The process of fatigue during 30 s of high-intensity exercise results in rapid and substantial mechanical, electrical and biochemical changes in muscle fibres. This thesis describes a series of experiments, performed upon a friction-loaded cycle ergometer, which investigated whether the magnitude of the mechanical and biochemical changes is affected by changes in average pedalling rate. The ability to generate peak power in a subsequent sprint of 6 s duration was used to assess the magnitude of the mechanical changes. Changes in the concentrations of blood and muscle metabolites pre- and post-exercise permitted some of the biochemical changes to be measured.

The purpose of this investigation was to determine the effects of a four day creatine load and simultaneous energy restriction on muscle creatine content, exercise performance, and body composition in 24 male recreational resistance trainers, age 18-26. Sixteen subjects were randomly divided into placebo (Pl, n=8) and creatine supplement (CrS, n=8) groups. Control (C, n=8) subjects of the same age were recruited separately g à d-1 to complete the performance and body composition tests while consuming their normal diet. The CrS group was administered 20 g à d-1 of creatine monohydrate (Cr) mixed with 5 g à d-1 of sucrose, while the Pl group was administered 25 of sucrose. Both CrS and Pl consumed a formula diet of 75.3 kJ (18 kcal) à kg-1 à d-1 for 4 d. Testing before and after energy restriction consisted of a repeated sprint cycle performance test (10 sprints of 6s, with 30s rest), hydrostatic weighing, and resting needle muscle biopsy. Testing revealed that subjects in CrS and Pl demonstrated significant decreases in body weight and % body fat (%BF) with no difference between groups. However, Pl demonstrated a significantly greater % loss in FFM (2.4 ± 0.25%) compared to CrS (1.4 ± 0.4%) (p<0.05). The muscle fuel stores of CrS and Pl responded significantly to the diet. Significant increases in muscle total Cr (p<0.01), free Cr (p<0.01), and CrP (p<0.05) of 16.5%, 16.8%, and 16% respectively were demonstrated by CrS over the energy restriction period, while Pl demonstrated significant decreases of 7.2% and 8.2% respectively in muscle total Cr (p<0.01) and free Cr (p<0.05). There were no significant differences between groups for performance during the cycle test, however, there were trends toward group by time interactions for performance enhancement in CrS relative to Pl, as total work (p=0.078) and work capacity (p=0.058) increased 3.8 ± 2.2% in CrS and decreased 0.5 ± 0.4% in Pl. It was concluded that short-term energy restriction resulted in decreased muscle Cr storage, and that Cr supplementation during energy restriction increased muscle Cr and CrP stores. Consumption of Cr allowed CrS to lose a significantly lower % FFM compared to Pl. Cr supplementation resulted in trends toward improved performance in CrS relative to Pl after energy restriction, but did not influence losses in body weight or %BF. / Master of Science

Made available in DSpace on 2016-12-06T17:07:00Z (GMT). No. of bitstreams: 1 Rogerio Santos de Oliveira Cruz.pdf: 891626 bytes, checksum: 8f132132abe4c34477a9871250e9fdb6 (MD5) Previous issue date: 2014-06-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A group of recreationally trained cyclists (26 ± 5 years, 176 ± 5 cm, 78 ± 8 kg, n = 15) took part in this repeated measures design, which aimed to evaluate the effects of remote ischemic preconditioning (RIPC) on physiological, metabolic and performance variables during the 1-min cycling time-trial. The subjects attended to the Human Performance Research Laboratory on six separate occasions within a two week period, with at least 48 h separating each test session. After an incremental test and a familiarization visit (sessions 1 and 2), subjects were randomly submitted in sessions 3 and 4 to a performance protocol preceded by either intermittent bilateral cuff inflation to 220 mm Hg (i.e., RIPC) or to 20 mm Hg (i.e., control). To increase data reliability, each intervention was replicated in visits 5 and 6, also in a random manner. In addition to cycling performance (mean power), the pulmonary oxygen uptake (VO2) and blood lactate responses were analyzed during the 1-min time trial and throughout 45-min of passive recovery to estimate the absolute and relative energy contribution from the three energy systems, as well as the total energy provision during performance. There was a substantial enhancement in performance after RIPC (1.9%, 90%CL of ±0.8%, n = 14), which was accompanied by improvements in the anaerobic glycolytic metabolism, even though it was insufficient to account alone for the observed change in performance. Our calculations therefore suggest that about 65% of the improvement after RIPC could be associated to an unnoticed higher lactic ATP turnover in the active muscles, while a supposed ATP sparing effect would be responsible for the remaining 35%. / Um grupo de ciclistas recreacionais treinados (26 ± 5 anos, 176 ± 5 cm, 78 ± 8 kg, n = 15) participou deste delineamento de medidas repetidas, o qual teve como objetivo principal avaliar os efeitos do pré-condicionamento isquêmico remoto (RIPC) sobre variáveis fisiológicas, metabólicas e de desempenho durante o teste de 1-min contra-o-relógio (1-min CR) no ciclismo. Os sujeitos compareceram ao Laboratório de Pesquisas em Desempenho Humano da UDESC em seis ocasiões distintas dentro de um período de duas semanas, com intervalos mínimos de 48 h entre cada sessão. Após um teste incremental e uma visita de familiarização com o teste de 1-min CR (visitas 1 e 2), os ciclistas foram submetidos randomicamente a um protocolo precedido ou não por restrição intermitente de fluxo sanguíneo (visitas 3 e 4). Para aumentar a confiabilidade dos dados, cada intervenção (RIPC ou controle) foi replicada nas visitas 5 e 6, também de maneira aleatória. Além do desempenho (potência média gerada), foram analisadas as respostas do consumo de oxigênio a nível pulmonar (VO2) durante o desempenho e ao longo dos 45-min de recuperação, juntamente com o comportamento da concentração de lactato no sangue arterializado. A partir destas variáveis, foram estimadas a contribuição relativa e absoluta dos três sistemas energéticos e a quantidade total de energia fornecida pelo organismo durante o desempenho. Houve uma melhora substancial no desempenho após a aplicação do RIPC (1,9%, LC90% de ±0,8%, n = 14), acompanhada por prováveis aprimoramentos nas variáveis associadas ao metabolismo glicolítico. Nossos cálculos sugerem que aproximadamente 65% da melhora no rendimento pode ser atribuída à maior capacidade muscular de ressíntese lática de ATP, enquanto uma suposta economia de ATP seria responsável pelos 35% restantes.