The principal aim of this Master’s thesis was to investigate potential differences in physiological responses to maximal and submaximal exercise in normobaric hypoxia between trained and untrained girls. Hypoxia undoubtedly exerts a profound effect on an individual's exercise performance. However, it is not fully clear whether hypoxia-related reductions in exercise performance are greater in trained versus untrained women. As most of the studies on exercise have been carried out on man, data on women are scarce are lacking. The introduction summarizes the findings of previous research in this area before presenting the results and findings of a study that involved testing maximal oxygen uptake (VO2peak) in normoxia and normobaric hypoxia in trained and untrained women.
The study was conducted among 22 female volunteers, who were divided into two groups: trained and untrained, based on their baseline normoxic maximal oxygen uptake (VO2peak > or < 40 mL/kg/min, respectively). Each subject underwent two laboratory tests. At each visit, the subjects performed a graded exercise test until failure exhaustion and a submaximal constant load test (1,5 W/kg body mass) on a cycle ergometer, with simultaneous monitoring of selected cardiorespiratory parameters. The tests were administered randomly once under normoxia (310 m) and once under normobaric hypoxia (FiO₂ 12%, 4300 m altitude). The two laboratory visits were carried out approximately 28 days apart to ensure that the women were in tested within the same menstrual cycle phase.
The obtained results indicate that the VO2peak in hypoxia decreases significantly more in trained as compared to untrained women. Relative change in VO2peak, was 8,3 ± 4,2 for the trained and 2,3 ± 3,0 ml/kg/min for the untrained subjects. A greater decrease in systemic saturation associated with hypoxia was also observed in trained women (28,1 ± 4,5 % for trained and 22,9 6,5 % for untrained). Subjects who achieved higher VO2peak concomitantly also showed higher minute ventilation values. Hypoxia resulted an increase in the respiratory quotient in all subjects with no differences regarding the training status. The value in normoxia were 1,12 ± 0,04 and in hypoxia it increased to 1,24 ± 0,11. Submaximal exercise testing did not show consistent differences between trained and untrained subjects.
In line with previous findings, the present work confirms a significant influence of training status on physiological responses of women at altitude. The results also confirm the well-known fact that responses to hypoxia are highly individually variable. This Master's thesis allows for a better understanding of the physiological limitations and challenges that hypoxic exposure poses to both trained and untrained women.
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