Genetic aspects of athletic performance: the African runners phenomenon.

The current dominance of African runners in long-distance running is an intriguing phenomenon that highlights the close relationship between genetics and physical performance. Many factors in the interesting interaction between genotype and phenotype (eg, high cardiorespiratory fitness, higher hemoglobin concentration, good metabolic efficiency, muscle fiber composition, enzyme profile, diet, altitude training, and psychological aspects) have been proposed in the attempt to explain the extraordinary success of these runners. Increasing evidence shows that genetics may be a determining factor in physical and athletic performance. But, could this also be true for African long-distance runners? Based on this question, this brief review proposed the role of genetic factors (mitochondrial deoxyribonucleic acid, the Y chromosome, and the angiotensin-converting enzyme and the alpha-actinin-3 genes) in the amazing athletic performance observed in African runners, especially the Kenyans and Ethiopians, despite their environmental constraints.

Descriptive epidemiology of injuries in a Brazilian premier league soccer team.

Soccer, which has a large number of participants, has a high injury incidence that causes both financial and time burdens. Therefore, knowledge about the epidemiology of soccer injuries could allow sports-medicine professionals, such as physicians and physiotherapists, to direct their work in specific preventive programs. Thus, our aim was to conduct an epidemiological survey of injuries sustained by professional soccer players from the same team who participated in the Brazilian championship premier league in 2009. To this end, we evaluated retrospectively player medical records from the team, which included name, date of birth, position, date of injury, mechanism of injury, and type of injury. In the period of study, 95 injuries were recorded: 42 (44.2%) were recorded during matches, and 53 (55.8%) during the training period. Injuries occurred more frequently in midfielders and strikers. All injuries happened in the lower limb, most of the injuries were muscular, and most occurred as the result of collisions with other athletes. In summary, this study demonstrates that there is a need for greater safety awareness in the training environment.

Heart rate response during a simulated Olympic boxing match is predominantly above ventilatory threshold 2: a cross sectional study.

The present study aimed to describe heart rate (HR) responses during a simulated Olympic boxing match and examine physiological parameters of boxing athletes. Ten highly trained Olympic boxing athletes (six men and four women) performed a maximal graded exercise test on a motorized treadmill to determine maximal oxygen uptake (52.2 mL · kg(-1) · min(-1) ± 7.2 mL · kg(-1) · min(-1)) and ventilatory thresholds 1 and 2. Ventilatory thresholds 1 and 2 were used to classify the intensity of exercise based on respective HR during a boxing match. In addition, oxygen uptake (V̇O2) was estimated during the match based on the HR response and the HR-V̇O2 relationship obtained from a maximal graded exercise test for each participant. On a separate day, participants performed a boxing match lasting three rounds, 2 minutes each, with a 1-minute recovery period between each round, during which HR was measured. In this context, HR and V̇O2 were above ventilatory threshold 2 during 219.8 seconds ± 67.4 seconds. There was an increase in HR and V̇O2 as a function of round (round 3 < round 2 < round 1, P < 0.0001). These findings may direct individual training programs for boxing practitioners and other athletes.

Comportamento da força em resposta ao alongamento e encurtamento muscular / Force behavior in response to muscle stretch and shortening

Alguns fenômenos relacionados à produção de força na fibra muscular não podem ser perfeitamente explicados pela teoria das pontes cruzadas; dentre eles, podemos citar o comportamento da força durante e após mudanças de comprimento muscular. Investigando a força durante estas mudanças, notou-se que o aumento e a diminuição da mesma durante o alongamento e encurtamento têm algumas características em comum com relação à forma do traçado da força: ambos apresentam duas fases (I e II), com duas mudanças de inclinação (P1 e P2). Apesar dessas similaridades, existem particularidades: quando diferentes velocidades são aplicadas, os comportamentos de P1 e P2 durante alogamento diferem ligeiramente dos seus homólogos durante o encurtamento. Distintos mecanismos moleculares tentam explicar essas particularidades: durante o alongamento P1 ocorre devido à reversão do curso de alavancagem das pontes cruzadas, ao passo que durante o encurtamento, as mesmas seguem seu curso normal. Em ambas as condições, P2 está relacionado ao ponto onde as pontes cruzadas se destacam; mas como este ponto ocorre em diferentes sentidos, resulta em diferentes estados moleculares finais. Ademais, P1 e P2 têm sido usados para se analisar o comportamento da força durante as mudanças de comprimento. Existem três mecanismos aceitos para explicar o ganho de força durante o alongamento 1) um aumento no número de pontes cruzadas; 2) um aumento na força gerada por cada ponte cruzada e 3) pontes cruzadas operando em estado de pré-curso-de-alavancagem. Já com relação à diminuição da força acredita-se que há uma perda da força média produzida por cada ponte cruzada, quando estas são “empurradas” para um estado molecular de menor tensão...

Some phenomena related to force production in muscle fibers cannot be fully explained by the crossbridge theory; among them we can cite the force behaviour during and after length changes. Investigating force during these changes, it was noted that the increase and decrease in force during stretchand shortening have some characteristics in common with respect to their force trace: both have twophases (I and II), with two changes in slope (P1 and P2). Despite these similarities, there are particularities: when different velocities are applied, P1 and P2 behaviours during stretch differ slightly from their counterpart during shortening. Distinct molecular mechanisms try to explain these particularities: during stretch, P1 occurs due to a reversal of powerstroke, where as during shortening, crossbridges follow the normal powerstroke course. In both conditions, P2 is related to the point where the cross-bridges detach; but as it happens in different directions, it results in different final molecular states. Furthermore, P1 e P2 have been used for force behaviour analyses during length changes. There are three accepted mechanisms to explain force enhancement during stretch: 1) an increase in the number of crossbridges, 2) an increase in force generated per crossbridge and 3) crossbridges operating in prepowerstroke. On the other hand, concerning force depression, it is believed there is a loss in the force produced per crossbridge, while they are "pushed" to a molecular state of lower strain...

Desempenho de basquetebolistas no salto vertical: comparação em diferentes momentos da partida / Basketball player's performance in vertical jump: a comparison at different times of the match

Introdução: O basquetebol é uma modalidade que se caracteriza pelo predomínio do metabolismo anaeróbio no fornecimento de energia com destaque para potência na realização dos diferentes fundamentos, principalmente na habilidade do salto. Com ações intermitentes no jogo, a produção de fadiga e a queda no desempenho dos atletas é um fator a ser investigado. Objetivo: o objetivo do estudo foi analisar e comparar saltos verticais de atletas de basquetebol, em diferentes quartos de jogo e posições, em duas partidas. Método: Participaram 11 atletas homens (idade de 22,8±3,7 anos, massa corporal de 94,15±13,9 kg, estatura de 196±9,1 cm) em diferentes posições e a avaliação da força explosiva de membros inferiores foi realizada com a técnica de Counter Movement Jump com auxílio dos braços. Os jogadores foram avaliados no início da partida e ao final dos quartos de jogo. Para análise dos dados utilizou-se média e desvio-padrão, teste de Kruskal-Wallis para normalidade, T de Student para dados pareados, na comparação entre as posições. Resultados: Os principais resultados dos valores de salto apontam para a proximidade quantos aos dados iniciais durante todos os quartos de jogo, nas duas partidas avaliadas e, em relação às posições do jogo e o tempo de participação, os armadores se destacam pelas diferenças significativas (p<0,05) avaliadas ao final do segundo e terceiro quarto. Conclusão: Os resultados assemelham-se a achados de outros autores, levando a crer que a fadiga de membros inferiores no salto não ocorre devido à relação com ações fisiológicas e da quantidade de saltos durante as partidas.

Introduction: Basketball is a sport that is characterized by the predominance of anaerobic metabolism in providing energy with the importance of power on the different fundamentals, especially in the ability of jump. With intermittent actions in the game, the production of fatigue and decline in athletes? performance is a factor to be investigated. Objective: The objective of the study was to analyze vertical jumps of basketball athletes, playing in different quarters and positions, in two matches. Methods: Study participants were 11 male athletes (age 22.8 ± 3.7 years, body mass 94.15 ± 13.9 kg, height of 196 ± 9.1 cm) in different positions and evaluation of explosive strength of lower limbs was performed with the technique of Counter Movement Jump with the help of arms. The players were evaluated at the beginning of the match and at the end of all quarters. For data analysis we used mean and standard deviation, the Kruskal-Wallis test for normality, Studen' s T for paired data, comparing the positions. Results: The main results of the jumps indicates to the homogeneity of the initial data for all quarters of the game in both matches and in relation to the playing time and participation, the guards shown significant differences (p <0 , 05) at the jumps evaluated at the second and third quarter, of game 2 and 1, respectively. Conclusion: The results are in accordance with findings of other studies, implying that the lack of fatigue in lower limbs in the act of jumping could be linked to the physiological responses and the number of jumps during the matches.

Periodização do treinamento de força: uma revisão crítica / Periodized strength training: a critical review

Originária da Alemanha e da antiga União das Repúblicas Socialistas Soviéticas (URSS), a teoria da periodização do treinamento se desenvolveu em meados do século XX, no chamado período científi co, baseada na teoria da Síndrome Geral da Adaptação (SGA). A literatura científi ca pertinente ao treinamento de força entende a periodização como a variação sistemática da intensidade e do volume com a fi nalidade de se desenvolver de forma efi ciente uma ou mais capacidades físicas. O presente trabalho teve por objetivo analisar o efeito da periodização sobre o treinamento de força com relação às suas adaptações específi cas e comparar os modelos mais recorrentes (fi xo, linear e ondulado). Para tanto, foi feito um levantamento bibliográfi co sobre as variáveis utilizadas para a prescrição do treinamento resistido, assim como uma revisão sistemática de artigos encontrados nas seguintes bases de dados: Pubmed e Scielo. A constatação principal da presente revisão foi que o modelo ondulado é o mais efi ciente para o aumento de força máxima e potência, seguido pelo linear e por último o fi xo, embora sejam necessárias mais investigações enfocando resistência de força e hipertrofi a muscular.

Originating from Germany and former Union of Soviet Socialist Republics (USSR), the training periodization theory was developed in the middle of the 20th Century, the so-called scientifi c period, based on the General Adaptation Syndrome theory (GAS). The scientifi c literature on strength training understands periodization as the systematic variation of intensity and volume aiming at more effi ciently developing one or more physical abilities. This paper aimed at analyzing the effect of periodization on strength training as related to its specifi c adaptations and comparing the most recurrent models (fi xed, linear, and undulating). For that, a bibliographic survey on the training variables used to prescript resistance training was carried out, as well as a systematic review of the articles found in the following databases: Pubmed and Scielo. The main fi nding of this review was that the undulated model is the most effective one for increasing maximum strength and power, followed by the linear one, and lastly by the fi xed one, although more investigation focusing on strength resistance and muscle hypertrophy is required.