The aim of this study was to determine if gender differences in muscle mass explain the gender differences in running and cycling sprint performance. Body composition (dual-energy X-ray absorptiometry), and running (30 and 300 m test) and cycling (Wingate test) sprint performance were assessed in 123 men and 32 women. Peak power (PP) output in the Wingate test expressed per kg of lower extremities lean mass (LM) was similar in males and females (50.4 +/- 5.6 and 50.5 +/- 6.2 W kg(-1), P = 0.88). No gender differences were observed in the slope of the linear relation between LM and PP or mean power output (MP). However, when MP was expressed per kg of LM, the males attained a 22% higher value (26.6 +/- 3.4 and 21.9 +/- 3.2 W kg(-1), P < 0.001). The 30 and 300-m running time divided by the relative lean mass of the lower extremities (RLM = LM x 100/body mass) was significantly lower in males than in females. Although, the slope of the linear relationship between RLM and 300-m running time was not significantly different between genders, the males achieved better performance in the 300-m test than the females. The main factor accounting for gender differences in peak and mean power output during cycling is the muscle mass of the lower extremities. Although, the peak power generating capability of the muscle is similar in males and females, muscle mass only partially explains the gender difference in running sprints, even when expressed as a percentage of the whole body mass.

Summary Background Sustainable Development Goal 3.2 has targeted elimination of preventable child mortality, reduction of neonatal death to less than 12 per 1000 livebirths, and reduction of death of children younger than 5 years to less than 25 per 1000 livebirths, for each country by 2030. To understand current rates, recent trends, and potential trajectories of child mortality for the next decade, we present the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 findings for all-cause mortality and cause-specific mortality in children younger than 5 years of age, with multiple scenarios for child mortality in 2030 that include the consideration of potential effects of COVID-19, and a novel framework for quantifying optimal child survival. Methods We completed all-cause mortality and cause-specific mortality analyses from 204 countries and territories for detailed age groups separately, with aggregated mortality probabilities per 1000 livebirths computed for neonatal mortality rate (NMR) and under-5 mortality rate (U5MR). Scenarios for 2030 represent different potential trajectories, notably including potential effects of the COVID-19 pandemic and the potential impact of improvements preferentially targeting neonatal survival. Optimal child survival metrics were developed by age, sex, and cause of death across all GBD location-years. The first metric is a global optimum and is based on the lowest observed mortality, and the second is a survival potential frontier that is based on stochastic frontier analysis of observed mortality and Healthcare Access and Quality Index. Findings Global U5MR decreased from 71·2 deaths per 1000 livebirths (95% uncertainty interval [UI] 68·3–74·0) in 2000 to 37·1 (33·2–41·7) in 2019 while global NMR correspondingly declined more slowly from 28·0 deaths per 1000 live births (26·8–29·5) in 2000 to 17·9 (16·3–19·8) in 2019. In 2019, 136 (67%) of 204 countries had a U5MR at or below the SDG 3.2 threshold and 133 (65%) had an NMR at or below the SDG 3.2 threshold, and the reference scenario suggests that by 2030, 154 (75%) of all countries could meet the U5MR targets, and 139 (68%) could meet the NMR targets. Deaths of children younger than 5 years totalled 9·65 million (95% UI 9·05–10·30) in 2000 and 5·05 million (4·27–6·02) in 2019, with the neonatal fraction of these deaths increasing from 39% (3·76 million [95% UI 3·53–4·02]) in 2000 to 48% (2·42 million; 2·06–2·86) in 2019. NMR and U5MR were generally higher in males than in females, although there was no statistically significant difference at the global level. Neonatal disorders remained the leading cause of death in children younger than 5 years in 2019, followed by lower respiratory infections, diarrhoeal diseases, congenital birth defects, and malaria. The global optimum analysis suggests NMR could be reduced to as low as 0·80 (95% UI 0·71–0·86) deaths per 1000 livebirths and U5MR to 1·44 (95% UI 1·27–1·58) deaths per 1...

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The aim of the present systematic review was to assess and provide an up-to-date analysis of the impact of coronavirus disease 2019 (COVID-19) pandemic on the health-related quality of life (HRQoL) of children and adolescents. Thus, an electronic search of the literature, in two well-known databases (PubMed and Web of Science), was performed until February 2021 (without date restriction). PRISMA guideline methodology was employed and data regarding the HRQoL were extracted from eligible studies. Articles were included if they met the following inclusion criteria: (a) children and/or adolescent population (4 to 19 years old); (b) HRQoL as a main assessment; (c) German, Spanish, Portuguese, French, and English language; and (d) pre-pandemic and during pandemic HRQoL data. Following the initial search, 241 possible related articles were identified. A total of 79 articles were identified as duplicates. Moreover, 129 articles were removed after reading the title and abstract. Of the remaining 33 articles, 27 were removed since they were not focused on children or adolescents (n = 19), articles did not report pre- and post- pandemic HRQoL values (n = 6), articles were not focused on HRQoL (n = 6), and one article was an editorial. Finally, six studies fulfilled the inclusion criteria and, therefore, were included in the systematic review. A total of 3177 children and/or adolescents during COVID-19 were included in this systematic review. Three articles showed that COVID-19 pandemic significantly impacted the HRQoL of children and adolescents, and another did not report comparison between pre- and during COVID-19 pandemic, although a reduction in the HRQoL can be observed. Nevertheless, two articles did not find significant changes and another one did not report p-values. Regarding sex differences, only two studies analyzed this topic, observing no differences between girls and boys in the impact of COVID-19 pandemic on HRQoL. Taking into account these results, this systematic review might confirm that COVID-19 has a negative impact on the HRQoL of children and/or adolescents.

Objective Our objective was to explore the training-related knowledge, beliefs, and practices of athletes and the influence of lockdowns in response to the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods Athletes (n = 12,526, comprising 13% world class, 21% international, 36% national, 24% state, and 6% recreational) completed an online survey that was available from 17 May to 5 July 2020 and explored their training behaviors (training knowledge, beliefs/attitudes, and practices), including specific questions on their training intensity, frequency, and session duration before and during lockdown (March–June 2020). Results Overall, 85% of athletes wanted to “maintain training,” and 79% disagreed with the statement that it is “okay to not train during lockdown,” with a greater prevalence for both in higher-level athletes. In total, 60% of athletes considered “coaching by correspondence (remote coaching)” to be sufficient (highest amongst world-class athletes). During lockdown, < 40% were able to maintain sport-specific training (e.g., long endurance [39%], interval training [35%], weightlifting [33%], plyometric exercise [30%]) at pre-lockdown levels (higher among world-class, international, and national athletes), with most (83%) training for “general fitness and health maintenance” during lockdown. Athletes trained alone (80%) and focused on bodyweight (65%) and cardiovascular (59%) exercise/training during lockdown. Compared with before lockdown, most athletes reported reduced training frequency (from between five and seven sessions per week to four or fewer), shorter training sessions (from ≥ 60 to < 60 min), and lower sport-specific intensity (~ 38% reduction), irrespective of athlete classification. Conclusions COVID-19-related lockdowns saw marked reductions in athletic training specificity, intensity, frequency, and duration, with notable within-sample differences (by athlete classification). Higher classification athletes had the strongest desire to “maintain” training and the greatest opposition to “not training” during lockdowns. These higher classification athletes retained training specificity to a greater degree than others, probably because of preferential access to limited training resources. More higher classification athletes considered “coaching by correspondence” as sufficient than did lower classification athletes. These lockdown-mediated changes in training were not conducive to maintenance or progression of athletes’ physical capacities and were also likely detrimental to athletes’ mental health. These data can be used by policy makers, athletes, and their multidisciplinary teams to modulate their practice, with a degree of individualization, in the current and continued pandemic-related scenario. Furthermore, the data may drive training-related educational resources for athletes and their multidisciplinary teams. Such upskilling would provide athletes with evidence to inform their training modifications in response to germane situations (e.g., COVID related, injury, and illness).

Objective: To analyse the effect of extracurricular physical activities on fat mass accumulation and physical fitness during growth in early pubertal males. Design: Longitudinal study. Subjects: A total of 42 male children (9.471.4 years, Tanner I-II and 12.771.5 years, Tanner III-IV, before and after the 3.3 years follow-up, respectively), randomly sampled from the population of Gran Canaria (Spain), 26 of them physically active (PA, at least 3 h per week during 3 years) and 16 non-physically active (non-PA). Measurements: Body composition (dual-energy X-ray absorptiometry), anthropometrics (body circumferences and skinfolds) and physical fitness variables (dynamic and isometric force, anaerobic capacity and maximal aerobic power) were determined in all subjects. Results: Both groups had comparable body sizes at the start and the end of the study. Body mass index increased with growth more in the PA than in the non-PA group (Po0.05). However, fat mass accumulation with growth was lower in the PA than in the non-PA (Po0.05). There was a positive relationship between the increment of total and trunkal fat mass, especially in nonactive children (r 2 ¼ 0.93). In contrast, there was an inverse relationship between the total lean mass growth and the accumulation of total and regional fat mass (r ¼ À0.37 to À0.41, all Po0.05). Physical fitness was maintained in the PA, while it worsened in the non-PA children. Conclusions: Without any dietary intervention, children who regularly participate in at least 3 h per week of sports activities are more protected against total and regional fat mass accumulation. They also increase their total lean and bone mass to a greater extent than children who do not participate in extracurricular sport activities. In addition, PA children maintain their physical fitness during growth, while it deteriorates in the non-PA children.

Background: The Global Matrix 4.0 on physical activity (PA) for children and adolescents was developed to achieve a comprehensive understanding of the global variation in children’s and adolescents’ (5–17 y) PA, related measures, and key sources of influence. The objectives of this article were (1) to summarize the findings from the Global Matrix 4.0 Report Cards, (2) to compare indicators across countries, and (3) to explore trends related to the Human Development Index and geo-cultural regions. Methods: A total of 57 Report Card teams followed a harmonized process to grade the 10 common PA indicators. An online survey was conducted to collect Report Card Leaders’ top 3 priorities for each PA indicator and their opinions on how the COVID-19 pandemic impacted child and adolescent PA indicators in their country. Results: Overall Physical Activity was the indicator with the lowest global average grade (D), while School and Community and Environment were the indicators with the highest global average grade (C+). An overview of the global situation in terms of surveillance and prevalence is provided for all 10 common PA indicators, followed by priorities and examples to support the development of strategies and policies internationally. Conclusions: The Global Matrix 4.0 represents the largest compilation of children’s and adolescents’ PA indicators to date. While variation in data sources informing the grades across countries was observed, this initiative highlighted low PA levels in children and adolescents globally. Measures to contain the COVID-19 pandemic, local/international conflicts, climate change, and economic change threaten to worsen this situation.

Long-term soccer participation, starting at a prepubertal age, results in greater improvement of physical fitness, greater acquisition of bone mass and a lower accumulation of body fat.