Identification of Individuals with Lower Versus Higher Exercising Limb Oxygen Delivery: Does Fatigue Progression Differ?
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Authors
Velickovic, Aleksandra
Date
Type
thesis
Language
eng
Keyword
Muscle Blood Flow , Oxygen Delivery/Demand Matching , Leg Exercise , Inter-Individual Differences , Fatigue
Alternative Title
Abstract
Background: In exercising skeletal muscle, oxygen delivery (O2Del) increases in proportion to oxygen cost (O2) to support aerobic production of the cell’s energy currency, ATP, and sustained exercise efforts. When O2Del/demand matching is acutely reduced within an individual, even if VO2 is maintained, greater fatigue occurs. Whether functionally significant differences in O2Del/demand matching exist between individuals, and whether these also impact fatigue, remains unknown. Purpose: 1. Identify inter-individual differences in exercising leg O2Del across a range of work rates (WR). 2. Determine whether those with relatively lower delivery exhibit increased fatigue progression. Methods: Ten healthy men completed multiple trials of progressive isometric knee extensor exercise (IKEE) to exhaustion to quantify individual O2Del/WR relationships. O2Del was determined as leg blood flow via ultrasound x arterial oxygen content (blood sampling). Higher and lower responder identification was based on O2Del/WR responses. A submaximal exercise fatigue test (SEFT) at 70% of peak, with intermittent maximal effort contractions, was used to track fatigue. Results: Higher versus lower O2Del/WR response individuals (p < 0.001) were identified and grouped accordingly. Differences in vasodilation accounted for O2Del/WR differences (p < 0.05). However, there was no between group difference in fatigue index (FI) (p = 0.43). This may have been because of the large variation in exercise efforts during the SEFT, confounding fatigue assessment. In a follow up study, it was determined if practice would improve repeatability and accuracy of exercise efforts to guide future study design. Participants performed 3 SEFTs on separate days. Initial MVC demonstrated good repeatability between trials (COV < 10%) but this did not improve with practice (p = 0.2). FI repeatability was problematic (COV > 10%), and did not improve with practice (p = 0.258). No significant interaction between the trial number and MVC interval on the average WR efforts (p = 0.673) suggests that the WR performed remained consistent within and between trials. Conclusion: In IKEE, there are inter-individual differences in O2Del/WR, which are attributable to differences in vasodilation. The SEFT did not detect any impact of O2Del/WR on fatigability, perhaps because of poor repeatability of FI, that was not improved with practice.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.