The primary aim of this thesis was to investigate the gender-specific responses to supramaximal cycling and to examine the changes in anaerobic and aerobic metabolism that occur in response to high-intensity interval training (HIT). All subjects in the present experiments were untrained, healthy young adults aged between 18 and 35 yr. Cycle ergometry was used for all experimental test procedures and training programs. The accumulated oxygen (AO2) deficit was used to quantify the production of adenosine triphosphate (ATP) via anaerobic metabolism during supramaximal cycling. In addition, pulmonary oxygen uptake measured at the onset of exercise was described using mathematical modeling to determine the rate response of the aerobic energy system during exercise. The purpose of experiment one was to examine the test-retest reliability of the maximal accumulated oxygen deficit (MAOD) measured at 110% and 120% of peak oxygen uptake for cycling in seven untrained male and seven untrained female subjects. After one familiarization trial, all subjects performed two MAOD tests at a power output corresponding to 110% and two tests at 120% of peak oxygen uptake in random order. MAOD was calculated for each subject as the difference between the estimated AO2 demand and the AO2 uptake measured during the exercise bout. The mean±standard error time to exhaustion (TE) for the group was not significantly different between trial one (226±13 s) and trial two (223±14 s) of the 110% test. Likewise, the difference in the TE between trial one (158±11 s) and trial two (159±10 s) was not significant for the 120% test. The intra-class correlation coefficients for the TE were 0.95 for the 110% test and 0.98 for the 120% test. The mean MAOD value obtained in trial one (2.62±0.17 L) was not significantly different from the mean value obtained in trial two (2.54±0.19 L) for the 110% test. Additionally, the mean values for the two trials did not differ significantly for MAOD (2.64±0.21 L for trial one and 2.63±0.19 L for trial two) in the 120% test. The intra-class correlation coefficients for MAOD were 0.95 for the 110% test and 0.97 for the 120% test. All intra-class correlation coefficients were significant at p < 0.001. When conducted under standardized conditions, the determination of MAOD for cycling was highly repeatable at both 110% and 120% of peak oxygen uptake in untrained male and female subjects. The results observed in experiment one suggest that the MAOD may be used to compare the anaerobic capacity (AC) of men and women and to examine changes in the contribution of the anaerobic energy systems before and after training. Experiment two examined the gender-specific differences in MAOD before and after 4 and 8 wk of HIT. Untrained men (n=7) and women (n=7) cycled at 120% of pre-training peak oxygen uptake to exhaustion (MAOD test) pre-, mid-, and post-training. A post-training timed test was also completed at the MAOD test power output, but this test was stopped at the TE achieved during the pre-training MAOD test. The 14.3±5.2% increase in MAOD observed in males after 4 wk of training was not different from the 14.0±3.0% increase seen in females (p > 0.05). MAOD increased by a further 6.6±1.9% in males and this change was not different from the additional 5.1±2.3% increase observed in females after the final 4 wk of training. Peak oxygen uptake measured during incremental cycling increased significantly (p < 0.01) in male but not in female subjects after 8 wk of training. Moreover, the AO2 uptake was higher in men during the post-training timed test compared to the pre-training MAOD test (p < 0.01). In contrast, the AO2 uptake was unchanged from pre- to post-training in female subjects. The increase in MAOD with training was not different between men and women suggesting an enhanced ability to produce ATP anaerobically in both groups. However, the increase in peak oxygen uptake and AO2 uptake obtained in male subjects following training indicates improved oxidative metabolism in men but not in women. It was concluded that there are basic gender differences that may predispose males and females to specific metabolic adaptations following an 8-wk period of HIT. Increases in AO2 uptake during supramaximal cycling demonstrated in men after training led to the hypothesis that peak oxygen uptake kinetics are speeded in male subjects with short-term HIT. It was suggested that training does not improve peak oxygen uptake kinetics in women as no change in AO2 uptake was found after 8 wk of HIT in female subjects. The purpose of experiment three was to examine peak oxygen uptake kinetics before and after 8 wk of HIT in six men and six women during cycling at 50% (50% test) and 110% (110% test) of pre-training peak oxygen uptake. A single-term exponential equation was used to model the peak oxygen uptake response (after phase I) during the 50% and 110% tests pre- and post-training. In addition, phase II and III of the peak oxygen uptake response during the 110% tests were examined using a two-term equation. The end of the phase I peak oxygen uptake response was identified visually and omitted from the modeling process. The duration of phase I determined during all experimental tests was not different between men and women and did not change with training in either group. Before training, men obtained a phase II peak oxygen uptake time constant (t2) of 29.0±3.3 s during the 50% test which was not different to the t2 of 28.8±2.2 s attained by women. In addition, the t2 determined during the 50% test was unchanged after 8 wk of HIT in both groups. The peak oxygen uptake kinetics examined during the 110% tests before training were well described by a single-term model in all male and female subjects. The t2 determined before training for the 110% test was significantly faster in men than in women. Furthermore, peak oxygen uptake was unchanged in female subjects and the t2 remained unaltered with 8 wk HIT (pre 45.5±2.2; post 44.8±2.3 s). In contrast, male subjects achieved a significantly higher peak oxygen uptake after training and the t2 determined for men during the 110% test was faster after training (36.4±1.6 s) than before training (40.1± 1.9 s). Improved model fits were obtained with the two-term equation compared to the single-term equation in two of the six male subjects during the 110% test post-training. It was found that the onset of the peak oxygen uptake slow component occurred at a mean time of 63.5±2.5 s and the t2 was reduced to 18.4±1.7 s. Using a Wilcoxon Signed Ranks z-test, the t2 described by the single-term equation in the remaining four subjects was determined to be significantly faster after training than before training, thus confirming the results obtained from the original group (n=6) of male subjects. End exercise heart rate (HREE) values obtained during the 50% and 110% tests were not different between men and women. During the 50% test, HREE values were unchanged, whereas HREE was significantly decreased during the 110% test after training in both groups. These data show that HIT might improve oxidative metabolism in men but not in women as reflected by a greater peak oxygen uptake and faster peak oxygen uptake kinetics during supramaximal work rates. We further suggest that the faster peak oxygen uptake kinetics demonstrated in men after training are probably not due to an improvement in cardiac function. Finally, the augmentation of oxidative metabolism during exercise after HIT in men might be dependent on the intensity of the exercise bout at which the peak oxygen uptake response is examined. The findings presented in this thesis suggest that MAOD is a reliable measure in both male and female subjects and can be used to monitor changes in anaerobic ATP production during supramaximal cycling. Moreover, these data suggest that 4 and 8 wk of HIT produce similar changes in anaerobic ATP generation in men and women. Finally, 8 wk of HIT results in the increase of peak oxygen uptake and AO2 uptake as well as the speeding of peak oxygen uptake kinetics during supramaximal cycling in male subjects. There was no evidence to suggest that oxidative metabolism was improved in women after short-term HIT. In conclusion, improvement in supramaximal exercise performances should be examined specifically for changes in the anaerobic and aerobic contributions to energy production. In addition, it is suggested that gender should be of primary consideration when designing exercise-training programs where improvement in both anaerobic and aerobic metabolism is required.

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Made available in DSpace on 2016-12-06T17:06:50Z (GMT). No. of bitstreams: 1 Jardel Schlickmann.pdf: 828069 bytes, checksum: 28142f1471dd5fe8cbc06d71583812dd (MD5) Previous issue date: 2012-04-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The purpose of this study was to determine whether supplementation with sodium bicarbonate (NaHCO3) changes in performance during supramaximal cycling exercise (ESupra), the cardiorespiratory variables and subsequent isometric muscle strength (IMS). The study include 8 male subjects, physically active (23,0±4,01years; 54,69±6,51ml/kg/min-1). The subjects underwent an all out ESupra at 1min in cycle ergometer with load 0,075 kg/weight, after ingestion of solution 0,3g/kg with NaHCO3 or placebo (PLAC) with 0,045g/kg NaCl. After performed the IMS for the upper and lower limbs. The NaHCO3 did not affect the ESupra (497,45±52,47W) compared with PLAC (497,97±60,15W). There were no effects of the ESupra or NaHCO3 ingestion of the test IMS for the elbow flexors (NaHCO3 pre 38,4±6,6kgf and post 36,7±7,8kgf; PLAC pre 37,1±6,8kgf and post 36,2±8,0kgf), as well as for IMS the knee extensors (NaHCO3 pre 84,68±12,36kgf and after 80,28±11,88kgf; PLAC pre 87,04±16,38kgf and after 81,20±13,41kgf). In relation the physiological responses was observed a significant increase at the end of the ESupra only to VCO2 (4,93±0,47l/min) in the condition NaHCO3 compared to PLAC (4,44±0,28l/min). No differences were observed for VO2, VE and VCO2 at anytime during recovery. Lactate concentrations were differently to blood condition NaHCO3 compared to PLAC from the second minute after the ESupra. Before these results, it is likely that the increase in blood lactate concentration after ingestions of NaHCO3 was due to increased release of lactate exercised by muscle and/or by decreasing the absorption in other tissues, since not presented evidence of increased production during exercise (i.e. improved performance). Moreover, the largest peak value during the VCO2 in ESupra suggest a lager buffering H+ generated by supplementation with NaHCO3. Despite evidence to demonstrate the action of NaHCO3 on acid-base balance and transport of lactate the administration of the alkaloid did not favor the performance of 1min ESupra or the IMS of the upper and lower limbs in active individuals. / O objetivo deste estudo foi verificar se a suplementação com bicarbonato de sódio (NaHCO3) altera o desempenho durante exercícios supramáximos no ciclismo (ESupra), as variáveis cardiorrespiratórias, e a força muscular isométrica subseqüente. Participaram deste estudo 8 sujeitos do sexo masculino, fisicamente ativos (23,0±4,01anos; 54,69±6,51ml/kg/min-1). Os voluntários foram submetidos a um ESupra de 1min no cicloergômetro, com carga 0,075 kg/peso, após a ingestão de uma solução com 0,3g/kg NaHCO3 ou placebo (PLAC) com 0,045g/kg de NaCl. Em seguida realizaram os testes de força máxima isométrica (FMI) para os membros superiores e inferiores. O NaHCO3 não teve efeito sobre o desempenho no ESupra (497,45±52,47W) comparado ao PLAC (497,97±60,15W). Não foram observados efeitos do ESupra nem da ingestão do NaHCO3 no teste para FMI dos flexores do cotovelo (NaHCO3 pré 38,4±6,6kgf e pós 36,7±7,8kgf; PLAC pré 37,1±6,8kgf e pós 36,2±8,0kgf), como também para a FMI dos extensores do joelho (NaHCO3 pré 84,68±12,36kgf e pós 80,28±11,88kgf; PLAC pré 87,04±16,38kgf e pós 81,20±13,41kgf). Em relação às respostas fisiológicas foi observado um aumento significativo durante o ESupra apenas para o pico de VCO2 (4,93±0,47l/min) na condição NaHCO3 comparado com o PLAC (4,44±0,28l/min), sem diferenças significativas para essa variável durante a recuperação. Não foram observadas diferenças significativas para o VO2 e VE em qualquer momento durante a recuperação. As concentrações de lactato sanguíneo foram diferentes para condição NaHCO3 quando comparado com o PLAC à partir do segundo minuto após o ESupra até o final dos 30min de recuperação. Diante dos resultados encontrados, é provável que o aumento na concentração do lactato sanguíneo após ingestão de NaHCO3 seja decorrente da maior liberação do íon pela musculatura exercitada e/ou pela diminuição da absorção nos outros tecidos, uma vez que não foram apresentados indícios de uma maior produção durante o exercício (i.e. melhora na performance). Além disso, o maior valor de VCO2 pico durante o ESupra sugere um maior tamponamento do H+ gerado pela suplementação com NaHCO3. Apesar de demonstrarmos indícios da ação do bicarbonato sobre o equilíbrio acidobásico e no transporte de lactato, a administração do alcalóide não favoreceu o ESupra de 1min no ciclismo nem a força máxima isométrica de membros superiores e inferiores em indivíduos ativos.