Murias, Juan M.Marinari, Gabriele2024-09-102024-09-102024-09-09Marinari, G. (2024). New approaches to investigate the oxygen cost of exercise applied to human performance (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.https://hdl.handle.net/1880/119662During exercise, there is a tight control between anaerobic and aerobic energy sources to meet the demand in adenosine triphosphate (ATP) for energy provision. Oxidative phosphorylation provides ATP via aerobic energy sources assuming an adequate supply of oxygen (O2) to the active tissues is provided. When the intensity of exercise is within the heavy domain (i.e., above the gas exchange threshold (GET)), there is an increased O2 cost per unit of work (i.e., V̇O2 gain; G) which has commonly been attributed to the development of the oxygen uptake slow component (V̇O2SC), in connection to a lower exercise efficiency. Therefore, finding new strategies to (i) decrease the O2 cost of exercise, (ii) explore the dynamics of V̇O2, and (iii) enhance exercise performance and improve cardiovascular fitness assessment is paramount in the field of exercise physiology. The general purpose of this thesis was to contribute to addressing the issues highlighted above. By implementing different exercise protocols, we found that: (i) approaching a target heavy-intensity constant-work rate (WR) gradually via a progressive ramp increment decreases steady state V̇O2 and reduces the initial and steady state lactate concentration ([La-]) as opposed to a standard step-transition to the same WR; (ii) increasing total hemoglobin concentration ([TotHb]) before reaching the target heavy-intensity WR via a ramp decreases muscle activation and the interaction (i.e., the ratio) between muscle activation and [TotHb] aligned with V̇O2, suggesting a tight link between the interplay of these physiological parameters; (iii) priming exercise accelerates the overall subsequent ramp incremental (RI) V̇O2 response by shortening the mean response time (MRT), extends the V̇O2max plateau and increases peak power output (POpeak). Collectively, these findings provide new insights into the mechanisms leading to the increased O2 cost of exercise, the interplay between muscle hemodynamics and muscle activation with V̇O2, and the beneficial effects of priming exercise on RI test to improve cardiovascular fitness assessment.enUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.Physiologydoctoral thesis