Water movement in the body is determined by the osmotic forces acting on the cell membrane. Ingestion of a highly-hypertonic glycerol solution resulting in high extracellular osmolality could drive water out of the intracellular space into the vascular space resulting in reduced muscle hydration and increased blood volume. The aim of this thesis was to study the effects of altered body water distribution during exercise. In chapter 3, ingestion of a 400 ml glycerol solution (1 g·kg-1 body mass) increased serum osmolality (309 mosmol·kg-1) which was associated with a 4.0% increase in blood volume due to a 7.2% increase in plasma volume, attributed to a shift of water from the intracellular space, resulting presumably in tissue dehydration. Glycerol ingestion was then used as a means of altering body water distribution in the other studies described in this thesis. Altered body water distribution had no acute effect on force production during quadriceps muscle isometric exercise (chapter 4), or handgrip strength (chapter 5). Regarding chronic effects (chapter 5), two groups of participants exercised handgrip and initiated recovery after ingestion of either a glycerol solution or placebo over a period of 8 weeks. Maximum handgrip strength increased in both groups and there was no statistically significant difference between the two groups. In chapters 6 and 7, the subjects performed a cycling exercise protocol to fatigue. In the glycerol trial, time to fatigue decreased compared with the iso-osmotic trial during an incremental VO2max test (chapter 6) and during cycling against a constant load at 100% VO2max intensity (chapter 7). In the glycerol trial, there was an accelerated increase in blood lactate and an accelerated increase in serum potassium (chapter 7), indicating altered muscle metabolism which may have contributed to the early development of fatigue.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Objectives: To evaluate the survival analysis and the fracture resistance of weakened (W) and not weakened (NW) roots restored with different intracanal systems posts. Methods: Eighty teeth were sectioned in 16mm and prepared in 12mm with a custom drill. Fifty roots were weakened with a tapered diamond drill and 30 kept without weakening. The specimens were embedded with acrylic-resin in PVC cylinders until 3mm coronal (bone limit) and the periodontal ligament was simulated with polyether material. The experimental design was: G1 and G2: cast and post core (Golden Alloy) with (CPC-GL W) or without (CPC GL NW) weakened roots, respectively; G3 and G4: cast and post core (Ni-Cr alloy) with (CPC Ni W) or without (CPC Ni NW) weakened roots, respectively; G5 and G6: fiber-posts with (FP NW) or without (FP W) weakened roots; G7: fiber-posts especially designed for weakened roots (FP-E W); G8: fiber-posts relined with composite-resin for weakened roots (FP-CR). All posts were adhesively cemented. All of the restored specimens were submitted to the mechanical cycling (37ºC, 45º, 130N, 2.2Hz and 1.5 million pulses) and follow up intervals between cycles 5x104 evaluating the presence of the event "crack". The specimens that survived the mechanical cycling were subjected to the fracture-resistance test under load application on palatal zone at 45º-inclination (cross-head speed = 1 mm/min) until failure. Failure mode was classified in favorable (above the simulated bone limit) and catastrophic (below the simulated bone limit). Survival rates were estimated using the technique of Kaplan-Meier method and survival rates according to the study groups were analyzed using the log-rank test (p≤0.05). Fracture resistance data were analyzed by the one-way ANOVA and Tukey test (p=0.05). Results: The post-hoc comparisons showed differences between specimens in groups FP-E and CPC (p=0.004). For fracture resistance statistical differences (p<0.0001) were depicted among the weakened groups: CPC-GL 541.4227.4A, CPC-Ni 642.6219.5A, FP- 282.264.7B, FP-E- 274.151.3B, FP-RC- 216.663.6B. No differences were observed for groups without weakening: CPC-GL- 459.3111.1A, CPC-Ni- 422.0151.9A and FP- 347.991.8A, with majority of favorable failures. Conclusions: weakened roots restored with CPC promoted high values of fracture toughness and failure rates unfavorable. There was higher survival rate for FP-E in relation to CPC (GL / Ni). / Objetivos: Avaliar a sobrevida e a resistência à fratura de raízes fragilizadas e não fragilizadas restauradas com diferentes pinos intracanais. Métodos: oitenta incisivos bovinos foram seccionados em 16 mm e preparados em 12 mm com brocas padronizadas. 50 raízes foram fragilizadas com ponta diamantada mantendo 0,5 mm de espessura e 6 mm intra canal e 30 foram mantidas sem fragilização. Os espécimes foram embutidos em cilindros de PVC até 3 mm coronários (limite ósseo) e o ligamento periodontal foi simulado com poliéter. A divisão dos grupos foi: G1 e G2, núcleo metálico fundido (liga nobre) com (NMF-LN FRAG) e sem (NMF-LN NFRAG) fragilização, respectivamente; G3 e G4: núcleo metálico fundido (liga não nobre) com (NMF-LNN FRAG) e sem (NMF-LNN NFRAG) fragilização, respectivamente; G5 e G6: pino de fibra de vidro com (PFV FRAG) e sem (PFV NFRAG) fragilização, respectivamente; G7: pinos de fibra especiais para canais alargados (PFV-E FRAG) e G8: pinos de fibra re-embasados com resina composta (PA FRAG). Todos os pinos foram cimentados adesivamente. Os espécimes foram submetidos à ciclagem mecânica (37ºC, 45º, 130N, 2.2Hz e 1.5x106 ciclos) e acompanhados entre intervalos de 5x104 ciclos quanto à presença do evento trinca . Os espécimes que sobreviveram foram submetidos ao teste de resistência à fratura sob aplicação de carga na face palatina da coroa (45º e 1 mm/min) até a falha. O modo de falha foi classificado em favorável (acima do limite ósseo simulado) e desfavorável (abaixo do limite ósseo simulado). As taxas de sobrevida foram estimadas pela curva de Kaplan-Meier e as taxas de sobrevivência de acordo com os grupos de estudo foram analisadas através do teste log-rank (p≤0,05). Os dados de resistência à fratura foram analisados pelo teste de ANOVA 1 fator e Tukey (p=0,05). Resultados: para análise de sobrevida, 7 espécimes fraturaram durante a ciclagem mecânica (grupos FRAG: 2 fraturas para PFV, 1 para NMF-LN e 2 para PA, grupos NFRAG: 2 para PFV). As comparações post-hoc demonstraram diferença apenas entre os espécimes dos grupos PFV-E e NMF (p=0,004). Para resistência à fratura houve diferença estatística (p<0.0001) entre os grupos fragilizados: G1- 541,4227,4A, G3- 642,6219,5A, G5- 282,264,7B, G7- 274,151,3B, G8- 216,663,6B com predominância de falhas desfavoráveis. Conclusão: Observou-se maior taxa de sobrevida para PFV-E em relação aos NMF (LN/LNN). Quanto ao teste de resistência à fratura, as raízes fragilizadas restauradas com núcleos metálicos fundidos apresentaram pior comportamento em relação às raízes restauradas com pinos de fibra de vidro (PFV, PFV-E e PA).