Murias, Juan M.Iannetta, Danilo2019-09-032019-09-032019-08-28Iannetta, D. (2019). Identifying exercise intensity "thresholds": Implications for metabolic responses, performance, and exercise intensity prescription (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.http://hdl.handle.net/1880/110852The exercise intensity spectrum, from rest to maximal oxygen uptake (V̇O2max), can be partitioned into three domains of intensity: moderate, heavy, and severe. These domains are demarcated by the lactate threshold (LT) (moderate-to-heavy) and critical power (CP) or maximal lactate steady-state (MLSS) (heavy-to-severe), with the respiratory compensation point (RCP) of the ramp-incremental exercise also being proposed as a marker of the heavy-to-severe boundary of exercise intensity. Although the physiological concepts underpinning these thresholds are well established, methodological issues associated with their determination may lead to inaccuracies and contrasting interpretations regarding their equivalence. The general purpose of this thesis was to find solutions to some of the issues associated with the determination of these “thresholds” and demonstrate why their accurate determination is fundamental in exercise physiology. Using a variety of exercise protocols it was demonstrated that: i) current methods to compute the mean response time (MRT) of V̇O2 during ramp-exercise are inaccurate – the novel method proposed was valid and more reproducible than these methods; ii) exercising slightly above MLSS, although characterized in this study by a stable V̇O2 response, disproportionally impaired maximal exercise capacity; iii) if the V̇O2 dynamics during ramp-incremental exercise are carefully considered, the work rates at RCP and CP/MLSS are not different – refuting the idea that the RCP is not a valid surrogate of the heavy-to-severe boundary of exercise intensity; iv) current methods to prescribe exercise intensity based on fixed-percentage of maximum values (e.g., V̇O2max) do not provide an accurate procedure by which to control exercise intensity. Collectively, these findings provide solutions/explanations to some of the issues related to the correct identification of these exercise thresholds and suggest that their correct identification is of extreme importance when interpreting their physiological implications and to guarantee an accurate exercise intensity prescription.engUniversity 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.Oxygen uptake kineticsExercise prescriptionExercise physiologyPhysiologydoctoral thesis10.11575/PRISM/36930