Position as a variable for cardiovascular responses during exercise

Abstract

Summary: Twenty-one normal young male subjects underwent resting and exercise (bicycle) radionuclide angiography in the full supine and 70" upright tilt positions in order to examine the effects of position on left ventricular size and performance, hemodynamics, and exercise duration. All subjects also underwent full (90") upright bicycle ergometry with respiratory gas analysis to establish the level of maximal exercise capacity for each. Body position significantly (p < 0.05) affected resting and exercise cardiovascular parameters. End-diastolic and endsystolic left ventricular volumes and stroke volume were larger in the supine position, both at rest and during exercise. The cardiac output at rest and during exercise were comparable for the two positions; an increase in resting and exercise heart rate in the 70" tilt position compensated for the reduced stroke volume of this posture. At maximal exercise, the 70" upright position was associated with a greater response in left ventricular ejection fraction, otherwise this parameter was not position related. Exercise capacity, in terms of duration and workload, was significantly higher in the supine (1 870 +390 s) and full upright (1830+250 s) positions than in the 70" tilt position (173Ok260 s). Changes in body position significantly alter parameters of ventricular, cardiovascular, and exercise performance.

Rest and exercise hemodynamic and metabolic findings in active duty soldiers referred for cardiac catheterization to exclude heart disease: Insights from past invasive cardiopulmonary exercise testing using multisensor high fidelity catheters

“…In the current study, at the work load = 50 watts, both heart rate and SVi increased with heart rate being the greater contributor to increased blood flow and stroke index more variable. These results are consistent with others reporting supine exercise in the catheterization laboratory (dye) and with other imaging modalities used in current practice to dynamically assess cardiac function .…”

“…In health, it is known that exercise capacity is influenced by subject age, gender, level of conditioning, hydration status, and environmental factors . The assessment of an individual's exercise capacity is also influenced by body position and exercise protocol . Although maximal aerobic capacity was not reported at the time of cardiac catheterization in our active duty soldiers, the variability in resting heart rate within the study population suggest that levels of aerobic conditioning varied and with a portion of the subjects (resting HR < 60 bpm) likely well‐conditioned at the time procedures were performed.…”

“…The physiological response to exercise depends on a subject's state of health, gender, level of conditioning, type, intensity and frequency of exercise, body position, state of hydration and environmental factors . This study provides insight into past practices of invasive cardiopulmonary testing and furthers the understanding of metabolic and hemodynamic changes in a young population during supine submaximal exercise.…”

Cardiopulmonary Responses at Various Angles of Cycle Backrest Inclination.

“…In general, the AT and peak VO2, which are determined from cardiopulmonary exercise testing, were lower in the supine position than in the upright position 5)8) . Left ventricular end diastolic pressure (LVEDP) and SV in the supine position were higher than those in the upright position at rest and during moderate exercise 12) . The difference in LVEDP and SV are gradually reduced as the work intensity increases 13) .…”

“…The CO and SV at the backrest angle of 60° was especially significantly greater, as compared with that at the 20° backrest angle. Cotsamire 12) and Thadani 13) reported that the CO and left ventricular end diastolic volume in supine exercise showed a significantly higher value than that in sitting exercise. Rowell 14) reported that the blood flow volume in the lung and the abdominal cavity increases more in the horizontal position than in the vertical position.…”