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.

Physical Exercise Decreases Endoplasmic Reticulum Stress in Central and Peripheral Tissues of Rodents: A Systematic Review.

Endoplasmic reticulum stress (ER stress) affects many tissues and contributes to the development and severity of chronic diseases. In contrast, regular physical exercise (PE) has been considered a powerful tool to prevent and control several chronic diseases. The present systematic review aimed to evaluate the impact of different PE protocols on ER stress markers in central and peripheral tissues in rodents. The eligibility criteria were based on PICOS (population: rodents; intervention: physical exercise/physical training; control: animals that did not undergo training; outcomes: endoplasmic reticulum stress; studies: experimental). The PubMed/Medline, Science Direct, Scopus, and Scielo databases were analyzed systematically. Quality assessment was performed using SYRCLE's risk of bias tool for animal studies. The results were qualitatively synthesized. Initially, we obtained a total of 2.490 articles. After excluding duplicates, 30 studies were considered eligible. Sixteen studies were excluded for not meeting the eligibility criteria. Therefore, 14 articles were included. The PE protocol showed decreased levels/expression of markers of ER stress in the central and peripheral tissues of rodents. PE can decrease ER stress by reducing cellular stress in the cardiac, brain, and skeletal muscle tissues in rodents. However, robust PE protocols must be considered, including frequency, duration, and intensity, to optimize the PE benefits of counteracting ER stress and its associated conditions.

Fatores associados aos comportamentos ativo e sedentário em adolescentes brasileiros: uma análise de redes / Factors associated with active and sedentary behaviors in Brazilian adolescents: a network analysis

O presente estudo verificou a associação entre variáveis sociodemográficas, características da esco-la, nível de atividade física (AF) e comportamento sedentário (CS) em adolescentes brasileiros. A amostra foi composta por 71.903 adolescentes entre 13 e 16 anos (52,8% meninas), matriculados no último ano do ensino fundamental, em escolas públicas e privadas do Brasil, participantes da terceira edição da Pesquisa Nacional da Saúde do Escolar (PeNSE). As informações foram recolhidas através de questionário. O tempo de AF na aula de Educação Física e extra aula de Educação Física, o tempo em deslocamento ativo e o tempo em CS foram associados às variáveis sociodemográficas (tipo de município, local da escola, escolaridade da mãe, percepção de insegurança, idade e sexo) e características da escola (tipo de escola e quadra disponível para uso). Utilizou-se a análise de rede. Quanto ao comportamento ativo, a topologia de rede mostrou que os meninos são mais ativos do que as meninas, principalmente na AF extra aula de Educação Física. Além disso, os resultados revelaram um maior tempo de AF na aula de Educação Física para os meninos, estudantes cujas mães apresentavam maior escolaridade, matriculados em escolas privadas e com quadra disponível para uso. Os estudantes matriculados em escolas públicas apresentaram maior tempo de AF em deslocamento ativo. Quanto ao CS, jovens do contexto urbano apresentaram maior exposição quando comparados aos pares do contexto rural. Conclui-se que as características sociodemográficas e da escola estão relacionadas com os comportamentos dos adolescentes brasileiros em todos os domínios da AF e no CS

The present study aimed to verify the association of sociodemographic correlates and school characteristics with levels of physical activity (PA) and sedentary behavior (SB) of Brazilian adolescents. The sample consisted of 71,903 adolescents between 13 and 16 years old (52.8% girls), enrolled in the last year in public and pri-vate elementary schools of Brazil, participants of the third edition of the National Survey of School Health (PeNSE). The time of PA in Physical Education class and extra Physical Education class, time in active commuting and time in SB were related to sociodemographic variables (type of municipality, place where the school is located, mother's schooling, perception of insecurity, age and gender) and school characteristics (type of school, block available for use). Data were analyzed using network analysis. The network topology showed that boys are more active than girls, especially in extra Physical Education`s PA. In addition, boys, students whose mothers have higher education, enrolled in private schools, which have a court available for use, have a positive association with longer time spent in PA in physical education classes. Students enrolled in public schools had a positive association with time spent in active commuting PA. As for SB, young people from the urban context are more exposed to SB than rural context. It was concluded that sociodemographic correlates and characteristics of the school were associated with all domains of the physical activity and sedentary behavior

Comparison of affective responses during school physical education classes with different recovery times / Comparação das respostas afetivas durante aulas de educação física escolar com diferentes tempos de recuperação

ABSTRACT This study aimed to verify the effect of exercise recovery time on the affective responses during a circuit training in physical education classes. Forty-six apparently healthy young adolescents (twenty-one girls) (12.85 ± 0.94 years; 49.7 ± 8.93 kg; 1.59 ± 0.08 cm; 19.51 ± 3.28 kg/m2) participated in this study. Were submitted participants for two physical education classes, based on circuited model of the same intensity, but with different recovery times (2 min and 1 min). The study was carried out in two phases: baseline and intervention. Affect, Arousal, and Ratings of Perceived Exertion data were analyzed using paired t-tests, considering a significance level of p < 0.05. The class with longer rest time (2 min) provided greater affection (t(45) = 3.586; p < 0,001) and less perceived effort (t(45) = 2.295; p = 0,026). The intensity manipulation strategy was effective in providing different affective responses, in which classes perceived as more intense, resulting in the decline of affect.

RESUMO O objetivo do estudo foi verificar o efeito do tempo de recuperação do exercício nas respostas afetivas durante um treinamento em circuito nas aulas de educação física. Quarenta e seis jovens adolescentes aparentemente saudáveis (vinte e uma meninas), com (12.85 ± 0.94 anos; 49.7 ± 8.93 kg; 1.59 ± 0.08 cm; 19.51 ± 3.28 kg/m2), participaram do estudo. Os participantes foram submetidos a duas aulas de educação física escolar, baseados em modelo de circuitos de mesma intensidade, porém com tempos de recuperação diferentes (2 min e 1 min). O estudo foi realizado em duas fases: base e intervenção. Os dados de Afeto, Ativação e Percepção Subjetiva do Esforço, foram analisados através de testes t pareados, considerando um nível de significância de p < 0,05. A aula com maior tempo de descanso (2 min) proporcionou maior afeto (t(45) = 3.586; p < 0,001) e menor esforço percebido (t(45) = 2.295; p = 0,026). A estratégia de manipulação da intensidade foi efetiva para proporcionar respostas afetivas diferentes, em que a aula percebida como mais intensa resultou no declínio do afeto.

Plyometric training increases gross motor coordination and associated components of physical fitness in children.

There is only limited evidence to suggest that training during childhood produces greater adaptations than at other ages. The aim of this study was to examine the effects of plyometric training (12 weeks, twice/week, 20 min/day) on physical fitness (PF) and gross motor coordination (GMC) in schoolboys aged 7-9 years. A total of 116 boys were assigned to two groups: plyometric training group (PT,n = 73) and control group (CG,n = 43). The CG maintained their normal daily activities. The PT consisted of twice-weekly exercises on nonconsecutive days for twelve weeks under monitored and controlled conditions. PF (handgrip strength, standing long jump (SLJ), curl-ups, sit and reach, square-test, running speed, and 1 mile run test), GMC, Korper-koordinations-test fur Kinder (KTK), and body mass index (BMI) were assessed. The main results through a 2 × 2 (time × groups) repeated measures analysis variance demonstrated a significant time effect that improves PF and GMC according to the direction of the measure. A group effect was observed only in the abdominal strength test (CG = 12.06% and PT = 17.04%) and moving sideways (CG = 11.1% and PT = 12.4%) showing that independent of the group there was an improvement. A significant interaction effect (time × groups) was observed in the flexibility test (CG = -2.7% and PT = 3.5%) and STJ (CG = 3.1% and PT = 18.5%), as well as jumping sideways (CG = 16.3% and PT = 17.4%) and overall GMC score (CG = 9.8% and PT = 15.9%), showing that gains in these variables were greater in the PT group. The results suggest that 12 weeks of PT improve components of gross motor coordination and health-related physical fitness in children.

Effect of school type and family income on motor competence changes in pre-school children: a repeated cross sectional study / Efeito do tipo de escola e renda familiar nas mudanças da competência motora em crianças pré-escolares: um estudo transversal repetido

ABSTRACT Motor competence (MC) is an attribute associated with positive health behaviors; contextual factors, seems to play a important role for MC of children. The purpose of this study was to compare the MC of preschool children in two different years and to identify the effect of contextual factors (school type and family income). Two representative samples of children (3 to 5 years old) from Recife were assessed in two time periods: 2010 (n= 282 children, 151 boys) and 2012 (n=270 children, 148 boys). MC was assessed using the Test of Gross Motor Development - 2. Data analysis used the Anova Two-Way and the Ancova tests adjusted by type of school (public and private) and family income, a p <0.05 was used. Locomotor skills, object control and overall motor quotient were superior for the children analyzed in 2010. Furthermore, the school type and income increased the effect size in the differences in object control skills and the general motor quotient. We can conclude that there was a decrease in MC of the preschool population after two years and that the contextual variables type of school and family income are important for the development of MC.

RESUMO A competência motora (CM) é um atributo associado a comportamentos positivos de saúde; fatores contextuais, parecem desempenhar um papel importante para CM de crianças. O objetivo deste estudo foi comparar a CM de pré-escolares em dois diferentes anos e identificar o efeito de fatores contextuais (tipo de escola e renda). Duas amostras representativas de crianças (3 a 5 anos) da cidade do Recife foram avaliadas em dois momentos: no ano de 2010 (282 crianças; 151 meninos) e 2012 (270 crianças; 148 meninos). A avaliação da CM foi realizada com o Test of Gross Motor Development - 2. A análise dos dados utilizou a Anova Two-Way e a Ancova ajustada por tipo de escola (pública e particular) e renda familiar, foi adotado um p<0.05. Foi identificada uma superioridade nas habilidades locomotoras, de controle de objetos e no quociente motor geral para as crianças analisadas em 2010 e o tipo de escola e renda aumentaram o tamanho do efeito das diferenças nas habilidades de controle de objetos e no quociente motor geral. Podemos concluir que houve uma diminuição na CM da população pré-escolar após dois anos e que as variáveis contextuais tipo de escola e renda são importantes para o desenvolvimento da CM.

Effects of maturation as a covariate of sex difference on motor competence in adolescents / Efeito da maturação como covariável da diferença entre sexos na competência motora em adolescentes

ABSTRACT The aim of this study was to evaluate differences between sexes in motor competence (MC) by product- and process-oriented assessments, and examine the effect of maturation as a covariate influencing the MC of boys and girls. The sample comprised 50 adolescents (28 boys), aged 11-17 years (14.02 ± 2.49), from two public schools. The MC was evaluated in three skills (standing long jump, hop and throw) by process- (developmental sequences for body components) and product-oriented assessments (distance, time and speed, respectively). Maturation was evaluated with the peak height velocity (PHV). Sex differences were evaluated using ANOVA and, subsequently, ANCOVA, considering the PHV as a covariate. Boys had better MC in all the skills for product-oriented assessment, and most of body components for process-oriented assessment. After using the PHV as a covariate, the magnitude of differences between sexes increased in most of motor skills for both types of assessments, favoring boys. Considering the effect of maturation on the difference between the sexes in the MC, we emphasize the need to observe the maturation while studying the MC during adolescence.

RESUMO O objetivo do presente estudo foi verificar a diferença entre sexos na competência motora (CM) avaliada por produto e processo do movimento, e analisar o efeito da maturação como uma covariável influenciando a CM de rapazes e moças. A amostra foi composta por 50 adolescentes (28 rapazes), com idade entre 11 e 17 anos (14,02±2,49), provenientes de duas escolas públicas. A CM foi avaliada em três habilidades (salto horizontal, saltito e arremesso sobre o ombro), por meio de medidas orientadas ao processo (sequências desenvolvimentais por componentes corporais) e ao produto do movimento (distância, tempo e velocidade, respectivamente). A maturação foi avaliada com o pico de crescimento em estatura (PCE). Diferenças entre os sexos foram avaliadas com a ANOVA One-Way e, posteriormente, a ANCOVA, utilizando o PCE como covariável. Os rapazes tiveram melhor CM em todas as habilidades nas medidas de produto do movimento e na maioria dos componentes corporais, que mediram o processo do movimento. Após a utilização do PCE como covariável, a magnitude da diferença entre os sexos aumentou na maioria das habilidades motoras para ambos os tipos de medida, favorecendo os rapazes. Considerando o efeito da maturação sobre a diferença entre os sexos na CM, ressaltamos a necessidade de observar a maturação ao examinar a CM na adolescência.

Physical characteristics that predict involvement with the ball in recreational youth soccer.

This study examined the relative contribution of age, stage of puberty, anthropometric characteristics, health-related fitness, soccer-specific tests and match-related technical performance to variance in involvements with the ball during recreational 5-a-side small-sided (32 × 15 m) soccer matches. Using a cross-sectional design, 80 healthy male students (14.6 ± 0.5 years of age; range 13.6-15.4) who played soccer recreationally were randomly divided into 10 teams and played against each other. Measurements included height, body mass, pubertal status, health-related fitness (12-min walk/run test, standing long jump, 15-m sprint and sit-ups in 30 s), soccer-specific tests (kicking for speed, passing for accuracy and agility run with and without a ball), match-related technical performance (kicks, passes and dribbles) and involvements with the ball during matches. Forward multiple regression analysis revealed that cardiorespiratory fitness (12-min walk/run test) accounted for 36% of the variance in involvements with the ball. When agility with the ball (zigzag running) and power (standing long jump) were included among the predictors, the total explained variance increased to 62%. In conclusion, recreational adolescent players, regardless of their soccer-specific skills, may increase participation in soccer matches most through physical activities that promote improvement in cardiorespiratory fitness, muscle power and agility.

Participation in sports practice and motor competence in preschoolers / A participação na prática de esportes e competência motora em crianças pré-escolares / La participación en la práctica del deporte y la competencia motriz en niños en edad preescolar

Recent theoretical model suggests that motor competence during early childhood is related to one's current and future health status and that practicing sports seems to be playing a special role in creating such competence. This study aimed to compare performance in gross motor skills among preschoolers participating in regular sports practice (SP) and those not participating (NSP), including comparisons by gender. The study uses secondary data from a population-based study of performance regarding the locomotor and object control skills of preschoolers (3 to 5 years old). Preschoolers were assigned to groups SP or NSP, paired by age and sex according to skills: locomotor (n = 54; 30 boys) or object control (n = 37; 17 boys). Analysis of variance showed that the SP group outperformed the NSP one, and there were gender differences only within SP group. Starting to practice sports during early childhood helps to build motor competence and benefits both genders.

Modelo teórico recente sugere que competência motora na primeira infância está relacionada com o estado de saúde atual e futuro e práticas de esportes parecem ser especiais para tal competência. Este estudo comparou o desempenho motor grosso de pré-escolares participantes em práticas esportivas regulares (PE) com o daqueles não participantes nessas práticas (NPE), incluindo comparações entre gêneros. Dados do desempenho em habilidades locomotoras e de controle de objetos foram retirados de um estudo de base populacional com pré-escolares (3 a 5 anos); pré-escolares foram alocados em grupos PE e NPE, pareados por idade e gênero, para as habilidades locomotoras (n = 54; 30 meninos) ou controle de objetos (n = 37; 17 meninos). Análise de variância mostrou que o grupo PE foi melhor que o NPE; houve diferenças entre gêneros somente no grupo NPE. Práticas esportivas, já durante a primeira infância, contribuem para a competência motora, beneficiando ambos os gêneros.

Modelo teórico reciente sugiere que la competencia motriz en la primera infancia está relacionada con el estado de salud actual y futuro; las prácticas deportivas parecen ser especial para dicha competencia. Este estudio comparó el desempeño motor bruto de los niños en edad preescolar que participan en las prácticas deportivas regulares (PD) con los que no participan (NPD), incluyendo comparaciones de género. Se tomaron los datos de desempeño en habilidades locomotoras y control objeto de estudio basado en la población con los niños en edad preescolar (3-5 años); los niños se dividieron en grupos PD y NPD, emparejados por edad y género, según las habilidades locomotoras (n = 54, 30 hombres) o de control de objetos (n = 37, 17 varones). El análisis de varianza mostró que el grupo de PD fue mejor que NPD, hubo diferencias entre los géneros en el grupo NPD. Las prácticas deportivas desde la infancia, contribuyen a la competencia motriz, en beneficio de ambos géneros.

Precisão do conhecimento de resultados no processo adaptativo em crianças / Precision of knowledge of results in the adaptative process in children

O objetivo deste estudo foi analisar os efeitos da precisão de Conhecimento de Resultados (CR) na aquisição de uma habilidade motora. Quarenta e oito crianças com idade entre oito e 10 anos (♂ = 9,33 ± 0,70 anos e ♀= 9,16 ± 0,81 anos) praticaram uma tarefa de acertar um alvo sobre uma mesa, mediante o lançamento de discos metálicos. Foram formados três grupos experimentais de acordo com o nível de precisão do CR: pouco preciso (GPP), preciso (GP) e muito preciso (GMP), além do grupo controle (GC), sem CR. A medida de desempenho foi o erro absoluto (EA). Os resultados indicaram diferença estatística a favor do GMP em comparação aos demais grupos, indicando que a maior precisão do CR favoreceu a estabilização da estrutura e a adaptabilidade do sistema, numa tarefa com meta de precisão espacial, em crianças.

This study aimed to analyze the effects of Knowledge of Results (KR) precision on acquisition of a motor ability. Forty eight children aged between eight and 10 years old (♂ = 9.33 ± 0.70 years old; ♀ = 9.16 ± 0.81 years old) practiced a manipulative task of reaching a target on a table, by the thrown of metallic discs. Three experimental groups were formed according to the KR precision level: less precise group (LPG), precise group (PG) and very precise group (VPG), and also the control group (CG), without KR. The performance measure was the absolute error. The results indicated statistic differences in favor of VPG when compared to the other groups, indicating that higher KR precision benefited the system's stabilization and adaptability for task with accuracy goal, for children.

Desempenho em uma tarefa de timing coincidente e velocidade do estímulo: o uso de índices de acertos / Performance in a coincidence timing task and stimulus velocity: use of hit rates

O objetivo deste estudo foi investigar o número de acertos consecutivos em uma tarefa complexa de timing coincidente, que foram utilizados como índices de desempenho, e o efeito da velocidade do estímulo luminoso no alcance desses índices. Trinta adultos de ambos os sexos foram testados no equipamento de Timing Coincidente para Tarefas Complexas em três velocidades do estímulo luminoso: alta, moderada e baixa. Asanálises mostraram que dois índices de desempenho podem ser usados como critério da estabilização do desempenho: três e quatro acertos consecutivos na meta de coincidência. A análise descritiva parece sugerir que na condição de alta velocidade o índice de acertosconsecutivos talvez tivesse que ser mais rigoroso.

The aim of this study was to investigate the number of consecutive hits in a complex coincidence timing task, which were used as performance indices, and the effect of light stimulus velocity on reaching these indices. Thirty adults of both genders were tested using an apparatus of coincidence timing for complex tasks and three light stimulus velocities (high, moderate and low). Analysis showed that two performance indices can be used as criteria of performance stabilization: three and four consecutive hits in the coincidence goal. Descriptive analysis suggeststhat the index of consecutive hits should be more rigorous at high light stimulus velocity.