Biological and environmental determinants of 12-minute run performance in youth

Biological maturation, fat mass and cardiorespiratory fitness in prepubescent girls: A mediation analysis

BACKGROUND

The association between indicators of maturation and measures of physical fitness are not well correlated and vary according to chronological age, sex, body size, and motor characteristics. It is known that chronological age, maturation, and fat mass are significant predictors of cardiorespiratory fitness in girls, however, the contributions of fat mass to the relationship between maturation and endurance performance are still unclear.

OBJECTIVE

The current study aimed to examine whether the association between somatic maturation and running performance in the 20-m shuttle-run in girls is mediated by estimated fat mass.

METHODS

The sample comprised 67 girls, aged 8.00-8.99 years. Stature, body mass, and skinfolds were measured. Estimates of body composition and predicted mature stature (PMS) were then calculated. Current stature was expressed as a percentage of PMS and somatic maturation was given by z-scores of the percentage of PMS. Mediation analysis was performed using the bias-corrected bootstrap approach with 5000 resamples in order to obtain estimates of total, direct, and indirect effects of z-scores of the percentage of PMS on 20-m shuttle-run performance mediated by fat mass.

RESULTS

The results show that fat mass mediated the negative effect of biological maturation on 20-m shuttle-run performance in the observed sample of prepubescent girls (Indirect effect: β = -0.177, 95%CI: -0.291 to -0.059).

CONCLUSION

Although the participants were prepubescent girls, poorer aerobic running performance appeared to be partly due to increased levels of fat mass.

Physical Fitness and Body Composition of Youth Referees in Invasion Games

BACKGROUND

Referees' activity can be an instrument for training students with an impact on health-related physical fitness (PF). This study aimed to investigate the differences in PF and body composition between students without sports practice (G1), students with regular sports practice (G2), and student referees in team invasion games (G3).

METHODS

This study followed a cross-sectional design. The sample comprised 45 male students between 14 and 20 years old (16.40 ± 1.85). Three groups (G1, G2, and G3) of 15 participants each were selected. PF was assessed by a 20 m shuttle run, change-of-direction test, and standing long jump. Body composition was determined by body mass index (BMI; kg/m2) and the percentage of body fat (%BF) predicted by skinfold.

RESULTS

After controlling for age as a covariate, the block of variables used to characterize PF was statistically different between sports practice groups favoring student referees (p < 0.001; r = 0.26). Similar results were achieved for body composition (i.e., BMI and %BF) (p < 0.001; r = 0.17). However, when the dependent variables were evaluated separately, there were only differences between groups in %BF (p = 0.007; r = 0.21). Student referees had statistically significantly lower values than the remaining groups.

CONCLUSION

Refereeing activity benefits PF related to health and performance, including body composition. This study confirms the benefits related to health in children and adolescents who are involved in refereeing activity.

Body Composition and Physical Fitness in Madeira Youth

BACKGROUND

Research on composition and physical fitness is lacking in school-aged children from Madeira. This study aimed to examine the frequencies of overweight and obese participants and, in addition, to compare the fitness levels of Madeira youth with reference data.

METHODS

The sample comprised 521 participants (n = 258 boys; n = 263 girls) aged 10.0-18.9 years old.

METHODS

Height and weight were measured. Body mass index (BMI) was calculated, and percent fat was derived from skinfolds. Tests detailed on FITESCOLA battery were performed. BMI was plotted against U.S. reference data and physical assessment contrasted with the cut-off points of FITESCOLA protocol and corresponding data developed in Portuguese youth.

RESULTS

The percentages of overweight and obesity were 15% (overweight) and 14% (obesity) for boys and 16% (overweight) and 6% (obesity) for girls. The median values of fat mass percentage were closely related to the cut-off standards; however, substantial variation was noted. Boys and girls tended to be below the recommendations of cardiorespiratory fitness.

CONCLUSIONS

Sport participation should be promoted in Madeira to attain acceptable values of body composition and physical fitness levels.

Is there stability in the performance of elite half-marathoners?

The purpose of this study was to investigate the performance stability of elite half-marathoners of both sexes. The study was composed of 24 elite athletes (12 female and 12 male), ranked among the Senior World TOP20 half-marathoners, who completed a half-marathon race for at least three consecutive years. Tracking was tested using autocorrelations and Kappa Cohen. Autocorrelation revealed a significant association, but a decrease in correlation among the years in both sexes. The overall weighted kappa showed lower stability in performance for both sexes (K ​= ​0.191 and K ​= ​−0.245) than for males. These findings suggest that both female and male elite half-marathoners showed low stability in performance during three events. Besides that, athletes with a better performance tended to present the highest performance stability. It is recommended that coaches track the developmental trajectories of the athletes to comprised the changes in performance across the years, as to provide environmental characteristics that can influence performance.

Change and Stability in Sibling Physical Fitness: The Portuguese Sibling Study

PURPOSE

This study aims to 1) describe mean changes in muscular and motor fitness components in sibships over 2 yr, 2) analyze individual tracking of fitness within sibships, 3) investigate sibling resemblance in fitness over time, and 4) examine the joint influence of biological, behavioral, and familial characteristics on fitness.

METHODS

The sample comprises 166 Portuguese biological sibling pairs (brother-brother, sister-sister, brother-sister) age 9-17 yr assessed at baseline and 2 yr later. Physical fitness components were measured with standardized tests. Percentage body fat and biological maturation were assessed, and physical activity, diet, screen time, and familial characteristics were obtained by questionnaires. Multilevel models were used to analyze the clustered longitudinal data.

RESULTS

Crude results showed that, on average, all sib-types increased their muscular and motor fitness components from baseline to follow-up (except sister-sister pairs in standing long jump and shuttle run). When adjusted for covariates, the mean changes were no longer significant. Individual tracking was moderate to high for the muscular component but low to moderate for the motor component. Consistency in sibling resemblance was higher in sister-sister pairs than in brother-brother and brother-sister pairs. More mature sibs were fitter in both components, whereas siblings with higher body fat percentage were less fit. Screen time, physical activity, and parental occupation were not associated with fitness components.

CONCLUSIONS

Biological characteristics were more strongly associated with fitness components than individual behaviors and familial characteristics. Furthermore, the muscular component tracked better than the motor component. Sister-sister pairs had greater resemblance in fitness over time compared with brother-brother or sister-brother pairs.