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

How Much the Swimming Performance Leading to Tokyo 2020 Olympic Games Was Impaired Due to the Covid-19 Lockdown?

The aim of this study was to analyze the progression and stability in the performance of world-ranked swimmers from 2015 to 2020, and the impairment induced by the COVID-19 lockdown. An observational retrospective design over five consecutive competitive seasons was selected. FINA's male Top-50 who were qualified for the Tokyo Olympic Games were considered in freestyle, backstroke, backstroke, and butterfly events. A total of 515 male swimmers and 2060 season-best performances were analyzed. All data was retrieved from two open-access and public websites (Swimrankings and Swimcloud). Repeated measures ANOVA followed by the Bonferroni post-hoc test was performed to analyze the variation between seasons. Stabilization in performance was assessed using spearman correlation coefficients. A significant improvement in performance ≈0.5-2.5% was found in most of the strokes and race distances until the 2018-2019 season. The 2020 lockdown impaired the performance by 1-2%. Moderate to high associations were found in the 2017-2018 season when considering the 2019-2020 performance. The breaststroke was the only stroke with a moderate-high stability (r > 0.40) in all race distances considering the overall time period. It can be concluded that world-ranked swimmers' performance was impaired by 1-2% due to the COVID-19 lockdown, returning to levels that were reached two years earlier.

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.

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.