conclusion, biological maturation mediated the positive associations between body size and composition and PFA in young swimmers.

Is motor competence associated with the risk of central obesity in preschoolers?

OBJECTIVES: To investigate the association between motor competence (MC) and central obesity in preschool children. METHODS: The sample comprised of 472 children aged 3 to 5 years (4.58 ± 0.70 years, 248 boys) from Recife, Brazil. MC was assessed using the Test of Gross Motor Development-2. Waist-to-height ratio (WHtR) was calculated and a cutoff of 0.5 was used to define central obesity. Logistic regression was used to examine the association between MC and WHtR ≥ 0.5. RESULTS: The prevalence of central obesity (WHtR) was 54.0% and 46.4% for boys and girls, respectively. Older children (OR = 0.61; CI = 0.44-0.84; P < .01) and those with higher MC in locomotor skills (OR = 0.96; CI = 0.93-0.99; P < .01) were less likely to present WHtR ≥ 0.5. Sex and object control skills were not associated with WHtR ≥ 0.5. CONCLUSIONS: To reduce the risks of central obesity in children, health practitioners should focus on increasing competence in locomotor skills since preschool years.

Are there gross motor coordination spurts during mid-childhood?

OBJECTIVES: The aims of this study were (1) to identify the timing of the mid-growth spurt (MGS) in stature in children and (2) to identify gross motor coordination (GMC) spurts when aligned by the age of attainment of the MGS (aMGS). METHODS: Stature, weight, and GMC were measured in 245 Portuguese children followed annually from 6 to 10 years. GMC was assessed and to estimate children's MGS in stature as well as GMC spurts in each of the four tests aligned by aMGS, we used a nonsmoothed polynomial methodology. RESULTS: In boys, the aMGS was attained at 7.8 years, whereas in girls it was 8.0 years. In boys, the peak MGS was 6.2 cm∙yr-1 and in girls it was 6.4 cm∙yr-1 . In boys, the peak for walking backwards (WB) occurred 18 months before aMGS (14.9-points∙yr-1 ), jumping sideways (JS) was 12 months after aMGS (13.5-points∙yr-1 ), hopping on one leg (HO) was 18 months before aMGS (11.7-points∙yr-1 ), and shifting platform (SP) was 12 months before aMGS (6.8-points∙yr-1 ). In girls, WB spurts occurred 12 months after aMGS (13.3-points∙yr-1 ), JS was 12 months before aMGS (10.5-points∙yr-1 ), HO was coincident with aMGS (10.4-points∙yr-1 ), and SP was 18 as well as 12 months before aMGS (7.2-points∙yr-1 ). No differences were observed in the mean peak spurts between sexes in the GMC tests. CONCLUSIONS: Boys and girls reached their MGS in stature at about the same chronological age. Spurts in GMC did not express themselves in the same biological timing relative to aMGS in stature, and there are sex differences.

Association between body mass index and individual characteristics and the school context: a multilevel study with Portuguese children / Relação entre o índice de massa corporal e as características individuais e do contexto escolar: um estudo multinível com crianças portuguesas

Abstract Objective The aim of this study was to examine the association between individual and school context characteristics with the body mass index of Portuguese children. Methods The sample comprised 1641 children (847 boys) aged 6-10 years from the North and Central regions of Portugal. Regarding the individual characteristics, age, gender, city of residence, levels of physical activity, and physical fitness were assessed. Concerning the school context characteristics, the surrounding environment, school size, presence of recreational characteristics and space, and presence of a sports court and of physical education classes were considered. Children's body mass index was the dependent variable. The multilevel analysis was carried out in HLM 7.0 software. Results The predictors of the child and the school context explained, respectively, 97.3% and 2.7% of the total body mass index variance. Regarding the individual characteristics, older children, boys, and those who had lower performance at the 1-mile run/walk, curl-up, push-up, and higher performance in trunk lift tests showed higher BMI. Further, urban schools with higher recreational spaces were positively associated with children's body mass index. Conclusion School context variables have a reduced effect on body mass index variation compared to the children's biological and behavioral characteristics. The authors therefore encourage strategies that aim to increasing children's physical fitness levels to help prevent excess weight.

Resumo Objetivo Examinar a associação de características individuais e do contexto escolar no índice de massa corporal de crianças portuguesas. Método A amostra compreendeu 1.641 crianças (847 meninos) de 6 a 10 anos. Em relação às características individuais foram utilizadas informações relativas ao sexo, à idade, à residência, à atividade física e à aptidão física. Em termos de contexto escolar, foram considerados o meio ambiente, o tamanho da escola, a presença de recreio, as características e as dimensões do espaço disponível para o recreio, a existência de quadra poliesportiva e de aulas de educação física. O índice de massa corporal [kg/(m2)] foi a variável dependente. A análise multinível foi efetuada no software HLM 7.0. Resultados Os preditores da criança e do contexto escolar explicaram, respectivamente, 97,3% e 2,7% da variância total do índice de massa corporal. Quanto às características individuais, a idade (mais velhos) e o sexo (meninos), bem como o desempenho reduzido nas provas de corrida/marcha da milha, do curl-up, do push-up e valores elevados no trunk lift, estiveram associados ao aumento no índice de massa corporal. Escolas do meio urbano e escolas com maiores espaços para o recreio também estiveram positivamente associadas ao aumento do índice de massa corporal. Conclusões As variáveis do contexto escolar têm um efeito reduzido na variação do índice de massa corporal comparativamente às características biológicas e comportamentais das crianças. Sugere-se a aplicação de programas que visem ao incremento dos níveis de aptidão física das crianças para prevenir o excesso de peso na infância.

Comparison of motor competence levels on two assessments across childhood.

This study compared performances and motor delay classifications for the Test of Gross Motor Development-2nd edition (TGMD-2) and the Körperkoordinationstest Für Kinder (KTK) in a sample of 424 healthy children (47% girls) between 5 and 10 years of age. Low-to-moderate correlations (r range = 0.34-0.52) were found between assessments across age. In general, both boys and girls demonstrated higher raw scores across age groups. However, percentile scores indicated younger children outperformed older children, denoting a normative percentile-based decrease in motor competence (MC) in the older age groups. In total, the TGMD-2 and KTK classified 39.4% and 18.4% children, respectively, as demonstrating very low MC (percentile ≤5). In conclusion, the TGMD-2 classified significantly more children with motor delays than the KTK and the differences between children's motor skill classification levels by these assessments became greater as the age groups increased. Therefore, the TGMD-2 may demonstrate more susceptibility to sociocultural influences and be more influenced by cumulative motor experiences throughout childhood. Low-to-moderate correlations between assessments also suggest the TGMD-2 and KTK may measure different aspects of MC. As such, it may be important to use multiple assessments to comprehensively assess motor competence.

Association between body mass index and individual characteristics and the school context: a multilevel study with Portuguese children.

OBJECTIVE: The aim of this study was to examine the association between individual and school context characteristics with the body mass index of Portuguese children. METHODS: The sample comprised 1641 children (847 boys) aged 6-10 years from the North and Central regions of Portugal. Regarding the individual characteristics, age, gender, city of residence, levels of physical activity, and physical fitness were assessed. Concerning the school context characteristics, the surrounding environment, school size, presence of recreational characteristics and space, and presence of a sports court and of physical education classes were considered. Children's body mass index was the dependent variable. The multilevel analysis was carried out in HLM 7.0 software. RESULTS: The predictors of the child and the school context explained, respectively, 97.3% and 2.7% of the total body mass index variance. Regarding the individual characteristics, older children, boys, and those who had lower performance at the 1-mile run/walk, curl-up, push-up, and higher performance in trunk lift tests showed higher BMI. Further, urban schools with higher recreational spaces were positively associated with children's body mass index. CONCLUSION: School context variables have a reduced effect on body mass index variation compared to the children's biological and behavioral characteristics. The authors therefore encourage strategies that aim to increasing children's physical fitness levels to help prevent excess weight.

Tracking of gross motor coordination in Portuguese children.

The purpose of this study was to investigate the tracking of gross motor coordination (GMC) and to profile children at 6 years of age who consistently showed higher stability patterns in different levels of GMC. The participants were 245 children (123 boys and 122 girls) who were assessed longitudinally from 6 to 9 years of age. GMC was assessed using the Korperkoordinationtest fur Kinder (KTK) test battery. Anthropometry, physical activity, and health- and performance-related physical fitness were also measured. Cohen's kappa (κ) was used to estimate tracking. Tracking was poor for all GMC tests (0.17 ≤ κ ≤ 0.38) and moderate for the GMC motor quotient (MQ) in both boys and girls (0.44 ≤ κ ≤ 0.45). Instability at the extremes was low in GMC tests and negligible for MQ. Children who consistently showed high GMC levels during the 4 years of follow-up were lighter, had lower body mass index and subcutaneous fat, and showed higher scores in physical fitness tests at 6 years of age than those who consistently had low GMC levels. In conclusion, GMC showed low-to-moderate tracking over time in childhood. However, children who consistently demonstrated high GMC levels over time had healthier profiles at 6 years of age.

Familial resemblance in gross motor coordination. The Peruvian Sibling Study on Growth and Health.

BACKGROUND: The development of gross motor coordination (GMC) is governed by biological and environmental factors whose effect sizes are still unclear. AIM: To investigate sibling resemblance in GMC, as well as biological and environmental correlates of GMC among Peruvian children. MATERIALS AND METHODS: The sample comprised 1256 biological siblings (6-15 years old), from three geographical areas of Peru. GMC was assessed using the Korperkoordinationtest für Kinder (KTK) test battery. Anthropometry, biological maturation and physical fitness (PF) were also measured. Multilevel modelling was performed using Stata 14 software. RESULTS: In general, sister-sister pairs (SS) showed the highest resemblance in GMC (ρ = 0.24) compared to brother-sister (BS) (ρ = 0.10) and brother-brother (BB) pairs (ρ = 0.07). On average, BB pairs had higher GMC than SS pairs and older siblings had higher GMC than younger siblings. Further, those with lower body mass index (BMI) and higher PF had higher GMC. There was also a significant interaction between age and PF with GMC. Siblings from the rainforest region demonstrated higher GMC than those from sea level and high-altitude siblings demonstrated lower GMC than their sea-level peers. CONCLUSION: These results demonstrate statistically significant sibling resemblance in GMC. Age, BMI, PF and geographical area were significant correlates of GMC.

Association between sports participation, motor competence and weight status: A longitudinal study.

OBJECTIVES: The aim of this study was to investigate if baseline motor competence, weight status and sports participation in early childhood predict sports participation two years later. DESIGN: longitudinal study. METHODS: In 2010, motor competence (object control and locomotor skills), weight status and sports participation were assessed in 292 children between three and five years-of-age. In 2012, sports participation was re-evaluated in 206 of the original 292 children. Logistic regression was implemented to examine if initial sports participation, motor competence and weight status would predict sports participation two years later. RESULTS: In the final model, sports participation in 2010 (OR=9.68, CI: 3.46 to 27.13) and locomotor skills (OR=1.21, CI: 1.01 to 1.46) significantly predicted sports participation after two years. CONCLUSIONS: These results suggest that initial sports participation and more advanced locomotor skills in preschool years may be important to promote continued participation in sports across childhood.