Health, Exercise, and Sports Sciences ETDs

Publication Date

10-7-1976

Abstract

This study was designed to investigate the effects of acute altitude exposure on selected pulmonary, cardiovascular, and metabolic variables in men and women during submax and max work. Seventeen male and 20 female physical education students were randomly selected for inclusion in the investigation which took place over an 11-wk period. All testing was conducted in a hypobaric chamber with each subject being tested initially at the terrestrial altitude of 1576 m to which they were acclimated. Subsequent tests were conducted at simulated altitudes of 2743 m and 3962 m. The subjects pedalled a bicycle ergometer at a rate of 60 rpm and a power load of 90 kpm/min for the first 3 min after which the load was augmented by 90 kpm/min at the end of each minute until pedalling rate could no longer be maintained. When this point was reached, the test was terminated and a 10-min recovery period commenced. Heart rate, blood pressure, and breathing frequency were recorded the last 20 sec of each minute and 30-sec samples of expired air were collected periodically until exercise was terminated. During the recovery period, heart rate was recorded during submax and max exercise as well as recovery. Minute ventilation, breathing frequency, and oxygen pulse were calculated for submax and max exercise. Mean arterial blood pressure was recorded for submax exercise only. Oxygen consumption, respiratory exchange ratio, and ventilation equivalent for oxygen were calculated for max exercise only. Analysis of covariance with repeated measures was employed to test for differences between the sexes during submax and max exercise at the two simulated altitudes. Ventilation (BTPS) was the only variable during submax work to exhibit a consistent difference between males and females in that women had a lower ventilation than men at both 2743 m and 3962 m. The greater ability of women to protect the acid-base balance at altitude was advanced as a possible explanation for this difference. From 1576 m to 2743 m, the percentage changes in submax heart rate and oxygen pulse were found to be different between the sexes. A theory for this apparent advantage of women as compared to men to tolerate minor hypoxic stress was advanced. It was suggested that women, at lower elevations, have latent reserve in local muscle perfusion which is mobilized when hypoxia reaches sufficient levels for massive vasodilation. During max work, oxygen consumption was affected more by altitude in women than in men. This was explained by their inability to increase ventilation. Max ventilation which remained lower in women was attributed to disparities in physiological limits, acid-base balance, oxygen cost of ventilation, and aerobic capacities between the men and women in this study. The variance in aerobic capacity as well as in airway resistance was also thought to be responsible for the aforementioned differences in oxygen consumption and the altitude-sex interaction which was present for this variable. The difference in oxygen pulse was a manifestation of the observed changes in max oxygen pulse. It was concluded that, for the subjects in this study, females tolerated hypoxia better during submax work than did men. During maximal work, the men apparently had a better tolerance for hypoxia than did the women.

Document Type

Dissertation

Language

English

Degree Name

Physical Education, Sports and Exercise Science

Level of Degree

Doctoral

Department Name

Health, Exercise, and Sports Sciences

First Committee Member (Chair)

Hemming Axel Atterbom

Second Committee Member

Leon Everett Griffin

Third Committee Member

Vivian H. Heyward

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