Orientador: Vilmar Baldissera / Resumo: Apesar de diversos avanços científicos, mesmo após mais de 200 anos de aplicação da primeira calorimetria com humanos e todas as possibilidades criadas pelas tecnologias desenvolvidas, em especial os aparatos portáteis, o gasto energético (GE) dos exercícios resistidos ainda permanece, de certa forma, elusivo. Desta forma, o presente estudo foi conduzido com o objetivo geral de Quantificar e criar um modelo matemático para a predição do gasto energético de homens e mulheres jovens fisicamente ativos nos exercícios supino reto (SR) e leg press (LP). 11 homens (grupo masculino – GM), com idade (média ± desvio padrão) de 28,7 ± 5,5 anos, altura de 1,77 ± 0,07m, massa corporal de 81,40 ± 8,17kg e percentual de gordura de 16,36 ± 6,79% e 11 mulheres (grupo feminino – GF), com idade de 27,6 ± 4,6 anos, altura de 1,67 ± 0,06m, massa corporal de 60,05 ± 5,76kg e percentual de gordura de 20,20 ± 2,73% se voluntariaram para o estudo. Cada voluntário se apresentou ao Laboratório de Fisiologia do Exercício da UFSCar em oito ocasiões: na primeira visita, os voluntários foram informados sobre os objetivos e procedimentos do estudo, assinaram o termo de consentimento livre e esclarecido, os dados antropométricos mensurados e realizado o ajuste da biomecânica dos exercícios e teste de 1 repetição máxima (1RM) nos exercícios SR e LP. Após 48 a 72 horas, na segunda visita, os voluntários foram submetidos ao reteste de 1RM. Nas seis visitas seguintes, os voluntários foram submetidos ao protocol... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Despite many scientific advances, even after over 200 years of the first calorimetry on humans and all the possibilities made especially by portable apparatus, energy expenditure (EE) still remains somehow elusive. In this sense, the present study was conducted to quantify and create a model to predict EE of young physically active men and women on the bench press (BP) and leg press (LP) exercises. 11 men (male group – GM) with age (mean ± standard deviation) 27.8 ± 5.5 years, height 1.77 ± 0.07m, body mass 81.40 ± 8.17kg and body fat percentage of 16.36 ± 6.79% and 11 women (female group – GF) with age 27.6 ± 4.6 years, height 1.67 ± 0.06m, body mass 60.05 ± 5.76kg and body fat percentage of 20.20 ± 2.73% volunteered for the study. Volunteers came to the Exercise Physiology Laboratory of UFSCar on eight visits: in the first visit, volunteers were informed of the aims and proceedings of the study, signed an informed consent and had their anthropometric data analyzed, biomechanical adjustments made and perform 1 repetition maximum (1RM) test on both exercises. After 48 to 72 hours, volunteers came to the second visit to perform 1RM re-test. In the six following visits, volunteers were submitted to the EE protocol at 40, 60 or 80% of their 1RM on the BP and LP exercises. Interval for evaluations of the same exercise were 48 to 72 hours. GM had a significant difference in total energy expenditure between exercises, but such effect was not observed when EE was quantified as calor... (Complete abstract click electronic access below) / Doutor

The aims of this thesis were to: 1) develop a new method for the determination of interstitial pH at rest and during exercise in vivo, 2) systematically explore the effects of different ingestion regimes of 300 mg.kg-1 sodium citrate on blood and urine pH at rest, and 3) to combine the new interstitial pH technique with the findings of the second investigation in an attempt to provide a greater understanding of H+ movement between the extracellular compartments. The purpose of the first study was to develop a method for the continuous measurement of interstitial pH in vastus lateralis was successfully developed using microdialysis and 2,7-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF). To avoid the presence of an artificial alkalosis during exercise, it was necessary to add 25 mM HCO3- to the perfusate. The outlet of the probe was cut less than 10 mm from the skin and connected to a stainless steel tube completing the circuit to a microflow-through cuvette (8 fÝl) within a fluorescence spectrophotometer. This prevented the loss of carbon dioxide from the dialysate and any subsequent pH artefact. Interstitial pH was collected from six subjects before, during and after five minutes of knee-extensor exercise at three intensities 30, 50, and 70 W. Mean,,bSEM interstitial pH at rest was 7.38,,b0.02. Exercise reduced interstitial pH in an almost linear fashion. The nadir value for interstitial pH at 30, 50 and 70 W exercise was 7.27, 7.16 and 7.04, respectively. The lowest pH was obtained 1 min after exercise, irrespective of workload, after which the interstitial pH recovered in a nearly exponential manner. The mean half time of interstitial recovery was 5.2 min. The changes in interstitial pH exceeded the changes in venous blood pH. This study demonstrated that interstitial pH can be measured using microdialysis and that it is continuously decreased during muscle activity. The purpose of the second study was to establish an optimal ingestion regime for the ingestion of 300 mg.kg-1 of sodium citrate and maximise the alkalotic effect while minimising any side effects. Increasing the effectiveness of alkali ingestion may lead to further increases in muscle performance. Ingesting 300 mg.kg-1 sodium citrate at a rate of 300 mg.min-1 was identified as the optimal ingestion regime to maximise alkalosis at rest, which occurred 3.5 h post-ingestion. This was determined by monitoring eight human subjects ingesting 300 mg.kg-1 sodium citrate at five different rates, control (no ingestant), bolus, 300, 600 and 900 mg.kg.min-1 on five days separated by at least 48 hours. Sodium citrate was ingested in capsule form with water ad libitum, with the exception of bolus, which was combined with 400 ml less than 25 percent orange juice and consumed in less than 1 min. Arterialised blood (mean 71.3,,b3.5 mmHg) acid-base and electrolyte status was assessed via the withdrawal of ~5 ml of blood every 30 min across an eight hour duration, placed on ice and analysed within five minutes. No alkalotic difference was found between ingestion rates (mean 7.445,,b0.004, 7.438,,b0.004 and 7.442,,b0.004 for 300, 600 and 900 mg.min-1, respectively). All experimental ingestion regimes were associated with elevations in [HCO3-] (29.6, 29.7, 29.8, 29.9 and 26.3 mmol.l-1 for bolus, 300, 600, 900 and control, respectively). The 300 ingestion regime had the greatest impact on [H+], a 0.66 meq.l-1,,e10-8 change. Bolus ingestion (3.93,,b0.08 mmol.l-1) of sodium citrate had no effect on control (4.06,,b0.08 mmol.l-1) blood [K+], however, 300 mg.min-1 decreased blood [K+] (p less than 0.05). There was no effect of sodium citrate on blood [Cl-], but after 2.5 h blood [Cl-] was lower than pre-ingestion values (p less than0.05). All ingestion rates of sodium citrate increased (p less than 0.05) urine pH above control. This is the first study to investigate the effect of varying ingestion rates on acid-base status at rest in humans. The results suggest that ingesting sodium citrate in small doses in quick succession induce a greater blood alkalosis than the commonly practised bolus protocol. Using the interstitial pH technique described above and the optimal ingestion regime (300 mg.min-1) identified above, the final experiment was designed to assess the influence of sodium citrate ingestion on interstitial pH at both rest and during exercise. Five subjects ingested 300 mg.kg-1 sodium citrate at 300 mg.min-1 again in capsule form with water ad libitum. Prior to ingestion, each subject had a cannula placed into their cephalic vein and one microdialysis probe (CMA-60) inserted into their left thigh, orientated along the fibres of vastus lateralus. This probe was used for the measurement of pH as described above. At the end of this period, an exercise protocol required five subjects to perform light exercise (10 W) for 10 min, before starting an intense exercise period (~90-95% leg VO2peak) to exhaustion followed by a 15 min recovery period. Dialysate and blood samples were collected across all periods. Mean,,bSEM interstitial pH for placebo and alkalosis were 7.38,,b0.12 and 7.24,,b0.16, respectively. Sodium citrate ingestion was not associated with an interstitial alkalosis. An exercise induced acidosis was observed in the interstitium during placebo but not during alkalosis (p less than 0.05). Mean,,bSEM venous pH were 7.362,,b0.003 and 7.398,,b0.003 for placebo and alkalosis, respectively. Sodium citrate ingestion was not associated with a venous alkalosis. Sodium citrate ingestion was associated with an increase in mean,,bSEM venous [HCO3-] (placebo 25.5,,b0.2, alkalosis 28.1,,b0.2). This increase in the blood bicarbonate buffer system was not associated with an increase in time to exhaustion (placebo 352,,b71, alkalosis 415,,b171). This was the first study to investigate the effects of sodium citrate ingestion on interstitial pH. The results of this study demonstrated that an interstitial alkalosis does not ensue after alkali ingestion, however, it was associated with the lack of an exercise induced acidosis suggesting an improved pH regulation during exercise.