Influence of a slow-start on overall performance and running kinematics during 6-h ultramarathon races.

The aim of this study was to describe the pacing during a 6-h ultramarathon (race 1) and to investigate whether a slow-start affects performance, running kinematic changes, ratings of perceived exertion (RPE) and fatigue (ROF) (race 2). After a critical speed test, participants completed two 6-h ultramarathons. Race 1 (n = 16) was self-paced, whereas in race 2 (n = 10), athletes performed the initial 36 min at speeds 18% below the mean speed of the initial 36 min of race 1. In race 1, participants adopted an inverse sigmoid pacing. Contact times increased after 1 h, and flight times decreased after 30 min (all P ≤ .009); stride length reduced after 1 h 30 min (all P = .022), and stride frequency did not change. Despite the lower speeds during the first 10% of race 2, and higher speeds at 50% and 90%, performance remained unchanged (57.5 ± 10.2 vs. 56.3 ± 8.5 km; P = .298). However, RPE and ROF were lowered for most of race 2 duration (all P < .001). For the comparison of kinematic variables between races, data were normalised by absolute running speed at each time point from 1 h onwards. No differences were found for any of the kinematic variables. In conclusion, decreasing initial speed minimises RPE and ROF, but does not necessarily affect performance. In addition, running kinematic changes do not seem to be affected by pacing manipulation.

Pacing Strategy During 24-Hour Ultramarathon-Distance Running.

PURPOSE: To describe pacing strategy in a 24-h running race and its interaction with sex, age group, athletes' performance group, and race edition. METHODS: Data from 398 male and 103 female participants of 5 editions were obtained based on a minimum 19.2-h effective-running cutoff. Mean running speed from each hour was normalized to the 24-h mean speed for analyses. RESULTS: Mean overall performance was 135.6 ± 33.0 km with a mean effective-running time of 22.4 ± 1.3 h. Overall data showed a reverse J-shaped pacing strategy, with a significant reduction in speed from the second-to-last to the last hour. Two-way mixed ANOVAs showed significant interactions between racing time and both athlete performance group (F = 7.01, P < .001, ηp2 = .04) and race edition (F = 3.01, P < .001, ηp2 = .02) but not between racing time and either sex (F = 1.57, P = .058, ηp 2 < .01) or age group (F = 1.25, P = .053, ηp2 = .01). Pearson product-moment correlations showed an inverse moderate association between performance and normalized mean running speed in the first 2 h (r = -.58, P < .001) but not in the last 2 h (r = .03, P = .480). CONCLUSIONS: While the general behavior represents a rough reverse J-shaped pattern, the fastest runners start at lower relative intensities and display a more even pacing strategy than slower runners. The "herd behavior" seems to interfere with pacing strategy across editions, but not sex or age group of runners.

Aerobic and Anaerobic Energy During Resistance Exercise at 80% 1RM.

The present study investigated the accumulated oxygen deficit (AOD) method to assess the energy cost in resistance exercises (RE). The aim of the study was to evaluate the aerobic and anaerobic energy release during resistance exercises performed at 80% 1-RM in four exercises (half squat, bench press, triceps extension and lat pull down), as well as the accuracy of its estimation. The sample comprised 14 men (age = 26.6 ± 4.9 years; height = 177.7 ± 0.1 cm; body mass = 79.0 ± 11.1 kg; and estimated fat mass = 10.5 ± 4.6%). Test and re-test of 1-RM were applied to every exercise. Low-intensity bouts at 12, 16, 20, and 24% of 1-RM were conducted. Energy cost was then extrapolated to 80% 1-RM exhaustive bout and relative energy contribution were assessed. By utilizing the AOD method, the results of the present study suggest a great proportion of anaerobic metabolism during exercise at 80% 1-RM in the four RE that were analyzed: Bench press = 77,66±6,95%; Half squat = 87,44±6,45%; Triceps extension = 63,91±9,22%; Lat pull down = 71,99±13,73 %. The results of the present study suggest that AOD during resistance exercises presents a pattern that does not match the reports in the literature for other types of exercise. The accuracy of the total energy demand estimation at 80% 1-RM was acceptable in the Bench press, in the Triceps extension and in the Lat pull down, but no in the Half squat. More studies are warranted to investigate the validity of this method in resistance exercise.

Prevalência do anticorpo da hepatite A em crianças e adolecentes com hepatopatia crônica / Prevalence of hepatitis A anibody in children and adolescents with chronic liver disease

Objetivo: avaliar a prevalência de hepatite viral A (HVA) em crianças e adolescentes portadores de doenças crônicas do fígado, em um serviço de hepatologia pediátrica. Métodos: entre maio de 1999 e fevereiro de 2001, foi estudada a prevalência de anticorpos anti-HVA total em 60 crianças e adolescentes, entre 1 e 16 anos de idade, portadoras de hepatopatias crônicas, provenientes da unidade de gastroenterologia pediátrica e programa de transplante hepático infantil do serviço de pediatria do Hospital de Clínicas de Porto Alegre. O anti-HVA, realizado através de um teste laboratorial comercialmente disponível em nosso meio (Abbott - MEIA HAVAB - sistema AXSYM), foi determinado e relacionado com a idade, com o sexo, com a cor, com o diagnóstico etiológico da hepatopatia e com a renda familiar dos pacientes.Resultados: apenas uma criança de 1 ano, portadora de atresia biliar, foi excluÝda do estudo por apresentar anti-HVA indeterminado, em duas ocasiões. Das 59 crianças restantes, 14 (24por cento) apresentavam resultados positivos para o anti-HVA total. As idades dos pacientes com anti-HVA positivos variaram de 1 a 16 anos (x= 7, 7 anos e mediana 8,5 anos). NÒo houve diferença significante entre idade, sexo e cor entre os grupos positivo e negativo. A renda familiar foi menor no grupo dos pacientes anti-HVA positivo, mas nÒo mostrou diferença estatÝstica significante. A diferença de prevalÛncia de anti-HVA entre as etiologias das hepatopatias estß, provavelmente, relacionada Ó idade mais do que ao diagnóstico. Conclusões: na populaçÒo estudada,...

[Prevalence of hepatitis A antibody in children and adolescents with chronic liver disease]. / Prevalência do anticorpo da hepatite A em crianças e adolescentes com hepatopatia crônica.

OBJECTIVE: To evaluate the prevalence of Hepatitis A virus (HAV) in children and adolescents with chronic liver disease in a unit of pediatric hepatology. METHODS: Between May 1999 and February 2001, we studied the prevalence of anti-HAV in 60 children and adolescents with chronic liver disease, aged between 1 and 16 years, from the Unit of Pediatric Hepatology of the Hospital de Clínicas de Porto Alegre. The total anti-HAV was determined by a commercially available competitive ELISA method (Abbott), and compared with age, sex, race, etiologic diagnosis and family income of each patient. RESULTS: A one-year old child was not included in the study because she presented twice with undetermined anti-HAV results. Among the other 59 patients, 14 (24%) presented a positive result of total anti-HAV. The ages of test-positive subjects varied between 1 and 16 years old (mean=7.7 years, median=8.5). The differences between positive and negative groups in relation to age, sex and race were not statistically significant. Family income was lower in anti-HAV positive patients, but this difference was not significant. The differences between the etiologies of liver diseases were probably more related to the age than to the etiologies of the diseases. CONCLUSIONS: In the studied population, the majority (76%) of children and adolescents with chronic liver disease are susceptible to hepatitis A virus infection and, consequently, they could present a more severe disease or even fulminant hepatitis A. We strongly suggest that these subjects receive Hepatitis A inactivated vaccine.