Growth, body composition and hormonal axes in children and adolescents

Effects of maximal power and the force-velocity profile on sprint acceleration performance according to maturity status and sex

This study aimed to determine whether maturational and sex-related differences in sprint times were accompanied by changes in relative maximal power (Pmax), force-velocity profiles (SFV) and optimal sprint distances (xopt). Sprint times and continuous velocity-time data were collected using a radar. Inverse dynamics applied to the centre of mass provided accurate estimations of force-velocity relationship parameters (Pmax, F0, v0, SFV, xopt) and technical variables (RFmax, DRF). Somatic maturity was determined from peak height velocity (PHV). Performance increased with maturation in girls and boys (p < 0.001, d = 0.86‒2.78) accompanied by increases in relative Pmax from pre to post-PHV (p < 0.011‒0.001, d = 0.98‒5.20). Increases in relative Pmax were predominantly due to more velocity-oriented profiles (p < 0.007‒0.001, d = 0.76‒1.41). xopt, RFmax and DRF also increased with maturation (p < 0.030‒0.001, d = 0.87‒3.40). Pmax increases in girls and boys throughout maturation enabling them to reduce sprint times. Both girls and boys increased Pmax through a shift to more velocity-oriented profiles. However, plateaus in F0 and RFmax were present from pre-PHV in girls, while boys had slower development from mid-PHV. Improving Pmax through increases in F0 and RFmax, while maintaining a velocity-oriented profile, will likely benefit youth sprint performance. A specific focus on these parameters is necessary from pre-PHV onwards in girls and from mid-PHV in boys.

Growth and physical development of children at apparent risk of sarcopenia

BACKGROUND

The consequences of sarcopenia on growth have received little attention. We analysed the potential risk resulting from the low lean mass for age expressed through the appendicular lean body mass index (aLBMI) and the ratio aLBM/trunk fat mass (trFM).

METHODS

The sample consisted of 580 participants 10-13 yrs evaluated twice in a 12-month interval: height, trFM, total and aLBM, whole-body bone mineral density less head (WBLH BMD), tibia and radius SOS, maturity and handgrip strength were measured. All variables except maturity and BMI were standardised according to sex and age group (Z-score) using the sample as a reference. A high risk of sarcopenia was identified for Z-scores ≤ -1 on aLBMI (Group B) or aLBM/trFM (Group C), while Z-scores > -1 on both markers were considered at low risk for sarcopenia (Group A). The ANCOVA adjusted for maturity was used to compare the three groups.

RESULTS

Girls showed a more significant decrease in the total BMC/LBM ratio in Group B and a minor increase in WBLH BMD in Group C (p < 0.050); boys in Group B showed a tendency to gain less height (p = 0.053).

CONCLUSION

The high risk of sarcopenia expressed through aLBMI or aLBM/trFM Z-score ≤ -1 compromises bone mineralisation in girls.

IMPACT

The findings emphasise the necessity of implementing routine screening protocols for sarcopenia risk within clinical environments and educational institutions. Such screenings should extend beyond merely assessing body mass index to encompass broader body composition variables like lean body mass. By integrating these assessments into routine health evaluations, healthcare professionals and educators can proactively identify at-risk individuals and initiate timely interventions for suboptimal physical growth and development.

Longitudinal Analysis of Latvian Child Growth: Anthropometric Parameters Dynamics from Birth to Adolescence

This study provides a comprehensive analysis of the physical development patterns from birth to adolescence, utilizing a longitudinal dataset of 70 children monitored from birth until 17 years of age. The research focuses on the variability of growth trajectories, emphasizing the role of genetic and environmental factors in influencing these patterns. Key findings indicate that most children undergo one or two periods of accelerated growth, with significant variability in the timing and magnitude of these growth spurts. The study also highlights the adaptive nature of growth changes over generations, influenced by ecological, nutritional, and socio-economic conditions. The longitudinal approach reveals critical insights into the timing of peak growth velocities, demonstrating that girls reach their growth peak approximately one year earlier than boys. The analysis of intergenerational growth patterns suggests a significant increase in average height over the century, attributed to genetic diversity and changes in lifestyle and nutrition. This study's findings emphasize the importance of updating physical development standards regularly to reflect the changing genetic and environmental landscape. The variability in growth patterns and their correlation with health outcomes in later life highlights the need for targeted public health strategies that address the underlying socio-economic and environmental determinants of health. This research contributes to the understanding of physical development trajectories and provides a foundation for future studies aimed at optimizing health outcomes from early childhood through adolescence. The primary objective of this article is to meticulously analyze the dynamics of height growth and accurately identify the periods of accelerated bodily development within the context of longitudinal research.

Muscle Strength Reference Values and Correlation with Appendicular Muscle Mass in Mexican Children and Adolescents

Strength and muscle mass are important determinants of health status, and reference values for pediatric populations from every country or geographic region are needed. The aim of this study was to develop age- and sex-specific reference values of muscle strength and evaluate the correlation between muscle strength and appendicular lean mass in Mexican children and adolescents. A cross-sectional study was conducted in 1111 healthy subjects ages 5 to 19 years of age participating in the "Body Composition Reference Values in Mexican Children and Adolescents" study. Smoothed reference values for the 1, 3, 5, 15, 25, 50, 75, 85, 95, 97, and 99 percentiles of muscle strength for upper and lower limbs were developed based on age and sex using Jamar® and Microfet2® dynamometers. Mean values were derived using the Generalized Additive Models for Location, Scale and Shape (GAMLSS), and lean mass was determined using dual-energy X-ray absorptiometry. Highly positive correlations of muscle strength with lean mass in upper limbs were found r-values 0.87-0.92 for boys and r = 0.80-0.86 for girls. High and moderate positive correlations for lower limbs were also noted for upper limbs: r = 0.74-0.86 for boys and r = 0.67-0.82 for girls. The reference values for appendicular muscle strength established in this study demonstrated a high and positive correlation between appendicular mass and muscle strength. These data will be useful when evaluating conditions and diseases affecting muscle or sports.

Why are there race/ethnic differences in adult body mass index-adiposity relationships? A quantitative critical review

Body mass index (BMI) is now the most widely used measure of adiposity on a global scale. Nevertheless, intense discussion centers on the appropriateness of BMI as a phenotypic marker of adiposity across populations differing in race and ethnicity. BMI-adiposity relations appear to vary significantly across race/ethnic groups, but a collective critical analysis of these effects establishing their magnitude and underlying body shape/composition basis is lacking. Accordingly, we systematically review the magnitude of these race-ethnic differences across non-Hispanic (NH) white, NH black and Mexican American adults, their anatomic body composition basis and potential biologically linked mechanisms, using both earlier publications and new analyses from the US National Health and Nutrition Examination Survey. Our collective observations provide a new framework for critically evaluating the quantitative relations between BMI and adiposity across groups differing in race and ethnicity; reveal new insights into BMI as a measure of adiposity across the adult age-span; identify knowledge gaps that can form the basis of future research and create a quantitative foundation for developing BMI-related public health recommendations.

Scaling of adult body weight to height across sex and race/ethnic groups: relevance to BMI

BACKGROUND

Body mass index (BMI) is formulated on the assumption that body weight (BW) scales to height with a power of 2 (BW∝height(2)), independent of sex and race-ethnicity. Powers differing from 2 are observed in studies of selected samples, thus raising the question if BMI is a generalizable metric that makes BW independent of height across populations.

OBJECTIVES

The objectives were to test the hypothesis that adult BW scales to height with a power of 2 independent of sex and race-ethnicity and to advance an understanding of BMI as a measure of shape by extending allometric analyses to waist circumference (WC).

DESIGN

We conducted cross-sectional subject evaluations, including body composition, from the NHANES and the Korean NHANES (KNHANES). Variations of the allometric model (Y = αX(β)) were used to establish height scaling powers (β ± SE) across non-Hispanic white and black, Mexican American, and Korean men and women.

RESULTS

Exploratory analyses in population samples established age and adiposity as important independent determinants of height scaling powers (i.e., β). After age and adiposity in the next series of analyses were controlled for, BW scaling powers were nonsignificantly different between race/ethnic groups within each sex group; WC findings were similar in women, whereas small but significant between-race differences were observed in the men. Sex differences in β values were nonsignificant except for BW in non-Hispanic blacks and WC in Koreans (P < 0.05). Nationally representative powers for BW were (NHANES/KNHANES) 2.12 ± 0.05/2.11 ± 0.06 for men and 2.02 ± 0.04/1.99 ± 0.06 for women and for WC were 0.66 ± 0.03/0.67 ± 0.05 for men and 0.61 ± 0.04/0.56 ± 0.05 for women.

CONCLUSIONS

Adult BW scales to height with a power of ∼2 across the 8 sex and race/ethnic groups, an observation that makes BMI a generalizable height-independent measure of shape across most populations. WC also follows generalizable scaling rules, a finding that has implications for defining body shape in populations who differ in stature.

Scaling of adult regional body mass and body composition as a whole to height: Relevance to body shape and body mass index

OBJECTIVES

Adult body mass (MB) empirically scales as height (Ht) squared (MB ∝ Ht(2) ), but does regional body mass and body composition as a whole also scale as Ht(2) ? This question is relevant to a wide range of biological topics, including interpretation of body mass index (BMI).

METHODS

Dual-energy X-ray absorptiometry (DXA) was used to quantify regional body mass [head (MH), trunk, arms, and legs] and whole-body composition [fat, lean soft tissue (LST), and bone mineral content (BMC)] in non-Hispanic (NH) white, NH black, Mexican American, and Korean adults participating in the National Health and Nutrition Examination Survey (NHANES; n = 17,126) and Korean NHANES (n = 8,942). Regression models were developed to establish Ht scaling powers for each measured component with adjustments for age and adiposity.

RESULTS

Exploratory analyses revealed a consistent scaling pattern across men and women of the four population groups: regional mass powers, head (∼0.8-1) < arms and trunk (∼1.8-2.3) < legs (∼2.3-2.6); and body composition, LST (∼2.0-2.3) < BMC (∼2.1-2.4). Small sex and population differences in scaling powers were also observed. As body mass scaled uniformly across the eight sex and population groups as Ht(∼2) , tall and short subjects differed in body shape (e.g., MH/MB ∝ Ht(-∼1) ) and composition.

CONCLUSIONS

Adult human body shape and relative composition are a function of body size as represented by stature, a finding that reveals a previously unrecognized phenotypic heterogeneity as defined by BMI. These observations provide new pathways for exploring mechanisms governing the interrelations between adult stature, body morphology, biomechanics, and metabolism.

Body fat percentiles of Brazilian adolescents according to age and sexual maturation: a cross-sectional study

BACKGROUND

The objective of this study was to determine body fat percentiles of adolescents in the city of São Paulo, Brazil, according to gender, age, and sexual maturation.

METHODS

This study involved 4,690 adolescents aged 10-15 years across 31 schools in the city of São Paulo. Sexual maturation was assessed in terms of Tanner stage. The body fat percentage was calculated using skinfold thickness. Percentile curves were calculated using the LMS (curve, mean, and coefficient of variation) method.

RESULTS

The mean body fat percentages were lower in boys aged 10-12 and 13-15 years than in girls. Body fat percentages decreased progressively with sexual maturation in boys, but increased in girls. The 85th, 95th, and 97th percentiles represent the cutoff points for moderately elevated, elevated, and very elevated body fat percentages, respectively, in pre-pubescent boys (85th, 95th, and 97th percentiles: 32.54, 95 41.04, and 97, respectively) and pubescent boys (31.09, 36.30, and 44.33, respectively). These cutoff points were lower in pre-pubescent girls (29.52, 35.01, and 41.82, respectively) and in the 97th percentile in pubescent girls (31.55, 36.20, and 41.86, respectively).

CONCLUSION

To our knowledge, these are the first body fat percentages cutoff points according to sexual maturation for adolescents aged 10-15 years in Brazil. Our results provide a significant contribution to the assessment of body composition in this population.

Influence of lean body mass and strength on landing energetics

PURPOSE

Less lean body mass may limit one's ability to produce adequate muscle forces to safely control landing from a jump, thus increasing the risk for injury. The primary objective of this study was to determine the effect of lower extremity lean mass (LELM) and eccentric muscle strength on lower extremity energy absorption (EA) during a drop jump landing.

METHODS

Seventy athletic subjects (35 men and 35 women) were measured for LELM with dual-energy x-ray absorptiometry, maximal eccentric strength of the quadriceps (QuadECC) and hamstrings (HamECC), and lower extremity joint energetics during the initial landing of a drop jump. A mediation analysis examined the extent to which LELM predicted EA at each lower extremity joint (EAHIP, EAKNEE, and EAANK) and subsequently whether these relationships were mediated by each subject's maximal eccentric strength capabilities.

RESULTS

LELM was a significant predictor of EAKNEE (R = 0.22, P < 0.01) in females but not in males (R = 0.03, P = 0.16). In females, QuadECC was a significant mediator of the effect of LELM on EA at the knee (ab = 179.72, 95% confidence interval [CI] = 10.43-423.42) and ankle (ab = 1.71, 95% CI = [0.16, 3.94]), whereas HamECC was a significant mediator of the relationship between LELM and EAHIP (ab = 4.89, 95% CI = 2.05-8.40). No significant relationships were observed in males.

CONCLUSIONS

LELM was a significant factor in energetic capabilities for females but not males. For females, this relationship was evident secondary to the stronger underlying relationship between maximal strength and EA. Thus, the maximal eccentric strength capabilities may be a more important determinant of energetic behaviors compared with the available quantity of lean mass alone. More work is needed to investigate these relationships and to reveal the underlying sex-specific mechanisms that determine EA capabilities.

Pubescent male students' attitudes towards menstruation in Taiwan: implications for reproductive health education and school nursing practice

AIM

To explore male students' attitudes towards menstruation.

BACKGROUND

Menstruation is a biological event that is often surrounded by secrecy and social stigma that causes anxiety amongst many young girls. A key element of this is the attitudes of young males towards this reproductive health issue. However, the literature around what young males think and feel about menstruation is limited.

DESIGN

Qualitative.

METHODS

A sample of 27 male students aged between 10-12 years participated in five focus groups. Data were then subject to a thematic analysis.

RESULTS

Five themes emerged from the data analysis that reflected the boys' feelings, experiences and attitudes towards menstruation: 'A silent topic', 'An unimportant issue', 'Errant information about menstruation'. In addition, according to their experience, participants gradually came to see menstruation from the 'menstrual stereotype' viewpoint. In their social life, they made choices that resulted in gradually regulating their behaviour that affected their 'relationships with girls'.

CONCLUSION

Young boys have misguided knowledge about menstruation and this helps to perpetuate the stigma surrounding this element of reproductive health. Boys also express a desire to learn more but are often restricted in this by home and school. School nurses are the best placed professionals to address this issue.

RELEVANCE TO CLINICAL PRACTICE

Menstrual education with boys should take a greater prominence than it often does in sexual health education in schools. Such inclusion will provide boys with a balanced and accurate knowledge base and therefore help towards reducing the social stigma around menstruation that is often experienced by young girls.

Sexual dimorphism of adipose tissue distribution across the lifespan: a cross-sectional whole-body magnetic resonance imaging study

BACKGROUND

Despite increasing research and clinical significance, limited information is available on how the visceral and subcutaneous adipose tissue (VAT and SAT) compartments develop during growth and maturation and then vary in volume across the adult lifespan. The present study aimed at exploring how adipose tissue compartments partition across the lifespan.

METHODS

Total body VAT and SAT were quantified in an ethnically-diverse cross-sectional sample of healthy subjects ages 5 - 88 yrs [children (5-17 years): males n = 88, BMI percentile (X ± SD), 61.9 ± 27.1; females, n = 59, BMI percentile, 60.0 ± 28.4; adults (≥ 18 yrs): males, n = 164, BMI, 25.6 ± 3.7 kg/m², and females, n = 188, BMI, 25.5 ± 5.4 kg/m²]. Subjects completed a whole-body magnetic resonance imaging scan and images were then segmented for VAT and SAT; total compartment volumes were calculated from respective slice areas. Sex and age distributions were evaluated by generating quadratic and cubic smoothing lines fitted to the data. Plots were developed with and without adjustment for total adipose tissue, ethnicity, and menopausal status in women. VAT and SAT volumes were both larger with greater age.

RESULTS

In adulthood, VAT was larger in males than in females with and without adjustment. In contrast, SAT volume was larger in females than in males after entering puberty and sex differences remained, with and without adjustment, across the remaining lifespan.

CONCLUSION

Based on observations made in this cross-sectional sample, VAT and SAT volumes were variably larger with greater age across most of the human lifespan, although the relatively small number of children warrants future larger scale studies to validate our observations. Moreover, the pattern and magnitude of adipose tissue "growth" differed between males and females, with the mechanistic basis of this sexual dimorphism only partially understood. These descriptive observations in a large cross-sectional cohort provide an initial foundation for future longitudinal and cohort studies.

Menstrual and menarche experience among pubescent female students in Taiwan: implications for health education and promotion practice

AIMS AND OBJECTIVES

This study aimed to explore the menarche and menstruation experiences of young females aged 10-12 years in elementary education in Taiwan.

BACKGROUND

Menarche is a significant milestone in a woman's life and for female adolescents it is a sharply defined biological event that can be a traumatic and uncomfortable time. If used, school nurses can make a significant contribution in educating young people and help to ameliorate these problems. Understanding how young women feel about menstruation is a central element to sexual health education practice.

DESIGN

A qualitative research design was employed using focus groups.

METHODS

Data were collected from 20 female students, aged between 10-12 years. Focus groups were recorded, transcribed and subject to a thematic analysis.

RESULTS

Three themes emerged from the data analysis reflecting the menstrual experience of participants. These were: 'Changing bodies: the physical effects of menarche and menstruation', 'Emotional issues: the psychological impact of menarche and menstruation' and 'Social dimensions of the menarche and menstruation'.

CONCLUSION

Our findings show that young females can experience significant physical and emotional difficulties around menstruation - many of which stem from poor information and the reactions of their peer group to menstrual activity. The potential for school nurses to contribute to this education is significant and schools should explore the manner in which nurses can contribute to this area of health education.

RELEVANCE TO CLINICAL PRACTICE

Nurses involved in health education work with young people and ensure that menstruation education addresses the social and psychological impact of the menarche as well as the physical elements of menstruation. Boys should not be absent from this education and the impact of their attitudes towards menstruation upon their female peers should be addressed in health education work.