Orientador: Antonio Carlos de Moraes / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Educação Fisica / Made available in DSpace on 2018-08-11T14:01:30Z (GMT). No. of bitstreams: 1 Altimari_LeandroRicardo_D.pdf: 2753845 bytes, checksum: 72487f2f03add9833dd0a2e582f711e2 (MD5) Previous issue date: 2008 / Resumo: O propósito do presente estudo foi investigar o efeitos da ingestão de cafeína (6 mg.kg-1) sobre o desempenho físico e mecanismos associados à fadiga de ciclistas em esforços supramáximos. Fizeram parte do estudo dez ciclistas com idade média de 27,5 ± 4,1 anos e tempo médio de prática na modalidade de 9,8 ± 4,7 anos. Os indivíduos foram submetidos a diferentes situações experimentais: 1) Determinação do consumo de oxigênio de pico (VO2pico) e limiar ventilatório (LV2); 2) Determinação da demanda acumulada de oxigênio (DEO2) (4 sessões de exercício submáximo - 60, 70, 80 e 90% do VO2pico), e 3) Teste retangular supramáximo (110% do VO2pico) para determinação do MAOD realizado em duas situações distintas (CAF - cafeína e PL - placebo/maltodextrina) aleatoriamente, em sistema duplo cego, com no mínimo 72 horas de intervalo entre os testes. Os sujeitos foram submetidos a mensuração de parâmetros antropométricos e anamnese nutricional para determinação do habito alimentar. Os sinais EMG foram coletados durante o teste retangular supramáximo (MAOD). O esforço percebido utilizando a escala de 6-20 pontos de Borg (1982) foi reportado a cada 30s de exercício no teste retangular supramáximo (MAOD). A concentração de lactato sangüíneo foi analisada em repouso (-60 min), imediatamente antes (0 min) e após (1, 3, 5, 7 e 10 min) o teste de MAOD nas condições CAF e PL. Os resultados demonstraram que o tempo de exaustão, a DEAO2 e o MAOD foram significantemente maiores na condição CAF comparada a PL (P<0,05). Não foram constatadas diferenças significantes na atividade EMG (RMS) dos músculos VL, VM, RF e QF integrados entre as condições CAF e PL em todos os períodos de tempo analisados (P>0,05). Quando comparado os slopes de FM dos músculos VL, VM, RF e QF integrados entre as condições CAF e PL estes se mostraram significantemente menores para ambos os músculos na condição CAF (P<0,05). O slope da PSE foi significantemente maior na condição CAF comparado a PL (P<0,05). Entretanto, o y-intercepto apresentou valor significantemente menor na condição CAF comparado a PL (P<0,05). Vale ressaltar que o valor de PSE inicial (30 s) medido durante o teste de MAOD na condição CAF foi significantemente menor comparado a PL (P <0,05). Não foram constatadas diferenças significantes nas concentrações de lactato sanguíneo entre as condições CAF e PL (P>0,05). Podemos concluir que a ingestão de cafeína (6 mg.kg-1) melhorou o desempenho anaeróbio pela atenuação da taxa de fadiga muscular causada por provável aumento na velocidade da condução dos impulsos nervosos para as fibras musculares / Abstract: The purpose of this study was to investigate the effects of the caffeine ingestion (6 mg.kg-1) on performance and mechanisms associated with the fatigue of cyclists in efforts supramaximum. Ten cyclists (age 27.5 ± 4.1 years; cycling experience 9.8 ± 4.7 years) were submitted to different experimental situations: 1) determination of the peak oxygen consumption (VO2pico) and ventilatory threshold (LV); 2) Determination of the accumulated oxygen demand (DEO2) (4 sessions of submaximum exercise - 60, 70, 80 and 90% of VO2pico), and 3) Supramaximum constant load test (110% of VO2pico) for determination of MAOD accomplished randomized in two different situations (CAF - caffeine and PL - placebo/maltodextrine), in double blind way, with an interval among tests with at least 72 hours. The subjects were submitted to anthropometric measurement and nutritional anamnesis for determination of the eating habits. The EMG signs were collected during the supramaximum constant load test (MAOD). The ratings of perceived exertion (PSE) were acquired using the 6-20 Borg scale (1982) being reported at each 30s of exercise during MAOD test. The blood lactate was analyzed in rest (-60 min), immediately before (0 min) and after (1, 3, 5, 7 and 10 min) during the MAOD test at CAF and PL conditions. The results demonstrated that the time of exhaustion, DEAO2 and MAOD were significantly larger in CAF than in PL condition (P < 0.05). Significant differences were not verified in the EMG activity (RMS) from Vastus Lateralis (VL), Vastus Medialis (VM), Rectus Femoris (RF) and integrated Quadriceps Femoris (QF) muscles among CAF and PL conditions during all of the analyzed periods (P > 0.05). When compared the mean power frequency (MPF) slopes of the muscles VL, VM, RF and QF integrated among the conditions CAF and PL these smaller significantly were shown for both muscles in the condition CAF (P < 0.05). The PSE slope was significantly higher during CAF when compare to PL condition (P < 0.05). However, the y-intercept presented significantly smaller value in CAF than in PL condition (P < 0.05). It is worthwhile to highlight that the initial value of PSE (30 s) measured during the MAOD test during CAF condition was significantly smaller than PL (P < 0.05). No significant differences were verified in the blood lactate concentrations between CAF and PL conditions (P > 0.05). It is possible to conclude that caffeine ingestion (6 mg.kg-1) improved anaerobic performance with the reduction of the rate of muscle fatigue, which could be explained by an increase in the firing rate of the neural impulse to muscles fibers / Doutorado / Ciencias do Desporto / Doutor em Educação Física

ABSTRACT Male subjects are invariably used to study the physiological determinants of middle distance running performance. Studies that do include females have examined only the aerobic contribution to middle distance running performance. The aim of the present study was to investigate aerobic, anaerobic and muscle function factors that could be used to predict middle distance running performance in female runners. This study was performed at an altitude of 1800m. Eleven middle distance female runners aged 18-20 were selected for the study. Aerobic capacity was assessed by measuring the maximal oxygen consumption (VO2max), running velocity at maximal oxygen consumption (vVO2max), running economy (RE) and onset of blood lactate accumulation (OBLA). The blood lactate curve of each subject was constructed by relating the oxygen consumption, to the plasma lactate concentrations. Anaerobic capacity was determined by measuring the maximum accumulated oxygen deficit (MAOD) on a treadmill. Muscle function was assessed by having the subjects cycle as fast as possible against changing brake weights ranging from heavy to light using a Monark cycle ergometer. The brake force (kg) was related to velocity (rpm).