Biological Maturation and Hormonal Markers, Relationship to Neuromotor Performance in Female Children

Exercise Immunology Applied to Pediatric Sport and the Importance of Monitoring Stages of Puberty and Biological Maturation

CONTEXT

Exercise immunology is aimed at understanding how exercise sessions can affect the immune system in athletic subjects of different age groups. The objective of the current study was to discuss in which stage of biological maturation (BM) young athletes may be more vulnerable in relation to the immune system, and whether there is a BM range in which it is safer to perform sports training with strenuous exercise loads.

EVIDENCE ACQUISITION

Evidence from scientific research from several scientific disciplines (eg, immunology, sport immunology, pediatrics, sports medicine, human development) was gathered to holistically examine the main particularities of exercise immunology as applied to pediatric sport.

STUDY DESIGN

Narrative review.

LEVEL OF EVIDENCE

Level 5.

RESULTS

In pediatric patients, lymphoid tissue expands during puberty and involutes after puberty until it returns to pre-expansion values. This suggests that there is a specific period in which the immune system may be stronger, which may provide opportunities for strenuous exercise in pediatric athletes. However, the chronological period when puberty occurs will be determined by BM, which is the rate at which the biological systems of the human body improves. This may affect the period of lymphoid tissue expansion and, consequently, the behavior of the immune system in pediatric subjects of the same age category.

CONCLUSION

During puberty, there is a significant increase in the proinflammatory profile; to compensate for this, there is an expansion of lymphoid tissue that may favor the efficiency of the immune system. The period in which puberty is reached may vary according to the stages of BM. Therefore, in exercise immunology applied to pediatric sports, in addition to external and internal training loads, it is necessary to consider BM and puberty, which have been shown to be safer biomarkers than chronological age for determining immune system behavior in pediatric athletes.

STRENGTH-OF-RECOMMENDATION TAXONOMY (SORT)

Evidence B level 3.

Successful Young Athletes Have Low Probability of Being Ranked Among the Best Senior Athletes, but This Is Higher When Compared to Their Less Successful Peers

Background

Contemporary research has shown that only a small proportion of high achieving young athletes continue to become successful senior athletes. However, there is a lack of empirical literature tracking the success of senior male and female athletes who were considered high achieving as a youth.

Hypothesis

Athletes of both sexes who are successful in youth categories (U18 and U20) are more likely to be successful senior athletes.

Conclusion

Data from 67,600 athletes were collated from the tilastopaja.org platform. The inclusion criteria for both genders were determined by top-100 ranking in the U18 and U20 age groups and progression to the top-100 as a senior athlete. Only 23.5% of successful track and field athletes (ranked in top-100) at U18 became a successful senior athlete, while 35.4% were from the U20 group. Girls ranked in the top-100 U18 and U20 categories are significantly more likely to be ranked in the top-100 as a senior when compared to boys. Although, being ranked in the top-50 at U18 and U20 significantly increases the probability of becoming a successful senior athlete when compared with less successful athletes at these age groups (p < 0.001). Notably, the majority (68.5%) of the most successful senior athletes were not ranked in the top-100 when in the U18 or U20 age groups. Only a small group of track and field athletes that are successful at U18 and U20 become successful at senior level. The most successful track and field youth athletes are significantly more likely to succeed as a senior athlete than their less successful peers, while girls are more likely to be successful than boys.

Factors related to lower limb performance in children and adolescents aged 7 to 17 years: A systematic review with meta-analysis

BACKGROUND

The literature identifies several factors that are associated with lower limb performance (LLP). However, there is little consensus on which factors have the major associations with LLP.

OBJECTIVE

Examine, analyze and summarize the scientific evidence on the factors associated with the performance of LLP in children and adolescents of both sexes aged between 7 and 17 years.

DESIGN

This systematic review was conducted following the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement and was registered in PROSPERO.

DATA SOURCES

A systematic literature search of five electronic databases (i.e., SPORTDiscus, PubMed, CINAHL, Google Scholar, and SCOPUS) with date restrictions was conducted (2010 to 2021).

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Eligibility criteria included (i) a study published between 2010 and 2021; (ii) a research study with observational design; (iii) a study analyzing LLP; and (iv) a sample composed of young people between 7 and 17 years old (regardless of sex).

ANALYSES

Literature analysis was carried out in English and Portuguese between 2018 and 2021, "blindly" by two researchers. For data sorting, Rayyan® was used. Data extraction and evidence analysis were performed "blindly", using the Loney scale. The minimum items for observational studies were analyzed by the STROBE checklist. Meta-analyses were conducted based on age group (Childhood [7 to 11 Yrs] and Adolescence [12 to 17 Yrs]) and puberty stages (i.e., Prepupertal and Pubertal). The heterogeneity between the samples of the studies was assessed using the "Cochran's Q" and "I^2" statistics. Meta-regression analyses were performed to check the factors related to heterogeneity of the studies and to check the associations between chronological age and LLP.

RESULTS

The literature search resulted in 1,109,650 observational studies of which 39 were included in this review. Through Meta-analysis and Meta-regressions, it was possible to indicate that advancing chronological age related to increased LLP (p<0.01), and that in relation to puberty stages pubertal subjects had higher LLP than their pre-pubertal peers (p<0.01).

DISCUSSION

The main findings of the present systematic review suggest that as chronological age advances (childhood to adolescence), neuromuscular systems mature and this may be due to advancing puberty, which is also associated with an increase in LLP.

CONCLUSION

The factors associated with lower limbs performance are still inconsistent in the literature. However, advancing chronological age and stage of puberty are both associated with increased lower limbs performance.

TRIAL REGISTRATION

ID-PROSPERO-CRD42020137925.

Relationship between Anthropometric, Physical and Hormonal Parameters among Pre-Pubertal Handball Players

Background: The aims of our study were to investigate the changes in anthropometric and physical parameters and fasting hormonal levels among pre-pubertal female handball players (n = 14, age: 11.53 ± 0.58 yrs, height: 153.36 ± 5.12 cm, body mass: 43.59 ± 6.14 kg) in the pre-season period following 8 weeks of handball training, and to analyze the contribution of hormones, physical performance and anthropometric parameters. Methods: Prior to and immediately following the training period, several anthropometric, strength, and cardiorespiratory variables, including fasting hormonal concentrations (plasma cortisol, estradiol, testosterone and growth hormones) were measured. Athletes performed concurrent resistance and aerobic exercises, including game-based trainings during the 8-week training period. Results: Significant elevations were found in all strength parameters (maximal handgrip strength dominant (D): 16.40%, p < 0.01; non-dominant (ND): 25.15%, p < 0.05; maximal concentric (MVC) torque of quadriceps D: 13.82%, p < 0.05; ND: 12.61%, p < 0.05; MVC torque of hamstring D: 12.14%, p < 0.01; ND: 12.44%, p < 0.01), including plasma cortisol levels (C, 34.30%, p < 0.05) and peak respiratory quotient (5.24%, p < 0.05). Body composition and maximal oxygen uptake (VO_2max) remained unchanged. Percentage changes in thigh (r = 0.316, p < 0.05), hand (r = 0.361, p < 0.05), and hip circumference (r = 0.297, p < 0.05) correlated with C changes. Percentage changes in plasma growth hormone levels (GH) contributed to the magnitude of gains in handgrip strength (r = 0.553, p < 0.05). Percentage changes in maximal exercise pulmonary ventilation (MVE) correlated with elevated C (r = −0.592, p < 0.05). Discussion: Changes in anthropometric variables and fasting hormone levels (estradiol, testosterone and cortisol) were poor indicators of developing VO_2max and strength during pre-pubertal years. Physical adaptation may not be explained in consideration of the athletes’ hormonal or anthropometric characteristics. Conclusion: Gradually increased training volume followed by a summer break should be applied to youth handball, considering the anti-hypertrophic responses and the inhibitory effect of elevating C on pre-pubertal maturation.

Relationship of Biological Maturation with Muscle Power in Young Female Athletes

There is still no consensus on how biological maturation (BM) affects the muscle power of upper and lower limbs in young people. The objective was to verify associations between BM and muscle power, as well as to compare the muscle power of upper (ULP) and lower limbs (LLP) among young athletes in different stages of BM. The sample consisted of 79 female athletes (10.9 ± 1.11 years old). Regarding BM, the sample was divided into three groups: delayed BM, synchronized BM, and accelerated BM. BM was identified by subtracting chronological age from bone age (BA). BA was measured by a mathematical model based on anthropometry. The muscular power of the upper limbs was analyzed by the medicine ball launch test, and that of the lower limbs was analyzed by the countermovement jump on a force platform. BM and BA correlated with ULP (BA: r =0.74; BM: r =0.65) and LLP (BA: r = 0.50; BM: r =0.41). In the comparisons of the tests of ULP and LLP, the groups with synchronized and accelerated BM were superior to the group with delayed BM. The advance of BM is associated with the ULP and LLP, as well as the advance of the BM affects muscle power in young female athletes. This occurs due to the increase in body mass resulting from the advancement of BM, which may favor the predominance of lean body mass, assisting in the production of muscle strength.

Lean mass and biological maturation as predictors of muscle power and strength performance in young athletes

Background

The biological maturation (BM) analyzed by peak height velocity (PHV) and bone age (BA), and lean body mass has been associated with the strength and muscle power of young athletes. However, the ability of BM (PHV and BA) and LM markers to predict muscle strength and power in young athletes remains uncertain.

Objective

The Aim was determine the predicting power of BM markers (PHV and BA) and LM in relation to muscle power of upper and lower limbs and muscle strength of upper limbs in adolescent athletes at puberty.

Methods

Ninety-two adolescent athletes (both sexes; age 12.4 ± 1.02 years) were assessed for body composition by dual-energy X-ray absorptiometry (DXA). Power of upper limbs (ULP), force handgrip (HG), vertical jump (VJ) and countermovement jump (CMJ) were recorded. BM was predicted by mathematical models to estimate PHV and BA. Multilayer artificial neural network analyses (MLP’s) were used to determine the power of prediction of LM, PHV and BA on muscle power and strength of upper- and lower-limbs of the athletes.

Results

LM, BA and PHV were associated with HG (r>0.74, p<0.05) and ULS (r>0.60, p<0.05) in both sexes. In both sexes BA was associated with VJ (r>0.55, p<0.05) and CMJ (r>0.53, p<0.05). LM indicated associations (r>0.60, p<0.05) with BA and with PHV (r<0.83, p<0.05) in both sexes. MLP’s analysis revealed that the LM provides > 72% of probability to predict the muscle power of upper- and lower-limbs, and the strength of the upper limbs; whereas PHV provides > 43% and bone age >64% in both female and male adolescent athletes.

Conclusion

We identified that, like PHV and BA, LM is a strong predictor of low cost of both upper limbs muscle strength and upper and lower limbs power in adolescent athletes.

Body adiposity index to analyze the percentage of fat in young men aged between 7 and 17 years

BACKGROUND

The body adiposity index (BAI), uses anthropometry to estimate percent body fat (%F). However, previous studies have shown that the BAI has limited accuracy for children and adolescents.

OBJECTIVE

We propose to develop and validate an adjusted BAI for use in male children and adolescents from 7 to 17 years of age.

METHODS

The sample consisted of 141 physically active male children and adolescents (age: 12.5 ± 2.14). The %F was determined by X-ray dual energy absorptometry equipment (DXA) as the standard method and by BAI, using an equation that uses height and hip circumference. Arithmetic modeling was used to adjust the structure of the BAI mathematical model.

RESULTS

The BAI arithmetic adjustment was successful, resulting in the mathematical model named in the present study of adjusted body adiposity index (BAI_ADJ ). BAI and BAI_ADJ correlated with DXA (r ≤ .70, p < .001). Regression analyzes indicate that, BAI (CI 95% β: [1.35; 1.90], p < .0001) and BAI_ADJ (CI 95% β: [1.40; 1.90], p < .0001) have the potential to estimate %F. BAI pointed out a difference in relation to DXA (p = .04). While there was no difference between BAI_ADJ and DXA (p = .1). There was a proportion bias of 13.2% for BAI (p < .05), but not for BAI_ADJ (p > .05).

CONCLUSION

The adjusted model of the body adiposity index proves to be an effective tool for the analysis of the fat percentage in young males. In addition, it demonstrated significant degrees of agreement and validity in relation to DXA.

Biological age, testosterone, and estradiol as discriminating factors of muscle strength levels in young athletes

BACKGROUND

Neuromuscular fitness can be influenced at puberty by a steroid hormones, such as testosterone (TRT) and estradiol (EST). However, more information is needed to assess the reliability between the discriminatory power of biological age (BA) markers with the discriminatory power of TRT and EST in relation to muscle strength in young athletes who are at puberty.

PURPOSE

Aimed to analyze BA, TRT and EST as discriminating factors of upper limb (ULS) and lower (LLS) strength levels in young athletes.

METHODS

The sample of 81 young athletes (54.4% female and 45.6% male; age: 11.4±1.08). Hormones were analyzed by chemiluminescence, BA markers by anthropometric variables and body composition by tetrapolar bioimpedance. ULS was verified by the medicineball launch test and LLS by the countermovement jump test on a force platform.

RESULTS

EST was reliable for discriminating ULS (p<0.05) and LLS (p<0.05) in females. TRT showed reliability in discriminating ULS (p<0.05) and LLS (p<0.05) in males. BA was significant in discriminating ULS (p<0.0001) in females and ULS (p=0.002) and LLS (p<0.0001) in males. BA showed significant reliability with hormonal analyzes (p<0.05).

CONCLUSIONS

That hormonal concentrations are reliable in discriminating ULS and LLS of young athletes of both sexes. BA was shown to be effective in discriminating ULS (in both sexes) and LLS (in males). BA showed significant reliability with hormonal analyzes (ULS and LLS in male sex; LLS for female sex).

Equation for analyzing the peak power in aquatic environment: An alternative for olympic rowing athletes

PURPOSE

To develop an equation to provide the peak power (PP) through a specific stimulus performed in an aquatic environment, as well as to correlate morphological, anthropometric and strength variables with rowing performance.

METHODS

The sample consisted of 16 elite young rowing athletes of both sexes (15.7 ± 1.21 years). The strength of upper limbs and lower limbs was verified. To analyze the PP, a 100-m Sprint test was performed on an indoor rowing type ergometer, and after a 72-hour wash-out, the test was repeated in an aquatic environment on a vessel equipped with a global position system. Body composition was analyzed by examining bone densitometry with an X-ray source and maturation was verified by anthropometry.

RESULTS

The tests for water sprint and indoor rowing showed significant reliability (ICC = 0.695; p = 0.0007). The PP aquatic showed reliability with that acquired in indoor rowing (ICC = 0.897; p<0.0001) and was related to maturation (p<0.05). The morphology, anthropometry and strength of the upper limbs were related to the sprint and peak strength in both tests (p<0.05).

CONCLUSION

The equation for the PP in aquatic environment presented by the present study is highly reliable with an indoor ergometer digital ergometer.

The influence of biological maturation and neuromuscular performance on peak bone mineral density in children

BACKGROUND

The growth and development cycle of the adult is characterized by substantial changes in physical size and maturity, and is controlled by the simultaneous influence of genetic components and the environment. Changes in the development of bones, muscles and adipose tissue are among the most important aspects of adolescent physical development. The aim of this research was to examine the correlation between bone mineral density (BMD) and neuromuscular performance in children at different stages of maturation.

METHODS

The study included 31 participants of both sexes (11.7±1.89 years). Body composition was assessed through bone densitometry using an energy duo X-ray source. The neuromuscular performance of the upper limbs was analyzed by the medicine ball hand grip and throwing tests. The lower limbs by the vertical counter-motion jump test, and skeletal maturation was analyzed by bone age. Maturation was used as an effect control between the association of BMD and neuromuscular performance.

RESULTS

The results demonstrated significant associations between the performance of upper (P<0.0001) and lower (P=0.01) limbs and BMD. On inter-group comparison for only the accelerated maturational stage, male participants had greater BMD than female participants (P=0.001; effect size 3.13). Regarding the maturational stages, male participants in the accelerated maturational stage demonstrated higher BMD than those in the normal and delayed maturational stages (P=0.04; effect size 3.10), whereas female participants did not demonstrate significant differences in BMD accumulation.

CONCLUSIONS

BMD has a strong correlation with the neuromuscular performance of upper and lower limbs of children of both sexes.

Evaluation of the body adiposity index against dual-energy X-ray absorptiometry for assessing body composition in children and adolescents

BACKGROUND

It is important to clarify the association of lean and fat mass between children and adolescents considering the rising prevalence of overweight and obesity in this age group. The aim of this study was to verify the association between the body adiposity index (BAI) and dual-energy X-ray absorptiometry (DXA) methods for analyzing body composition, as well as analyzing the validity of BAI to verify the percentage of fat in children and adolescents.

METHODS

The sample was composed of 106 children and adolescents, 44 females (age: 11.5 ± 1.8 years) and 62 evils (13.6 ± 2.6 years). The body fat (%F) was measured using DXA and the doubly indirect BAI body fat estimation technique.

RESULTS

The BAI and DXA estimates of %F were strongly correlated (boys: r = .71, P < .0001; girls: r = .72, P < .0001). The linear regression analyses showed that BAI is significant to estimate the %F in total sample (P < .0001). For boys, the %F analyzes performed by BAI and DXA did not show any differences when compared (P = .2). In addition, BAI pointed out a significant proportion bias for both sexes (P < .0001), which suggests its inefficiency in the analysis of %F.

CONCLUSIONS

BAI and DXA correlate; however, there is low reliability and a high proportion bias for the analysis of %F by BAI.

The Effectiveness of Biological Maturation and Lean Mass in Relation to Muscle Strength Performance in Elite Young Athletes

This study aimed to identify the interactional relationships between maturation (biological age (BA)) and lean mass on strength development in young athletes from different sports. Using a cross-sectional study design, a sample of 64 young athletes (rowers, swimmers, jiu-jitsu, volleyball, soccer and tennis players) of both sexes (13.6 ± 1.17 years) were recruited. Body composition was assessed using dual energy bone densitometry with X-ray source (DEXA). Strength of upper limbs (ULS), force hand grip (HG), vertical jump (VJ) and jump against movement (CMJ) were recorded. BA was estimated from anthropometrics. BA relationships were identified with upper limb strength in all athletes, and with the lower limb strength of tennis players, only (p < 0.05). An interaction effect between lean mass and BA was found (η2p = 0.753), as was a local effect within the regression models (ƒ2 ≥ 0.33). Athletes with a higher concentration of lean mass had superior upper and lower limb strength (p < 0.05). Lean mass showed a local effect (ƒ2) greater than that associated with BA. Although maturation is related to strength development, the strength of the relationship is mitigated by the accrual of lean mass. Specifically, the local effect of lean mass on muscle strength is broader than that of maturation, especially for lower limb strength.

Can the Neuromuscular Performance of Young Athletes Be Influenced by Hormone Levels and Different Stages of Puberty?

BACKGROUND

Endocrine mechanisms can be a determining factor in the neuromuscular performance of young athletes.

OBJECTIVE

The objective of the present study was to relate maturational and hormonal markers to neuromuscular performance, as well as to verify whether young athletes with different testosterone levels show differences in muscle strength.

METHODS

The sample consisted of 37 young male Brazilian athletes (11.3 ± 0.94 years) who were members of a sports initiation project. Hormonal markers were analyzed biochemically by blood samples, and maturation markers by mathematical models based on anthropometry. Body composition was verified by tetrapolar bioimpedance. The performance of upper and lower limb strength and body speed were analyzed.

RESULTS

Hormonal and maturational markers were related to neuromuscular performance (p < 0.05). Young people with higher testosterone levels showed higher muscle strength (p < 0.05). Artificial neural networks showed that testosterone predicted the performance of upper limbs by 49%, and maturation by 60%. Maturation foreshadowed the performance of lower limbs by 30.3%.

CONCLUSION

Biological maturation and hormonal levels can be related to neuromuscular performance, and young people with higher testosterone levels show superior muscle strength in relation to the others.