Effects of caffeine on time to exhaustion in exercise performed below and above the anaerobic threshold

Controversy still exists concerning the potential ergogenic benefit of caffeine (CAF) for exercise performance. The purpose of this study was to compare the effects of CAF ingestion on endurance performance during exercise on a bicycle ergometer at two different intensities, i.e., approximately 10% below and 10% above the anaerobic threshold (AT). Eight untrained males, non-regular consumers of CAF, participated in this study. AT, defined as the intensity (watts) corresponding to a lactate concentration of 4 mM, was determined during an incremental exercise test from rest to exhaustion on an electrically braked cycle ergometer. on the basis of these measurements, the subjects were asked to cycle until exhaustion at two different intensities, i.e., approximately 10% below and 10% above AT. Each intensity was performed twice in a double-blind randomized order by ingesting either CAF (5 mg/kg) or a placebo (PLA) 60 min prior to the test. Venous blood was analyzed for free fatty acid, glucose, and lactate, before, during, and immediately after exercise. Rating of perceived exertion and time to exhaustion were also measured during each trial. There were no differences in free fatty acids or lactate levels between CAF and PLA during and immediately after exercise for either intensity. Immediately after exercise glucose increased in the CAF trial at both intensities. Rating of perceived exertion was significantly lower (CAF = 14.1 ± 2.5 vs PLA = 16.6 ± 2.4) and time to exhaustion was significantly higher (CAF = 46.54 ± 8.05 min vs PLA = 32.42 ± 14.81 min) during exercise below AT with CAF. However, there was no effect of CAF treatment on rating of perceived exertion (CAF = 18.0 ± 2.7 vs PLA = 17.6 ± 2.3) and time to exhaustion (CAF = 18.45 ± 7.28 min vs PLA = 19.17 ± 4.37 min) during exercise above AT. We conclude that in untrained subjects caffeine can improve endurance performance during prolonged exercise performed below AT and that the decrease of perceived exertion can be involved in this process

Effect of an acute β-adrenergic blockade on exercise intensity corresponding to the lactate minimum

β-Adrenoreceptor blockade is reported to impair endurance, power output and work capacity in healthy subjects and patients with hypertension. The purpose of this study was to investigate the effect in eighth athletic males of an acute β-adrenergic blockade with propranolol on their individual power output corresponding to a defined lactate minimum (LM). Eight fit males (cyclist or triathlete) performed a protocol to determine the power output corresponding to their individual LM (defined from an incremental exercise test after a rapidly induced exercise lactic acidosis). This protocol was performed twice in a double-blind randomized order by each athlete first ingesting propranolol (80mg) and in a second trial a placebo, 120 minutes respectively prior to the test sequence. The blood lactate concentration obtained 7 minutes after anaerobic exercise (a Wingate test) was significantly lower after acute β-adrenergic blockade (8.6 ± 1.6mM) than under the placebo condition (11.7 ± 1.6mM). The work rate at the LM was lowered from 215.0 ± 18.6 to 184.0 ± 18.6 watts and heart rate at the LM was reduced from 165 ± 1.5 to 132 ± 2.2 beats/minute as a result of the blockade. There was a non-significant correlation (r = 0.29) between the power output at the LM with and without acute β-adrenergic blockade. In conclusion, since the intensity corresponding to the LM is related to aerobic performance, the results of the present study, are able to explain in part, the reduction in aerobic power output produced during β-adrenergic blockade.

Oxygen uptake kinetics and time to exhaustion in cycling and running: A comparison between trained and untrained subjects

The objective of the present study was to compare pulmonary gas exchange kinetics (VO 2 kinetics) and time to exhaustion (Tlim) between trained and untrained individuals during severe exercise performed on a cycle ergometer and treadmill. Eleven untrained males in running (UR) and cycling (UC), nine endurance cyclists (EC), and seven endurance runners (ER) were submitted to the following tests on separate days: (i) incremental test for determination of maximal oxygen uptake (VO 2max) and the intensity associated with the achievement of VO 2max (IVO 2max) on a mechanical braked cycle ergometer (EC and UC) and on a treadmill (ER and UR); (ii) all-out exercise bout performed at IVO 2max to determine the time to exhaustion at IVO 2max (Tlim) and the time constant of oxygen uptake kinetics (τ). The τ was significantly faster in trained group, both in cycling (EC = 28.2 ± 4.7 s; UC = 63.8 ± 25.0 s) and in running (ER = 28.5 ± 8.5 s; UR = 59.3 ± 12.0 s). Tlim of untrained was significantly lower in cycling (EC = 384.4 ± 66.6 s vs. UC; 311.1 ± 105.7 s) and higher in running (ER = 309.2 ± 176.6 s vs. UR = 439.8 ± 104.2 s). We conclude that the VO 2 kinetic response at the onset of severe exercise, carried out at the same relative intensity is sensitive to endurance training, irrespective of the exercise type. The endurance training seems to differently influence Tlim during exercise at IVO 2max in running and cycling. © 2003 Taylor & Francis Ltd.

A new neolignan and antioxidant phenols from Nectandra grandiflora

The EtOH crude extract from the leaves of Nectandra grandiflora collected in the Atlantic Forest, Brazil, showed antioxidant activity towards β-carotene in a TLC assay. The bioassay-guided fractionation led to the isolation of protocatechuic acid and two flavonol glycosides: afzelin and quercetrin, which showed free radical scavenging activity towards DPPH (ΔA 32, 16 and 73% at 50 μmol L-1) and were compared to commercial antioxidants rutin (81% at 50 μmol L-1) and BHT (9% at 50 μmol L-1), used as standard compounds. Additionally, three inactive neolignans, including the new bicycle[3.2.1]octane neolignan 2′-oxo-piperol B were obtained and characterized by spectrometric methods. ©2005 Sociedade Brasileira de Química.

O limiar de esforço percebido (LEP) corresponde à potência crítica e a um indicador de máximo estado estável de consumo de oxigěnio

The perceived exertion has been a target of several investigations, many times with association with objective physiological indicators in exercise. Recently, the identification of the perceived exertion threshold (PET) was proposed in the water running, which presented no difference in relation to the critical velocity. Theoretically, both parameters would be indicators of the maximum steady state of variables such as V̇O2 and blood lactate. The objective of this work was to verify the coincidence between PET, critical power (PCrit) and an indicator of maximum V̇O2 steady state (PCrit') in cycle ergometer. Eight male participants were submitted to progressive effort test in order to determine V̇O2peak (46.7 ± 8.5 ml/kg/min) and to four rectangular tests until exhaustion for the estimation of the critical power model parameters, PET and PCrit'. The hyperbolic relation between mechanical power and time spent for the V̇O2peak to be reached in each test was used for the PCrit' estimation, considered as the asymptote in the power axis, and the portion of the anaerobic work capacity (CTAnaer) depleted up to the establishment of the V̇O2peak (CTAnaer'). In order to identify PET, the straight lines angular coefficients of the perceived exertion in time (ordinate) and the powers used (abscissa) were adjusted to a linear function that provided a point in the power axis in which the perceived exertion would be kept indefinitely stable. The parameters PCrit and CTAnaer were estimated by means of the power-time non-linear equation. In order to compare the estimations of PET, PCrit and PCrit', the analysis of variance ANOVA for repeated measurements was employed, and the associations were established through the Pearson correlation. CTAnaer and CTAnaer' were compared through the t test. PET (180 W ± 61 W), PCrit (174 W ± 43 W) and PCrit' (176 W ± 48 W) were not significantly different and the correlations were of 0.92-0.98. CTAnaer' (14,080 ± 5,219 J) was lower than CTAnaer (22,093 ± 9,042 J). One concludes that the PET predicts the intensity of PCrit and PCrit' with accuracy.

Dental trauma involving root fracture and periodontal ligament injury: A 10-year retrospective study

The purpose of this retrospective study was to analyze the cases of traumatic dental injuries involving root fracture and/or periodontal ligament injury (except avulsion) treated at the Discipline of Integrated Clinic, School of Dentistry of Araçatuba, São Paulo State University (UNESP), Brazil, from January 1992 to December 2002. Clinical and radiographic records from 161 patients with 287 traumatized teeth that had sustained root fracture and/or injuries to the periodontal ligament were examined. The results of this survey revealed that subluxation (25.09%) was the most common type of periodontal ligament injury, followed by extrusive luxation (19.86%). There was a predominance of young male patients and most of them did not present systemic alterations. Among the etiologic factors, the most frequent causes were falls and bicycle accidents. Injuries on extraoral soft tissues were mostly laceration and abrasion, while gingival and lip mucosa lacerations prevailed on intraoral soft tissues injuries. Radiographically, the most common finding was an increase of the periodontal ligament space. The most commonly performed treatment was root canal therapy. Within the limits of this study, it can be concluded that traumatic dental injuries occur more frequently in young male individuals, due to falls and bicycle accidents. Subluxation was the most common type of periodontal ligament injury. Root canal therapy was the type of treatment most commonly planned and performed.

Severe fracture of the maxillary alveolar process associated with extrusive luxation and tooth avulsion: A case report

Aim: The aim of this report is to present a case of severe fracture of the maxillary anterior alveolar process with substantial bone dislodgement associated with extrusive tooth luxation and avulsion. Background: Dentoalveolar trauma is a challenge to dentistry, especially in young patients, for it can lead to early tooth loss which compromises oral function, esthetics, self-esteem, and alter the long-term plan of care for the victim. Case Report: A 12-year-old girl with severe dentoalveolar trauma to the maxillary anterior region presented for emergency care for her injury. Treatment consisted of fracture reduction of the alveolar process, repositioning of the teeth that had suffered extrusive luxation, placement of a semi-rigid splint, and suturing of soft tissue lacerations. The traumatized teeth presented with pulpal necrosis and were treated endodontically. After 24 months of follow up, the fracture of the alveolar process was completely healed and the displaced teeth presented no signs of ankylosis or root resorption. Summary: First-aid care contributed remarkably to this case allowing the re-establishment of esthetics, function, and patient's self-esteem. In spite of trauma extension the treatment outcomes were favorable. Clinical Significance: Cases of dentoalveolar trauma should be evaluated on an individual basis. However, early emergency management and adequate follow-up can prevent further complications and contribute to treatment success.

Are early and late rate of force development differently influenced by fast-velocity resistance training?

This study examined the effect of fast-velocity concentric isokinetic resistance training (FV) on the rate of force development (RFD) at early (<100 ms) and late phases (>100 ms) of rising muscle force. Nine men participated in a 6-week resistance training intervention for the lower body, and nine matched subjects participated as controls (CON). During concentric isokinetic (180°s-1) knee extension training, subjects were instructed to do each contraction 'as fast and forcefully as possible'. Maximal muscle strength (MVC) and RFD (0-10, 0-20, ..., 0-250 ms from the onset of contraction) were measured during maximal voluntary isometric contraction of the knee extensors (KE). There were no significant changes in MVC of KE in both groups after intervention (FV = 314·2 ± 101·1 versus 338·7 ± 88·0 N{bullet operator}m, P>0·05; CON = 293·3 ± 94·8 versus 280·0 ± 72·2 N{bullet operator}m, P>0·05). The RFD increased 39-71% at time intervals up to 90 ms from the onset of the contraction (P<0·05), whereas no change occurred at later time intervals. Similarly, relative RFD (i.e.%MVC{bullet operator}s-1) (RFDr) increased 33-56% at time intervals up to 70 ms from the onset of the contraction (P<0·05). It can be concluded that a short period of resistance training performed with concentric fast-velocity isokinetic muscle contractions is able to enhance RFD and RFDr obtained at the early phase of rising muscle force. © 2013 The Authors Clinical Physiology and Functional Imaging © 2013 Scandinavian Society of Clinical Physiology and Nuclear Medicine.

Estudo clínico comparativo do aquecimento por eletroestimulação ou bicicleta estacionária como preparação ao alongamento muscular

Pós-graduação em Bases Gerais da Cirurgia - FMB

Estudo sobre os efeitos de tensões residuais na vida em fadiga da liga de alumínio 6013-T6, em perfil tubular, submetidas a shot peening

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

As operações de paz da ONU no pós-guerra fria: a atuação brasileira no Timor Leste

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Bikeways and intermodality between bicycles and public transport

Analyses how the bicycle has evolved as a form of transport and outlines a bicycle traffic scheme. It provides examples showing that bicycles are a valid alternative to cars and can be integrated into a transport chain.

Ensaios mecânico e aplicação da lógica fuzzy para avaliação do canote do garfo

A inovação tecnológica tem sido um dos fatores fundamentais que levam grandes empresas a permanecerem no topo do ranking mundial do mercado globalizado, de acordo com o avanço tecnológico o setor de engenharia tem buscado soluções que ofereçam resultados positivos em prol do crescimento de sua empresa ou organização. Métodos de simulação para avaliação do comportamento mecânico de produtos submetidos a cargas estáticas e cargas dinâmicas são extremamente necessárias para redução dos custos de fabricação dos produtos. O uso de ensaios mecânicos e virtuais é de vital importância para avaliação do produto. O presente trabalho teve como objetivo a utilização da lógica fuzzy em um produto chamado canote do garfo da bicicleta, onde foi analisado além do grau de pertinência variado entre 0 e 1, o grau de veracidade também variado entre 0 e 1, tendo como foco principal o comportamento do produto canote do garfo e sua validação.

Limites da engenharia de transporte e a estrada minada: o caso da BR 316, Km 0 ao Km 10

A Organizaçãao Mundial da Sáude caracteriza o trânsito como um problema de sáude pública, motivo pelo qual se justificam as preocupações e os esforços de diversos países em criar políticas que venham a frear os índices cada vez mais crescentes de acidentes de trânsito que trazem prejuízos sociais e financeiros a todos. Neste sentido, a conservação da infraestrutura das rodovias ganha um papel relevante nas discussões que tratam os acidentes e suas causas, vez que a infraestrutura de uma rodovia pode ser apontada como um fator determinante para tais ocorrências. Diante disto, esta dissertação tem como objetivo investigar de que forma a precariedade estrutural da Rodovia Federal BR 316, entre os quilômetros 0 ao 10, potencializou a ocorrência de acidentes de trânsito nos anos de 2009 a 2012. Para tanto, lançou-se mão de uma metodologia baseada em explorações teóricas aliadas a análise de informações provenientes do banco de dados da Polícia Rodoviária Federal e pesquisa de campo, materializada a partir da apresentação de fotos ilustrativas do trecho pesquisado, possibilitando o desenvolvimento de um novo Índice de Qualidade para a Rodovia. Os dados colhidos foram tratados a partir da aplicação das técnicas estatísticas análise descritiva e análise multivariada a fim de confirmar a hipótese suscitada. Destaque-se que, no trecho pesquisado o fluxo de veículos e pedestres é intenso e, além, é um intervalo quilométrico que apresenta diversos problemas estruturais como, por exemplo, o aumento e a diminuição do número de pistas de rolamento, a má qualidade dos retornos, a falta de segurança e higiene das passarelas, a descontinuidade dos acostamentos, a inadequação das paradas de ônibus, enfim. No que tange à acidentes e às suas causas, pôde-se constatar que no ano de 2010 houveram mais ocorrências, especialmente, do tipo colisão com bicicleta, colisão com objeto móvel, colisão frontal e colisão transversal, motivadas por desobediência à sinalização, velocidade incompatível, ingestão de álcool, dentre outros. Finalmente, deve-se ressaltar o fato de que nos trechos considerados ruins, além da falta de atenção, a principal causa de acidentes é o defeito na via, corroborando-se então, a hipótese que a precariedade da infraestrutura da rodovia potencializou as ocorrências de acidentes de trânsito, no período de 2009 a 2012. Diante disto, é possível afirmar que o acidente de trânsito é um fato social, consubstanciando como um problema que abarca aspectos sociopolíticos e culturais da sociedade moderna, mas que também é potencializado pelo estado de conservação estrutural das Rodovias.

Analise eletromiográfica e dinamométrica durante o ciclio da pedalada em cicloergômetro aquático

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)