Health, Exercise, and Sports Sciences ETDs

Publication Date

Winter 1-9-1978

Abstract

This investigation was conducted to evaluate effects of acute altitude exposure on selected pulmonary, cardiovascular, metabolic, and psychological variables measured at rest, during, and after submaximal exercise. Comparisons were made between a group of men with coronary heart disease who were participants in an exercise reha­bilitation program (trained CHD's) and a group of healthy, asymptomatic, and sedentary individuals (HI's).

Nine male trained CHD's and 10 male HI's partici­pated in the study, which was conducted during an 8-week period. Initially, all subjects performed a maximal stress test on a bicycle ergometer at 1576m. Maximal values from this test were utilized in determining rela­tive workloads for each subject. Subsequent tests were performed in a hypobaric chamber at 1576m and 3353m in randomly assigned sequence. Subjects pedaled a bicycle ergometer at a rate of 60 rpm and workload of 90 kpm/min for the first three minutes. Each minute thereafter, workload was increased 90 kpm/min until the end of test. The baseline tests terminated with attainment of maximal effort. Tests conducted in the hypobaric chamber were terminated at the predetermined 60-percent relative workload. A 5-minute recovery period followed, with blood pressure (BP) and heart rate (HR) being monitored the last 20 seconds of each minute. Before and during the test, HR and BP were taken the last 15 seconds of each minute and expired gas samples were collected every other minute, commencing the fourth minute and continuing until exercise was terminated. Oxygen consumption (V02) and minute ventilation (V) were calculated from expired air samples and heart rate (HR), mean blood pressure (BP), pressure rate product (PRP), pressure rate product/oxygen consumption (PRP/V02), oxygen pulse (OP), ventilation equivalent (VEQ), and perceived exertion (PE) were derived from data collected at rest, during, and after submaximal work.

Relative workloads during submaximal exercise were 30 percent, 40 percent, 50 percent, and 60 percent of maximal VO2. The Mann Whitney U-Test was utilized to assess differences between the two groups at each of these work levels, as well as at rest and recovery.

Change scores between 1576m and 3353m were utilized to delineate response differences between the two groups. The Wilcoxin Signed Ranks Test was used to test main effect of altitude on resting, submaximal work, and recovery variables within each group and work level.

A difference between trained CHD's and HI's was found in VEQ when altitude increased from 1576m and 3353m at 40 and 50 percent relative workloads. It is postulated that trained CHD's demonstrated a slightly decreased cardiac output response caused by a smaller stroke volume (SV). Consequently, as work progressed to 40 and 50 percent rela­tive workloads, cellular hypoxia and acidosis caused an increased ventilatory response. As exercise continued, the possibility of an increased peripheral vasodilation in trained CHD's could have resulted in decreased hypoxia. There also may have been an increased arterio-venous O2 difference (AVDO2) which could have caused a levelling off of Vat the 60-percent workload.

A difference between the two groups was also found in OP at the 60-percent workload when altitude was increased from 1576m to 3353m. A suggested theory for this differ­ence is that maximal SV was attained sooner in trained CHD's than in HI's. At the relative workload of 60 percent, higher HR and maximal SV were attained. At that workload, a reduced SV may have been the determining factor in the decreased SV by an increased AVDO2 as mentioned earlier. It was concluded that the trained CHD's in this study tolerated the metabolic consequences of altitude hypoxia as well as the HI's at rest, during, and after submaximal exercise at intensities up to and including 60 percent of maximal aerobic capacity.

Document Type

Dissertation

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

Vivian Heyward

Third Committee Member

Leon Everett Griffin

Fourth Committee Member

Richard D. Lueker

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