BackgroundCapillary rather than venipuncture may be a simpler and less invasive blood collection protocol that would increase the number of potential sampling tests. However, if capillary sampling can be used as an alternative to venipuncture to determine changes in plasma, total creatine kinase (CK) activity in response to a football training session is poorly known.ObjectiveThis study aims to determine whether capillary blood sampling would provide representative measures of total CK activity compared to venipuncture in response to a football training session-induced elevated CK plasma levels.MethodsTwenty-two players from an under-19 football team performed a simulated football match with 11 players on each team for 90 minutes total duration (two halves of 45 minutes with 15 minutes rest between). Venous and ear lobe capillary blood samples were collected before and after (24h and 48h) the training session. Athletes retested for three consecutive days after exercise during the recovery week.ResultsThe simulated match significantly increased (P< 0.05) total CK activity as determined in both venous (1.7-fold) and capillary (1.9-fold) blood sampling. Total CK activity determined using capillary samples demonstrated significant correlation (r = 0.85; P < 0.01) and an elevated concordance Lin index (pc = 0.80) when compared to venous sampling total CK. The Bland–Altman plot showed capillary sampling CK overestimated venous CK levels by 130 U/L (61%), with moderated variance and low bias.ConclusionsOur results demonstrated that capillary sampling for total CK activity assay may be considered a reliable alternative to venipuncture to determine changes in plasma total CK activity in response to a football training session.

The present study aimed to investigate the influence of months of birth on anthropometry, body composition, biological maturation, and motor performance in young Brazilian soccer players. Young Brazilian soccer players from the Under-13 (n = 50; 13.6 ± 0.3 years), Under-15 (n = 50; 15.5 ± 0.4 years), and Under-17 categories (n = 46; 17.7 ± 0.3 years) took part in this study. Athletes were divided according to chronological age, 1st tertile (January to April); 2nd tertile (May to August); and 3rd tertile (September to December). Anthropometry, body composition, biological maturation, and motor performance variables were evaluated for all participants. There were no differences between the U-13, U-15, and U-17 categories regarding birth tertiles (p > 0.05). Differences between the ages and birth tertiles were observed for the stature, body mass, and lean body mass (p < 0.05). Moreover, differences were found in maturational status between the ages and birth tertiles (p < 0.05). In general, U-13 players showed lower values compared to U-15 and U-17 players in tests of motor performance. In addition, there was a difference in motor performance between the birth tertiles only for RSA variables. The months of birth influenced the stature, body mass, lean body mass, and repeated sprint ability in the U-13 and U-15 categories. Thus, care should be taken during the process of talent selection, as many young players could be underestimated due to their date of birth.

Determine the relationship between changes in oxidative stress markers, muscle damage, DOMS, and their relationship with performance in response to a session of football training during a 1-week recovery period of young football players. Methods: Nineteen young football players aged 16.7±1.0 years were included in the study. After initial evaluation for basal levels of oxidative stress and muscle damage markers, DOMS, and performance testing (Vertical Jump, Agility T-test, and RAST potency test), the athletes were submitted to a routine training session composed of squatting exercises, followed by a simulated football match of 45 minutes. Athletes were reevaluated for 3 consecutive days (24h, 48h, and 72h after the training session) during the recovery week. Results: An elevated DOMS score in the quadriceps and posterior thigh (P<0.05) and serum CK was observed 24h to 72h after the training session. Despite elevated DOMS and CK muscle damage markers, no changes were observed in the vertical jump test, RAST potency test, or agility T-test during the recovery week. In addition, no changes in the oxidative stress markers analyzed MDA, AOPP, and GSH were observed during the recovery week. Conclusion: Training sessions with squatting exercises and simulated matches promote a rise in CK and DOMS, but not sufficient to impair physical performance during the training week in young players.

Introdução: O chute é uma habilidade técnica imprescindível utilizada no Futebol, e é através dela que, na maioria das vezes, se alcança o gol. Objetivo: Verificar a relação entre a simetria da força em membros inferiores e sua influência na precisão do chute em atletas de Futebol de diferentes idades. Método: A amostra foi composta por 41 atletas de Futebol, do sexo masculino, com média de 16+1,1 anos de idade, de 63,7+9,52 kg de peso corporal, de 1,74+0,08m de altura e com um IMC 20,8+1,9, que realizaram testes específicos de salto vertical para avaliar a força de membros inferiores e o teste de precisão de chute Mor e Christian (1979). No teste de avaliação da força, os atletas executaram os saltos tanto com ambos os pés, como na forma unilateral, sendo o Squat Jump (SJ), Contra-Movimento (CM) e o Contra-Movimento com Auxílio dos Braços (Li). Nos três testes não era permitido o atleta recolher os pés para trás ou jogá-los para frente. No teste de precisão do chute, uma meta regulamentar de Futebol (7,32 x 2,44m) foi dividida em áreas de resultados por duas cordas fixadas no travessão a 1,22 m de cada poste da meta, de modo a ser dividida em quatro zonas de pontuação (1,20m cada). Os atletas executaram o chute em uma bola estacionária com o pé dominante, em qualquer ponto ao longo da linha de chute a 14,5m de distância da meta, sendo realizados quatro chutes em cada zona de pontuação. Para uma melhor visualização dos desempenhos alcançados pelos atletas, optou-se por criar grupos amostrais de acordo com a posição específica e com a perna de chute. A análise estatística adotada foram as medidas de tendência central, através do software Microsoft Excel. Resultados: Ao averiguar a pontuação no teste de precisão de chute por dominância e posição, os atletas destros das posições Atacante (82+27,5), Goleiro (86+22,2), Meio Campo (91,3+19,9) e Zagueiro (97+34,6), e os atletas canhotos da posição Lateral (105+22,5), conseguiram se sair melhor no referido teste. Ao verificar grupos que obtiveram melhores resultados no teste de chute, em relação às melhores médias de desempenho no teste de salto unilateral, percebe-se que os grupos que tiveram resultados melhores saltando com a perna de apoio foram os Atacantes/Destros (26,4+5,5), Goleiros/Destros (23,7+5,8) e Meio Campo/Canhotos (23,9+3,4). Por outro lado, o grupo Lateral/Canhoto (25,7+0,9) e Zagueiro/Destro (23,9+4,3), tiveram melhores desempenhos com a perna em que executam o chute.  Considerações finais: Os atletas que obtiveram melhores resultados na precisão de chute foram os que obtiveram melhores resultados quando realizaram o salto com a perna de apoio, reforçando a hipótese que se tem mais força na perna de apoio, devido a esta fornecer mais estabilidade para o corpo neste movimento.

No abstract