Running sprint force-velocity-power profile obtained with a low-cost and low frame rate acquisition video technique: reliability and concurrent validity.

The Force-velocity (F-v) and Power-velocity (P-v) relationships quantify athlete's horizontal force production capacities during sprinting. Efforts are underway to enhance ecological validity for practitioners and sports coaches. This study provides detailed data comparison of a low frames per second setup (30 Hz; FPSlow) with splits from a high FPS camera to derive F-v and P-v relationships. Sixty-six sprints performed by 11 university track and field athletes (6 male, 5 female) were evaluated. Data were recorded using FPSlow, photocells, and a high-speed camera (240 Hz; MySprint). In the FPSlow setup, bias was 0.17s, and Limits of agreement was 0.09s compared to photocells. ICC was 1.00, and the coefficient of variation (CV) was 1.0% [0.8-1.1%]. Time acquisition comparison between MySprint and FPSlow setups revealed high consistency (ICC = 0.99) and low CV (2.9% [2.8-3.1%]). F-v profile variables exhibited biases from trivial to small, with ICC ranging from moderate to nearly perfect. CV ranged from 2.7% to 11.8%, and improved using the average of three sprints (CV between 1.8% and 8.6%). The 'simple method' applied to data from the low FPS video setup yielded kinetic and kinematic parameters comparable to those obtained by the validated previous method and photocells.

Monitoring Bar Velocity to Quantify Fatigue in Resistance Training.

We analyzed the effects of load magnitude and bar velocity variables on sensitivity to fatigue. Seventeen resistance-trained men (age=25.7±4.9 years; height=177.0±7.2 cm; body mass=77.7±12.3 kg; back-squat 1RM=145.0±33.9 kg; 1RM/body mass=1.86) participated in the study. Pre- and post-exercise changes in the mean propulsive velocity (MPV) and peak velocity (PV) in the back-squat at different intensities were compared with variations in the countermovement jump (CMJ). CMJ height decreased significantly from pre- to post-exercise (∆%=-7.5 to -10.4; p<0.01; ES=0.37 to 0.60). Bar velocity (MPV and PV) decreased across all loads (∆%=-4.0 to -12.5; p<0.01; ES=0.32 to 0.66). The decrease in performance was similar between the CMJ, MPV (40% and 80% 1RM; p=1.00), and PV (80% 1RM; p=1.00). The magnitude of reduction in CMJ performance was greater than MPV (60% 1RM; p=0.05) and PV (40% and 60% 1RM; p<0.01) at the post-exercise moment. Low systematic bias and acceptable levels of agreement were only found between CMJ and MPV at 40% and 80% 1RM (bias=0.35 to 1.59; ICC=0.51 to 0.71; CV=5.1% to 8.5%). These findings suggest that the back-squat at 40% or 80% 1RM using MPV provides optimal sensitivity to monitor fatigue through changes in bar velocity.

Relative age effect on muscle power in Brazilian youth: a population study / Efeito da idade relativa na potência muscular em jovens brasileiros: um estudo de população

Abstract This study aimed to examine the relative age effect on muscle power in a large sample of Brazilian children and adolescents. The sample consisted of 87,766 girls and boys aged 7-16 years, data collected in repeated cross-sectional surveillance carried out since 1999. The participants were grouped into four age subgroups within each chronological age based on birthdates. Upper and lower limbs muscle power were assessed using the 2-Kg medicine ball throw and horizontal jump tests, respectively. The normative distribution of physical fitness components was used for classification. The results showed a significant association between relative age and normative classification of muscle power. Among boys, there was a sequential increase in the frequency of individuals classified as "very good/excellent" as the relative age increased. A similar trend was observed among girls. The findings provided evidence of a relative age effect on muscle power in Brazilian children and adolescents. These findings have implications for the organization of structured physical activities and sports, as early-born individuals may have an advantage in performance. Further research is needed to explore the underlying mechanisms and potential interventions to mitigate the relative age effect and promote equal opportunities for all youth in physical activities and sports.

Resumo Este estudo teve como objetivo examinar o efeito da idade relativa na potência muscular em crianças e adolescentes brasileiros. A amostra foi composta por 87.766 meninas e meninos com idades entre 7 e 16 anos. Os participantes foram agrupados em quatro subgrupos etários dentro de cada idade cronológica tendo como base as datas de nascimento e da coleta dos dados. A potência muscular dos membros superiores e inferiores foi avaliada por meio dos testes de arremesso de medicine ball de 2 kg, e salto horizontal, respectivamente. A distribuição normativa (fraco; razoável; bom; muito bom; excelente) dos dois testes de potência foi utilizada para a classificação. Os resultados mostraram associação significativa entre os subgrupos etários e a classificação normativa da potência muscular. Entre os meninos, houve aumento na frequência de indivíduos classificados como "muito bom/excelente" à medida que a idade relativa aumentava. Uma tendência semelhante foi observada entre as meninas. Os achados forneceram evidências do efeito de idade relativa na potência muscular de crianças e adolescentes brasileiros. Esses resultados têm implicações práticas na organização de atividades físicas estruturadas e esportes em diferentes contextos, pois indivíduos nascidos mais cedo podem ter vantagem no desempenho em tarefas que exijam potência muscular. Mais pesquisas são necessárias para explorar os mecanismos subjacentes e intervenções que possam mitigar o efeito de idade relativa e promover oportunidades iguais para todas as crianças e adolescentes nas atividades físicas e esportes.

Are relative age effects pervasive in lower competitive tiers of school sports? An investigation of student-athletes from Minas Gerais / Los efectos de la edad relativa son dominantes en los niveles menos competitivos del deporte escolar? Una investigación de estudiantes-deportistas de minas gerais / Os efeitos da idade relativa são pervasivos nos níveis menos competitivos do esporte escolar? Uma investigação de estudantes-atletas de Minas Gerais

Este estudio investigaba el Efecto de la Edad Relativa (EEA) en atletas escolares, según categorías y género. Han sido analizados 1356 jugadores masculinos y 1044 femeninas (de 9 a 17 años) que participaron en competencias escolares en Minas Gerais-Brasil en 2018 y/o 2019 en las categorías Sub-11, Sub-14 y/o Sub-17. Los jugadores fueron divididos en cuartos, de acuerdo con el mes de nacimiento: Q1 (enero-marzo), Q2 (abril-junio), Q3 (julio-septiembre) y Q4 (octubre-diciembre). Se realizaron pruebas de chi-cuadrado para verificar la presencia de EEA. El nivel de significación fue 5%. La distribución observada difirió de la esperada cuando todos los jugadores fueron analizados juntos (p = 0.019; ⍵ = 0.06), y en los hombres, cuando los jugadores fueron analizados por género (p = 0.017; ⍵ = 0.09). En ambos casos se encontró una mayor proporción de jugadores nacidos en los primeros meses del año (p < 0.008). Los resultados indicaron una distribución desigual de nacimientos en la categoría Sub-11 (p < 0.001; ⍵ = 0.25), en la que deportistas nacidos en Q1 y Q2 fueron más frecuentes (p < 0.001). Cuando se analizaron juntos categoría y género, se observó que atletas nacidos en Q1 fueron más frecuentes que los deportistas nacidos en Q3 (p < 0.002) y Q4 (p < 0.001) en la Sub-11, independientemente del género (p < 0.002), pero no en las categorías Sub-14 y Sub-17. Teniendo en cuenta que el deporte escolar puede ser el primer paso para alcanzar mayores niveles competitivos, es importante instruir a los entrenadores sobre el EEA, con el fin de reducir las desigualdades en el acceso al deporte escolar. (AU)

This study investigated the Relative Age Effect (RAE) in school athletes, according to sex and age categories. Birthdates from 1356 male and 1044 female athletes (aged 9 to 17 years) who played scholar competitions in Minas Gerais-Brazil in 2018 and/or 2019 in categories Under-11, Under-14 and/or Under-17 were analyzed. Athletes were divided into quarters according to their month of birth: Q1 (January-March), Q2 (April-June), Q3 (July-September), and Q4 (October-December). Chi-squared tests were performed to verify the presence of RAE. The significance level was set at 5%. The observed distribution was different from expected when all athletes were analyzed together (p = 0.019; ⍵= 0.06), and in males when athletes were analyzed separately by sex (p = 0.017; ⍵= 0.09). Athletes born in the three first months of the year were more frequent in both cases (p < 0.008). The age category analyses indicated uneven distribution of births in Under-11 category (p < 0.001; ⍵= 0.25), where athletes born in Q1 and Q2 were more frequent (p < 0.001). When age category and sex were considered together, it was observed that athletes born in Q1 were more frequent than athletes born in Q3 (p < 0.002) and Q4 (p < 0.001) in the U-11 category regardless of sex (p < 0.002), but not in the Under-14 and Under-17 categories. Considering that school sport can be the first step towards achieving higher competitive levels, it is important to instruct coaches about RAE, in order to reduce inequalities in the access to school sport. (AU)

Este estudo investigou o Efeito da Idade Relativa (EIR) em atletas escolares, de acordo com categorias e sexo. Analisaram-se datas de nascimento de 1356 atletas do sexo masculino e 1044 do sexo feminino (de 9 a 17 anos) que participaram de competições escolares em Minas Gerais-Brasil em 2018 e/ou 2019 nas categorias Sub-11, Sub-14 e/ou Sub-17. Os atletas foram divididos em quartis, de acordo com o mês de nascimento: Q1 (janeiro-março), Q2 (abril-junho), Q3 (julho-setembro) e Q4 (outubro-dezembro). Realizaram-se testes de chi-quadrado para verificar a presença do EIR. O nível de significância adotado foi de 5%. A distribuição observada diferiu do esperado quando todos os atletas foram analisados em conjunto (p = 0.019; ⍵= 0.06), e no sexo masculino, quando os atletas foram analisados por sexo (p = 0.017; ⍵= 0.09). Encontrou-se maior proporção de atletas nascidos nos primeiros meses do ano em ambos os casos (p < 0.008). Os resultados indicaram uma distribuição desigual de nascimentos na categoria Sub-11 (p < 0.001; ⍵= 0.25), onde atletas nascidos nos Q1 e Q2 foram mais frequentes (p < 0.001). Quando a categoria e o sexo foram analisados conjuntamente, se observou que atletas nascidos no Q1 foram mais frequentes que atletas nascidos em Q3 (p < 0.002) e Q4 (p < 0.001) no Sub-11, independentemente do sexo (p < 0.002), mas não nas categorias Sub-14 e Sub-17. Considerando que o esporte escolar pode ser o primeiro passo para alcançar maiores níveis competitivos, é importante instruir os treinadores sobre o EIR, a fim de reduzir as desigualdades de oportunidades de acesso ao esporte escolar. (AU)

Analysis of velocity- and power-load relationships of the free-weight back-squat and hexagonal bar deadlift exercises.

The aim of this study was to analyse the load-velocity and load-power relationships in the free-weight back-squat (BSQ) and hexagonal bar deadlift (HBD) exercises. Twenty-five (n = 25) resistance-trained men (age = 23.7 ± 2.8 years) performed a progressive load test at maximal intended velocity to determine their BSQ and HBD one-repetition maximum (1RM). Mean propulsive velocity (MPV) during the concentric phase of the lift was recorded through a linear encoder. Load-velocity and load-power relationships were analysed by fitting linear regression and the second-order polynomial, respectively, to the data. Maximum strength (1RM), MPV (30-80% 1RM), and power output (30-90% 1RM) were higher for HBD compared to BSQ exercise (p < 0.05). A very strong relationship between MPV and relative intensity was found for both BSQ (R2 = 0.963) and HBD (R2 = 0.967) exercises. The load that maximizes power output (Pmax) was 64.6 ± 2.9% (BSQ) and 59.6 ± 1.1% (HBD) 1RM. There was a range of loads at which power output was not different than Pmax (BSQ: 40-80% 1RM; HBD: 50-70% 1RM). In conclusion, the load-velocity and load-power relationships might assist strength and conditioning coaches to monitor and prescribe exercise intensity in the BSQ and HBD exercises using the velocity-based training approach.

Risk or benefit? Side effects of caffeine supplementation in sport: a systematic review.

PURPOSE: The aim of this study was to systematically review evidence on the prevalence and magnitude of side effects associated with caffeine supplementation in athletes. METHODS: Systematic searches through the PubMed, VHL, Scopus, and Web of Science databases were conducted according to the PRISMA guidelines. Peer-reviewed articles written in English that reported the prevalence/percentage or magnitude/effect size of side effects after caffeine supplementation in athletes in a sports context were included. Studies were grouped by the dose of caffeine administered as follows: low = ≤ 3.0 mg/kg; moderate = from 3.1 to 6.0 mg/kg; high = ≥ 6.1 mg/kg. The magnitude of the side effects was calculated with effect sizes. RESULTS: The search retrieved 25 studies that met the inclusion/exclusion criteria with a pooled sample of 421 participants. The supplementation with caffeine produced a higher prevalence or magnitude of all side effects under investigation when compared to placebo/control situations. The prevalence (magnitude) was between 6 and 34% (ES between 0.13 and 1.11) for low doses of caffeine, between 0 and 34% (ES between -0.13 and 1.20) for moderate doses of caffeine, and between 8 and 83% (ES between 0.04 and 1.52) with high doses of caffeine. The presence of tachycardia/heart palpitations and the negative effects on sleep onset had the highest prevalence and magnitude, in athletes using supplementation with caffeine. CONCLUSION: In summary, caffeine supplementation in the doses habitually used to enhance physical performance produces several side effects, both after exercise and at least 24 h after the ingestion. However, the prevalence and magnitude of side effects with high doses of caffeine were habitually higher than with low doses of caffeine. From a practical perspective, using ~3.0 mg/kg of caffeine may be the dose of choice to obtain the ergogenic benefits of caffeine with the lowest prevalence and magnitude of side effects.

Did the Absence of Crowd Support During the Covid-19 Pandemic Affect the Home Advantage in Brazilian Elite Soccer?

This study aimed to investigate the impact of crowd absence due to the COVID-19 pandemic on home advantage in Series A and B of professional Brazilian male soccer. Moreover, we sought to compare the home advantage between different competitive levels. Data from 2018 to 2020 Brazilian professional soccer championships (Series A and B) were analyzed, consisting of 2280 matches. The effect of home advantage was calculated in relation to the number of points won, the number of wins, goals scored and goals conceded. Our results indicated that home advantage was reduced in Serie A. Specifically, the 2020 (absence of the crowd) and 2019 seasons showed smaller home advantage compared to the 2018 season. On the other hand, Serie B analyses indicated no changes in home advantage over the seasons analyzed. The comparison of home advantage between competitive levels indicated higher home advantage in Serie A, exclusively in the 2018 season. In addition to the absence of fans, other changes occurred in elite sports due to the pandemic, such as changes in rules and the calendar. Considering that home advantage is affected by multiple interacting factors, it is important to investigate specific sports leagues across the world to determine which factors had the greatest impact on the advantage of playing home matches.

Market value of Brazilian soccer players that played 2020 series A and B of the Brazilian championship: an analysis based on quarters of birth and playing position

Abstract Aim: The present study aimed to investigate the prevalence of RAE in soccer players from different positions in Series A and B in 2020 Brazilian soccer, as well as the impact of RAE on the estimated market value of these players. Methods: Data from 1080 male elite soccer athletes were analyzed. Athletes were grouped according to birth quarters: Q1 (January-March), Q2 (April-June), Q3 (July-September), and Q4 (October-December) and the competitive level (Series A or B). Chi-square tests (χ2) were performed to compare the birthdates' distribution of athletes according to a competitive level and playing positions. Kruskal-Wallis test was used to compare the market values of players born in each of the quarters of the year across competitive levels and playing positions. The significance level was set at 5%. Results: The overall analyses showed the prevalence of RAE in Series A and B, with an overrepresentation of athletes born in the first two quarters of the year. The RAE analysis based on playing positions showed different from expected distributions for forwards, midfielders, and defenders in Series A. In Series B, only midfielders showed a difference from the expected distribution. As for the market values analyses, no differences were found based on the athletes' birth quarters, regardless of competitive level or playing position. Conclusion: Our results indicate that, although RAE is prevalent in Series A and B of elite Brazilian soccer, it does not seem to influence players' estimated market values.

The use of real-time monitoring during flywheel resistance training programmes: how can we measure eccentric overload? A systematic review and meta-analysis.

This systematic review and meta-analysis aimed to analyse the technologies and main training variables used in the literature to monitor flywheel training devices in real time. In addition, as the main research question, we investigated how eccentric overload can be effectively monitored in relation to the training variable, flywheel shaft type device and the moment of inertia selected. The initial search resulted in 11,621 articles that were filtered to twenty-eight and seventeen articles that met the inclusion criteria for the systematic review and meta-analysis, respectively. The main technologies used included force sensors and rotary/linear encoders, mainly to monitor peak or mean force, power or speed. An eccentric overload was not always achieved using flywheel devices. The eccentric overload measurement was related to the main outcome selected. While mean force (p = 0.011, ES = -0.84) and mean power (p < 0.001, ES = -0.30) favoured the concentric phase, peak power (p < 0.001, ES = 0.78) and peak speed (p < 0.001, ES = 0.37) favoured the eccentric phase. In addition, the lower moments of inertia (i.e., from 0.01 to 0.2 kg·m2) and a cylindrical shaft type (i.e., vs conical pulley) showed higher possibilities to achieve eccentric overload. A wide variety of technologies can be used to monitor flywheel devices, but to achieve eccentric overload, a flywheel cylindrical shaft type with low moments of inertia is advised to be used.

Mental Fatigue From Smartphone Use Reduces Volume-Load in Resistance Training: A Randomized, Single-Blinded Cross-Over Study.

We investigated the acute effects of mental fatigue induced by 30-minute use of smartphone social network apps on volume load in resistance training among recreationally trained adults. Sixteen (n = 16) adults of both sexes performed three sets of a half back-squat exercise to failure with 80% of 15RM, interspersed with 3-minutes of passive recovery between sets, before and after two different cognitive tasks: (a) use of smartphone social network apps; and (b) watching a documentary. We assessed mechanical variables and ratings of perceived exertion during the strength exercise. Relative to the documentary-viewing control condition, a 30-minute exposure to smartphone social network apps led participants toward increased perception of mental fatigue (p = 0.004) and lower volume-load during the strength exercise (p = 0.006). There were no significant differences in perceived exertion between conditions (p = 0.54), participants' motivation (p = 0.277), intra-set mechanical variables (p > 0.05), or blood lactate concentrations (p = 0.36). Our findings of an isolated possible higher-than normal RPE without changes in physiological variables, accompanying the lower volume-load in the mentally-fatigued participants support psychological, rather than physiological, bases for mental fatigue effects.

Transcranial Stimulation Improves Volume and Perceived Exertion but does not Change Power.

This study aimed to analyze the acute effect of anodal transcranial direct current stimulation (a-tDCS) over the primary motor cortex (M1) on the volume, perceived exertion, and neuromuscular performance measurements in trained and untrained adults. Twenty-four male adults (12 trained and 12 untrained) participated in this single-blind, randomized, and sham-controlled study. The participants performed three back squat repetitions using the 15RM load with maximal concentric velocity to assess neuromuscular performance before tDCS and 30-min after resistance exercise. Next, they were randomly assigned to a-tDCS over M1 or the sham condition. Participants performed ten sets of parallel back squat with 15RM load and repetitions sustained to momentary muscular failure. The total number of repetitions was higher (p<0.05) and perceived exertion was lower (p<0.05) after a-tDCS in both groups. Peak power, velocity, and force decreased in both groups after the RE session (p<0.05), but with a higher rate in untrained individuals (p<0.05). No significant effect was found for peak power, peak velocity, and peak force (p>0.05). This study suggests that using a-tDCS may improve the total volume of repetitions and perceived exertion in trained and untrained individuals.

What is the effect of vigorous exercise on the brain?

Abstract Aims: This study aimed to verify whether vigorous exercise is capable of generating mental fatigue. Methods: To do so, 16 young adult male (29.4 ± 5.2 years old) cyclists (5.4 ± 4.6 years of training) underwent three visits: 1) control session (rest); 2) session with cognitive demand (20 minutes of AX-CPT); 3) session with vigorous exercise (10km time trial). Mental fatigue was assessed using the visual analog scale of fatigue in the pre-and post-session moments. A two-way ANOVA of repeated measures followed by the Bonferroni posthoc was used to verify the effect of the condition (control, cognitive demand, and exercise) and time (pre and post) interaction. The paired "t" test was used to compare the delta of mental fatigue (post - pre) of the sessions. The partial eta squared was used to determine the effect size of the variance. The significance adopted was p < 0.05. Results: A condition x time interaction was observed (F (2.30) = 5.349, p = 0.010, partial η2 = 0.263). When comparing the deltas, a mean difference was found between the control and vigorous exercise (p = 0.033) conditions and cognitive demand and vigorous exercise (p = 0.017) conditions. Control and cognitive demand sessions showed no difference (p = 0.801). Conclusion: The findings suggest that intense physical exercise seems to cause mental fatigue after practice.

Relative age effects in elite Brazilian track and field athletes are modulated by sex, age category, and event type

Abstract Aim: This study investigated the Relative Age Effect (RAE) in Brazilian track and field athletes based on sex, age category (U-16, U-18, U-20, U-23 and senior), and event type (sprints/hurdles, middle distance, long-distance, jumps, throws). Methods: Data from 2.259 male and 1.776 female elite track and field athletes, ranked top-50 in events held by the Brazilian Track and Field Confederation in 2019 were analyzed. To determine RAE athletes were divided into four quarters based on their months of birth, considering January 1st the cut-off date. The influence of sex, age category, and event types in the pervasion of RAE in Brazilian track and field athletes was assessed through Chi-squared tests. Results: Athletes born closer to the cut-off date were more frequent than athletes born further from this date were in male youth categories. This effect reduced as categories increased, even reversing in the senior category. Finally, RAE was more frequent in events in which athletic performance relies more on strength, speed, and power, which is the case of sprints/hurdles, jumps, and throws. Conclusion: RAE is particularly prevalent in young male Brazilian track and field athletes, which indicates that many potentially talented athletes are overlooked in youth tryouts because they were born months away from the cut-off date. Policies that reduce the disadvantages faced by relatively younger athletes are warranted in order to avoid the loss of potential sports talents.

Swimming and bone mineral density: a sport without osteogenic stimulation? / Natação e densidade mineral óssea: uma modalidade esportiva sem estímulo osteogênico? / Natación y densidad mineral ósea: ¿una modalidad deportiva sin estímulo osteogénico?

ABSTRACT Introduction: The osteogenic effects generated by different sports are the subject of a growing number of research projects. Regular physical activity is one of the main recommendations for the stimulation of bone mineral density (BMD). However, evidence has shown that not all physical activities promote similar effects. In this context, the osteogenic effects of swimming need to be clarified. Objective: To verify and compare total and regional BMD levels between male and female swimming athletes and university non-athletes. Methods: The sample, composed of 60 participants of both sexes, was divided into two groups: 30 swimming athletes (GA): 15 men (22.2 ± 3.92 years; 73.61 ± 16.55 kg; 1.76 ± 0.08 m) and 15 women (21.91 ± 2.21 years; 53.15 ± 8.36 kg; 1.64 ± 0.06 m) and a control group (CG): 30 university non-athletes: 15 men (20.73 ± 1.27 years; 74.4 ± 5.54 kg, 1.74 ± 0.04 m) and 15 women (19.93 ± 2.05 years; 59.72 ± 1.33 kg; 1.63 ± 0.004 m). BMD (total, arms, legs, pelvis and spine) was measured using dual energy X-ray absorptiometry (DXA). The results were compared with one-way ANOVA using Scheffé's post hoc test, when necessary. Results: When compared with the women, the men of both groups presented superior results for all BMD values analyzed. In addition, GA had higher BMD of arms and spine when compared to the CG, both for males (p = 0.016 and p = 0.001, respectively) and females (p = 0.0001 and p = 0.011, respectively). Conclusions: The results of this study demonstrate that young male adults, athletes and non-athletes, present higher levels of BMD than their peers of the opposite sex. In addition, the results suggest that when undertaken for competitive purposes and with a weekly training volume of 12 hours or more, swimming may be beneficial for the bone development of young athletes when compared to non-athlete controls. Level of evidence III; Retrospective comparative study.

RESUMO Introdução: Os efeitos osteogênicos gerados pelas diferentes modalidades esportivas são alvo de um crescente número de investigações. A prática regular de atividades físicas é uma das principais recomendações para a estimulação da densidade mineral óssea (DMO). Entretanto, as evidências têm demonstrado que nem todas as atividades físicas promovem efeitos semelhantes. Nesse contexto, os efeitos osteogênicos da natação precisam ser esclarecidos. Objetivo: Verificar e comparar os níveis de DMO, total e regional, entre atletas de natação de ambos os sexos e universitários não atletas. Métodos: A amostra, composta por 60 participantes de ambos os sexos, foi dividida em dois grupos: 30 atletas de natação (GA): 15 homens (22,2±3,92 anos; 73,61±16,55 Kg; 1,76±0,08 m) e 15 mulheres (21,91±2,21 anos; 53,15±8,36 Kg; 1,64±0,06 m) e um grupo controle (GC): 30 universitários não atletas: 15 homens (20,73±1,27anos; 74,4±5,54 Kg; 1,74±0,04 m) e 15 mulheres (19,93±2,05 anos; 59,72±1,33 Kg; 1,63±0,004 m). As DMO (total, dos braços, pernas, pelve e coluna) foram medidas com utilização da absorciometria radiológica de dupla energia (DXA). Os resultados foram comparados com auxílio da ANOVA One-Way utilizando, quando necessário, o teste post hoc de Scheffé. Resultados: Quando comparados com as mulheres, os homens dos dois grupos apresentaram resultados superiores para todas as DMO analisadas. Além disso, o GA apresentou maiores DMO de braços e de coluna quando comparado ao GC, tanto para homens (p=0,016 e p=0,001, respectivamente) quanto para mulheres (p=0,0001 e p=0,011, respectivamente). Conclusão: Os resultados do presente estudo demonstram que os jovens adultos do sexo masculino, atletas e não atletas, apresentam maiores níveis de DMO que seus pares do sexo oposto. Além disso, os resultados sugerem que, quando praticado com objetivo competitivo e com volume de treinamento semanal igual ou superior a 12 horas, a natação pode ser benéfica para o desenvolvimento ósseo de jovens atletas, quando comparado com o grupo controle não atletas. Nível de evidência III; Estudo retrospectivo comparativo.

RESUMEN Introducción: Los efectos osteogénicos generados por las diferentes modalidades deportivas son objeto de un creciente número de investigaciones. La práctica regular de actividades físicas es una de las principales recomendaciones para la estimulación de la densidad mineral ósea (DMO). Entretanto, las evidencias han demostrado que no todas las actividades físicas promueven efectos semejantes. En ese contexto, los efectos osteogénicos de la natación precisan ser esclarecidos. Objetivo: Verificar y comparar los niveles de DMO, total y regional, entre atletas de natación de ambos sexos y universitarios no atletas. Métodos: La muestra, compuesta por 60 participantes de ambos sexos, fue dividida en dos grupos: 30 atletas de natación (GA): 15 hombres (22,2±3,92 años; 73,61±16,55 Kg; 1,76±0,08 m) y 15 mujeres (21,91±2,21 años; 53,15±8,36 Kg; 1,64±0,06 m) y un grupo control (GC): 30 universitarios no atletas: 15 hombres (20,73±1,27 años; 74,4±5,54 Kg; 1,74±0,04 m) y 15 mujeres (19,93±2,05 años; 59,72±1,33 Kg; 1,63±0,004 m). Las DMO (total, de los brazos, piernas, pelvis y columna) fueron medidas con el uso de la absorciometría radiológica de doble energía (DXA). Los resultados fueron comparados con auxilio de ANOVA One-Way utilizando, cuando fuera necesario, el test post hoc de Scheffé. Resultados: Cuando comparados con las mujeres, los hombres de los dos grupos presentaron resultados superiores para todas las DMO analizadas. Además, el GA presentó mayores DMO de brazos y de columna cuando comparado al GC, tanto para hombres (p=0,016 e p=0,001, respectivamente) como para mujeres (p=0,0001 y p=0,011, respectivamente). Conclusión: Los resultados del presente estudio demuestran que los jóvenes adultos del sexo masculino, atletas y no atletas, presentan mayores niveles de DMO que sus pares del sexo opuesto. Además, los resultados sugieren que, cuando practicado con objetivo competitivo y con volumen de entrenamiento semanal igual o superior a 12 horas, la natación puede ser benéfica para el desarrollo óseo de jóvenes atletas, cuando comparado con el grupo control no atletas. Nivel de evidencia III; Estudio retrospectivo comparativo.

The stretch-shortening cycle efficiency is dependent on the maturational stage / A eficiência do ciclo alongamento-encurtamento é dependente do estágio maturacional

Abstract Maturation interferes with physiological and mechanical aspects of muscle contraction. The aim of the present study was to compare the efficiency of the stretch-shortening cycle (SSC) between different maturation stages. One hundred forty six young people, with 72 boys and 74 girls, were recruited to participate in the study. Sexual maturation was measured and the group was stratified into adolescents (> 3 auto-tanner) and children (<2 auto-tanner). Squat jump (SJ) and countermovement jump (CMJ) performance were measured to measure reactive force (RF) capacity, eccentric utilization ratio (EUR) and pre-stretch augmentation (PSAP). The children did not present statistical difference between SJ and CMJ (t(55)= -1.93; ∆ = -0.61; 95% CI = -1.24 to -0.02; p = 0.058), while the adolescents presented higher performance of CMJ (t(89)= -12.28; ∆ = -2.44; 95% CI = -2.84 to -2.05; p <0.001). In addition, adolescents had higher RF performance (t(144)= 5.18; p <0.0001; 95% CI = 2.53 to 1.13), PSAP (t(144)= 4.38; p <0.0001; 95% CI = 14.00 to 5.29) and EUR (t(144)= 4.38; p <0.0001; 95% CI = 0.14 to 0.05). We conclude that more mature young people have better SSC utilization.

Resumo Maturação interfere em aspectos fisiológicos e mecânicos da contração muscular. O objetivo do estudo foi comparar a eficiência do ciclo alongamento-encurtamento (SSC) em diferentes estágios maturacionais. Cento e quarenta e seis jovens, sendo 72 meninos e 74 meninas, foram recrutados para participar do estudo. Maturação sexual foi mensurada e o grupo foi estratificado em adolescentes (≥ 3 e crianças (< estágio 2). Salto estático (SJ) e o salto contramovimento (CMJ) foram utilizados para mensurar a força reativa (RF), razão de utilização da excêntrica (EUR) e aumento do pré-estiramento (PSAP). As crianças não apresentaram diferença significante entre SJ e CMJ (t(55)= -1.93; ∆ = -0.61; 95% CI = -1.24 to -0.02; p = 0.058), Enquanto que os adolescentes apresentaram maior desempenho de CMJ (t(89)= -12.28; ∆ = -2.44; 95% CI = -2.84 to -2.05; p <0.001). Em adição, adolescentes apresentaram maior RF (t(144)= 5.18; p <0.0001; 95% CI = 2.53 to 1.13), PSAP (t(144)= 4.38; p <0.0001; 95% CI = 14.00 to 5.29) e EUR (t(144)= 4.38; p <0.0001; 95% CI = 0.14 to 0.05). Nós concluímos que jovens com mais maturados apresentam maior capacidade de utilização do SSC.

Analysis of the small-sided games in volleyball: an ecological approach / Análise dos pequenos jogos no voleibol: uma abordagem ecológica

Abstract The aim of the present study was to compare the tactical and technical behavior of beginner players in volleyball side-out between four distinct situations of reduced games with different area/player ratios: 4.5 m2 (3.0 m x 3.0 m), 8.0 m2 (4.0 m x 4.0 m), 10.58 m2 (4.6 m x 4.6 m), and 13.52 m2 (5.2 m x 5.2 m). We analyzed 76 games played by 16 players with a mean age of 12.2 ± 0.5 years and experience of 1.2 ± 0.8 years of practice. Tactical and technical behavior was analyzed using an adaptation of the Game Performance Analysis Instrument (GPAI). The analysis was conducted for passing, setting and attacking according to the components related to technical adjustment, technical efficiency and decision-making. The results showed that players presented higher technical and tactical indexes in the passing and setting skills in 4.6 m x 4.6 m and 5.2 m x 5.2 m situations. Also, in the 3.0 m x 3.0 m situation higher technical indexes were found for the attacking. No differences were found in the tactical behavior of attacking for tested situations. We conclude that the environmental constraints imposed by the small-sided games imply distinct technical and technical behaviors. Thus, the pedagogical strategy of using small-sided games for the teaching of volleyball for beginner players must be associated with the intended objectives for each basic volleyball skills.

Resumo O objetivo do presente estudo foi comparar o comportamento tático e técnico de jogadores iniciantes no voleibol no side-out de acordo com quatro situações distintas de jogos reduzidos com diferentes relações área/jogador: 4,5 m2 (3,0 m x 3,0 m), 8,0 m2 (4,0 m x 4,0 m), 10,58 m2 (4,6 m x 4,6 m) e 13,52 m2 (5,2 m x 5,2 m). Foram analisados ​​76 jogos disputados por 16 jogadores com média de idade de 12,2 ± 0,5 anos e experiência de 1,2 ± 0,8 anos de prática. O comportamento tático e técnico foi analisado por meio de uma adaptação do Game Performance Analysis Instrument. A análise foi realizada para a recepção, o levantamento e o ataque de acordo com os componentes relacionados ao ajuste técnico, eficiência técnica e a tomada de decisão. Os resultados mostraram que os jogadores apresentaram índices táticos e técnicos superiores nas habilidades de recepção e levantamento nas situações de 4,6 m x 4,6 m e 5,2 m x 5,2 m. Além disso, na situação de 3,0 m x 3,0 m foram encontrados índices técnicos mais elevados para o ataque. Não foram encontradas diferenças no comportamento tático do ataque para as situações analisadas. Concluímos que as restrições ambientais, impostas pelos pequenos jogos, implicam em comportamentos táticos e técnicos distintos. Assim, a estratégia pedagógica de utilização de pequenos jogos para o ensino do voleibol para jogadores iniciantes deve estar associada aos objetivos pretendidos para cada uma das habilidades básicas do voleibol.

Analysis of associations and factors predicting the effectiveness of finalization in the female handball of high level / Análise das associações e dos fatores preditivos da eficácia do lançamento no handebol feminino de alto nível

ABSTRACT The study aimed to analyze the association between the position of the attacker, the place of the finish and the direction of the finalization with the effectiveness of the finalization, as well as the predictive factors of this. A total of 6146 attack actions of 66 matches were analyzed by the 24 teams participating in the 2015 Women's World Handball Championship. For the association between the variables studied, we used the Chi-Square test and for predictive analysis of the data, we used the multinomial regression. The significance level of p≤0.05 was adopted and the software SPSS version 20.0 for Windows was used. The results showed an association between the finalization effect and the attacker's position (χ2 = 107.39, p = 0.0001, ɸ = 0.13), association between the finishing effect and the finishing direction (χ2 = 715, (Χ2 = 587.25, p = 0.0001, ɸ = 0.34), and that the predictive factors of the finalization effect was statistically significant (χ2 = 854.666; p <0.0001). Thus, from the results, it is possible to concluded that the effect of the finalization and the direction of the finalization, suggesting that the position of the player does not influence in obtaining the goal.

RESUMO O estudo objetivou analisar a associação entre a posição da atacante, o local do lançamento e a direção do lançamento com o efeito do lançamento, bem como os fatores preditivos deste. Foram analisadas 6146 ações de ataque de 66 jogos realizados pelas 24 equipes participantes do Campeonato Mundial de Handebol Feminino de 2015. Para a associação entre as variáveis estudadas recorreu-se ao teste do Qui-Quadrado e para análise preditiva utilizou-se à regressão logística multinomial. Adotou-se o valor de significância de p≤0,05 e utilizou-se o software SPSS versão 20.0 para Windows. Os resultados apontaram associação entre o efeito do lançamento e a posição da atacante (��2= 107,39; p=0,0001; ɸ=0,13), entre o efeito do lançamento e o local do lançamento (��2= 715,01; p=0,0001; ɸ=0,34), entre o efeito do lançamento e a direção do lançamento (��2= 587,25; p=0,0001; ɸ=0,34) e que o local do lançamento e a direção do lançamento foram fatores preditivos do efeito do lançamento (��2=854,666; p<0,0001). Assim, a partir dos resultados, pode-se concluir que o efeito do lançamento é predito pelo local do lançamento e pela direção do lançamento, sugerindo que a posição da jogadora não influencia na obtenção do gol.

The relationship between relative age effects and sex, age categories and playing positions in Brazilian National Handball Teams

Abstract Aims: This study investigated the existence of Relative Age Effect (RAE) in the selection process of male and female athletes in the Brazilian national handball teams according to age categories (U-18, U-21, and senior) and playing position (wings, backs, pivots, and goalkeepers). Methods: In order to determine RAE, athletes were divided based on their months of birth; quarters Q1 (January-March), Q2 (April-June), Q3 (July-September), and Q4 (October-December). Data were collected from the official Brazilian Handball Confederation (CBHb) website and included the athletes that participated in training and/or competitions composing the Brazilian national teams from 2014 to 2018. To determine the RAE on playing positions, age categories of male and female groups were pooled. Chi-squared tests were performed to investigate the RAE. Results: An over-representation of players born in Q1 and Q2 in the U-18, U-20, and senior categories of male teams and the U-20, and senior female teams were found. In the male teams, as the age category increased, RAE decreased, but still existed. Such distribution was reversed in the female athletes, with a higher RAE magnitude in the senior category as compared to U-18 and U-21. Additionally, it seems that RAE is dependent on the playing position only for male athletes (wings and backs) whereas RAE was found for all playing positions in female athletes. Conclusion: Overall, RAE was found in Brazilian national handball teams, but its magnitude and form of manifestation seem to be influenced by sex, category, and playing position.

Mudança no foco de atenção ao longo da prática de uma habilidade motora / Change in attentional focus through the practice of a motor skill

Este experimento investigou os efeitos da mudança do foco de atenção durante o processo de aprendizagem de uma habilidade motora. Quatro grupos experimentais (foco interno, foco externo, foco interno-externo e foco externo-interno) e um grupo controle praticaram uma tarefa de arremesso de dardo. Durante a fase de aquisição, dois grupos experimentais tiveram uma forma de focalizar a atenção (foco interno ou externo) e os outros dois grupos tiveram o foco de atenção mudado na metade da prática (foco interno-externo ou externo-interno). Os resultados do teste de retenção mostraram que o foco interno-externo resultou em um desempenho mais consistente. Esses resultados sugerem a existência de relação entre os efeitos do foco de atenção e o nível de aprendizagem.

This experiment investigated the effects of changing the attentional focus during the process of learning a motor skill. Four experimental groups (internal, external, internal-external and external-internal focus) and one control group practiced a dart throwing task. During the acquisition phase, two experimental groups had only one focusing attention (internal or external focus), and other two experimental groups had focus of attention changed half way through the amount of practice (internal-external or external-internal focus). The results of the retention test showed that the internal-external focus resulted in a more consistent performance. These results suggest the existence of a relationship between the effects of attentional focus and level of learning.

Comparação do tempo de reação entre atletas de Basquetebol, Ginástica Artística e não atletas / Comparison of reaction time between Basketball players, Artistic Gymnasts and non-athletes / Comparación de tiempo de reacción entre los atletas de Baloncesto, Gimnasia Artística y no atletas

O propósito deste estudo foi comparar o tempo de reação entre atletas de Basquetebol (grupo Basquetebol), Ginástica Artística (grupo Ginástica) e não atletas (grupo controle). Os indivíduos foram avaliados no tempo de reação simples e de escolha através do instrumento MULTPSY 821 e Sistema de Testes de Viena, respectivamente. Os resultados indicaram somente diferença significativa entre os grupos na medida de tempo de reação simples. O grupo controle apresentou maior tempo de reação comparado aos outros grupos. Esses achados indicam que a prática de Basquetebol e Ginástica Artística pode melhorar o tempo de reação simples, que é uma capacidade perceptiva necessária em atividades diárias.

The purpose of this study was to compare the reaction time between Basketball players (group Basketball), Artistic Gymnastics (Gymnastics group) and non-athletes (control group). The subjects were evaluated in simple and choice reaction time through the instrument MULTPSY 821 and Viena Test System, respectively. The results showed only significant difference between groups in the measure of simple reaction time. The control group showed higher reaction time compared to other groups. These findings indicate that the practice of Basketball and Artistic Gymnastics can improve the reaction time which is a perceptual ability needed in daily living activities.

El propósito de este estudio fue comparar el tiempo de reacción entre los atletas de Baloncesto (grupo Baloncesto), atletas de la Gimnasia Artística (grupo Gimnasia) y los no deportistas (grupo control). Los sujetos fueron evaluados en el tiempo de reacción simple y la elección a través del instrumento MULTPSY 821 y sistema de análisis de Viena, respectivamente. Los resultados mostraron diferencias significativas sólo entre los grupos en la medida del tiempo de reacción simple. El grupo control presentó mayor tiempo de reacción en comparación con otros grupos. Estos resultados indican que la práctica del Baloncesto y la Gimnasia pueden mejorar el tiempo de reacción que es una capacidad perceptiva necesaria en las actividades diarias.