Mechanisms for decreased exercise capacity after bed rest in normal middle-aged men
| Autor: | James H. McKillop, D. J. Goldwater, Robert F. DeBusk, Michael L. Goris, Victor A. Convertino, Joseph Hung |
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| Rok vydání: | 1983 |
| Předmět: |
Male
medicine.medical_specialty Erythrocytes Supine position Cardiac Volume medicine.medical_treatment Physical Exertion Posture Bed rest Oxygen Consumption Heart Rate Internal medicine Heart rate Humans Medicine Radionuclide Imaging Ejection fraction business.industry Oxygen transport Technetium VO2 max Heart Stroke Volume Stroke volume Middle Aged Radiocardiography Myocardial Contraction Echocardiography Exercise Test Cardiology Cardiology and Cardiovascular Medicine business Bed Rest |
| Zdroj: | The American Journal of Cardiology. 51:344-348 |
| ISSN: | 0002-9149 |
| DOI: | 10.1016/s0002-9149(83)80063-0 |
| Popis: | The mechanisms responsible for the decrease in exercise capacity after bed rest were assessed in 12 apparently healthy men aged 50 +/- 4 years who underwent equilibrium gated blood pool scintigraphy during supine and upright multistage bicycle ergometry before and after 10 days of bed rest. After bed rest, echocardiographically measured supine resting left ventricular end-diastolic volume decreased by 16% (p less than 0.05). Peak oxygen uptake during supine effort after bed rest was diminished by 6% (p = not significant [NS]), whereas peak oxygen uptake during upright effort declined by 15% (p less than 0.05). After bed rest, increases in heart rate were also greater during exercise in the upright than in the supine position (p less than 0.05). Values of left ventricular ejection fraction increased normally during both supine and upright effort after bed rest and were higher than corresponding values before bed rest (p less than 0.05). After bed rest, increased left ventricular ejection fraction and heart rate largely compensated for the reduced cardiac volume during supine effort, but these mechanisms were insufficient to maintain oxygen transport capacity at levels during upright effort before bed rest. These results indicate that orthostatically induced cardiac underfilling, not physical deconditioning or left ventricular dysfunction, is the major cause of reduced effort tolerance after 10 days of bed rest in normal middle-aged men. |
| Databáze: | OpenAIRE |
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