Preferred Name
Beverley Buchanan
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Date of Graduation
5-15-2025
Semester of Graduation
Spring
Degree Name
Master of Science (MS)
Department
Department of Kinesiology
First Advisor
Stephanie P. Kurti-Luden
Second Advisor
Nicholas D. Luden
Third Advisor
Michael J. Saunders
Abstract
Abstract
Purpose: The purpose of this study was to examine whether physiological sex-based differences affect cardiorespiratory responses to loaded and unloaded exercise in both normoxia and hypoxia, as well as exercise performance following loaded exercise under these conditions. Methods: Nineteen recreationally active males (n=8) and females (n=11) were recruited from James Madison University and the surrounding Harrisonburg area. Two preliminary tests included body composition assessment via DEXA, VO2max testing in normoxia and hypoxia, and familiarization with pulmonary functions tests. Experimental trials involved 45-minutes of treadmill walking at a matched relative intensity 65% VO2max in normoxia or hypoxia and in an unloaded or loaded state. Pulmonary function testing was performed through completion of the maximum flow volume loops (MFVL) and maximal inspiratory and expiratory pressure testing (MIPs/MEPs) before and after 45-minutes of treadmill walking. Breath samples were continuously collected through an automated gas exchange device (Vyntus One, Mettawa, Illinois, U.S.). Immediately after the 45-minutes of walking, subjects completed an unloaded time trial to exhaustion (TTE) trial at a matched relative intensity of 95% of their normoxic or hypoxic VO2max. Results: Females had lower FEV1 and FVC overall in the loaded conditions, (p< 0.05), effects which were not present in males. Both males and females experienced increased VE, VT, and fB in the loaded compared to unloaded conditions (p< 0.05). Specifically, females had higher fB in the loaded hypoxic condition compared to the unloaded hypoxic condition (p< 0.05). There were no changes in MIPs or MEPs from pre- to post- 45 minute treadmill walking (p>0.05). Lastly, females had lower TTE durations in hypoxia compared to normoxic conditions (p< 0.05), and muscle tissue TSI% (tissue saturation index) were lower in both hypoxic conditions compared to normoxia in females (p< 0.05). Conclusion: There were no changes in respiratory muscle fatigue pre- to post- 45-minute treadmill walking. Declines in hypoxic TTE duration in females may be better explained by lower muscle tissue TSI% during the TTE in hypoxia, which may reflect inadequate blood flow to fatiguing respiratory muscles respiratory leading to performance decrements. More research is needed to mechanistically explain the sex differences observed in the present study.
