Browsing by Author "Beever, Austin T"

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    The Effects of Simulated Altitude on Maximal and Submaximal Exercise
    (2021-04-26) Beever, Austin T; MacInnis, Martin J; Murias, Juan M; Aboodarda, Saied Jalal; Subudhi, Andrew W
    The maximal lactate steady state (MLSS) identifies the upper limit of sustainable exercise; however, the extent to which an individual’s MLSS is affected by changes in altitude is unknown. The primary objective of this thesis was to determine the extent to which the MLSS-associated cycling power output (PO) (MLSSp), assessed in normoxia (NORM; FIO2=20.9 %) at 1111 m in Calgary, AB, is affected by acute exposure to simulated hypoxia (HYPO; FIO2=18.2 %) and hyperoxia (HYPER; FIO2=23.8 %). The secondary objective was to evaluate metabolic, cardiorespiratory, perceptual and neuromuscular responses to 30 min of cycling at similar relative intensities (i.e., MLSSp, and 10 W above the MLSSp (MLSSp+10)), and the same absolute intensity of exercise (i.e., the normoxic MLSSp; MLSSpNORM) in these same FIO2 conditions. Eleven (4 females, 7 males) participants completed this study. MLSSp decreased in HYPO (209±54 W) compared to NORM (225±58 W; p=0.001), but HYPER (230±56 W; p<0.001) was not different from NORM (p>0.05). Four participants reached task failure prior to 30 min in the HYPO condition at MLSSpNORM, in addition to two, three and three participants in NORM, HYPO and HYPER, respectively, at MLSSp+10. At MLSSp and MLSSp+10 blood lactate concentration ([BLa]), ventilation (V?E), heart rate (HR) and perceptual responses to exercise did not differ between FIO2 conditions (p>0.05), despite a difference in V?O2 (p<0.05). In contrast, at MLSSpNORM, V?O2 was similar across conditions (p>0.05), whereas [BLa], V?E, HR and perceptual response to exercise were exacerbated in HYPO compared to both NORM and HYPER (p<0.05). Exercising in each condition elicited neuromuscular fatigue—manifesting as a reduction in quadriceps isometric maximal voluntary contraction, high- and low-frequency doublet, and single twitch force amplitudes—but no differences were detectable between conditions at any exercise intensity (p>0.05). In summary, a small decrease in FIO2, relative to ambient conditions, reduced the cycling MLSSp and exacerbated metabolic, cardiorespiratory and perceptual responses to ~30 min of exercise at an absolute PO but not at similar relative intensities, whereas increasing the FIO2 by the same amount did not significantly affect MLSSp or physiological responses to exercise performed at the same absolute or relative intensities.