Fernando Roberto De-Oliveira

Effect of carbohydrate availability on time to exhaustion in exercise performed at two different intensities

This study examined the effects of pre-exercise carbohydrate availability on the time to exhaustion for moderate and heavy exercise. Seven men participated in a randomized order in two diet and exercise regimens each lasting 3 days with a 1-week interval for washout. The tests were performed at 50% of the difference between the first (LT1) and second (LT2) lactate breakpoint for moderate exercise (below LT2) and at 25% of the difference between the maximal load and LT2 for heavy exercise (above LT2) until exhaustion. Forty-eight hours before each experimental session, subjects performed a 90-min cycling exercise followed by 5-min rest periods and a subsequent 1-min cycling bout at 125% VO2max/1-min rest periods until exhaustion to deplete muscle glycogen. A diet providing 10% (CHO(low)) or 65% (CHO(mod)) energy as carbohydrates was consumed for 2 days until the day of the experimental test. In the exercise below LT2, time to exhaustion did not differ between the CHO(mod) and the CHO(low) diets (57.22 +/- 24.24 vs 57.16 +/- 25.24 min). In the exercise above LT2, time to exhaustion decreased significantly from 23.16 +/- 8.76 min on the CHO(mod) diet to 18.30 +/- 5.86 min on the CHO(low) diet (P < 0.05). The rate of carbohydrate oxidation, respiratory exchange ratio and blood lactate concentration were reduced for CHO(low) only during exercise above LT2. These results suggest that muscle glycogen depletion followed by a period of a low carbohydrate diet impairs high-intensity exercise performance.

Insatisfação corporal e atividade física em adolescentes da região continental de Florianópolis

The relationship between physical activity and body dissatisfaction is little explored in literature. It was examined the body dissatisfaction and physical activity relationship among adolescents students of public schools from Florianopolis, Brazil. The sample was composed by 242 students, 109 boys (14,6±2,8 years) and 138 girls (14,3±3 years). The instruments used were a habitual physical activities questionnaire and a body silhouettes scale. Forty three per cent of girls and 29,4% of boys are insufficiently active. Sixty nine per cent of the boys and 76,7% of the girls are unsatisfied with their body silhouette. Boys demonstrate a tendency of both increase and decrease their body silhouette, while girls demonstrate a tendency to decrease their body silhouette. No association was found between satisfaction with body silhoutte and habitual physical activity status. To investigate the relationship between physical activity and body dissatisfaction can be useful for future research that could be verified in the therapeutical interventions with physical activity for the body dissatisfaction treatment.

Identificação de limiares metabólicos em curvas de freqüência cardíaca ajustadas

O objetivo deste estudo foi comparar os ajustes linear e sigmoide da frequencia cardiaca (FC) durante o exercicio incremental e analisar a validade destes modelos para identificar os limiares de transicao metabolica em exercicio progressivo, a partir de pontos de mudanca no ajuste nao-linear de Boltzmann. Dez mountain bikers de alto rendimento (27,1 ± 7,4 anos; 67,0 ± 6,1 kg; 175,1 ± 4,1 cm; 6,1 ± 1,9 % de gordura) foram submetidos a teste progressivo no ciclo-simulador, com carga inicial de 100 W e incremento de 30 W a cada 3 min ate a exaustao. A FC foi registrada batimento-a-batimento durante todo o teste. A curva da FC foi ajustada pela equacao sigmoide de Boltzmann, com calculo do Ponto de Inflexao da FC (PIFC = valor fixo V50 da equacao) e Ponto de Deflexao da FC (PDFC = metodo Dmax). No final de cada estagio, foi determinada a concentracao sanguinea de lactato ([La]). O primeiro limiar de lactato (LL1) foi determinado atraves do calculo do menor valor equivalente de lactato/carga. Para o segundo limiar (LL2), foi acrescido 1,5 mmol.l-1 ao menor valor deste equivalente. Em todos os atletas, o ajuste sigmoide da FC se apresentou mais adequado que o linear (p < 0,0001). O PIFC (161 ± 10 bpm) e PDFC (179 ± 5 bpm) foram identificados em oito e sete sujeitos, respectivamente. A FC e a carga do PIFC foram semelhantes as obtidas no LL2, enquanto que esses parâmetros foram menores no LL1 e maiores no PDFC. Assim, e possivel especular que o PIFC esta no mesmo dominio fisiologico do LL2. Entretanto, foram encontradas fracas associacoes entre os limiares de lactato com o PIFC e PDFC (-0,08 a 0,37).

High-CHO diet increases post-exercise oxygen consumption after a supramaximal exercise bout

We investigated if carbohydrate (CHO) availability could affect the excess post-exercise oxygen consumption (EPOC) after a single supramaximal exercise bout. Five physically active men cycled at 115% of peak oxygen uptake (V̇O2 peak) until exhaustion with low or high pre-exercise CHO availability. The endogenous CHO stores were manipulated by performing a glycogen-depletion exercise protocol 48 h before the trial, followed by 48 h consuming either a low- (10% CHO) or a high-CHO (80% CHO) diet regime. Compared to the low-CHO diet, the high-CHO diet increased time to exhaustion (3.0±0.6 min vs 4.4±0.6, respectively, P=0.01) and the total O2 consumption during the exercise (6.9±0.9 L and 11.3±2.1, respectively, P=0.01). This was accompanied by a higher EPOC magnitude (4.6±1.8 L vs 6.2±2.8, respectively, P=0.03) and a greater total O2 consumption throughout the session (exercise+recovery: 11.5±2.5 L vs 17.5±4.2, respectively, P=0.01). These results suggest that a single bout of supramaximal exercise performed with high CHO availability increases both exercise and post-exercise energy expenditure.

Relação entre indicadores fisiológicos obtidos em teste ergoespirométrico em cicloergômetro de membros superiores e desempenho na canoagem

A avaliacao de indicadores de aptidao aerobia em canoistas revela caracteristicas funcionais adquiridas por treinamento especifico, podendo estar relacionadas ao desempenho competitivo. Assim, o objetivo do presente estudo foi avaliar indicadores funcionais obtidos em teste ergoespirometrico de jovens canoistas, e verificar a relacao destas variaveis com a performance em distâncias de 200, 500 e 1.000m. Foram avaliados 12 atletas do sexo masculino (17,6 ± 2,1 anos; 175,7 ± 2,5cm; 68,3 ± 6,3kg) por meio de teste em cicloergometro de membros superiores para determinacao do consumo de oxigenio no limiar ventilatorio 1 (LV1 - 1,8 ± 0,4L/min), no limiar ventilatorio 2 (LV2 - 2,9 ± 0,4L/min) e VO2pico (3,5 ± 0,4L/min). O teste tinha inicio com carga de 17W, com incrementos de 17W/min ate a exaustao voluntaria. Os atletas foram tambem submetidos a testes especificos em embarcacao individual K-1 em um lago, objetivando alcancar os menores tempos nas distâncias referidas (tempos equivalentes a 47,6 ± 4,3, 122,0 ± 9,0 e 239,5 ± 12,6s, respectivamente). Foi utilizado o teste de correlacao de Spearman-Rank (rs), com nivel de significância fixado em 5%. Observou-se correlacao moderada entre LV2 e tempo nos 1.000m (rs = -0,685), VO2pico e tempo nos 500m (rs = -0,699) e VO2pico e tempo nos 1.000m (rs = -0,734). Portanto, conclui-se que LV2 e VO2pico obtidos em cicloergometro de membros superiores, e expressos em termos absolutos, predizem o desempenho em provas de 500 e 1.000m de canoagem, podendo ser potencialmente empregados na avaliacao de canoistas.

The effects of acute and chronic sprint-interval training on cytokine responses are independent of prior caffeine intake

We examined the effect of acute and chronic sprint interval training (SIT), with or without prior caffeine intake, on levels of exercise-induced inflammatory plasma cytokines [interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-α]. Twenty physically-active men ingested either a placebo (n = 10) or caffeine (n = 10) 1 h before each SIT session(13-s × 30-s sprint/15 s of rest) during six training sessions (2 weeks). The early (before, immediately after, and 45 min after the exercise) and late (24 and 48 h after the exercise) cytokine and creatine kinase (CK) responses were analyzed for the first and last training sessions. Plasma IL-6 and IL-10 peaked 45 min after the exercise, and then returned to basal values within 24 h (p < 0.05) in both groups on both occasions (p > 0.05). On both occasions, and for both groups, plasma TNF-α increased from rest to immediately after the exercise and then decreased at 45 min before reaching values at or below basal levels 48 h after the exercise (p < 0.05). Serum CK increased from rest to 24 and 48 h post-exercise in the first training session (p < 0.05), but did not alter in the last training session for the PLA group (p > 0.05). Serum CK was unchanged in both the first and last training sessions for the CAF group (p > 0.05). Two weeks of SIT induced a late decrease in the IL-6/IL-10 ratio (p < 0.05) regardless of caffeine intake, suggesting an improved overall inflammatory status after training. In conclusion, a single session of SIT induces muscle damage that seems to be mitigated by caffeine intake. Two weeks of SIT improves the late SIT-induced muscle damage and inflammatory status, which seems to be independent of caffeine intake.

Heart rate kinetics during very heavy and severe exercise performed after dietary manipulation

Little is known about heart rate (HR) kinetics during exercise in the very heavy (VH) and severe (SE) intensity domains. The objective of this study was to describe mathematically the HR kinetics during exercise performed in these intensity domains and to compare the parameters derived from these models between situations of high (HCHO), low (LCHO) and control (C) carbohydrate availability. Twelve men performed three trials to exhaustion in the VH or SE domains after diet manipulation with HCHO, LCHO and C. The VH intensity was ∆LW75% (75% of the difference between VO2max and LL2) and SE was 115% of VO2max identified in a previous incremental test (20 W/3 min). HR responses were mathematically fitted by mono- and biexponential functions. In the VH domain, the residual sum of squares (RSS) obtained with the biexponential model was significantly lower than that obtained with the monoexponential model (P 0.05). In the VH domain, there were no significant differences in biexponential parameters between the HCHO, LCHO and C conditions. In the SE domain, there were no significant differences in monoexponential parameters between the HCHO, LCHO and C conditions, although the time constant of the monoexponential model was significantly reduced in LCHO when compared to HCHO (51.5 ± 26.4 vs 65.4 ± 34.1 s; P < 0.05). The bi- and monoexponential mathematical models seem to be the best description of HR responses during exercise performed in the HV and SE intensity domains, respectively. In addition, carbohydrate availability only seems to affect HR kinetics during exercise performed at SE intensity.

Predição do desempenho aeróbio na canoagem a partir da aplicação de diferentes modelos matemáticos de velocidade crítica

O modelo de velocidade critica com dois parâmetros vem sendo utilizado para a determinacao do desempenho aerobio e anaerobio. No entanto, o modelo com tres parâmetros preve um parâmetro adicional correspondente a velocidade instantânea maxima (Vmax) ao modelo original, tendo impacto sobre a estimativa dos outros dois parâmetros. Sendo assim, o objetivo deste trabalho foi verificar e comparar a relacao da velocidade critica (VCrit), fornecida pelos modelos com dois (VCrit-2parâmetros) e tres (VCrit-3parâmetros) parâmetros, com a velocidade media mantida em esforco maximo de 6.000m (V6000m) na canoagem. Nove canoistas (17,4 ± 2,4 anos) competitivos do sexo masculino realizaram, em dias diferentes, testes maximos de 200, 500, 1.000, 1.800 e 6.000m. A VCrit foi calculada para todos os sujeitos, a partir das distâncias de 200 a 1.800m, utilizando-se as equacoes hiperbolicas com dois e tres parâmetros. As duracoes dos percursos ficaram no intervalo entre 46,1 ± 2,5s e 513,9 ± 25,6s. Para comparacao entre as velocidades (VCrit-2parâmetros, VCrit-3parâmetros e V6000m) foi utilizada ANOVA one way para medidas repetidas, seguida pelo teste post hoc de Newman-Keuls. A associacao entre as variaveis foi feita a partir de correlacao de Pearson. Para analise de concordância foi aplicada a plotagem de Bland-Altman entre os valores de VCrit-2parâmetros, VCrit-3parâmetros e V6000m . Em media, o tiro de 6.000m teve duracao de 29,9 ± 1,0 min. Houve diferenca significante da VCrit-3parâmetros (2,93 ± 0,36m/s) em relacao a VCrit-2parâmetros (3,31 ± 0,22m.s-1) e V6000m (3,35 ± 0,11m.s-1). VCrit-2parâmetros e V6000m nao diferiram entre si. A correlacao entre VCrit-2parâmetros e V6000m foi de 0,72 (p = 0,03), enquanto que a entre VCrit-3parâmetros e V6000m nao foi significante. Os resultados deste estudo sugerem que o modelo de velocidade critica de dois parâmetros fornece valor de VCrit mais adequado para a avaliacao aerobia de canoistas. A VCrit-3parâmetros subestima a velocidade que pode ser mantida por aproximadamente 30 min, com baixa capacidade preditiva de desempenho aerobio. Assim, foram obtidas evidencias de validade do modelo original de velocidade critica de dois parâmetros proposto por Monod e Scherrer.