RESUMO
In swimming, the speed-time relationship provides the critical speed (CS) and the maximum distance that can be performed above CS (D'). During intermittent severe intensity exercise, a complete D' depletion coincides with task failure, while a sub-CS intensity is required for D' reconstitution. Therefore, determining the balance D' remaining at any time during intermittent exercise (D'BAL) could improve training prescription. This study aimed to 1) test the D'BAL model for swimming; 2) determine an equation to estimate the time constant of the reconstitution of D' (τD'); and 3) verify if τD' is constant during two interval training sessions with the same work intensity and duration and recovery intensity, but different recovery duration. Thirteen swimmers determined CS and D' and performed two high-intensity interval sessions at a constant speed, with repetitions fixed at 50 m. The duration of passive recovery was based on the work/relief ratio of 2:1 (T2:1) and 4:1 (T4:1). There was a high variability between sessions for τD' (coefficient of variation of 306%). When τD' determined for T2:1 was applied in T4:1 and vice versa, the D'BAL model was inconsistent to predict the time to exhaustion (coefficient of variation of 29 and 28%). No linear or nonlinear relationships were found between τD' and CS, possibly due to the high within-subject variability of τD'. These findings suggest that τD' is not constant during two high-intensity interval sessions with the same recovery intensity. Therefore, the current D'BAL model was inconsistent to track D' responses for swimming sessions tested herein.
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PURPOSE: Although ischaemic preconditioning (IPC), induced by cycles of transient limb ischaemia and reperfusion, seems to improve exercise performance, the optimal duration of ischaemia-reperfusion cycles is not established. The present study investigated the effect of ischaemia-reperfusion duration within each IPC cycle on performance in a 2000-m rowing ergometer test. METHODS: After incremental and familiarization tests, 16 trained rowers (mean ± SD: age, 24 ± 11 years; weight, 74.1 ± 5.9 kg; [Formula: see text] peak, 67.2 ± 7.4 mL·kg-1·min-1) were randomly submitted to a 2000-m rowing test preceded by intermittent bilateral cuff inflation of the lower limbs with three cycles of ischaemia-reperfusion, lasting 5 min (IPC-5) or 10 min (IPC-10) at 220 or 20 mmHg (control). Power output, [Formula: see text], heart rate, blood lactate concentration, pH, ratings of perceived exertion (RPE), and near-infrared spectroscopy-derived measurements of the vastus lateralis muscle were continuously recorded. RESULTS: No differences among treatments were found in the 2000-m test (control: 424 ± 17; IPC-5: 425 ± 16; IPC-10: 424 ± 17 s; P = 0.772). IPC-10 reduced the tissue saturation index and oxy-haemoglobin concentration during exercise compared with control. The power output during the last 100-m segment was significantly lower with IPC-10. The IPC treatments increased the heart rate over the first 500 m and decreased the pH after exercise. No alterations were observed in [Formula: see text], blood lactate, or RPE among the trials. CONCLUSION: In conclusion, IPC does not improve the 2000-m rowing ergometer performance of trained athletes regardless of the length of ischaemia-reperfusion cycles.
Assuntos
Tolerância ao Exercício , Precondicionamento Isquêmico/métodos , Traumatismo por Reperfusão/fisiopatologia , Esportes Aquáticos/fisiologia , Adolescente , Adulto , Teste de Esforço , Hemodinâmica , Humanos , Masculino , Músculo Esquelético/irrigação sanguínea , Músculo Esquelético/fisiologia , Consumo de Oxigênio , Distribuição Aleatória , Traumatismo por Reperfusão/prevenção & controleRESUMO
Abstract The aims of the present study were to assess the reliability of long sprint cycling performance in a group of recreationally trained cyclists and to provide thresholds for changes in performance for this particular group of subjects in repeated measures designs through a scale of magnitudes. Repeatability of mean power output during a 1-min cycling time trial was assessed in a group of 15 recreationally trained cyclists (26 ± 5, years, 176 ± 5 cm, 78 ± 8 kg). They were tested on separate days, approximately one week apart. The test and retest values for the whole group of cyclists were 7.0 ± 0.5 W/kg and 6.9 ± 0.6 W/kg (systematic change and 90% confidence limits of -1.0% ± 1.1%). Our results indicated good test-retest reproducibility (typical error of 1.8%, 90% confidence limits of 1.4% to 2.6%; intraclass correlation coefficient of 0.96, confidence limits of 0.91 to 0.99), but suggested a reduction of mean power for the "slower" subjects on retest (-2.0%, 90% confidence limits of ±1.8%). If not monitored, this systematic decrease could interfere in results of studies utilizing groups with similar performance levels, particularly investigating strategies to improve performance in sprint cycling exercises around 1 min. The thresholds for moderate, large, very large and extremely large effects for mean power output on long sprint cycling performance are about 0.4%, 1.3%, 2.3%, 3.6%, and 5.8%, respectively.
Resumo Os objetivos do presente estudo foram avaliar a confiabilidade do desempenho de sprint longo no ciclismo em um grupo de ciclistas recreacionais e fornecer limiares para mudanças no desempenho para este grupo de sujeitos em delineamentos de medidas repetidas, através de uma escala de magnitudes. A reprodutibilidade da potência média durante um contrarrelógio de 1-min foi avaliada em um grupo de 15 ciclistas recreativamente treinados (26 ± 5 anos, 176 ± 5 cm, 78 ± 8 kg). Eles foram avaliados em dias separados, com aproximadamente uma semana de intervalo. Os valores de teste-reteste no contrarrelógio de 1-min para o grupo inteiro foram 7,0 ± 0,5 W/kg and 6,9 ± 0,6 W/kg (mudança sistemática e limite de confiança de 90% de -1,0% ± 1,2%). Nossos resultados indicam boa reprodutibilidade teste-reteste (erro típico de 1,8%, limite de confiança de 90% de 1,4% para 2,6%; coeficiente de correlação intraclasse de 0,96, limite de confiança de 90% de 0,91 para 0,99), mas sugeriu uma redução da média de potência para os sujeitos "mais lentos" no reteste (-2,0%, limite de confiança de 90% de ±1,8%). Se não monitorada, esta queda sistemática na potência pode interferir nos resultados de estudos utilizando grupos com níveis similares de desempenho, particularmente investigando estratégias para melhorar o desempenho em sprints com duração próxima a 1 min. Os limiares para efeitos moderado, grande, muito grande e extremamente grande para média da potência em sprint longo no ciclismo são aproximadamente 0,4%, 1,3%, 2,3%, 3,6% e 5,8%, respectivamente.
Assuntos
Humanos , Adulto , Ciclismo , Desempenho Atlético/estatística & dados numéricosRESUMO
A relação entre desempenhos em diferentes distâncias com seus respectivos tempos fornece um válido, barato e prático índice de avaliação da capacidade aeróbia para natação. Este índice, conhecido como Velocidade Crítica, tem recebido muita atenção por pesquisadores, pois possibilita a substituição de outros indicadores de capacidade aeróbia que geralmente são caros ou demandam demasiado tempo do período de treinamento. No entanto, ainda não foi realizada uma compilação de estudos tratando da Velocidade Crítica com outros índices de capacidade aeróbia na natação. Assim, o objetivo desta revisão foi comparar a relação da Velocidade Crítica com outros índices de capacidade aeróbia comumente utilizados na natação como: Teste de 30 Minutos, Máximo Estado Estável de Lactato, Limiar Anaeróbio e Velocidade Aeróbia Máxima. Foi realizada uma busca bibliográfica nas bases de dados PubMed e SciELO, utilizando-se as seguintes palavras-chave: "Critical swimming speed", "critical swimming velocity" e "velocidade crítica and natação". Ao fim do processo de seleção foram incluídos 21 artigos para esta revisão. Foi observado que a relação da Velocidade Crítica com o Limiar Anaeróbio e o Teste de 30 Minutos é dependente da idade dos nadadores, requerendo cautela quando comparados. Também foi observado que a Velocidade Crítica superestima a intensidade do Máximo Estado Estável de Lactato e do Limiar Anaeróbio em nadadores adultos, indicando delimitar os domínios do exercício pesado e severo na natação. Contudo, a Velocidade Crítica pode ser influenciada pelas distâncias preditivas utilizadas para sua determinação, e assim, devem ser cuidadosamente selecionadas. Por fim, a Velocidade Crítica apresenta boa correlação com os principais índices aeróbios representando ser um bom parâmetro para avaliação da capacidade aeróbia em nadadores....(AU)
The relationship between distance covered and the time needed to cover it at maximal speed provide a valid, cheap and practice index to evaluate aerobic capacity in swimming. This index, known as Critical Swimming Speed, has received much attention for researchers, because it could replace other aerobic capacity indexes that usually are more expensive and demand more time of training. However, there is no compilation of studies involving Critical Swimming Speed and other aerobic capacity index on the literature. Hence, the purpose of this literature review was comparing the relationship between Critical Swimming Speed with others aerobic capacity indexes generally used in swimming as: 30-min Test, Maximal Lactate Steady State, Anaerobic Threshold and Maximal Aerobic Speed. The articles were surveyed on the scientific bases PubMed and SciELO using the following keywords: "Critical swimming speed", "critical swimming velocity" and "velocidade crítica and natação" (on Portuguese). At the end of the search process, 21 articles were included in the revision. It was observed that the relationship between Critical Swimming Speed with Anaerobic Threshold and 30-min Test is affected by the age of the swimmers, demanding caution when comparing these indexes. It was also observed that the Critical Swimming Speed overestimates the Maximal Lactate Steady State and Anaerobic Threshold in adult swimmers, which indicates a boundary between the heavy and severe intensity domains during swimming exercises. However, the predictive distances used for the Critical Swimming Speed determination may influence on its final value and, thus, they should be carefully selected. Lastly, Critical Swimming Speed shows a good correlation with major aerobic indexes and represents a good aerobic capacity parameter to evaluate swimmers....(AU)
Assuntos
Humanos , Masculino , Feminino , Criança , Adolescente , Adulto , Atletas , Desempenho Atlético , Ácido Láctico , Consumo de Oxigênio , Educação Física e Treinamento , Natação , Medidores de VelocidadeRESUMO
Resumo O objetivo deste estudo foi determinar o modo e o grau com que variáveis aeróbias e anaeróbias influenciam o desempenho e a fadiga em "sprints" repetidos (RS) na corrida. Para este fim, participaram do estudo 24 homens, sendo oito corredores velocistas, oito corredores fundistas e oito sujeitos ativos. Em uma pista sintética de atletismo estes sujeitos foram submetidos aos seguintes testes: 1) teste incremental para determinação do VO2max e da velocidade aeróbia máxima (VAM); 2) teste de velocidade constante realizado a 110%VAM para determinar a cinética do VO2 durante exercício e o máximo déficit acumulado de oxigênio (MAOD); 3) teste de "sprints" repetidos (10 "sprints" de 35 m, intercalados com 20 s de recuperação) para determinar o tempo total dos "sprints" (TT), tempo do melhor sprint (TM) e a queda do desempenho em percentual (Sdec). Para analisar a diferença entre os grupos e as relações entre as variáveis foram utilizadas a análise de variância ANOVA "one-way", complementada pelo teste de Tukey, e a correlação de Pearson, respectivamente. O TT em RS foi diferente significativamente entre todos os grupos (velocistas, 49,5 ± 0,8 s; fundistas, 52,6 ± 3,1 s; ativos, 55,5 ± 2,6 s) e Sdec foi significativamente inferior em fundistas comparado aos outros grupos (velocistas, 8,9 ± 2,1%; fundistas, 4,0 ± 2,0%; ativos, 8,4 ± 4,4%). O TT foi correlacionado significativamente com o TM (r = 0,85, p < 0,01) e com o MAOD (r = - 0,54, p < 0,01). Além disso, Sdec foi correlacionado significativamente com variáveis aeróbias (VO2max, r = - 0,58, < 0,01; VAM, r = - 0,59, p < 0,01; constante de tempo "tau", r = 0,45, p = 0,03). Portanto, conclui-se que apesar de índices aeróbios influenciarem na redução da fadiga em RS, o desempenho em RS é principalmente influenciado por características anaeróbias.(AU)
Abstract This study aimed to determine the manner and degree to which aerobic and anaerobic variables influence repeated running sprint performance and ability. Twenty four males (sprinters = 8, endurance runners = 8 and physical active subjects = 8) performed in a synthetic track the following tests: 1) incremental test to determine the VO2max and the maximum aerobic velocity (MAV); 2) constant velocity test performed at 110% of MAV to determine the VO2 kinetics and the maximum accumulated oxygen deficit (MAOD); 3) repeated sprint test (10 sprints of 35-m interspersed by 20s) to determine sprint total time (TT), best sprint time (BT) and score decrement (Sdec). Between-groups comparisons and the correlations between variables were analyzed by one-way ANOVA with a Tukey post-hoc tests and Pearson correlation, respectively. TT was significantly different among all groups (sprinters = 49.5 ± 0.8 s; endurance = 52.6 ± 3.1 s; active = 55.5 ± 2.6 s) and Sdec was significantly lower in endurance runners as compared with sprinters and physical active subjects (sprinters = 8.9 ± 2.1%; endurance = 4.0 ± 2.0%; active = 8.4 ± 4.4%). TT correlated significantly with BT (r = 0.85, p < 0.01) and MAOD (r = - 0.54, p < 0.01). Moreover, Sdec was significantly correlated with aerobic parameters (VO2max, r = - 0.58, p < 0.01; MAV, r = - 0.59, p < 0.01; time constant tau, r = 0.45, p = 0.03). In conclusion, although the aerobic parameters have an important contribution to RS ability, RS performance is mainly influenced by anaerobic parameters.(AU)
Assuntos
Humanos , Masculino , Adulto , Desempenho Atlético , Consumo de Oxigênio , Educação Física e Treinamento , CorridaRESUMO
PURPOSE: Although high-intensity interval training (HIT) seems to promote greater improvements in aerobic parameters than continuous training, the influence of exercise intensity on [Formula: see text] on-kinetics remains under investigation. METHODS: After an incremental test, twenty-one recreationally trained cyclists performed several time-to-exhaustion tests to determine critical power (CP), and the highest intensity (I HIGH), and the lowest exercise duration (T LOW) at which [Formula: see text] is attained during constant exercise. Subjects also completed a series of step transitions to moderate- and heavy-intensity work rates to determine pulmonary [Formula: see text] on-kinetics. Surface electromyography (EMG) of vastus lateralis muscle and blood lactate accumulation (∆BLC) was measured during heavy exercise. Subjects were assigned to one of two 4-week work-matched training groups: the lower [105 % CP: n = 11; 4 × 5 min at 105 % CP (218 ± 39 W), 1 min recovery] or the upper [I HIGH: n = 10; 8 × 100 % I HIGH (355 ± 60 W), 1:2 work:recovery ratio] intensity of the severe exercise domain. RESULTS: The two interventions were similarly effective in reducing the phase II [Formula: see text] time constant during moderate (105 % CP: 34 ± 13 to 25 ± 8 s; I HIGH: 31 ± 9 to 23 ± 6 s) and heavy exercise (105 % CP: 25 ± 7 to 18 ± 5 s; I HIGH: 27 ± 7 to 16 ± 5 s) and in reducing the amplitude of [Formula: see text] slow component, EMG amplitude, and ∆BLC during heavy exercise. CONCLUSION: In conclusion, the short-term adjustments in response to step transitions to moderate and heavy exercise were independent of training intensity within the severe exercise domain.
Assuntos
Tolerância ao Exercício/fisiologia , Treinamento Intervalado de Alta Intensidade/métodos , Músculo Esquelético/fisiologia , Consumo de Oxigênio/fisiologia , Oxigênio/metabolismo , Esforço Físico/fisiologia , Limiar Anaeróbio/fisiologia , Ciclismo/fisiologia , Metabolismo Energético/fisiologia , Feminino , Humanos , Cinética , Ácido Láctico/sangue , Masculino , Taxa de Depuração Metabólica , Força Muscular/fisiologia , Fatores de Tempo , Adulto JovemRESUMO
To investigate the impact of different training backgrounds on pulmonary oxygen uptake (VÌO2) responses during all-out and supramaximal constant-velocity running exercises, nine sprinters (SPRs) and eight endurance runners (ENDs) performed an incremental test for maximal aerobic velocity (MAV) assessment and two supramaximal running exercises (1-min all-out test and constant-velocity exercise). The VÌO2 responses were continuously determined during the tests (K4b2, Cosmed, Italy). A mono-exponential function was used to describe the VÌO2 onset kinetics during constant-velocity test at 110%MAV, while during 1-min all-out test the peak of VÌO2 (VÌO2peak), the time to achieve the VÌO2peak (tVÌO2peak) and the VÌO2 decrease at last of the test was determined to characterize the VÌO2 response. During constant-velocity exercise, ENDs had a faster VÌO2 kinetics than SPRs (12.7 ± 3.0 vs. 19.3 ± 5.6 s; p < 0.001). During the 1-min all-out test, ENDs presented slower tVÌO2peak than SPRs (40.6 ± 6.8 and 28.8 ± 6.4 s, respectively; p = 0.002) and had a similar VÌO2peak relative to the VÌO2max (88 ± 8 and 83 ± 6%, respectively; p = 0.157). Finally, SPRs was the only group that presented a VÌO2 decrease in the last half of the test (-1.8 ± 2.3 and 3.5 ± 2.3 ml.kg-1.min-1, respectively; p < 0.001). In summary, SPRs have a faster VÌO2 response when maximum intensity is required and a high maximum intensity during all-out running exercise seems to lead to a higher decrease in VÌO2 in the last part of the exercise.
Assuntos
Consumo de Oxigênio/fisiologia , Corrida/fisiologia , Adulto , Humanos , Cinética , Pulmão/fisiologia , Masculino , Metabolismo , Resistência Física , Fatores de Tempo , Adulto JovemRESUMO
Abstract The severe-intensity domain has important applications for the prescription of running training and the elaboration of experimental designs. The objectives of this study were: 1) to investigate the validity of a previously proposed model to estimate the shortest exercise duration (TLOW) and the highest velocity (VHIGH) at which VO2 max is reached during running, and 2) to evaluate the effects of aerobic training status on these variables. Eight runners and eight physically active subjects performed several treadmill running exercise tests to exhaustion in order to mathematically estimate and to experimentally determine TLOW and VHIGH. The relationship between the time to achieve VO2 max and time to exhaustion (Tlim) was used to estimate TLOW. VHIGH was estimated using the critical velocity model. VHIGH was assumed to be the highest velocity at which VO2 was equal to or higher than the average VO2 max minus one standard deviation. TLOW was defined as Tlim associated with VHIGH. Runners presented better aerobic fitness and higher VHIGH (22.2 ± 1.9 km.h-1) than active subjects (20.0 ± 2.1 km.h-1). However, TLOW did not differ between groups (runners: 101 ± 39 s; active subjects: 100 ± 35 s). TLOW and VHIGH were not well estimated by the model proposed, with high coefficients of variation (> 6%) and a low correlation coefficient (r<0.70), a fact reducing the validity of the model. It was concluded that aerobic training status positively affected only VHIGH. Furthermore, the model proposed presented low validity to estimate the upper boundary of the severe-intensity domain (i.e., VHIGH), irrespective of the subjects' training status.
Resumo O domínio severo tem importantes aplicações para a prescrição do treinamento de corrida e elaboração de delineamentos experimentais. O estudo teve como objetivos: 1) investigar a validade de um modelo proposto previamente para estimativa do menor tempo de exercício (TINF) e maior velocidade (VSUP) em que o VO2max é alcançado na corrida; e 2) comparar os efeitos do estado de treinamento nestes parâmetros. Oito corredores e oito indivíduos fisicamente ativos realizaram uma série de testes até a exaustão em esteira rolante para estimar matematicamente e determinar experimentalmente o TINF e VSUP. A relação entre tempo para atingir o VO2 max e tempo de exaustão (Tlim) foi usado para estimar o TINF. A VSUP foi estimada pelo modelo de Velocidade Crítica. VSUP foi assumida como a maior velocidade em que o VO2 ± 2,1 km.h-1. Entretanto, TINF não foi diferente entre grupos (Corredores 101 ± 39; Ativos: 100 ± 35 s). VSUP e TINF não foram bem estimados pelo modelo proposto e apresentaram altos coeficientes de variação (> 6%) e baixa correlação (r < 0,70), o que diminuiu a sua validade. Pode-se concluir que o estado de treinamento aeróbio afetou positivamente apenas a VSUP. Além disso, o modelo proposto apresentou baixa validade para predição do limite superior do domínio severo (VSUP) independentemente do estado de treinamento dos indivíduos.
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The focus of the present study was to investigate the effects of a fast-start pacing strategy on running performance and pulmonary oxygen uptake (VO2) kinetics at the upper boundary of the severe-intensity domain. Eleven active male participants (28±10 years, 70±5 kg, 176±6 cm, 57±4 mL/kg/min) visited the laboratory for a series of tests that were performed until exhaustion: 1) an incremental test; 2) three laboratory test sessions performed at 95, 100 and 110% of the maximal aerobic speed; 3) two to four constant speed tests for the determination of the highest constant speed (HS) that still allowed achieving maximal oxygen uptake; and 4) an exercise based on the HS using a higher initial speed followed by a subsequent decrease. To predict equalized performance values for the constant pace, the relationship between time and distance/speed through log-log modelling was used. When a fast-start was utilized, subjects were able to cover a greater distance in a performance of similar duration in comparison with a constant-pace performance (constant pace: 670 m±22%; fast-start: 683 m±22%; Pâ=â0.029); subjects also demonstrated a higher exercise tolerance at a similar average speed when compared with constant-pace performance (constant pace: 114 s±30%; fast-start: 125 s±26%; Pâ=â0.037). Moreover, the mean VO2 response time was reduced after a fast start (constant pace: 22.2 s±28%; fast-start: 19.3 s±29%; Pâ=â0.025). In conclusion, middle-distance running performances with a duration of 2-3 min are improved and VO2 response time is faster when a fast-start is adopted.
Assuntos
Pulmão/fisiologia , Oxigênio/metabolismo , Corrida/fisiologia , Adulto , Exercício Físico , Humanos , Cinética , Masculino , Consumo de Oxigênio/fisiologiaRESUMO
O objetivo do estudo foi analisar a influência da cafeína no desempenho dos 200 metros rasos (200 m). Dezessete indivíduos fisicamente ativos (21,5 ± 2,15 anos; 175,9 ± 5,5 cm; 74,1 ± 10,04 kg) executaram em dias diferentes duas performances de 200m. Uma hora antes do teste foi ingerido de modo duplo-cego e randomizado cápsula gelatinosa contendo cafeína (6mg.kg-1) ou placebo. Foram analisados o tempo final dos 200 m rasos e o lactato sanguíneo ([La]; repouso, pré-aquecimento e pós-teste). A ingestão de cafeína diminuiu significantemente o tempo no desempenho dos 200m em relação ao placebo (27,398 ± 1,626 vs. 27,596 ± 1,714 s, respectivamente) e aumentou as [La] pré-aquecimento (1,236 ± 0,497 vs 1,064 ± 0,330 mM) sem modificações na [La] pico. Assim, podemos concluir que a ingestão de cafeína exerceu efeito ergogênico no desempenho com característica anaeróbia, nos indivíduos ativos avaliados neste estudo. Contudo a ausência de modificação na [La] pico indica que essa melhora não parece estar relacionada a um maior fluxo glicolítico.
The aim of this study was to investigate the influence of caffeine ingestion on 200 meters performance (200 m). Seventeen physical education students (21.5 ± 2.15 years; 175.9 ± 5.5 cm; 74.1 ± 10.04 kg) performed on two different days two performances of 200 m. One hour before the performance the participants ingested a gelatin capsule containing either caffeine (6 mg.kg-1) or placebo in a randomized double-blinded manner. Were analyzed the end time of the 200 m race and blood lactate ([La]; rest, pre-warm-up and post-test) Caffeine intake decreased the time to overcome 200 m race compared to placebo intake (27.398 ± 1.626 and 27.596 ± 1.714 s, respectively) and increased blood lactate concentration [La] pre-warm-up (1.236 ± 0.497; 1.064 ± 0.330 mM, respectively) without modification in [La] peak. Thus, we conclude that caffeine intake exert an ergogenic effect on anaerobic performance, however analyzing the [La] peak, this improvement does not seem to be related to increased glycolytic flux.